JPH0435518B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of Commercial Application] This invention relates to an improved method for liquefying hydrous coals, including through-air drying of hydrous coals. [Prior Art and Problems to be Solved] Coal is generally used as fuel or for various other purposes, either as it is or after liquefaction treatment. In this case, the mined coal is usually used after removing the ash or dewatering it to improve energy efficiency. In terms of efficiency, it is preferable to reduce the size of coal particles and wash the ash to remove ash, but since water is usually used in coal washing, a large amount of water adheres to the coal after washing, causing certain types of problems. Coal has a moisture content of over 20% by weight. Additionally, some types of lignite have a moisture content of 20 to 70% by weight. Methods for drying such coal include (1) flash drying method;
Drying methods such as (2) drying in oil and (3) pressurized steam method are known. The flash drying method is currently widely used, but there is excess oxygen remaining in the hot air obtained by mixing air and fuel, and the temperature of the hot air is usually mixed. oxidized,
In addition, some of the volatile components are decomposed, gasified, and dissipated. Oxidized coals continue to oxidize even at room temperature and are more likely to spontaneously ignite, requiring huge costs for coal storage equipment. Furthermore, if coal liquefaction is performed using coal dried by the conventional flash drying method as a raw material, the product yield will decrease and the amount of hydrogen consumed will increase, which is very economically disadvantageous. In principle, the drying in oil method and the pressurized steam method can dry coal without oxidizing it, but in both conventional methods, the water content of the coal after dehydration is around 10% by weight. . Therefore, when liquefying these coals, the equipment becomes huge as the net supply of coal decreases, and the hydrogen partial pressure inside the reaction tower, which greatly affects the liquefaction reaction, decreases due to the presence of water vapor. This requires higher pressure. Furthermore, since the water separated by this method contains a large amount of water-soluble organic compounds such as phenols, cresols, and humic acid, the cost for treating this separated water increases. Similar treatment of separated water is required in the flash drying method that has been developed in recent years. This invention can prevent oxidation of coal,
The present invention aims to provide a method for liquefying hydrous coal that can prevent an increase in hydrogen consumption during liquefaction and also prevent a decrease in liquefaction rate. [Means for Solving the Problems] The method for liquefying hydrous coal of the present invention involves drying hydrous coal by contacting it with hot air at a temperature of 200°C or less,
The method is characterized in that the dried coal is then heated in a solvent under hydrogen pressure to form a coal solution. Furthermore, this invention removes some moisture still remaining in coals from which most of the moisture has been removed by air drying by heating in a solvent and separating it into a steam phase and a coal slurry phase, It is also characterized in that the coal slurry is then heated under hydrogen pressure to form a coal solution. In this invention, by limiting the temperature of the hot air brought into contact with the hydrous coal to 200°C or less, the temperature of the dried material is maintained at 150°C or less, and even if oxygen is present in the airflow, the coal is oxidized. It is possible to prevent a change in the composition thereof, and therefore a decrease in the liquefaction rate can be prevented. When the temperature of the air stream exceeds 200°C, the composition of the coal changes and the liquefaction rate decreases. Preferred hot air stream temperatures are within the range of 50-190°C. The coal used in this invention has a low moisture content.
10% by weight or more of coking coal, non-caking coal, dry coal, lignite,
and grass charcoal, but in particular dry charcoal can be easily dried and liquefied by the method of the present invention without causing a change in composition. After most of the water is removed and dried through ventilation drying, the water content in the coal is 5.
~15% by weight. However, in order to further dehydrate this coal, aerated drying requires a long time and is not efficient. In this case, after adding a solvent to the dried coal and making it into a slurry, the resulting coal slurry is heated to 100 to 300 ml under pressure or under normal pressure.
Dehydration can be carried out by raising the temperature to a temperature within the range of °C, introducing it into a gas-liquid separation tank, and separating it into a steam phase and a coal slurry phase. When dehydrating coal slurry by heating it under pressure, first use a pump or the like to pressurize it to a pressure higher than the saturated water vapor pressure at the heating temperature, but if the pressure is increased too high, the pressure resistance of the equipment will increase. Since the necessity arises and economical efficiency deteriorates, it is preferable to use a pressure near the saturated steam pressure or a pressure higher than the saturated steam pressure by about 10 kg/cm ² . After pressurizing with a pump or the like, the coal slurry is passed through a heating furnace and heated to the required temperature. When the heating temperature of coal slurry exceeds 300°C, its saturated steam pressure also increases significantly, making it necessary to similarly increase the pressure resistance of the entire equipment before and after the heating furnace, resulting in economical issues. Because of this disadvantage, the heating temperature is usually set at 300°C or lower. However, coal cannot avoid thermal decomposition at temperatures above 200°C, and as a result of thermal decomposition, cracked gas containing carbon dioxide and other gases is generated. When thermal decomposition of coal is promoted in this way, cracked gases such as carbon dioxide that should be generated in the liquefaction reaction zone are separated and removed in advance in the hydrogenation reaction. This prevents a decrease in the hydrogen partial pressure, which is the most important factor, and increases the liquefaction rate of coal. Therefore, the heating temperature of the coal slurry is preferably within the range of 200 to 300°C. After heating, the coal slurry is depressurized and introduced into a gas-liquid separation tank, where the steam phase and coal slurry phase are separated and dehydrated. When the coal slurry is dehydrated by heating under normal pressure, if the heating temperature is 200°C or higher, the evaporation of the solvent will be promoted at the same time, so the heating temperature is preferably within the range of 100 to 200°C. In the case of normal pressure heating dehydration, water completes evaporation during passage through the heating furnace, and rapidly separates into a steam phase and a coal slurry phase in a gas-liquid separation tank. According to this coal slurry dewatering method, there is no risk of oxidation of the coal and the process is carried out within a relatively high temperature range, so that highly efficient dewatering of coal with a low moisture content is possible, particularly within a short time. Therefore, a combination of aerated drying at low temperatures and a coal slurry dehydration method can provide an excellent dehydration method both process-wise and economically.
Outstanding practical effects will be produced. The solvent used for coal liquefaction is hydrocarbon oil with a boiling point of 180°C or higher, such as coal dry distilled tar or its fraction, petroleum heavy oil with a boiling point of 200°C or higher,
These are coal decomposition product oil produced in the coal liquefaction process, hydrogenated products of these solvents, or mixtures thereof. Furthermore, coal slurry after dehydration and a coal solution containing solids from which gas has been separated in the coal liquefaction process may also be used as the solvent. When drying in oil, ie, through-air drying is performed without coal slurry dehydration, the dried coal is made into coal slurry by adding a solvent and, if desired, a catalyst. The weight ratio of the solvent to the dry coal in this coal slurry or in the coal slurry subjected to the above-mentioned in-oil drying treatment is preferably 1:0.1 to 0.5, particularly preferably 1:0.15 to 0.4. The temperature during preparation of the coal slurry is preferably 100° C. or lower to prevent bubble generation. Oxides, hydroxides, sulfides, and their reduction products of iron, molybdenum, cobalt, nickel, aluminum, silicon, etc. are used as catalysts for liquefaction, and the amount added is 2 to 5% by weight of dry coal. . The slurry containing dry coal is then heated under hydrogen pressure to cause depolymerization and dissolution of the coal, resulting in liquefaction. The hydrogen partial pressure is preferably 30 atm or more, particularly preferably within the range of 70 to 300 atm. The reaction temperature is preferably within the range of 300 to 500°C, particularly preferably within the range of 400 to 490°C. The reaction time is preferably 10 to 120 minutes. The resulting reaction mixture contains hydrogen, lower hydrocarbons,
It is separated into a gas mixture such as carbon dioxide and hydrogen sulfide and a coal solution. This coal solution is separated from insoluble substances such as undissolved coal and ash, and subjected to distillation to separate into a coal liquefaction product that is liquid at room temperature and a coal liquefaction product that is solid at room temperature. According to this invention, as is clear from the examples, drying of hydrous coals is carried out without any substantial change in the composition of the coals, and the conversion rate and product yield of coal during coal liquefaction are also improved. It is not substantially different from that of dry coal obtained by vacuum drying raw coal. Furthermore, since the water content in dried coal is less than 5% by weight, it is suitable for use in the coal liquefaction process, and even when drying in oil is combined, most of the water is removed by air drying. The amount of separated water is small, and its treatment is not a big problem. [Description with Drawings] Hereinafter, one embodiment of the present invention will be described with reference to the accompanying drawings. Hydrous coal is supplied to the ventilation dryer 2 through line 1 . On the other hand, air as a drying air stream from the line 15 is heated by the heater 16 to a temperature of 200°C or less, preferably within the range of 50 to 190°C, and is supplied to the ventilation dryer 2, where it is combined with hydrous coal. Contact and dry the hydrous coal. Further, carbon dioxide supplied through a line 17, which will be described later, may be used by appropriately mixing it with the air of the drying air stream. Various types of ventilation dryers 2 are used, such as a fixed bed type, a moving bed type, a rotary dryer, a fluidized dryer, and a flash dryer. Dry coal with a moisture content of 5 weight or less leaving the ventilation dryer 2 is introduced into a slurry preparation tank 4 and is passed through line 1.
Mixed with circulating solvent from 4 and liquefaction catalyst, 100
A coal slurry is prepared at a temperature below .degree. The weight ratio of solvent to dry coal is particularly 1:0.15~
0.4 is preferred. Examples of liquefaction catalysts include iron,
Oxides, hydroxides, or sulfides of molybdenum, cobalt, nickel, aluminum, silicon, etc., or reduced products thereof, are preferably used in the range of 2 to 5% by weight of the dry coal. If it is desired to further reduce the water content in the coal, the slurry is sent to the heater 27 of the dehydration equipment using a slurry pump that supplies the coal to the dehydration equipment, and heated to a required temperature. When heating under pressure, the slurry temperature should be within the range of 200 to 300°C, and the pressure should be about 10 kg/cm ² higher than the saturated water vapor pressure at that temperature. Moreover, when heating under normal pressure, the slurry temperature is within the range of 100 to 200°C. The heated slurry is introduced into a gas-liquid separation tank 28, and the water mixed in the slurry is removed through a line 29 in a gas phase. The slurry dehydrated in the gas-liquid separation tank 28 is sent to the heater 5 by a slurry pump, and the subsequent processing is the same as in the case of dewatering only by ventilation drying, and coal liquefaction is carried out. When this in-oil drying method is not used, the slurry produced in the slurry preparation tank 4 is transferred from the slurry preparation tank 4 to the heater 5 by a slurry pump.
directly introduced into the On the other hand, hydrogen is supplied from lines 21 and 26 to the heater 5, the inflow to the heater 5 being particularly preferably at a pressure in the range from 70 to 300 atm and at a temperature in the range from 400 to 300 atm.
It can be heated to a temperature within the range of 490℃. The slurry heated and heated by the heater 5 is
The coal is allowed to remain in the reactor 6 for a period ranging from 10 to 120 minutes, during which depolymerization of the organic substances in the coal, dissolution in the solvent and hydrogenation reaction take place. This hydrogenation reaction is promoted by a liquefaction catalyst added to the slurry. The reaction mixture leaving the reactor 6 separates the gaseous product consisting of carbon dioxide, hydrogen sulfide and lower hydrocarbons produced in the gas-liquid separator 7, as well as unreacted hydrogen, from the liquid product. The separated gaseous phase portion is sent via line 8 to gas separation facility 18 where lower hydrocarbons, carbon fluoride and hydrogen sulfide are each separated from unreacted hydrogen by known means. A portion of the lower hydrocarbons is sent via line 19 to hydrogen production facility 20 where it is converted to hydrogen by steam reforming. This amount of hydrogen corresponds to the amount of hydrogen consumed by the reaction. The hydrogen produced in the hydrogen production facility 20 is
It is introduced into the heater 5 through a line 21 along with hydrogen that is separated in the gas separation facility 18 and returned to the heater 5 through a line 26 . The remaining lower hydrocarbons are discharged from the system through line 23 and used for various purposes. In the hydrogen production facility 20, hydrogen may be produced by partially oxidizing a mixture of coal and residue from the line 11, which will be described later. The carbon dioxide separated in the gas separation facility 18 can also be sent to the heater 16 as a drying air stream through the line 17 and mixed with the air supplied through the line 15 for use. Further, hydrogen sulfide is discharged to the outside of the system via line 22. The liquefied product separated in the gas-liquid separator 7 is sent to the solid-liquid separator 10 via a line 9, where insoluble substances such as undissolved coal and ash are separated from the coal solution consisting of the coal liquid product and the solvent. . Solid-liquid separators include filters, centrifuges,
Liquid cyclones are used. The separated solid residue is discharged from the system via line 11 or used for hydrogen production as described above. On the other hand, the coal solution passes through line 12 to distillation column 13
where it is separated into a solvent, a liquid product that is liquid at room temperature, and a still residue that is solid at room temperature. The separated solvent is returned to the slurry preparation tank 4 via a line 14 as a circulating solvent. The liquid product, which is liquid at room temperature, and the distillation residue, which is solid at room temperature, are removed via lines 24 and 25, respectively. [Examples] This invention will be further explained below with reference to Examples, but the invention is not limited thereto. Example 1 A Drying of hydrated coal Morwell dry coal having the following analytical values was crushed into 8 to 20 meshes and a wire mesh was placed on the bottom, inner diameter 14 cm, height 13
This container was filled into a cylindrical steel container with a diameter of 1.5 cm, and this container was placed in a steel tube with an inner diameter of 15 cm and a height of 30 cm, which was equipped with a heat insulating heater around the periphery, and heated air was passed through the bottom of the cylindrical container. It was dried depending on the conditions.
For comparison, instead of passing through hot air flow, 40
Vacuum drying was carried out at 1 mmHg using a vacuum electric dryer with a volume of x40 x 40 cm. (a) Efficacy analysis Moisture 60% by weight (based on raw coal) Volatile content 49.9 〃 (based on dry coal) Fixed carbon 47.7 〃 (〃〃〃〃〃) Net calorific value 2050kcal/Kg (based on raw coal) (b ) Elemental analysis C 69.84% by weight H 4.86 〃 N 0.55 〃 S 0.31 〃 O 24.44〃

[Table] B Liquefaction of dry coal
37.5g, 0.5g of iron oxide as a catalyst, and 112.5g of coal decomposition product oil as a solvent were charged into a 500ml autoclave, hydrogen was charged at an initial pressure of 120Kg/cm ² G, and the mixture was stirred at approximately 900rpm. 3℃/
The temperature was raised to 420°C at a heating rate of min. After being held at this temperature for 60 minutes, it was rapidly cooled to room temperature. Separate the reaction product from unreacted hydrogen and produced gas, and collect the liquid product filtrate at 10 mmHg and bottom temperature.
Distilled under reduced pressure at 350°C to remove distillate oil and residue (SRC).
= Sol-vent Refined Coal).
The filtration residue was washed with a predetermined amount of benzene and acetone, and then dried under reduced pressure to obtain a reaction residue. The results are shown in Table 2. Note that the experiment number corresponds to the number of the drying test.

【table】

[Table] * Weight percentage of hydrogen consumed relative to coal
As is clear from the results in Table 2, there is a substantial difference in coal conversion rate, PRC yield, and hydrogen consumption rate between dry coal dried by vacuum drying and dry coal dried by air drying. Although no difference is observed, aerated drying with a hot air stream at 220°C is disadvantageous because the coal conversion rate and SRC yield decrease, and the hydrogen consumption rate increases. Example 2 In order to understand the changes in the composition of dried brown coal due to ventilation drying, drying was carried out using hot air flow under various drying conditions, and elemental analysis of the dried lignite was conducted, and the results are shown in Table 3. For comparison, results obtained by vacuum drying are also shown. The dried coal was from the same lot as that used in Example 1, and the drying procedure was the same as that used in Example 1.
It is similar to As is clear from the results in Table 3, there is virtually no difference in the elemental analysis values of lignite, especially in the oxygen analysis values, due to differences in drying methods.

【table】 [Brief explanation of drawings]

The drawing is a flow sheet showing one embodiment of the invention. 2... Ventilation dryer, 4... Slurry preparation tank, 5... Heater, 6... Reactor, 7... Gas-liquid separator, 10... Solid-liquid separator, 13... Residue column, 16... Heater, 18... Gas separation Equipment, 20... Hydrogen production equipment, 27... Heater, 28... Gas-liquid separator.

Claims (1)

[Claims] 1. A method characterized by drying hydrous coals by contacting them with hot air at a temperature of 200°C or less, and then heating the dried coals in a solvent under hydrogen pressure to form a coal solution. Liquefaction method for hydrous coals. 2 Hydrous coal is dried by contacting with hot air at a temperature of 200°C or less, and the dry coal that still contains some moisture is heated in a solvent to separate it into a steam phase and a coal slurry phase. A method for liquefying water-containing coal, which is characterized by removing the water content of the coal and heating the dry coal slurry thus obtained under hydrogen pressure to obtain a coal solution.