A system and method for recovering organic matter from coal gas-water concentrate in a fixed-bed gasifier.

Abstract

This invention discloses a system and method for recovering organic matter from the concentrated coal gas water of a fixed-bed gasifier. The recovery system is structured as follows: a fixed-bed gasifier, a coal gas water heat exchanger, a scrubbing tower, and a heater are connected in sequence. The coal gas water outlet at the top of the heater is connected to the top of a humidification tower. The circulating water outlet at the bottom of the humidification tower is connected to the coal gas water inlet via a coal gas water circulation pipeline. The top of the humidification tower is connected to the bottom of the fixed-bed gasifier. The concentrated water inlet of a centrifugal extractor is connected to the coal gas water circulation pipeline, the solvent inlet is connected to a solvent tank, and the solvent phase outlet is connected to a fractionation tower. The top of the fractionation tower is connected to the solvent tank, and the bottom is connected to a crude phase intermediate product tank. Through this recovery system, the coal gas water produced during the coal gasification process is completely evaporated into water vapor to supply the gasifying agent in the gasifier. Most of the organic matter in the coal gas water is absorbed and separated by the solvent to obtain crude phenol products. The gasification workshop does not discharge coal gas water externally, and it is recovered and utilized as a resource.

Description

Technical Field

[0001] This invention relates to a system and method for recovering organic matter from coal gas-water concentrate in a fixed-bed gasifier, belonging to the field of coal conversion and utilization technology. Background Technology

[0002] For the foreseeable future of the next 10 to 20 years, coal will remain my country's most important energy base. Many energy-intensive production processes, such as glass and ceramics manufacturing, require clean fuels. Although natural gas is the first choice, its limited supply and high price mean that many industries cannot abandon it. Converting coal into clean coal gas is a good alternative to natural gas. Currently, the industrial gasification furnaces widely used in my country still suffer from coal gas water pollution emissions and high treatment costs for coal gas containing organic matter. Summary of the Invention

[0003] This invention provides a system and method for recovering organic matter from coal gas water concentrate in a fixed-bed gasifier. It mainly targets the internal circulation of water generated during the production process of a low-pressure gasifier using air as the gasifying agent. Most of the water in the coal gas water is evaporated into reactants required for the gasification reaction, and the organic matter in the concentrate is recovered to obtain high-value by-products.

[0004] The organic matter recovery system in the gas-water concentrate of a fixed-bed gasifier provided by the present invention includes a gas-water heat exchanger, a scrubbing tower, a heater, a humidification tower, a centrifugal extractor, and a fractionation tower.

[0005] The gas outlet of the fixed-bed gasifier is connected to the gas inlet of the gas-water heat exchanger, the gas outlet of the gas-water heat exchanger is connected to the gas inlet of the scrubbing tower, and the gas outlet of the scrubbing tower is connected to the downstream user.

[0006] The washing water circulation pipeline of the washing tower is connected to the gas and water inlet at the bottom of the heater, the gas and water outlet at the top of the heater is connected to the top of the humidification tower, the circulation water outlet at the bottom of the humidification tower is connected to the gas and water inlet through the gas and water circulation pipeline, and the top of the humidification tower is connected to the bottom of the fixed bed gasifier.

[0007] The centrifugal extractor is equipped with a concentrated water inlet, a solvent inlet, an aqueous phase outlet, and a solvent phase outlet. The concentrated water inlet is connected to the gas-water circulation pipeline (to discharge part of the concentrated gas-water from the circulation loop and recover the organic matter therein), the solvent inlet is connected to the solvent tank, and the solvent phase outlet is connected to the fractionation tower.

[0008] The top of the fractionation column is connected to the solvent tank, and the bottom is connected to the coarse phase intermediate product tank.

[0009] In the above-mentioned recovery system, the tube side of the gas-water heat exchanger is connected to the gas transmission pipeline, and the shell side is connected to the water transmission pipeline.

[0010] In the above-mentioned recovery system, the gas-water inlet is connected to the tube side of the heater, and the shell side is connected to the steam circulation pipeline.

[0011] In the aforementioned recycling system, a steam heater is provided at the bottom of the humidification tower.

[0012] In the above-mentioned recycling system, a solid-liquid separator is installed on the pipeline connecting the concentrated water inlet and the gas-water circulation pipeline to filter out solid substances.

[0013] In the above-mentioned recovery system, the aqueous phase outlet is connected to the gas-water circulation pipeline.

[0014] In the above-described recovery system, a reboiler is connected to the bottom of the fractionation column.

[0015] In the above-mentioned recovery system, a condenser is provided between the distillation tower and the solvent tank.

[0016] In the above-described recovery system, the solvent tank is equipped with a solvent inlet.

[0017] Based on the recovery system of this invention, this invention further provides a method for recovering organic matter from the gas-water concentrate of a fixed-bed gasifier, comprising the following steps:

[0018] The gas produced by the fixed-bed gasifier is fed into the gas-water heat exchanger of the recovery system. After being cooled, it enters the scrubbing tower and is then washed before entering the downstream unit. The gas is cooled and washed to produce gas-water containing organic matter.

[0019] The gas-water produced by the scrubbing tower is fed into the heater for heating; the heated gas-water enters the humidification tower from the top and comes into countercurrent contact with the air / oxygen entering from the bottom. Part of the gas-water changes from liquid to steam and mixes with the air / oxygen. The resulting humid air containing water vapor enters the fixed-bed gasifier from the bottom as a gasifying agent.

[0020] The remaining gas-water in the humidification tower is circulated to the heater for further heating (i.e., the remaining water in the humidification tower cools down due to heat absorption from partial water evaporation, and the lower-temperature gas-water is circulated to the heater by the circulating water pump to continue being heated by water vapor).

[0021] The concentrated liquid produced during the circulation-evaporation process of the coal gas-water enters the centrifugal extractor and is extracted and centrifuged with the organic solvent therein. The resulting solvent phase enters the fractionation tower for fractionation, and the resulting aqueous phase is connected to the coal gas-water circulation pipeline. Crude phenol intermediate is obtained at the bottom of the fractionation tower, and the solvent obtained at the top of the tower is recycled back to the centrifugal extractor.

[0022] In the above recovery method, the concentrated water after filtration to remove solids is simultaneously mixed with the organic solvent in the centrifugal extractor. The organic components are more soluble in the organic solvent than in water, and most of the phenol and other organic compounds in the concentrated water are absorbed by the organic solvent. Due to the density difference between the organic solvent and water, the organic solvent is lighter. The rotation of the centrifugal extractor promotes the separation of the organic solvent phase and the aqueous phase; the solvent phase and the aqueous phase flow continuously from the two outlets of the centrifugal extractor, respectively.

[0023] In the above recovery method, the concentration of organic matter in the lower aqueous phase (raffinate) is reduced, and it is sent back to the gas-water circulation loop to allow the water in it to continue to evaporate.

[0024] In the above recovery method, the upper solvent phase is sent to a fractionation tower. After the mixture is heated by steam in the reboiler, due to the difference in boiling points between the organic solvent and the organic components, the low-boiling-point organic solvent gas rises to the top of the fractionation tower. After cooling, liquid solvent is obtained. Except for a portion of the reflux, the recovered solvent is recycled to the extraction centrifuge. A small amount of supplemental solvent is added to compensate for the solvent loss during the separation process.

[0025] In the above recovery method, the high-boiling-point liquid phase at the bottom of the fractionation tower leaves the fractionation tower as a mixture of various organic components, mainly phenol. The intermediate products can be collected and further refined into various high-purity phenolic organic products.

[0026] The organic solvents used in the above-mentioned recovery methods are typically methyl isobutyl ketone, isopropyl ether, and N-503 kerosene.

[0027] Through the recycling method of this invention, the coal gas water produced in the coal gasification process is completely evaporated into water vapor to supply the gasification agent required by the gasifier. Most of the organic matter in the coal gas water is absorbed and separated by the solvent to obtain crude phenol products. The gasification workshop does not discharge coal gas water to the outside and it is recycled and utilized as a resource. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the organic matter recovery system in the coal gas-water concentrate of the fixed-bed gasifier of the present invention.

[0029] The markings in the diagram are as follows:

[0030] 1 Gas-water heat exchanger, 2 Scrubber, 3 Heater, 4 Humidification tower, 5 Centrifugal extractor, 6 Fractionating tower, 7 Circulating water pump, 8 Solid separator, 9 Solvent tank, 10 Crude phase intermediate product tank, 11 Reboiler, 12 Condenser, 13 Raffinate reflux pump. Detailed Implementation

[0031] The present invention will be further described below with reference to the accompanying drawings, but the present invention is not limited to the following embodiments.

[0032] like Figure 1 The diagram shown is a schematic of the structure of the organic matter recovery system in the coal gas-water concentrate of the fixed-bed gasifier provided by the present invention, including a coal gas-water heat exchanger 1, a scrubbing tower 2, a heater 3, a humidification tower 4, a centrifugal extractor 5, and a fractionation tower 6.

[0033] The gas outlet of the fixed-bed gasifier is connected to the gas inlet of the gas-water heat exchanger 1. Hot coal gas is heated by the gas-water heat exchanger 1 to produce steam (the tube side is connected to the gas delivery pipeline, and the shell side is connected to the water delivery pipeline; that is, the gas flows through the tube side, and the water flows through the shell side). The gas outlet of the gas-water heat exchanger 1 is connected to the gas inlet of the scrubbing tower 2, and the gas outlet of the scrubbing tower 2 is connected to the downstream user.

[0034] The washing water circulation pipeline of the scrubbing tower 2 is connected to the gas-water inlet at the bottom of the heater 3, and the gas-water outlet at the top of the heater 3 is connected to the top of the humidification tower 4 (wherein, the gas-water inlet is connected to the tube side of the heater, and the shell side is connected to the steam circulation pipeline, i.e., gas-water flows through the tube side, and water flows through the shell side). The circulating water outlet at the bottom of the humidification tower 4 is connected to the gas-water inlet through a gas-water circulation pipeline, and a circulating water pump 7 is installed on the gas-water circulation pipeline. The top of the humidification tower 4 is connected to the bottom of the fixed-bed gasifier, so that the humid air (air and water vapor) generated in the humidification tower 4 enters the gasifier, reacts with the coal as a gasifying agent to produce coal gas, and then leaves from the top of the gasifier. A steam heater is installed at the bottom of the humidification tower 4 to increase the evaporation rate of the gas-water.

[0035] The centrifugal extractor 5 is equipped with a concentrated water inlet, a solvent inlet, an aqueous phase outlet, and a solvent phase outlet. The concentrated water inlet is connected to the gas-water circulation pipeline (to discharge part of the concentrated gas-water from the circulation loop and recover the organic matter therein). A solid separator 8 is installed on the connected pipeline to separate and remove solid substances. The solvent inlet is connected to the solvent tank 9, the aqueous phase outlet is connected to the gas-water circulation pipeline, and the solvent phase outlet is connected to the fractionation tower 6, thereby introducing the concentrated liquid and organic solvent into the centrifugal extractor for mixing and extraction. The extracted aqueous phase is recycled back to the gas-water circulation loop to allow the water in it to continue to evaporate. The extracted organic phase enters the fractionation tower 6, and a raffinate reflux pump 13 is installed on the connected pipeline.

[0036] The top of the fractionating column 6 is connected to the solvent tank 9, and the bottom is connected to the crude phase intermediate product tank 10. A reboiler 11 is connected to the bottom of the fractionating column 6 to separate the solvent and organic components. A condenser 12 is connected between the fractionating column 6 and the solvent tank 9. The cooled solvent is refluxed back into the fractionating column 6, and part of it is refluxed back into the centrifugal extractor 5 for circulation.

[0037] When using the recovery system of this invention to recover organic matter from the gas-water concentrate of a fixed-bed gasifier, the following steps can be followed:

[0038] Coal reacts with gasifying agents air and steam in a fixed-bed gasifier to produce coal gas. The hot coal gas at the gasifier outlet enters a coal gas-water heat exchanger 1 for cooling, and then enters a scrubbing tower 2 to remove large molecular organic matter, resulting in coal gas-water containing organic matter. The coal gas-water is then sent to a heater 3 to be heated by steam. The coal gas-water flows through the tube side, while the steam flows through the shell side.

[0039] The heated coal gas-water mixture enters humidification tower 4, where air entering from the bottom comes into countercurrent contact with the hot coal gas-water mixture entering from the top. Part of the coal gas-water mixture evaporates into water vapor, which enters the air. When the air leaves humidification tower 4, it is nearly saturated with water vapor. Steam heating is installed at the bottom of humidification tower 4 to increase the evaporation rate of the coal gas-water mixture. The humid air then enters the gasifier, where air and water vapor act as gasifying agents, reacting with the coal to produce coal gas, which exits from the top of the gasifier.

[0040] The remaining water in humidification tower 4 cools down due to partial evaporation and heat absorption. The lower-temperature gas-water is circulated to the heat exchanger by the circulating water pump to continue being heated by steam.

[0041] As the water in the gas-water evaporates, the organic matter it contains gradually concentrates, increasing its concentration. Taking the original phenol concentration in the phenol-containing water as 2000 ppm, due to the lower circulation temperature resulting in less phenol evaporation, after a 10-fold concentration, the phenol concentration in the concentrate will approach 20000 ppm, or 2%. Part of the circulating gas-water is discharged from the circulation loop and, as concentrated water, is filtered by the solids separator 8 to remove solids. It is then sent to the concentrated water (phenol-containing water) centrifugal extractor 5, where it mixes with the solvent that enters simultaneously.

[0042] Organic components are more soluble in solvents (usually methyl isobutyl ketone or isopropyl ether, etc.) than in water. Most of the organic compounds, such as phenol, contained in concentrated water are absorbed by the solvent. Due to the density difference between solvent and water, the solvent is lighter. The centrifugal extractor 5 rotates to promote the separation of the solvent phase and the aqueous phase; the solvent phase and the aqueous phase flow continuously from the two outlets of the extractor, respectively.

[0043] The concentration of organic matter in the aqueous phase (raffinate) decreases, and it is sent back to the gas-water circulation loop to allow the water in it to continue to evaporate. The upper solvent phase is sent to the fractionation tower 6. After the mixture is heated by steam in the reboiler 11, due to the difference in boiling points between the solvent and the organic components, the low-boiling-point solvent gas rises to the top of the fractionation tower 6. After cooling, liquid solvent is obtained. Except for some reflux, the recovered solvent is recycled to the centrifugal extractor 5. A small amount of solvent is added to make up for the solvent loss during the separation process.

[0044] The high-boiling-point liquid phase leaving the bottom of fractionation column 6 is a mixture of various organic components, mainly phenol. The intermediate products can be collected and further refined into various high-purity phenolic organic products.

[0045] Through the above recycling process, the coal gas water produced in the coal gasification process is completely evaporated into water vapor to supply the gasification agent required by the gasifier. Most of the organic matter in the coal gas water is absorbed and separated by the solvent to obtain crude phenol products. The gasification workshop does not discharge coal gas water to the outside and it is recycled and utilized as a resource.

Claims

1. A system for recovering organic matter from coal gas-water concentrate in a fixed-bed gasifier, comprising a coal gas-water heat exchanger, a scrubbing tower, a heater, a humidification tower, a centrifugal extractor, and a fractionation tower; The gas outlet of the fixed-bed gasifier is connected to the gas inlet of the gas-water heat exchanger, the gas outlet of the gas-water heat exchanger is connected to the gas inlet of the scrubbing tower, and the gas outlet of the scrubbing tower is connected to the downstream user. The washing water circulation pipeline of the washing tower is connected to the gas and water inlet at the bottom of the heater, the gas and water outlet at the top of the heater is connected to the top of the humidification tower, the circulation water outlet at the bottom of the humidification tower is connected to the gas and water inlet through the gas and water circulation pipeline, and the top of the humidification tower is connected to the bottom of the fixed bed gasifier. The centrifugal extractor is equipped with a concentrated water inlet, a solvent inlet, an aqueous phase outlet, and a solvent phase outlet. The concentrated water inlet is connected to the gas-water circulation pipeline, the solvent inlet is connected to the solvent tank, and the solvent phase outlet is connected to the fractionation tower. The top of the fractionation column is connected to the solvent tank, and the bottom is connected to the coarse phase intermediate product tank; The gas-water inlet is connected to the tube side of the heater, and the shell side is connected to the steam circulation pipeline; The bottom of the humidification tower is equipped with a steam heater.

2. The recycling system according to claim 1, characterized in that: The tube side of the gas-water heat exchanger is connected to the gas transmission pipeline, and the shell side is connected to the water transmission pipeline.

3. The recycling system according to claim 1 or 2, characterized in that: A solid-liquid separator is installed on the pipeline connecting the concentrated water inlet and the gas-water circulation pipeline.

4. The recycling system according to claim 1 or 2, characterized in that: The aqueous phase outlet is connected to the gas-water circulation pipeline.

5. The recycling system according to claim 1 or 2, characterized in that: A reboiler is connected to the bottom of the fractionation column.

6. The recycling system according to claim 1 or 2, characterized in that: A condenser is provided between the distillation tower and the solvent tank.

7. The recycling system according to claim 1 or 2, characterized in that: The solvent tank is equipped with a solvent inlet.

8. A method for recovering organic matter from coal gas-water concentrate in a fixed-bed gasifier, comprising the following steps: The gas produced by the fixed-bed gasifier is fed into the gas-water heat exchanger of the recovery system according to any one of claims 1-7, and after being cooled, it enters the scrubbing tower and enters the downstream unit after being scrubbed. The gas-water produced by the scrubbing tower is fed into the heater for heating; the heated gas-water enters the humidification tower from the top and comes into countercurrent contact with the air / oxygen entering from the bottom. Part of the gas-water changes from liquid to steam and mixes with the air / oxygen. The resulting humid air containing water vapor enters the fixed-bed gasifier from the bottom as a gasifying agent. The remaining gas-water mixture in the humidification tower is circulated to the heater for further heating; The concentrated liquid produced during the circulation-evaporation process of the coal gas-water enters the centrifugal extractor and is extracted and centrifuged with the organic solvent therein. The resulting solvent phase enters the fractionation tower for fractionation, and the resulting aqueous phase is connected to the coal gas-water circulation pipeline. Crude phenol intermediate is obtained at the bottom of the fractionation tower, and the solvent obtained at the top of the tower is recycled back to the centrifugal extractor.

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