CA1056322A - Process for reducing the sulphur content of coal and coal char and the ignition temperature of coal char - Google Patents
Process for reducing the sulphur content of coal and coal char and the ignition temperature of coal charInfo
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- CA1056322A CA1056322A CA214,068A CA214068A CA1056322A CA 1056322 A CA1056322 A CA 1056322A CA 214068 A CA214068 A CA 214068A CA 1056322 A CA1056322 A CA 1056322A
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- char
- coal
- bath
- temperature
- caustic
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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
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- 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)
- Carbon And Carbon Compounds (AREA)
- Production Of Liquid Hydrocarbon Mixture For Refining Petroleum (AREA)
Abstract
ABSTRACT
Coal and like carbonaceous materials are converted to char by heating with restricted oxygen access at a temperature not exceeding about 870°C. (1600°F.) and the resultant char is desulphurized by treatment with a hot liquid alkali, preferably with a molten caustic alkali such as sodium or potassium hydroxide or a mixture thereof at a temperature in the range 260-400°C. (500-750°F.) for a residence time of about 2 to about 30 minutes, whereafter the desulphurized char is separated form the alkali and freed from the latter as by washing with water.
Coal and like carbonaceous materials are converted to char by heating with restricted oxygen access at a temperature not exceeding about 870°C. (1600°F.) and the resultant char is desulphurized by treatment with a hot liquid alkali, preferably with a molten caustic alkali such as sodium or potassium hydroxide or a mixture thereof at a temperature in the range 260-400°C. (500-750°F.) for a residence time of about 2 to about 30 minutes, whereafter the desulphurized char is separated form the alkali and freed from the latter as by washing with water.
Description
, ~
~os63ZZ-This invention concerns a process for reducing the sulphur content of coal and coal char and the ignition temperature of coal char. In this Specification "coal" is to be understood to include all forms of coal and similar carbonaceous materials 'such as, for instance, peat, lignite, bitumen and tar, that may be converted to a char by heating with restricted access of oxygen.
Commercial desulphurization techniques only remove a portion of the sulphur present in coal or in coal chars. This is inadequate to comply with air purity standards which limit the amount of sulphur dioxide that may be produced by the use of coalsg chars, and other carbonaceous materials when used as a fuel. The need for a relatively sulphur-~ree char has therefore become very important, especially in view of dwindling supplies of oil and natural gas and abundant supplies of coal.
c .
One known method of desulphurizing coal consists o~ crushing and grinding the coal into a fine powder that is then introduced into a fluid medium to allow the sulphur in the form of FeS2 (pyrite) to form a separate layer that is mechanicaily removed from the coal. This technique, however~ does not remove FeS2 that remains embedded in the uncrushed coal, nor can it remove ~ any o~ the sulphur present in otherinorganic compounds and in i organic compounds.
Another method is to treat coal with hydrogen gas so as to leach out the sulphur ln the form of hydrogen sulphide gas. This 'I ' method generally works well with coal but cannot be applied `' ' ' -successfully to char because when coal is converted into char, i chemical reactions occur between the sulphur and the inorganic and organic compounds in the coal to "fix" the sulphur in the `~
char and ron~cr-ff it more resistant to reaction with hydrogen.
.
, ; ' , -. , ' .
~0563'~Z
Hot (molten) caustic alkali has also been used to leach sulphur from finely-divided coal. This procedure, however, removes only a rela-tively small amount of the sulphur from coal and would not appear to be suitable for desulphurising char owing to the "fixed" condition of the sulphur therein. Furthermore, this method requires the coal to be in a semi-fluid or plastic condition for effective leaching: char does not become semi-fluid or plastic and would therefore seem to be unsuitable for such de-sulphurizing procedure.
It has, however, now been discovered that greatly improved desulphurization may be achieved by converting coal into char by heating at temperatures which do not exceed about 870C., and thereafter treating the char in a hot alkali, preferably caustic alkali, system. It is surprising that char should desulphurize in a hot alkali system in view of the fact that char does not attain the fluid condition belièved to be necessary during the desulphurization of coal with a hot caustic alkali system.
Moreover, the sulphur reduction attainable by this procedure is greater than that attained by the prior procedure of treating coal with an equivalent alkali system. The procedure also has the advantage that the char ignition temperature is substantially reduced. This is desirable in-asmuch as less heat or energy is required to effect ignition of such chars.
According to the present invention there is provided a process for desulfurizing coal char said process comprising adding said char to molten caustic to form a mixture such that the ratio of molten caustic to char in said mixture is at least about three to one, the residence time of said char in said mixture is about two minutes to about thirty minutes and is sufficient to lower the sulfur content of said char.
In another aspect, there is provided a process for producing low sulfur char from coal comprising converting said coal to char by heating at a temperature no greater than about 870C and adding said char to a bath of molten caustic, said bath having a ratio of molten caustic to char of at least about three to one, for a residence time of from about two minutes to about thirty minutes, sufficient to lower the sulfur content of said char.
~ y ~0563Z5:
Preferably, said coal is converted tosaid char at a temperature of about 540C to about 595C said molten caustic is formed from a mixture of about equal parts of sodium hydroxide and potassium hydroxide, said bath is maintained at a temperature of about 260C to about 400C said residence time is about ten minutes, said char is removed from said bath and washed sufficiently to cause said char to be substantially free of said caustic, and the sulfur content of said char is reduced to a value no greater than about 0.7 percent by weight on a dry basis.
In yet a further aspect, there is provided a process for pro-ducing a low sulfur, low ash, lowignition temperature char from coal, said process comprising converting said coal to char by heating at a temperature no greater than about 870C and adding said char to a bath of molten caustic, said bath having a ratio of molten caustic to char of at least about three to one, for a residence time of from about two minutes to about thirty minutes, sufficient to lower the sulfur content of said char to less than that of said coal, sufficient to lower the ash content of said char to l~ss than that of said coal, and sufficient to lower the ignition temperature of said char so that said char ignition temperature is no higher than about the ignition temperature of said coal.
In practicing the procedure indicated, that constitutes the desulphurising of the present invention, coal is first converted into char by any suitable method that does not involve charring temperatures exceeding about 870C. Chars produced at temperatures between about 540C and 870C
are capable of having between ab~ut 50% to about 99%of their sulphur removed, 3a -` ~0563ZZ
with the optimum desulphurization occurring when the coal has been charred at temperatures in the range 540C to 595 C. The 870 C~ figure represents an upper temperature limit for practical operatlon since although coals that are charred at temperatures above 870 C. give a char that can be desulphurized to an extent by the alkali system treatment, the degree of desulphurization attained will not be as great as when the charring temperatures below 870C. are employed. However, a charring temperature of not more than about 730C. is preferred if loss of desulphurizing capability is to be avoided.
The char, follo~ng its production as aforesaid, is then introduced into an alkali system, such as for example, a bath of hot,molten7 caustic alkali. The char need not be specially treated or prepared before this treatmcnt and may be in~oduced into the alkali system in its as-produced condition.
-1. The materials used to form the alkali system may be any - caustic alkali, such as for example, sodium hydroxide (NaOH) or potassium hydroxide (KOH), or an alkali such as calcium oxide, -sodium carbonate, or any other strongly alkaline màterial. The system may comprise a mixture of two or more al~alis.
Alkaline materials that are solids at ambient temperatures need to be heated to a temperature above their melting point to ~orm and maintain the liquid alkali system. In preferred procedures the alkali system comprdses a mixture of equal amounts by weight of sodium hydroxide and potassium hydroxide that is heated to and maintained at a temperature between about 260C.
and about 400C.
.
The weight ratio of alkali system to char should be maintained at a level that will effect-satisfactory desulphurization. In -~~ 30 ~referred procedures, this involves the use of at least three ~ ~ 4 . - .
:, - . . - . - : ' , : ' . .
~0563Z2 parts of a 50/50 NaOH-KOH mixture to one part of char.
When the c~ar has been introduced into the alkali system, it is preferably intimately mixed therewith by means - of a motor-driven stirrer or other equivalent means which will provide a thorough contact between the char with the alkali system. An inert fluid, such as nitrogen gas, may be used to purge the char alkali system mixture to eliminate ~` oxygen and to prevent the possibility of any reactionstherewith.
The elimination of oxygen from the bath, however, is not essential for satisfactory desulphurization.
The period of intimate contact between the char and the alkali system is referred to as the "residence time" and should be from about two to about forty minutes. About thirty minutes is preferred for maximum desulphurization. After the prescribed residence time~ the char is allowed to rise to the surface of the y alkali system where it is decanted or skimmed off by conventional flotation separation means. The char is preferably thereafter washed with water to remove the alkali materials and until the pH of the washing water shows no change after washing the char.
Chars desulphurized by this procedure have been found to have lower ignition temperatures than chars which have not been so desulphurized. The lowering of the ignition temperature of char or coal by the addition of an alkali metal thereto is known, ~, but the washed chars produced by the preferred procedure do not ;1~ have added alkali metals and would not, therefore, be expected i to have lower ignition temperatures. This is a surp~ising finding and a significant advantage in the use of such chars inasmuch as the presence of alkali metals in the char is detri=ental to furnaces in which the chars are used as fuels.
i'' " ' ~1 ` .
~, .
: ~ :
j 10563ZZ
EXAMPLE I
To demonstrate the effect of charring temperatures upon desulphurization of char, s0ven specimens of char, each weighing 25 grams and having a -60 mesh particle size, were prepared from Hamilton coal at temperatures ranging from 540C. to 980C.
Hamilton coal is obtained from Western Kentucky, U.S.A., and is characterized by being bituminous and highly volatile. Alkali systems for treating each individual char specimen were prepared in stainless steel beakers. With one exception noted below, each alkali system was a mixture of 100 grams of sodium hydrQxide and 100 grams of potassium hydroxide melted by standing its beaker on a-hot plate which was set to provide a system temperature of 400 C. A bimetallic thermometer was used to determine the temperature of the liquid alkali systems. Nitrogen gas was bubbled through each system to purge any oxygen present therein.
Each char specimen was introduced into its alkali system ~ t~4~e c and the resulting mi~c~u~c were stirred for thirty minutes while being held at a temperature of 400 C. At the conclusion of this residence time, the reactions were stopped by the addition of water to each mixture to form an aqueous solu+ion of the cautic -~alkalis. The desulphurized char samples were removed from these solutions by filtration and washed with water until no further change in the pH of the wash water was noted. Each char specimen was air-dried and analyzed for its sulphur content which was compared with its (previously ascertained) sulphur content before treatment by the alkali system. The results were as follows:
~ .
-~, - .
.
, , ' - -, Charring Tem- Sulphur content Sulphur content Percentage perature of of the Char of the char of sulphur the specimen before treatment after treatment removal by (weight o/o) '' (weight !) treatment 540C . 1.88 o . og* 95.2 540C. ` 1.81 0.01 99.5 - ` 650C. 1.88 - 0.11 94.2 760C . ~ 79 0.25 ,86. o 870C . 1.73 0.85 50.9 870C . 1.82 0.76 58.2 - 980C. 1.75 1.08 38.4 `
* For this particular specimen, the alkali system was a mixture -of 50 grams of sodium hydroxide and 50 grams of potassium`
hydroxide.
~, ' ; ~:
.
Z
: ~- : . , , ~ . ' '' ' , , EXAMPLE II
To demonstrate the effect of residence time upon desulphurization, five 25-gram specimens of char were ~; manufactured and desulphurized as described in Example I
,~ ' ~X C ef >t hereinabove,-ux~p~ that in each case the char was manufactured at a temperature of 540 C. and the residence time was varied --from two minutes to thirty minutes. The results, expressed in terms of weight percentage of the total desulphurized char sample weight in each case, and compared with a sixth, control, sample that was not treated with the alkali system (shown below as a Residence Time of O min.) were as follows:
,. . .::
Residence Water Ash Total Pyrite Other Sulphur ; TimeContent Content Sulphur Content Inor- contain-Content (FeS2) ganic ing Or-Sulphur ganic Compounds O min.1.49 32.91 2.85 o.63 0.13 1 40
~os63ZZ-This invention concerns a process for reducing the sulphur content of coal and coal char and the ignition temperature of coal char. In this Specification "coal" is to be understood to include all forms of coal and similar carbonaceous materials 'such as, for instance, peat, lignite, bitumen and tar, that may be converted to a char by heating with restricted access of oxygen.
Commercial desulphurization techniques only remove a portion of the sulphur present in coal or in coal chars. This is inadequate to comply with air purity standards which limit the amount of sulphur dioxide that may be produced by the use of coalsg chars, and other carbonaceous materials when used as a fuel. The need for a relatively sulphur-~ree char has therefore become very important, especially in view of dwindling supplies of oil and natural gas and abundant supplies of coal.
c .
One known method of desulphurizing coal consists o~ crushing and grinding the coal into a fine powder that is then introduced into a fluid medium to allow the sulphur in the form of FeS2 (pyrite) to form a separate layer that is mechanicaily removed from the coal. This technique, however~ does not remove FeS2 that remains embedded in the uncrushed coal, nor can it remove ~ any o~ the sulphur present in otherinorganic compounds and in i organic compounds.
Another method is to treat coal with hydrogen gas so as to leach out the sulphur ln the form of hydrogen sulphide gas. This 'I ' method generally works well with coal but cannot be applied `' ' ' -successfully to char because when coal is converted into char, i chemical reactions occur between the sulphur and the inorganic and organic compounds in the coal to "fix" the sulphur in the `~
char and ron~cr-ff it more resistant to reaction with hydrogen.
.
, ; ' , -. , ' .
~0563'~Z
Hot (molten) caustic alkali has also been used to leach sulphur from finely-divided coal. This procedure, however, removes only a rela-tively small amount of the sulphur from coal and would not appear to be suitable for desulphurising char owing to the "fixed" condition of the sulphur therein. Furthermore, this method requires the coal to be in a semi-fluid or plastic condition for effective leaching: char does not become semi-fluid or plastic and would therefore seem to be unsuitable for such de-sulphurizing procedure.
It has, however, now been discovered that greatly improved desulphurization may be achieved by converting coal into char by heating at temperatures which do not exceed about 870C., and thereafter treating the char in a hot alkali, preferably caustic alkali, system. It is surprising that char should desulphurize in a hot alkali system in view of the fact that char does not attain the fluid condition belièved to be necessary during the desulphurization of coal with a hot caustic alkali system.
Moreover, the sulphur reduction attainable by this procedure is greater than that attained by the prior procedure of treating coal with an equivalent alkali system. The procedure also has the advantage that the char ignition temperature is substantially reduced. This is desirable in-asmuch as less heat or energy is required to effect ignition of such chars.
According to the present invention there is provided a process for desulfurizing coal char said process comprising adding said char to molten caustic to form a mixture such that the ratio of molten caustic to char in said mixture is at least about three to one, the residence time of said char in said mixture is about two minutes to about thirty minutes and is sufficient to lower the sulfur content of said char.
In another aspect, there is provided a process for producing low sulfur char from coal comprising converting said coal to char by heating at a temperature no greater than about 870C and adding said char to a bath of molten caustic, said bath having a ratio of molten caustic to char of at least about three to one, for a residence time of from about two minutes to about thirty minutes, sufficient to lower the sulfur content of said char.
~ y ~0563Z5:
Preferably, said coal is converted tosaid char at a temperature of about 540C to about 595C said molten caustic is formed from a mixture of about equal parts of sodium hydroxide and potassium hydroxide, said bath is maintained at a temperature of about 260C to about 400C said residence time is about ten minutes, said char is removed from said bath and washed sufficiently to cause said char to be substantially free of said caustic, and the sulfur content of said char is reduced to a value no greater than about 0.7 percent by weight on a dry basis.
In yet a further aspect, there is provided a process for pro-ducing a low sulfur, low ash, lowignition temperature char from coal, said process comprising converting said coal to char by heating at a temperature no greater than about 870C and adding said char to a bath of molten caustic, said bath having a ratio of molten caustic to char of at least about three to one, for a residence time of from about two minutes to about thirty minutes, sufficient to lower the sulfur content of said char to less than that of said coal, sufficient to lower the ash content of said char to l~ss than that of said coal, and sufficient to lower the ignition temperature of said char so that said char ignition temperature is no higher than about the ignition temperature of said coal.
In practicing the procedure indicated, that constitutes the desulphurising of the present invention, coal is first converted into char by any suitable method that does not involve charring temperatures exceeding about 870C. Chars produced at temperatures between about 540C and 870C
are capable of having between ab~ut 50% to about 99%of their sulphur removed, 3a -` ~0563ZZ
with the optimum desulphurization occurring when the coal has been charred at temperatures in the range 540C to 595 C. The 870 C~ figure represents an upper temperature limit for practical operatlon since although coals that are charred at temperatures above 870 C. give a char that can be desulphurized to an extent by the alkali system treatment, the degree of desulphurization attained will not be as great as when the charring temperatures below 870C. are employed. However, a charring temperature of not more than about 730C. is preferred if loss of desulphurizing capability is to be avoided.
The char, follo~ng its production as aforesaid, is then introduced into an alkali system, such as for example, a bath of hot,molten7 caustic alkali. The char need not be specially treated or prepared before this treatmcnt and may be in~oduced into the alkali system in its as-produced condition.
-1. The materials used to form the alkali system may be any - caustic alkali, such as for example, sodium hydroxide (NaOH) or potassium hydroxide (KOH), or an alkali such as calcium oxide, -sodium carbonate, or any other strongly alkaline màterial. The system may comprise a mixture of two or more al~alis.
Alkaline materials that are solids at ambient temperatures need to be heated to a temperature above their melting point to ~orm and maintain the liquid alkali system. In preferred procedures the alkali system comprdses a mixture of equal amounts by weight of sodium hydroxide and potassium hydroxide that is heated to and maintained at a temperature between about 260C.
and about 400C.
.
The weight ratio of alkali system to char should be maintained at a level that will effect-satisfactory desulphurization. In -~~ 30 ~referred procedures, this involves the use of at least three ~ ~ 4 . - .
:, - . . - . - : ' , : ' . .
~0563Z2 parts of a 50/50 NaOH-KOH mixture to one part of char.
When the c~ar has been introduced into the alkali system, it is preferably intimately mixed therewith by means - of a motor-driven stirrer or other equivalent means which will provide a thorough contact between the char with the alkali system. An inert fluid, such as nitrogen gas, may be used to purge the char alkali system mixture to eliminate ~` oxygen and to prevent the possibility of any reactionstherewith.
The elimination of oxygen from the bath, however, is not essential for satisfactory desulphurization.
The period of intimate contact between the char and the alkali system is referred to as the "residence time" and should be from about two to about forty minutes. About thirty minutes is preferred for maximum desulphurization. After the prescribed residence time~ the char is allowed to rise to the surface of the y alkali system where it is decanted or skimmed off by conventional flotation separation means. The char is preferably thereafter washed with water to remove the alkali materials and until the pH of the washing water shows no change after washing the char.
Chars desulphurized by this procedure have been found to have lower ignition temperatures than chars which have not been so desulphurized. The lowering of the ignition temperature of char or coal by the addition of an alkali metal thereto is known, ~, but the washed chars produced by the preferred procedure do not ;1~ have added alkali metals and would not, therefore, be expected i to have lower ignition temperatures. This is a surp~ising finding and a significant advantage in the use of such chars inasmuch as the presence of alkali metals in the char is detri=ental to furnaces in which the chars are used as fuels.
i'' " ' ~1 ` .
~, .
: ~ :
j 10563ZZ
EXAMPLE I
To demonstrate the effect of charring temperatures upon desulphurization of char, s0ven specimens of char, each weighing 25 grams and having a -60 mesh particle size, were prepared from Hamilton coal at temperatures ranging from 540C. to 980C.
Hamilton coal is obtained from Western Kentucky, U.S.A., and is characterized by being bituminous and highly volatile. Alkali systems for treating each individual char specimen were prepared in stainless steel beakers. With one exception noted below, each alkali system was a mixture of 100 grams of sodium hydrQxide and 100 grams of potassium hydroxide melted by standing its beaker on a-hot plate which was set to provide a system temperature of 400 C. A bimetallic thermometer was used to determine the temperature of the liquid alkali systems. Nitrogen gas was bubbled through each system to purge any oxygen present therein.
Each char specimen was introduced into its alkali system ~ t~4~e c and the resulting mi~c~u~c were stirred for thirty minutes while being held at a temperature of 400 C. At the conclusion of this residence time, the reactions were stopped by the addition of water to each mixture to form an aqueous solu+ion of the cautic -~alkalis. The desulphurized char samples were removed from these solutions by filtration and washed with water until no further change in the pH of the wash water was noted. Each char specimen was air-dried and analyzed for its sulphur content which was compared with its (previously ascertained) sulphur content before treatment by the alkali system. The results were as follows:
~ .
-~, - .
.
, , ' - -, Charring Tem- Sulphur content Sulphur content Percentage perature of of the Char of the char of sulphur the specimen before treatment after treatment removal by (weight o/o) '' (weight !) treatment 540C . 1.88 o . og* 95.2 540C. ` 1.81 0.01 99.5 - ` 650C. 1.88 - 0.11 94.2 760C . ~ 79 0.25 ,86. o 870C . 1.73 0.85 50.9 870C . 1.82 0.76 58.2 - 980C. 1.75 1.08 38.4 `
* For this particular specimen, the alkali system was a mixture -of 50 grams of sodium hydroxide and 50 grams of potassium`
hydroxide.
~, ' ; ~:
.
Z
: ~- : . , , ~ . ' '' ' , , EXAMPLE II
To demonstrate the effect of residence time upon desulphurization, five 25-gram specimens of char were ~; manufactured and desulphurized as described in Example I
,~ ' ~X C ef >t hereinabove,-ux~p~ that in each case the char was manufactured at a temperature of 540 C. and the residence time was varied --from two minutes to thirty minutes. The results, expressed in terms of weight percentage of the total desulphurized char sample weight in each case, and compared with a sixth, control, sample that was not treated with the alkali system (shown below as a Residence Time of O min.) were as follows:
,. . .::
Residence Water Ash Total Pyrite Other Sulphur ; TimeContent Content Sulphur Content Inor- contain-Content (FeS2) ganic ing Or-Sulphur ganic Compounds O min.1.49 32.91 2.85 o.63 0.13 1 40
2 min.12.10 14.56 0.73 0.12 0.02 0.59 5 min.12.55 13.18 o.46 0,12 0.07 0.27 10 min.29.77 12.87 0.07 0.05 0.00 0,02 0.l5 20 min.10.69 16.47 0 ,5 0 10 0 00 o.o5 30 min.15.93 19.92 o.o6 0.08 0.00 . i .
! The above results, recalculated on a dry basis, i.e., by -¦ 20 not including thewater content, and showing the desulphurization I achieved, are as follows:
.
~ - 8 -. ~ .
. ;i ,, 1 ' Residence Ash Total Pyrite Other Sulphur Percent-TimeContent Sulphur Content Inor- Con- age of content (FeS2) ganic taining Sulphur Sulphur Organic removal Compounds __ 0 33.412.89 o.64 0.13 1.42 2 16.560.83 0.14 0.02 o.67 71.3 15.070.53 0.14 0.08 0.31 81.7 18.330.10 0.07 0 0.03 96.5 18.44 0.17 0.11 0 o.o6 94.1 23.690.07 0.10 0 - 97.6 EXAMPLE III
To demonstrate the effect of desulphurization on the ignition temperature of char, a char was prepared from Hamilton coal at a temperature of 760 C. A 25-gram portion of this char having a -60 mesh particle size was desulphurized by the procedure set forth in Example I hereinabove and compared with both a 25-gram portion of the same char that was not desulphurized and a 25-gram sample of the original coai specimen. The results were as follows: - -Ignition Ash W E ~o~a~ T SPdElUmR C ~o~assium Temper- Content Sulphur in Ash in Ash Specimen ature Content _ _ . . . . _ Coal 570C7.92 2.~5o.64 2.32 Char 680C. 10.79 1.75 -1.45 2.32 Desulphur-ized Char 570 C. 5.74 0.25 1.50 1.72 It will be seen that the desulphurized char contained the , equivalent of about 9/0 of the sulphur in the original coal and the equivalent of about 14% of the sulphur in the char produced from that coal: that is, the treatment removed about 91% of the original coal sulphur content and about 860/o of the untreated char sulphur content.
.. 9 , EXAMPLE IV
To further demonstrate the ~ficacy of the method of the inventlon, a coal char was prepared from Hamilton coal at 540 C. and divided into four 25-gram specimens having a -60 mesh particle size. Two of these specimens were desulphurized by the procedure set fol~e~ in Example I hereinabove, and were -analyzed and compared with the corresponding analysis of the other two char specimens. The two sets of results were combined and were as follows:
Analysis of untreated char specimens - weight percent Water Ash Total Pyrite Sulphide Organic Content Content Sulphur Sulphur Sulphur Sulphur 1.02 9.561.79 0.24 0.41 1.14 ::
- Dry Basis - - 9.661.81 0.24 0.41 1.16 . . 'Z ~ ~.
Analysis of treated char specimens 13.25 2.99 0.01 0.01 0.00 o.
Dry Basis
! The above results, recalculated on a dry basis, i.e., by -¦ 20 not including thewater content, and showing the desulphurization I achieved, are as follows:
.
~ - 8 -. ~ .
. ;i ,, 1 ' Residence Ash Total Pyrite Other Sulphur Percent-TimeContent Sulphur Content Inor- Con- age of content (FeS2) ganic taining Sulphur Sulphur Organic removal Compounds __ 0 33.412.89 o.64 0.13 1.42 2 16.560.83 0.14 0.02 o.67 71.3 15.070.53 0.14 0.08 0.31 81.7 18.330.10 0.07 0 0.03 96.5 18.44 0.17 0.11 0 o.o6 94.1 23.690.07 0.10 0 - 97.6 EXAMPLE III
To demonstrate the effect of desulphurization on the ignition temperature of char, a char was prepared from Hamilton coal at a temperature of 760 C. A 25-gram portion of this char having a -60 mesh particle size was desulphurized by the procedure set forth in Example I hereinabove and compared with both a 25-gram portion of the same char that was not desulphurized and a 25-gram sample of the original coai specimen. The results were as follows: - -Ignition Ash W E ~o~a~ T SPdElUmR C ~o~assium Temper- Content Sulphur in Ash in Ash Specimen ature Content _ _ . . . . _ Coal 570C7.92 2.~5o.64 2.32 Char 680C. 10.79 1.75 -1.45 2.32 Desulphur-ized Char 570 C. 5.74 0.25 1.50 1.72 It will be seen that the desulphurized char contained the , equivalent of about 9/0 of the sulphur in the original coal and the equivalent of about 14% of the sulphur in the char produced from that coal: that is, the treatment removed about 91% of the original coal sulphur content and about 860/o of the untreated char sulphur content.
.. 9 , EXAMPLE IV
To further demonstrate the ~ficacy of the method of the inventlon, a coal char was prepared from Hamilton coal at 540 C. and divided into four 25-gram specimens having a -60 mesh particle size. Two of these specimens were desulphurized by the procedure set fol~e~ in Example I hereinabove, and were -analyzed and compared with the corresponding analysis of the other two char specimens. The two sets of results were combined and were as follows:
Analysis of untreated char specimens - weight percent Water Ash Total Pyrite Sulphide Organic Content Content Sulphur Sulphur Sulphur Sulphur 1.02 9.561.79 0.24 0.41 1.14 ::
- Dry Basis - - 9.661.81 0.24 0.41 1.16 . . 'Z ~ ~.
Analysis of treated char specimens 13.25 2.99 0.01 0.01 0.00 o.
Dry Basis
- 3.45 0.01 0.01 0.00 0.00 -The percentage of desulphurization for the treated epecimens was thus a~oui 99.4.
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Claims (18)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for desulfurizing coal char said process comprising adding said char to molten caustic to form a mixture such that the ratio of molten caustic to char in said mixture is at least about three to one, the residence time of said char in said mixture is about two minutes to about thirty minutes and is sufficient to lower the sulfur Content of said char.
2. The process as claimed in claim 1 wherein said molten caustic is formed from the group comprising sodium hydroxide, potassium hydroxide, calcium oxide, sodium carbonate, and mixture thereof.
3. The process as claimed in claim 1 wherein said molten caustic is formed from about equal parts by weight of sodium hydroxide and potassium hydroxide, and the temperature of said mixture is maintained between about 500°F and about 750°F (about 260°C and about 400°C).
4. The process as claimed in claim 1 wherein said molten caustic is formed from about equal parts of sodium hydroxide and potassium hydroxide, the temperature of said mixture is maintained between about 500°F and about 750°F (about 260°C and about 400°C), plus the step of washing said char so that said char is substantially free of caustic.
5. The process as claimed in claim 4 wherein the sulfur content of said washed char is no greater than about 0.7 percent by weight on a dry basis.
6. A process which both desulfurizes and lowers the ash content of coal char said process comprising adding said char to a bath of molten caustic, said bath having a ratio of molten caustic to char of at least about three to one, for a residence time of from about two minutes to about thirty minutes, sufficient to lower both the sulfur and the ash content of said char.
7. The process as claimed in claim 6 wherein said molten caustic is formed from the group comprising sodium hydroxide, potassium hydroxide, calcium oxide, sodium carbonate, and mixtures thereof.
8. The process as claimed in claim 6 wherein said molten caustic is formed from a mixture of about equal parts of sodium hydroxide and potassium hydroxide, and the temperature of said bath is maintained between about 500°F
and about 750°F (about 260°C and about 400°C).
and about 750°F (about 260°C and about 400°C).
9. The process as claimed in claim 6 wherein said molten caustic is formed from a mixture of about equal parts of sodium hydroxide and pota-ssium hydroxide, the temperature of said bath is maintained between about 500°F and about 750°F (about 260°C and about 400°C), and said char is removed from said bath and washed so that said char is substantially free of caustic.
10. A process for producing low sulfur char from coal comprising:
a) converting said coal to char by heating at a temperature no greater than about 1600°F (about 870°C) and b) adding said char to a bath of molten caustic, said bath having a ratio of molten caustic to char of at least about three to one, for a residence time of from about two minutes to about thirty minutes, sufficient to lower the sulfur content of said char.
a) converting said coal to char by heating at a temperature no greater than about 1600°F (about 870°C) and b) adding said char to a bath of molten caustic, said bath having a ratio of molten caustic to char of at least about three to one, for a residence time of from about two minutes to about thirty minutes, sufficient to lower the sulfur content of said char.
11. The process as claimed in claim 10 wherein said molten caustic is formed from the group comprising sodium hydroxide, potassium hydroxide, calcium oxide, sodium carbonate, and mixtures thereof.
12. The process as claimed in claim 10 wherein said molten caustic is formed from a mixture of about equal parts of sodium hydroxide and potassium hydroxide, and said bath is maintained at a temperature of about 500°F to about 750°F (about 260°C and about 400°C).
13. The process as claimed in claim 10 wherein said coal is converted to said char at a temperature of about 1000°F to about 1100°F (about 540°C
to about 595°C) said molten caustic is formed from a mixture of about equal parts of sodium hydroxide and potassium hydroxide, said bath is maintained at a temperature of about 500°F to about 750°F (about 260°C to about 400°C) said residence time is about ten minutes, said char is removed from said bath and washed sufficiently to cause said char to be substantially free of said caustic, and the sulfur content of said char is reduced to a value no greater than about 0.7 percent by weight on a dry basis.
to about 595°C) said molten caustic is formed from a mixture of about equal parts of sodium hydroxide and potassium hydroxide, said bath is maintained at a temperature of about 500°F to about 750°F (about 260°C to about 400°C) said residence time is about ten minutes, said char is removed from said bath and washed sufficiently to cause said char to be substantially free of said caustic, and the sulfur content of said char is reduced to a value no greater than about 0.7 percent by weight on a dry basis.
14. A process for producing a low sulfur, low ash, low ignition temperature char from coal, said process comprising:
a) converting said coal to char by heating at a temperature no greater than about 1600°F (about 870°C) and b) adding said char to a bath of molten caustic, said bath having a ratio of molten caustic to char of at least about three to one, for a residence time of from about two minutes to about thirty minutes, sufficient to lower the sulfur content of said char to less than that of said coal, sufficient to lower the ash content of said char to less than that of said coal, and sufficient to lower the ignition temperature of said char so that said char ignition temperature is no higher than about the ignition tempera-ture of said coal.
a) converting said coal to char by heating at a temperature no greater than about 1600°F (about 870°C) and b) adding said char to a bath of molten caustic, said bath having a ratio of molten caustic to char of at least about three to one, for a residence time of from about two minutes to about thirty minutes, sufficient to lower the sulfur content of said char to less than that of said coal, sufficient to lower the ash content of said char to less than that of said coal, and sufficient to lower the ignition temperature of said char so that said char ignition temperature is no higher than about the ignition tempera-ture of said coal.
15. The process as claimed in claim 14 wherein said molten caustic is formed from the group comprising sodium hydroxide, potassium hydroxide, calcium oxide, sodium carbonate, and mixtures thereof.
16. The process as claimed in claim 15 wherein said molten caustic is formed from a mixture of about equal parts of sodium hydroxide and potassium hydroxide, the temperature of said bath is between about 500°F and about 750°F, (about 260°C and about 400°C) and said char is removed from said bath and washed sufficiently to cause said char to be substantially free of said caustic.
17. A process for producing low sulfur char from coal according to claim 10 comprising:
a) converting said coal to char by heating at temperature no greater than about 1350°F (about 730°C) and b) adding said char to a bath of molten caustic, said bath having a ratio of molten caustic to char of at least about three to one, for a resi-dence time of from about two minutes to about thirty minutes, sufficient to lower the sulfur content of said char to a value no greater than about 0.7 percent by weight on a dry basis.
a) converting said coal to char by heating at temperature no greater than about 1350°F (about 730°C) and b) adding said char to a bath of molten caustic, said bath having a ratio of molten caustic to char of at least about three to one, for a resi-dence time of from about two minutes to about thirty minutes, sufficient to lower the sulfur content of said char to a value no greater than about 0.7 percent by weight on a dry basis.
18. A process for producing low sulfur char from coal comprising converting said coal to char at a temperature of about 1000°F to about 1350°F
(about 540°C to about 730°C) and adding said char to a bath of molten caustic said bath having a ratio of molten caustic to char of at least about three to one, for a residence time of from about two minutes to about thirty minutes, wherein said molten caustic is formed from a mixture of about equal parts of sodium hydroxide and potassium hydroxide, said bath is maintained at a temperature of about 500°F to about 750°F (about 260°C to about 400°C) said char is removed from said bath and washed sufficiently to cause said char to be substantially free of said caustic, and the sulfur content of said char is reduced to a value no greater than about 0.7 percent by weight on a dry basis.
(about 540°C to about 730°C) and adding said char to a bath of molten caustic said bath having a ratio of molten caustic to char of at least about three to one, for a residence time of from about two minutes to about thirty minutes, wherein said molten caustic is formed from a mixture of about equal parts of sodium hydroxide and potassium hydroxide, said bath is maintained at a temperature of about 500°F to about 750°F (about 260°C to about 400°C) said char is removed from said bath and washed sufficiently to cause said char to be substantially free of said caustic, and the sulfur content of said char is reduced to a value no greater than about 0.7 percent by weight on a dry basis.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US42970874A | 1974-01-02 | 1974-01-02 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1056322A true CA1056322A (en) | 1979-06-12 |
Family
ID=23704379
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA214,068A Expired CA1056322A (en) | 1974-01-02 | 1974-11-19 | Process for reducing the sulphur content of coal and coal char and the ignition temperature of coal char |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JPS5098901A (en) |
| CA (1) | CA1056322A (en) |
| GB (1) | GB1492600A (en) |
| IN (1) | IN142596B (en) |
| PL (1) | PL93927B1 (en) |
| ZA (1) | ZA747581B (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5085764A (en) * | 1981-03-31 | 1992-02-04 | Trw Inc. | Process for upgrading coal |
| CA2001852A1 (en) * | 1988-11-01 | 1990-05-01 | Iwao Numakura | Process and apparatus for the formation of negative resist pattern |
| EP1622995A1 (en) * | 2003-03-31 | 2006-02-08 | Council of Scientific and Industrial Research | A process for removal of organic sulphur from high sulphur coal and a device thereof |
-
1974
- 1974-11-12 GB GB49021/74A patent/GB1492600A/en not_active Expired
- 1974-11-19 CA CA214,068A patent/CA1056322A/en not_active Expired
- 1974-11-22 IN IN2607/CAL/74A patent/IN142596B/en unknown
- 1974-11-27 ZA ZA00747581A patent/ZA747581B/en unknown
- 1974-12-27 JP JP50001042A patent/JPS5098901A/ja active Pending
-
1975
- 1975-01-02 PL PL1975177116A patent/PL93927B1/pl unknown
Also Published As
| Publication number | Publication date |
|---|---|
| GB1492600A (en) | 1977-11-23 |
| ZA747581B (en) | 1975-12-31 |
| PL93927B1 (en) | 1977-07-30 |
| AU7556374A (en) | 1976-05-20 |
| JPS5098901A (en) | 1975-08-06 |
| IN142596B (en) | 1977-07-30 |
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