KR20190111479A - Continuous Flue gas Desulfurization System - Google Patents

Abstract

The present invention relates to a desulfurization system for performing a desulfurization process on exhaust gas in a continuous process using a membrane contactor. The exhaust gas desulfurization system for the continuous process of the present invention can further reduce sulfur oxides regarding the gas discharged from the exhaust gas desulfurization facility. The use of a relatively small membrane contactor can also provide feasibility that lowers equipment construction and operation costs.

Description

Continuous Flue Gas Desulfurization System

The present invention relates to a desulfurization system, and more particularly, to a desulfurization system for removing sulfur oxides in exhaust gas in a continuous process using a membrane contactor.

Exhaust gases from factories and power plants contain a variety of pollutants, including ultra-fine dust, sulfur oxides, and carbon dioxide.In particular, combustion of sulfur-containing fuels, such as coal, requires trace amounts of SO ₂ and SO ₃ . Create SOx. Sulfur oxide contained in exhaust gas is not only a main cause of acid rain and smog along with nitrate, but also a major source of ultrafine dust in the atmosphere. Most sulfur oxide treatment facilities use limestone as an absorbent reaction in the wet limestone gypsum process, and produce gypsum as a reaction product and sell it as a raw material for cement or gypsum board. In recent years, however, the inflow of SO ₂ concentration has increased due to the increased use of high sulfur fuel, and the quality of gypsum is also reduced due to deterioration of operating conditions of the desulfurization process. In addition, the problem of desulfurization equipment is caused by the reduction of sulfur oxide removal rate, increasing exhaust gas flow rate, GGH leakage rate, absorption tower pH, oxidizing air flow rate reduction, absorption tower water level imbalance due to clogging part of oxidation air distribution pipe. There are a number of problems such as limestone blinding, absorbent particle size and purity, increased inlet sulfur oxide concentration, and reduced L / G ratio.

With the recent development of carbon capture and storage (CCS) technology for reducing greenhouse gas emissions, the level of carbon dioxide capture technology in the exhaust gas is approaching the commercialization stage, and installation and operation of existing thermal power generation facilities are being attempted. Sulfur oxide in the process for capturing carbon dioxide in the exhaust gas The gas inlet concentration increases as the sulfur content of fossil fuel increases. Sulfur oxides are known to degrade alkanolamines solution used in the wet absorption of CO ₂ , and SO ₂ containing moisture in the CO ₂ inlet gas can cause corrosion of pipes, pumps and other infrastructure. do. In the same sulfur dioxide to give an adverse effect on the CO ₂ capture process, CO ₂ storage process due to the efficiency degradation and contamination of the collected CO ₂ in the process when entering the so CO ₂ inflow of contamination, including the SO ₂ to the collecting step This is strictly regulated. For example, it is common that sulfur oxides should not exceed 10 ppm and the MHI aims to regulate it to 1 ppm or less.

In order to keep the sulfur oxide concentration below 10ppm by increasing the desulfurization efficiency as high as 99.5% in the existing flue gas desulfurization process (FGD) to cope with the inflow conditions of sulfur oxide required by the CO ₂ capture process, In order to greatly increase the size (more than 2 times), to completely refill the filling and internal structure, and to increase the circulation of the absorbent reaction solution, basic equipment or equipment such as a circulation pump should be added or replaced with a large capacity. Therefore, in the case of adding a CO ₂ capture facility in a facility that is already installed and in operation, it is often impossible to drastically modify the existing flue gas desulfurization facility. In such cases, the introduction of additional ultra-clean flue gas desulfurization facilities is inevitable. Therefore, the necessity of ultra-clean desulfurization process is required to supplement the performance of the existing desulfurization process (FGD) and to maintain the operation efficiency and economic efficiency of the carbon dioxide capture and storage process.

Membrane devices are considered to be one of the most energy-saving technologies among various gas separation technologies because no additional energy (latent heat) is needed for the phase change during the separation process. Currently, the membrane process is used in various fields such as oxygen / nitrogen separation in air, refinery process, hydrogen recovery concentration in petrochemical process, separation and removal of carbon dioxide and hydrogen sulfide from natural gas. The membrane process has the advantages that the device components required to install the system are very simple, the operation and control methods are very simple and the scale is easy to scale up. Regarding the separation of sulfur oxides, the membrane device is smaller in size than the existing FGD, is easy to install, and the membrane device can be efficiently used in the free space between the FGD and the stack.

Korean Patent No. 1010727 relates to a system for removing sulfur oxides from combustion exhaust gas and a method thereof, and discloses a method for removing sulfur oxides by chemically reacting sulfur oxides of exhaust gases injected into a reactor using a catalyst. Republic of Korea Patent No. 1672881 relates to an exhaust gas treatment device for improving the SO ₃ removal efficiency, to remove the sulfur oxides by spraying the solution using a wet scrubber.

The exemplary patents have a problem in that a large amount of equipment needs to be added and replaced, and a post-treatment process is also required as the reactants, absorbents, and the like are used. Therefore, there is a need for a desulfurization system that is easier to install with a smaller scale device than conventional FGD.

Korea Patent Publication 1010727 Korean Patent Publication No. 1672881

The present invention has been made in view of the above problems, to provide a desulfurization system for performing a desulfurization process in the exhaust gas in a continuous process.

The present inventors have completed the present invention by finding a desulfurization system that can minimize the emission of sulfur oxides as a secondary desulfurization system using a membrane contactor.

The present invention is a continuous process exhaust gas desulfurization system, the system comprises an exhaust gas supply; Flue gas desulfurization (FGD) for performing primary desulfurization of the exhaust gas supplied from the exhaust gas supply unit; A separator contactor for supplying the primary desulfurized exhaust gas through the flue gas desulfurization apparatus to perform secondary desulfurization; A storage tank storing the sulfur oxide absorbing solution absorbed by the membrane contactor; And a secondary desulfurization absorption solution processing line for supplying the sulfur oxide absorption solution stored in the reservoir to the water or slurry supply unit of the flue gas desulfurization apparatus, wherein the membrane contactor includes a hollow fiber membrane module, and the inner surface or the outer surface of the hollow fiber membrane. On the side there is provided a continuous process exhaust gas desulfurization system in which an alkaline solution is circulated.

The present invention also provides a continuous process exhaust gas desulfurization system, the separator contactor further comprises a pressure reducing pump.

The present invention also provides a continuous process exhaust gas desulfurization system, the system comprising: an exhaust gas supply unit; Flue gas desulfurization (FGD) for performing primary desulfurization of the exhaust gas supplied from the exhaust gas supply unit; A separator contactor for supplying the first desulfurized exhaust gas through the flue gas desulfurization apparatus to perform secondary desulfurization; And a sulfur oxide supply line for injecting sulfur oxides discharged from the separator contactor into FGD, wherein the separator contactor includes an absorption tower and a degassing column including a hollow fiber membrane module, and an inner side or an outer side of the hollow fiber membrane. The alkaline solution is circulated therein, and the primary desulfurized exhaust gas is supplied to the absorption tower so that the sulfur oxides in the exhaust gas are absorbed into the alkali solution, and the alkali solution absorbing the sulfur oxides is supplied to the degassing tower to provide sulfur oxides. It is degassed, and the sulfur oxides discharged from the degassing tower are fed back to the flue gas desulfurization apparatus, to provide a continuous process exhaust gas desulfurization system.

The present invention, the separator is, polypropylene, polyether sulfone, polysulfone, polyethylene imide, polyimide, poly burnsimidazole, polyacrylate, poly-n-butyl methacrylate, polycarbonate, polyether ether Membranes consisting of one or more hydrophobic materials selected from the group consisting of ketones, polyestersulfones, polyvinylidene fluorides, polyvinylpyrrolidones, polyvinylfluorides and polyvinylcarbazoles, or the materials coated on or inside Membrane, a continuous process exhaust gas desulfurization system.

In the present invention, the alkaline solution is KOH, MgO, MgCO ₃ , NaO, NaCO ₃ , NaOH, NaHCO ₃ , CaO, Ca (OH) ₂ , CaCO ₃ and One or more aqueous solutions selected from the group consisting of NH ₃ provide a continuous process exhaust gas desulfurization system.

The present invention also provides a continuous process exhaust gas desulfurization system in which the gas phase and the liquid phase supplied to the hollow fiber membrane module flow in different directions.

In the continuous process exhaust gas desulfurization system of the present invention, while further reducing the sulfur oxides for the gas discharged from the flue gas desulfurization facility, the use of a relatively small membrane contactor can also secure the economics of lowering the equipment construction cost and operating costs.

1 is a schematic diagram of a continuous process exhaust gas desulfurization system in accordance with one embodiment of the present invention.
2 is a schematic diagram of a continuous process exhaust gas desulfurization system including an absorption tower and a degassing column according to one embodiment of the present invention.

Prior to the description of the invention, the terms or words used in the specification and claims described below should not be construed as limiting in their usual or dictionary meanings. Therefore, the embodiments described in the specification and the drawings shown in the drawings are only one of the most preferred embodiments of the present invention and do not represent all of the technical idea of the present invention, various modifications that can be replaced at the time of the present application It should be understood that there may be equivalents and variations.

In one aspect the invention is a desulfurization system comprising a membrane contactor for removing sulfur oxides from exhaust gas, the system comprising: an exhaust gas supply; Flue gas desulfurization (FGD) for performing primary desulfurization of the exhaust gas supplied from the exhaust gas supply unit; A separator contactor for supplying the primary desulfurized exhaust gas through the flue gas desulfurization apparatus to perform secondary desulfurization; A storage tank storing the sulfur oxide absorbing solution absorbed by the membrane contactor; And a sulfur oxide absorption solution supply line for supplying the sulfur oxide absorption solution stored in the reservoir to FGD.

The desulfurization system of the present invention includes a separator contactor fabricated with a hollow fiber membrane as a module and cartridgeized thereto. 1 is a schematic diagram of a continuous process exhaust gas desulfurization system of the present invention. The dotted line indicates the movement of the gas, and the solid line indicates the movement of the absorbing solution. The desulfurization system supplies the exhaust gas 10 supplied from the exhaust gas supply unit to the center of the flue gas desulfurization (FGD) 11. At this time, the primary desulfurization solution including the desulfurization agent is supplied to the water or slurry injector 1 on the top of the flue gas desulfurization apparatus 11, and in this case, the primary desulfurization is performed by contacting the combustion flue gas. The flue gas desulfurization apparatus 11 is preferably a wet flue gas desulfurization apparatus having an absorption tower, which sprays the absorption liquid from the nozzle in the absorption tower and contacts the absorption liquid and the exhaust gas in the absorption layer. The sulfur component in the contacted exhaust gas reacts with the absorbent liquid, and the absorbent liquid is converted into an acidic component and falls to the bottom of the tower. The lower absorbent liquid is neutralized with a neutralizing agent, and only the exhaust gas from which the sulfur component is removed is discharged from the top of the tower. The primary desulfurized exhaust gas is supplied to the membrane contactor 20 to perform secondary desulfurization.

The separator contactor is a separator cartridge including a plurality of hollow fiber membrane modules 21, and absorbs residual sulfur oxides in the exhaust gas desulfurized primarily in the flue gas desulfurization apparatus of the present invention. The separator is an interphase of a material having a function of selectively restricting the movement of a material between two phases. In the present invention, the separator is an interface between a gas and a liquid. The gas is a primary desulfurized exhaust gas and the liquid is a hollow fiber membrane for gas separation that separates the sulfide sulfide from the exhaust gas into an absorption solution capable of absorbing sulfur oxides in the exhaust gas. The hollow fiber membrane is made of a porous tubular polymer membrane, the sulfur oxide absorption solution flows to one side of the outer or inner side of the hollow fiber membrane, the exhaust gas flows to the other side. The absorbing solution and the primary desulfurized exhaust gas flow in different directions to facilitate the absorption of sulfur oxides. The absorbing solution is an alkaline solution, and in one embodiment the alkaline solution is KOH, MgO, MgCO ₃ , NaO, NaCO ₃ , NaOH, NaHCO ₃ , CaO, Ca (OH) ₂ , CaCO ₃ and NH ₃ At least one aqueous solution selected. The absorption solution absorbs residual sulfur oxides from the primary desulfurized exhaust gas.

When an alkali solution, such as NaOH, is used outside or inside the hollow fiber membrane, sulfur oxides in the primary desulfurized exhaust gas pass through the hollow fiber membrane and react as in Schemes 1 and 2 and are absorbed in the absorption solution.

Scheme 1

2NaOH + SO _2- > Na ₂ SO ₃ + H ₂ O

NaOH + SO _2- > NaHSO ₃

Na ₂ CO ₃ + SO _2- > Na ₂ SO ₃ + CO ₂

Na ₂ SO ₃ + SO ₂ + H ₂ O-> 2NaHSO ₃

Scheme 2

NaOH + SO _3- > Na ₂ SO ₄ + H ₂ O

The absorption solution in which the sulfur oxide is absorbed is supplied to the storage tank 30 through the membrane contactor sulfur oxide absorption solution supply line 32. The reservoir 30 is connected to the separator contactor 20, the lean absorption solution (low sulfur oxide content) supply line 31, the separator contactor sulfur oxide absorption solution supply line 32, and the separator contactor The water or slurry injection portion of the flue gas desulfurization apparatus 11 installed at the front end and the secondary desulfurization absorption solution treatment line 12 are connected. Depending on the concentration of the absorbent solution in the reservoir, the absorbent solution circulates in each position and can be operated in a continuous process. When the sulfur oxide concentration of the absorbent solution is increased, the absorbent solution is supplied to the water or slurry injection unit 1 of the flue gas desulfurization apparatus 11 through the secondary desulfurization absorbent solution supply line 12, and the alkaline solution is the flue gas desulfurization apparatus ( As it is injected into 11) there is an effect that the desulfurization effect of the flue gas desulfurization apparatus (11) is also improved. The membrane contactor may be provided with a depressurization pump 50, a manned blower, and the like to maintain a differential pressure in order to add a pressure difference from the absorbing solution to the primary desulfurized exhaust gas supplied from the flue gas desulfurization apparatus 11.

In another embodiment, the desulfurization system of the present invention uses a membrane contactor 200 that includes an absorption tower 201 and a degassing tower 202. 2 is a schematic diagram of a continuous process exhaust gas desulfurization system including an absorption tower 20 and a degassing tower 201 of the present invention. The dotted line indicates the movement of the gas, and the solid line indicates the movement of the absorbing solution. The desulfurization system comprises an exhaust gas supply unit 10; Flue gas desulfurization (FGD) 11 for performing primary desulfurization of the exhaust gas supplied from the exhaust gas supply unit; A separator contactor 200 for supplying the first desulfurized exhaust gas through the flue gas desulfurization apparatus to perform secondary desulfurization; And a sulfur oxide supply line 42 for injecting sulfur oxides discharged from the separator contactor into a backstroke desulfurization apparatus, wherein the separator contactor includes an hollow fiber membrane module 21 and an absorption tower 201 and a degassing tower 202. ). The absorption tower absorbs residual sulfur oxides in the exhaust gas desulfurized primarily by the flue gas desulfurization apparatus 11 using an absorption solution. Absorption solution absorbing sulfur oxide in the absorption tower 201 is supplied to the degassing tower 202 through the absorption tower rich solution (solution having a high sulfur oxide concentration) supply line 22 and the vacuum pump 50 in the degassing tower The pressure difference is generated using) to desorb the sulfur oxide from the absorbing solution.

The absorption tower and the degassing column are provided with a hollow fiber membrane module and the hollow fiber membrane is made of a porous tubular polymer membrane. The hollow fiber membrane in the absorption tower is an interface between the solution capable of absorbing sulfur oxides and the primary desulfurized exhaust gas, and the sulfur oxide absorbing solution flows to one side of the outside or the inside, and the exhaust gas flows to the other side. The absorbing solution and the primary desulfurized exhaust gas flow in different directions to facilitate the absorption of sulfur oxides. When the hollow fiber membrane in the degassing column is supplied through the degassing tower supply line 22 to the absorbing solution absorbing the sulfur oxide in the absorption tower through the degassing column supply line 22, the sulfur oxide is recovered in the gas state by depressurizing at the other side. do. The sulfur oxide recovered by the gas is supplied to the flue gas desulfurization apparatus. Absorption solution from which sulfur oxides are degassed is supplied to the absorption tower 201 through the degassing tower lean absorption solution supply line 41 to be reused and operated in a continuous process. The absorbing solution is an alkaline solution, and in one embodiment, the alkaline solution is at least one aqueous solution selected from the group consisting of KOH, MgO, NaOH, NaHCO ₃ , CaO, Ca (OH) ₂ , CaCO ₃ and NH ₃ .

The hollow fiber membrane used in the desulfurization system of the present invention has a diameter of 100 µm to 1,500 µm and preferably 400 µm to 1,000 µm. When the diameter is 100 μm or less, gas cannot pass smoothly due to pressure when gas is injected into the tubular polymer membrane, and when 1500 μm or more, the gas has a low contact probability with the polymer membrane wall, thereby reducing the gas passage efficiency of the membrane. The pore size is 10nm to 400nm has a size that can pass through the sulfur oxides. The surface of the tubular polymer membrane is porous, through which gas can permeate, whereas the water-soluble sulfur oxide absorption solution of the present invention is a hydrophobic membrane that cannot pass through. In one embodiment, the hydrophobic film is polypropylene, polyethersulfone, polysulfone, polyethyleneimide, polyimide, polyburnzimidazole, polyacrylate, poly-n-butylmethacrylate, polycarbonate, polyetheretherketone, A film made of at least one hydrophobic material selected from the group consisting of polyester sulfones, polyvinylidene fluorides, polyvinylpyrrolidones, polyvinylfluorides and polyvinylcarbazoles, or a film coated on the inside or the outside with said material . The coating may be coated inside or outside the polymer hollow fiber membrane.

Although the exemplary embodiments of the present application have been described in detail above, the scope of the present application is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to.

All technical terms used in the present invention, unless defined otherwise, are used in the meaning as commonly understood by those skilled in the art in the related field of the present invention. The contents of all publications described herein by reference are incorporated into the present invention.

1. Water or slurry inlet
10. Exhaust Gas Supply Line
11. Flue Gas Desulfurization System
12. Second Desulfurization Absorption Solution Treatment Line
20. Membrane Contactor
21. Hollow fiber membrane module
22. Absorption Tower Rich Absorption Solution Supply Line
30. Storage tank
31. Lean Absorption Solution Supply Line
32. Membrane Contactor Sulfur Oxide Absorption Solution Supply Line
41. Deaeration tower lean absorption solution supply line
42. Sulfur Oxide Supply Line
50. Pump
200. Membrane contactor including absorption tower and deaeration tower
201.The absorption tower
202. Degassing tower

Claims (6)

Continuous process exhaust gas desulfurization system,
The system comprises an exhaust gas supply;
Flue gas desulfurization (FGD) for performing primary desulfurization of the exhaust gas supplied from the exhaust gas supply unit;
A separator contactor for supplying the primary desulfurized exhaust gas through the flue gas desulfurization apparatus to perform secondary desulfurization;
A storage tank storing the sulfur oxide absorbing solution absorbed by the membrane contactor; And
And a secondary desulfurization absorption solution processing line for supplying the sulfur oxide absorption solution stored in the reservoir to the water or slurry supply unit of the flue gas desulfurization apparatus.
The membrane contactor comprises a hollow fiber membrane module,
Alkaline solution is circulated to the inner surface or the outer surface of the hollow fiber membrane,
Continuous process exhaust gas desulfurization system.
The method of claim 1,
The membrane contactor further includes a pressure reducing pump,
Continuous process exhaust gas desulfurization system.
Continuous process exhaust gas desulfurization system,
The system comprises an exhaust gas supply;
Flue gas desulfurization (FGD) for performing primary desulfurization of the exhaust gas supplied from the exhaust gas supply unit;
A separator contactor for supplying the first desulfurized exhaust gas through the flue gas desulfurization apparatus to perform secondary desulfurization; And
A sulfur oxide supply line for injecting sulfur oxides discharged from the separator contactor into FGD;
The separator contactor includes an absorption tower and a degassing tower including a hollow fiber membrane module,
An alkaline solution circulates on the inner side or the outer side of the hollow fiber membrane,
The primary desulfurized exhaust gas is supplied to the absorption tower so that sulfur oxides in the exhaust gas are absorbed into the alkaline solution.
The alkaline solution absorbing the sulfur oxide is supplied to the degassing tower to degas the sulfur oxide,
Sulfur oxide discharged from the degassing tower is re-supplied to the flue gas desulfurization apparatus,
Continuous process exhaust gas desulfurization system.
The method according to any one of claims 1 to 3,
The separator is polypropylene, polyether sulfone, polysulfone, polyethyleneimide, polyimide, polyburnimidazole, polyacrylate, poly-n-butyl methacrylate, polycarbonate, polyether ether ketone, polyester sulfone , A film made of at least one hydrophobic material selected from the group consisting of polyvinylidene fluoride, polyvinylpyrrolidone, polyvinylfluoride and polyvinylcarbazole, or a film coated on the inside or the outside,
Continuous process exhaust gas desulfurization system.
The method according to any one of claims 1 to 3,
The alkaline solution is KOH, MgO, MgCO ₃ , NaO, NaCO ₃ , NaOH, NaHCO ₃ , CaO, Ca (OH) ₂ , CaCO ₃ and At least one aqueous solution selected from the group consisting of NH ₃ ,
Continuous process exhaust gas desulfurization system.
The method according to any one of claims 1 to 3,
The gas phase and the liquid phase supplied to the hollow fiber membrane module flow in different directions,
Continuous process exhaust gas desulfurization system.

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