Gasified gas purification system and process

Abstract

The invention relates to a gasified gas purification system and process. The gasified gas purification system comprises a dust removal unit and a tar washing unit; the dust removal unit comprises a cyclone dust collector, a gasified gas heat exchanger and a filter; the cyclone dust collector is provided with a gasification furnace gasified gas inlet, a dust removal ash outlet and a dust removal gasified gas outlet; the filter is provided with a heat exchange gasified gas inlet, a filtered ash outlet and a filtered gasified gas outlet; the tar washing unit is provided with a gasified gas inlet, a detergent inlet, a gasified gas outlet and a washing liquid outlet; the dust removal gasified gas outlet is connected with the heat exchange gasified gas inlet through a first connecting pipeline, and the gasified gas heat exchanger is arranged on the first connecting pipeline; and the filtered gasified gas outlet is connected with the gasified gas inlet. Fly ash, tar and the like can be removed in order, and cross contamination is avoided.

Description

Technical Field

[0001] The invention relates to a gasification gas purification system and process. Background Art

[0002] As a renewable resource, the carbon emitted during the energy utilization of biomass is theoretically equal to the carbon fixed through photosynthesis during the growth of biomass, thus achieving a carbon-neutral cycle. Among all the ways of utilizing biomass, biomass gasification power generation technology, as a cutting-edge technology, has the advantages of flexible scale, high efficiency, and carbon neutrality. While solving the problem of reducing agricultural and forestry waste and recycling resources, it also provides clean electricity for rural areas, off-grid islands and other areas with distributed energy needs.

[0003] The raw gas produced from the gasifier inevitably contains a high content of tar, solid particles and other unexpected components, among which tar (i.e., all organic compounds with a boiling point above benzene) is particularly problematic. The biomass structure has a high volatile content, usually above 50%. This part of the volatile matter has weak thermal stability and is the first to precipitate in the thermochemical reaction, thus forming gas phase tar. Depending on the gasification form and raw materials, the tar content usually ranges from a few grams to tens of grams per standard cubic meter. The largest component in tar is monophenols (mainly phenol and guaiacol), followed by polycyclic aromatic hydrocarbons (PAH) with a smaller content of one order of magnitude. Such substances are very easy to condense in the transmission pipeline (350-400°C), resulting in a series of problems such as pipeline blockage, valve jamming, metal corrosion, fan stoppage, etc., causing the system to shut down. Too high a tar content makes it difficult to burn out in an internal combustion engine, forming particulate matter such as carbon black. At the same time, the naphthalene component in the tar will form crystals at the air intake of the internal combustion engine. The tar will also contaminate the spark plug, causing problems such as ignition difficulty.

[0004] The current mainstream gas purification technologies can be generally divided into two categories: dry and wet. The dry method includes mechanical dust removal, high-temperature tar cracking and other measures, while the wet method is mainly water washing. The OLGA (OiL-based GAswasher) gas purification system developed by the Netherlands Energy Research Center is designed based on solvent absorption of heavy tar. It uses two-stage removal units to remove different types of tar. The heavy tar is washed with a special oily solvent for cooling and absorption. The light tar in the gas is further dissolved in the washing oil by absorption, and then the washing oil is regenerated by steam stripping (using water vapor or hot air). The results show that the heavy tar in the raw gas is removed relatively completely, and the gas dew point temperature is reduced to 25°C; most of the phenolic and heterocyclic components in the tar are successfully removed. East China University of Science and Technology, Gaoyou Linyuan Technology Co., Ltd. and Shenyang Gas and Thermal Research and Design Institute of the Ministry of Construction jointly developed a multi-stage tar removal system based on medium and normal temperature electrostatic precipitator (patent publication number CN 10974353B). This system is for fixed bed upper suction gasification furnace type. The raw gas first passes through the first stage water spray tower to cool from 1000℃ to 80℃, and most of the fly ash is removed at the same time. Then it passes through the medium temperature electrostatic precipitator, and then further cools to 30℃ through the intercooler before entering the normal temperature electrostatic precipitator to remove tar. Guangdong Zhengpeng Biomass Energy Technology Co., Ltd. discloses a biomass gas purification and waste heat recovery system (patent publication number CN104073297 B), which directly removes fly ash from the gas at high temperature through the filter chamber. At the same time, the filter chamber plays the role of high temperature cracking tar, and all heat sources are provided by the high temperature flue gas generated by the combustion of gasification gas.

[0005] In summary, the prior art has the following four defects: First, in the traditional wet washing, tar and fly ash are removed simultaneously. However, the contact between tar and fly ash can form a gel that is not easy to flow, causing transportation difficulties or even pipeline blockage; if the wet spraying adopts water solvent, alkaline wastewater will be further generated after washing, increasing the cost of water treatment; at the same time, due to the huge difference in polarity between water and tar components themselves, it is difficult to achieve similar miscibility, so the absorption effect of tar, especially the removal effect of light tar, is poor; second, a part of the fly ash produced by biomass gasification is usually concentrated in the section with a smaller diameter (<10μm), which Some fly ash is difficult to remove by conventional methods such as cyclone separation; third, the removal of tar by electrostatic precipitator requires additional high-power electricity; the electrodes in the electrostatic precipitator are easily contaminated, and the electrodes need to be protected by inert gas to avoid explosion hazards caused by increased oxygen content in the gasification gas due to system leakage and other factors; fourth, the temperature required for high-temperature cracking of tar is usually above 1000°C, while the conventional gasification gas outlet temperature is around 600-800°C, and additional high-temperature gas is required to maintain the heat required for cracking; although the addition of catalysts can reduce the temperature required for tar cracking, it will bring about problems such as catalyst coking and deactivation, and fly ash pollution. Summary of the invention

[0006] The present invention provides a gasification gas purification system and process to solve the problems of poor removal effect of tar and fly ash in the prior art. The system can remove fly ash and tar in an orderly manner to avoid cross contamination.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a gasification gas purification system, which includes a dust removal unit and a tar washing unit;

[0009] The dust removal unit includes a cyclone dust collector, a gasification gas heat exchanger and a filter; the cyclone dust collector is provided with a gasification gas inlet of the gasifier, a dust removal ash outlet and a dust removal gasification gas outlet; the filter is provided with a heat exchange gasification gas inlet, a filter ash outlet and a filter gasification gas outlet;

[0010] The tar washing unit is provided with a gasified gas inlet, a washing agent inlet, a gasified gas outlet and a washing liquid outlet;

[0011] The dust removal gasification gas outlet is connected to the heat exchange gasification gas inlet via a first connecting pipe, and the gasification gas heat exchanger is arranged on the first connecting pipe; the filtering gasification gas outlet is connected to the gasification gas inlet.

[0012] In the present invention, the cyclone dust collector can be set as a primary or secondary device.

[0013] In the present invention, the filter element of the filter can be a ceramic filter element or a sintered metal filter element.

[0014] In the present invention, the gasification gas heat exchanger can adopt the form of heat transfer and cooling by high-temperature heat-conducting oil to prevent the tar in the gasification gas from precipitating during the rapid cooling process during the heat exchange of cold and hot gases.

[0015] In the present invention, the filter may also be provided with a filter element back-blowing air inlet.

[0016] In the present invention, the dust removal unit may further include a spiral ash discharger, and the dust removal gasification gas outlet and the filtered gasification gas outlet are connected to an ash inlet of the spiral ash discharger.

[0017] In the present invention, the tar washing unit may include a heavy tar absorption subunit and a light tar absorption subunit; the heavy tar absorption subunit includes a spray tower group, and the spray tower group is provided with a filtered gasification gas inlet, a spray agent inlet, a spray liquid outlet and a spray gasification gas outlet; the light tar absorption subunit includes an absorption tower, and the absorption tower is provided with a de-heavy gasification gas inlet, a de-light gasification gas outlet, an absorbent inlet and an absorption liquid outlet; the filtered gasification gas inlet is the gasification gas inlet of the tar washing unit, and is connected to the filtered gasification gas outlet, the spray gasification gas outlet is connected to the de-heavy gasification gas inlet, and the de-light gasification gas outlet is the gasification gas outlet of the tar washing unit.

[0018] Wherein, the spray tower group may include at least one spray tower, for example, two spray towers connected in series. The spray tower may be an empty tower or a bubble tower. The spray tower may be provided with 2-5 spray layers. Each spray layer may be provided with 3-12 nozzles. The top of the spray tower may be provided with a demister to prevent the spray agent from being carried out of the tower with the air flow. The heavy tar absorption subunit may also include a liquid-liquid separator, the liquid-liquid separator is provided with a spray liquid inlet, a regeneration spray agent outlet and a heavy tar outlet, the heavy tar outlet is located lower than the regeneration spray agent outlet, the spray liquid outlet is connected to the spray liquid inlet, and the regeneration spray agent outlet is connected to the spray agent inlet. The heavy tar absorption subunit may also include a gas-liquid separator, which is provided with a spray gasification gas inlet, a de-heavy gasification gas outlet and a liquid outlet, wherein the spray gasification gas inlet is connected to the spray gasification gas outlet, the de-heavy gasification gas outlet is connected to the de-heavy gasification gas inlet, and the liquid outlet is connected to the spray liquid inlet.

[0019] Wherein, the absorption tower may be a packed tower. The packing in the packed tower may be a multi-stage packing. The packing in the packed tower may be a regular geometric structure packing with anti-clogging. The light tar absorption subunit may also include a flash tank group, the flash tank group is provided with an absorption liquid inlet, a regenerated absorbent outlet and a light tar outlet, the absorption liquid inlet is connected to the absorption liquid outlet through a second connecting pipeline, and the regenerated absorbent outlet is connected to the absorbent inlet through a third connecting pipeline. The flash tank group includes at least one flash tank, for example, three flash tanks connected in series. An absorption liquid heat exchanger is provided on the second connecting pipeline. An external discharge branch may be provided on the third connecting pipeline, and the external discharge branch is close to the regenerated absorbent outlet. An absorbent replenishing branch may be provided on the third connecting pipeline, and the absorbent replenishing branch is close to the regenerated absorbent inlet. An absorbent heat exchanger may be provided on the third connecting pipeline.

[0020] In the present invention, the gasification gas outlet can be connected to a drying device. The drying device can be a partition cooling device or an active cyclone separation device.

[0021] In a second aspect, the present invention provides a gasification gas purification method, using the gasification gas purification system as described above, which comprises the following steps:

[0022] S1. The gasified gas at the outlet of the gasifier is initially separated from fly ash by the cyclone dust collector, and then heat-exchanged by the gasified gas heat exchanger to obtain gasified gas after heat exchange; the lower limit of the temperature of the gasified gas after heat exchange is the dew point temperature of heavy tar, and the upper limit is the tolerance temperature of the filter element of the filter; the gasified gas after heat exchange is filtered by the filter to obtain gasified gas after dust removal;

[0023] S2. The gasified gas after dust removal is washed by a tar washing unit.

[0024] In the present invention, in step S1, the gasification gas at the gasifier outlet may include CO, CO2, H2, CH4, N2, O2 and H2O.

[0025] In the present invention, in step S1, the tar content of the gasified gas at the outlet of the gasifier can be 600 mg / Nm 3 The tar may be an organic compound having a boiling point above that of benzene, including phenol, guaiacol, cresol, benzene, toluene, naphthalene, anthracene, phenanthrene and pyrene. Heavy tar may be a component having a molecular structure of more than three benzene rings. Light tar is a component having a molecular structure of two or fewer benzene rings.

[0026] In the present invention, in step S1, the fly ash content of the gasification gas at the outlet of the gasifier can be 1.44 g / Nm 3 .

[0027] In the present invention, in step S1, the temperature t1 of the gasification gas at the outlet of the gasifier can be 600-800°C, for example, 750°C, depending on the different gasification forms.

[0028] In the present invention, in step S1, after passing through the cyclone dust collector, the fly ash removal efficiency with a particle size of more than 10 μm reaches more than 98%, and the difference between the temperature t2 and t1 of the obtained gasification gas can be less than 50°C.

[0029] In the present invention, in step S1, the temperature t3 of the gasified gas after heat exchange may be 400-450°C.

[0030] In the present invention, in step S1, the temperature t4 of the gasified gas after dust removal can be 350-400°C.

[0031] In the present invention, the tar washing unit may include a heavy tar absorption subunit and a light tar absorption subunit, the heavy tar absorption subunit includes a spray tower group, and the light tar absorption subunit includes an absorption tower. Step S2 may be: the gasified gas after dust removal is sprayed by the spray tower group and then absorbed by the absorption tower to obtain the gasified gas after light tar removal.

[0032] According to the distribution of tar components in the gasification gas, the density of the spray agent used in the spray tower group can be lower than that of heavy tar, such as water, high carbon solvent or biodiesel. Each spray tower in the spray tower group can use the same spray agent.

[0033] Wherein, the spray tower group may include a first-level spray tower and a second-level spray tower connected in series, and the temperature t5 of the gasified gas at the outlet of the first-level spray tower after passing through the first-level spray tower may be 80-150°C, and is at least 20°C lower than the boiling point of the spray agent used in the spray tower group, preferably 30°C lower than the boiling point of the spray agent used in the spray tower group, for example, 160°C; the temperature t6 of the gasified gas at the outlet of the second-level spray tower after spraying through the second-level spray tower may be 40-150°C, for example, 60-70°C, and its dew point temperature is 30-50°C.

[0034] The temperature t7 of the gasified gas after heavy tar removal entering the absorption tower may be 40-150°C, for example 70°C.

[0035] The temperature t8 of the gasified gas after the light tar is removed may be 60°C or below.

[0036] The absorbent used in the absorption tower may be a solvent similar to the light tar component, preferably a high carbon alkane, such as n-octadecane.

[0037] Wherein, the light tar absorption subunit may also include a flash tank group, the temperature t9 of the absorption liquid entering the flash tank group may be 100-150°C, for example, 140°C, the pressure p1 may be 2-10kPa, for example, 3kPa, and the operating pressure of the flash tank in the flash tank group may be normal pressure or negative pressure, for example, 1kPa.

[0038] Among them, the temperature t of the circulating absorbent entering the absorption tower is 10 It can be 60°C or below.

[0039] In the present invention, the gasification gas outlet is connected to a drying device, and the gasification gas purification method may further include step S3, wherein the gasification gas after light tar removal is dried by the drying device to obtain purified gasification gas. The temperature of the purified gasification gas may be 40°C or below, preferably 30°C or below.

[0040] Without violating the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0041] The reagents and raw materials used in the present invention are commercially available.

[0042] The positive and progressive effects of the present invention are:

[0043] (1) The gasification gas purification system of the present invention has a dust removal unit including a medium temperature filter. After passing through the cyclone dust collector and the medium temperature filter, the particulate matter removal rate in the gasification gas can reach 99.5%, and the tar removal efficiency can be further improved to more than 90%, and the regeneration process of the spray agent and the absorbent is relatively simple;

[0044] (2) The gasification gas purification system of the present invention, the heavy tar absorption subunit may also include a gas-liquid separator, which can remove water vapor, aerosol, etc. carried by the gasification gas passing through the spray tower group, reduce the humidity of the gasification gas, and help improve the tar removal efficiency of the subsequent absorption tower; it may also include a dryer, which can remove water carried by aerosols, etc. generated by the gasification gas during the tar washing process, and can reduce the humidity of the gasification gas, which is conducive to improving the power generation efficiency of the internal combustion engine;

[0045] (3) The gasification gas purification process of the present invention is aimed at the large fly ash particles, fine fly ash particles, heavy tar, light tar, water and other unexpected components in the biomass gasification gas. The large fly ash particles, fine fly ash particles, heavy tar, light tar and water and other unexpected components in the gasification gas are removed in an orderly manner based on the dew point temperature, and the dry-wet combined process is combined to achieve deep purification;

[0046] (4) The gasification gas purification process of the present invention realizes efficient, stable, pollution-free, orderly deep purification without additional pollution emissions. The sensible heat of the gasification gas can be used as a heat source, and the waste generated is introduced into the gasification system for combustion, so the overall energy utilization efficiency is high. At the same time, the dew point temperature of the terminal gasification gas can be reduced to below room temperature, thereby avoiding the precipitation of tar in the system pipeline and ensuring the stable power generation of the downstream internal combustion engine.

[0047] (5) The gasification gas purification process of the present invention first passes through the spray tower group of the heavy tar absorption subunit to remove the aromatic components with a molecular weight of more than three benzene rings and some monophenols by gas-liquid contact, and then passes through the absorption tower of the light tar absorption subunit to remove the aromatic components with a molecular weight of naphthalene and below and some monophenols by absorption as the main method and condensation as the auxiliary method, so that the tar content is less than 50 mg / Nm 3 Even lower, meeting the intake requirements of long-term stable power generation of internal combustion engines. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 This is a schematic diagram of the gasification gas purification system in Example 1;

[0049] As shown in the figure: cyclone dust collector 1, gasification gas heat exchanger 2, filter 3, spiral ash discharger 4, primary spray tower 5, secondary spray tower 6, gas-liquid separator 7, liquid-liquid separator 8, absorption tower 9, absorption liquid heat exchanger 10, primary flash tank 11, secondary flash tank 12, tertiary flash tank 13, absorbent heat exchanger 15, drying equipment 17;

[0050] Gasified gas a at the outlet of gasifier, gasified gas after heat exchange b, gasified gas after dust removal c, back-blowing gas r, gasified gas d at the outlet of the first-stage spray tower, gasified gas e at the outlet of the second-stage spray tower, gasified gas f after heavy tar removal, gasified gas g after light tar removal, circulating spray agent h, spray liquid i, heavy tar j, absorption liquid k, flash regenerated absorbent l, light tar m, circulating absorbent n, fresh absorbent o, non-renewable material p, purified gasified gas q. DETAILED DESCRIPTION

[0051] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples. The experimental methods in the following examples without specifying specific conditions are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0052] Example 1

[0053] A gasification gas purification system, such as Figure 1, which includes a dust removal unit, a tar washing unit and a drying device 17; in view of the fact that fly ash in biomass gasification gas has a wide particle size distribution, the dust removal unit includes a cyclone dust collector 1, a gasification gas heat exchanger 2, a filter 3 and a spiral ash discharger 4; the cyclone dust collector 1 is provided with a gasification furnace gasification gas inlet, a dust removal ash outlet and a dust removal gasification gas outlet; the filter 3 is provided with a heat exchange gasification gas inlet, a filtering ash outlet and a filtering gasification gas outlet; the dust removal gasification gas outlet is connected to the heat exchange gasification gas inlet through a first connecting pipe, and the gasification gas heat exchanger 2 is arranged on the first connecting pipe; the dust removal gasification gas outlet and the filtering gasification gas outlet are connected to the ash inlet of the spiral ash discharger 4.

[0054] In this embodiment, the cyclone dust collector 1 is set as the first stage, and in other embodiments, it can be set as the first stage or the second stage according to the different dust content of the gasified gas. In this embodiment, the function of the gasification gas heat exchanger 2 is to lower the temperature of the gasified gas, and at the same time, the sensible heat of the high-temperature gasified gas can be used to heat the gasification agent required for the reaction of the upstream gasification system, such as air, water vapor, etc. In this embodiment, the gasification gas heat exchanger 2 can adopt the form of heat transfer and cooling by high-temperature heat transfer oil to prevent the tar in the gasified gas from precipitating during the rapid cooling process during the heat exchange of cold and hot gases. In this embodiment, the filter element of the filter 3 adopts a ceramic filter element, and in other embodiments, a sintered metal filter element can be used. The gasified gas c obtained after dust removal by the dust removal unit basically does not contain fly ash. The fly ash collected by the cyclone dust collector 1 and the filter 3 is discharged in real time by the spiral ash discharger 4.

[0055] In this embodiment, the tar washing unit includes a heavy tar absorption subunit and a light tar absorption subunit; the heavy tar absorption subunit includes a spray tower group consisting of a first-level spray tower 5 and a second-level spray tower 6 connected in series, a gas-liquid separator 7 and a liquid-liquid separator 8, the spray tower group is provided with a filtered gasification gas inlet, a spray agent inlet, a spray liquid outlet and a spray gasification gas outlet; the gas-liquid separator 7 is provided with a spray gasification gas inlet, a de-heavy gasification gas outlet and a liquid outlet; the liquid-liquid separator 8 is provided with a spray liquid inlet, a regeneration spray agent outlet and a heavy tar outlet, and the heavy tar outlet is located lower than the regeneration spray agent outlet; the filtered gasification gas inlet is connected to the filtered gasification gas outlet, the spray gasification gas inlet is connected to the spray gasification gas outlet, the liquid outlet is connected to the spray liquid inlet, the heavy tar outlet is located lower than the regeneration spray agent outlet, the spray liquid outlet is connected to the spray liquid inlet, and the regeneration spray agent outlet is connected to the spray agent inlet.

[0056] In this embodiment, the primary spray tower 5 and the secondary spray tower 6 are empty towers, each of which is provided with 3 spray layers, 6 nozzles in each spray layer, and a demister is provided on the top of the tower to prevent the spray agent from being carried out of the tower with the air flow. After spraying by the primary spray tower 5 and the secondary spray tower 6, most of the components with higher boiling points in the gasified gas, such as components with a molecular structure of more than three benzene rings, are basically removed, and components with a molecular structure of more than two benzene rings, such as naphthalene, are partially removed. The gasified gas purified from the secondary spray tower 6 further passes through the gas-liquid separator 7 to prevent fine droplets from being carried into the absorption tower 9. After the heavy tar is removed, the gasified gas f at the outlet of the heavy tar absorption subunit basically does not contain heavy tar components with a molecular structure of more than three benzene rings, and does not contain solid particles at all. The spray liquid i discharged from the first-stage spray tower 5, the second-stage spray tower 6 and the bottom of the gas-liquid separator 7 all enters the liquid-liquid separator 8. The separation adopts multi-stage static sedimentation. The upper supernatant forms a circulating spray agent h and enters the spray tower group, thereby forming a circulation of the spray agent. The heavy tar j at the bottom is discharged from the system and can be passed into the gasification system for combustion or enter the treatment unit.

[0057] In this embodiment, light tar is a component whose molecular structure contains two or less benzene rings, and the light tar absorption subunit includes an absorption tower 9 and a flash tank group consisting of a first-stage flash tank 11, a second-stage flash tank 12, and a third-stage flash tank 13 connected in series; the absorption tower 9 is provided with a de-heavy gasification gas inlet, a de-light gasification gas outlet, an absorbent inlet, and an absorption liquid outlet; the flash tank group is provided with an absorption liquid inlet, a regenerated absorbent outlet, and a light tar outlet; the de-heavy gasification gas outlet is connected to the de-heavy gasification gas inlet, the absorption liquid inlet is connected to the absorption liquid outlet through a second connecting pipeline, the regenerated absorbent outlet is connected to the absorbent inlet through a third connecting pipeline, and an absorption liquid heat exchanger 10 is provided on the second connecting pipeline. The third connecting pipeline is provided with an absorbent heat exchanger 15, an external discharge branch, and an absorbent supplement branch, the external discharge branch is close to the regenerated absorbent outlet, and the absorbent supplement branch is close to the regenerated absorbent inlet.

[0058] In this embodiment, the absorption tower 9 is a packed tower, using multi-stage packing, and the packing adopts a regular geometric structure packing that is resistant to clogging. In this embodiment, the heating medium of the absorption liquid heat exchanger 10 is superheated steam. In other embodiments, the heating medium can be the medium heated by the gasification gas heat exchanger 2, such as thermal oil. The light tar m precipitated from the flash tank group contains a small amount of absorbent and water, which is sent to the gasification system for incineration to avoid secondary pollution caused by emissions. After a long period of continuous operation, the absorbent can no longer be regenerated by flash evaporation, and the absorption effect is difficult to meet the expected requirements. At this time, this part of the non-renewable material p is discharged from the system and can be further introduced into the upstream gasification system for combustion. At the same time, fresh absorbent o is added to enter the system.

[0059] In this embodiment, the gasification gas outlet is connected to the drying device 17, and the drying device 17 adopts a partition cooling device. In other embodiments, according to the level of water content in the gasification gas, an active cyclone separation device can be used. In this embodiment, the drying device 17 is used to remove liquid droplets in the gasification gas, and the gasification gas q after drying and purification can be introduced into the internal combustion engine for power generation.

[0060] Example 2

[0061] A gasification gas purification method, wherein the gasification gas to be purified has a gas molar composition of about 15.0% CO, about 13.0% CO2, about 23.3% H2, about 1.9% CH4, about 39.1% N2, about 0.8% O2, and about 7.0% H2O; and a tar content of about 600 mg / Nm 3 The main components of tar are phenol, guaiacol, cresol, benzene, toluene, naphthalene, anthracene, phenanthrene, pyrene, etc. The dew point of tar is about 200℃; the fly ash content is about 1.44g / Nm 3 , wherein the mass proportion of particles with a diameter <5 μm is 29.6%, the mass proportion of particles with a diameter 5 μm ≤ <10 μm is 44.4%, and the mass proportion of particles with a diameter ≥10 μm is 26%. The gasification gas purification system in Example 1 is used to purify the gasification gas, including the following steps:

[0062] S1. The gasified gas a at the outlet of the gasifier is initially separated from fly ash by the cyclone dust collector 1, and the gasified gas temperature drops by no more than 50°C. After heat exchange by the gasified gas heat exchanger 2, the gasified gas b after heat exchange is obtained. The temperature t1 of the gasified gas a at the outlet of the gasifier is 750°C, and the temperature t3 of the gasified gas b after heat exchange is 450°C. The gasified gas b after heat exchange is filtered by the filter 3 to obtain the gasified gas c after dust removal. The operating temperature of the filter 3 is 400-450°C, and the temperature t4 of the gasified gas c after dust removal is 350-400°C. The dust content reaches 30mg / Nm 3 In this embodiment, the filter element of the filter 3 is back-blown and regenerated by back-blowing gas r, and the back-blowing gas r is nitrogen. The temperature of the back-blowing gas r needs to be kept close to the dew point temperature of the gasification gas, for example, 300-400°C. In other embodiments, the back-blowing gas r can be the flue gas discharged after the internal combustion engine generates electricity.

[0063] S2, the gasified gas c after dust removal is sprayed by the first-stage spray tower 5 to obtain the gasified gas d at the outlet of the first-stage spray tower, with a temperature t5 of 150°C, and then sprayed by the second-stage spray tower 6 to obtain the gasified gas e at the outlet of the second-stage spray tower with a temperature t6 of 70°C. After two-stage spraying, most of the components with higher boiling points in the gasified gas, such as components with a molecular structure of more than three benzene rings, are basically removed, and components with a molecular structure of more than two benzene rings, such as naphthalene, are partially removed. The gasified gas e at the outlet of the second-stage spray tower further passes through the gas-liquid separator 7 to prevent fine droplets from being carried into the absorption tower 9, and the gasified gas f after heavy tar removal is obtained, with a temperature t7 of about 70°C, which basically does not contain heavy tar components with a molecular structure of more than three benzene rings, and does not contain solid particles at all. The spray liquid i discharged from the first spray tower 5, the second spray tower 6 and the bottom of the gas-liquid separator 7 all enters the liquid-liquid separator 8, and the separation adopts multi-stage static sedimentation. The upper supernatant forms a circulating spray agent h and enters the spray tower group, thereby forming a spray agent circulation. The heavy tar j at the bottom is discharged from the system and can be passed into the gasification system for combustion or enter the processing unit. In this embodiment, the spray agent is biodiesel.

[0064] The gasified gas f after heavy tar removal is absorbed by the absorption tower 9 to obtain the gasified gas g after light tar removal; the temperature t8 of the gasified gas g after light tar removal is 60°C. The absorption liquid k is first heated to 140°C by the absorption liquid heat exchanger 10. The heating heat source is the sensible heat of the gasified gas in the gasification gas heat exchanger 2. After being pressurized, it enters the flash tank group. The inlet pressures in the first-stage flash tank 11, the second-stage flash tank 12 and the third-stage flash tank 13 are all 3kPa, and the operating pressures are all 1kPa. The required operating pressure can be provided by a vacuum pump. The light tar m precipitated from the flash tank group contains a small amount of absorbent and water, which is sent to the gasification system for incineration to avoid secondary pollution caused by emissions. The regenerated flash regenerated absorbent l is then cooled to 60°C by the absorbent heat exchanger 15 to obtain the circulating absorbent n and re-enter the absorption tower 9 for circulating absorption. In this embodiment, the absorbent is n-octadecane, and the temperature t of the circulating absorbent n entering the absorption tower 9 is 100%. 10 The temperature is 60℃. After a long period of continuous operation, the absorbent cannot be regenerated by flash evaporation, and the absorption effect is difficult to meet the expected requirements. At this time, this part of the non-renewable material p is discharged from the system and can be further introduced into the upstream gasification system for combustion. At the same time, fresh absorbent o is added to the system.

[0065] S3, the gasified gas g after light tar removal is dried by the drying device 17 to obtain the purified gasified gas q. The water content of the purified gasified gas q reaches 40mg / Nm 3 Below, temperature below 40℃, tar content less than 50mg / Nm 3 , which can meet the stable power generation needs of internal combustion engines.

Claims

1. A gasification gas purification system, characterized in that: It includes a dust removal unit and a tar washing unit; The dust removal unit comprises a cyclone dust collector (1), a gasification gas heat exchanger (2) and a filter (3); the cyclone dust collector (1) is provided with a gasification gas inlet for the gasifier, a dust removal ash outlet and a dust removal gasification gas outlet; the filter (3) is provided with a heat exchange gasification gas inlet, a filter ash outlet and a filter gasification gas outlet; The tar washing unit is provided with a gasified gas inlet, a washing agent inlet, a gasified gas outlet and a washing liquid outlet; The dust removal gasification gas outlet is connected to the heat exchange gasification gas inlet via a first connecting pipe, and the gasification gas heat exchanger (2) is arranged on the first connecting pipe; the filtered gasification gas outlet is connected to the gasification gas inlet.

2. The gasification gas purification system according to claim 1, characterized in that: The cyclone dust collector (1) is configured as a primary or secondary device; And / or, the filter element of the filter (3) is a ceramic filter element or a sintered metal filter element; And / or, the filter (3) is further provided with a filter element back-blowing air inlet; And / or, the dust removal unit further comprises a spiral ash discharger (4), and the dust removal gasification gas outlet and the filtered gasification gas outlet are connected to an ash inlet of the spiral ash discharger (4).

3. The gasification gas purification system according to claim 1, characterized in that: The tar washing unit includes a heavy tar absorption subunit and a light tar absorption subunit; The heavy tar absorption subunit comprises a spray tower group, wherein the spray tower group is provided with a filtered gasification gas inlet, a spray agent inlet, a spray liquid outlet and a spray gasification gas outlet; The light tar absorption subunit comprises an absorption tower (9), wherein the absorption tower (9) is provided with a deheavy gasification gas inlet, a delightened gasification gas outlet, an absorbent inlet and an absorption liquid outlet; The filtered gasified gas inlet is the gasified gas inlet of the tar washing unit and is connected to the filtered gasified gas outlet. The sprayed gasified gas outlet is connected to the deheavy gasified gas inlet. The delightened gasified gas outlet is the gasified gas outlet of the tar washing unit.

4. The gasification gas purification system according to claim 3, characterized in that: The spray tower group includes at least one spray tower, for example, two spray towers connected in series; the spray tower is preferably an empty tower or a bubble tower; the spray tower is preferably provided with 2-5 spray layers; each spray layer is preferably provided with 3-12 nozzles; the top of the spray tower is preferably provided with a demister; the heavy tar absorption subunit preferably also includes a liquid-liquid separator (8), the liquid-liquid separator (8) is provided with a spray liquid inlet, a regeneration spray agent outlet and a heavy tar outlet, and the heavy tar outlet is located at a low position. At the regeneration spray agent outlet, the spray liquid outlet is connected to the spray liquid inlet, and the regeneration spray agent outlet is connected to the spray agent inlet; the heavy tar absorption subunit preferably also includes a gas-liquid separator (7), the gas-liquid separator (7) is provided with a spray gasification gas inlet, a de-heavy gasification gas outlet and a liquid outlet, the spray gasification gas inlet is connected to the spray gasification gas outlet, the de-heavy gasification gas outlet is connected to the de-heavy gasification gas inlet, and the liquid outlet is connected to the spray liquid inlet; And / or, the absorption tower (9) is a packed tower; the packing in the packed tower is preferably a multi-stage packing; the packing in the packed tower is preferably a regular geometric structure packing; the light tar absorption subunit preferably also includes a flash tank group, the flash tank group is provided with an absorption liquid inlet, a regenerated absorbent outlet and a light tar outlet, the absorption liquid inlet is connected to the absorption liquid outlet via a second connecting pipeline, and the regenerated absorbent outlet is connected to the absorbent inlet via a third connecting pipeline; the flash tank group preferably includes at least one flash tank, for example, three flash tanks connected in series; the second connecting pipeline is preferably provided with an absorption liquid heat exchanger (10); the third connecting pipeline is preferably provided with an external discharge branch, the external discharge branch is close to the regenerated absorbent outlet; the third connecting pipeline is preferably provided with an absorbent replenishing branch, the absorbent replenishing branch is close to the regenerated absorbent inlet; the third connecting pipeline is preferably provided with an absorbent heat exchanger (15).

5. The gasification gas purification system according to claim 1, characterized in that: The gasification gas outlet is connected to a drying device (17); the drying device (17) preferably adopts a partition cooling device or an active cyclone separation device.

6. A gasification gas purification method, characterized in that: A gasification gas purification system according to any one of claims 1 to 5 is used, comprising the following steps: S1, the gasification gas (a) at the outlet of the gasifier is initially separated from fly ash by the cyclone dust collector (1), and then heat-exchanged by the gasification gas heat exchanger (2) to obtain the heat-exchanged gasification gas (b); the lower limit of the temperature of the heat-exchanged gasification gas (b) is the dew point temperature of heavy tar, and the upper limit is the tolerance temperature of the filter element of the filter (3); the heat-exchanged gasification gas (b) is filtered by the filter (3) to obtain the dust-removed gasification gas (c); S2. The gasified gas (c) after dust removal is washed by a tar washing unit.

7. The gasification gas purification method according to claim 6, characterized in that: In step S1, the gasification gas (a) at the gasifier outlet includes CO, CO2, H2, CH4, N2, O2 and H2O; And / or, in step S1, the tar content of the gasification gas (a) at the outlet of the gasifier is 600 mg / Nm 3 ; And / or, in step S1, the fly ash content of the gasification gas (a) at the gasifier outlet is 1.44 g / Nm 3 ; And / or, in step S1, the temperature t1 of the gasification gas (a) at the gasification furnace outlet is 600-800°C, for example, 750°C; And / or, in step S1, after passing through the cyclone dust collector (1), the difference between the temperature t2 and t1 of the gasified gas obtained is less than 50°C; and / or, in step S1, the temperature t3 of the gasified gas (b) after the heat exchange is 400-450°C; And / or, in step S1, the temperature t4 of the gasified gas (c) after dust removal is 350-400°C.

8. The gasification gas purification method according to claim 6, characterized in that: The tar washing unit comprises a heavy tar absorption subunit and a light tar absorption subunit, the heavy tar absorption subunit comprises a spray tower group, and the light tar absorption subunit comprises an absorption tower (9), and step S2 is: the gasified gas (c) after dust removal is sprayed by the spray tower group, and then absorbed by the absorption tower (9) to obtain the gasified gas (g) after light tar removal.

9. The gasification gas purification method according to claim 8, characterized in that: The spraying agent used in the spray tower group has a density lower than that of heavy tar, such as water, high carbon solvent or biodiesel; each spray tower in the spray tower group preferably uses the same spraying agent; And / or, the spray tower group comprises a first spray tower (5) and a second spray tower (6) connected in series, the temperature t5 of the gasified gas (d) at the outlet of the first spray tower after passing through the first spray tower (5) is 80-150°C, and is at least 20°C lower than the boiling point of the spray agent used in the spray tower group, preferably 30°C lower than the boiling point of the spray agent used in the spray tower group, for example, 160°C; the temperature t6 of the gasified gas (e) at the outlet of the second spray tower after spraying through the second spray tower (6) is 40-150°C, for example, 60-70°C, and its dew point temperature is 30-50°C; and / or, the temperature t7 of the gasified gas (f) after heavy tar removal entering the absorption tower (9) is 40-150° C., for example 70° C.; and / or, the temperature t8 of the gasification gas (g) after the light tar is removed is 60° C. or less; And / or, the absorbent used in the absorption tower (9) is a high carbon alkane, such as n-octadecane; And / or, the light tar absorption subunit further comprises a flash tank group, the temperature t9 of the absorption liquid entering the flash tank group is 100-150°C, for example, 140°C, the pressure p1 is 2-10kPa, for example, 3kPa, and the operating pressure of the flash tank in the flash tank group is normal pressure or negative pressure, for example, 1kPa; and / or, the temperature t of the circulating absorbent (n) entering the absorption tower (9) 10 60℃ or below.

10. The gasification gas purification method according to claim 6, characterized in that: The gasification gas outlet is connected to a drying device (17), and the gasification gas purification method further comprises step S3, wherein the gasification gas (g) after light tar removal is dried by the drying device (17) to obtain purified gasification gas (q); the temperature of the purified gasification gas (q) is preferably 40°C or below, for example, 30°C or below.

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