CA1129360A - Pipeline liquefaction of coal and other carbonaceous material - Google Patents
Pipeline liquefaction of coal and other carbonaceous materialInfo
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- CA1129360A CA1129360A CA348,025A CA348025A CA1129360A CA 1129360 A CA1129360 A CA 1129360A CA 348025 A CA348025 A CA 348025A CA 1129360 A CA1129360 A CA 1129360A
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Abstract
ABSTRACT OF THE DISCLOSURE
A method and apparatus are disclosed for the simultaneous liquefaction and transportation of coal in a pipeline. The initial section of the pipeline is utilized as a reaction vessel for the liquefaction of particulate coal by reaction with hydrogen under elevated temperature and pressure, the particulate coal being introduced in the form of an oil-based slurry. A portion of liquefied or partially liquefied coal is recycled from a point downstream in said pipeline to the feed-in region to form a part or all of the oil carrier of said slurry. The remainder of the coal-containing reaction mixture is fed on through the pipeline while allowing liquefaction to continue to completion with progressive let-down of pressure to normal pipeline operating pressures.
A method and apparatus are disclosed for the simultaneous liquefaction and transportation of coal in a pipeline. The initial section of the pipeline is utilized as a reaction vessel for the liquefaction of particulate coal by reaction with hydrogen under elevated temperature and pressure, the particulate coal being introduced in the form of an oil-based slurry. A portion of liquefied or partially liquefied coal is recycled from a point downstream in said pipeline to the feed-in region to form a part or all of the oil carrier of said slurry. The remainder of the coal-containing reaction mixture is fed on through the pipeline while allowing liquefaction to continue to completion with progressive let-down of pressure to normal pipeline operating pressures.
Description
This invention relates to a method and apparatus for the simultaneous liquefaction and transportation of coal in a pipeline, an initial section of which is used as a high temperature and pressure reactor to effect at least a part of the liquefaction reaction.
It is known that one of the most economical ways of transporting coal is in a pipeline in particulate form as a slurry, the carrier being either water or oil. Such pipelines are normally operated at a pressure of about 1,400 psi and at ambient temperature. Transmission rates run from 3 to 8 feet per second, with five feet per second being a common value. The coal is finely ground to a size range of from 14 to 200 mesh to inhibit settling during transmission. The concentration of coal usually ranges from 30 to 40%
by volume, with 35% being an accepted ratio.
It is also known that finely ground coal can be liquefied, i.e.
converted from a solid into a liquid, by slurrying in an appropriate oil carrier at high temperatures and pressures in the presence of hydrogen and with or without a catalyst. The hydrogen can be supplied as hydrogen gas, from a hydrogen donor solvent, or from a generating system. Examples of hydrogen donor solvents include tetralin isopropanol, anthracene and phen-anthrene. The generating system commonly used is the water gas or shift reaction where carbon monoxide is reacted with steam to generate hydrogen and carbon dioxide. This can be operated to give final gas blends of various ratios of hydrogen to carbon monoxide~ often called synthesis gas or producer gas. Typical liquefaction operating conditions are temperatures of 325C to 500C and pressures of 1000 to 4000 psi. For such a reaction the coal is commonly ground to a particle size in the range of from thirty to two hundred mesh. Slurry concentrations of 30 to 50% coal in oil, by volume are generally used.
A preferred technique for providing the oil carrier is to start up ' - 1-., - . . :,~ .. .: : :
3t~) with a solvent such as phenanthrene or a particular distillate cut from petro-le~ refining. After the slurry has passed through the reactor, a portion of the liquefied slurry, typically one-third, is returned to the reactor to provide the initial solvent carrier. The process then becomes continuous, with a one-third to one-half recycle of slurry, as desired. Residence times in the reactor vary from a few minutes, generally five to fifteen, to two hours, depending on the design of the reactor and whether or not a catalyst is used. Suitable catalysts are iron, cobalt, molybdenum, zinc chloride and alkali carbonates. The iron and alkali carbonates found naturally in some coals, particularly lignites, have been found to give enough catalytic activ-ity so that additional catalyst is not needed.
Pipelining and liquefaction of coal are both characterized by very heavy capital investment, now in the billion dollar per installation category.
Generally, the source of the coal is distant from the point of ultimate con-sumer use, so that lengthy transportation of the coal or the oil derived from it is required. Thus, to pipeline coal as a slurry and then liquefy it at its destination involves the sum of these separate costs.
United States Patent 3,527,692 ~Paul E. Titus) relates to a method for the simultaneous transportation and recovery of shale oil from oil shale flowing as a slurry within a pipeline. A slurry of crushed oil shale in an oil carrier is transported by means of a pipeline, while simultaneously heat-ing the slurry to a temperature of about 550 to 600~ within the pipeline until the kerogen within the oil shale is converted to shale oil, It will be appreciated that this prior patent does not relate to a hydrogenation process, nor to the treatment of coal. Canadian Patent 907,559 ~Loyd R. Kern) dis-closes the hydrogenation of crude oil in a pipeline, but is not concerned with the problems of liquefaction or transportation of solid materials.
One of the primary problems of existing coal liquefaction processes
It is known that one of the most economical ways of transporting coal is in a pipeline in particulate form as a slurry, the carrier being either water or oil. Such pipelines are normally operated at a pressure of about 1,400 psi and at ambient temperature. Transmission rates run from 3 to 8 feet per second, with five feet per second being a common value. The coal is finely ground to a size range of from 14 to 200 mesh to inhibit settling during transmission. The concentration of coal usually ranges from 30 to 40%
by volume, with 35% being an accepted ratio.
It is also known that finely ground coal can be liquefied, i.e.
converted from a solid into a liquid, by slurrying in an appropriate oil carrier at high temperatures and pressures in the presence of hydrogen and with or without a catalyst. The hydrogen can be supplied as hydrogen gas, from a hydrogen donor solvent, or from a generating system. Examples of hydrogen donor solvents include tetralin isopropanol, anthracene and phen-anthrene. The generating system commonly used is the water gas or shift reaction where carbon monoxide is reacted with steam to generate hydrogen and carbon dioxide. This can be operated to give final gas blends of various ratios of hydrogen to carbon monoxide~ often called synthesis gas or producer gas. Typical liquefaction operating conditions are temperatures of 325C to 500C and pressures of 1000 to 4000 psi. For such a reaction the coal is commonly ground to a particle size in the range of from thirty to two hundred mesh. Slurry concentrations of 30 to 50% coal in oil, by volume are generally used.
A preferred technique for providing the oil carrier is to start up ' - 1-., - . . :,~ .. .: : :
3t~) with a solvent such as phenanthrene or a particular distillate cut from petro-le~ refining. After the slurry has passed through the reactor, a portion of the liquefied slurry, typically one-third, is returned to the reactor to provide the initial solvent carrier. The process then becomes continuous, with a one-third to one-half recycle of slurry, as desired. Residence times in the reactor vary from a few minutes, generally five to fifteen, to two hours, depending on the design of the reactor and whether or not a catalyst is used. Suitable catalysts are iron, cobalt, molybdenum, zinc chloride and alkali carbonates. The iron and alkali carbonates found naturally in some coals, particularly lignites, have been found to give enough catalytic activ-ity so that additional catalyst is not needed.
Pipelining and liquefaction of coal are both characterized by very heavy capital investment, now in the billion dollar per installation category.
Generally, the source of the coal is distant from the point of ultimate con-sumer use, so that lengthy transportation of the coal or the oil derived from it is required. Thus, to pipeline coal as a slurry and then liquefy it at its destination involves the sum of these separate costs.
United States Patent 3,527,692 ~Paul E. Titus) relates to a method for the simultaneous transportation and recovery of shale oil from oil shale flowing as a slurry within a pipeline. A slurry of crushed oil shale in an oil carrier is transported by means of a pipeline, while simultaneously heat-ing the slurry to a temperature of about 550 to 600~ within the pipeline until the kerogen within the oil shale is converted to shale oil, It will be appreciated that this prior patent does not relate to a hydrogenation process, nor to the treatment of coal. Canadian Patent 907,559 ~Loyd R. Kern) dis-closes the hydrogenation of crude oil in a pipeline, but is not concerned with the problems of liquefaction or transportation of solid materials.
One of the primary problems of existing coal liquefaction processes
- 2 -'' ` ' ~ ~ ' and coal slurry pipelines is the requirement for large amounts of cooling or carrier water. This is a major stumbling block for the liquefaction plants in the coal fields in the dry middle-western United States. For the same reason of lack of water, coal cannot normally be pipelined as a water slurry, while oil is now too expensive as a carrier or is not available at the source of the coal.
It is an object of the present invention to provide an economic process for simultaneously liquefying and transporting coal in a pipeline and an apparatus for carrying out such process. It is a further object of the invention to avoid the disadvantage of utilizing very large quantities of carrier or cooling water. Another object of the invention is to reduce the need for pressure let-down valves, heat exchangers and cooling water.
Accordingly, one aspect of the invention provides a method for the simultaneous liquefaction of coal and transportation thereof in a pipeline, which method comprises feeding a slurry of particulate coal in an oil carrier into and through an initial liquefaction section of pipeline maintained under elevated temperature and pressure; providing in said liquefaction section of pipeline a source of hydrogen for reaction with the particulate coal to at least commence liquefaction thereof; recycling a portion of at least partially liquefied coal from a point downstream in said pipeline to the initial lique-faction section thereof to provide a part or all of the oil carrier; feeding the remainder of the liquefied coal through the pipeline while allowing liquefaction to continue to completion with progressive pressure let-down by line friction loss; and thereafter transporting the liquefied coal through the pipeline.
Suitable operating temperatures and pressures for the initial pipe-line section are in the range of about 250 to 500C preferably 325 to 425C
or 450C, and 1500 to 5000 psi, with a pipeline feed velocity of from 3 to .
:: . .. . ..
, ~ ,, . , ~ , ,:
: : ~ - ; .
~2~3~
feet per second. One major advantage of the combined liquefaction and trans-portation process of the invention is the reduced need for water. The transportation process is in fact facilitated by the in situ liquefaction since fluid carrier, i.e. oil, is released from the coal under the liquefac-tion effect of the added hydrogen. One of the current drawbacks to coal pipe-lining is the need to provide huge amounts of water to move the coal and this is hard to get in some places. Similarly, vast amounts of water are needed for on-site liquefaction. For either pipelining or on-site liquefaction thousands of acre feet of water are needed. The invention removes this water supply drawback.
Another aspect of the invention provides an apparatus for the com-bined liquefaction and transportation of coal, which comprises: ~a) a pipe-line including an initial liquefaction section adapted to carry a flow of coal-in-oil slurry and reaction gases under elevated pressure and temperature and downstream from said liquefaction section a transport section; (b) means for feeding a coil-in-oil slurry and reaction gases to the beginning of the liquefaction section; (c) a recycle section extending from the end of the liquefaction section back to or near the beginning of the liquefaction section for recycling a portion of the partially processed feed back to the beginning of the liquefaction section to constitute a part or all of the oil carrier of said slurry; and (d~ discharge means at the downstream end of said transport section for discharging liquefied coal and associated gases and solids.
If water is to be eliminated as a carrier for coal, oil has to be used. In the invention~ most or all of the oil can come from the coal itself.
Moreover, if water is to be eliminated as a coolant for liquefaction reactors, by the present invention, the surface area of the reactor is extended by converting the reactor into a pipeline so that heat loss by natural convec-tion and conduction to the environment is adequate. Once the liquefaction is , - 4 -: . .: .
' 3LlZ~ti~3 started, using a once only external charge of oil, part of the liquefaction product is drawn off downstream and recycled to the entrance of the pipeline reactor and slurried with the incoming coal. In this way the pipelining of coal can be carried out in dry areas of the country without fear of harm to local water supplies. It is this unexpected use of the coal itself, as its own carrier, that opens up this new technology.
One immediate gain in economics is in energy density processed through the pipeline. A conventional coal-in-water pipeline carries 50 per-cent by weight of water. Thus, half of the load is water which has no energy value at discharge. When the coal is used as the carrier, part as oil, part as gases from the liquefaction, and part as solid residue or char, the whole load can be burned at discharge. Thus, the energy density is doubled. This in turn cuts the capital cost in half. This cost in turn includes the cost of the pipeline, and its installation. The pipeline now becomes the lique-faction reactor. The liquefaction reactor comprises about one-third of the capital cost of a liquefaction complex, which is effectively saved by an installation operating according to the invention. This then is one of the economic incentives of the invention. The environmental incentive is the removal of the high water demand for the separate process.
It is the removal of the water restriction on coal pipelining which renders the process of the invention virtually independent of discharge "conversion" values. It does not matter whether the coal is discharged large-ly as a gas, or largely as an oil, or largely as a char, provided the product mix is such that it will flow through the pipeline, carried along by its own mass. On discharge the mass can be burned as is, in a power plant, or the gases and liquids can be separated out and reprocessed as needed and the char burnt as a boiler fuel. Indeed the capital cost for reprocessing is already more than covered in the liquefaction portion of the overall cost, since this ,.; .. , , ~,' , ,, ~ ~, :.
:: : :: .. . .
.~ ~: , , -: ~ :
.: , ,; ~ .. , ~L12~3fi() includes refining costs and in the slurry dewatering charges at discharge, which no longer exist.
The accompanying drawing is a schematic illustration of a preferred embodiment of the method of the invention.
Referring now to the drawing, there is shown diagrammatically a pipeline modified at the feed end to effect coal liquefaction in accordance with the invention. Hot reaction gases are fed into the feed end of the pipe-line at 1 together with an oil slurry of ground coal and reaction commences and proceeds as the coal passes down the liquefaction leg of the pipeline. At point 2, a portion of the partially liquefied coal is recycled to the feed end 1, and liquefaction continues in the recycle leg so the effective time of liquefaction of the recycled slurry is doubled. Naturally the distance between points 1 and 2 can be varied, depending on the particular nature and amount of raw material being processed and the reaction conditions being employed.
If desired, a second recycle point can be located further down the pipeline and either the first or the second, or both, can be chosen for recycling par-tially liquefied coal, depending on the monitored progress of the reaction and the volume of feedstock coming on-stream. Moreover, hot reaction gases can be introduced at either point 1 or point 2 or at both places simultaneously or alternately.
The balance of the coal slurry proceeds on through the pipeline.
Additional recycle legs can optionally be provided as shownJ if necessary with further heatingl at points further down the pipeline. At the discharge end of the pipeline, the liquefied coal product is separated from gases and solids present.
A preferred embodiment of the invention will now be described. The pipeline is designed to operate at a throughput velocity of five feet per second, in turbulent flow. This prevents settling and assures good mixing for .
... .
It is an object of the present invention to provide an economic process for simultaneously liquefying and transporting coal in a pipeline and an apparatus for carrying out such process. It is a further object of the invention to avoid the disadvantage of utilizing very large quantities of carrier or cooling water. Another object of the invention is to reduce the need for pressure let-down valves, heat exchangers and cooling water.
Accordingly, one aspect of the invention provides a method for the simultaneous liquefaction of coal and transportation thereof in a pipeline, which method comprises feeding a slurry of particulate coal in an oil carrier into and through an initial liquefaction section of pipeline maintained under elevated temperature and pressure; providing in said liquefaction section of pipeline a source of hydrogen for reaction with the particulate coal to at least commence liquefaction thereof; recycling a portion of at least partially liquefied coal from a point downstream in said pipeline to the initial lique-faction section thereof to provide a part or all of the oil carrier; feeding the remainder of the liquefied coal through the pipeline while allowing liquefaction to continue to completion with progressive pressure let-down by line friction loss; and thereafter transporting the liquefied coal through the pipeline.
Suitable operating temperatures and pressures for the initial pipe-line section are in the range of about 250 to 500C preferably 325 to 425C
or 450C, and 1500 to 5000 psi, with a pipeline feed velocity of from 3 to .
:: . .. . ..
, ~ ,, . , ~ , ,:
: : ~ - ; .
~2~3~
feet per second. One major advantage of the combined liquefaction and trans-portation process of the invention is the reduced need for water. The transportation process is in fact facilitated by the in situ liquefaction since fluid carrier, i.e. oil, is released from the coal under the liquefac-tion effect of the added hydrogen. One of the current drawbacks to coal pipe-lining is the need to provide huge amounts of water to move the coal and this is hard to get in some places. Similarly, vast amounts of water are needed for on-site liquefaction. For either pipelining or on-site liquefaction thousands of acre feet of water are needed. The invention removes this water supply drawback.
Another aspect of the invention provides an apparatus for the com-bined liquefaction and transportation of coal, which comprises: ~a) a pipe-line including an initial liquefaction section adapted to carry a flow of coal-in-oil slurry and reaction gases under elevated pressure and temperature and downstream from said liquefaction section a transport section; (b) means for feeding a coil-in-oil slurry and reaction gases to the beginning of the liquefaction section; (c) a recycle section extending from the end of the liquefaction section back to or near the beginning of the liquefaction section for recycling a portion of the partially processed feed back to the beginning of the liquefaction section to constitute a part or all of the oil carrier of said slurry; and (d~ discharge means at the downstream end of said transport section for discharging liquefied coal and associated gases and solids.
If water is to be eliminated as a carrier for coal, oil has to be used. In the invention~ most or all of the oil can come from the coal itself.
Moreover, if water is to be eliminated as a coolant for liquefaction reactors, by the present invention, the surface area of the reactor is extended by converting the reactor into a pipeline so that heat loss by natural convec-tion and conduction to the environment is adequate. Once the liquefaction is , - 4 -: . .: .
' 3LlZ~ti~3 started, using a once only external charge of oil, part of the liquefaction product is drawn off downstream and recycled to the entrance of the pipeline reactor and slurried with the incoming coal. In this way the pipelining of coal can be carried out in dry areas of the country without fear of harm to local water supplies. It is this unexpected use of the coal itself, as its own carrier, that opens up this new technology.
One immediate gain in economics is in energy density processed through the pipeline. A conventional coal-in-water pipeline carries 50 per-cent by weight of water. Thus, half of the load is water which has no energy value at discharge. When the coal is used as the carrier, part as oil, part as gases from the liquefaction, and part as solid residue or char, the whole load can be burned at discharge. Thus, the energy density is doubled. This in turn cuts the capital cost in half. This cost in turn includes the cost of the pipeline, and its installation. The pipeline now becomes the lique-faction reactor. The liquefaction reactor comprises about one-third of the capital cost of a liquefaction complex, which is effectively saved by an installation operating according to the invention. This then is one of the economic incentives of the invention. The environmental incentive is the removal of the high water demand for the separate process.
It is the removal of the water restriction on coal pipelining which renders the process of the invention virtually independent of discharge "conversion" values. It does not matter whether the coal is discharged large-ly as a gas, or largely as an oil, or largely as a char, provided the product mix is such that it will flow through the pipeline, carried along by its own mass. On discharge the mass can be burned as is, in a power plant, or the gases and liquids can be separated out and reprocessed as needed and the char burnt as a boiler fuel. Indeed the capital cost for reprocessing is already more than covered in the liquefaction portion of the overall cost, since this ,.; .. , , ~,' , ,, ~ ~, :.
:: : :: .. . .
.~ ~: , , -: ~ :
.: , ,; ~ .. , ~L12~3fi() includes refining costs and in the slurry dewatering charges at discharge, which no longer exist.
The accompanying drawing is a schematic illustration of a preferred embodiment of the method of the invention.
Referring now to the drawing, there is shown diagrammatically a pipeline modified at the feed end to effect coal liquefaction in accordance with the invention. Hot reaction gases are fed into the feed end of the pipe-line at 1 together with an oil slurry of ground coal and reaction commences and proceeds as the coal passes down the liquefaction leg of the pipeline. At point 2, a portion of the partially liquefied coal is recycled to the feed end 1, and liquefaction continues in the recycle leg so the effective time of liquefaction of the recycled slurry is doubled. Naturally the distance between points 1 and 2 can be varied, depending on the particular nature and amount of raw material being processed and the reaction conditions being employed.
If desired, a second recycle point can be located further down the pipeline and either the first or the second, or both, can be chosen for recycling par-tially liquefied coal, depending on the monitored progress of the reaction and the volume of feedstock coming on-stream. Moreover, hot reaction gases can be introduced at either point 1 or point 2 or at both places simultaneously or alternately.
The balance of the coal slurry proceeds on through the pipeline.
Additional recycle legs can optionally be provided as shownJ if necessary with further heatingl at points further down the pipeline. At the discharge end of the pipeline, the liquefied coal product is separated from gases and solids present.
A preferred embodiment of the invention will now be described. The pipeline is designed to operate at a throughput velocity of five feet per second, in turbulent flow. This prevents settling and assures good mixing for .
... .
3~C) the liquefaction process. A slurry of 50% by weight of coal in oil is made up and fed into the pipeline in a continuous manner, with the coal ground to a 100 to 200 mesh size. For initial start up, a blend of 10% tetralin and 90%
anthracene is used as carrier for the coal. Effluent gas from an oxygen-fed, coal-fired, producer gas plant is blown directly into the slurry in the pipe-line to heat it to about 435C and to start the liquefaction process. Producer gas is a carbon monoxide/hydrogen blend obtained from coal. Alternatively the CO/H blend obtained from the reforming of methane and known as synthesis gas could be used.
The producer gas is adjusted with steam to give a one to one ratio of hydrogen to carbon monoxide in the gas stream.
Steam could be fed directly with carbon monoxide, without separate hydrogen, since the hydrogen is then obtained from the steam in the lique-faction leg. Thus either Co and H2, or CO and H20 or CO, H2 and H20 can be employed as the reaction gas mixture. Water can be used as the source of steam or hydrogen, either the water content of the coal as-mined or water added in the grinding process. The gas is added at a rate sufficient to pro-vide 20,000 standard cubic feet of hydrogen per ton of coal feed to the pipe-line. The pipeline is insulated to retain the heat fed in by the hot producer gas and also that liberated by the exothermic liquefaction reactions. At a point 3,000 feet downstream, corresponding to a residence time of ten minutes in the pipeline, one-third of the slurry is drawn off from the top of the pipeline and returned to the feed end to provide or augment the carrier fluid.
This initial 3,000 foot pipeline section is the liquefaction section or leg and is operated at a pressure of about 3,000 psi and a temperature throughout of about 435C. In an alternative embodiment a liquefaction leg of about 1500 feet could be used, corresponding to a residence time of 5 minutes, the reaction temperature being simil~r or higher. A further alternative would be . ~ , . : .. . : :
., ~ , .: ., :
~Z~ 3 a lique:Eaction leg of 6000 feet and a reaction temperature of 300C, corres ponding to a residence time of about 20 mimltes at this lower temperature. Of course, in each case the residence time of the recycle portion is effectively doubled as the material also passes through the recycle portion.
After the liquefaction section pressure let down occurs gradually as a result of natural frictional drag to the normal 1200 to 1600 psi pipeline operating pressure. The temperature is also permitted to fall in a gradual manner. During this period of gradually falling temperature and pressure the liquefaction reactions continue to completion in the presence of hydrogen and carbon monoxide gases. In this way, the effective residence time for reaction is increased greatly at no additional capital cost. If desired, second or third recycle legs can be inserted downstream to boost liquefaction or to reheat.
Process conditions in the pipeline can, of course, be varied depend-ing on the nature of the feed and the type of product desired. Generally, increasing the pressure and the hydrogen feed leads to more hydrocracking and a product distilling at a lower temperature. The pipeline slurry viscosity can also be reduced. If desired, catalysts can be added to obtain a specific effect. The range of possible process conditions is given in the following Table.
The ability to vary residence time at will without changing the throughput of the pipeline is an important advantage of the invention over the prior art. Previously, if the residence time was lengthened, throughput would be correspondingly reduced~ I`his is because the liquefaction reactor volume is fixed. In the process of the invention, the "reactor" volume is variable, in effect, over any desired length of the pipeline. Thus the invention is inherently more flexible in the treatment of different types of coal.
Another advantage of the ability to switch on demand to longer ~: ~....... : , 3fi~
residence times (i.e. larger reactor volumes~ and lower operating temperatures is that corrosive effects, e.g. from hydrogen attack on pipeline metal, are reduced. Moreover, operation at the lowest reactive temperature possible, with no loss of throughput because of the extended residence time is obviously one alternative available from the invention. This reduces wear and tear and plant material costs. Conventional plants must generally operate at high temperatures to get the fastest reaction and thereby maintain adequate through-put and also to save on reactor size.
POSSIBLE PIPELINE LIQUEFACTION CONDITIONS
r Process Parameter Range .
Coal in slurry ~% by weight) 35 to 50 Water in coal feed ~% by weight) 2 to 35 Recycle ratio ~volume) 1/4 to 3/4 Temperature (C) 200 or 250 to 500 Pressure (psi) 1200 to 5000 Hydrogen/Carbon Monoxide Ratio in Gas Feed 1/0 to 0/1 Hydrogen Feed Rate (s.c.f./ton coal~ 10,000 to 30,000 Pipeline velocity, feet/sec. 3 to ~
Length of liquefaction of leg (feet~ 600 to 6000 Residence time for liquefaction section ~minutes) 2 to 20 Under such conditions up to 95% of the coal can be converted to a liquid or gaseous fraction, with an oil yield of up to 60%. The difference between the conversion and the oil yield is due to the formation of hydro-carbon gases, methane, ethane, propane, etc., and carbon dioxide gas. Thus, the pipeline is carrying a mix of gases, oils and some residual solids. These , _ g _ ,."i, .:
.. : . : . .:~.. ..
:, , ~ :,; . :
- ~ , : . , , l~X~3~
can be separated and collected on discharge from the pipeline. Coal general-ly contains from 2.5% to 5.5% hydrogen by weight. Crude oil contains about 12% hydrogen by weight, and natural gas about 25%. The objective in coal liquefaction is to add hydrogen to the coal, either from hydrogen gas directly, or from steam, to bring the hydrogen content closer to that of oil. A liquid product of about 7% to 11% hydrogen is satisfactory, and to be expected.
The technique is applicable to coals of all ranks, from anthracite to lignite. It is particularly suitable for lignite since the water content of lignite can be used to promote the water gas shift reaction during the transmission of the lignite. Lignites also sometimes contain iron or alkali carbonates which contribute to the catalytic effect utilized in the hydrogena-tion reactions.
The invention is also applicable to other carbonaceous feed stocks, such as peat, wood, agricultural waste and municipal waste. Moreover, while the invention is particularly useful for the liquefaction of carbonaceous material, it is also applicable to the treatment of mineral ores and other solids, gases or liquids, during transmission in a pipeline. Examples include the microbial treatment of a mineral ore in a slurry of water and the cataly-tic conversion of natural gas to ethylene. The invention affords a particular-ly attractive route for exploiting reactions and processes requiring long residence times, wherever these can be combined with a bulk transportation need.
- lQ --.
. ~
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: .
anthracene is used as carrier for the coal. Effluent gas from an oxygen-fed, coal-fired, producer gas plant is blown directly into the slurry in the pipe-line to heat it to about 435C and to start the liquefaction process. Producer gas is a carbon monoxide/hydrogen blend obtained from coal. Alternatively the CO/H blend obtained from the reforming of methane and known as synthesis gas could be used.
The producer gas is adjusted with steam to give a one to one ratio of hydrogen to carbon monoxide in the gas stream.
Steam could be fed directly with carbon monoxide, without separate hydrogen, since the hydrogen is then obtained from the steam in the lique-faction leg. Thus either Co and H2, or CO and H20 or CO, H2 and H20 can be employed as the reaction gas mixture. Water can be used as the source of steam or hydrogen, either the water content of the coal as-mined or water added in the grinding process. The gas is added at a rate sufficient to pro-vide 20,000 standard cubic feet of hydrogen per ton of coal feed to the pipe-line. The pipeline is insulated to retain the heat fed in by the hot producer gas and also that liberated by the exothermic liquefaction reactions. At a point 3,000 feet downstream, corresponding to a residence time of ten minutes in the pipeline, one-third of the slurry is drawn off from the top of the pipeline and returned to the feed end to provide or augment the carrier fluid.
This initial 3,000 foot pipeline section is the liquefaction section or leg and is operated at a pressure of about 3,000 psi and a temperature throughout of about 435C. In an alternative embodiment a liquefaction leg of about 1500 feet could be used, corresponding to a residence time of 5 minutes, the reaction temperature being simil~r or higher. A further alternative would be . ~ , . : .. . : :
., ~ , .: ., :
~Z~ 3 a lique:Eaction leg of 6000 feet and a reaction temperature of 300C, corres ponding to a residence time of about 20 mimltes at this lower temperature. Of course, in each case the residence time of the recycle portion is effectively doubled as the material also passes through the recycle portion.
After the liquefaction section pressure let down occurs gradually as a result of natural frictional drag to the normal 1200 to 1600 psi pipeline operating pressure. The temperature is also permitted to fall in a gradual manner. During this period of gradually falling temperature and pressure the liquefaction reactions continue to completion in the presence of hydrogen and carbon monoxide gases. In this way, the effective residence time for reaction is increased greatly at no additional capital cost. If desired, second or third recycle legs can be inserted downstream to boost liquefaction or to reheat.
Process conditions in the pipeline can, of course, be varied depend-ing on the nature of the feed and the type of product desired. Generally, increasing the pressure and the hydrogen feed leads to more hydrocracking and a product distilling at a lower temperature. The pipeline slurry viscosity can also be reduced. If desired, catalysts can be added to obtain a specific effect. The range of possible process conditions is given in the following Table.
The ability to vary residence time at will without changing the throughput of the pipeline is an important advantage of the invention over the prior art. Previously, if the residence time was lengthened, throughput would be correspondingly reduced~ I`his is because the liquefaction reactor volume is fixed. In the process of the invention, the "reactor" volume is variable, in effect, over any desired length of the pipeline. Thus the invention is inherently more flexible in the treatment of different types of coal.
Another advantage of the ability to switch on demand to longer ~: ~....... : , 3fi~
residence times (i.e. larger reactor volumes~ and lower operating temperatures is that corrosive effects, e.g. from hydrogen attack on pipeline metal, are reduced. Moreover, operation at the lowest reactive temperature possible, with no loss of throughput because of the extended residence time is obviously one alternative available from the invention. This reduces wear and tear and plant material costs. Conventional plants must generally operate at high temperatures to get the fastest reaction and thereby maintain adequate through-put and also to save on reactor size.
POSSIBLE PIPELINE LIQUEFACTION CONDITIONS
r Process Parameter Range .
Coal in slurry ~% by weight) 35 to 50 Water in coal feed ~% by weight) 2 to 35 Recycle ratio ~volume) 1/4 to 3/4 Temperature (C) 200 or 250 to 500 Pressure (psi) 1200 to 5000 Hydrogen/Carbon Monoxide Ratio in Gas Feed 1/0 to 0/1 Hydrogen Feed Rate (s.c.f./ton coal~ 10,000 to 30,000 Pipeline velocity, feet/sec. 3 to ~
Length of liquefaction of leg (feet~ 600 to 6000 Residence time for liquefaction section ~minutes) 2 to 20 Under such conditions up to 95% of the coal can be converted to a liquid or gaseous fraction, with an oil yield of up to 60%. The difference between the conversion and the oil yield is due to the formation of hydro-carbon gases, methane, ethane, propane, etc., and carbon dioxide gas. Thus, the pipeline is carrying a mix of gases, oils and some residual solids. These , _ g _ ,."i, .:
.. : . : . .:~.. ..
:, , ~ :,; . :
- ~ , : . , , l~X~3~
can be separated and collected on discharge from the pipeline. Coal general-ly contains from 2.5% to 5.5% hydrogen by weight. Crude oil contains about 12% hydrogen by weight, and natural gas about 25%. The objective in coal liquefaction is to add hydrogen to the coal, either from hydrogen gas directly, or from steam, to bring the hydrogen content closer to that of oil. A liquid product of about 7% to 11% hydrogen is satisfactory, and to be expected.
The technique is applicable to coals of all ranks, from anthracite to lignite. It is particularly suitable for lignite since the water content of lignite can be used to promote the water gas shift reaction during the transmission of the lignite. Lignites also sometimes contain iron or alkali carbonates which contribute to the catalytic effect utilized in the hydrogena-tion reactions.
The invention is also applicable to other carbonaceous feed stocks, such as peat, wood, agricultural waste and municipal waste. Moreover, while the invention is particularly useful for the liquefaction of carbonaceous material, it is also applicable to the treatment of mineral ores and other solids, gases or liquids, during transmission in a pipeline. Examples include the microbial treatment of a mineral ore in a slurry of water and the cataly-tic conversion of natural gas to ethylene. The invention affords a particular-ly attractive route for exploiting reactions and processes requiring long residence times, wherever these can be combined with a bulk transportation need.
- lQ --.
. ~
`~ :
: .
Claims (12)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method for the simultaneous liquefaction of coal and transporta-tion thereof in a pipeline, which comprises: (a) feeding a slurry of par-ticulate coal in an oil carrier into and through an initial liquefaction section of a pipeline maintained under elevated temperature and pressure; (b) providing in said liquefaction section a source of hydrogen for reaction with said particulate coal to at least begin liquefaction thereof; (c) at a point downstream in said pipeline, separating a liquid fraction from the partially liquefied coal and recycling such fraction to said initial liquefaction section to provide a part or all of the oil carrier; (d) feeding the remain-der of the liquefied coal through the pipeline while allowing liquefaction to continue to completion with progressive let-down of pressure to a normal pipeline operating pressure; and (e) thereafter transporting the liquefied coal through the pipeline.
2. A method according to claim 1, wherein an operating pressure of about 1500 to 5000 psi and a temperature of about 250 to 500°C are maintained in the initial liquefaction section the feed velocity being from about 3 to 8 feet per second and the residence time being from about 2 to 20 minutes.
3. A method according to claim 2, wherein the operating temperature is about 325 to 425°C.
4. A method according to claim 1, wherein the coal slurry contains from about 35 to 50% by weight of coal.
5. A method according to claim 1, wherein from about 25 to 75% by volume of the slurry is recycled.
6. A method according to claim 5, wherein about one third of the slurry is recycled.
7. A method according to claim 1, wherein one or more additional re-cycle loops are provided downstream, with the recycled feed portion or portions optionally being reheated.
8. An apparatus for the combined liquefaction and transportation of coal, which comprises: (a) a pipeline including an initial liquefaction sec-tion adapted to carry a flow of coal-in-oil slurry and reaction gases under elevated pressure and temperature and downstream from said liquefaction section a transport section; (b) means for feeding a coal-in-oil slurry and reaction gases to the beginning of the liquefaction section; (c) a recycle section extending from the end of the liquefaction section back to or near the begin-ning of the liquefaction section for recycling a portion of the partially processed feed back to the beginning of the liquefaction section to constitute part or all of the oil carrier of said slurry; and (d) discharge means at the downstream end of said transport section for discharging liquefied coal and associated gases and solids.
9. An apparatus according to claim 8, wherein the pipeline is provided downstream with one or more additional recycle loops, optionally including additional heating means.
10. An apparatus according to claim 8, and including means for introduc-ing hot reaction gas at the downstream end of the liquefaction section.
11. An apparatus according to claim 8, wherein the length of the liquefaction leg is from about 600 to 6000 feet.
12. An apparatus according to claim 10, wherein the liquefaction leg is about 3000 feet in length.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US2574679A | 1979-03-30 | 1979-03-30 | |
| US25,746 | 1979-03-30 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1129360A true CA1129360A (en) | 1982-08-10 |
Family
ID=21827839
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA348,025A Expired CA1129360A (en) | 1979-03-30 | 1980-03-20 | Pipeline liquefaction of coal and other carbonaceous material |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1129360A (en) |
-
1980
- 1980-03-20 CA CA348,025A patent/CA1129360A/en not_active Expired
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