Title:
SYSTEM FOR PRODUCING AND DISCHARGING OXIDIZERS FOR WASHING OPERATIONS
Document Type and Number:
United States Patent 3682190
Abstract:
The invention disclosed is directed to a system for generating and discharging oxidizers such as sodium hypochlorite in washing operations where maintenance of a predetermined concentration of oxidizer for extended periods on a continuous and automated basis is essential for stain removal and disinfection. The oxidizer production is achieved by controlled electrolysis of suitable salts in a vessel separate from that in which the objects are washed. The supply of oxidizer to the wash solution is accomplished by a regulated overflow system.
Inventors:
Patil, Arvind S. (Silver Spring, MD)
Veltman, Preston L. (Severna Park, MD)
Loder, Edwin R. (Cincinnati, OH)
Sabatelli, Philip M. (Cincinnati, OH)
Sarge, Carmen R. (Fort Thomas, KY)
Veltman, Preston L. (Severna Park, MD)
Loder, Edwin R. (Cincinnati, OH)
Sabatelli, Philip M. (Cincinnati, OH)
Sarge, Carmen R. (Fort Thomas, KY)
Plaque It!
Sponsored by: Flash of Genius |
Application Number:
05/046941
Publication Date:
08/08/1972
Filing Date:
06/17/1970
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Export Citation:
Primary Class:
Other Classes:
204/275.100, 134/57R
International Classes:
A47L15/44; C02F1/467; C11D3/395; C11D11/00; C02F1/461; B08B3/00
Field of Search:
134/57D,57R,100 137/5,93 204/95,149,151,152,275
US Patent References:
| 2663308 | Unitary solution control apparatus | December 1953 | Hodgens | |
| 2859760 | Automatic detergent feeding control | November 1958 | Borell | |
| 2887444 | Process of and means for chlorinating swimming pools or the like | May 1959 | Lindstaedt | |
| 3139890 | Dishwasher having means to inject liquid additive into the rinse water supply line | July 1964 | Moran | |
| 3274094 | Apparatus for the chlorination of water | September 1966 | Klein | |
| 3343045 | Solution conductivity measuring and controlling apparatus | September 1967 | Law et al. | |
| 3378479 | Electrolytic cell and chlorinating system using same | April 1968 | Colvin et al. | |
| 3433723 | METHOD FOR PRODUCING HYPOCHLORITE SOLUTIONS AND INTRODUCING SAME INTO CONFINED BODIES OF WATER | March 1969 | Stanton | |
| 3518174 | METHOD AND APPARATUS FOR PURIFICATION OF WATER CONTAINING ORGANIC CONTAMINANTS | June 1970 | Inoue |
Primary Examiner:
Cohan, Alan
Assistant Examiner:
Zobkiw, David J.
Claims:
WHAT IS CLAIMED IS
1. A washing system which comprises in combination, a wash tank containing a wash solution, an oxidizer reservoir disposed outside the wash tank and in an overhead position relative thereto, said oxidizer reservoir containing means for generating oxidizer including an electrochemical cell and a solution of a salt selected from the group consisting of alkali metal and alkaline earth metal salts of chlorine, bromine and iodine, said electrochemical cell having an anode and two cathodes, said cathodes being shorter than said anode and disposed on each side of the anode substantially parallel to one another, a housing for the cell having a central long rectangular compartment for the anode, and two side compartments, one on each side of the anode compartment for each cathode, each compartment open at the bottom and having a vent on top for the escape of anodic and cathodic gases, a side drain extending from the oxidizer reservoir and into the wash tank for initial transfer of oxidizer generated by said electrochemical cell in the oxidizer reservoir and into the wash tank, water feed means for controllably supplying water to the oxidizer reservoir, and an overflow outlet from the oxidizer reservoir to the wash tank for supplying oxidizer generated by said electrochemical cell in the oxidizer reservoir to the wash tank.
2. The washing system of claim 1 wherein said salt is selected from the group consisting of sodium chloride, and potassium chloride and wherein the concentration of said salt in said solution is within the range of from about 1. percent by weight to about the percent by weight at which the solution is saturated.
3. The washing system of claim 1 wherein the overflow outlet is controlled by a solenoid valve which is actuated by a conductivity cell whenever the conductivity of the wash solution falls below a predetermined value for maintaining a predetermined concentration of oxidizer in the wash solution.
4. The washing system of claim 1 wherein the concentration of the oxidizer is from about 20 to about 40 parts per million of chlorine in the wash solution.
5. The washing system of claim 1 wherein the concentration of the oxidizer is from about 1 to about 10 parts per million of iodine in the wash solution.
1. A washing system which comprises in combination, a wash tank containing a wash solution, an oxidizer reservoir disposed outside the wash tank and in an overhead position relative thereto, said oxidizer reservoir containing means for generating oxidizer including an electrochemical cell and a solution of a salt selected from the group consisting of alkali metal and alkaline earth metal salts of chlorine, bromine and iodine, said electrochemical cell having an anode and two cathodes, said cathodes being shorter than said anode and disposed on each side of the anode substantially parallel to one another, a housing for the cell having a central long rectangular compartment for the anode, and two side compartments, one on each side of the anode compartment for each cathode, each compartment open at the bottom and having a vent on top for the escape of anodic and cathodic gases, a side drain extending from the oxidizer reservoir and into the wash tank for initial transfer of oxidizer generated by said electrochemical cell in the oxidizer reservoir and into the wash tank, water feed means for controllably supplying water to the oxidizer reservoir, and an overflow outlet from the oxidizer reservoir to the wash tank for supplying oxidizer generated by said electrochemical cell in the oxidizer reservoir to the wash tank.
2. The washing system of claim 1 wherein said salt is selected from the group consisting of sodium chloride, and potassium chloride and wherein the concentration of said salt in said solution is within the range of from about 1. percent by weight to about the percent by weight at which the solution is saturated.
3. The washing system of claim 1 wherein the overflow outlet is controlled by a solenoid valve which is actuated by a conductivity cell whenever the conductivity of the wash solution falls below a predetermined value for maintaining a predetermined concentration of oxidizer in the wash solution.
4. The washing system of claim 1 wherein the concentration of the oxidizer is from about 20 to about 40 parts per million of chlorine in the wash solution.
5. The washing system of claim 1 wherein the concentration of the oxidizer is from about 1 to about 10 parts per million of iodine in the wash solution.
Description:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a system for producing and discharging oxidizers such as sodium hypochlorite in washing operations. The oxidizer is produced by electrolysis of dissolved salts in required concentration and at a required rate to maintain a predetermined concentration of oxidizer in the wash solution. The oxidizer is discharged into the wash solution by utilization of an overflow system which can be either manually or electronically controlled. The present invention is particularly valuable where production and maintenance of oxidizers in a washing system is required on a continuous and automated basis.
2. Description of the Prior Art
Oxidizing agents are used extensively in various types of washing operations for such purposes as disinfecting, deodorizing and bleaching. The use of oxidizing agents such as chlorine and hypochlorites in washing operations, particularly institutional and commercial laundry and dishwashing systems is highly desirable because of the rapid washing processes utilized by institutions.
The hypochlorites, which are used extensively for increased detergency and stain removal in laundry and dishwashing systems are ordinarily produced by reacting gaseous chlorine with a hydroxide of sodium, calcium or potassium under carefully controlled conditions. Gaseous chlorine is readily obtainable by simple electrolysis of an aqueous solution of the corresponding chloride salt. The electrochemical generation of chlorine is widely practiced, and such processes are well developed in the art. However, there are many hazards and problems connected with supplying washing operations with active chlorine gas as well as hypochlorites.
Many conventional methods for the addition of chlorine and chlorine releasing compounds to wash solutions are based upon the chemical action of chlorine. While the direct introduction of gaseous chlorine from a pressurized source probably represents the simplest form of disinfecting and destaining this method has the disadvantages of requiring heavy and cumbersome pressure type storage cylinders to contain the supply of liquid or gaseous chlorine, and an expensive and delicately balanced metering system for regulating the delivery of the gas.
The use of granular solid-type oxidizers such as hypochlorite preparations are quite costly and very difficult to distribute uniformly throughout the wash solution. Ready mixed hypochlorites share a disadvantage with the solid hypochlorite preparations in being an expensive source of chlorine. Difficulties are also encountered in the storage, transportation, and fire prevention of ready mixed oxidizers such as hypochlorites.
The use of detergents containing chlorine releasing agents also presents a threat to the efficiency of washing systems. Many dish and laundry detergents containing both a chlorine releasing agent and a surfactant have brief shelf lives due to attack by chlorine on the surfactant. As a result, the overall effectiveness of the composition is reduced.
While previous attempts have been made to produce and supply washing systems with various oxidizers, especially chlorine gas and hypochlorites, these attempts have not been successful in developing a safe, efficient and inexpensive method for both generating oxidizers and discharging them in a regulated manner into washing systems in order to maintain a predetermined level of oxidizer in the wash solution.
SUMMARY OF THE INVENTION
It has now been found by the practice of this invention that a predetermined level of oxidizer can be maintained in a wash solution by utilization of a washing system which comprises a means for producing the oxidizer, and discharging it into the wash solution. The oxidizer is produced in a separate chamber from that in which the articles are washed. An electrochemical cell consisting of a set of electrodes may be incorporated into this chamber (hereafter referred to as the salt reservoir), or in a separate chamber. The electrodes are continuously exposed to a salt solution such as a sodium or potassium chloride, iodide or bromide singly or in combintion. A dropspout attached to an overflow outlet in the side wall of the oxidizer reservoir, a chamber in which the oxidizer is produced and/or stored, extends into the washing apparatus and discharges the oxidizer from said chamber to the wash solution. The amount of oxidizer discharge supplied to the wash solution can be controlled by a simple regulated overflow, or a sophisticated electronic control utilizing conductivity and/or the oxidation-reduction potential of the solution in the washing operation.
The present system of electrochemically generating an oxidizer such as chlorine and discharging it into a washing system can be adapted to various types of washing operations whether for fabrics, dishes, utensils, or other articles. Its mobility, efficiency, economy and versatility offer special advantages to institutional and commercial dish and laundry washing processes.
The present system provides for optimization of electrolysis conditions thereby enabling production of oxidizers from relatively inexpensive salts and with high current efficiency. Hence the cost per unit concentration of oxidizer is substantially lower than that of conventional oxidizer materials.
This system also eliminates the numerous hazards and inconveniences of handling such oxidizers as chlorine gas, and solid and ready-mixed hypochlorites.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention may be best understood by reference to the following description, taken in connection with the following drawings, in which:
FIG. 1 is a schematic drawing of the oxidizer generating and discharging system of this invention in its relation to a conventional washing apparatus.
FIG. 2 is a schematic drawing of the oxidizer generating and discharging system of this invention in combination with an electronic system which detects the reduction in the conductivity of the wash solution, and actuates a solenoid valve to allow water to flow through the detergent reservoir and the oxidizer reservoir. Solubilized detergent and oxidizer are then supplied to the wash tank by an overflow system.
FIG. 3 is a schematic drawing of the structure of one of the electrochemical cells employed in this invention.
FIG. 4 is a drawing of a preferred embodiment of the oxidizer generating and discharging system of this invention, particularly the electrochemical cell as it is incorporated in the salt reservoir.
FIG. 5 is a drawing of a preferred embodiment in which the electrochemical cell is located in a separate chamber outside the salt solution reservoir.
FIG. 6 is a schematic drawing of a preferred embodiment in which an independent oxidizer sensing device is used to regulate the addition of oxidizer into the wash solution in order to maintain a predetermined level of oxidizer in the wash solution.
DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1 illustrates the oxidizer generating and discharging unit in association with a washing apparatus. Washing apparatus 10 represents a conventional dish or laundry washing machine having wash tank 11 in its base. (By "wash tank" as used herein is meant a reservoir for the wash solution.) This is provided with valve controlled drain 12 and overflow 13 maintaining cleansing solution level 14. Disposed in an overhead position outside washing apparatus 10 is oxidizer reservoir 15 in which the oxidizer is electrochemically generated. Said reservoir is equipped with side drain 22 having valve 22A with the drain extending into wash tank 11, and overflow outlet 16 to which is attached dropspout 21 extending into wash tank 11. Incorporated into oxidizer reservoir 15 are electrodes 17 and 18 connected by loop 23 to rectifier 19 which provides power to the cell. Feed pipe 20 supplies water at a desired rate through oxidizer reservoir 15 thereby filling said reservoir to the overflow level determined by outlet 16. Oxidizer reservoir 15 contains a saturated solution of a salt preferably a halogen salt, which is converted to active halogen gas by electrolysis. The halogen gas becomes solubilized in reservoir 15. Side drain 22 delivers the initial addition of oxidizer to the wash solution. As additional water is fed to reservoir 15 through feed pipe 20, the overflow of oxidizer solution 24A passes through overflow outlet 16, into dropspout 21 to wash solution 25 thereby continually oxidizing the wash solution. The oxidizer requirement is controlled in oxidizer reservoir 15 by passage of a predetermined electrolysis current through oxidizer solution 24A.
The salt used in detergent reservoir 15 depends on the oxidizer desired. However, halogen salts such as the alkali metal and alkaline earth metal salts of chlorine, bromine and iodine are preferred.
A detergent-oxidizer composition can be added to reservoir 15 as the oxidizer source. The effluent from reservoir 15 provides for the addition of both oxidizer and detergent in sufficient amounts to efficiently oxidize and supply detergency to the wash solution 25.
FIG. 2 illustrates the oxidizer generating and discharging system of this invention in combination with an electronic system which controls the oxidizer requirements by detecting the reduction in the conductivity of the wash solution. Washing apparatus 26 represents a conventional dish or laundry washing machine having wash tank 27 in its base. This is provided with valve controlled drain 28 and overflow 29 maintaining cleansing solution level 30. Disposed in overhead positions outside wash tank 26 are oxidizer reservoir 31 and detergent reservoir 32 each having overflow outlet 33 and 34 respectively. The oxidizer reservoir 31 which is also equipped with side drain 53 extending into wash tank 26 contains sufficient amounts of a suitable salt to produce a saturated solution; detergent reservoir 32 contains a detergent powder. Side drain 53 includes valve 53A as a component thereof for control of initial charge to the wash tank. Incorporated into reservoir 31 are electrodes 35 and 36 connected by loop 37 to rectifier 38 which provides power from step down transformer 39.
Feed pipe 40 supplies water to oxidizer reservoir 31 and detergent reservoir 32 thereby filling said reservoirs to the overflow levels determined by overflow outlets 33 and 34. Adjustment of valves 41 and 42 in feed pipe 40, controls the amount of water which enters detergent reservoir 32 and oxidizer reservoir 31 thus, controlling the amount of oxidizer and detergent discharged into wash tank 27. The oxidizer is electrochemically generated in the oxidizer reservoir 31 and becomes solubilized in oxidizer solution 43. Conductivity electrode 44 which is connected by electrode cable 45 to electronic circuitry head 46 detects the reduction in the conductivity of the wash solution 47 and actuates solenoid valve 48 to allow water to flow through feed pipe 40 into the detergent reservoir 32 and the oxidizer reservoir 31. The overflow of detergent solution 49 passes through overflow outlet 34 into dropspout 50 to wash solution 47 thereby providing controlled detergency to said wash solution. The overflow of oxidizer solution 43 passes through overflow outlet 33 into dropspout 51 to wash solution 47 thereby oxidizing said solution. Solenoid valve 48 is connected by solenoid cable 52 to electronic circuitry head 46. Transformer 39 operates conductivity bridge and associated electronic circuitry head 46, in addition to supplying necessary current to rectifier 38.
Detergent reservoir 32 and connected dropspout 50 are not necessary to the successful operation of the oxidizer generating and discharging system of this invention. The oxidizing unit is adaptable to many commercial washing systems utilizing conventional methods of dispensing detergent.
In the washing operations described in FIGS. 1 and 2, one to three gallons of wash solution per 30 minutes are lost through overflow 29. To maintain a particular concentration of oxidizer in the wash solution, requisite quantities of oxidizer must be added intermittantly to compensate for the loss of oxidizer due to this overflow. By passing a specific electrolysis current through the oxidizer solution, enough oxidizer can be produced to maintain the desired level of oxidizer in the wash solution.
Referring now to FIG. 3, electrochemical cell 60 consists of a central long rectangular compartment 61 for anode 62 and two side compartments 63 and 64 half the length of anode chamber 61 where cathodes 65 equal in surface area to anode 62 are located. The three lucite compartments 61, 63 and 64 are separated from each other by lucite partitions 67 and 68, and are open at the bottom. Each compartment has vent 66 on top for escape of gases.
Electrochemical cell 60 as described above produces the optimum electrolysis result. The shorter cathode compartments 63 and 64 facilitate the escape of hydrogen gas evolved there, whereas the longer anode chamber 61 causes increased solubilization of chlorine gas to produce hypochlorite. Both anode 62 and cathodes 65 can be constructed of either graphite, titanium, a noble metal of the platinum group, or a deposit of a noble metal of the platinum group on titanium to prevent electrode corrosion in highly alkaline conditions and in the presence of wet halogen gas.
FIG. 4 illustrates a variation in the oxidizer generating and discharging system of this invention. The oxidizer is produced in a separate electrolysis chamber located inside the salt reservoir, and discharged from this chamber. Said resevoir 70 is divided into two compartments; electrolysis compartment 71 and salt solution compartment 72. Electrolysis chamber 71 houses anode 74 and cathodes 75 which are separated from each other by lucite panels 76 and 77. Salt solution 73 enters compartment 71 through opening 78. Electrolysis of a small volume of salt solution occurs in electrolysis chamber 71 enabling production of oxidizer at a concentration of about 6,000 parts per million. The oxidizer is discharged into the washing tank by means of delivery hose 84 connected to electrolysis compartment 71. Oxidizer solution level 79 is maintained by floating microswitch 80. As solution level 79 falls, the microswitch control circuit is broken and solenoid switch 81 is actuated to allow water to flow through feed pipe 82 and out of water jets 83. When the oxidizer solution 73 reaches the desired level and the microswitch control circuit is again completed, solenoid valve 81 is deactivated and feed pipe 82 closed. The electrochemical cells illustrated in FIGS. 3 and 4 and described above are the subject of commonly assigned U.S. application Ser. No. 74,715 filed Sept. 23, 1970.
FIG. 5 illustrates another variation in the oxidizer generating and discharging system of this invention. In this case the oxidizer is produced in a separate electrolysis chamber located outside the salt solution resevoir. Connected to salt solution chamber 85 is electrolysis chamber 86, containing either the electrochemical cell described in FIG. 3, or a cell with simple arrangement of a single cathode and anode as shown in FIG. 5. Electrolysis chamber 86 is equipped with vent 87 for the escape of hydrogen gas evolved at the cathodes. Salt solution 88 is displaced into electrolysis chamber 86 through valve 89 and dropspout 90. Electrolysis of a small volume of said salt solution occurs in electrolysis chamber 86 enabling production of oxidizer at a concentration of above 5,000 parts per million of oxidizer in about 700 milliliters of salt solution. The oxidizer is discharged into the wash tank through dropspout 91. Continual maintenance of salt solution level 92 is accomplished by regulating the input of fresh water into the salt solution chamber 85. Fresh water entering at the base of the oxidizer solution chamber 85 displaces concentrated oxidizer solution 88 into electrolysis chamber 86. Subsequently, the rate of overflow from salt solution chamber 85 governs the amount of oxidizer discharged into the wash tank. The input of fresh water can be controlled by either regulating mechanical valve 94 or electronic valve 95.
FIG. 6 illustrates the use of an independent oxidizer sensing electrode in an oxidizer generating and dispensing system similar to that described in FIG. 2.
Independent oxidizer sensing electrode 98 is incorporated into wash tank 99- and connected by electrode cable 100 to electronic circuitry head 101. Disposed in an overhead position outside wash tank 99 is oxidizer reservoir 104 in which the oxidizer is electrochemically generated. Said resevoir is equipped with overflow outlet 105 to which is attached drop-spout 106 extending into wash tank 99. Incorporated into oxidizer reservoir 104 are electrodes 107 and 108 connected by loop 109 to rectifier 110 which provides power from step down transformer 111. Oxidizer reservoir 104 is filled to the overflow level determined by outlet 105 with saturated salt solution 113. Chlorine sensing electrode 98, which is continually exposed to wash solution 112 detects the reduction in concentration of the oxidizer and actuates solenoid valve 102 thereby allowing water to flow through feed pipe 103 into oxidizer reservoir 104. The oxidizer solution 113 displaced by fresh water from feed pipe 103 passes through overflow outlet 105 into dropspout 106 to wash solution 112 thereby maintaining a predetermined concentration of oxidizer in said wash solution. Solenoid valve 102 is connected by cable 122 to electronic circuitry head 101. Transformer 111 operates electronic circuitry head 101. Conductivity electrode 114 is incorporated into wash tank 99, and connected by electrode cable 115 to electronic circuitry head 116. Disposed in an overhead position out side wash tank 99 is detergent reservoir 117 equipped with overflow outlet 118 to which is connected dropspout 119. Detergent reservoir 117 is filled to the overflow level determined by overflow outlet 118 with detergent solution 121. Conductivity electrode 114 detects the reduction in the conductivity of wash solution 112 and actuates solenoid valve 119 to allow water to flow through feed pipe 120 into the detergent reservoir 117. The overflow of detergent solution 121 passes through overflow outlet 118 into dropspout 119 to wash solution 112 thereby supplying controlled detergency to said solution. Solenoid valve 119 is connected by cable 123 to electronic circuitry head 116. Transformer 124 operates conductivity bridge and associated electronic circuitry head 116.
The independent oxidizer sensing system illustrated in FIG. 6 provides an extremely efficient and accurate method of detecting the concentration of oxidizer in the wash solution and maintaining the predetermined concentration of oxidizer desired.
The independent oxidizer sensing electrodes which can be used for detecting the reduction in the concentration of various oxidizers are silver/silver chloride electrode for detecting the reduction in the concentration of available chlorine, silver/silver bromide electrode for detecting the reduction in the concentration of available bromine, and silver/silver iodine electrode for detecting the reduction in the concentration of available iodine.
The specific details on the use of the above-mentioned silver halide electrodes are known to those skilled in the art of electrochemistry. In addition to the use of silver halide electrodes, other types of sensing electrode systems which make use of the oxidizing property of the wash solution can be used.
Referring back to FIG. 2, the electronic method of controlling the amount of oxidizer as well as detergent discharged into wash solution 47 is based on detecting the conductivity of said solution. Other methods of determining the conductivity of wash solution 47 which would in turn actuate solenoid valve 48 to allow water to flow through detergent reservoir 32 and oxidizer reservoir 31 could be used with the oxidizer generating and discharging unit of this invention.
The concentration of oxidizer salt in the solution supplied to the electrolysis chamber can be within the range of from about 1. percent by weight to about the percent by weight at which the solution is saturated.
Mixtures of oxidizer sources can be used to take advantage of mutual potentiation and cash advantages. For example, the presence of small quantities of hypoiodites in a larger quantity of hypochlorite enhances the effectiveness of the latter in oxidizing and disinfecting.
In the practice of this invention, the voltage which can be used across the anode is from about 0.10 to about 5 volts and preferably from about 1.3 to about 2.5 volts with respect to the standard hydrogen electrode.
The concentration of oxidizer which can be attained in the wash solution by using the systems described in FIG. 1, 2 and 4, 5 and 6 is from about 20 to about 40 parts per million of available chlorine, from about 20 to about 100 parts per million of available bromine and from about 1 to about 10 parts per million of available iodine. Concentrations of oxidizer outside the ranges given above can be attained by variation of electrode size, cell volume, current passed across the electrodes and the delivery system.
Referring back to FIG. 5, the salt solution supplied to the electrolysis chamber from the salt solution chamber should be of sufficient concentration to effect very good current efficiency, i.e., greater than 50 percent. As indicated by the following chart, excellent current efficiency is attained when the concentration of the salt solution is greater than 8 percent by weight. Attainment of current efficiencies greater than 95 percent is possible when the electrochemical cell illustrated in FIG. 3 is employed.
% NaCl 4% 8 % 12 % 16 % 20 % 24 % ppm Cl 2 3300 4910 6220 6630 6600 6750 Produced % Current 34.8% 51.8% 65.6% 70.1% 69.7% 71.4% Efficiency
The invention is further illustrated by the following non-limiting examples.
EXAMPLE 1
The oxidizer generating and discharging unit illustrated in FIG. 2 was adapted to a commercial dishwasher. An oxidizer level of 25 parts per million of available chlorine and 0.4 percent concentration of detergent were maintained in the wash solution over a six hour period. The electrolysis current passed across the electrodes was 10 amperes. The direct current voltage passed across the electrodes was 6.6 volts.
The detergent and oxidizer discharge was controlled by a common solenoid valve which was actuated whenever the conductivity of the wash solution fell below a value corresponding to 0.4 percent detergent concentration. The conductivity attributed by the addition of brine solution along with the hypochlorite was taken into consideration and proper adjustment of the conductivity cell was made. The test run was conducted in the following manner.
The oxidizer reservoir having a capacity of 6.8 liters was filled with a saturated brine solution. A sufficient amount of detergent powder was placed in the detergent reservoir which was then filled with water. The electrochemical cell was energized and oxidizer production was begun one-half hour before the dishwasher was started. The electrochemical cell generated 905 parts per million of available chlorine in 6.8 liters of solution with 93 percent current efficiency. (Chlorine concentration was determined by standard titration procedures.) Before the dishwasher was started, 3 liters of solution from the oxidizer reservoir were added to the wash tank to produce 29.4 parts per million of available chlorine in 30 gallons of wash solution. The feed pipe valves were adjusted to allow twice as much water to enter the oxidizer reservoir as the detergent reservoir thereby controlling the amount of detergent and oxidizer discharged into the wash solution.
The dishwashing machine was packed with heavily soiled dishes and eating utensils, and then started. After completion of the washing operation, the dishes and utensils were thoroughly clean and free from any trace of food particles. Several loads of dishes were washed during the six hour period, and were found to be clean, bright and free from stain.
EXAMPLE 2
The identical procedure described in Example 1 was followed for generating and discharging hypobromite. The current was adjusted to 5 amperes for production of bromine. The oxidizer reservoir was filled with a saturated solution of sodium bromide and an oxidizer level of 25 parts per million of available bromine was maintained in the was solution over a six hour period. Heavily soiled dishes were cleaned with the wash solution containing hypobromite and were found to be extremely clean, bright and free from stain.
EXAMPLE 3
The identical procedure described in Example 1 was followed for generating and discharging hypoiodite. The current was adjusted to 0.35 amperes for production of iodine. The oxidizer reservoir was filled with a saturated solution of sodium iodide and an oxidizer level of 3 parts per million of available iodine was maintained in the wash solution over a six hour period. Heavily soiled dishes and utensils were cleaned with the wash solution containing hypoiodite and were found to be extremely clean, bright and free from stain.
EXAMPLE 4
The oxidizer generating and discharging unit illustrated in FIG. 1 was adapted to a commercial dishwasher. An oxidizer level of 25 parts per million of available chlorine was maintained in the wash solution over a one hour period. The electrolysis current passed across the electrodes was 10 amperes. The direct current voltage across the electrodes was 6.6 volts. The oxidizer discharge was controlled by feeding liquid at a rate of 100 ml per minute through the electrolysis chamber without the use of a conductivity cell. The test run was conducted in the following manner.
The oxidizer having a capacity of 6.8 liters was filled with a saturated brine solution. THe electrochemical cell was energized and oxidizer production was begun one-half hour before the dishwasher was started. The electrochemical cell generated 900 parts per million of available chlorine in 6.8 liters of solution. Before the dishwasher was started, 3 liters of solution from the oxidizer reservoir were added to the wash tank to produce 24 parts per million of available chlorine in 30 gallons of wash solution. The dishwasher was packed with heavily soiled dishes, glassware and eating utensils, and then started. A constant overflow of 100 milliliters per minute from the oxidizer reservoir maintained a oxidizer level of 25 parts per million available chlorine in the wash solution during the washing operation. The dishes subjected to this washing system were found to be sparkling clean and perfectly free from stain.
EXAMPLE 5
The identical procedure described in Example 4 was followed for generating and discharging hypobromide. The current was adjusted to 5 amperes for production of bromine. The oxidizer reservoir was filled with a saturated solution of sodium bromide and an oxidizer level of 25 parts per million of available bromine was maintained in the wash solution over a one hour period. Heavily soiled dishes, glassware and eating utensils were cleaned in the wash solution containing hypobromite and were found to be extremely clean, bright and free from stain.
EXAMPLE 6
The identical procedure described in Example 4 was followed for generating and discharging hypoiodite. The current was adjusted to 0.35 amperes for production of iodine. The oxidizer reservoir was filled with a saturated solution of sodium iodide and as oxidizer level of 3 parts per million of available iodine was maintained in the wash solution over a one hour period. Heavily soiled dishes, glassware and eating utensils were cleaned with the wash solution containing hypoiodite and were found to be extremely clean, bright and free from stain.
EXAMPLE 7
The oxidizer generating and discharging unit illustrated in FIG. 1 was adapted to a commercial dishwasher. An oxidizer level of 25 parts per million of available chlorine and a detergent level of 0.4 percent concentration of detergent were maintained in the wash solution over a one hour period. The electrolysis current passed across the electrodes was 10 amperes. The direct current voltage across the electrodes was 6.6 volts. The oxidizer and detergent discharge was controlled by feeding liquid at a rate of 100 milliliters per minute through the electrolysis chamber without the use of a conductivity cell. The test run was conducted in the following manner.
The oxidizer reservoir having a capacity of 6.8 liters was filled with a saturated brine solution. A sufficient amount of detergent powder was also added to the oxidizer reservoir. The electrochemical cell was energized and oxidizer production was begun one-half hour before the dishwasher was started. The electrochemical cell generated 900 parts per million of available chlorine in 6.8 liters of solution. Before the dishwasher was started, an initial charge of oxidizer and detergent were added to the wash tank to produce 30 parts per million of available chlorine and 0.4 percent detergent concentration in 30 gallons of wash solution. The dishwasher was packed with heavily soiled dishes, glassware and eating utensils, and then started. A constant overflow of 100 milliliters per minute from the combined oxidizer-detergent reservoir maintained an oxidizer level of 30 parts per million available chlorine and a detergent level of 0.4 percent detergent concentration in the wash solution during the washing opera-tion. The dishes subjected to this washing system were found to be sparkling clean and perfectly free from stain.
EXAMPLE 8
The oxidizer generating and discharging unit illustrated in FIG. 1 was adapted to a commercial dishwasher. The identical procedure described in Example 4 was followed for generating and discharging hypochlorite and hypobromite. The oxidizer solution was filled with a saturated solution of sodium chloride and sodium bromide wherein said salts are in a one to one ratio. A level of 25 parts per million of available oxidizer was maintained in the wash solution over a one hour period. Heavily soiled dishes, glassware and eating utensils were cleaned with the wash solution containing both hypochlorite and hypoiodite and were found to be extremely clean, bright and free from stain.
EXAMPLE 9
The oxidizer generating and discharging unit illustrated in FIG. 4 was adapted to a commercial dishwasher. An oxidizer level of 25 parts per million of available chlorine and 0.4 percent concentration of detergent were maintained in the wash solution over a period of five hours. The electrolysis current passed across the electrodes was 10 amperes. The voltage across the electrodes was 6.6 volts.
A pump regulated to discharge 60 ml. of hypochlorite solution per minute from the electrolysis compartment into the wash solution was used to maintain the 25 parts per million chlorine level. The test run was conducted in the following manner.
The salt solution compartment having a capacity of approximately 8 liters, and the electrolysis compartment were filled with a saturated sodium chloride solution. The electrochemical cell was energized and oxidizer production was begun one-half hour before the dishwasher was started. The electrochemical cell generated 5,000 parts per million of available chlorine in 1,000 milliliters of solution. Before the dishwasher was started an initial charge of oxidizer was added to produce 20 parts per million of available chlorine in 30 gallons of wash solution. (Chlorine concentration was determined by standard titration procedures.)
The dishwashing machine was packed with heavily soiled dishes and eating utensils, and then started. 60 ml/minute of oxidizer solution was pumped into the wash tank while the dishes were being washed. After completion of the washing operation, the dishes and utensils were thoroughly clean, and free from any trace of food particles.
EXAMPLE 10
The identical procedure described in Example 8 was followed for generating and discharging hypobromite. The current was adjusted to 5 amperes for production of bromine. The oxidizer solution compartment and electrolysis compartment were filled with a saturated solution of sodium bromide and an oxidizer level of 25 parts per million of available bromine was maintained in the wash solution over several hours. Heavily soiled dishes were cleaned with the wash solution containing hypobromite and were found to be extremely clean, bright and free from stain.
EXAMPLE 11
The identical procedure described in Example 8 was followed for generating and discharging hypoiodite. The current was adjusted to 5 amperes for production of bromine. The oxidizer solution compartment and electrolysis compartment were filled with a saturated solution of sodium iodide and an oxidizer level of 4 parts per million of available iodine was maintained in the wash solution over several hours. Heavily soiled dishes and utensils were cleaned with the wash solution containing hypoiodite and were found to be extremely clean, bright and free from stain.
EXAMPLE 12
The oxidizer generating and discharging unit illustrated in FIG. 5 was adapted to a commercial dishwasher to produce sodium hypochlorite from crystalline sodium chloride. An oxidizer level of 20 parts per million of available chlorine was maintained in the wash solution over a two hour period. The electrolysis current passed across the electrodes was 10 amperes.
The oxidizer discharge was controlled by feeding water at a predetermined rate of about 50 to about 60 ml per minute through the oxidizer solution chamber thereby controlling the amount of salt solution displaced into the electrolysis chamber and the subsequent overflow of oxidizer solution into the wash tank. The test run was conducted in the following manner. A saturated sodium chloride solution was produced by percolating fresh water through the crystalline sodium chloride in the salt solution chamber. The electrolysis chamber was filled with said solution, the electrochemical cell was energized and oxidizer production was begun one-half hour before the dishwasher was started. The electrochemical cell generated 6,000 p.p.m. of available chlorine in 700 ml of solution. Before the dishwasher was started 370 ml of the oxidizer solution was discharged into the wash tank by means of over-flow from the salt solution chamber. This charge provided the initial 2.2 grams of chlorine which is needed every 15 minutes to maintain an oxidizer level of 20 parts per million of available chlorine.
The dishwashing machine was packed with heavily soiled dishes and eating utensils, and then started. During the washing operation, the oxidizer solution in the electrolysis chamber was continually renewed and replaced at a rate of 50 to 60 milliliters per minute. The displaced oxidizer solution provided a continuous supply of not less than about 0.15 gram chlorine per minute thereby maintaining the oxidizer level of 20 parts per million of available chlorine in the wash solution. After completion of the washing operation the dishes and utensils were found to be thoroughly clear, bright and free from any trace of food particles or stain.
The following chart represents the chlorine production rate for the initial 30 minute period and 120 minutes actual operation
Grams of Chlorine Grams of Chlorine Generator Elapsed Chlorine Supplied each Supplied Each Minutes Level Minute to Washer 15 minutes ____________________________________________________________ ______________ 0 0 0 0 30 6000 2.22 - 45 3920 .19 2.94 60 3360 .17 2.52 75 3120 .16 2.34 90 3060 .15 2.29 105 2920 .16 2.40 120 2660 .15 2.28 135 2720 .15 2.25 150 2500 .15 2.25 ____________________________________________________________ ______________
EXAMPLE 13
An oxidizer generating and discharging system utilizing an independent chlorine sensing electrode as described in FIG. 6 was adapted to a commercial dishwasher. An oxidizer level of 25 parts per million of avallable chlorine was maintained in the wash solution over a six hour period. The electrolysis current passed across the electrodes was 10 amperes.
The test was conducted in the same manner as Example 4. However, in this case the oxidizer discharge was controlled independently from the detergent solution discharge. The silver/silver chloride electrode detected only the reduction in the concentration of available chlorine, and in turn actuated a solenoid valve of its own to cause an overflow of oxidizer into the wash solution. The dishwasher was operated in this manner for 6 hours. Several loads of dishes were washed, and were found to be clean, bright and free from stain.
It is to be understood that the foregoing detailed description is given merely by way of illustration and that many variations may be made therein without departing from the spirit or scope of this invention.
1. Field of the Invention
The present invention relates to a system for producing and discharging oxidizers such as sodium hypochlorite in washing operations. The oxidizer is produced by electrolysis of dissolved salts in required concentration and at a required rate to maintain a predetermined concentration of oxidizer in the wash solution. The oxidizer is discharged into the wash solution by utilization of an overflow system which can be either manually or electronically controlled. The present invention is particularly valuable where production and maintenance of oxidizers in a washing system is required on a continuous and automated basis.
2. Description of the Prior Art
Oxidizing agents are used extensively in various types of washing operations for such purposes as disinfecting, deodorizing and bleaching. The use of oxidizing agents such as chlorine and hypochlorites in washing operations, particularly institutional and commercial laundry and dishwashing systems is highly desirable because of the rapid washing processes utilized by institutions.
The hypochlorites, which are used extensively for increased detergency and stain removal in laundry and dishwashing systems are ordinarily produced by reacting gaseous chlorine with a hydroxide of sodium, calcium or potassium under carefully controlled conditions. Gaseous chlorine is readily obtainable by simple electrolysis of an aqueous solution of the corresponding chloride salt. The electrochemical generation of chlorine is widely practiced, and such processes are well developed in the art. However, there are many hazards and problems connected with supplying washing operations with active chlorine gas as well as hypochlorites.
Many conventional methods for the addition of chlorine and chlorine releasing compounds to wash solutions are based upon the chemical action of chlorine. While the direct introduction of gaseous chlorine from a pressurized source probably represents the simplest form of disinfecting and destaining this method has the disadvantages of requiring heavy and cumbersome pressure type storage cylinders to contain the supply of liquid or gaseous chlorine, and an expensive and delicately balanced metering system for regulating the delivery of the gas.
The use of granular solid-type oxidizers such as hypochlorite preparations are quite costly and very difficult to distribute uniformly throughout the wash solution. Ready mixed hypochlorites share a disadvantage with the solid hypochlorite preparations in being an expensive source of chlorine. Difficulties are also encountered in the storage, transportation, and fire prevention of ready mixed oxidizers such as hypochlorites.
The use of detergents containing chlorine releasing agents also presents a threat to the efficiency of washing systems. Many dish and laundry detergents containing both a chlorine releasing agent and a surfactant have brief shelf lives due to attack by chlorine on the surfactant. As a result, the overall effectiveness of the composition is reduced.
While previous attempts have been made to produce and supply washing systems with various oxidizers, especially chlorine gas and hypochlorites, these attempts have not been successful in developing a safe, efficient and inexpensive method for both generating oxidizers and discharging them in a regulated manner into washing systems in order to maintain a predetermined level of oxidizer in the wash solution.
SUMMARY OF THE INVENTION
It has now been found by the practice of this invention that a predetermined level of oxidizer can be maintained in a wash solution by utilization of a washing system which comprises a means for producing the oxidizer, and discharging it into the wash solution. The oxidizer is produced in a separate chamber from that in which the articles are washed. An electrochemical cell consisting of a set of electrodes may be incorporated into this chamber (hereafter referred to as the salt reservoir), or in a separate chamber. The electrodes are continuously exposed to a salt solution such as a sodium or potassium chloride, iodide or bromide singly or in combintion. A dropspout attached to an overflow outlet in the side wall of the oxidizer reservoir, a chamber in which the oxidizer is produced and/or stored, extends into the washing apparatus and discharges the oxidizer from said chamber to the wash solution. The amount of oxidizer discharge supplied to the wash solution can be controlled by a simple regulated overflow, or a sophisticated electronic control utilizing conductivity and/or the oxidation-reduction potential of the solution in the washing operation.
The present system of electrochemically generating an oxidizer such as chlorine and discharging it into a washing system can be adapted to various types of washing operations whether for fabrics, dishes, utensils, or other articles. Its mobility, efficiency, economy and versatility offer special advantages to institutional and commercial dish and laundry washing processes.
The present system provides for optimization of electrolysis conditions thereby enabling production of oxidizers from relatively inexpensive salts and with high current efficiency. Hence the cost per unit concentration of oxidizer is substantially lower than that of conventional oxidizer materials.
This system also eliminates the numerous hazards and inconveniences of handling such oxidizers as chlorine gas, and solid and ready-mixed hypochlorites.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention may be best understood by reference to the following description, taken in connection with the following drawings, in which:
FIG. 1 is a schematic drawing of the oxidizer generating and discharging system of this invention in its relation to a conventional washing apparatus.
FIG. 2 is a schematic drawing of the oxidizer generating and discharging system of this invention in combination with an electronic system which detects the reduction in the conductivity of the wash solution, and actuates a solenoid valve to allow water to flow through the detergent reservoir and the oxidizer reservoir. Solubilized detergent and oxidizer are then supplied to the wash tank by an overflow system.
FIG. 3 is a schematic drawing of the structure of one of the electrochemical cells employed in this invention.
FIG. 4 is a drawing of a preferred embodiment of the oxidizer generating and discharging system of this invention, particularly the electrochemical cell as it is incorporated in the salt reservoir.
FIG. 5 is a drawing of a preferred embodiment in which the electrochemical cell is located in a separate chamber outside the salt solution reservoir.
FIG. 6 is a schematic drawing of a preferred embodiment in which an independent oxidizer sensing device is used to regulate the addition of oxidizer into the wash solution in order to maintain a predetermined level of oxidizer in the wash solution.
DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1 illustrates the oxidizer generating and discharging unit in association with a washing apparatus. Washing apparatus 10 represents a conventional dish or laundry washing machine having wash tank 11 in its base. (By "wash tank" as used herein is meant a reservoir for the wash solution.) This is provided with valve controlled drain 12 and overflow 13 maintaining cleansing solution level 14. Disposed in an overhead position outside washing apparatus 10 is oxidizer reservoir 15 in which the oxidizer is electrochemically generated. Said reservoir is equipped with side drain 22 having valve 22A with the drain extending into wash tank 11, and overflow outlet 16 to which is attached dropspout 21 extending into wash tank 11. Incorporated into oxidizer reservoir 15 are electrodes 17 and 18 connected by loop 23 to rectifier 19 which provides power to the cell. Feed pipe 20 supplies water at a desired rate through oxidizer reservoir 15 thereby filling said reservoir to the overflow level determined by outlet 16. Oxidizer reservoir 15 contains a saturated solution of a salt preferably a halogen salt, which is converted to active halogen gas by electrolysis. The halogen gas becomes solubilized in reservoir 15. Side drain 22 delivers the initial addition of oxidizer to the wash solution. As additional water is fed to reservoir 15 through feed pipe 20, the overflow of oxidizer solution 24A passes through overflow outlet 16, into dropspout 21 to wash solution 25 thereby continually oxidizing the wash solution. The oxidizer requirement is controlled in oxidizer reservoir 15 by passage of a predetermined electrolysis current through oxidizer solution 24A.
The salt used in detergent reservoir 15 depends on the oxidizer desired. However, halogen salts such as the alkali metal and alkaline earth metal salts of chlorine, bromine and iodine are preferred.
A detergent-oxidizer composition can be added to reservoir 15 as the oxidizer source. The effluent from reservoir 15 provides for the addition of both oxidizer and detergent in sufficient amounts to efficiently oxidize and supply detergency to the wash solution 25.
FIG. 2 illustrates the oxidizer generating and discharging system of this invention in combination with an electronic system which controls the oxidizer requirements by detecting the reduction in the conductivity of the wash solution. Washing apparatus 26 represents a conventional dish or laundry washing machine having wash tank 27 in its base. This is provided with valve controlled drain 28 and overflow 29 maintaining cleansing solution level 30. Disposed in overhead positions outside wash tank 26 are oxidizer reservoir 31 and detergent reservoir 32 each having overflow outlet 33 and 34 respectively. The oxidizer reservoir 31 which is also equipped with side drain 53 extending into wash tank 26 contains sufficient amounts of a suitable salt to produce a saturated solution; detergent reservoir 32 contains a detergent powder. Side drain 53 includes valve 53A as a component thereof for control of initial charge to the wash tank. Incorporated into reservoir 31 are electrodes 35 and 36 connected by loop 37 to rectifier 38 which provides power from step down transformer 39.
Feed pipe 40 supplies water to oxidizer reservoir 31 and detergent reservoir 32 thereby filling said reservoirs to the overflow levels determined by overflow outlets 33 and 34. Adjustment of valves 41 and 42 in feed pipe 40, controls the amount of water which enters detergent reservoir 32 and oxidizer reservoir 31 thus, controlling the amount of oxidizer and detergent discharged into wash tank 27. The oxidizer is electrochemically generated in the oxidizer reservoir 31 and becomes solubilized in oxidizer solution 43. Conductivity electrode 44 which is connected by electrode cable 45 to electronic circuitry head 46 detects the reduction in the conductivity of the wash solution 47 and actuates solenoid valve 48 to allow water to flow through feed pipe 40 into the detergent reservoir 32 and the oxidizer reservoir 31. The overflow of detergent solution 49 passes through overflow outlet 34 into dropspout 50 to wash solution 47 thereby providing controlled detergency to said wash solution. The overflow of oxidizer solution 43 passes through overflow outlet 33 into dropspout 51 to wash solution 47 thereby oxidizing said solution. Solenoid valve 48 is connected by solenoid cable 52 to electronic circuitry head 46. Transformer 39 operates conductivity bridge and associated electronic circuitry head 46, in addition to supplying necessary current to rectifier 38.
Detergent reservoir 32 and connected dropspout 50 are not necessary to the successful operation of the oxidizer generating and discharging system of this invention. The oxidizing unit is adaptable to many commercial washing systems utilizing conventional methods of dispensing detergent.
In the washing operations described in FIGS. 1 and 2, one to three gallons of wash solution per 30 minutes are lost through overflow 29. To maintain a particular concentration of oxidizer in the wash solution, requisite quantities of oxidizer must be added intermittantly to compensate for the loss of oxidizer due to this overflow. By passing a specific electrolysis current through the oxidizer solution, enough oxidizer can be produced to maintain the desired level of oxidizer in the wash solution.
Referring now to FIG. 3, electrochemical cell 60 consists of a central long rectangular compartment 61 for anode 62 and two side compartments 63 and 64 half the length of anode chamber 61 where cathodes 65 equal in surface area to anode 62 are located. The three lucite compartments 61, 63 and 64 are separated from each other by lucite partitions 67 and 68, and are open at the bottom. Each compartment has vent 66 on top for escape of gases.
Electrochemical cell 60 as described above produces the optimum electrolysis result. The shorter cathode compartments 63 and 64 facilitate the escape of hydrogen gas evolved there, whereas the longer anode chamber 61 causes increased solubilization of chlorine gas to produce hypochlorite. Both anode 62 and cathodes 65 can be constructed of either graphite, titanium, a noble metal of the platinum group, or a deposit of a noble metal of the platinum group on titanium to prevent electrode corrosion in highly alkaline conditions and in the presence of wet halogen gas.
FIG. 4 illustrates a variation in the oxidizer generating and discharging system of this invention. The oxidizer is produced in a separate electrolysis chamber located inside the salt reservoir, and discharged from this chamber. Said resevoir 70 is divided into two compartments; electrolysis compartment 71 and salt solution compartment 72. Electrolysis chamber 71 houses anode 74 and cathodes 75 which are separated from each other by lucite panels 76 and 77. Salt solution 73 enters compartment 71 through opening 78. Electrolysis of a small volume of salt solution occurs in electrolysis chamber 71 enabling production of oxidizer at a concentration of about 6,000 parts per million. The oxidizer is discharged into the washing tank by means of delivery hose 84 connected to electrolysis compartment 71. Oxidizer solution level 79 is maintained by floating microswitch 80. As solution level 79 falls, the microswitch control circuit is broken and solenoid switch 81 is actuated to allow water to flow through feed pipe 82 and out of water jets 83. When the oxidizer solution 73 reaches the desired level and the microswitch control circuit is again completed, solenoid valve 81 is deactivated and feed pipe 82 closed. The electrochemical cells illustrated in FIGS. 3 and 4 and described above are the subject of commonly assigned U.S. application Ser. No. 74,715 filed Sept. 23, 1970.
FIG. 5 illustrates another variation in the oxidizer generating and discharging system of this invention. In this case the oxidizer is produced in a separate electrolysis chamber located outside the salt solution resevoir. Connected to salt solution chamber 85 is electrolysis chamber 86, containing either the electrochemical cell described in FIG. 3, or a cell with simple arrangement of a single cathode and anode as shown in FIG. 5. Electrolysis chamber 86 is equipped with vent 87 for the escape of hydrogen gas evolved at the cathodes. Salt solution 88 is displaced into electrolysis chamber 86 through valve 89 and dropspout 90. Electrolysis of a small volume of said salt solution occurs in electrolysis chamber 86 enabling production of oxidizer at a concentration of above 5,000 parts per million of oxidizer in about 700 milliliters of salt solution. The oxidizer is discharged into the wash tank through dropspout 91. Continual maintenance of salt solution level 92 is accomplished by regulating the input of fresh water into the salt solution chamber 85. Fresh water entering at the base of the oxidizer solution chamber 85 displaces concentrated oxidizer solution 88 into electrolysis chamber 86. Subsequently, the rate of overflow from salt solution chamber 85 governs the amount of oxidizer discharged into the wash tank. The input of fresh water can be controlled by either regulating mechanical valve 94 or electronic valve 95.
FIG. 6 illustrates the use of an independent oxidizer sensing electrode in an oxidizer generating and dispensing system similar to that described in FIG. 2.
Independent oxidizer sensing electrode 98 is incorporated into wash tank 99- and connected by electrode cable 100 to electronic circuitry head 101. Disposed in an overhead position outside wash tank 99 is oxidizer reservoir 104 in which the oxidizer is electrochemically generated. Said resevoir is equipped with overflow outlet 105 to which is attached drop-spout 106 extending into wash tank 99. Incorporated into oxidizer reservoir 104 are electrodes 107 and 108 connected by loop 109 to rectifier 110 which provides power from step down transformer 111. Oxidizer reservoir 104 is filled to the overflow level determined by outlet 105 with saturated salt solution 113. Chlorine sensing electrode 98, which is continually exposed to wash solution 112 detects the reduction in concentration of the oxidizer and actuates solenoid valve 102 thereby allowing water to flow through feed pipe 103 into oxidizer reservoir 104. The oxidizer solution 113 displaced by fresh water from feed pipe 103 passes through overflow outlet 105 into dropspout 106 to wash solution 112 thereby maintaining a predetermined concentration of oxidizer in said wash solution. Solenoid valve 102 is connected by cable 122 to electronic circuitry head 101. Transformer 111 operates electronic circuitry head 101. Conductivity electrode 114 is incorporated into wash tank 99, and connected by electrode cable 115 to electronic circuitry head 116. Disposed in an overhead position out side wash tank 99 is detergent reservoir 117 equipped with overflow outlet 118 to which is connected dropspout 119. Detergent reservoir 117 is filled to the overflow level determined by overflow outlet 118 with detergent solution 121. Conductivity electrode 114 detects the reduction in the conductivity of wash solution 112 and actuates solenoid valve 119 to allow water to flow through feed pipe 120 into the detergent reservoir 117. The overflow of detergent solution 121 passes through overflow outlet 118 into dropspout 119 to wash solution 112 thereby supplying controlled detergency to said solution. Solenoid valve 119 is connected by cable 123 to electronic circuitry head 116. Transformer 124 operates conductivity bridge and associated electronic circuitry head 116.
The independent oxidizer sensing system illustrated in FIG. 6 provides an extremely efficient and accurate method of detecting the concentration of oxidizer in the wash solution and maintaining the predetermined concentration of oxidizer desired.
The independent oxidizer sensing electrodes which can be used for detecting the reduction in the concentration of various oxidizers are silver/silver chloride electrode for detecting the reduction in the concentration of available chlorine, silver/silver bromide electrode for detecting the reduction in the concentration of available bromine, and silver/silver iodine electrode for detecting the reduction in the concentration of available iodine.
The specific details on the use of the above-mentioned silver halide electrodes are known to those skilled in the art of electrochemistry. In addition to the use of silver halide electrodes, other types of sensing electrode systems which make use of the oxidizing property of the wash solution can be used.
Referring back to FIG. 2, the electronic method of controlling the amount of oxidizer as well as detergent discharged into wash solution 47 is based on detecting the conductivity of said solution. Other methods of determining the conductivity of wash solution 47 which would in turn actuate solenoid valve 48 to allow water to flow through detergent reservoir 32 and oxidizer reservoir 31 could be used with the oxidizer generating and discharging unit of this invention.
The concentration of oxidizer salt in the solution supplied to the electrolysis chamber can be within the range of from about 1. percent by weight to about the percent by weight at which the solution is saturated.
Mixtures of oxidizer sources can be used to take advantage of mutual potentiation and cash advantages. For example, the presence of small quantities of hypoiodites in a larger quantity of hypochlorite enhances the effectiveness of the latter in oxidizing and disinfecting.
In the practice of this invention, the voltage which can be used across the anode is from about 0.10 to about 5 volts and preferably from about 1.3 to about 2.5 volts with respect to the standard hydrogen electrode.
The concentration of oxidizer which can be attained in the wash solution by using the systems described in FIG. 1, 2 and 4, 5 and 6 is from about 20 to about 40 parts per million of available chlorine, from about 20 to about 100 parts per million of available bromine and from about 1 to about 10 parts per million of available iodine. Concentrations of oxidizer outside the ranges given above can be attained by variation of electrode size, cell volume, current passed across the electrodes and the delivery system.
Referring back to FIG. 5, the salt solution supplied to the electrolysis chamber from the salt solution chamber should be of sufficient concentration to effect very good current efficiency, i.e., greater than 50 percent. As indicated by the following chart, excellent current efficiency is attained when the concentration of the salt solution is greater than 8 percent by weight. Attainment of current efficiencies greater than 95 percent is possible when the electrochemical cell illustrated in FIG. 3 is employed.
% NaCl 4% 8 % 12 % 16 % 20 % 24 % ppm Cl 2 3300 4910 6220 6630 6600 6750 Produced % Current 34.8% 51.8% 65.6% 70.1% 69.7% 71.4% Efficiency
The invention is further illustrated by the following non-limiting examples.
EXAMPLE 1
The oxidizer generating and discharging unit illustrated in FIG. 2 was adapted to a commercial dishwasher. An oxidizer level of 25 parts per million of available chlorine and 0.4 percent concentration of detergent were maintained in the wash solution over a six hour period. The electrolysis current passed across the electrodes was 10 amperes. The direct current voltage passed across the electrodes was 6.6 volts.
The detergent and oxidizer discharge was controlled by a common solenoid valve which was actuated whenever the conductivity of the wash solution fell below a value corresponding to 0.4 percent detergent concentration. The conductivity attributed by the addition of brine solution along with the hypochlorite was taken into consideration and proper adjustment of the conductivity cell was made. The test run was conducted in the following manner.
The oxidizer reservoir having a capacity of 6.8 liters was filled with a saturated brine solution. A sufficient amount of detergent powder was placed in the detergent reservoir which was then filled with water. The electrochemical cell was energized and oxidizer production was begun one-half hour before the dishwasher was started. The electrochemical cell generated 905 parts per million of available chlorine in 6.8 liters of solution with 93 percent current efficiency. (Chlorine concentration was determined by standard titration procedures.) Before the dishwasher was started, 3 liters of solution from the oxidizer reservoir were added to the wash tank to produce 29.4 parts per million of available chlorine in 30 gallons of wash solution. The feed pipe valves were adjusted to allow twice as much water to enter the oxidizer reservoir as the detergent reservoir thereby controlling the amount of detergent and oxidizer discharged into the wash solution.
The dishwashing machine was packed with heavily soiled dishes and eating utensils, and then started. After completion of the washing operation, the dishes and utensils were thoroughly clean and free from any trace of food particles. Several loads of dishes were washed during the six hour period, and were found to be clean, bright and free from stain.
EXAMPLE 2
The identical procedure described in Example 1 was followed for generating and discharging hypobromite. The current was adjusted to 5 amperes for production of bromine. The oxidizer reservoir was filled with a saturated solution of sodium bromide and an oxidizer level of 25 parts per million of available bromine was maintained in the was solution over a six hour period. Heavily soiled dishes were cleaned with the wash solution containing hypobromite and were found to be extremely clean, bright and free from stain.
EXAMPLE 3
The identical procedure described in Example 1 was followed for generating and discharging hypoiodite. The current was adjusted to 0.35 amperes for production of iodine. The oxidizer reservoir was filled with a saturated solution of sodium iodide and an oxidizer level of 3 parts per million of available iodine was maintained in the wash solution over a six hour period. Heavily soiled dishes and utensils were cleaned with the wash solution containing hypoiodite and were found to be extremely clean, bright and free from stain.
EXAMPLE 4
The oxidizer generating and discharging unit illustrated in FIG. 1 was adapted to a commercial dishwasher. An oxidizer level of 25 parts per million of available chlorine was maintained in the wash solution over a one hour period. The electrolysis current passed across the electrodes was 10 amperes. The direct current voltage across the electrodes was 6.6 volts. The oxidizer discharge was controlled by feeding liquid at a rate of 100 ml per minute through the electrolysis chamber without the use of a conductivity cell. The test run was conducted in the following manner.
The oxidizer having a capacity of 6.8 liters was filled with a saturated brine solution. THe electrochemical cell was energized and oxidizer production was begun one-half hour before the dishwasher was started. The electrochemical cell generated 900 parts per million of available chlorine in 6.8 liters of solution. Before the dishwasher was started, 3 liters of solution from the oxidizer reservoir were added to the wash tank to produce 24 parts per million of available chlorine in 30 gallons of wash solution. The dishwasher was packed with heavily soiled dishes, glassware and eating utensils, and then started. A constant overflow of 100 milliliters per minute from the oxidizer reservoir maintained a oxidizer level of 25 parts per million available chlorine in the wash solution during the washing operation. The dishes subjected to this washing system were found to be sparkling clean and perfectly free from stain.
EXAMPLE 5
The identical procedure described in Example 4 was followed for generating and discharging hypobromide. The current was adjusted to 5 amperes for production of bromine. The oxidizer reservoir was filled with a saturated solution of sodium bromide and an oxidizer level of 25 parts per million of available bromine was maintained in the wash solution over a one hour period. Heavily soiled dishes, glassware and eating utensils were cleaned in the wash solution containing hypobromite and were found to be extremely clean, bright and free from stain.
EXAMPLE 6
The identical procedure described in Example 4 was followed for generating and discharging hypoiodite. The current was adjusted to 0.35 amperes for production of iodine. The oxidizer reservoir was filled with a saturated solution of sodium iodide and as oxidizer level of 3 parts per million of available iodine was maintained in the wash solution over a one hour period. Heavily soiled dishes, glassware and eating utensils were cleaned with the wash solution containing hypoiodite and were found to be extremely clean, bright and free from stain.
EXAMPLE 7
The oxidizer generating and discharging unit illustrated in FIG. 1 was adapted to a commercial dishwasher. An oxidizer level of 25 parts per million of available chlorine and a detergent level of 0.4 percent concentration of detergent were maintained in the wash solution over a one hour period. The electrolysis current passed across the electrodes was 10 amperes. The direct current voltage across the electrodes was 6.6 volts. The oxidizer and detergent discharge was controlled by feeding liquid at a rate of 100 milliliters per minute through the electrolysis chamber without the use of a conductivity cell. The test run was conducted in the following manner.
The oxidizer reservoir having a capacity of 6.8 liters was filled with a saturated brine solution. A sufficient amount of detergent powder was also added to the oxidizer reservoir. The electrochemical cell was energized and oxidizer production was begun one-half hour before the dishwasher was started. The electrochemical cell generated 900 parts per million of available chlorine in 6.8 liters of solution. Before the dishwasher was started, an initial charge of oxidizer and detergent were added to the wash tank to produce 30 parts per million of available chlorine and 0.4 percent detergent concentration in 30 gallons of wash solution. The dishwasher was packed with heavily soiled dishes, glassware and eating utensils, and then started. A constant overflow of 100 milliliters per minute from the combined oxidizer-detergent reservoir maintained an oxidizer level of 30 parts per million available chlorine and a detergent level of 0.4 percent detergent concentration in the wash solution during the washing opera-tion. The dishes subjected to this washing system were found to be sparkling clean and perfectly free from stain.
EXAMPLE 8
The oxidizer generating and discharging unit illustrated in FIG. 1 was adapted to a commercial dishwasher. The identical procedure described in Example 4 was followed for generating and discharging hypochlorite and hypobromite. The oxidizer solution was filled with a saturated solution of sodium chloride and sodium bromide wherein said salts are in a one to one ratio. A level of 25 parts per million of available oxidizer was maintained in the wash solution over a one hour period. Heavily soiled dishes, glassware and eating utensils were cleaned with the wash solution containing both hypochlorite and hypoiodite and were found to be extremely clean, bright and free from stain.
EXAMPLE 9
The oxidizer generating and discharging unit illustrated in FIG. 4 was adapted to a commercial dishwasher. An oxidizer level of 25 parts per million of available chlorine and 0.4 percent concentration of detergent were maintained in the wash solution over a period of five hours. The electrolysis current passed across the electrodes was 10 amperes. The voltage across the electrodes was 6.6 volts.
A pump regulated to discharge 60 ml. of hypochlorite solution per minute from the electrolysis compartment into the wash solution was used to maintain the 25 parts per million chlorine level. The test run was conducted in the following manner.
The salt solution compartment having a capacity of approximately 8 liters, and the electrolysis compartment were filled with a saturated sodium chloride solution. The electrochemical cell was energized and oxidizer production was begun one-half hour before the dishwasher was started. The electrochemical cell generated 5,000 parts per million of available chlorine in 1,000 milliliters of solution. Before the dishwasher was started an initial charge of oxidizer was added to produce 20 parts per million of available chlorine in 30 gallons of wash solution. (Chlorine concentration was determined by standard titration procedures.)
The dishwashing machine was packed with heavily soiled dishes and eating utensils, and then started. 60 ml/minute of oxidizer solution was pumped into the wash tank while the dishes were being washed. After completion of the washing operation, the dishes and utensils were thoroughly clean, and free from any trace of food particles.
EXAMPLE 10
The identical procedure described in Example 8 was followed for generating and discharging hypobromite. The current was adjusted to 5 amperes for production of bromine. The oxidizer solution compartment and electrolysis compartment were filled with a saturated solution of sodium bromide and an oxidizer level of 25 parts per million of available bromine was maintained in the wash solution over several hours. Heavily soiled dishes were cleaned with the wash solution containing hypobromite and were found to be extremely clean, bright and free from stain.
EXAMPLE 11
The identical procedure described in Example 8 was followed for generating and discharging hypoiodite. The current was adjusted to 5 amperes for production of bromine. The oxidizer solution compartment and electrolysis compartment were filled with a saturated solution of sodium iodide and an oxidizer level of 4 parts per million of available iodine was maintained in the wash solution over several hours. Heavily soiled dishes and utensils were cleaned with the wash solution containing hypoiodite and were found to be extremely clean, bright and free from stain.
EXAMPLE 12
The oxidizer generating and discharging unit illustrated in FIG. 5 was adapted to a commercial dishwasher to produce sodium hypochlorite from crystalline sodium chloride. An oxidizer level of 20 parts per million of available chlorine was maintained in the wash solution over a two hour period. The electrolysis current passed across the electrodes was 10 amperes.
The oxidizer discharge was controlled by feeding water at a predetermined rate of about 50 to about 60 ml per minute through the oxidizer solution chamber thereby controlling the amount of salt solution displaced into the electrolysis chamber and the subsequent overflow of oxidizer solution into the wash tank. The test run was conducted in the following manner. A saturated sodium chloride solution was produced by percolating fresh water through the crystalline sodium chloride in the salt solution chamber. The electrolysis chamber was filled with said solution, the electrochemical cell was energized and oxidizer production was begun one-half hour before the dishwasher was started. The electrochemical cell generated 6,000 p.p.m. of available chlorine in 700 ml of solution. Before the dishwasher was started 370 ml of the oxidizer solution was discharged into the wash tank by means of over-flow from the salt solution chamber. This charge provided the initial 2.2 grams of chlorine which is needed every 15 minutes to maintain an oxidizer level of 20 parts per million of available chlorine.
The dishwashing machine was packed with heavily soiled dishes and eating utensils, and then started. During the washing operation, the oxidizer solution in the electrolysis chamber was continually renewed and replaced at a rate of 50 to 60 milliliters per minute. The displaced oxidizer solution provided a continuous supply of not less than about 0.15 gram chlorine per minute thereby maintaining the oxidizer level of 20 parts per million of available chlorine in the wash solution. After completion of the washing operation the dishes and utensils were found to be thoroughly clear, bright and free from any trace of food particles or stain.
The following chart represents the chlorine production rate for the initial 30 minute period and 120 minutes actual operation
Grams of Chlorine Grams of Chlorine Generator Elapsed Chlorine Supplied each Supplied Each Minutes Level Minute to Washer 15 minutes ____________________________________________________________ ______________ 0 0 0 0 30 6000 2.22 - 45 3920 .19 2.94 60 3360 .17 2.52 75 3120 .16 2.34 90 3060 .15 2.29 105 2920 .16 2.40 120 2660 .15 2.28 135 2720 .15 2.25 150 2500 .15 2.25 ____________________________________________________________ ______________
EXAMPLE 13
An oxidizer generating and discharging system utilizing an independent chlorine sensing electrode as described in FIG. 6 was adapted to a commercial dishwasher. An oxidizer level of 25 parts per million of avallable chlorine was maintained in the wash solution over a six hour period. The electrolysis current passed across the electrodes was 10 amperes.
The test was conducted in the same manner as Example 4. However, in this case the oxidizer discharge was controlled independently from the detergent solution discharge. The silver/silver chloride electrode detected only the reduction in the concentration of available chlorine, and in turn actuated a solenoid valve of its own to cause an overflow of oxidizer into the wash solution. The dishwasher was operated in this manner for 6 hours. Several loads of dishes were washed, and were found to be clean, bright and free from stain.
It is to be understood that the foregoing detailed description is given merely by way of illustration and that many variations may be made therein without departing from the spirit or scope of this invention.