KR20220157671A - Ultra-clean acid gas separation system including absorption and adsorption processes - Google Patents

Abstract

The present invention provides an absorption tower for absorbing hydrogen sulfide, an acid gas in biogas, using an iron chelate absorbent, and an ultra-clean hydrogen sulfide separation system for highly separating the same. According to the hydrogen sulfide separation system according to an embodiment of the present invention, the hydrogen sulfide removal rate can be significantly increased by using an ultra-clean acid gas separation system including a hybrid process in which absorption and adsorption are linked. The ultra-clean acid gas separation system using an iron chelate absorbent maximizes the removal of hydrogen sulfide, an acid gas in biogas, to improve the efficiency of a clean fuel conversion process of biogas, and can secure advantages such as high efficiency, selective removal, and low operating costs. The ultra-clean acid gas separation system comprises an absorption tower, a regeneration tower, and an adsorption tower.

Description

Ultra-clean acid gas separation system including absorption and adsorption process

The present invention relates to acid gas separation, and more specifically, to an ultra-clean hydrogen sulfide separation system and separation method for highly separating hydrogen sulfide, an acid gas in biogas, using an iron chelate absorbent.

Fossil fuel, which is currently the most used energy by mankind, has limited reserves and causes global warming due to the emission of greenhouse gases such as carbon monoxide, carbon dioxide, sulfur and nitrogen oxides when burned. Therefore, research on clean energy sources that can replace fossil fuels is being actively conducted, and among them, biogas using organic waste resources is attracting attention.

Fischer-Tropsh process and gas after producing synthetic gas H ₂ and CO gas through a gasification reaction that reacts biogas with oxygen and steam under high-temperature and high-pressure conditions to convert biogas into high value-added products such as synthetic petroleum, electricity, and methane. It is converted by injecting it into various subsequent processes such as engines. However, biogas using organic waste resources contains impurities (H ₂ S, NH ₃ , H ₂ O), among which hydrogen sulfide is a Ni material catalyst used in the reforming process and Fe, Co used in the FT process. It causes poisoning and performance degradation by H ₂ S of the material catalyst. Therefore, in order to prevent poisoning and performance degradation of the reforming process and the FT process catalyst by hydrogen sulfide, the H ₂ S concentration must be maintained at a level of 10 ppb or less, and the development of a high-level purification process for hydrogen sulfide in biogas is essential.

Currently, in general, the process of removing hydrogen sulfide is a method using a solid adsorbent using zeolite, iron oxide powder, impregnated activated carbon, etc., a cloud process, an amine absorption process, an ammonia absorption process, an alkali salt absorption process, a process using microorganisms and enzymes, It can be classified as a liquid phase catalytic oxidation-reduction method. However, existing processes have disadvantages such as large-sized equipment, reduced adsorption and absorption capacity, and long removal time, and it is difficult to remove hydrogen sulfide in biogas below 10 ppb.

Korean Patent Publication No. 2011-0120759 relates to a hydrogen sulfide absorbent, and discloses a hydrogen sulfide absorbent using hexamethylenediamine, diethylenetriamine, etc. as a reaction activator for tertiary alkanolamine. However, this is an amine-based absorbent used as a conventional acid gas absorbent, and has problems such as deterioration of the absorbent and corrosion of the device. Therefore, there is a need for a biogas purification method that can be easily installed with a small-scale device and can maximize the removal of hydrogen sulfide.

In addition, conventional biogas purification has a problem of only removing 1 ppm or more of hydrogen sulfide. Therefore, it is possible to remove up to 10 ppb using the absorption and adsorption hybrid process, which can prevent catalyst poisoning by hydrogen sulfide in the subsequent catalyst process, so there is a need to secure production technology for high value-added clean fuels such as liquid fuel and hydrogen using biogas. do.

Accordingly, the present invention provides a biogas purification system for highly purifying acidic gas in biogas, particularly hydrogen sulfide, using an iron chelate absorbent to turn biogas into liquid fuel, and including a hybrid process in which absorption and adsorption are linked. The purpose is to increase the hydrogen sulfide removal rate to 99.9% or more by using an ultra-clean acid gas separation system.

However, the technical problem to be achieved by the present invention is not limited to the above-mentioned technical problem, and other technical problems not mentioned are clearly understood by those skilled in the art from the description below. It could be.

As a technical means for achieving the above-described technical problem, one aspect of the present invention,

An absorption tower in which an iron chelate absorbent absorbs hydrogen sulfide when biogas containing hydrogen sulfide is injected; a regeneration tower in which an iron chelate absorbent solution absorbing hydrogen sulfide discharged from the bottom of the absorption tower is injected and the absorbent is regenerated by supplying oxygen; and an adsorption tower for removing impurities from the process gas from which hydrogen sulfide has been removed in the absorption tower, wherein the iron chelate absorbent is Fe-EDTA aqueous solution,

The ratio of iron (FE) to EDTA of the iron chelate absorbent is 0.2 to 0.6: 1, and the absorption tower has a rate ratio of 100 to 500 between the absorbent and the gas (L / G, cc / L, Liquid flow rate / gas flow rate), and provides an ultra-clean acid gas separation system.

The iron chelate absorbent may be prepared by mixing an Fe solution after mixing a basic solution and EDTA.

The pH of the iron chelate absorbent may be 8 to 10.

The concentration of the iron chelate absorbent may be 0.05 to 0.09 mol/L.

The pressure difference between the inlet and outlet of the absorption tower may be 0.3 mmH ₂ O to 0.7 mmH ₂ O.

The packing material in the column may be filled by sequentially alternating random packing and structured packing.

A specific surface area of the randomly packed packing in the column may be 100 m ² /m ³ or less, and a specific surface area of the structured packed packing may be 500 m ² /m ³ or more.

The absorption tower may include a spray nozzle for spraying the iron chelate absorbent, and the spray nozzle may have a multi-jet nozzle type.

The absorption tower may include the dispersion plate, and the dispersion plate may have porous pores.

Another aspect of the present invention is,

As a hybrid ultra-clean acid gas separation method in which absorption and adsorption are linked, injecting biogas containing hydrogen sulfide into an absorption tower: absorbing hydrogen sulfide in the biogas with an iron chelate absorbent; a regeneration step of injecting an iron chelate absorbent solution that has absorbed hydrogen sulfide discharged in the absorption step and regenerating the absorbent by supplying oxygen; and an adsorption step of removing impurities from the treated gas from which hydrogen sulfide has been removed in the absorption tower, wherein the iron chelate absorbent is an Fe-EDTA aqueous solution, and the iron chelate absorbent has a ratio of iron (FE) to EDTA of 0.2 to 0.2 to EDTA. 0.6: 1, and the absorption process is a hybrid superclean acid in which absorption and adsorption are linked, in which the absorbent and gas are injected at a rate ratio of 100 to 500 (L / G, cc / L, Liquid flow rate / gas flow rate) A gas separation method is provided.

It may further include a reforming step and F-T (Fisher-Tropsch) reaction step capable of reforming carbon dioxide and methane discharged from the adsorption step and producing fuel.

The iron chelate absorbent may be prepared by mixing an Fe solution after mixing a basic solution and EDTA.

The pH of the iron chelate absorbent may be 8 to 10.

The iron chelate absorbent may have a concentration of 0.05 mol/L to 0.09 mol/L.

According to an embodiment of the present invention, the hydrogen sulfide removal rate can be increased to 99.9% or more by using an ultra-clean acid gas separation system including a hybrid process in which absorption and adsorption are linked.

In addition, the ultra-clean acid gas separation system using the iron chelate absorbent of the present invention maximizes the removal of hydrogen sulfide, which is an acid gas in biogas, to improve the efficiency of the clean fuel conversion process of biogas, and provides high efficiency, selective removal, low operating cost, etc. advantages can be obtained.

The effects of the present invention are not limited to the above effects, and should be understood to include all effects that can be inferred from the detailed description of the present invention or the configuration of the invention described in the claims.

1 is a diagram showing PFD and P&ID related to a biogas purification process.
2 is a diagram showing the results of a test run test for hydrogen sulfide separation using an absorption tower.
3 is a view showing a channeling phenomenon in an absorption tower column.
4 is a view showing the results of a test run for hydrogen sulfide separation using an absorption tower in a steady state.
5 is a photograph showing a supplemented biogas purification mini-pilot process.
6 is a view showing the results of a blank run test using a mixed gas.
7 is a view showing the hydrogen sulfide removal efficiency according to the feed gas change.
8 is a graph showing the hydrogen sulfide removal efficiency according to the pH change of the absorbent.
9 is a graph showing hydrogen sulfide removal efficiency according to feed gas change.
10 is a table comparing the performance of a hydrogen sulfide absorption process compared to conventional ones.
11 is a photograph and a picture showing a pressure drop measuring device in an absorption tower and its experimental results.
12 is a diagram showing a mini-pilot hybrid process experiment apparatus.
13 is a graph showing the results of hydrogen sulfide separation experiments using a hybrid process.

Hereinafter, the present invention will be described in more detail. However, the present invention can be implemented in many different forms, and the present invention is not limited by the embodiments described herein, and the present invention is only defined by the claims to be described later.

In addition, terms used in the present invention are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In the entire specification of the present invention, 'include' a certain element means that other elements may be further included without excluding other elements unless otherwise stated.

In the present specification, an absorption tower may mean a device that contacts a gas with a liquid or suspension for the purpose of concentrating or removing a specific component in the gas, and a packing material is an exhaust gas treatment facility used in various industrial processes. It may refer to a structure filled in a tower for absorption. In addition, the term chelate may refer to a complex ion formed by a coordination bond between one ligand and a metal ion at two or more sites.

Hereinafter, the present invention will be described in detail.

The first aspect of the present application is,

An absorption tower in which an iron chelate absorbent absorbs hydrogen sulfide when biogas containing hydrogen sulfide is injected; a regeneration tower in which an iron chelate absorbent solution absorbing hydrogen sulfide discharged from the bottom of the absorption tower is injected and the absorbent is regenerated by supplying oxygen; And an adsorption tower for removing impurities from the processed gas from which hydrogen sulfide has been removed in the absorption tower. The ratio of FE) is 0.2 to 0.6: 1, and the absorbent and gas are injected at a rate ratio of 100 to 500 (L / G, cc / L, Liquid flow rate / gas flow rate), ultra-clean acid gas Separation system is provided.

Hereinafter, the absorption tower for absorbing hydrogen sulfide according to the first aspect of the present application will be described in detail.

The absorption tower of the present invention absorbs hydrogen sulfide in the supplied biogas, and can be absorbed using a liquid absorbent. In the absorption tower, hydrogen sulfide contained in the injected biogas is chemically absorbed using an iron chelate absorbent, and processed gas containing methane and carbon dioxide can be discharged to the outside. In the absorption tower, it is possible to absorb hydrogen sulfide in the biogas supplied to the bottom while spraying from the top of the absorption tower. The iron chelate absorbent of the present invention can absorb hydrogen sulfide in biogas supplied to the absorption tower through chemical reactions as shown in Formulas (1) to (4) below. When hydrogen sulfide is first physically absorbed while being dissociated into the absorbent solution, it is oxidized by the iron chelate present in the absorbent and forms solid sulfur as shown in Formula (4). In one embodiment of the present invention, the absorption tower can be driven at 5 ° C to 90 ° C, preferably at a temperature range of 25 ° C to 45 ° C. When the operating temperature is 5° C. or less, the absorption capacity is similar to the freezing point of the absorbent and may decrease the absorption capacity. At 90° C. or higher, it is difficult to perform the absorption and regeneration process due to evaporation of the absorption solution.

H ₂ S(g) + H ₂ O ↔ H ₂ S(aq) (1)

H ₂ S(aq) ↔ H ⁺ + HS ^- (2)

HS ^- ↔ H ⁺ + S ^2- (3)

S ^2- + 2Fe ³⁺ ↔ S0 + 2Fe ²⁺ (4)

chelating absorbent

According to an embodiment of the present invention, the iron chelate absorbent may preferably be Fe-EDTA aqueous solution. The ratio of iron (FE) to EDTA may be 0.2 to 0.6:1, preferably 0.25 to 0.4:1, and more preferably 0.33:1.

The iron chelate absorbent may be prepared by mixing a basic solution and EDTA and then mixing an Fe solution, preferably by mixing EDTA with NaOH to adjust the pH, and then mixing the Fe solution, more preferably The pH may be adjusted to about 12 by adding 4M NaOH to EDTA, and then adjusted to pH 8 or higher by slowly adding Fe solution. Precipitation can be prevented through the preparation method of the iron chelate absorbent.

The pH of the iron chelate absorbent may be 8 to 10, preferably 8.5 to 9.5, and most preferably 9.88.

The iron chelate absorbent may have a concentration of 0.05 mol/L to 0.09 mol/L, preferably 0.06 mol/L to 0.08 mol/L, and more preferably 0.07 mol/L. If the concentration is 0.05 mol/L, the amount of molecules capable of absorbing hydrogen sulfide is small, so that smooth absorption cannot be performed. If the concentration is 0.09 mol/L or more, hydrogen sulfide is sufficiently absorbed and there may be an amount of remaining molecules, which is uneconomical, and excessive Solid sulfur may be produced which may interfere with the continuous process.

The hydrogen sulfide absorbed by the iron chelate becomes solid sulfur, and at the same time the iron chelate is converted from trivalent to divalent. The iron chelate absorbent converted to divalent must be regenerated to trivalent for reuse. In the present invention, the reduced iron chelate absorbent solution may be supplied to a regeneration tower to be oxidized and regenerated. The absorbent solution supplied from the absorption tower contains solid sulfur, which is filtered while being supplied to the regeneration tower. The filtration may be performed in a filter located at the outer bottom of the absorption tower, and preferably may be performed in a filter for removing solid sulfur in an intermediate line moving between the absorption tower and the regeneration tower. The filter removes solid sulfur and uses a filter capable of passing only the absorbent, and by installing two or more filter mounting devices, it is possible to facilitate the flow of the absorbent while sequentially replacing them when solid sulfur accumulates.

Regeneration of the iron chelate absorbent is performed according to the reactions of formulas (5) and (6) below. The absorbent solution injected into the regeneration tower is regenerated by oxygen supplied to the regeneration tower. Oxygen in the regeneration tower is absorbed into the absorbent solution, and the absorbed oxygen reacts with the iron chelate. At this time, the divalent iron chelate is oxidized to trivalent and regenerated. the regeneration tower

In , the regenerated absorbent is re-supplied to the absorption tower to re-absorb hydrogen sulfide, enabling a continuous process.

O₂ (g) + H₂O ↔

O₂ (aq) (5)

O ₂ (g) + H ₂ O ↔

O ₂ (aq) (5)

O₂ (aq) + 2Fe²⁺ ↔ 2Fe³⁺ + 2OH (6)

O ₂ (aq) + 2Fe ²⁺ ↔ 2Fe ³⁺ + 2OH (6)

Hybrid process with adsorption

Even when the absorption process using the iron chelate absorbent is used as described above, the hydrogen sulfide removal rate can reach 99%. The hydrogen sulfide removal rate can be increased to 99.9% or more through a hybrid process linked to adsorption.

pressure drop

In the absorption process, the high pressure drop in the tower that occurs when gas and liquid contact causes problems such as flooding. Therefore, the low pressure drop facilitates gas-liquid flow and increases the separation efficiency of the process. The pressure difference between the inlet and outlet of the absorption tower of the present invention may be 0.3 mmH ₂ O to 0.7 mmH ₂ O, preferably 0.4 mmH ₂ O to 0.6 mmH ₂ O, more preferably 0.5 mmH ₂ O. In the experimental example of the present application, the pressure drop at 5 L/min is very low as 0.5 mmH ₂ O (4.8*10-5 atm), showing no problem during operation.

packing

Structured packing may refer to various materials specially designed for use in absorption towers and chemical reactors. Structured packing typically consists of thin corrugated metal plates or gauze arranged to pass a fluid through a complex path through the column, which can create a large surface area for contact between different phases. Structured packings can have inclined flow channels while providing a relatively high surface area while providing very low resistance to gas flow. Therefore, by having a high surface area, liquid diffusion can be maximized, and the open area is wider, so that a large capacity and a small pressure drop can occur.

On the other hand, random packing may refer to a method of packing a column with randomly packed filtration materials in order to optimize the surface area on which reactants can interact and to minimize the complexity of the column configuration.

According to an embodiment of the present invention, structured packing can be partially installed in the random packing in the absorption tower column. In general, the specific surface area of fillers that influence gas-liquid contact is 100 m ² /m ³ or less in the case of randomly packed fillers and 500 m ² /m ³ or more in the case of structured packed fillers, which can increase the separation efficiency. Therefore, it is possible to prevent channeling and increase the liquid wetting effect by sequentially placing the column packing material in random and structured packing.

In other device design, improvement of control system for continuous operation between absorption tower and regeneration tower, installation of dehydrator before adsorption tower to circulate condensed water to regeneration tower, process for removing solid sulfur for continuous operation of absorption and regeneration Efficiency can be improved by improving and supplementing column internals, etc.

Spray Nozzles and Dispersion Plates

The spray nozzle may be in the form of a multi-jet nozzle. The injection nozzle of the sap can be changed to a multi-jet nozzle type so that it can be evenly distributed at the top of the column.

In addition, the dispersion plate may have porous pores. The dispersion plate was designed, manufactured, and mounted three-dimensionally to facilitate redispersion of the liquid sprayed from the nozzle while having porous pores in order to disperse the liquid sprayed from the nozzle well before being injected into the column. A dispersion plate can be mounted on each stage of the column to facilitate redistribution of the liquid.

Adsorption tower, reforming tower and F-T reactor

In the absorption tower of the present invention, the biogas from which hydrogen sulfide is removed by the iron chelate absorbent is discharged to the top of the absorption tower, and it can be supplied to the adsorption tower filled with metal oxide. The adsorption tower can treat small amounts of impurities that have not been treated in the absorption tower, and can prevent catalyst poison when used in gas reforming and synthesis processes through advanced purification of biogas. In one embodiment, the gas passing through the adsorption tower includes methane and carbon dioxide, which can produce clean fuel using a reforming process and an F-T process.

The reforming process unit of the present invention can produce syngas using methane and carbon dioxide. For example, synthesis gas can be produced by steam reforming of methane (SRM) and carbon dioxide reforming of methane (CDR). The steam reforming method may generate carbon monoxide and hydrogen by reacting methane and steam under conditions of 700-850 ° C, 1-40 atm, space velocity 3,000-6,000 ^{hr -1} (CH ₄ + H ₂ O → CO + 3H ₂ , ΔH ^o = 206 kJ/mol). The carbon dioxide reforming method of methane may generate carbon monoxide and hydrogen by reacting methane and carbon dioxide at 700-850 ° C. and 1-10 atm (CH ₄ + CO ₂ → 2CO + 2H ₂ , △H ^o = 247 kJ/ mol). The produced syngas can be used by itself or can produce high value-added compounds through the FT (Fisher-Tropsch) reaction process unit. The FT process is a technology for producing synthetic fuel from syngas and consists of the following four main reactions at a reaction temperature of 200-350 ° C. and a pressure of 10-30 atmospheres under an iron or cobalt catalyst. Methane and carbon dioxide generated from the biogas of the present invention can prevent degradation of the catalyst used in the FT reaction by highly purifying hydrogen sulfide in the gas.

(a) Chain growth in FT synthesis

CO + 2H ₂ → -CH ^2- + H ₂ O △H(227℃) = -165kJ/mol

(b) Methanation

CO + 3H ₂ → CH ₄ + H ₂ O △H(227℃) = -215kJ/mol

(c) Water gas shift reaction

CO + H ₂ O ↔ CO ₂ + H ₂ △H(227℃) = -40kJ/mol

(d) Boudouard reaction

2CO ↔ C + CO ₂ △H(227℃) = -134kJ/mol

The second aspect of the present application is,

As a hybrid ultra-clean acid gas separation method in which absorption and adsorption are linked, injecting biogas containing hydrogen sulfide into an absorption tower: absorbing hydrogen sulfide in the biogas with an iron chelate absorbent; a regeneration step of injecting an iron chelate absorbent solution that has absorbed hydrogen sulfide discharged in the absorption step and regenerating the absorbent by supplying oxygen; and an adsorption step of removing impurities from the treated gas from which hydrogen sulfide has been removed in the absorption tower, wherein the iron chelate absorbent is an Fe-EDTA aqueous solution, and the iron chelate absorbent has a ratio of iron (FE) to EDTA of 0.2 to 0.2 to EDTA. 0.6: 1, and the absorption process is a hybrid superclean acid in which absorption and adsorption are linked, in which the absorbent and gas are injected at a rate ratio of 100 to 500 (L / G, cc / L, Liquid flow rate / gas flow rate) A gas separation method is provided.

Although detailed descriptions of portions overlapping with those of the first aspect of the present application have been omitted, the contents described for the first aspect of the present application can be equally applied even if the description is omitted from the second aspect.

The absorption tower is equipped with a filter at the bottom so that solid sulfur produced by oxidation of hydrogen sulfide by the iron chelate absorbent is filtered, and the liquid absorbent is injected into the regeneration tower. In the regeneration tower, oxygen is injected to oxidize the absorbent and reinjected into the absorption tower, and a continuous process is possible.

In one embodiment of the present application, it may further include a reforming step and F-T (Fisher-Tropsch) reaction step capable of reforming carbon dioxide and methane discharged from the adsorption step and producing fuel.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein.

Example 1: Preparation of an iron chelate absorbent

EDTA, a chelating compound, contains 6 unshared electron pairs (2 nitrogen groups, 4 carboxyl groups), and these unshared electron pairs have an electron donor to form Fe-EDTA, a complex compound with iron solution, to selectively release hydrogen sulfide. can be separated and removed

An improved iron chelate absorbent was prepared to separate hydrogen sulfide. The preparation was made into a liquid solution by mixing EDTA and Fe. In addition, the pH of the solution was adjusted to change the properties of the prepared iron chelate absorbent. In the manufacturing method, after injecting a certain amount of EDTA-2Na into DI water, it is diluted to prepare a 900ml solution.

To adjust the pH of the prepared solution, a 4M NaOH solution was mixed with the EDTA solution (pH 3-5) to make the pH 6 or more (about pH 12), and the pH was adjusted to 8 or more by slowly adding Fe solution. In addition, in order to prepare a liquid Fe solution, an Fe solution was prepared in DI water, and the mixing ratio of Fe and EDTA was adjusted to 0.33: 1 to prepare a large amount. Acidification could be prevented by maintaining the Fe-EDTA concentration as low as 0.07 mol/L.

Precipitation can be prevented by mixing NaOH with EDTA, which is a chelating material, to make the EDTA solution into an alkaline solution, thereby maintaining an alkaline state even when the Fe solution is mixed. In addition, as the EDTA solution maintains its alkaline properties, it has the property of forming a complex compound between Fe and EDTA better when mixing the Fe solution, so it was shown that the hydrogen sulfide removal efficiency is high even at low concentrations.

Experimental Example 1: Continuous hydrogen sulfide absorption process using an iron chelate absorbent

1. Mini-pilot scale device design

A mini-pilot device design for ultra-clean biogas purification was performed. In order to secure basic data for process design, heat and mass balance calculations were performed, followed by PFD (Process Flow Diagram) and P&ID (Piping & Instrument Diagram). The device was designed for biogas production using 50kg/day organic waste resources at the time of demonstration, and the production rate was 3.47 L/min, so it was designed based on this.

The PFD of FIG. 1A consists of an iron-chelate absorption process, a cooling process for water removal, and an adsorption process. In the absorption process, it consists of a gas injection unit, a continuous absorption and regeneration process, and a control system. In the gas injection unit, an injection flow rate measuring device and a control device, which are actually organic waste-derived gases, are provided. In addition, a cylinder was installed to inject oxygen or air to supply gas to the regeneration tower. The reactor for the continuous absorption and regeneration process had a diameter of 5 cm and a tower height of 1 m. In addition, the tower is composed of two stages so that the length of the tower can be freely adjusted according to changes in operating conditions during process operation. Plastic packing was injected into the tower. In addition, distributors were installed at the top and bottom of the tower to ensure good dispersion during injection of liquid and gas. A certain amount of liquid storage tank was placed at the bottom of the tower to facilitate the control of the flow rate level of the liquid in the absorption tower and the regeneration tower. In addition, a metering pump was installed between the absorption tower and the regeneration tower so that the iron chelate absorbent could be constantly circulated. A post-cooling device and a fixed bed adsorption tower for low-concentration hydrogen sulfide removal were installed.

In the P&ID of FIG. 1B, instrumentation is attached to each PFD-based device. This device is an actual process demonstration development for use as a commercial device in the future, and various control devices are attached to the device in consideration of various situations that may occur in the commercial device. In the refinery and auxiliary equipment, the process was composed of equipment capable of actual automatic operation, such as the size of each equipment and line size, along with all the controllable instrumentation. In addition, the control system program was produced and modified so that each device can be linked and operated well, so that actual operation is possible.

2. Comparative Example 1: Mini-pilot scale device fabrication and commissioning

A test run experiment was conducted for the iron chelate absorption process using the fabricated device using the designed data. As operating conditions, absorbent concentration 0.2M, used absorbent 1 L, absorbent flow rate 460 L/min, simulated gas concentration H ₂ S 100ppm (N ₂ balance), gas flow rate 0.5 to 3.5 L/min, regeneration gas Air, regeneration gas flow rate It was performed at 1-2 L/min.

As a result of the hydrogen sulfide separation test run experiment using the absorption process, as shown in FIG. 2, the efficiency of 20% at 3.5 L/min and 30-60% at 0.5 L/min of the injection gas is shown. As shown in the column phenomenon of FIG. 3, when gas and liquid contact in the absorption tower, sufficient liquid wetting is not achieved due to the channeling phenomenon due to the wall effect of the liquid, resulting in reduced efficiency. because it causes

In addition, even in the results of the hydrogen sulfide separation test run using the absorption tower in a steady state, as shown in FIG. In addition, since the efficiency increases as the air injection flow rate increases during regeneration, optimal absorption and regeneration operating conditions are required. In addition, even in a normal state, the separation efficiency of hydrogen sulfide is low, and improvement and supplementation of the device are required.

3. Example 2: Complementary Mini-Pilot Scale Device Fabrication

As described above, in order to compensate for the low hydrogen sulfide separation efficiency by channeling of the column according to the results of the test run experiment, as shown in FIG. 5, a biogas purification mini-pilot process was supplemented.

To this end, a spray nozzle, a distributor, and an internal inside the column were supplemented in order to widen the gas-liquid contact area of the column. The injection nozzle of the absorption liquid was changed to a multi-jet nozzle type so that it could be evenly distributed over the top of the column. In addition, the dispersion plate was designed, manufactured, and mounted three-dimensionally to facilitate redispersion of the liquid sprayed from the nozzle while having porous pores so that the liquid sprayed from the nozzle could be well dispersed before being injected into the column. A dispersion plate was installed at each stage of the column to facilitate redistribution of the liquid.

Also, in the column, random packing was partially loaded with structured packing. In general, the specific surface area that influences gas-liquid contact is 100 m ² /m ³ for random packing and 500 m ² /m ³ for structured packing, which can increase the separation efficiency. Therefore, random packing and structured packing were sequentially placed as column packing materials to prevent channeling and increase the liquid wetting effect.

In other device designs, a control system improvement for continuous operation between the absorption tower and the regeneration tower, a dehydrator was installed before the adsorption tower, and a process for circulating condensed moisture to the regeneration tower and removing solid sulfur for continuous operation of absorption and regeneration. We tried to improve the efficiency by supplementing the column internal through improvement and supplementary experiments.

(1) Preliminary experiments on mini-pilot scale devices

Before field demonstration, a preliminary operation experiment using two types of simulated gas 1 (H ₂ S 100 ppm, N ₂ bal.) and simulated gas 2 (H ₂ S 100 ppm, CO ₂ 30%, CH ₄ 70%) was performed. As an analysis device, a GC-PFPD (Pulsed Frame Photometric Detector) capable of analyzing hydrogen sulfide was used. As a result of the analysis, as shown in FIG. 6, it was found that the analysis device was reliable by obtaining an analysis result similar to the manufactured mock gas.

(2) Hydrogen sulfide separation from organic waste resources Mini-pilot scale process operation by operating conditions

1) Driving results using a mini-pilot scale device (H ₂ S/N ₂ )

H ₂ S separation experiments using the improved absorption process were performed. as operating conditions

Feed gas: H ₂ S 100ppm balance N ₂ , Feed gas flow rate: 1∼4 L/min, Absorbent concentration: 0.07 mol/L, Absorbent pH: 9.77, Absorbent volume: 1.3 L, Absorbent flow rate: 460 mL/min , Oxidative gas: Air, Oxidative gas flow rate: 2 L / min. The separation efficiency definition is as follows.

As can be seen in Figure 7, the hydrogen sulfide removal efficiency according to the change in feed gas is L / G [(Liquid flow rate, mL / min) / (Gas flow rate, L / min)] in the entire operating range from 460 to 115 to 99 % or higher removal efficiency (H ₂ S: <1 ppm) is shown. At this time, it was shown that there was no pH change during hydrogen sulfide absorption and regeneration (pH: 9.77). It can be seen that the regeneration of the absorbent by oxidation is excellent.

In FIG. 8, the hydrogen sulfide removal efficiency according to pH change is 95 to 99% (operating area: L / G 460 to 131) at pH 7 or less of the absorbent, which is 99% or less. However, at an absorbent pH of 9 or higher, the separation efficiency is 99% (operating area: L/G 460 to 131).

It can be seen that the improved absorption process shows high efficiency, and pH control of the absorbent has a great effect on the separation efficiency.

2) Results of operation using a mini-pilot scale device (H ₂ S/CO ₂ /CH ₄ )

H ₂ S separation experiment using absorption process Feed gas: H ₂ S 100ppm CO ₂ 30%, CH ₄ 70%, Feed gas flow rate: 1∼3.5 L/min, Absorbent concentration: 0.07 mol/L, Absorbent pH: 9.77, Absorbent volume: 1.3 L, Absorbent flow rate: 460 mL/min, Oxidative gas: Air, Oxidative gas flow rate: 2 L/min.

In FIG. 9, the hydrogen sulfide removal efficiency according to the change in feed gas shows a removal efficiency of 99% or more (H ₂ S: <1ppm) in the operating range L / G of 460 to 131. At this time, the pH change is slightly lowered during continuous hydrogen sulfide absorption and regeneration experiments, but the separation efficiency is constant.

Based on the previously published literature, hydrogen sulfide removal efficiency according to operating conditions is compared and shown in FIG. 10. Comparison was made according to absorbent concentration, L/G, and biogas components. As a result of process operation using the developed absorbent, the developed process shows a removal efficiency of 99% or more (H ₂ S: <1ppm) at L/G 460 or less, which is superior to the existing ones.

Experimental Example 2: Pressure drop test results of mini-pilot scale absorption process

In the absorption process, the high pressure drop in the tower that occurs when gas and liquid contact causes problems such as flooding. Therefore, the low pressure drop facilitates gas-liquid flow and increases the separation efficiency of the process. In this experiment, as shown in FIG. 11, the pressure drop at 5 L/min is 0.5 mmH ₂ O (4.8 x 10 ^-5 atm), which is very low, showing no problem during operation.

Experimental Example 3: Operation result of absorption and adsorption linked process using mini-pilot scale device (H ₂ S/CO ₂ /CH ₄ )

A hydrogen sulfide separation experiment using a hybrid process in which absorption and adsorption are coupled using a mini-pilot scale device shown in FIG. 12 was performed. In the experiment, the concentration of hydrogen sulfide was set at 100 to 300 ppm.

In the H ₂ S separation experiment using the hybrid process, the operating conditions of the absorption process were Feed gas: H ₂ S 100ppm/300ppm, CO ₂ 30%, CH ₄ 70%, Feed gas flow rate: 3.5 L/min, Absorbent concentration: 0.07 mol/L, Absorbent pH: 9.88, Absorbent volume: 1.3 L, Absorbent flow rate: 460 mL/min, Oxidative gas: Air, Oxidative gas flow rate: 2 L/min. In addition, after the absorption process, side steam of the treated gas was injected into the adsorption process to conduct hydrogen sulfide treatment experiments. At this time, the operating conditions were Feed gas flow rate: 700 cc/min, Adsorbent amount: 10gr (Bulk density: 0.578g/cm ³ ) was performed at GHSV 2,400 hr ^-1 .

In the hydrogen sulfide separation experiment using the mini-pilot hybrid process, the H ₂ S concentration was continuously tested at 100 ppm and 300 ppm, respectively, for 240 min. As shown in the experimental results of FIG. 13, the removal rate after operation at concentrations of 100 ppm and 300 ppm of hydrogen sulfide is 99.9% or more. In addition, the adsorption experiment was performed at a space time of 20 to 50 hr ^-1 , which is the operating condition of a general commercial adsorption process, whereas in this experiment, despite the accelerated experiment, high removal efficiency was shown.

In order to understand the accurate removal performance of the results of this experiment, after the end of the 240min experiment, a 3L Tedlar bag was used to collect the processed gas after the absorption and adsorption processes, and then a GC with a sulfur analysis detector was used to perform additional analysis was performed.

/

(ppb), 흡착 공정 후에는 각각 4.5 및 0.0

/

(ppb)을 나타내었다.As a result of the analysis, after the absorption process at 100ppm and 300ppm of H ₂ S concentration in the feed gas, respectively, 306 and 305

/

(ppb), after the adsorption process, 4.5 and 0.0 respectively

/

(ppb).

Claims (14)

An absorption tower in which an iron chelate absorbent absorbs hydrogen sulfide when biogas containing hydrogen sulfide is injected;
a regeneration tower in which an iron chelate absorbent solution absorbing hydrogen sulfide discharged from the bottom of the absorption tower is injected and the absorbent is regenerated by supplying oxygen; and
An ultra-clean acid gas separation system comprising an adsorption tower for removing impurities from the processed gas from which hydrogen sulfide has been removed in the absorption tower,
The iron chelate absorbent is an aqueous solution of Fe-EDTA,
The ratio of iron (FE) to EDTA of the iron chelate absorbent is 0.2 to 0.6: 1,
The absorption tower is an ultra-clean acid gas separation system in which the absorbent and the gas are injected at a rate ratio (L / G, cc / L, Liquid flow rate / gas flow rate) of 100 to 500.
According to claim 1,
The iron chelate absorbent is prepared by mixing a basic solution and EDTA and then mixing an Fe solution, ultra-clean acid gas separation system.
According to claim 1,
The pH of the iron chelate absorbent is 8 to 10, ultra-clean acid gas separation system.
According to claim 1,
The concentration of the iron chelate absorbent is 0.05 mol / L to 0.09 mol / L, ultra-clean acid gas separation system.
According to claim 1,
The pressure difference between the inlet and outlet of the absorption tower is 0.3 mmH ₂ O to 0.7 mmH ₂ O, ultra-clean acid gas separation system.
According to claim 1,
The packing material in the column is an ultra-clean acid gas separation system in which random packing and structured packing are sequentially crossed and filled.
According to claim 1,
The specific surface area of the randomly packed packing in the column is 100 m ² /m ³ or less,
The structured packing has a specific surface area of 500 m ² / m ³ or more, ultra-clean acid gas separation system.
According to claim 1,
The absorption tower includes a spray nozzle for spraying the iron chelate absorbent,
The spray nozzle is a multi-jet nozzle type, ultra-clean acid gas separation system.
According to claim 1,
The absorption tower includes the dispersion plate,
The dispersion plate has porous pores, ultra-clean acid gas separation system.
As a hybrid ultra-clean acid gas separation method in which absorption and adsorption are linked,
Injecting biogas containing hydrogen sulfide into the absorption tower:
Absorbing hydrogen sulfide in the biogas with an iron chelate absorbent;
a regeneration step of injecting an iron chelate absorbent solution that has absorbed hydrogen sulfide discharged in the absorption step and regenerating the absorbent by supplying oxygen; and
An adsorption step of removing impurities from the processed gas from which hydrogen sulfide is removed in the absorption tower;
The iron chelate absorbent is an aqueous solution of Fe-EDTA,
The ratio of iron (FE) to EDTA of the iron chelate absorbent is 0.2 to 0.6: 1,
The absorption process is a hybrid ultra-clean acid gas separation method in which absorption and adsorption are linked, in which the absorbent and the gas are injected at a rate ratio (L / G, cc / L, Liquid flow rate / gas flow rate) of 100 to 500.
According to claim 10,
A hybrid ultra-clean acid gas separation method in which absorption and adsorption are linked, further comprising a reforming step capable of reforming carbon dioxide and methane discharged in the adsorption step and producing fuel, and a Fisher-Tropsch (FT) reaction step.
According to claim 10,
The iron chelate absorbent is prepared by mixing a basic solution and EDTA and then mixing an Fe solution, a hybrid ultra-clean acid gas separation method in which absorption and adsorption are linked.
According to claim 10,
The pH of the iron chelate absorbent is 8 to 10, a hybrid ultra-clean acid gas separation method in which absorption and adsorption are linked.
According to claim 10,
The iron chelate absorbent has a concentration of 0.05 mol / L to 0.09 mol / L, a hybrid ultra-clean acid gas separation method in which absorption and adsorption are linked.

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