CN103074093A - Direct drying and pyrolysis integrated process and system for lignite - Google Patents

Abstract

The invention relates to a process and system for integrating direct drying and pyrolysis of lignite. The process includes sending fuel into a high-temperature catalytic cracking furnace for combustion, and the heat generated is used as a heat source for the cracking reaction of crude gas in the high-temperature catalytic cracking furnace; The medium-temperature flue gas discharged from the upper flue gas outlet of the cracking furnace enters the external heating jacket of the pyrolysis furnace, and indirectly heats, dries and pyrolyzes the lignite raw material to produce semi-coke, crude gas and water vapor, and the tail gas of the flue gas is emptied; the crude gas and The unreacted water vapor is discharged from the pyrolysis furnace, enters the high-temperature catalytic cracking furnace through the gas inlet, and catalytic cracking and steam reforming reactions occur inside it to generate high-temperature cracking gas; part of the high-temperature cracking gas flows back into the pyrolysis furnace Furnace, the remaining part is used as external fuel gas or synthetic raw material after dust removal, water washing and filtration purification. The invention omits the drying and steam preparation links in the traditional lignite steam gasification application, and improves the utilization efficiency of spontaneous steam.

Description

A lignite direct drying and pyrolysis integrated process and system

technical field

The patent of the present invention relates to the integrated process and system of lignite direct drying and pyrolysis, in particular to the process and system of applying the low-pressure water vapor generated in the lignite drying process to the subsequent catalytic reforming reaction, which belongs to the technical field of clean and efficient utilization of low-quality coal .

technical background

my country's total coal reserves reach 600 billion tons, ranking third in the world, of which lignite accounts for about 12.7%. Lignite is a coal with a state between anthracite and peat. Due to its short coal-forming time, high moisture content (generally up to 30%−60%), high volatile content, and low ignition point, it has poor thermal stability and chemical High activity, calorific value is generally below 4000kcal/kg. High water content reduces the energy density of lignite, which brings great difficulties to the transportation and efficient utilization of lignite, which greatly limits the scale of lignite mining.

Taking advantage of the high chemical activity of lignite, producing syngas through steam gasification, and then using it to synthesize a series of chemicals is an important way for the clean utilization of lignite. In the traditional lignite utilization scheme, the lignite with high moisture content must be pre-dried before entering the gasifier, such as hot air drying, to reduce its humidity to a certain range. This method of drying first and then using it not only increases equipment investment, but also consumes more energy in the drying process. In addition, most of the steam required for steam gasification is produced by auxiliary steam generators, and a large amount of low-pressure water vapor generated by drying and evaporation cannot be utilized. The phenomenon of repeated energy consumption in the process of lignite drying and gasification is serious, and the energy utilization rate is low. , high processing cost.

Hu Guoxin et al. proposed a process for producing high-concentration hydrogen by directional gasification of wet biomass in Hydrogen-Rich Gas Production from Pyrolysis of Biomass in an Auto-generated Steam Atmosphere (ENERGY & FUELS, 2009, 23: 1748-1753). The process integrates wet biomass drying and pyrolysis, steam gasification, and high-temperature in-situ _CO2 separation in one reactor, so that the spontaneous steam generated by moisture drying can be steam-gasified, and the gas with high hydrogen production concentration can be obtained. While degassing, the operation is simplified and the energy consumption is reduced. Guo Liejin et al. (patent CN 102126704A) carried out catalytic gasification of biomass in supercritical water, the gasification rate of biomass can reach 100%, the volume percentage of _H2 in the gas product can even exceed 50%, and there is no tar in the reaction , charcoal and other by-products will not cause secondary pollution. Wet biomass with high water content can be directly gasified without the need for high energy consumption drying process. However, these conversion methods are mainly aimed at the hydrogen production process from biomass, and cannot produce fuel gas, or produce synthesis gas for the synthesis of chemical raw materials. Therefore, starting from the improvement of the steam supply mode, the efficient and clean utilization of lignite is used to produce gas or syngas, and the low-pressure steam generated during the lignite drying process is applied to the subsequent gasification and reforming reaction process to save energy and reduce equipment consumption. And investment, has very important practical significance and better economy. Previously, there was no report on the integrated utilization of lignite by direct drying-pyrolysis.

Contents of the invention

In order to overcome the deficiencies of the prior art, the object of the present invention is to provide a lignite direct drying and pyrolysis integrated process and system, so that lignite can be pyrolyzed and gasified in a spontaneous steam atmosphere, eliminating the need for traditional lignite steam gasification applications The drying and steam preparation links in the process improve the utilization efficiency of spontaneous steam.

In order to achieve the above object, a technical solution of the present invention is:

A lignite direct drying and pyrolysis integrated system, the system is composed of a pyrolysis furnace, a high temperature catalytic cracking furnace, a buffer tank, a fuel hopper, a blower, a cyclone dust collector, a water washing tank and an activated carbon filter tank, the pyrolysis furnace It is composed of an inner furnace and an outer heating jacket. The inner furnace of the pyrolysis furnace is equipped with an upper top inlet, an upper gas outlet, a bottom carbon outlet and a lower air inlet. The heating jacket of the pyrolysis furnace is equipped with The lower flue gas inlet and the upper flue gas outlet; the high temperature catalytic cracking furnace is equipped with a top air inlet, an upper flue gas outlet, a bottom gas outlet and a lower fuel inlet, and a catalyst is installed in the high temperature catalytic cracking furnace; the buffer tank is equipped with an upper gas inlet, The gas outlet on the left side and the gas outlet on the right side; the upper gas outlet of the inner furnace of the pyrolysis furnace is connected to the upper air inlet of the high temperature catalytic cracking furnace, the lower air inlet of the inner furnace of the pyrolysis furnace is connected to the left gas outlet of the buffer tank, and the heat The lower flue gas inlet of the heating jacket outside the cracking furnace is connected to the upper flue gas outlet of the high temperature catalytic cracking furnace, the bottom gas outlet of the high temperature catalytic cracking furnace is connected to the top gas inlet of the buffer tank, the lower fuel inlet of the high temperature catalytic cracking furnace and the fuel hopper The discharge port is connected, the gas outlet on the right side of the buffer tank is connected to the upper air inlet of the gas cyclone dust collector, the outlet of the cyclone dust collector is connected to the inlet of the water washing tank, and the outlet of the water washing tank is connected to the inlet of the activated carbon filter tank.

As a further improvement of the present invention, the pyrolysis furnace and the high-temperature catalytic cracking furnace are both made of high-temperature resistant stainless steel, and the surface is heat-resistant treated or lined with a refractory layer.

As a further improvement of the present invention, the high-temperature catalytic cracking furnace is a shell and tube structure, the crude gas enters from the top, and is heated in the tube side to produce catalytic cracking and steam re-reaction; The gas flows countercurrently to provide heat for the cracking reaction.

In order to achieve the above object, another technical solution of the present invention is:

A lignite direct drying and pyrolysis integrated process, comprising the following steps:

S1. The fuel is fed into the high-temperature catalytic cracking furnace for combustion, and the heat generated is used as the heat source of the high-temperature catalytic cracking furnace;

S2. The medium-temperature flue gas discharged from the upper flue gas outlet of the high-temperature catalytic cracking furnace with a temperature of 500 − 900 °C enters the outer heating jacket of the pyrolysis furnace through the flue gas inlet, and heats, dries and pyrolyzes the lignite raw material to produce semi-coke, Contains crude gas and water vapor, and the flue gas tail gas is emptied after purification;

S3. Crude gas and unreacted water vapor are discharged from the gas outlet on the top of the pyrolysis furnace, and enter the high-temperature catalytic cracking furnace through the gas inlet. Catalytic cracking and steam reforming reactions occur inside the high-temperature catalytic cracking furnace, and the high-temperature cracking gas produced by the reaction ;

S4. Part of the high-temperature cracking gas flows back into the inner furnace of the pyrolysis furnace as a heat source to directly heat the lignite, and the remaining part is used as external gas supply or synthetic raw material after dust removal, water washing, filtration and purification.

As a further improvement of the present invention, the fuel is biomass with a particle size of 0.025mm − 0.25mm. The fuel is mixed with air and burned in a high-temperature catalytic cracking furnace, which can generate a high temperature of 1000-1200°C, which is catalytic heat The furnace provides heat.

As a further improvement of the present invention, the drying and pyrolysis in step 2 include heating and dehydrating the lignite first to generate low-pressure steam, and then continuing to raise the temperature for pyrolysis to generate coal semi-coke and crude gas.

As a further improvement of the present invention, the temperature of the crude gas in step 2 when it exits the pyrolysis furnace is 300-600 °C.

As a further improvement of the present invention, the temperature of the high-temperature cracked gas in the step 4 when entering the pyrolysis furnace is 700-1000 °C;

As a further improvement of the present invention, after the crude gas in step 4 undergoes catalytic cracking and steam reforming reactions, the temperature of the high-temperature cracked gas E generated is 800-1000°C.

This process is applicable to a variety of furnace types, including three-stage furnaces, vertical furnaces, etc., and does not have high requirements on the particle size of lignite fed into the furnace.

This process is suitable for lignite or other coals with a moisture content of 20% − 60%, and also for raw materials with high moisture content such as domestic garbage and sludge.

Beneficial effect:

(1) In this process, the pyrolysis gas is not diluted by external gas, and all the generated gas is finally used for external supply; the low-pressure water vapor (50 − 500 Pa) generated by pyrolysis is used for steam catalysis of lignite and pyrolysis gas The reforming reaction has a high utilization rate of steam; the system does not have additional water vapor to enter, and the energy consumption is reduced.

(2) This process integrates lignite drying and pyrolysis gasification into a process system, which saves a separate drying process and equipment. The process is simple and easy to operate, which reduces equipment investment and operating costs.

(3) The energy required in the pyrolysis and gasification process of lignite in this process is supplied by biomass. Since biomass is a renewable energy source, the present invention has great environmental benefits.

Description of drawings

Fig. 1 is a schematic flow diagram of the integrated process and system of lignite direct drying and pyrolysis in Example 1 of the present invention.

In the figure 1−pyrolysis furnace, 2−high temperature catalytic cracking furnace, 3−buffer tank, 4−micron fuel hopper, 5−blower, 6−cyclone dust collector, 7−water washing tank, 8−activated carbon filter tank, 11−heat Flue gas inlet at the lower part of the cracking furnace, 12-gas outlet at the upper part of the pyrolysis furnace, 13-gas inlet at the top of the high-temperature catalytic cracking furnace, 14-gas outlet at the bottom of the high-temperature catalytic cracking furnace, 15-gas inlet at the top of the buffer tank, 16-lower part of the pyrolysis furnace Gas inlet, 17-cyclone separator inlet, 18-cyclone separator outlet, 19-water washing tank inlet, 20-water washing tank outlet, 21-activated carbon filter tank inlet; A-lignite raw material, B-brignite semi-coke, C-coarse Coal gas, D−water vapor, E−high temperature pyrolysis gas, F−purified gas, G−biomass micron fuel, H−medium temperature flue gas, J−tail gas.

Detailed ways

Example 1

As shown in Figure 1, the lignite direct drying and pyrolysis integrated system consists of a pyrolysis furnace 1, a high-temperature catalytic cracking furnace 2, a buffer tank 3, a micron fuel hopper 4, a blower 5, a cyclone dust collector 6, a water washing tank 7, and activated carbon Filter tank 8 etc. are formed. The pyrolysis furnace 1 is composed of an inner furnace and an outer heating jacket. The inner furnace of the pyrolysis furnace 1 is provided with an upper top feed inlet 13, an upper gas outlet 12, a bottom charcoal outlet and a lower air inlet 16. , the heating jacket of the pyrolysis furnace 1 is provided with a lower flue gas inlet 11 and an upper flue gas outlet; the high temperature catalytic cracking furnace 2 is provided with a top air inlet 13, an upper flue gas outlet 10, a bottom gas outlet 14 and a lower fuel inlet 9. The high-temperature catalytic cracking furnace 2 is equipped with a catalyst; the buffer tank 3 is provided with an upper gas inlet 15, a left gas outlet, and a right gas outlet; the micron fuel hopper 4 is provided with a top feed port and a bottom discharge port; the pyrolysis furnace 1 The upper gas outlet 12 of the inner furnace is connected to the upper air inlet 13 of the high-temperature catalytic cracking furnace 1, the bottom air inlet 16 of the inner furnace of the pyrolysis furnace 11 is connected to the left gas outlet 15 of the buffer tank 13, and the pyrolysis furnace 1 is heated externally The lower flue gas inlet 11 of the jacket is connected to the upper flue gas outlet 10 of the high temperature catalytic cracking furnace 2, the bottom gas outlet of the high temperature catalytic cracking furnace 12 is connected to the top gas inlet 15 of the buffer tank 3, and the gas outlet on the right side of the buffer tank 13 is connected to the gas The upper air inlet 17 of the cyclone dust collector 16, the lower part inlet 19 of the cyclone dust collector outlet 18 and the water washing tank 7 are connected, and the water washing tank outlet 20 is connected with the activated carbon filter tank inlet 21.

As shown in Figure 1, the lignite direct drying and pyrolysis integration process includes the following steps:

S1. Start the blower 4, spray the biomass micron fuel G into the high-temperature catalytic cracking furnace 2 for combustion, and heat the high-temperature catalytic cracking furnace 2 to 1100°C.

S2. Start the feeding mechanism, continuously feed the lignite A into the lignite pyrolysis furnace 1 from the top feed port, and at the same time introduce the medium-temperature flue gas H from the high-temperature catalytic cracking furnace 2 into the outer heating jacket of the pyrolysis furnace 1, and process the lignite raw material A Heating pyrolysis. The lignite is heated to 150 - 300°C, the water in the lignite is gradually evaporated into water vapor D, and then the temperature continues to rise to 500 - 600°C, and pyrolysis produces semi-coke B and crude gas C.

S3. Crude gas C and unreacted water vapor enter the high-temperature catalytic cracking furnace 2 , where catalytic cracking and steam reforming reactions occur inside, and high-temperature cracking gas E at 900°C is generated.

S4. The high-temperature cracked gas E is discharged from the outlet of the high-temperature catalytic cracking furnace 2, and the high-temperature cracked gas E is introduced into the pyrolysis furnace 1, and the high-temperature cracked gas E equivalent to the amount of raw gas flows back to the pyrolysis furnace, and contacts and exchanges heat with lignite A countercurrently. The lignite is heated to 800°C, and the coal semi-coke B is discharged from the bottom of the pyrolysis furnace 1, and is output as fuel after being cooled. The remaining pyrolysis gas is purified and treated by the cyclone dust collector 6, the water washing tank 7, and the activated carbon filter tank 8 as the gas for external supply.

Example 2

Taking a lignite coal in Inner Mongolia as an example, its calorific value is 3500kcal/kg, its total moisture content is 34.5%, its volatile matter content is 35%, and its ash content is 11%. After the lignite is sieved, the particle size ranges from 3 mm to 20 mm, and it enters the pyrolysis furnace continuously at a rate of 50 kg/h. It is heated in the pyrolysis furnace 1 to remove moisture and generate low-pressure steam D; after dehydration, the lignite A is gradually heated To 800 ℃, pyrolysis produces coal semi-coke B, crude gas C (including tar) and water vapor D. The medium-temperature flue gas H (800°C) discharged after the combustion of the micron fuel G is passed into the pyrolysis furnace 1 to heat the lignite A;

Crude gas C and steam D enter the high-temperature catalytic cracking furnace 2, where catalytic cracking and steam reforming reactions occur at 1100°C. Part of the generated high-temperature cracked gas E (temperature 900°C) flows back into the pyrolysis furnace 1 to heat and pyrolyze the lignite A, and the remaining gas is treated by cyclone dust removal 6, water washing 7, and activated carbon filtration 8 before being delivered to users .

After sampling and analysis, the composition of the condensed gas E is: 45.6% hydrogen, 9.2% methane, 25.6% carbon monoxide, and 19.6% carbon dioxide.

All the other technological procedures of this example are the same.

Claims (9)

1. A lignite direct drying and pyrolysis integrated system is characterized in that the system consists of pyrolysis furnace (1), high temperature catalytic cracking furnace (2), buffer tank (3), fuel hopper (4), blower ( 5), a cyclone dust collector (6), a water washing tank (7) and an activated carbon filter tank (8); the pyrolysis furnace (1) is composed of an inner furnace and an outer heating jacket, and the pyrolysis furnace (1) The inner furnace of the furnace is provided with an upper top feed inlet, an upper gas outlet (12), a bottom charcoal outlet and a lower air inlet (16), and the heating jacket of the pyrolysis furnace (1) is provided with a lower flue gas inlet ( 11) and the upper flue gas outlet; the high temperature catalytic cracking furnace (2) is equipped with a top air inlet (13), an upper flue gas outlet (10), a bottom gas outlet (14) and a lower fuel inlet (9). The furnace (2) is equipped with a catalyst; the buffer tank (3) is provided with an upper gas inlet (15), a left gas outlet and a right gas outlet; the upper gas outlet (12) of the inner furnace of the pyrolysis furnace (1) is connected to the high temperature The upper air inlet (13) of the catalytic cracking furnace (1), the bottom air inlet (16) of the inner furnace of the pyrolysis furnace (11) is connected to the buffer tank (13) and the left gas outlet (15), and the pyrolysis furnace (1 ) The lower flue gas inlet (11) of the external heating jacket is connected to the upper flue gas outlet (10) of the high temperature catalytic cracking furnace (2), and the bottom gas outlet of the high temperature catalytic cracking furnace (12) is connected to the top gas of the buffer tank (3) The inlet (15), the gas outlet on the right side of the buffer tank (13) are connected to the upper air inlet (17) of the gas cyclone dust collector (16), the lower inlet (19) of the cyclone dust collector outlet (18) and the water washing tank (7) ) connection, water washing tank outlet (20) and activated carbon filter tank inlet (21) connection. 2. The lignite direct drying and pyrolysis integrated system according to claim 1, characterized in that, the pyrolysis furnace (1) and the high-temperature catalytic cracking furnace (2) are both made of high-temperature resistant stainless steel, and the surface is Heat-resistant treatment or lined with refractory layer. 3. The lignite direct drying and pyrolysis integrated system according to claim 1, characterized in that, the high-temperature catalytic cracking furnace (2) is a tube-and-tube structure, and the crude gas (C) and water vapor (D) It enters from the top and is heated in the tube side to undergo catalytic cracking and steam re-reaction; the high-temperature flue gas flows countercurrently with the crude gas outside the tube to provide heat for the entire reaction. 4. A lignite direct drying and pyrolysis integration process is characterized in that the process comprises the following steps: S1. Send the fuel into the high-temperature catalytic cracking furnace (2) for combustion, and the heat generated is used as the heat source for catalytic cracking in the high-temperature catalytic cracking furnace (2); S2. The medium-temperature flue gas (H) discharged from the upper flue gas outlet (10) of the high-temperature catalytic cracking furnace (2) with a temperature of 500-900 °C enters the external heating clamp of the pyrolysis furnace (1) through the flue gas inlet (11) Set, heating, drying and pyrolyzing the lignite raw material (A) to produce semi-coke (B), crude gas (C) and water vapor (D), and the tail gas J is purified and then emptied; S3. Crude gas (C) and unreacted water vapor (D) are discharged from the gas outlet (12) on the top of the pyrolysis furnace, and enter the high-temperature catalytic cracking furnace (2) through the gas inlet (13). ) Catalytic cracking and steam reforming reactions occur inside to produce high-temperature cracked gas (E); S4. Part of the high-temperature cracking gas (E) flows back into the inner furnace of the pyrolysis furnace (2) as a heat source to directly heat the lignite, and the remaining part is purified by cyclone dust removal, water washing and filtration, and then used as external gas or synthetic gas. raw material. 5. The lignite direct drying ̶ ̶ and pyrolysis integrated process according to claim 4, characterized in that, the fuel is biomass with a particle size of 0.025mm − 0.25mm. 6. The lignite direct drying and pyrolysis integration process according to claim 4 is characterized in that the drying and pyrolysis in the step 2 include heating and dehydrating the lignite to generate low-pressure water vapor, and then continue to heat up, heat Decomposition produces coal semi-coke (B), crude gas (C) and water vapor (D). 7. The lignite direct drying and pyrolysis integrated process according to claim 4, characterized in that the temperature of the raw gas (C) and steam (D) in the step 2 when they leave the pyrolysis furnace is 300 − 600°C. 8. The lignite direct drying and pyrolysis integrated process according to claim 4, characterized in that the temperature of the high-temperature cracked gas E in step 4 when entering the pyrolysis furnace is 700-1000 °C. 9. The lignite direct drying and pyrolysis integrated process according to claim 4, characterized in that, after the crude gas (C) in step 4 undergoes catalytic cracking and steam reforming reactions, the resulting high-temperature cracking Gas (E) temperature is 800-1000°C.

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