JPH0132276B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for hydropyrolyzing coal, and particularly to an effective method for hydropyrolyzing coal to suppress the production of methane due to higher-order hydrogenolysis and obtain a gasoline fraction in high yield. In recent years, coal, which is the most abundant of all fossil fuel resources and is widely distributed around the world, has been reevaluated as an energy source that can replace oil as a means of dealing with the future depletion of oil resources. I'm getting used to it. However, coal is an extremely complex polymer compound, and in addition to its main constituents carbon and hydrogen, it also contains considerable amounts of heteroatoms such as oxygen, nitrogen, and sulfur, as well as ash. In addition to emitting air pollutants, it also has a lower calorific value than petroleum, and there are problems with transportation and storage, and many other issues remain to be resolved. As a means of solving these essential problems with coal, there are many methods to liquefy coal, remove heteroatoms and ash, and obtain clean fuel oil, fuel gas, and other high value-added chemical raw materials. was proposed. Typical of these methods include, for example, a method of extracting coal with a solvent (e.g., U.S. Pat. No. 4,022,680), a method of liquefying coal in the presence of hydrogen or a hydrogen donor (e.g., U.S. Pat. Patent No. 4191629), a method for liquefying and gasifying coal in the presence of hydrogen (for example,
51-502), and a method of liquefying and gasifying coal in an inert gas (for example, US Pat. No. 3,736,233). In addition, as a method to directly obtain light oil and gas by heating coal, finely pulverized coal is jetted into a high-temperature, high-pressure hydrogen stream in a short period of time ranging from tens of milliseconds to several minutes. A method of high-speed hydrogenation and thermal decomposition of coal (for example, Japanese Patent Application Laid-Open No. 142703/1983) is also known. This method uses, for example, crushed coal under pressure
Coal is ^{10 3}
It is carried out by rapid heating at a rate of ℃/second or more and hydrogenation pyrolysis, and the reaction products are methane, ethane, carbon dioxide, carbon monoxide, hydrogen sulfide, ammonia, hydrocarbons with 3 to 5 carbon atoms, and water. , gasoline fraction, fuel oil (aromatic compounds with 10 or more carbon atoms and high-boiling point tar), and a solid product containing ash called char are obtained. In the past, many studies have been conducted to suppress the production of methane and increase the conversion rate of high-value-added gasoline fractions to light oils in such high-speed hydropyrolysis methods of coal, but the results remain unsatisfactory. There is no known way to do this. The present inventors have researched a method for processing coal with a high conversion rate into light oil with high added value. Finely pulverized coal is ejected into a heated hydrogen stream to rapidly heat it.
After instantaneous reaction at a temperature of ~1100℃, the temperature is lowered and the temperature range is 500~850℃.
It was found that holding the reaction for 60 seconds and further reacting gave improved results, and this was proposed earlier (Japanese Patent Laid-Open No. 165487/1983). Although this method considerably improves the conversion rate from coal to gasoline fraction compared to conventional methods, it is still not fully satisfactory in terms of suppressing higher-order hydrogenolysis of the gasoline fraction produced. Ta. Therefore, the present inventors discovered that the number of carbon atoms produced was 2 to 5.
We have developed an extremely effective method of hydropyrolysis of coal, which has been extensively researched to suppress the generation of methane gas due to the higher-order hydrogenolysis of hydrocarbons, especially ethane, and improve the conversion rate to gasoline fraction. This finding led to the present invention. That is, the purpose of the present invention is to produce a gasoline fraction from coal in a high yield, and at the same time, to produce hydrocarbons having 2 to 5 carbon atoms as a by-product, particularly by high-order hydrogenation of ethane, which is abundant in quantity. It is an object of the present invention to provide an industrially advantageous method for hydrogenation and pyrolysis of coal, which can effectively suppress the generation of methane gas due to pyrolysis and greatly reduce the consumption of hydrogen for hydrogenation. According to the method of the present invention, when coal is liquefied and gasified by heat treatment in a hydrogen gas atmosphere, (a) fine coal powder is heated in a hydrogen stream at a pressure of 35 to 250 kg/cm ² (1 gauge pressure); erupts to 750-1100℃
(b) A step of further reacting for 0.1 to 30 seconds at a temperature lower than the temperature of the above step and in the range of 500 to 850°C, (c) A step of causing the reaction to occur by rapidly heating to a temperature of a step of separating the char from the reaction product thus obtained; (d) a step of cooling the reaction product from which the char has been separated to separate fuel oil; and (e) a step of separating at least one of the separated fuel oils. Department
There is provided a method for hydropyrolysis of coal, which is characterized in that the step consisting of the step of circulating and supplying at the end of the reaction in step (a) is continuously performed. The coal used in the method of the present invention is preferably pulverized as much as possible, and practically the particle size is adjusted to a particle size of 100 meshes or less, preferably 200 meshes or less. In addition, the hydrogen gas flow used in step (a) is preferably formed in an atmosphere consisting essentially of hydrogen gas, but for example, up to about 30% by volume of inert gas, other water vapor, carbon dioxide gas, carbon monoxide, etc. , may be diluted with a gas such as methane. However, those containing oxidizing gas components such as oxygen, which inhibit the hydrogenolysis reaction, are disadvantageous. In the step (a), such a hydrogen stream is injected into the reaction vessel under pressure at a gauge pressure of 35 to 250 kg/cm ² in a heated state, and pulverized coal is injected into the reaction vessel to a temperature of 750 to 1100°C.
It is rapidly heated to a temperature of , and the reaction occurs instantaneously. The heating rate of the coal is preferably as fast as possible in order to increase the amount of liquid product, preferably 10 ⁴ C/sec or more, and more preferably 5 to ^{10 4} C/sec. Also,
In step (a), if the reaction temperature is higher than 1100℃, the amount of methane produced will be large and the liquid product will be small;
In addition, if the reaction temperature is less than 750°C, the rate of thermal decomposition of coal will be slow and sufficient thermal decomposition will not be obtained, so the reaction temperature must be in the range of 750°C or more and 1100°C or less.
Desirably 800℃ or higher and 1050℃ or lower. In step (a), it is necessary to instantaneously heat the differential coal to the above reaction temperature range and cause it to undergo a decomposition reaction, but if the reaction time is short, the coal will not reach the above reaction temperature, and conversely, if the reaction time is too long, the coal will not reach the above reaction temperature. Typically 20
The time period is preferably at least 800 milliseconds, more preferably at least 50 milliseconds and at most 500 milliseconds. Such a rapid heating hydrogenolysis reaction of fine coal powder needs to be carried out in the presence of a sufficient amount of hydrogen, so that the reaction in the next continuous step (b) can also be carried out effectively. A gauge pressure of 35 to 250 Kg/cm ² is advantageously employed. The material treated in step (a) is led to step (b) and is continuously processed. In step (b), the treated product in step (a) is further heated under a temperature condition of 500 to 850°C and lower than the thermal decomposition temperature in step (a)
The reaction is processed for 0.1 to 30 seconds. (b) In the process,
If the reaction temperature is higher than 850℃, the rate of decomposition of the gasoline fraction will be high and the selectivity to the gasoline fraction will be reduced, and if the reaction temperature is lower than 500℃, the rate of decomposition of the fuel oil produced in step (a) will be low. The reaction temperature is higher than 500℃ and 850℃ because it is slow and the conversion rate to gasoline fraction decreases.
The temperature must be below, preferably between 550°C and 800°C. Furthermore, if the reaction time is less than 0.1 seconds under such temperature conditions, we cannot expect much improvement in the conversion rate to gasoline fractions, and if the reaction time exceeds 30 seconds, the decomposition of gasoline fractions will progress too much, resulting in the production of methane. The reaction time in step (b), which is not preferable because it increases the amount of formation, must be 0.1 seconds or more and 30 seconds or less, preferably 0.2 seconds or more and 20 seconds or less. The reaction temperature in each reaction zone does not necessarily need to be constant and may be changed over time. Since the reaction product obtained by the reaction in step (b) contains char, which is ash, it must be separated and removed. In this (c) step,
In order to easily separate the char from the reaction product, it is desirable to maintain the temperature at which the liquid product does not condense, and usually 350°C or higher is preferred. This step (c) can also be carried out by incorporating it into the step (b). The reaction product from which the char has been separated is cooled to separate the fuel oil, but when only the fuel oil in the reaction product is separated in this (2) step, a distillation column is usually used, and the fuel oil is separated from the bottom of the column. Fuel oil and reaction products lighter than gasoline fraction are separated and taken out from the top of the column. The separation temperature can be easily determined by the pressure and the composition of the reaction product. In the present invention, at least a part of the fuel oil obtained in step (d) is transferred at the end of the reaction in step (a), that is, in
It is circulated and supplied during the transition from process to process. In this (e) process, the residence time of gasoline fraction and ethane is relatively short compared to the circulation residence time of fuel oil in step (e), so the larger the amount of fuel oil circulated, the better. However, when moving from step (a) to step (b), the amount of fuel oil circulated is naturally limited due to its heat balance, as it also functions as a cooling medium necessary to rapidly lower the reaction temperature. be done. The hydrogen gas pressure in step (a), in which the main reaction is the pyrolysis reaction of coal, is not affected much by the conversion rate from coal to liquid products; If the pressure in step (b), where the reaction is the main reaction, is increased, the conversion rate to gasoline fraction will increase. However, if the pressure is increased to a certain level or higher, the effect becomes smaller, and in the case of high-pressure operation, the equipment becomes large and becomes economically disadvantageous. Like this (b)
It is desirable to appropriately increase the reaction pressure in the process, but providing a compression process between both reactions requires cooling, which is disadvantageous both from the reaction standpoint and from the thermal energy perspective. The pressure of step (a) is determined by focusing on the desired pressure of step (a), and the pressure of step (a) is the pressure of step (b) plus the pressure loss in the reaction tube (which can usually be ignored). is desirable. The reaction pressure in both steps is preferably 35 Kg/cm ² G or more and 250 Kg/cm ² G or less, and more preferably 50 Kg/cm ² G or more and 200 Kg/cm ² G or less. Also, (c): (d) The pressure in the process is usually (b)
It is preferable to carry out the process at a pressure similar to that of the process. This is because when step (2) is carried out under high pressure, the temperature at the bottom of the distillation column can be raised, so the handling viscosity of the fuel oil becomes low and the operability becomes very easy. The weight ratio of hydrogen for reaction to the supplied pulverized coal (dry and ash-free basis) varies depending on the type of coal and the composition of the required reaction product, and is generally the weight ratio of hydrogen to the supplied coal (dry and ash-free basis). The ratio is 0.03 ~
0.08 is fine, but excess hydrogen is necessary to improve the diffusion of liquid products from coal and the diffusion of hydrogen into coal pores, increase the conversion rate from coal to gasoline fraction, and prevent coking. It is desirable to supply However, excess hydrogen is separated from the products from the coal, returned to the reactor, and recycled, so when the amount of excess hydrogen increases, the energy and equipment required for separation, circulation, and heating become large, making it uneconomical. be at a disadvantage. Therefore, the weight ratio of supplied hydrogen to supplied coal is 0.1 or more and 1.5 or less (1:10 to 3:2).
is preferable, and more preferably 0.12 or more and 1.0 or less. The present invention can achieve the object extremely effectively and obtain improved effects by continuously operating the steps (a) to (e) in combination. As mentioned above, the coal treated by the method of the present invention is composed of a variety of extremely complex polymeric substances and organic compounds, and therefore an extremely wide variety of phenomena and behaviors are observed during the treatment process. Although it is difficult to clearly understand the process, many research experiments conducted by the present inventors have revealed that gasoline fractions are produced not only directly from coal but also by further hydrogenolysis of fuel oil, an intermediate product. However, the latter is more dominant overall, and the resulting gasoline fraction is further subjected to higher hydrogen cracking to ultimately produce methane. It was discovered that suppressing the production of methane is an important issue. By the way, the reaction of converting coal to gasoline fraction in the present invention can be thought of mainly through two processes. One is that covalent bonds with low bond dissociation energy are cleaved by simple thermal decomposition of coal, and free radicals are generated. Therefore, this is the first stage reaction process in which reactions such as hydrogen abstraction, dehydrogenation, recombination, and cyclization proceed and are stabilized as liquid decomposition products. It is presumed that the resulting thermal decomposition liquid product is hydrogenolyzed in the second stage reaction process to further reduce the molecular weight. It is thought that the first stage reaction process is completed in a relatively short time, and the higher the reaction temperature, the more intense the cleavage of covalent bonds with lower bond dissociation energy appears to occur. On the other hand, the second stage reaction process produces more gasoline fraction than the hydrogen cracking reaction of the fuel oil produced in the first stage reaction process, but the target product is the gasoline fraction or the ethane produced as a by-product. In order to suppress the higher-order hydrogenolysis reaction of methane into methane, it is necessary to carry out the reaction at a relatively low temperature, and to quickly remove the generated gasoline fraction and ethane from the reaction system. According to the method of the present invention, a large amount of liquid product is produced in step (a), and the fuel oil separated in step (d) is introduced into this product (step (e)). By using the latent heat of vaporization and sensible heat, the temperature conditions in the (b) process can be obtained without substantially requiring external cooling (for example, cooling by direct supply of hydrogen or water, or cooling by indirect heat exchange). This is extremely convenient, and furthermore, by circulating the fuel oil in this manner, the hydrogenolysis rate of the fuel oil is made faster than the hydrogenolysis rate of gasoline, and the actual decomposition reaction time of the gasoline fraction produced by cracking is shortened. As a result, significantly improved results can be obtained, and the present invention can be said to be an industrially superior method. In addition,
In the present invention, coal refers to anthracite coal, bituminous coal, subbituminous coal, charcoal, lignite, dirty coal, grass coal, and the like. In addition, the conversion rate from coal to each reaction product is
It is defined by the following equation. Conversion rate of each reaction product =
Amount of carbon in each reaction product/amount of carbon in supplied coal x 100% The present invention will be described in more detail with reference to Examples below, but the present invention is not limited to these Examples. Example 1 Illinois No. 6 coal was sequentially crushed using a geocrusher, a brown coal mill, and a ball mill.
After removing coarse particles using a 200-mesh sieve, it was dried in a vacuum dryer at -720 mmHg and 100°C for 10 hours to adjust the moisture content to 3 parts by weight or less based on 100 parts by weight of coal. The elemental analysis values of the coal were as shown in Table 1 based on anhydrous coal.

【table】

[Table] 1.0Kg/H of hydrogen at room temperature under a pressure of 100Kg/cm ² G is preheated to 900℃ using an externally heated Hastelloy It was heated to 1150℃ using an externally heated ceramic hydrogen heating tube. On the other hand, the finely pulverized dry coal at room temperature of 2.5Kg/H is continuously fed using a table-type coal feeder under a pressure of 100Kg/cm ² G, and hydrogen at room temperature of 0.1Kg/H and a pressure of 100Kg/cm ² G is used. The coal was conveyed using a hydrogen gas stream, and the coal was jet-mixed into the superheated hydrogen stream to rapidly raise the temperature of the coal from room temperature to 930°C. The heating rate of coal at this time is approximately 2
×10 ⁵ °C/sec. Further, the mixture of coal and hydrogen was passed through an externally heated ceramic reaction tube having an inner diameter of 6 mmφ, and the reaction in step (a) was carried out at a reaction temperature of 930° C. and a reaction time of 120 milliseconds. After that, 3.4 kg/H of fuel oil, which will be described later, is sprayed with hydrogen and mixed with the reaction product of step (a), and the temperature of the reaction product is adjusted.
The mixture was rapidly cooled to 700°C and passed through an externally heated stainless steel reaction tube with an inner diameter of 2 mmφ connected to a ceramic reaction tube to carry out the reaction in step (b) at a reaction temperature of 700°C and a reaction time of 2 seconds. The reaction product from the reaction tube in step (b) was mixed with hydrogen at room temperature, the reaction product was rapidly cooled to 450°C, and the charge was separated using a cyclone-type charge trap. Furthermore, the reaction product was introduced into a distillation column with an inner diameter of 50 mmφ and a height of 3000 mm packed with a Raschig ring, and fuel oil was separated from the bottom of the column, and light products higher than gasoline fraction were separated from the top of the column. The top temperature is 95℃, and the bottom temperature is 150℃.
I kept each one and drove it. The fuel oil at the bottom of the column (a) was circulated to rapidly cool the reaction product at the end of the process, and a surplus of approximately 0.1 kg/h was extracted from the circulation system. On the other hand, the light products discharged from the top of the tower are cooled to room temperature by indirect water cooling to condense the water and gasoline fraction, and after separating the water and gasoline fraction in a decanter, the gasoline fraction is A part of it was used as reflux in the distillation column, and the rest was extracted from the system. For uncondensed gases, methane, ethane, ethylene,
CO+CO ₂ and a hydrocarbon gasoline fraction having 3 to 5 carbon atoms were analyzed, and the fuel oil, gasoline fraction, and water extracted from the system were also analyzed in the same manner. In addition, in order to keep the reaction temperature constant in steps (a) and (b), an electric heater was installed around the reaction tube, and a hydrogen heating tube, the reaction tube and the electric heater in steps (a) and (b) were By storing the reaction tube in a stainless steel pressure-resistant container with an inner diameter of 500 mm, there was no need for a pressure-resistant reaction tube. Also, the pressure from step (a) to step (d) is 100Kg/cm ²
(a) The amount of hydrogen supplied to the coal supplied in the process reaction is 0.5 (weight ratio) on an anhydrous and ash-free basis,
(b) The amount of hydrogen supplied to the coal supplied for the process reaction is 0.54
(weight ratio). The amount of fuel oil circulated relative to the supplied coal was 1.5 (weight ratio) on an anhydrous and ash-free basis. As a result of analysis of the reactant, the conversion rate of the reaction product from coal based on carbon standards was as shown in Table 2.

[Table] The amount was 102% by weight, but the amount for which the material balance did not match was taken as fuel oil. Examples 2 to 5 Dry pulverized coal (Illinois No. 6) used in Example 1
A reaction experiment was conducted on the same sample using the apparatus described in Example 1. As reaction conditions for each example,
Table 3 shows the results obtained by varying the reaction zone temperature, time, reaction hydrogen supply amount relative to the supplied coal, and fuel oil circulation amount relative to the supplied coal in steps (a) and (b). In addition, in order to change the reaction time in steps (a) and (b), the length and diameter of the reaction tubes were appropriately changed.

[Table] Comparative Examples 1 to 3 Using the apparatus described in Example 1, the fuel oil supply to the reaction end section of step (a) was stopped, only room temperature hydrogen was supplied, and the reaction products were mixed, and (b) The step reaction was carried out. Using the same sample of pulverized coal as in Example 1, a reaction experiment similar to that in Example 1 was carried out at a coal supply rate of 2.5 kg/h. The experimental results are shown in Table 4.

【table】

[Table] Typical improvement effects of the present invention compared to the prior art are listed below. (1) The conversion rate from coal to gasoline fraction increases by approximately 7%. (2) The conversion rate from coal to ethane increases by approximately 13%. (3) The total conversion rate from coal is approximately 60%, which is equivalent to conventional technology.
%, but the conversion rate to methane is 5% lower, so the amount of hydrogen consumed for reaction is small, and the hydrogen production cost can be reduced. (4) When lowering the temperature of the reaction product from step (a) to step (b), there is no need to directly supply a cooling medium from the outside, so there is no cost for recovering it.

Claims (1)

[Claims] 1. When coal is heat-treated in a hydrogen gas atmosphere to liquefy and gasify it, (a) fine coal powder is heated to a pressure of 35 to 250 Kg/cm ² (gauge pressure);
(b) At a temperature lower than the temperature of the previous step and in the range of 500 to 850°C, further 0.1 a step of reacting for ~30 seconds; (c) a step of separating the char from the reaction product obtained by the reaction; (d) a step of cooling the reaction product from which the char has been separated to separate fuel oil; (e) At least a portion of the separated fuel oil
(a) A method for hydropyrolysis of coal, characterized in that a step consisting of a step of circulating and supplying at the end of the reaction of the step is carried out continuously. 2. The heating rate of fine coal powder in step (a) is
The method according to claim 1, wherein the temperature is 10,000° C./second or more. 3 (a) Supply amount of fine coal powder in process (anhydrous,
The weight ratio of the ash-free standard) and the amount of hydrogen supplied for reaction is
10. A method according to claim 1, wherein the ratio is between 10:1 and 2:3. 4 (e) Claim 1 in which the fuel oil supply in the step is carried out by spraying using steam or hydrogen
The method described in section.