Title:
Process of treating coal and composition therefor
United States Patent 2089599


Abstract:
This invention relates to a process for the treating of coal and the burning of the same, which coal contains relatively large amounts of iron sulphur compounds, such as iron pyrites, for the purpose of improving the burning of the coal, obviating deleterious flue gas and tube slagging, and...



Inventors:
Crecelius, Lawrence P.
Application Number:
US60954932A
Publication Date:
08/10/1937
Filing Date:
05/05/1932
Assignee:
Crecelius, Lawrence P.
Primary Class:
Other Classes:
44/604, 44/905, 423/512.1, 423/532, 423/539
International Classes:
C10L9/10
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Description:

This invention relates to a process for the treating of coal and the burning of the same, which coal contains relatively large amounts of iron sulphur compounds, such as iron pyrites, for the purpose of improving the burning of the coal, obviating deleterious flue gas and tube slagging, and to improve the ash characteristics.

The advance in the art of power production in power plants has been signalized by much higher rates of burning of coal in furnaces than heretofore practiced and an accompanying relative diminution of the air supplied for two main purposes. The higher rates of burning of coal was done for the purpose of increasing the capacity of a given plant, and the second purpose of relative diminution of air supplied was effected for the purpose of decreasing stack losses. The effect of this advance or change in practice, has been to bring about much higher furnace temperatures than were usually regarded as good practice in the past. It has also decreased very materially the amount of air available for oxidizing the various elements in the coal used for combustion. Furthermore, it has operated to increase the speed of heat liberation, and, therefore, decrease the time element for combustion.

The whole effect in this change in the art has operated to disqualify and eliminate, to a very 80 large extent, the use of coals high in iron sulphur compounds, such as are mined in western Pennsylvania, Ohio, Indiana, Illinois and many other states. The reason for the foregoing is the objectionable and disastrous clinkering which is produced by coals high in Iron sulphur compounds, which when subjected to the furnace conditions mentioned before, decompose to ferrous sulphide, which melts at approximately 2140° F., running down on to the grate surfaces, obstructing to a large extent the passage of air through the grates, and additionally, fusing to the iron of the grate bars, thereby becoming permanently affixed thereto. In the second place, due to the high blasting for heavy overloads, 5 particles of coal are driven off from the burning fuel and are blasted against the boiler tube surfaces. Owing to the high temperature of the furnaces, in excess of 2140° F., the ferrous sul0 phide particles which are carried by the coal are more or less plastic and accumulate on such tube surfaces, permanently fastening themselves to such surfaces and giving rise to tube slagging.

In the third place these ferrous sulphide particles collect on the economizer and preheater surfaces, where, due to the low temperature, the ferrous sulphide oxidizes to ferric sulphate, which converts sulphur dioxide of the flue gases into sulphuric acid and gives rise to corrosion on the ao economizer and the preheater surfaces.

I have discovered that when such coal as has hereinbefore been referred to is burned in the presence of chlorine, the ferrous sulphide becomes decomposed and quickly forms its stable oxides, namely, ferric oxide and sulphur dioxide, the first of which passes to the ash and the second of which passes out of the stack, and that consequently the difficulties in burning coals with high iron sulphur compounds, are obviated. To accomplish the introduction of chlorine during the burning of the coal, two methods may be employed, one of which consists in injecting chlorine gas directly into the burning bed of coal, which may be readily accomplished by passing in the chlorine along with the air supplied for combustion, the chlorine thus finding its way into and through the burning fuel.

Another method, and the one which will be described more at length, contemplates that the necessary chlorine may be introduced into the furnace, by employing suitable chemicals, which are preferably first sprayed upon and distributed through the coal to be burned.

Speaking in general terms, the chemicals used may be said to comprise a suitable deliquescent halogen compound, such for instance, as calcium chloride or magnesium chloride or mixtures of the two, together with suitable catalytic material, such as manganese dioxide, iron oxide, chromium oxide, used two or more of them together, give most satisfactory results.

Preferably the composition which has just been described, may be made up as a liquid and distributed over the coal uniformly by spraying it upon the same, preferably at the mine, so that its quantity and distribution may be properly controlled, and thereafter the coal may be shipped in the usual way to its destination. However, under such circumstances, it is necessary in order to maintain the composition properly distributed and associated with the coal, to provide a fixer, which renders the composition substantially unaffected by exposure, to which the coal may be subjected in transit, thus making certain of the presence of the treating compound in the coal when the coal is burned.

One suitable composition for treating the coal is made up as follows: Percent by weight Calcium chloride--- ---__________.. ___-- 92 Potassium dichromate.---.... __--------- 3 Manganese dioxide ....----_ _______----- 3 Tannic acid-..-- ------------------..___ 2 It has been found that a quantity of the above 65 composition equal to approximately 5% of the sulphur content in the coal is suitable for the purpose.

The reactions when coal is burned with a composition of the general qharacter recited above are as follows: SCalcium chloride (CaCl2) 5 This medium is inherently deliquescent and provides the small amount of water necessary to the process, inasmuch as both chlorine and steam are essential. Calcium chloride decomposes under heat (beginning at a temperature of about 932° F., and terminating at a temperature of about 1652* F.), yielding calcium oxide (CaO) and hydrochloric acid (HC1). Hydrochloric acid alone is not satisfactory for decomposing iron sulphide but must be converted into chlo18 rine. To accomplish this two catalysts are employed.

Catalysts Manganese dioxide (MnOz) and chromium oxide are employed for conversion of the hydroSchloric acid into chlorine. Although, with respect to the formation of chlorine from hydrochloric acid, manganese dioxide and chromium oxide perform as catalytic agents, it has been found that when manganese dioxide and chromium oxide are used together the catalytic conversion of hydrochloric acid into chlorine is accelerated by some six or more times the activity of either one used alone. The chromium oxide Sfunctions as a promoter catalytic agent. Obviously by the use of the terms "manganese dioxide" and "chromium oxide" there will be included as coming within the same scope, chemical substances which when heated decompose to form manganese dioxide and chromium oxide, respectively, where such substances produce the effect of manganese dioxide and chromium oxide in the conversion of chlorine in theburning of the coal as previously described.

In order to affix the calcium chloride and the manganese dioxide and the potassium dichromate to the coal sufficiently well to insure its retention against rain and snow, I add as a fixative, tannic acid (C4HIoOo). I have found that instead of supplying the chromium oxide directly, that when potassium dichromate is substituted, the fixative step is brought into play. This is due to the fact that the potassium dichromate 'and tannic acid react upon one another in the presence of moisture and produce an insoluble floc60 culent tanninbichromate precipitate which affixes the whole to the coal and secondly, that under heat at the proper temperature, the tanninbichromate is oxidized producing the chromium oxide required as a catalyst, as before described.

Without in any way intending to limit myself in any precise way to the description which follows, the general reactions occurring in the burnI: ng fuel bed may be generally stated as follows: . Beginning at a temperature of approximately 932° F., and up to a temperature of approximately 1652° F., the deliquescent calcium chloride is decomposed into calcium oxide and hydrochloric acid. The effectiveness of the hydrochloric acid after Its liberation in decomposing iron sulphide is not limited to its acidic properties, but is tremendously advanced by its catalytic conversion into chlorine, due to the presence of the manganese dioxide and chromium oxide. The iron sulphide is attacked by both hydrochloric acid and chlorine, principally the latter, yielding ferrous chloride and hydrogen sulphide, both of which are volatile and rapidly converted into ferric oxide and sulphur dioxide together with a liberation of hydrochloric acid, which, due to the continued presence of the catalytic agents before mentioned, is converted again and again, with violent rapidity into free chlorine, to repeatedly attack the ferrous sulphide in the manner previously described. The repeated cycles of reactions explains the comparatively small quantities of chemicals employed in treating the coal.

While I have before indicated that there is some latitude in the employment of chemical substances to accomplish the desired result, it should be noted, however, that the chemicals used must be capable of effecting the reactions necessary to the production of chlorine in the burning fuel at a temperature below the fusion temperature of ferrous sulphide, which is approximately 2140* F. It will be obvious that the chemical materials with which the coal is treated may be suitably prepared in the correct proportions and shipped as an article of commerce to be applied to the coal, either at the coal mine or applied to the coal just previous to its use. It has been found advantageous to apply the mixture of materials to the coal at the mine, and where this is done the coal, with the chemical materials applied thereto, is shipped as an article of commerce to the consumer.

This application is a continuation in part of application Serial No. 541,523, filed June 1, 1931, in the name of Lawrence P. Crecelius.

While in the foregoing specification the invention has been described in connection with the treatment and burning of coal, it will be understood that it is intended to include not only coal but coke, lignite, peat and other substances of similar category wherein is involved the problem of the removal of iron sulphur compounds.

Having thus described my invention, what I claim is: 1. A composition of matter for the treatment of coal comprising a chloride which upon heating decomposes below the fusion temperature of iron sulphide, together with manganese dioxide and a substance containing chromium oxide.

2. A composition of matter for the treatment of coal comprising a deliquescent chloride, manganese dioxide and a substance containing chromium oxide.

3. A composition of matter for the treatment of coal comprising a chloride which upon heating decomposes below the fusion temperature of iron sulphide, together with manganese dioxide, potassium dichromate and tannic acid.

4. A composition of matter for the treatment of coal comprising calcium chloride, manganese dioxide and potassium dichromate. 5. A composition of matter for the treatment of coal comprising calcium chloride, manganese dioxide, potassium dichromate and tannic acid.

6. A composition of matter for the treatment of coal comprising a chloride which upon heating decomposes below the fusion temperature of iron sulphide, together with an inorganic oxidizing agent and an oxidation catalyst of the type of manganese dioxide.

7. A composition of matter for the treatment 05 of coal comprising a chloride which upon heating decomposes below the fusion temperature of iron sulphide, together with an oxidation catalyst of the type of manganese dioxide and an oxidizing agent which acts as a promoter catalyst. 8. A composition of matter comprising a deliquescent chloride, potassium dichromate and tannic acid.

9. The method of treating coal for the purposes described, which consists in applying to the coal a composition containing calcium chloride, manganese dioxide, potassium dichromate and tannic acid.

10. The method of treating coal for the purposes described, which consists in applying to the coal a composition containing a chloride which upon heating decomposes at a temperature below the fusion point of iron sulphide, an oxidation catalyst of the type of manganese dioxide and an oxidizing agent which acts as a promoter catalyst.

11. The method which consists in burning in the presence of air, coal containing iron sulfur compounds in such quantity as to normally form objectionable clinker and subjecting the burning coal to the action of a chloride which decomposes at a temperature below the fusion point of iron sulphide, together with a catalytic agent and a promoter catalytic agent whereby by chemical action there is provided a continuous and sufficient supply of chlorine to effect substantial decomposition of the iron sulfur compounds to form a stable oxide of iron and a stable oxide of sulfur.

12. The method which consists in burning in the presence of air, coal containing iron sulfur compounds in such quantity as to normally form objectionable clinker and subjecting the burning coal to the action of calcium chloride, together with a catalytic agent and a promoter catalytic agent, whereby by chemical action there is provided a continuous and sufficient supply of chlorine to effect substantial decomposition of the iron sulfur compounds to form a stable oxide of iron and a stable oxide of sulfur.

13. The process which consists of burning in the presence of air, coal containing iron sulfur compounds in such quantity as to normally form objectionable clinker and subjecting the burning coal to the action of a chloride which decomposes at a temperature below the fusion point of iron sulphide, together with manganese dioxide and chromium oxide to thereby produce a continuous and sufficient supply of chlorine in the burning coal during the combustion thereof to effect a substantial decomposition of iron sulphide into a stable oxide of iron and a stable oxide of sulfur.

14. The process which consists of burning in the presence of air, coal containing iron sulfur compounds in such quantity as to normally form objectionable clinker and subjecting the burning coal to the action of a calcium chloride, together with manganese dioxide and chromium oxide to thereby produce a continuous and sufficient supply of chlorine in the burning coal during the combustion thereof to effect a substantial decomposition of iron sulphide into a stable oxide of iron and a stable oxide of sulfur.

15. The method which consists in burning in the presence of air, coal containing iron sulfur compounds in such quantity as to normally form objectionable clinker and subjecting the burning coal to the action of a chloride which decomposes at a temperature below the fusion point of iron sulphide together with an oxidizing catalyst of the type of manganese dioxide, and an inorganic oxidizing agent whereby by chemical action there is provided a continuous and sufficient supply of chlorine to effect substantial decomposition of the iron sulfur compound to form a stable oxide of iron and a stable oxide of sulfur.

16. The method which consists in burning in the presence of air, coal containing iron sulfur compounds in such quantity as to normally form objectionable clinker and subjecting the burning coal to the action of a calcium chloride, together with an oxidizing catalyst of the type of manganese dioxide, and an inorganic oxidizing agent whereby by chemical action there is provided a continuous and sufficient supply of chlorine to effect substantial decomposition of the iron sulfur compound to form a stable oxide of iron and a stable oxide of sulfur.

17. As an article of commerce, coal upon which there has been deposited a mixture of calcium chloride together with manganese dioxide, potassium dichromate and tannic acid, which causes the mixture to become fixed upon the coal.

18. As an article of commerce, coal upon which there has been deposited a mixture of a deliquescent chloride together with a mixture of an oxidation catalyst of the type of manganese dioxide, an inorganic oxidizing agent and a substance which fixes the said material upon the coal.

19. As an article of commerce, coal upon which there has been deposited a mixture of a deliquescent chloride together with a mixture of an oxidation catalyst of the type of manganese dioxide, an inorganic oxidizing agent and tannic acid.

20. As an article of commerce, coal upon which there has been deposited a mixture of a deliquescent chloride together with a catalyst and a promoter catalyst and a substance which fixes the chloride and catalytic material upon the coal.

LAWRENCE P. CRECELIUS.