EP0060354B1 - Method of treating coal to remove sulphur and ash - Google Patents
Method of treating coal to remove sulphur and ash Download PDFInfo
- Publication number
- EP0060354B1 EP0060354B1 EP19810301043 EP81301043A EP0060354B1 EP 0060354 B1 EP0060354 B1 EP 0060354B1 EP 19810301043 EP19810301043 EP 19810301043 EP 81301043 A EP81301043 A EP 81301043A EP 0060354 B1 EP0060354 B1 EP 0060354B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- coal
- mixture
- sulphur
- ash
- water
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
- C10L9/00—Treating solid fuels to improve their combustion
- C10L9/02—Treating solid fuels to improve their combustion by chemical means
Definitions
- High sulfur coal i.e., about 3%, exists in unmined form and also in the form of already mined coal that has been discarded, i.e., refuse coal.
- Refuse coal usually consists of fines which result from the processing of coal. More particularly, when coal is mined it is normally crushed and washed and the washings are generally dumped and used as land fill or dumped into a lake or stream. In the latter case, over a period of time, the pond or stream becomes almost completely filled with the finely powdered coal. Not only is a significant waste of coal but it is injurious to the lakes and streams. Many lakes have become “dead” lakes dueto this disposal of waste coal. The ash content of such refuse coal, i.e., above 20% by weight, also makes it economically unattractive to attempt to utilize it.
- a method of treating pulverised coal to remove sulphur comprises adding pickle liquor to the coal, subsequent adding to the coal of a mixture of water with chlorine gas added thereto, the amount of pickle liquor and chlorine gas being sufficient to provide a mixture having a pH of less than about 3, and physically separating the coal from the mixture.
- the present invention is applicable to high sulphur, high ash refuse or virgin coal.
- coal crushed to about 1/4 by 0 size (that is 1/4 inch down to 325 Tyler mesh in size6.35 to 0.04x10- 2 m) is first treated with spent pickle liquor. Thereafter it is subjected to a strong acidic oxidizing agent. More particularly, the acidified coal mixture is treated with a mixture of chlorine gas dissolved in water. Thereafter coal and ash are separated through the use of water and gravity. Following this, the acid solution remaining is treated with lime and the precipitate which contains various sulfur compounds is discarded. These sulfur compounds exists in such a state that they are not injurious to our environment when discarded and in fact have a beneficial effect on dead lakes.
- a method of removing ash and sulphur from coal wherein sulphur is present comprises forming a coal and water mixture from pulverized coal and a minor amount of water, treating the mixture with chlorine gas in an amount sufficient to convert the sulphur to a sulphur containing acid(s), physically separating ash and coal from the mixture, treating the remaining mixture containing the sulphur containing acid(s) with lime whereby the sulphur is precipitated as calcium salts, and physically separating the calcium salts.
- the process of this invention can be effectively practised on any high sulphur content coal.
- refuse coal that at the present time has no utility.
- the refuse coal contains less than about 1% sulphur, has about 5-6% ash, has about 14,000-14,500 British thermal unit (btu) per pound (3:26-3.37x104 J/kg), and is processed into easily handled pellets.
- btu British thermal unit
- the refuse coal typically contains 2-3% sulphur, 25-30% ash and has a btu per pound content of only 7,500 (1.74x10 4 J/Kg).
- Refuse coal is produced as the result of normal coal mining operations and exists as a result of coal being crushed and washed. Typically it is 1/4 by 0 and discarded as land fill or thrown into a pond, lake or stream. In some instances as much as 20% by weight of the mined coal ends up in the form of heretofore unusable refuse coal.
- the pulverized coal is first mixed with spent pickle liquor.
- a pickling acid to remove scale, rust, etc. Most frequently 60° Be' sulfuric acid is employed and this is the preferred form for use in the present invention although other acid pickle liquors may be employed.
- the spent pickle liquor comprising the acid and various iron compounds such as Fe 2 (SO 4 ) 31 FeS0 4 .7H 2 0 and other contaminants must be disposed of. Obviously, the disposal of such a liquid poses a significant problem from an environmental standpoint.
- the amount of spent pickle liquor mixed with the pulverized coal is somewhat dependent on the sulfur content of the coal. Usually though 2% pickle liquor based on the weight of the coal is sufficient.
- the mixture is introduced into any suitable type of reactor mixture and mixed with about 20% by weight of water.
- the water temperature and temperature of the mixture is 80-90°F (26.7-37.2°C). This may require suitable heating or cooling means of conventional design.
- chlorine gas Into the reactor mixture is introduced chlorine gas.
- the amount of chlorine required is an amount sufficient to provide a mixture having a pH of about 3 or less.
- the chlorine gas provides hydrochloric acid, hypochlorous acid and nascent oxygen.
- iron disulphide iron pyrite
- the ash and coal that are present can be mechanically separated from each other and from the acid solution.
- One convenient way for doing so consists of introducing the entire mixture into a conically shaped separator of conventional design, where provision is made at the bottom for introducing water. At the top a weir is provided such that material at the surface of the mixture will be transferred out of the separator and into a discharge conduit. The denser heavier coal particles fall to the bottom and are discharged through an outlet. The coal is then dried and preferably pelletized.
- a sufficient amount of lime to precipitate most of the sulfur as calcium salts i.e., CaS0 3 , CaS, CaS0 4 or other salts of calcium containing sulfur.
- the amount of lime required is that amount which is required to provide a neutral or nearly neutral pH.
- Such precipitated salts are thereafter separated and preferably used as fill in coal slurry ponds. If the ponds are not totally filled but if a sufficient amount of the precipitate is added over a relatively short period of time the pond is once again capable of supporting life.
- the coal so recovered has less than 6% ash, less than 1% sulfur and a btu content of about 14,000 per pound (3.26x 10 4 J/kg).
- the economics of the process are such that refuse coal may be economically reclaimed to provide an excellent energy source.
- a minor amount of water preferably in the form of steam.
- the water added is preferably an amount equal to about 10-20 % by weight of the coal.
- chlorine gas is added to the mixture.
- the chlorine gas is not dissolved in water nor is pickle liquor added to the mixture.
- the amount of water required is reduced.
- the mixture after treatment with the chlorine gas is subjected to the separation step and thereafter to the neutralization step.
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Combustion & Propulsion (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Organic Chemistry (AREA)
- Solid Fuels And Fuel-Associated Substances (AREA)
- Processing Of Solid Wastes (AREA)
Description
- There exists in the United States a large quantity of coal which cannot be economically used as a fuel because of its high sulfur content. Environmental laws are such that it is enconomi- cally unfeasible to burn a high sulfur content coal because of the expensive antipollution equipment required.
- High sulfur coal, i.e., about 3%, exists in unmined form and also in the form of already mined coal that has been discarded, i.e., refuse coal. Refuse coal usually consists of fines which result from the processing of coal. More particularly, when coal is mined it is normally crushed and washed and the washings are generally dumped and used as land fill or dumped into a lake or stream. In the latter case, over a period of time, the pond or stream becomes almost completely filled with the finely powdered coal. Not only is this is a significant waste of coal but it is injurious to the lakes and streams. Many lakes have become "dead" lakes dueto this disposal of waste coal. The ash content of such refuse coal, i.e., above 20% by weight, also makes it economically unattractive to attempt to utilize it.
- There also exist in the United States substantial. deposits of unmined or virgin coal having a high sulfur content. In order to burn such coal in industry it would be necessary to spend substantial amounts of money for air pollution equipment. Therefore, this high sulfur content coal is not being mined.
- The need to effectively utilize energy while at the same time protecting our environment faces many other industries as well, the steel industry being another example. The disposal of waste materials from steel making processes in an economically feasible, environmentally suitable manner is frequently a significant problem. For example, in the processing of steel an acid solution (pickle liquor) is used to treat the product. The resultant solution consisting of an acid, iron compounds, contaminants, etc. (collectively referred to hereinafter as spent pickle liquor) must be disposed of.
- In accordance with one aspect of the invention, a method of treating pulverised coal to remove sulphur comprises adding pickle liquor to the coal, subsequent adding to the coal of a mixture of water with chlorine gas added thereto, the amount of pickle liquor and chlorine gas being sufficient to provide a mixture having a pH of less than about 3, and physically separating the coal from the mixture.
- The present invention is applicable to high sulphur, high ash refuse or virgin coal. In one form of the present process, coal, crushed to about 1/4 by 0 size (that is 1/4 inch down to 325 Tyler mesh in size6.35 to 0.04x10-2m) is first treated with spent pickle liquor. Thereafter it is subjected to a strong acidic oxidizing agent. More particularly, the acidified coal mixture is treated with a mixture of chlorine gas dissolved in water. Thereafter coal and ash are separated through the use of water and gravity. Following this, the acid solution remaining is treated with lime and the precipitate which contains various sulfur compounds is discarded. These sulfur compounds exists in such a state that they are not injurious to our environment when discarded and in fact have a beneficial effect on dead lakes.
- In accordance with another aspect of the invention, a method of removing ash and sulphur from coal wherein sulphur is present comprises forming a coal and water mixture from pulverized coal and a minor amount of water, treating the mixture with chlorine gas in an amount sufficient to convert the sulphur to a sulphur containing acid(s), physically separating ash and coal from the mixture, treating the remaining mixture containing the sulphur containing acid(s) with lime whereby the sulphur is precipitated as calcium salts, and physically separating the calcium salts.
- In this alternative form of the present invention only a minor amount of water is added to the pulverized coal, preferably in the form of steam, and the mixture is treated with chlorine gas.
- The process of this invention can be effectively practised on any high sulphur content coal. In its most useful application it is practised on refuse coal that at the present time has no utility. After treatment the refuse coal contains less than about 1% sulphur, has about 5-6% ash, has about 14,000-14,500 British thermal unit (btu) per pound (3:26-3.37x104 J/kg), and is processed into easily handled pellets. In contrast, before processing the refuse coal typically contains 2-3% sulphur, 25-30% ash and has a btu per pound content of only 7,500 (1.74x104 J/Kg).
- Refuse coal is produced as the result of normal coal mining operations and exists as a result of coal being crushed and washed. Typically it is 1/4 by 0 and discarded as land fill or thrown into a pond, lake or stream. In some instances as much as 20% by weight of the mined coal ends up in the form of heretofore unusable refuse coal.
- Various areas of the United States contain large deposits of coal which are basically unusable because of the high sulphur content of the coal. The present process is applicable also to such coal. The only modification required is to pulverize the coal so that it is about 1/4 by 0 as in the case of refuse coal..
- In the practice of one embodiment of the process the pulverized coal is first mixed with spent pickle liquor. In the manufacture of iron or steel it is customary to use a pickling acid to remove scale, rust, etc. Most frequently 60° Be' sulfuric acid is employed and this is the preferred form for use in the present invention although other acid pickle liquors may be employed. After use, the spent pickle liquor comprising the acid and various iron compounds such as Fe2(SO4)31 FeS04.7H20 and other contaminants must be disposed of. Obviously, the disposal of such a liquid poses a significant problem from an environmental standpoint.
- For some unknown reason the use of spent pickle liquor produces superior results than if the acid itself is used. While it is not completely understood, it is believed that the iron salts present in the spent pickle liquor have a significant effect on the reaction rate.
- If only uncontaminated H2S04 is used, the final results in many cases in terms of sulfur removal are inferior and the speed of the reaction is decreased. Moreover, the ability to convert a material that poses such an environmental risk to a safe, useful material able to benefit the environment is an advantage not to be taken lightly. While it is preferred to use spent pickle liquor the acid in unused form may be utilized recognizing, of course, that under some conditions inferior results may be obtained.
- The amount of spent pickle liquor mixed with the pulverized coal is somewhat dependent on the sulfur content of the coal. Usually though 2% pickle liquor based on the weight of the coal is sufficient.
- It is important to allow the pickle liquor to contact the coal for a brief period of time prior to further processing. In practice 5--10 minutes has been found to be satisfactory. Thereafter, the mixture is introduced into any suitable type of reactor mixture and mixed with about 20% by weight of water. Preferably the water temperature and temperature of the mixture is 80-90°F (26.7-37.2°C). This may require suitable heating or cooling means of conventional design. Into the reactor mixture is introduced chlorine gas. The amount of chlorine required is an amount sufficient to provide a mixture having a pH of about 3 or less. When mixed with the water the chlorine gas provides hydrochloric acid, hypochlorous acid and nascent oxygen.
- While it is not completely understood, it is believed that the iron disulphide (iron pyrite) which is present in the coal and which forms the major sulphur containing material is converted into the following iron and sulphur compounds through the following reactions:
- To the liquid and water material overflowing the separation is added a sufficient amount of lime to precipitate most of the sulfur as calcium salts, i.e., CaS03, CaS, CaS04 or other salts of calcium containing sulfur. The amount of lime required is that amount which is required to provide a neutral or nearly neutral pH. Such precipitated salts are thereafter separated and preferably used as fill in coal slurry ponds. If the ponds are not totally filled but if a sufficient amount of the precipitate is added over a relatively short period of time the pond is once again capable of supporting life.
- The coal so recovered has less than 6% ash, less than 1% sulfur and a btu content of about 14,000 per pound (3.26x 104 J/kg). The economics of the process are such that refuse coal may be economically reclaimed to provide an excellent energy source.
- In the alternative form of the present invention, to the pulverized coal is added a minor amount of water, preferably in the form of steam. The water added is preferably an amount equal to about 10-20 % by weight of the coal. Thereafter, to the mixture is added chlorine gas. Unlike the previous embodiment the chlorine gas is not dissolved in water nor is pickle liquor added to the mixture. Also, the amount of water required is reduced. As in the previous embodiment, the mixture after treatment with the chlorine gas is subjected to the separation step and thereafter to the neutralization step.
Claims (10)
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP19810301043 EP0060354B1 (en) | 1981-03-12 | 1981-03-12 | Method of treating coal to remove sulphur and ash |
DE8181301043T DE3171535D1 (en) | 1981-03-12 | 1981-03-12 | Method of treating coal to remove sulphur and ash |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP19810301043 EP0060354B1 (en) | 1981-03-12 | 1981-03-12 | Method of treating coal to remove sulphur and ash |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0060354A1 EP0060354A1 (en) | 1982-09-22 |
EP0060354B1 true EP0060354B1 (en) | 1985-07-31 |
Family
ID=8188236
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP19810301043 Expired EP0060354B1 (en) | 1981-03-12 | 1981-03-12 | Method of treating coal to remove sulphur and ash |
Country Status (2)
Country | Link |
---|---|
EP (1) | EP0060354B1 (en) |
DE (1) | DE3171535D1 (en) |
Families Citing this family (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6729248B2 (en) | 2000-06-26 | 2004-05-04 | Ada Environmental Solutions, Llc | Low sulfur coal additive for improved furnace operation |
US8439989B2 (en) * | 2000-06-26 | 2013-05-14 | ADA-ES, Inc. | Additives for mercury oxidation in coal-fired power plants |
CN101497464B (en) * | 2009-01-19 | 2011-01-05 | 中国科学院山西煤炭化学研究所 | Method for processing pickle liquor or electroplating waste liquor |
CN102295969B (en) * | 2011-07-27 | 2013-09-18 | 北京科技大学 | Method for simultaneous removal of sulfur and arsenic in sulfur coal with high removal rate and little time |
Family Cites Families (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE670964C (en) * | 1933-09-15 | 1939-01-28 | Erdoel Akt Ges Deutsche | Process for ash removal from coke of mineral coals |
US3998604A (en) * | 1974-09-23 | 1976-12-21 | International Oils Exploration N.L. | Demineralization of brown coal |
GB1454933A (en) * | 1974-10-12 | 1976-11-10 | Tioxide Group Ltd | Process for the treatment of acidic waste liquid containing dissolved salts |
-
1981
- 1981-03-12 EP EP19810301043 patent/EP0060354B1/en not_active Expired
- 1981-03-12 DE DE8181301043T patent/DE3171535D1/en not_active Expired
Also Published As
Publication number | Publication date |
---|---|
EP0060354A1 (en) | 1982-09-22 |
DE3171535D1 (en) | 1985-09-05 |
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