Title:
Electrostatic precipitator central monitor and control system
United States Patent 3893828


Abstract:
The operating functions of Electrostatic Precipitators are monitored and controlled by a digital data processing computer system in which the conditions of the precipitator power supplies and electrode cleaning devices, the dust disposal system, and the emission stack of the precipitators are monitored and controlled. The operating conditions may be utilized according to predetermined functions and standards, and the data recorded and stored, to provide control for the system, as well as the recording and storage of the data. A fast, efficient and reliable system utilizing digital data processing techniques is realized.



Inventors:
ARCHER WILLIAM E
Application Number:
05/484360
Publication Date:
07/08/1975
Filing Date:
06/28/1974
Assignee:
WAHLCO, INC
Primary Class:
Other Classes:
96/32
International Classes:
B03C3/68; (IPC1-7): B03C3/68
Field of Search:
55/104,105,108,112,110,139,466,428,432,210,218 444
View Patent Images:



Primary Examiner:
Talbert Jr., Dennis E.
Attorney, Agent or Firm:
Sandler, Howard E.
Parent Case Data:


This is a continuation, of application Ser. No. 379,637, filed June 11, 1973, and now abandoned.
Claims:
I claim

1. An emission monitor and control system for an industrial electrostatic precipitator used to remove particulate contaminants from process waste gases prior to discharging such waste gases into the atmosphere comprising: condition responsive means operatively connected to said precipitator for sensing power supply, and rapper and dust disposal operating conditions and exhaust gas contact conditions; and computer monitoring and display means in operative communication with said condition responsive means for monitoring said conditions.

2. An emission monitor and control system as set forth in claim 1 wherein said computer monitoring and display means is responsively connected to control the operating parameters of said system in accordance with functions of said operating conditions.

3. An emission monitor and control system as set forth in claim 2 wherein the portion of said condition responsive means for sensing power supply operating conditions senses the primary voltage and current, the precipitator voltage and current, and the spark rate of said precipitator.

4. An emission monitor and control system as set forth in claim 3 wherein the portion of said condition responsive means for sensing electrode cleaning device operating conditions senses the actual functioning of individual electrode cleaning devices.

5. An emission monitor and control system as set forth in claim 4 wherein the portion of said condition responsive means for sensing dust disposal operating conditions senses the temperature differential in the hopper and feeder of the dust disposal system and the level of dust in the hopper.

6. An emission monitor and control system as set forth in claim 5 wherein the portion of said condition responsive means for sensing stack flow conditions senses the particulate content in the gas leaving said precipitator.

7. An emission monitor and control system as set forth in claim 6 wherein said computer monitoring and display means is responsively connected to control the operating parameters of said precipitator according to said power supply operating conditions and said electrode cleaning devices operating conditions.

8. An emission monitor and control system as set forth in claim 6 wherein said computer monitoring and display means is responsively connected to control the operating parameters of said precipitator according to said dust disposal operating conditions.

9. An emission monitor and control system as set forth in claim 6 wherein said computer monitoring and display means is responsively connected to control the operating parameters of said precipitator according to the particulate content of gas leaving said precipitator.

10. An emission monitor and control system as set forth in claim 6 wherein said computer monitoring and display means is responsively connected to control the operating parameters of said precipitator according to said dust disposal operating conditions and said particulate content.

Description:
BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to industrial precipitators for removing foreign particles from the emission gas and more particularly to a computer control and display system for monitoring and controlling the operating parameters of a precipitator system in accordance with the desired conditions.

2. Description of the Prior Art

The growing number of regulations limiting the permissable emissions from industrial sources has forced industry to take immediate and drastic steps in the control of stack emissions. Because of the regulations which severely limit the range of allowable stack emissions, even minor malfunctions in the equipment operation or operating conditions can cause serious difficulties and unacceptable smoke from the stack.

In a typical system, an electrostatic precipitator is operated at its most efficient condition by maintaining the precipitating voltage at a proper level determined by the spark rate and other parameters. Systems and circuits are known which attempt to select optimum voltage ranges for particular gas and dust conditions in the precipitator. However, these controls do not take into account the other operating conditions in the remainder of the system; for example, operating conditions of the dust disposal system and flow distribution may be such as to provide an undesirable stack emission which is not sensed by precipitator controls.

In a typical industrial system, control rooms may contain only limited monitoring and enunciating systems which do not provide an indication of impending trouble in the precipitator. Trouble is reported only after the fact which is too late to correct the problem before severe damage is caused. Additionally, there may be provided a stack optical emission monitor. The typical system contains no means for anticipating trouble as it develops in the precipitator functions and consequently timely maintenance cannot be performed to head off serious malfunctions or shutdowns before they occur. This results in a loss of collection efficiency which causes excessive stack emissions and resulting curtailment or complete shutdown of production.

In prior art precipitator control systems automatic means are provided for maintaining the precipitator operating voltage in the desired range for maximum efficiency; however, malfunctioning in the other parts of the overall system such as the dust disposal system, for example, can cause changes in the system operation which are not sensed by the precipitator controls. The purpose of the precipitator controls is to maintain an optimum voltage across the precipitator electrodes. The failure of the dust disposal system cannot be sensed by sensing the precipitator voltage. The proper functioning of the electrode cleaning devices is essential to the maintenance of precipitator operation and efficiency. These conditions may appear on the precipitator control system yet there is no way to determine the source of the malfunctioning until serious emission from the stack occurs. This is totally unacceptable to any operating system.

Accordingly, a central system for monitoring and controlling the emission from an electrostatic precipitator by taking into account all the operating conditions in the components that make up the system is needed. In order to provide an accurate and reliable pollution control system to meet stringent requirements, the monitor and control system must be operated in such a way as to anticipate malfunctioning so that repairs can be accomplished before the stack emission reaches a critical level.

Accordingly, it is a primary object of this invention to provide a central monitor and control system for an electrostatic precipitator in an accurate reliable and foolproof manner.

SUMMARY OF THE INVENTION

In brief, the particular apparatus and method in accordance with the present invention utilizes a computer control and display system for monitoring and controlling the emission from electrostatic precipitators. Each of the primary elements of the precipitator system; the power supplies and electrode cleaning devices, the feeder and valves of the dust disposal system, and the particulate content of the exit gas, are sensed by responsive means which provide signals fed through multiplexers to monitor and control devices in a centralized control room where the signals are monitored and controlled according to predetermined parameters to provide signals in the form of records, alarms, displays and control signals for changing the operating conditions. In the electrostatic precipitator, signals indicative of the voltages and currents at the primary and secondary of the precipitator, the spark rate, and the functioning of the rappers are combined in the multiplexer and fed to the central control area. In the dust disposal system, signals indicative of the temperature rise of the hopper, the dust level in the hopper, the feeder temperature rise, and the functioning of the upper and lower valves are fed to the central control area. A signal indicative of the outlet (or exit) cleanliness gas is fed to the central control area.

An important aspect of the invention is the aforementioned monitoring of the signals in the central control area to provide a complete record and real time display of operating conditions. Additionally, signals are fed into a computer which is programmed in accordance with predetermined parameters to provide control signals to the precipitator and dust disposal system to provide a change in function responsive to changes in the operating conditions.

The multiplexing feature of the monitor and control system of the invention adapts it especially for adding it to existing precipitator systems without the expense of hard wiring or interference with existing plant facilities.

In the monitoring aspect of the system, a complete record and display of the operating conditions is provided which among other things provides a means for verifying the actual functioning of the system in addition to the exact operating conditions that are occurring. For example in rapper control, the command and exact functioning of the individual rappers is monitored and displayed to enchance the maintenance and reliability of the rappers.

According to the control aspect of the invention, the operating conditions of the precipitator, dust disposal system, and flue gas emission, are maintained in the computer control where they are continuously checked and monitored by the system which provides correctional controls to change the operating parameters as needed in addition to providing alarm signals and maintenance instructions as well as supervisory check lists.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram illustrating the basic function of the monitoring control system of the invention; and

FIG. 2 is a schematic block diagram illustrating in more detail the monitor and control system of the invention.

DESCRIPTION OF A PREFERRED EMBODIMENT

As illustrated in the brief schematic diagram of FIG. 1, the operating conditions of the parts of the precipitator system are measured by condition responsive transducers 11 which feed signals through a multiplexer system 13 to the computer control and monitor system 15. Typical of the signals measured are the primary and secondary currents and voltages from the precipitator power supplies, the spark rate across precipitator electrodes, the functioning of the precipitator electrode cleaning devices, the temperatures at the hopper, and the feeder of the dust disposal system, the level of dust in the hopper, the functioning of the feeder valves in the dust disposal system and the opacity of the gas leaving the precipitator. The computer control and monitor 15 provides a suitable display and record of the signals fed through the multiplexer 13 on a real time basis or on a storage basis. In this manner a complete monitor and control system is provided which among other things acquires and logs data, checks against limits and generates alarms, provides periodic records, and displays status for the various components of the system. The control function is responsive to all of the above mentioned input signals and will adjust the operation of the various system components for optimum overall performance.

Referring now to FIG. 2, there is illustrated in schematic form, the system of FIG. 1 in more detail in which a typical power plant system is shown as an example where signals are fed from a precipitator 17 into a control room 19 and a control console system 21. The control room 19, which is typically near the power generating equipment, receives the current voltage and spark rate signals from the precipitator power supplies 23 and displays the signals on a monitor panel 25 in the control room 19. Additionally, signals from the rappers 25 indicating the function of the rapper as a result of a command signal from a rapper control timer 27 in the control room 19 are indicated. Further, the signals from the rapper are fed through a field multiplexer 27 to the control console area 21. Thus, in addition to the standard display readings for operating conditions of the precipitator, signals indicating the function of the rappers themselves in addition to the power supplies are fed to the central console area 21 and into a computer 26 therein, which provides the necessary control to change the actual operating conditions of the precipitator.

In the ash disposal system, the signals indicative of the temperature of the hopper 28 are fed on line 29 through a field multiplexer 31 to the computer 26. In addition, a temperature differential at the feeder is fed on line 35 through the multiplexer 31 to the computer 26. These temperature signals are utilized in the computer 26 to provide an alarm and control signal which indicates the proper functioning of the ash disposal system. In addition the high ash level of the hopper 28 is suitably measured at 37 and fed through a multiplexer 39 to the mini computer 26. The functioning of the upper feeder valve 41 and the lower feeder valve 43 is fed through the multiplexer 39 to the mini computer 26. The volume of flow through the stack 47 is measured by a suitable transducer 49 and fed through a field multiplexer 51 to the computer 26.

In the control console area 21, the computer 26 has associated therewith a typical display and record device such as a cathode ray tube 53, a teletype 55, a tape cassette 57 and a line printer 59. These devices operate in accordance with a well known digital control manner to provide the necessary display in records of the results of the operating conditions measured by the transducers.

As an example of a typical control that can be provided by the system of the present invention, the malfunctioning of the ash disposal system may be measured by a signal along line 29 which indicates that the temperature of the hopper is substantially equal to the ambient temperature. This is a clear indication that the ash is not moving along the hopper and the system is malfunctioning. Such a signal fed to the computer 26 and displayed thereon will provide an alarm signal indicating that the hopper did not actually empty even though the ash handling system functioned. This will provide time for remedial action before the hopper overfills. In another example an increase in the emission from one precipitator unit as measured by transducer 49 and fed to the computer 26 can be used as a signal to reduce the gas volume to that particular unit and thereby balancing the gas distribution resulting in higher collection efficiency.

A special advantage of the system of this invention is the ability to monitor all of the operating conditions of the entire precipitator system displaying and controlling these conditions in a single control console area. In this way, maintainence and operability is greatly enhanced.

By providing a central indication of all of the operating conditions of the system at the normal control station for the process, equipment down time is greatly minimized. For example, an accidental overfilling of the hopper of the ash disposal system may be prevented by correlating the operation of the hopper emptying at the upper feeder valve 41 with the actual hopper temperature at 29. This may easily be provided in the computer 26.

Installation and cost of the system of this invention is minimized by utilizing existing transducers and multiplexing techniques to the maximum.

While the invention has been illustrated by a specific embodiment, the invention is not limited to specific devices or configurations. It is to be realized that the invention disclosed herein does not involve particular circuits or particular digital data processing techniques. It is to be realized that the invention disclosed herein does not involve particular circuits or particular digital data processing techniques. It is to be realized that it is well within the skill of the art to provide various components in the control console area 21 for example. These operate according to a standard digital data processing control technique well known in the art and not described in detail herein. Further the actual transducers utilized for measuring the operating conditions at the various elements is a matter of design choice and not a part of this invention. The field multiplexers and the central multiplexer may be selected in accordance with techniques well known in the art. The primary object of providing multiplexing is to realize a real time display monitor and control system.