JPH047399B2 - - Google Patents

Description

[Detailed description of the invention]

BACKGROUND OF THE INVENTION This invention relates to drying and deoxidizing coal by heating the coal in hot slurry oil, and in particular to drying and deoxidizing coal in a coal slurry before feeding the slurry to a coal liquefaction process. ℃
It relates to a method of drying and deoxidizing at a temperature of (350-650〓). In the coal liquefaction method, the coking coal is first crushed and dried to remove surface moisture and contained moisture, reducing the residual moisture to less than 3% by weight. At this time, the coal is passed through a drying tunnel using sensible heat. It is common to use . Coking coal also typically contains some undesirable oxygen.
The main disadvantage when the coal feed to the liquefaction process has a high oxygen content is that the oxygen combines with the expensive hydrogen to produce commercially worthless water. Oxygenated compounds contained in hydrocarbon liquid products from coal liquefaction processes are also undesirable as liquid transportation fuels. Oxygen compounds also contribute to retrograde reactions to produce insoluble organic materials that do not react. Schafer, in Fuels Vol. 59, May 1980, pp. 295-304, reports that coal dried by a pyrolysis operation is decarboxylated under high temperature conditions, that is, COOH (carboxyl groups) are separated. produces carbon dioxide, carbon monoxide and water. For each molecule of carbon dioxide produced, one molecule of tightly bound water is also lost from the drying coal. The effect of bound water and carbon dioxide is greater on lower grade coals because they contain more carboxyl groups and therefore more water than higher grade coals. The physical and chemical properties of lower grade coals and their response to coal liquefaction processes are believed to be adversely affected by the presence of tightly held water and carboxyl groups in the coal. These oxygen-containing species reduce the hydrogen partial pressure and coal conversion in the coal liquefaction reactor, increase hydrogen consumption, affect diffusion properties, and increase the need for separation and disposal, thus reducing coal liquefaction. It is known to have an adverse effect on the economy of the method. In the direct coal liquefaction process, particulate coal and hot slurry oil are blended using a temperature-controlled mixing tank. The slurried oil is normally removed from the process and then treated to remove gas, moisture and light naphtha.
Cool before recycling to slurry stage. Weber, in US Pat. No. 4,209,911, discloses a method for drying coal in a slurry mixing vessel prior to coal liquefaction. However, Weber does not disclose any deoxidation of the coal or increased reactivity of the slurry at more severe drying conditions as provided by this invention. SUMMARY OF THE INVENTION The present invention provides a method for drying and deoxidizing coal in a coal-oil slurry mixing tank maintained at an elevated temperature. The present invention provides a process for drying and deoxygenating granular coal to remove moisture and oxygen contained therein, by mixing a feed granular coal with a hydrocarbon slurry oil in a mixing zone to obtain an oil of about 1.2 to 2.5 ml. providing a coal-oil slurry mixture having a weight ratio of /coal;
The coal-oil slurry mixture was heated to 177-343°C (350°C
Drying and desorption of a coal slurry comprising heating to a temperature of ~650㎓) to generate moisture and oxygen vapor from the coal; and recovering a dry coal-oil slurry mixture having reduced moisture and oxygen content. Oxygen method. By using this invention, the water and oxygen content of a coal slurry is reduced and the relative reactivity of coal slurries containing bituminous and lower subbituminous coals and similar organic deposits is reduced. The slurry temperature is increased by increasing the temperature of the slurry to at least about 177°C (350°) and usually no more than 343°C (650°). The remaining moisture in the heated coal-oil slurry is approximately 3% by weight.
The oxygen content is reduced to less than about 7% by weight. A more reactive slurry is also obtained which produces a higher hydrogen partial pressure within the reactor and increases the total conversion of coal to product oil. For a given total reaction pressure, the present invention can improve product quality and reduce the energy required to cool the recycle stream. This drying and deoxygenation stage of the coal is usually carried out in a single mixing tank, but two or three stage mixing tanks can be used at increasing temperatures and pressures if desired. Although this coal drying and deoxygenation step can be used to obtain a dry coal-oil slurry stream for fuel use, it is preferably used as a pretreatment step for the coal feed stream to the coal liquefaction process, and is preferably used as a pretreatment step for the coal feed stream to the catalytic coal liquefaction process. It is further preferred to obtain a feed stream. Therefore, when this coal drying and deoxygenation step is used in a coal liquefaction process, it reduces H ₂ consumption, increases coal conversion, improves product quality, reduces the energy required for cooling the recycle stream, and thus directly Intended to improve the economics of liquefaction or lignin quality improvement. Similar benefits may be expected when processing coal containing higher concentrations of mineral matter and clay water by reducing or eliminating condensation reaction products caused by the generation of steam vapor from the clay. be done. DESCRIPTION OF THE INVENTION The invention will be further described as a coal pretreatment step in a coal liquefaction process. FIG. 1 shows a process diagram of a method for drying and deoxidizing a coal-oil slurry according to the present invention. As shown in FIG. 1, raw coal from 10 is crushed or ground and sieved in a crushing and sizing stage 12 to obtain a particle size range of 30-375 mesh (US sieve series). If desired, the coal may also be cleaned or beneficent to remove mineral matter. then 1
3, supplying the granular coal to the slurry mixing tank 14,
Here the standard boiling point range is about 260~399℃ (500~750〓)
and a hydrocarbon slurry oil 16 having the following properties.
The pressure in the vessel is determined by a portion of the recirculated gas stream derived from the process from 0 to 10.5 Kg/ ^cm2 Gauge (0 to 150 psig), preferably from 0 to 3.5 Kg/ ^cm2 Gauge (0 to 50 psig).
Maintain pressure. Mixing tank 1 with 13 granular coals
4 can be fed via a conventional pressurized lock hopper or via a screw or star feeder (not shown in the drawings). Effective mixing of the granular coal and slurried oil is carried out in tank 14 at least about 0.6 m/sec (2 ft/sec).
This is done by giving a liquid velocity of sec). The coal and oil in an atmospheric or pressurized mixing tank are mixed using an agitator or mixer, a sill board and a recirculating circuit or similar mechanical device that provides a well-mixed coal-oil slurry. can be mixed together. Such mixing may be carried out by a rotary mixer 15 installed in a tank, or by a part 1 of the slurry flow 17.
7a by recirculation to the tank by pump 18, or by means of both devices. The temperature of the slurry in the mixing tank 14 is usually about 288 to 371.
121-343℃ (250-650〓) by recirculating the thermal slurry oil 16 at a temperature of ℃ (550-700〓)
maintain it. Slurry tank temperature is 177~260℃ (350℃)
~500〓) is preferable. The vessel 14 typically includes an outer insulation 14a to retain heat and help maintain the desired internal slurry temperature. The residence time of the coal in the tank 14 depends on the moisture content of the fed coal and the desired degree of dryness, but typically ranges from about 0.2 hours at a high drying temperature of 343°C (650°C) to about 121°C (250°C) with high moisture content.
〓) at a low drying temperature of up to about 3 hours. Longer residence times can be used for process control purposes if desired. A vapor stream containing evolved moisture and oxygen is removed at 19. The resulting coal/oil slurry mixture of 17, which has a significantly reduced moisture and oxygen content, is pressurized at 20 and sent as stream 21 to a coal liquefaction step 24. Temperature-controlled slurry mixing tank 14 for direct coal liquefaction coal and recirculated slurry oil at 121-343℃
It operates at temperatures of (250-650〓) and pressures of 0-10.5 Kg/ ^cm2 gauge pressure (0-150 psig). If desired, any fine inorganic solids that settle in the slurry mixing tank, such as clay solids minus water, can be recovered independently from the tank 14 at the drain line 14b. Such recovery is facilitated by providing the tank with a tapered bottom to allow collection of this type of fine sediment. Whenever the pressure in the slurry mixing vessel 14 is at or near atmospheric pressure, the steam generated from the vessel is removed at 19 by an eductor device and a gas, oil and water recovery system (not shown).
can be sent to. The dried and deoxygenated slurry from the mixing tank 14 is then typically passed through a preheater 22 to a coal liquefaction step 24, which can be either a contact or non-contact process.
send to In this process, the reacted effluent material is divided into a top stream and a bottom stream, with the top material being recycled into gas and
Separated into naphtha and distillate fractions. Bottoms isothermally 3.5-10.5Kg/cm ² gauge pressure (50-150psig)
and sent to a liquid-solid separation stage, such as by a hydrocyclone device. 25 gas flow
A soft hydrocarbon liquid product is recovered at 26 and a heavy hydrocarbon liquid product is recovered at 27. 121~343℃
The liquid stream having a temperature of (250-650〓) is recycled to the slurry tank 14 as coal slurry oil.
Although the coal-oil mixing vessel can normally be sufficiently heated by recirculating the hot outflow of the hydrocyclone as stream 16, additional heat from such things as electric heaters may be used for process start-up purposes. It can be supplied as needed. A portion of the recirculated gas is flushed at the pressure of the mixing tank prior to pressurizing the coal hopper and mixing tank. Although the coal drying and deoxygenation stages are usually or preferably carried out in a single mixing vessel, two or even more stage vessels may be used, each operating at conditions of increasing temperature and pressure. The coal-oil slurry from the first mixing tank is pumped to the next tank for further heating, and the steam stream generated from the tank is sent to a recovery system (not shown). The thermal drying step of the coal-oil slurry is preferably used in the catalytic coal liquefaction process as shown in FIG. In this preferred embodiment, raw coal is pulverized and sized in the same manner as in FIG.
to be introduced. The heated coal-oil slurry is pumped from the thermal slurry mixing tank 14 by the pump 20 to 35 to 352
Pressurized to high pressure such as Kg/cm ² (500~5000psi),
It then passes through a preheater 22 to a reactor 30 having a catalyst bed 32. Recycled hydrogen at 28 can be reheated at 29 and optionally combined with fresh make-up hydrogen and fed to reactor 30, or can be sent separately to heater 22 as stream 28b. The coal-oil slurry and hydrogen stream are then passed through the catalyst bed 3.
2, and uniformly flows upward from the bottom through the baffle plate 31 under flow rate, temperature and pressure conditions that achieve the desired hydrogenation reaction. floor 3
The catalyst in No. 2 comprises a metal selected from the group consisting of cobalt, iron, molybdenum, nickel, tin, and other hydrocarbon hydrogenation catalyst metals known in the industry, such as alumina, magnesia, silica, and similar materials. The catalyst must be selected from a group of catalysts deposited on a selected substrate. In addition, the particulate hydrogenation catalyst processes approximately 0.045 catalysts per ton of coal.
0.1 to 3.0 lbs. can be added to reactor 30 via connection 33. flowing a liquid and a gaseous substance in cocurrent upwardly through a reactor having a bed of said specific catalytic solid particles;
By expanding the solid particle bed by at least about 10% above its pile height, typically by 20-100%,
The solid particles are brought into random boiling motion by an upwardly flowing flow within the reactor. The characteristic of an ebullated bed at a certain degree of volumetric expansion is that as the finer, lighter solid particles move upward through the catalyst bed, the contact particles forming the effervescent bed are retained in the reactor and the finer, lighter solid particles move upward through the catalyst bed. The substance is passed through the reactor. The level 32a above the catalyst bed above which very few contact particles rise is the level above boiling. Generally, the total density of the catalyst mass is about 400~3204Kg/
m ³ (25-200 b/ft ³ ), the upward flow rate of liquid is approximately 204-4889 m ² (ft ² ) of the horizontal cross-sectional area of the reactor.
per minute (5 to 120 gallons per minute), and the expanded volume of the ebullated bed is usually no greater than twice the volume of the settled mass. In order to maintain the desired superficial rising liquid velocity in the reactor, the reactor 3 is removed from above the level 32a above the boil via a downconduit 34 and a pump 35.
It is common to recirculate a portion of the liquid slurry to the reactor, such as recirculating the liquid to the bottom of the reactor and then upwardly through the baffle plate 31. Spent catalyst can be removed by withdrawal in connection 36 to maintain the desired catalyst activity within the reaction zone. The operating conditions of the reactor are 371-499℃ (700-930℃
〓) temperature and hydrogen partial pressure of 70-352Kg/ ^cm2 (1000-5000psi), preferably 399-482℃ (750-900〓)
and maintain a wide range of hydrogen partial pressure from 70 to ^281Kgcm2 (1000 to 4000psi). Coal throughput or space velocity is 160-2403Kg coal/hour/reactor volume
m ³ (10-150 lbs coal/hour/reactor volume
^ft3 ), the yield of unconverted coal obtained as char is about 4 to 10% of the anhydrous ashless coal fed.
% by weight. The relative sizes of the coal and catalyst particles and the boiling conditions are such that the catalyst is retained in the reactor, while the ash and unconverted coal or coal particles are carried away with the liquid reaction products. An effluent stream 37 substantially free of solid catalyst particles is recovered from the reactor 30, cooled at 38, and then sent to a phase separator 40. From separator 40, a soft gas fraction stream is removed at 41 and sent to a hydrogen purification stage 42.
A medium purity hydrogen stream 43 is recovered from the purification stage 42;
It is recycled as stream 28 via heater 29 to reactor 30 where it supplies a portion of the required hydrogen as heated hydrogen stream 29a. A liquid vertical stream 44 is recovered from the separator 40 and 45
The pressure is reduced by , and the mixture is sent to a phase separator 46 . The separator operates at near atmospheric pressure and temperatures of 500-650°C to permit the removal of a light hydrocarbon liquid stream at 47 and a heavy hydrocarbon liquid stream at 48. Stream 47 contains naphtha and light distillate fractions and is sent to fractionation stage 50 where hydrocarbon gas products are recovered at 51 and light distillate products are recovered at 52. Hydrogenated coal liquefaction fraction 48 typically has a normal boiling point range above about 288°C (550°), preferably 316-510°C (600-950°) and contains asphaltenes, pre-asphaltenes, unconverted coal and solid ash. This fraction 48 is passed through a liquid-solid separation stage 5 such as a number of hydrocyclones.
Send to 4. Stream 260℃ ⁺ (500〓
⁺ ) Remove the liquid stream at 56. Portion 57 of liquid stream 56
is sent to the fractionating column 50, the remaining 58 is pressurized to the reactor pressure at 59, and the necessary slurry oil is supplied to the slurry mixing tank 14. The descending liquid stream 62 of separation stage 54, which has increased solids concentration, is removed and sent to vacuum distillation at 64. The overhead liquid 65 obtained from the vacuum still is combined with stream 66 to provide a heavy distillate product stream 68. If desired, a portion of stream 68 can be used for slurrying oil 16. Also, if desired, at least a portion 67 of stream 66 can be sent to vacuum distiller 64.
The heavy vacuum bottoms stream 69, which contains some asphaltenes, breasphaltenes, and unconverted coal and solid ash, is either coked to recover the oil product or gasified to produce make-up hydrogen required for the process. can be further processed. The invention will be further illustrated by the following examples, which are not intended to limit the scope in any way. Comparative Example 1 Wyodak sub-bituminous granular coal having a particle size of 50-325 mesh (US sieve series) and containing 10-25% water by weight was heat recycled from a coal liquefaction process unit to a tank. The slurry was fed into a slurry mixing vessel maintained at a temperature range of 110-121°C (230-250°) by hydrocarbon slurry oil. The initial moisture in the feed coal varies between 11 and 17.5% by weight;
The residence time of the coal in the slurry tank was approximately 2 hours, and most of the water contained in the supplied coal evaporated from the tank as steam. The average results of the slurry tank drying operation over several days are shown in Table 1.

[Table] Water, weight%
These results show that even at a moderate slurry mixing tank temperature of 111-119°C (232-246°C), the initial
~42~ from feed coal containing ~17.5% moisture by weight
This indicates that 52% of water was removed, resulting in dry coal with a water content of approximately 4.4 to 6.2% by weight. This dry coal-oil slurry feedstock is suitable as a feed stream for a coal liquefaction process. Example 1 A similar slurry mixing vessel study of coal deoxidation was conducted, where the slurry consisted of Wyodac coal containing 17-20% by weight oxygen mixed with recirculated oil obtained from Wyodash coal. . Coal-oil slurry in autoclave at 177-260℃
(350-500〓) and then analyzed. Figure 3 shows the results of coal deoxidation and the relationship between conversion and slurry tank temperature. As the slurry bath temperature increases from approximately 121°C (250〓) to 260°C (500〓), an increase in coal deoxidation and decarboxylation occurs and the treated slurry obtains an increase in coal conversion. It is noteworthy that the reactivity was relatively higher. It is thought that a more reactive slurry was produced due to the loss of carboxyl groups and water molecules contained in the coal. It is believed that a more reactive slurry for direct coal liquefaction not only increases coal conversion, but also favorably changes the yield distribution to produce a lower boiling hydrocarbon liquid fraction. Also, the hydrogen partial pressure within the hydrogenation reactor will increase due to carbon dioxide and water molecules being lost in the slurry mixing tank instead of remaining in the reactor feed stream. Example 2 Recycled oil and oil/oil obtained from Illinois No. 6 bituminous coal initially containing about 10% water by weight and having a particle size range of 50 to 200 mesh (US sieve series)
The coal weight ratio was mixed in the range of 1.6 to 1.8. The recirculating oil temperature was 232-316°C (450-600°C). The initial mixing of coal and oil is at 71~93℃ (160~200〓) in the tank.
at a temperature of 3 hours with an average residence time of 3 hours to produce a slurry source and remove most of the moisture from the coal. The resulting coal/oil slurry was then transferred to a second mixing vessel maintained at a constant slurry height and maintained at 232°C (450°C) by an electric heater with an average residence time of 1.9 hours. Residual oxygen contained in the coal was generated in a second mixing vessel and the steam stream containing moisture and oxygen was removed. The resulting coal/oil slurry stream with reduced moisture and oxygen content was collected from the lower end of the vessel. The reactivity of the heated coal-oil slurry was determined by microautoclave analysis. Coal-oil slurry samples were taken before and after treatment in the thermal slurry mixing tank,
The slurry material is then placed in a micro autoclave.
Thermal reaction was carried out at 454°C (850°C) for 30 minutes. The resulting reactants were then extracted independently with cyclohexane, toluene, and tetrahydrofuran (THF). The results are shown in Table 2.

[Table] In the above results, the temperature of the slurry mixing tank is 232
It is noted that an increase in slurry reactivity occurred with an increase in temperature to 450 °C. in this way,
The solubility and reactivity of the coal/oil slurry was increased as evidenced by the increased conversion of coal obtained under otherwise identical reaction conditions. Example 3 Illinois No. 6 bituminous coal as in Example 2 was mixed with a hydrocarbon liquid obtained from coal, ie, slurried oil, at an oil/coal weight ratio ranging from 1.6 to 1.8. The temperature of the recirculated oil was 232-316°C (450-600°C). Initial mixing of granular coal and oil at 71~93℃
The experiment was carried out in a tank at a temperature of (160 to 200 °C) and an average residence time of 3 hours for the coal. The resulting mixed coal/oil slurry is then heated to an internal mixing temperature of 232°C using an electric heater.
℃ (450〓), and the average internal residence time of the coal is
The mixture was transferred to a second mixing tank for 1.9 hours. The moisture and oxygen originally contained in the coal were generated in a second slurry mixing vessel and the steam stream containing moisture and oxygen was removed. The resulting coal/oil slurry with reduced moisture and oxygen content was recovered from the vessel and sent to a bench scale coal catalytic hydrogenation process. The operating conditions of the process and the results obtained are also shown in Table 3 and FIG.

【table】

[Table] Weight% of charcoal
The slurry mixing tank temperature was kept at 121℃ during 8 days of operation.
(250〓) to 232℃ (450〓),
It is noted that the yield of the 204-524°C (400-975〓) fraction increased from 31.6 to 35.8% by weight as shown in Table 3. Also during this time, the residual oil product yield (524°C ⁺ (975〓 ⁺ ) fraction) decreased from 14.6 to 10.8% by weight of the dry coal feed under otherwise identical operating conditions. Also, the decrease in CO and CO ₂ in the product yield obtained by liquefaction through higher slurry mixing tank temperatures indicates that the amount of oxygen removed from the coal in the hot slurry mixing tank has increased. This decrease in residual oil yield with increasing slurry mixing tank temperature is further illustrated in FIG. Example 4 Initially containing about 14-17% water and 17-19% oxygen by weight, 50-200 mesh (US sieve series)
Wyodak subbituminous coal with particle size of was mixed with oil obtained from the coal in liquefaction and hydrogenation process.
The temperature of the oil used was 232-316°C (450-600°C) and the oil to coal weight ratio was 1.5-1.6. The coal/oil mixture was kept at a temperature of approximately 232°C (450°C) using an electric heater, giving an average coal residence time of 1.9 hours. The moisture and oxygen contained in the coal were generated in a mixing tank and the steam stream containing moisture and oxygen was removed.
The resulting coal/oil slurry with significantly reduced concentrations of both moisture and oxygen was recovered from the thermal slurry mixing tank and fed to a coal liquefaction process for producing hydrocarbon liquid products, where the temperature of the conventional slurry mixing tank was 93°C.
The required hydrogen consumption is reduced compared to the liquefaction method with 121°C (200-250〓).

[Brief explanation of drawings]

Figure 1 is a process diagram of the coal-oil slurry drying and deoxidizing method according to the present invention, Figure 2 is a process diagram of the coal-slurry drying stage operated upstream of the catalytic coal liquefaction process, and Figure 3 is the slurry tank temperature. Figure 4 shows the decrease in the yield of residual oil (524°C ⁺ (975〓 ⁺ ) fraction) from the coal hydrogenation process as the slurry mixing tank temperature increases. This is a graph showing. 12... Grinding and sizing stage, 14... Slurry mixing tank, 14a... Outer heat insulation part, 15... Rotating mixer, 18... Pump, 20... Pump, 22...
Preheater, 24... Coal liquefaction process, 29... Heater, 30... Reactor, 31... Straightening plate, 32...
...Catalyst bed, 33...Connection, 34...Down conduit, 3
5...Pump, 36...Communication, 38...Cooler,
40... Phase separator, 42... Hydrogen purification stage, 46
... Phase separator, 50 ... Fractionation stage, 54 ... Liquid-solid separation stage, 64 ... Vacuum distiller.

Claims (1)

[Claims] 1. A method for drying and deoxidizing granular coal to remove moisture and oxygen contained therein, including: (a) first supplying granular coal containing 5 to 30% by weight of moisture; Hydrocarbon slurry oil and 0-10.5
Kg/cm ² Gauge pressure (0 to 150 psig) by mixing in a mixing zone maintained at a pressure of approximately
(b) converting the coal-oil slurry mixture into a slurried oil having a temperature of 260-357°C (500-675〓) obtained from a coal liquefaction process; and 177 to 343℃ (350
~650〓) to generate moisture and oxygen from the coal; and (c) a dry, deoxygenated coal-oil slurry mixture containing less than about 3.0% moisture and less than about 7% oxygen by weight. A method for drying and deoxidizing coal slurry, comprising the steps of recovering. 2. The method of claim 1, wherein the feed coal has a particle size of 30 to 375 mesh (US sieve series). 3. The method of claim 1, wherein the slurried oil contains at least about 10% by weight particulate solids consisting essentially of unconverted coal and mineral matter. 4. The method of claim 1, wherein the inorganic solids are recovered independently from the mixing zone. 5. The method according to claim 1, wherein the feed coal is bituminous coal containing 5 to 15% by weight of water. 6. The method according to claim 1, wherein the feed coal is subbituminous coal containing 10 to 30% by weight of water. 7. The method according to claim 1, wherein the feed coal is lignite containing 15 to 35% by weight of water. 8. The method of claim 1, wherein the coal-oil mixing is sufficient to produce a liquid velocity within the mixing zone of at least about 2 ft/sec. 9. The method of claim 1, wherein the coal residence time in the mixing zone is about 1 to 3 hours. 10. The method of claim 1, wherein the hydrocarbon slurried oil is at least in part hydrocyclone overhead liquid recycled from the coal liquefaction step. 11. Feeding the heated coal-oil slurry mixture to a coal liquefaction process, where the temperature of the coal-oil slurry mixture is from about 110-121°C (230-250〓) to about 177-343°C (350-650〓). 2. The method of claim 1 for increasing the conversion of feed coal to hydrocarbon liquids and gaseous products in a coal liquefaction process by increasing the liquefaction rate.