Gas purification system

Abstract

To provide a gas purification system capable of precisely removing impurities from a gasification gas produced from various carbon-containing substances (coal, carbon-based waste, biomass) as raw materials.SOLUTION: A gas purification system comprises: a halide removal means 11 that removes halides from a gasification gas by passing the gasification gas therethrough; a sulfur compound removal means 12 that removes sulfur compounds and hydrogen cyanide as a nitrogen compound from the gasification gas from which halogens have been removed; a heavy metal removal means 13 that removes heavy metals from the gasification gas from which the sulfur compounds and hydrogen cyanide as a nitrogen compound have been removed by passing the gasification gas therethrough; and an ammonia removal means 14 that washes the gasification gas with water to remove ammonia.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a gas purification system capable of precisely removing impurities from gasification gas. [Background technology]

[0002] Coal is found in a wide range of regions around the world, has large recoverable reserves, and its price is stable, resulting in a stable supply and a low price per calorific value. In thermal power generation using coal as fuel, for example, there is known equipment that uses coal gasification gas generated in a coal gasifier as fuel to drive a gas turbine to generate electricity, and also recovers exhaust heat from the gas turbine to generate steam, which then drives a steam turbine to generate electricity (see, for example, Patent Document 1).

[0003] The coal gasification gas generated in the coal gasification furnace contains impurities such as halogen compounds and sulfur compounds that can affect downstream equipment, as well as heavy metal impurities such as mercury and arsenic. Therefore, a gas purification system is used to remove the impurities from the coal gasification gas and turn it into fuel gas.

[0004] In recent years, in addition to coal, carbonaceous waste and biomass have increasingly been used as raw materials for generating fuel (gasification gas).The gasification gas generated in a gasifier is used as fuel for power generation in gas engines, gas turbines, fuel cells, etc., as well as raw material for chemical synthesis, so there is an increasing demand for more precise removal of impurities from the gasification gas purified in a gas purification system. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-171148 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in view of the above circumstances, and aims to provide a gas purification system that can precisely remove impurities from gasification gas produced using various carbon-containing substances (coal, carbonaceous waste, biomass) as raw materials. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, the gas purification system of the present invention according to claim 1 is a gas purification system for removing impurities from gasification gas produced by gasification gas generation, and is characterized by comprising: a halide removal means for circulating the gasification gas at a gas temperature above the dew point temperature and at a temperature around the temperature in the produced state, and removing halides; a sulfur compound removal means for circulating the gasification gas from which halides have been removed by the halide removal means, at a gas temperature above the dew point temperature, and removing hydrogen cyanide, which is a sulfur compound and a nitrogen compound; a heavy metal removal means for circulating the gasification gas from which sulfur compounds and hydrogen cyanide, which is a nitrogen compound, have been removed by the sulfur compound removal means, at a gas temperature above the dew point temperature, and removing heavy metals; and an ammonia removal means for washing the gasification gas from which heavy metals have been removed by the heavy metal removal means with water to remove ammonia.

[0008] In the present invention according to claim 1, the gasification gas at a gas temperature exceeding the dew point temperature is passed through halide removal means to remove halides in a dry manner, the gasification gas from which the halogens have been removed is passed through sulfur compound removal means at a gas temperature exceeding the dew point temperature to remove sulfur compounds and hydrogen cyanide, which is a nitrogen compound, in a dry manner, and the gasification gas from which the sulfur compounds and hydrogen cyanide, which is a nitrogen compound, have been removed is passed through heavy metal removal means at a gas temperature exceeding the dew point temperature to remove heavy metals in a dry manner. Then, the gasification gas from which the heavy metals have been removed by the heavy metal removal means is washed with water in an ammonia removal means to remove ammonia in a wet manner.

[0009] Therefore, after halides, sulfur compounds, hydrogen cyanide which is a nitrogen compound, and heavy metals are removed by dry processing, ammonia is washed and removed, and water-soluble impurities can be removed downstream. Furthermore, because water washing is performed after halides, sulfur compounds, hydrogen cyanide which is a nitrogen compound, and heavy metals have been removed, the impurities contained in the wastewater after water washing consist almost entirely of ammonium ions generated by the dissolution of ammonia, so the burden on wastewater treatment does not increase, and the burden on wastewater treatment is significantly reduced, making it possible to precisely remove impurities from the gasification gas.

[0010] In order to achieve the above-mentioned object, the gas purification system of the present invention according to claim 2 is a gas purification system for removing impurities from gasification gas produced by gasification gas generation, characterized in that it comprises: a halide removal means for circulating the gasification gas at a gas temperature above the dew point temperature and at a temperature around the temperature of the gasification gas when it is produced, and removing halides; a sulfur compound removal means for circulating the gasification gas from which halides have been removed by the halide removal means at a gas temperature above the dew point temperature, and removing sulfur compounds and hydrogen cyanide, which is a nitrogen compound; and a heavy metal removal means for circulating the gasification gas from which sulfur compounds have been removed by the sulfur compound removal means at a gas temperature below the dew point, and removing heavy metals.

[0011] In the present invention according to claim 2, the gasification gas at a gas temperature exceeding the dew point temperature is circulated through a halide removal means to remove the halides in a dry manner, the gasification gas from which the halogens have been removed is circulated through a sulfur compound removal means at a gas temperature exceeding the dew point temperature to remove the sulfur compounds and hydrogen cyanide, which is a nitrogen compound, in a dry manner, and the gasification gas from which the sulfur compounds and hydrogen cyanide have been removed is circulated through a heavy metal removal means at a gas temperature below the dew point to remove the heavy metals in a dry manner.

[0012] Therefore, after halides, sulfur compounds, and hydrogen cyanide, which is a nitrogen compound, are removed in a dry process at a gas temperature above the dew point, heavy metals are removed in a dry process at a gas temperature below the dew point, and in the heavy metal removal means, impurities such as tar (condensate) that condense when the temperature drops below the dew point are also removed.

[0013] Therefore, it is possible to remove impurities, including tar (condensate), even from gasification gas produced using various carbon-containing substances (coal, carbonaceous waste, biomass) as raw materials (for example, gasification gas produced using waste plastic as raw material and in which halogens increase significantly).

[0014] The present invention according to claim 3 is characterized in that, in the gas purification system according to claim 2, it is provided with an ammonia removal means for washing with water the gasification gas from which heavy metals have been removed by the heavy metal removal means to remove ammonia.

[0015] In the present invention according to claim 3, hydrogen cyanide, which is a halide, sulfur compound, and nitrogen compound, is removed in a dry manner at a gas temperature above the dew point, and heavy metals are removed in a dry manner at a gas temperature below the dew point before water washing is performed. Therefore, the impurities contained in the wastewater after water washing are almost entirely ammonium ions generated by the dissolution of ammonia, and the burden on wastewater treatment does not increase. The burden on wastewater treatment is significantly reduced, and impurities in the gasification gas can be precisely removed.

[0016] Furthermore, the gas purification system of the present invention according to claim 4 is characterized in that, in the gas purification system according to claim 3, it further comprises a dehumidifying means for dehumidifying the gasification gas that has been brought to a temperature below the dew point after the sulfur compounds and hydrogen cyanide, which is a nitrogen compound, have been removed by the sulfur compound removal means.

[0017] In the present invention according to claim 4, the gasification gas that has been brought to a temperature below the dew point is dehumidified by a dehumidifying means, and the dehumidifying means also removes impurities such as tar (condensate) that have condensed when the temperature is below the dew point, and the gasification gas from which moisture and impurities such as tar (condensate) have been removed is sent to a heavy metal removal means, where the heavy metals are removed in a dry manner.

[0018] Furthermore, the gas purification system of the present invention according to claim 5 is characterized in that, in the gas purification system according to claim 1, it is provided with a branching and distribution means for branching the gasification gas from which heavy metals have been removed by the heavy metal removal means into two routes and distributing it to the ammonia removal means and external utilization means (power generation means).

[0019] In the present invention according to claim 5, the gasification gas from which heavy metals have been removed by the metal removing means is branched into two routes by the branching and allocating means, and is allocated to the ammonia removing means and the external utilization means (power generating means).

[0020] The gas purification system of the present invention according to claim 6 is the gas purification system according to claim 1 or claim 3, further comprising a conversion means for converting ammonium ions generated when ammonia is removed by the ammonia removal means into ammonia or an ammonium salt, or ammonia and an ammonium salt, and recovering the ammonium ions.

[0021] In the present invention according to claim 6, ammonium ions (NH4 + ) is converted to ammonia (NH3) or ammonium salts, or ammonia (NH3) and ammonium salts, by a conversion means (for example, a conversion means by stripping), and recovered, thereby achieving reuse (recycling) of nitrogen.

[0022] Furthermore, a gas purification system of the present invention according to claim 7 is the gas purification system according to any one of claims 1 to 5, characterized in that the halides removed by the halide removal means include at least one of hydrogen chloride, hydrogen fluoride, and hydrogen bromide, and the halide removal means comprises first removal means that roughly removes halogens using an absorbent containing calcium in an atmosphere at a first temperature, and second removal means that precisely removes halogens using an absorbent containing sodium in an atmosphere at a second temperature different from the first temperature.

[0023] In the present invention according to claim 7, halogens are roughly removed in a dry manner by a first removal means using an absorbent containing calcium in an atmosphere at a first temperature which is approximately the temperature of the state in which the halogens are produced by the gasification means, and halogens are precisely removed in a dry manner by a second removal means using an absorbent containing sodium in an atmosphere at a second temperature which is different from the first temperature.

[0024] This makes it possible to precisely remove halides even from gasified gas that is produced using waste plastic, which is a carbonaceous waste, as a raw material and has a significantly high halide concentration.

[0025] Furthermore, the gas purification system of the present invention according to claim 8 is the gas purification system according to any one of claims 1 to 5, characterized in that the impurities removed by the sulfur compound removal means include at least one of hydrogen sulfide and carbonyl sulfide, which are sulfur compounds, and hydrogen cyanide, which is a nitrogen compound, and the sulfur compound removal means is an absorbent containing zinc.

[0026] In the eighth aspect of the present invention, sulfur compounds and cyanide compounds, which are nitrogen compounds, are removed in a dry manner using an absorbent containing zinc. The treatment temperature is set to an atmosphere of, for example, 450°C, higher than the operating temperature of the second means of halide removal. When zinc ferrite is used, for example, it is installed in a three-tower switching system, and continuous operation is carried out by switching between reduction, sulfidation (removal), and regeneration processes.

[0027] This allows the switching intervals between the three towers to be adjusted, making it possible to precisely remove sulfur compounds and hydrogen cyanide, even in cases where the concentration of sulfur compounds or hydrogen cyanide in the gasified gas fluctuates due to changes in the composition of the carbon-containing raw material.

[0028] In the present invention according to claim 8, for example, zinc oxide can be used to dryly remove sulfur compounds and hydrogen cyanide, which is a nitrogen compound. In this case, the treatment temperature is set to about the operating temperature of the second means of the halide removal means, for example, 300°C.

[0029] Furthermore, a gas purification system according to a ninth aspect of the present invention is the gas purification system according to any one of the first to fifth aspects, wherein the heavy metals removed by the heavy metal removal means include at least one of hydrogen selenide and arsenic hydride, and metallic mercury vapor, and the heavy metal removal means includes a first treatment device that removes selenium and arsenic using activated carbon, and a second treatment device that removes mercury using a copper-based absorbent that mainly contains copper and absorbs mercury, or impregnated activated carbon that removes mercury by adsorbing salts produced by a chemical reaction with mercury.

[0030] In the present invention according to claim 9, for example, selenium and arsenic are removed by dry treatment using activated carbon at a treatment temperature of 120°C, which is above the dew point (first treatment device), and mercury is removed by a copper-based absorbent that mainly contains copper and absorbs mercury, or by impregnated activated carbon that removes mercury by adsorbing salts formed by chemical reaction with mercury (second treatment device). Alternatively, selenium and arsenic are removed by dry treatment using activated carbon at a treatment temperature of 50°C, which is below the dew point (first treatment device), and mercury is removed by a copper-based absorbent that mainly contains copper and absorbs mercury, or by impregnated activated carbon that removes mercury by adsorbing salts formed by chemical reaction with mercury (second treatment device).

[0031] The heavy metal removal means can remove impurities other than heavy metals, such as boron, and impurities such as tar (condensate).

[0032] Furthermore, a gas purification system of the present invention according to claim 10 is the gas purification system according to any one of claims 1 to 5, further comprising a gasification furnace that generates a gasification gas to be sent to the halide removal means, wherein at least carbonaceous waste is fed into the gasification furnace as a raw material, and some or all of O2, H2O, and CO2 are supplied to the gasification furnace as gasifying agents, and a synthesis gas mainly composed of H2 and CO is generated by a gasification reaction.

[0033] In the present invention according to claim 10, the gasification gas produced in the gasification furnace is sent to the halide removal means, and the gasification agent is adjusted according to the proportion of carbonaceous waste contained as raw material, thereby sending gasification gas of stable composition.

[0034] Furthermore, the gas purification system of the present invention according to claim 11 is the gas purification system according to claim 1 or any one of claims 3 to 5, wherein the gasification gas from which ammonia has been removed by the ammonia removal means is utilized in a power generation and valuable resource concurrent production means for synthesizing chemical products and generating electricity, and the power generation and valuable resource concurrent production means comprises: a distribution means for distributing the gasification gas from which impurities have been removed into two paths; a chemical synthesis means for synthesizing chemical products using the gasification gas from one of the paths distributed by the distribution means; and a power generation means for generating electricity using the gasification gas from the other path distributed by the distribution means as fuel.

[0035] In the present invention according to claim 11, the gasification gas from which ammonia has been removed by the ammonia removal means is distributed by the distribution means, and the gasification gas on one path distributed by the distribution means is sent to the chemical synthesis means to synthesize chemical products, and the gasification gas on the other path distributed by the distribution means is sent as fuel to the power generation means. The operation of the distribution means can be linked to the supply status of the gasifying agents O2, HO, and CO2, the status of power demand, etc.

[0036] The chemical synthesis means can be applied to synthesize, for example, chemical products such as methane, methanol, olefins, oxalic acid, DME, etc. The power generation means can be applied to synthesize, for example, gas engines, gas turbines, fuel cells, etc. [Effects of the Invention]

[0037] The gas purification system of the present invention makes it possible to precisely remove impurities from gasification gas produced using various carbon-containing materials (coal, carbonaceous waste, biomass) as raw materials. [Brief explanation of the drawings]

[0038] [Figure 1] 1 is a conceptual diagram of a gasification facility equipped with a means for simultaneously producing electricity and valuable resources and having a gas purification system according to one embodiment of the present invention. [Figure 2] 1 is a block diagram of a gas purification system according to an embodiment of the present invention. [Figure 3] FIG. 10 is a conceptual diagram illustrating the state of impurity concentration. [Figure 4] FIG. 1 is a schematic diagram of a first embodiment of a gas purification means (including temperature conditions). [Figure 5] FIG. 10 is a schematic diagram of a second embodiment of the gas purification means (including temperature conditions). [Figure 6] FIG. 10 is a schematic diagram of a third embodiment of the gas purification means (including temperature conditions). [Figure 7] FIG. 10 is a schematic diagram of a fourth embodiment of the gas purification means (including temperature conditions). DETAILED DESCRIPTION OF THE INVENTION

[0039] An energy supply system (gasification facility equipped with means for power generation and valuable resource co-production) having a gas purification system according to one embodiment of the present invention will be described with reference to Figure 1. Figure 1 shows the overall concept of a gasification facility equipped with means for power generation and valuable resource co-production and having a gas purification system according to one embodiment of the present invention.

[0040] The energy supply system of this embodiment is a system having a power generation means for generating electricity and a chemical synthesis means for synthesizing chemical products as a means for generating electricity and simultaneously producing valuable materials, and impurities in the gasification gas obtained in the gasification furnace equipment are removed by the gas purification system of the present invention, and the gasification gas from which the impurities have been removed is used to generate electricity and synthesize chemical products.

[0041] As shown in the figure, the means for generating electricity and producing valuable resources is equipped with a gasification furnace 2 that gasifies raw materials (coal, carbonaceous waste, biomass) together with a gasifying agent to produce gasification gas mainly composed of H2 and CO.

[0042] Char (unburned carbon components including ash) is separated from the gasification gas obtained in the gasification furnace 2 by separation means (cyclone, filter, etc.) 3, and the separated char is circulated to the gasification furnace 2 via a circulation path 4. The circulation path 4 allows the char contained in the gasification gas obtained in the gasification furnace 2 to be separated and circulated to the gasification furnace 2.

[0043] It is also possible to store a portion of the char from the circulation path 4. By storing a portion of the char, it is possible to reduce CO2 emissions and also to reduce the CO in the synthesis gas, thereby further increasing the H2 / CO ratio.

[0044] The gasification gas from which char has been separated in the separation means 3 has the H2 ratio adjusted in the shift reaction means 5, and impurities removed in the gas purification means 6. The gasification gas from which impurities have been removed is sent to the distribution means 7. A chemical synthesis means 8 is connected to one side of the path of the distribution means 7, and a power generation means 9 is connected to the other side of the path of the distribution means 7.

[0045] Although an example is shown in which the shift reaction means 5 is provided between the separation means 3 and the gas purification means 6, the position of the shift reaction means 5 does not necessarily have to be at this location, and it can also be provided, for example, in the path between the distribution means 7 and the chemical synthesis means 8.

[0046] When the gasification gas is diverted to one of the paths, the gasification gas is sent to the chemical synthesis means 8 and used for chemical synthesis. When the gasification gas is diverted to the other path, the gasification gas is used as fuel for the combustion means of the power generation means 9 (for example, a combustor that obtains combustion gas to drive an expansion turbine).

[0047] The exhaust gas from the power generation means 9, for example, exhaust gas that has completed its work in an expansion turbine, has CO2 separated from it, and a portion of the separated and recovered CO2 is used as CO2 as a gasifying agent by the circulation means 10 and fed into the gasification furnace 2.

[0048] The chemical products synthesized by the chemical synthesis means 8 can be applied to the synthesis of, for example, methane, methanol, olefins, oxalic acid, DME, etc. The power generation means 9 can also be applied to a fuel cell in which the gasification gas is used as the anode gas.

[0049] O2, H2O, and CO2 are used as gasifying agents, and the supply conditions (supply ratios) of the gasifying agents O2, H2O, and CO2 are adjusted by the control means 1. That is, the supply conditions of the gasifying agents O2, H2O, and CO2 are adjusted by the control means 1, and the ratio of H2 to CO (H2 / CO ratio) in the gasification gas that is generated is controlled to a desired state.

[0050] This makes it possible to obtain gasification gas suitable for power generation and chemical synthesis, and by adjusting the gasification agent, it becomes possible to effectively use waste, the processing volume of which varies, and biomass, the procurement volume of which varies, together with coal to obtain synthesis gas.

[0051] The gas purification means will be outlined with reference to Fig. 2. Fig. 2 shows a block diagram of a gas purification system according to one embodiment of the present invention.

[0052] As shown in the figure, the gas purification means 6 has a halide removal means 11 through which the gasification gas from the separation means 3 flows and which removes halides. The gasification gas is sent to the halide removal means 11 at a temperature above the dew point temperature and at a temperature around the temperature of the gasification gas produced in the gasification furnace 2. The halides removed by the halide removal means 11 include hydrogen chloride (HCl), hydrogen fluoride (HF), and hydrogen bromide (HBr).

[0053] The gasification gas from which halides have been removed by the halide removal means 11 is sent to the sulfur compound removal means 12. In the sulfur compound removal means 12, the gasification gas flows at a gas temperature exceeding the dew point temperature, and impurities are removed. The impurities removed by the sulfur compound removal means 12 include sulfur compounds (hydrogen sulfide: H2S, carbonyl sulfide: COS) and nitrogen compounds (hydrogen cyanide: HCN).

[0054] The gasification gas from which sulfur compounds and hydrogen cyanide have been removed by the sulfur compound removal means 12 is sent to the heavy metal removal means 13 at a gas temperature above the dew point temperature, or after being cooled to a gas temperature below the dew point. The heavy metals removed by the heavy metal removal means 13 include metallic mercury vapor (Hg), hydrogen selenide (H2Se), and arsenic hydride (AsH3).

[0055] Then, the gasification gas from which heavy metals have been removed by the heavy metal removal means 13 is sent to the ammonia removal means 14. In the ammonia removal means 14, the gasification gas from which heavy metals have been removed is washed with water to remove ammonia (NH3).

[0056] That is, in the gas purification means 6, the gasified gas at a gas temperature exceeding the dew point temperature is passed through halide removal means 11, where halides are removed in a dry manner, the gasified gas from which halides have been removed is passed through sulfur compound removal means 12 at a gas temperature exceeding the dew point temperature, where sulfur compounds and hydrogen cyanide, which is a nitrogen compound, are removed in a dry manner, and the gasified gas from which impurities (sulfur compounds, hydrogen cyanide) have been removed is passed through heavy metal removal means 13 at a gas temperature exceeding the dew point temperature or at a gas temperature below the dew point after being cooled, where heavy metals are removed in a dry manner. Then, the gasified gas from which heavy metals have been removed in the heavy metal removal means 13 is washed with water in ammonia removal means 14, where ammonia (NH3) is removed in a wet manner.

[0057] For this reason, after hydrogen cyanide and heavy metals among the halides, sulfur compounds, and nitrogen compounds are removed by dry processing, ammonia (NH3) is removed by rinsing with water. Then, because rinsing with water is carried out after hydrogen cyanide and heavy metals among the halides, sulfur compounds, and nitrogen compounds have been removed, the only impurities contained in the wastewater after rinsing with water are ammonium ions generated by the dissolution of ammonia (NH3), so there is no need to increase the burden of wastewater treatment, and the burden of wastewater treatment can be significantly reduced and impurities in the gasification gas can be precisely removed.

[0058] In addition, ammonium ions (NH4 + ) can be sent to the conversion means 15 (for example, conversion means by stripping). The conversion means 15 converts the ammonium ions (NH4 + ) is converted to ammonia (NH3) or ammonium salts, or ammonia (NH3) and ammonium salts, and recovered. This achieves the reuse (recycling) of nitrogen.

[0059] The state of the concentration of impurities removed by the gas purifying means 6 will be described with reference to Fig. 3. Fig. 3 shows the state of the concentration of impurities in the gas purifying means 6.

[0060] As shown in the figure, the impurities present at the inlet of the halide removal means 11 are HCl (narrowly spaced diagonal lines sloping downward to the left), other halides (narrowly spaced diagonal lines sloping downward to the right), H2S (widely spaced diagonal lines sloping downward to the left), COS (widely spaced diagonal lines sloping downward to the right), HCN (narrowly spaced mesh), NH3 (open), As (widely spaced mesh), Se (gray), and Hg (black), and the inlet temperature to the halide removal means 11 is set to, for example, 250°C.

[0061] In the halide removal means 11, HCl (narrowly spaced diagonal lines sloping downward to the left) and other halides (narrowly spaced diagonal lines sloping downward to the right) are roughly removed by a first removal means 21 using a calcium-containing absorbent (slaked lime, quicklime, limestone), and HCl (widely spaced diagonal lines sloping downward to the left) and other halides (widely spaced diagonal lines sloping downward to the right) are precisely removed by a second removal means 22 using a sodium-containing absorbent (sodium aluminate, COS conversion catalyst, and sodium aluminate).

[0062] In the sulfur compound removal means 12, H2S (widely spaced diagonal lines sloping downward to the left), COS (widely spaced diagonal lines sloping downward to the right), and HCN (narrowly spaced mesh) are removed using an absorbent containing zinc (zinc ferrite or zinc oxide).

[0063] In the heavy metal removal means 13, As (wide mesh) and Se (gray) are removed in a first treatment device 31 using activated carbon, and Hg (black) is removed in a second treatment device 32 using a copper-based absorbent that mainly uses copper to absorb mercury, or impregnated activated carbon that removes mercury by adsorbing salts produced by a chemical reaction with mercury.

[0064] Then, in the ammonia removal means 14, NH3 (white portion) is removed by washing with water, and a gasification gas of, for example, 50°C is obtained.

[0065] Specific examples of the gas purification means 6 will be described with reference to Figures 4 to 7. Figures 4 to 7 show the schematic configuration (system status) and temperature status of first to fourth examples of the gas purification means, where (a) shows the schematic system of the processing equipment, and (b) shows the temperature status during each process.

[0066] First Example The first embodiment will be described with reference to FIG.

[0067] As shown in Figures 4(a) and (b), the halide removal means 11 includes a first removal means 21 that roughly removes halogens using hydrated lime (Ca(OH)2), an absorbent containing calcium, in an atmosphere at a first temperature (e.g., 250°C), and a second removal means 22 that precisely removes halogens using sodium aluminate (NaAlO2), an absorbent containing sodium, in an atmosphere at a second temperature (e.g., 350°C) that is different from the first temperature (a temperature higher than the first temperature).

[0068] The first removal means 21 roughly removes halides in a dry manner using hydrated lime (Ca(OH)2). Temperature adjustment means 41 is provided between the first removal means 21 and the second removal means 22, and the temperature of the gasification gas from which the halides have been roughly removed is raised to 250°C to 350°C. The second removal means 22 precisely removes halides in a dry manner using sodium aluminate (NaAlO2).

[0069] This makes it possible to precisely remove halides even from gasified gas that is produced using waste plastic, which is a carbonaceous waste, as a raw material and has a significantly high halide concentration.

[0070] The sulfur compound removal means 12 is constructed by filling a reactor with zinc ferrite (ZnFe2O4), an absorbent containing zinc. The gasification gas is passed through a honeycomb made of zinc ferrite, and in addition to sulfur compounds (hydrogen sulfide: H2S, carbonyl sulfide: COS), nitrogen compounds (hydrogen cyanide: HCN) are also removed in a dry process.

[0071] The treatment temperature in the sulfur compound removal means 12 is set to, for example, an atmosphere of 450°C, which is higher than the operating temperature in the second removal means 22 of the halide removal means 11. The gasification gas from which halogens have been removed in the second removal means 22 is heated to 450°C by temperature adjustment means 42 and sent to the sulfur compound removal means 12. The zinc ferrite is, for example, placed in a three-tower switching system facility, and continuous operation is carried out by switching between reduction, sulfidation (removal), and regeneration processes.

[0072] This allows the switching intervals between the three towers to be adjusted, making it possible to precisely remove sulfur compounds and hydrogen cyanide, even in cases where the concentration of sulfur compounds or hydrogen cyanide in the gasified gas fluctuates due to changes in the composition of the carbon-containing raw material.

[0073] The gasification gas from which sulfur compounds (hydrogen sulfide: H2S, carbonyl sulfide: COS) and the nitrogen compound hydrogen cyanide (HCN) have been removed by the sulfur compound removal means 12 is cooled to a temperature below the dew point (e.g., 50°C) by the temperature adjustment means 43 (heat exchange means), dehumidified by the dehumidification means 44, and then sent to the heavy metal removal means 13.

[0074] The gasification gas that has been washed with water by the ammonia removal means 14, which will be described later, may be used as the cooling medium for the temperature adjustment means 43. The gasification gas that has been washed with water by the ammonia removal means 14 is heated by the gasification gas from the sulfur compound removal means 12 (temperature adjustment means 43), and is sent to the distribution means 7.

[0075] The heavy metal removal means 13 includes a first treatment device 31 filled with activated carbon that removes selenium (Se) and arsenic (As), and a second treatment device 32 filled with a copper-based absorbent that mainly contains copper and absorbs mercury (Hg). The second treatment device 32 can also be filled with impregnated activated carbon that removes mercury by adsorbing salts generated by a chemical reaction with mercury.

[0076] In the heavy metal removal means 13, selenium (Se) and arsenic (As) are removed in a dry manner using activated carbon at a processing temperature below the dew point (e.g., 50°C), and mercury (Hg) is removed in a dry manner using a copper-based absorbent at a processing temperature below the dew point (e.g., 50°C).

[0077] Therefore, after halides, sulfur compounds, and hydrogen cyanide, which is a nitrogen compound, are removed by a dry process at a temperature above the dew point, heavy metals are removed by a dry process at a temperature below the dew point, and impurities such as tar (condensate) are also removed in the heavy metal removal means 13.

[0078] Therefore, even in the case of gasification gas produced using various carbon-containing materials (coal, carbonaceous waste, biomass) as raw materials (for example, gasification gas produced using waste plastic as raw material and in which halogens increase significantly), it is possible to remove impurities, including tar (condensate), that condenses when the temperature drops below the dew point.

[0079] The gasification gas from which heavy metals have been removed by the heavy metal removal means 13 is sent to the ammonia removal means 14. The ammonia removal means 14 is a scrubber 35 that removes ammonia (NH3) by washing with water. The gasification gas from which ammonia (NH3) has been removed by the ammonia removal means 14 (to 50°C, for example) is heated by the temperature adjustment means 43 and distributed to two routes by the distribution means 7. The gasification gas in one route distributed by the distribution means 7 is sent to the chemical synthesis means 8 where chemical products are synthesized, and the gasification gas in the other route distributed by the distribution means 7 is sent to the power generation means 9 as fuel.

[0080] In the scrubber 35, water washing is performed after the halides, sulfur compounds, nitrogen compounds, and heavy metals are removed, so the only impurities contained in the wastewater after water washing are ammonium ions generated by the dissolution of ammonia (NH3), and the burden on wastewater treatment does not increase.The burden on wastewater treatment is significantly reduced, and impurities in the gasification gas can be precisely removed.

[0081] The ammonium ion (NH4 + ) is sent to the conversion means 15 (see FIG. 2), and the conversion means 15 (see FIG. 2) converts the ammonium ions (NH4 + ) is converted to ammonia (NH3) or ammonium salts, or ammonia (NH3) and ammonium salts, and recovered. This achieves the reuse (recycling) of nitrogen.

[0082] Second Example The second embodiment will be described with reference to Fig. 5. The same members as those in the first embodiment shown in Fig. 4 are given the same reference numerals.

[0083] The equipment of the second embodiment includes a second removal means 24 instead of the second removal means 22 of the first embodiment. That is, as shown in Figures 5(a) and 5(b), a COS conversion catalyst and sodium aluminate (NaAlO2) are used as the second removal means 24. Then, in the temperature adjustment means 41, the gasification gas at 250°C from which halides have been roughly removed by the first removal means 21 is heated to 300°C (a temperature higher than the first temperature).

[0084] The second removal means 24 performs precision dry removal of halides using sodium aluminate (NaAlO2) at a treatment temperature of 300°C. Note that the COS conversion catalyst converts most of carbonyl sulfide (COS), a sulfur compound that is difficult to remove, into hydrogen sulfide (HS), a sulfur compound that is easier to remove.

[0085] The equipment of the second embodiment is configured such that zinc oxide (ZnO) is filled in a reactor as the sulfur compound removal means 12. In the sulfur compound removal means 12, nitrogen compounds (hydrogen cyanide: HCN) are removed in a dry process in addition to sulfur compounds (hydrogen sulfide: H2S, carbonyl sulfide: COS) at a treatment temperature of 300°C, which is the same temperature as that of the second removal means 24. Therefore, the temperature adjustment means 42 (see FIG. 4) is not required in the second embodiment.

[0086] This allows zinc oxide (ZnO) to be used to remove sulfur compounds (hydrogen sulfide, carbonyl sulfide) and hydrogen cyanide, a nitrogen compound, thereby simplifying the process by eliminating the need for temperature control means, and by making hydrogen sulfide the main component of sulfur compounds, sulfur compounds (hydrogen sulfide, carbonyl sulfide) and hydrogen cyanide, a nitrogen compound, can be efficiently removed in a dry process.

[0087] As in the first embodiment, the sulfur compound removing means 12 can also use zinc ferrite (ZnFe2O4).

[0088] The gasification gas from which sulfur compounds and hydrogen cyanide, a nitrogen compound, have been removed in a dry manner by the sulfur compound removal means 12 using zinc oxide (ZnO) is cooled to a temperature below the dew point (for example, 50°C) by the temperature adjustment means 43 (heat exchange means), as in the first embodiment, and then dehumidified by the dehumidification means 44. Thereafter, the gasification gas is sent to the heavy metal removal means 13 where the heavy metals are removed in a dry manner, and the ammonia (NH3) is removed by the ammonia removal means 14.

[0089] Third Example The third embodiment will be described with reference to Fig. 6. The same members as those in the first embodiment shown in Fig. 4 are given the same reference numerals.

[0090] 6(a) and 6(b), in the equipment of the third embodiment, the gasification gas from which halogens have been precisely removed using sodium aluminate (NaAlO2) and from which sulfur compounds have been removed using zinc ferrite (ZnFe2O4) is cooled to a temperature above the dew point (e.g., 120°C) by temperature adjustment means 43 (heat exchange means) and sent to heavy metal removal means 13. In heavy metal removal means 13, heavy metals are removed in a dry manner at a treatment temperature above the dew point.

[0091] A branching / distribution means 51 is provided in the path between the heavy metal removal means 13 and the ammonia removal means 14, and the gasification gas is branched into two paths by the branching / distribution means 51. One of the paths branched by the branching / distribution means 51 is connected to the ammonia removal means 14, and the gasification gas from which heavy metals have been removed is sent to the ammonia removal means 14. The gasification gas from which ammonia (NH3) has been removed by the ammonia removal means 14 is sent to the chemical synthesis means 8. The other path branched by the branching / distribution means 51 is connected to the power generation means 9, and the gasification gas before the ammonia (NH3) has been removed is sent to the power generation means 9, which is an external utilization means.

[0092] For this reason, halogens are precisely removed using sodium aluminate (NaAlO2), sulfur compounds are removed using zinc ferrite (ZnFe2O4), and the gasification gas from which heavy metals have been dry-removed by the heavy metal removal means 13 is branched into two routes by the branching and distribution means 51 and can be distributed to the ammonia removal means 14 (chemical synthesis means 8) and the power generation means 9, and the gasification gas at a temperature above the dew point before ammonia (NH3) that can be used as fuel is removed can be supplied to the power generation means 9.

[0093] <Fourth Example> The fourth embodiment will be described with reference to Fig. 7. The same members as those in the second embodiment shown in Fig. 5 are given the same reference numerals.

[0094] 7(a) and 7(b), in the equipment of the fourth embodiment, halides are precisely removed using sodium aluminate (NaAlO2), most of the sulfur compound carbonyl sulfide (COS) is converted to hydrogen sulfide (HS) using a COS conversion catalyst, and the sulfur compounds and nitrogen compound hydrogen cyanide (HCN) are removed from the gasified gas using zinc oxide (ZnO). The gasified gas is then cooled to a temperature above the dew point (e.g., 120°C) using temperature adjustment means 43 (heat exchange means) and sent to heavy metal removal means 13. In heavy metal removal means 13, heavy metals are dry-removed at a treatment temperature above the dew point.

[0095] As in the third embodiment, a branching and distribution means 51 is provided in the path between the heavy metal removal means 13 and the ammonia removal means 14, and the gasification gas is branched into two paths by the branching and distribution means 51. One of the paths branched by the branching and distribution means 51 is connected to the ammonia removal means 14, and the gasification gas from which heavy metals have been removed is sent to the ammonia removal means 14. The gasification gas from which ammonia (NH3) has been removed by the ammonia removal means 14 is sent to the chemical synthesis means 8. The other path branched by the branching and distribution means 51 is connected to the power generation means 9, and the gasification gas before the ammonia has been removed is sent to the power generation means 9, which is an external utilization means.

[0096] Therefore, halogens are precisely removed using a COS conversion catalyst and sodium aluminate (NaAlO2), sulfur compounds are removed using zinc oxide (ZnO), and the gasification gas from which heavy metals have been dry-removed by the heavy metal removal means 13 is branched into two routes by the branching and distribution means 51 and can be distributed to the ammonia removal means 14 (chemical synthesis means 8) and the power generation means 9, and the gasification gas at a temperature above the dew point before ammonia (NH3) that can be used as fuel is removed can be supplied to the power generation means 9.

[0097] The gas purification system described above is capable of precisely removing impurities such as halides, sulfur compounds, hydrogen cyanide (a nitrogen compound), heavy metals, and ammonia (NH3) contained in gasification gas generated using various carbon-containing materials (coal, carbonaceous waste, biomass) as feedstock. It is also possible to remove impurities such as tar (condensate) that condenses due to a drop in gas temperature. The ammonia removal means 14, the only wet process, is performed after other impurities have been removed. Therefore, the only impurities in the wastewater are ammonium ions generated by the dissolution of ammonia (NH3). This significantly reduces the burden on wastewater treatment and enables precise removal of impurities from the gasification gas. [Industrial Applicability]

[0098] The present invention can be used in the industrial field of gas purification systems. [Explanation of symbols]

[0099] 1. Control measures 2 Gasifier 3 Separation means 4 Circulation Route 5. Shift reaction means 6 Gas purification means 7 Sorting method 8 Chemical synthesis means 9. Means of power generation 10 Circulation means 11 Halide removal means 12 Means for removing sulfur compounds 13 Heavy metal removal means 14 Ammonia removal means 15 Conversion methods 21 First removal means 22, 24 Second removal means 31 First processing device 32 Second processing device 35 Scrubba 41, 42, 43 Temperature adjustment means 44 Dehumidification means 51 Branching and allocation method

Claims

1. A gas purification system for removing impurities from gasification gas generated by gasification gas generation, a halide removal means for circulating the gasified gas at a temperature exceeding the dew point temperature and approximately equal to the temperature at which the gasified gas was generated, thereby removing the halide; a sulfur compound removal means for circulating the gasification gas from which halides have been removed by the halide removal means at a gas temperature exceeding the dew point temperature, thereby removing sulfur compounds and hydrogen cyanide, which is a nitrogen compound; a heavy metal removal means for removing heavy metals from the gasification gas from which the sulfur compounds and hydrogen cyanide, which is a nitrogen compound, have been removed by the sulfur compound removal means by circulating the gasification gas at a gas temperature exceeding the dew point temperature; an ammonia removal means for removing ammonia by washing with water the gasification gas from which heavy metals have been removed by the heavy metal removal means; A gas purification system comprising:

2. A gas purification system for removing impurities from gasification gas generated by gasification gas generation, a halide removal means for circulating the gasified gas at a temperature exceeding the dew point temperature and approximately equal to the temperature at which the gasified gas was generated, thereby removing the halide; a sulfur compound removal means for circulating the gasification gas from which halides have been removed by the halide removal means at a gas temperature exceeding the dew point temperature, thereby removing sulfur compounds and hydrogen cyanide, which is a nitrogen compound; a heavy metal removal means for removing heavy metals from the gasification gas from which the sulfur compounds and hydrogen cyanide, which is a nitrogen compound, have been removed by the sulfur compound removal means by circulating the gasification gas at a gas temperature below the dew point. A gas purification system comprising:

3. 3. The gas purification system according to claim 2, and an ammonia removal means for removing ammonia by washing the gasification gas from which heavy metals have been removed by the heavy metal removal means. A gas purification system comprising:

4. 4. The gas purification system according to claim 3, and a dehumidifying means for dehumidifying the gasification gas whose temperature has been reduced to a temperature below the dew point after the sulfur compounds and hydrogen cyanide, which is a nitrogen compound, have been removed by the sulfur compound removing means. A gas purification system comprising:

5. 2. The gas purification system according to claim 1, The gasification gas from which heavy metals have been removed by the heavy metal removal means is branched into two routes and distributed to the ammonia removal means and an external utilization means. A gas purification system comprising:

6. The gas purification system according to claim 1 or 3, The ammonium ions (NH ４ ＋ ) into ammonia or ammonium salt, or ammonia and ammonium salt, and recovering the ammonia or ammonium salt. A gas purification system comprising:

7. The gas purification system according to any one of claims 1 to 5, The halide removed by the halide removing means is containing at least one of hydrogen chloride, hydrogen fluoride, and hydrogen bromide; The halide removal means comprises: a first removal means for roughly removing halogens using an absorbent containing calcium in an atmosphere at a first temperature; and a second removal means for precisely removing halogens using an absorbent containing sodium in an atmosphere at a second temperature different from the first temperature. A gas purification system comprising:

8. The gas purification system according to any one of claims 1 to 5, The impurities removed by the sulfur compound removing means are: The sulfur compound includes at least one of hydrogen sulfide and carbonyl sulfide, and hydrogen cyanide, which is a nitrogen compound; The sulfur compound removing means is It is an absorbent containing zinc A gas purification system comprising:

9. The gas purification system according to any one of claims 1 to 5, the heavy metals removed by the heavy metal removal means include at least one of hydrogen selenide and arsenic hydride, and metallic mercury vapor; The heavy metal removal means is The system has a first treatment device that uses activated carbon to remove selenium and arsenic, and a second treatment device that uses a copper-based absorbent that mainly uses copper to absorb mercury, or impregnated activated carbon that removes mercury by adsorbing salts produced by a chemical reaction with mercury. A gas purification system comprising:

10. The gas purification system according to any one of claims 1 to 5, a gasification furnace for generating a gasification gas to be sent to the halide removal means; At least carbonaceous waste is input into the gasification furnace as a raw material, In the gasification furnace, O 2 , H 2 O, CO 2 A part or all of 2 and CO-based synthesis gas is produced. A gas purification system comprising:

11. The gas purification system according to claim 1 or any one of claims 3 to 5, The gasification gas from which ammonia has been removed by the ammonia removal means is It is used as a means of synthesizing chemical products and generating electricity, and also as a means of producing valuable materials. The means for generating electricity and producing valuable resources includes: a distribution means for distributing the gasification gas from which impurities have been removed into two paths; a chemical synthesis means for synthesizing a chemical product using the gasification gas in one of the paths allocated by the allocation means; a power generation means for generating electricity using the gasification gas in the other path allocated by the allocation means as fuel; A gas purification system comprising:

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