Composite desulfurizer for removing SO2, NOx and HCl and preparation method thereof

Abstract

The invention belongs to the technical field of adsorption desulfurizing agents, and particularly provides a composite desulfurizing agent for removing SO2, NOX and HCl and a preparation method thereof, and the composite desulfurizing agent comprises the following components in parts by weight: 25-35 parts of a desulfurizing agent, 30-50 parts of a denitrifying agent and 10-15 parts of modified activated carbon. The composite desulfurizer can efficiently remove SO2, NOX and HCl at the same time, the problem that a traditional single desulfurizer can only aim at one pollutant is effectively solved, the desulfurization efficiency is remarkably improved, and the increasingly strict environmental protection requirement is met; meanwhile, the composite desulfurizer is good in reproducibility, the desulfurization cost is reduced, the generation of wastes is reduced, the requirements of environmental protection and sustainable development are met, and the composite desulfurizer can be used in a high-temperature environment and is suitable for being used in a waste incineration plant.

Description

Technical Field

[0001] The present invention belongs to the technical field of adsorption desulfurization agent, and specifically relates to a method for removing SO2, NO X A composite desulfurizing agent for desulfurizing HCl and a preparation method thereof. Background Art

[0002] With the acceleration of industrialization, the pollution of flue gas emissions to the environment is becoming increasingly serious, including sulfur dioxide (SO), nitrogen oxides (NO x ) and hydrogen chloride (HCl) are the main pollutants. Waste incineration has become the main method of treating domestic waste in my country. Domestic waste contains a large amount of organic matter, which generally contains sulfur, chlorine and nitrogen elements. During the combustion process, it is decomposed by heat and undergoes strong high-temperature oxidation, releasing atmospheric pollutants. However, traditional desulfurization, denitrification and dechlorination technologies are mostly for single pollutant treatment, and have problems such as low efficiency, high cost and secondary pollution. In recent years, multi-pollutant synergistic removal technology has gradually attracted attention, aiming to develop a method that can simultaneously and efficiently remove SO, NO x and HCl composite desulfurizer.

[0003] Chinese patent CN 107297144 B discloses a composite desulfurizer, which comprises, by weight, 1-15% cyanuric acid, 1-15% cosolvent, 1-20% catalyst, 0-10% chelating agent, 1-20% stabilizer, and 50-95% water. This composite desulfurizer is low-cost, readily available, and capable of achieving efficient desulfurization and denitrification. However, components such as water and the chelating agent ethylenediamine readily decompose and volatilize at high temperatures, making it unsuitable for flue gas treatment in the waste incineration industry.

[0004] Therefore, there is an urgent need to develop a new type of composite desulfurizer and its preparation method, aiming to achieve high efficiency in the synergistic removal of multiple atmospheric pollutants under high temperature environment, while also achieving economic and environmental benefits. Summary of the Invention

[0005] In view of the existing technical problems, the present invention aims to provide a method for removing SO2, NO X The composite desulfurizer of the present invention can remove SO2, NO and HCl at the same time with high efficiency. X The composite desulfurizer of the present invention is highly recyclable and can be regenerated and reused through simple heat or chemical treatment. This reduces desulfurization costs and waste generation, meeting the requirements of environmental protection and sustainable development. The composite desulfurizer can be used in high-temperature environments and is suitable for use in waste incineration plants.

[0006] On the one hand, the present invention provides a method for removing SO2 and NO X The composite desulfurizer comprises the following components in parts by weight: 25-35 parts of desulfurizer, 30-50 parts of denitrifier, and 10-15 parts of modified activated carbon.

[0007] The reaction mechanism and effects of the present invention are as follows:

[0008] 1. The desulfurizing agent of the present invention adopts a composition of calcium hydroxide, calcium carbonate and calcium sulfate, which can effectively reduce the discharge of pollutants such as sulfur dioxide, nitrogen oxides and hydrogen chloride, and is conducive to environmental protection. Calcium hydroxide and calcium carbonate are commonly used desulfurizing agents, and the two can be used in combination to effectively improve desulfurization efficiency and reduce costs, and the introduction of calcium sulfate can effectively improve the strength of the product, which makes the stability of the composite desulfurizing agent improved, enhances reproducibility, and reduces subsequent processing costs. In addition, the applicant found that after calcium sulfate is contacted and mixed with calcium hydroxide and calcium carbonate, it is conducive to improving denitrification efficiency.

[0009] 2. The addition of a small amount of magnesium oxide to the calcium-based desulfurizer of the present invention can increase the calcium conversion rate, thereby improving the removal of acidic gases. This may be because the presence of magnesium oxide provides a supporting skeleton and better maintains the pore structure.

[0010] 3. Montmorillonite has a layered structure with a large interlayer distance, which can provide additional adsorption sites. By adding dimethylaminoethyl methacrylate and dodecyltrimethylammonium bromide to organically modify montmorillonite, the interlayer distance of montmorillonite is further expanded, increasing the adsorption capacity. At the same time, the addition of dodecyltrimethylammonium bromide makes montmorillonite more hydrophobic, reducing the adsorption of water molecules. This hydrophobicity can improve the stability of activated carbon under high humidity conditions, reduce the impact of water poisoning, and further improve the water poisoning resistance of activated carbon. Furthermore, the present invention improves the dispersibility of titanium dioxide by intercalating it into montmorillonite, thereby improving the adsorption performance and stability. Furthermore, the double bonds introduced on the titanium dioxide / montmorillonite composite material can be grafted with coconut shell activated carbon through the double bonds on 3-vinyl-1-(2-propylene-1-yl)-1H-imidazole tetrafluoroborate, ensuring that the titanium dioxide / montmorillonite composite material is stably attached to the activated carbon, which not only reduces the possibility of activated carbon pore collapse during the regeneration process, but also reduces SO2, NO X There is a van der Waals force between the HCl molecules and the surface molecules of the titanium dioxide particles. When the molecules on the surface of titanium dioxide are heated, the adsorbed SO2 and NO X And HCl molecules can be desorbed from titanium dioxide, thereby improving the desulfurization, denitrification and dechlorination performance and regeneration function of the modified activated carbon.

[0011] In some embodiments, the desulfurizing agent is a combination of calcium hydroxide, calcium carbonate and calcium sulfate.

[0012] In some embodiments, the mass ratio of calcium hydroxide, calcium carbonate and calcium sulfate is 10:(9.5-10.5):(0.08-0.2).

[0013] Preferably, the particle size of the desulfurizing agent is 150-300 mesh.

[0014] In some embodiments, the denitrification agent comprises any one or more of urea, polyaniline, and polyamide.

[0015] In some embodiments, the method for preparing the modified activated carbon comprises the following steps:

[0016] Q1. Mix sodium montmorillonite with deionized water and stir. Adjust the pH of the dispersion to 4.5-5.5. Add dimethylaminoethyl methacrylate and dodecyltrimethylammonium bromide. Heat to 60-80°C for 1-1.5 hours. Cool, filter under reduced pressure to obtain a solid, dry, and grind to obtain pretreated montmorillonite.

[0017] Q2. Tetrabutyl titanate and an ethanol aqueous solution were mixed and stirred, and the pretreated montmorillonite obtained in step Q1 was added, heated to 60-80 ° C and stirred for 2-4h, cooled, washed, and dried to obtain a titanium dioxide / montmorillonite composite material;

[0018] Q3. Coconut shell activated carbon was mixed with deionized water, stirred, 3-vinyl-1-(2-propylene-1-yl)-1H-imidazole tetrafluoroborate and N,N-dimethylformamide were added, heated to 50-70 ° C and stirred for 20-30 hours, and then the titanium dioxide / montmorillonite composite material and initiator obtained in step Q2 were added. The reaction was carried out at 60-80 ° C under inert gas protection, cooled, washed, filtered, and dried to obtain modified activated carbon.

[0019] In some embodiments, the mass ratio of sodium montmorillonite, dimethylaminoethyl methacrylate and dodecyltrimethylammonium bromide in step Q1 is 10:(0.5-0.7):(0.35-0.55).

[0020] In some embodiments, the mass ratio of the pretreated montmorillonite to tetrabutyl titanate in step Q2 is 1:(0.5-1).

[0021] In some embodiments, the mass ratio of 3-vinyl-1-(2-propylene-1-yl)-1H-imidazole tetrafluoroborate, coconut shell activated carbon and titanium dioxide / montmorillonite composite material in step Q3 is (14-18):(400-600):1.

[0022] In some embodiments, the composite desulfurizer further comprises 4-6 parts of magnesium oxide by weight.

[0023] Another aspect of the present invention is to provide a method for removing SO2 and NO as described in the above scheme. X A method for preparing a composite desulfurizer for HCl comprises the following steps:

[0024] The desulfurizer, the denitrifier and the modified activated carbon are mixed to obtain a composite desulfurizer.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The composite desulfurizer of the present invention can simultaneously and efficiently remove SO2 and NO X The composite desulfurizer of the present invention combines sulfur dioxide, HCl, and nitric oxide, effectively solving the problem of traditional single desulfurizers that can only target one pollutant, significantly improving desulfurization efficiency and meeting increasingly stringent environmental protection requirements. Furthermore, the composite desulfurizer of the present invention has good renewability, reduces desulfurization costs, and reduces waste generation, meeting the requirements of environmental protection and sustainable development. Furthermore, the composite desulfurizer can be used in high-temperature environments and is suitable for use in waste incineration plants.

[0027] Among the traditional processes, semi-dry, dry, and wet desulfurization all require treatment after the pollutants are generated. The cost of post-generation treatment is high, and a large amount of fly ash is generated. The composite desulfurizer of the present invention can be used in the front-end control of pollutant generation, replacing traditional processes, abolishing traditional desulfurization systems, activated carbon systems, etc., and thus can effectively reduce the amount of fly ash by nearly 50%.

[0028] 2. The desulfurizer of the present invention adopts a combination of calcium hydroxide, calcium carbonate and calcium sulfate, which can effectively and synergistically reduce the emission of pollutants such as sulfur dioxide, nitrogen oxides and hydrogen chloride, which is beneficial to environmental protection.

[0029] 3. The magnesium oxide of the present invention can increase the calcium conversion rate, thereby improving the removal of acidic gases.

[0030] 4. On the one hand, the present invention further expands the interlayer spacing of montmorillonite by adding dimethylaminoethyl methacrylate and dodecyltrimethylammonium bromide, thereby increasing its adsorption capacity. Simultaneously, the pretreated montmorillonite exhibits enhanced hydrophobicity, which can improve the activated carbon's resistance to water poisoning. On the other hand, titanium dioxide is intercalated into the montmorillonite to enhance its dispersibility, thereby improving its adsorption performance and stability. Subsequently, the titanium dioxide / montmorillonite composite material can be grafted onto coconut shell activated carbon, reducing the possibility of activated carbon pore collapse during regeneration and enhancing the modified activated carbon's desulfurization, denitrification, and dechlorination performance, as well as its regeneration function. DETAILED DESCRIPTION

[0031] The present invention will be described below in conjunction with specific embodiments. It should be noted that the following examples are illustrative of the present invention and are intended only to illustrate the present invention, not to limit the present invention. Other combinations and various modifications within the scope of the present invention may be made without departing from the spirit or scope of the present invention.

[0032] The composite desulfurizers were prepared according to the ratios of the raw materials and the preparation methods specified in the following examples and comparative examples.

[0033] In order to facilitate those skilled in the art to implement the present invention, some raw material manufacturers of the embodiments and comparative examples are described as follows:

[0034] The particle size of the desulfurizers calcium hydroxide, calcium carbonate, and calcium sulfate is 200 mesh;

[0035] Coconut shell activated carbon: purchased from Henan Yutai Environmental Protection Materials Co., Ltd., model yt-19;

[0036] Unless otherwise specified, other raw materials can be purchased from the market.

[0037] Preparation Example 1

[0038] The preparation method of modified activated carbon A comprises the following steps:

[0039] Q1. 200 g of sodium montmorillonite was mixed with 400 mL of deionized water and stirred until uniformly distributed. The pH of the dispersion was adjusted to 5. 12 g of dimethylaminoethyl methacrylate and 9 g of dodecyltrimethylammonium bromide were added. The mixture was heated to 70°C for 1 h, cooled to room temperature, and the solid was filtered under reduced pressure. The solid was dried at 105°C for 4 h and ground to obtain the pretreated montmorillonite.

[0040] Q2. 90 g of tetrabutyl titanate and 300 mL of a 50 wt% aqueous ethanol solution were mixed and stirred, and 120 g of the pretreated montmorillonite obtained in step Q1 was added. The mixture was heated to 70 ° C and stirred for 3 h, cooled to room temperature, washed twice with deionized water, and dried at 105 ° C for 10 h to obtain a titanium dioxide / montmorillonite composite material;

[0041] Q3. 5000g of coconut shell activated carbon was mixed with 40L of deionized water and stirred evenly. 160g of 3-vinyl-1-(2-propylene-1-yl)-1H-imidazole tetrafluoroborate and 5000mL of N,N-dimethylformamide were added, and the mixture was heated to 60°C and stirred for 24h. Then, 10g of the titanium dioxide / montmorillonite composite material obtained in step Q2 and 1.5g of azobisisobutyronitrile were added. The mixture was reacted at 80°C under nitrogen for 3h, cooled to room temperature, washed twice with deionized water, and filtered under reduced pressure to obtain a solid. The solid was dried at 105°C for 12h and ground to obtain modified activated carbon A.

[0042] Preparation Example 2

[0043] The preparation method of modified activated carbon B is the same as that of Preparation Example 1, except that the amount of dimethylaminoethyl methacrylate added in step Q1 is 8 g.

[0044] Preparation Example 3

[0045] The preparation method of modified activated carbon C is the same as that of Preparation Example 1, except that the amount of dodecyltrimethylammonium bromide added in step Q1 is 5 g.

[0046] Preparation Example 4

[0047] The preparation method of modified activated carbon D is the same as that of Preparation Example 1, except that the amount of tetrabutyl titanate added in step Q2 is 55 g.

[0048] Preparation Example 5

[0049] The preparation method of modified activated carbon E is the same as that of Preparation Example 1, except that in step Q3, the amount of 3-vinyl-1-(2-propylene-1-yl)-1H-imidazole tetrafluoroborate added is 130 g.

[0050] Example 1

[0051] A method for removing SO2 and NO X The composite desulfurizer for preparing HCl comprises, by weight, 30 parts of a desulfurizer, 40 parts of a denitrifier, and 12.5 parts of modified activated carbon A; wherein, the desulfurizer is composed of calcium hydroxide, calcium carbonate, and calcium sulfate in a mass ratio of 10:10:0.14, and the denitrifier is urea.

[0052] The preparation method of the composite desulfurizer of the present invention comprises the following steps:

[0053] The desulfurizer, the denitrifier and the modified activated carbon A are mixed to obtain a composite desulfurizer.

[0054] Example 2

[0055] A method for removing SO2 and NO X The composite desulfurizer for preparing HCl comprises, by weight, 30 parts of a desulfurizer, 40 parts of a denitrifier, 12.5 parts of modified activated carbon A, and 5 parts of magnesium oxide; wherein the desulfurizer is composed of calcium hydroxide, calcium carbonate, and calcium sulfate in a mass ratio of 10:10:0.14, and the denitrifier is urea.

[0056] The preparation method of the composite desulfurizer of the present invention comprises the following steps:

[0057] The desulfurizer, the denitrifier, the modified activated carbon A and the magnesium oxide are mixed to obtain a composite desulfurizer.

[0058] Example 3

[0059] A method for removing SO2 and NO X The composite desulfurizer for preparing HCl comprises, by weight, 25 parts of a desulfurizer, 30 parts of a denitrifier, and 10 parts of modified activated carbon A; wherein, the desulfurizer is composed of calcium hydroxide, calcium carbonate, and calcium sulfate in a mass ratio of 10:9.5:0.08, and the denitrifier is urea.

[0060] The preparation method of the composite desulfurizer of the present invention is the same as that of Example 1.

[0061] Example 4

[0062] A method for removing SO2 and NO X The composite desulfurizer for preparing HCl comprises, by weight, 35 parts of a desulfurizer, 50 parts of a denitrifier, and 15 parts of modified activated carbon A; wherein, the desulfurizer is composed of calcium hydroxide, calcium carbonate, and calcium sulfate in a mass ratio of 10:10.5:0.2, and the denitrifier is urea.

[0063] The preparation method of the composite desulfurizer of the present invention is the same as that of Example 1.

[0064] Example 5

[0065] A method for removing SO2 and NO X The composite desulfurizer for desulfurizing HCl and the preparation method thereof are the same as those in Example 1, except that an equal amount of modified activated carbon B is used instead of modified activated carbon A.

[0066] Example 6

[0067] A method for removing SO2 and NO X The composite desulfurizer for desulfurizing HCl and the preparation method thereof are the same as those in Example 1, except that an equal amount of modified activated carbon C is used instead of modified activated carbon A.

[0068] Example 7

[0069] A method for removing SO2 and NO X The composite desulfurizer for desulfurizing HCl and the preparation method thereof are the same as those in Example 1, except that an equal amount of modified activated carbon D is used instead of modified activated carbon A.

[0070] Example 8

[0071] A method for removing SO2 and NO X The composite desulfurizer for desulfurizing HCl and the preparation method thereof are the same as those in Example 1, except that an equal amount of modified activated carbon E is used instead of modified activated carbon A.

[0072] Example 9

[0073] A method for removing SO2 and NO X The composite desulfurizer for desulfurizing HCl and the preparation method thereof are the same as those in Example 1, except that the desulfurizer is composed of calcium hydroxide and calcium carbonate in a mass ratio of 1:1.

[0074] Comparative Example 1

[0075] A method for removing SO2 and NO X The composite desulfurizer for desulfurizing HCl and the preparation method thereof are the same as those in Example 1, except that an equal amount of coconut shell activated carbon is used instead of modified activated carbon A.

[0076] Effect evaluation:

[0077] The composite desulfurizers prepared in Examples 1-9 and Comparative Example 1 were tested and analyzed, and the specific results are shown in Table 1-2.

[0078] Performance testing:

[0079] (1) A flue gas purification ultra-low emission system was built behind a small mechanical grate-type waste incinerator in a county-level waste incineration plant in southwest my country. The composite desulfurizer was introduced into the high-temperature removal reaction chamber of the flue gas purification ultra-low emission system. The residence time of the high-temperature flue gas in the reaction chamber was 4s. The amount of composite desulfurizer used was controlled at 15kg / t of waste. The high-temperature flue gas treatment capacity of the device was 16000Nm 3 / h, using flue gas analyzer to measure and analyze SO2 and NO before and after treatment X and HCl removal rate.

[0080] Table 1

[0081] Serial number <![CDATA[SO2 removal rate / %]]> <![CDATA[NO X Removal rate / %]]> HCl removal rate / % Example 1 99.4 98.6 95.2 Example 2 99.6 98.8 95.5 Example 3 98.9 97.5 94.9 Example 4 99.4 98.5 95.2 Example 5 96.5 95.5 94.2 Example 6 97.9 96.4 93.7 Example 7 97.1 95.9 93.3 Example 8 97.4 96.1 94.0 Example 9 99.0 96.5 94.9 Comparative Example 1 93.2 92.4 89.8

[0082] The results in Table 1 show that the composite desulfurizers prepared in Examples 1-4 have excellent adsorption removal rates and can simultaneously and efficiently remove SO2 and NO. X and HCl.

[0083] Compared with Example 1, when preparing modified activated carbon, Examples 5-6 changed the mass ratio of sodium montmorillonite, dimethylaminoethyl methacrylate and dodecyltrimethylammonium bromide, and the adsorption capacity decreased. Example 7 changed the mass ratio of pretreated montmorillonite and tetrabutyl titanate, and the stability and adsorption of the modified activated carbon decreased. Example 8 changed the mass ratio of 3-vinyl-1-(2-propylene-1-yl)-1H-imidazole tetrafluoroborate, coconut shell activated carbon and titanium dioxide / montmorillonite composite material, resulting in weak grafting stability of titanium dioxide / montmorillonite composite material and coconut shell activated carbon, which will affect SO2, NO in Examples 5-8. X and HCl removal efficiency.

[0084] Compared with Example 1, Example 9 does not add calcium sulfate, and the strength of the product is reduced, which affects the removal efficiency, especially the denitrification efficiency.

[0085] Comparative Example 1 Compared with Example 1, the same amount of commercial coconut shell activated carbon was used, SO2, NO X The removal efficiency of HBr and HCl decreased significantly.

[0086] (2) The regeneration performance of the composite desulfurizers of Examples 1-2 and Comparative Example 1 was evaluated. The composite desulfurizers were applied to flue gas for 3 regeneration cycles. The SO2 concentration in the flue gas was 500 mg / Nm 3 .

[0087] Table 2

[0088]

[0089] As shown in Table 2, the composite desulfurizer prepared in Examples 1-2 has excellent regeneration properties and still has a high desulfurization rate; while the coconut shell activated carbon in Comparative Example 1 has relatively poor adsorption desulfurization properties after regeneration cycles.

[0090] The above is only a preferred embodiment of the present invention and does not limit the present application in any form. Although the present application is disclosed as above with a preferred embodiment, it is not intended to limit the present application. Any technician familiar with this profession, without departing from the scope of the technical solution of the present application, makes some changes or modifications using the technical content disclosed above, which are equivalent to equivalent implementation cases. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution.

Claims

1. A method for removing SO2 and NO X and HCl composite desulfurizer, characterized in that, The composite desulfurizer comprises the following components in parts by weight: 25-35 parts of desulfurizer, 30-50 parts of denitrifier, and 10-15 parts of modified activated carbon.

2. A method for removing SO2 and NO according to claim 1 X and HCl composite desulfurizer, characterized in that, The desulfurizing agent is a combination of calcium hydroxide, calcium carbonate and calcium sulfate.

3. A method for removing SO2 and NO according to claim 2 X and HCl composite desulfurizer, characterized in that, The mass ratio of the calcium hydroxide, calcium carbonate and calcium sulfate is 10: (9.5-10.5): (0.08-0.2).

4. A method for removing SO2 and NO according to claim 1 X and HCl composite desulfurizer, characterized in that, The denitrification agent comprises any one or more of urea, polyaniline and polyamide.

5. A method for removing SO2 and NO according to claim 1 X and HCl composite desulfurizer, characterized in that, The preparation method of the modified activated carbon comprises the following steps: Q1. Mix sodium montmorillonite with deionized water and stir. Adjust the pH of the dispersion to 4.5-5.

5. Add dimethylaminoethyl methacrylate and dodecyltrimethylammonium bromide. Heat to 60-80°C for 1-1.5 hours. Cool, filter under reduced pressure to obtain a solid, dry, and grind to obtain pretreated montmorillonite. Q2. Tetrabutyl titanate and an ethanol aqueous solution were mixed and stirred, and the pretreated montmorillonite obtained in step Q1 was added, heated to 60-80 ° C and stirred for 2-4h, cooled, washed, and dried to obtain a titanium dioxide / montmorillonite composite material; Q3. Coconut shell activated carbon was mixed with deionized water, stirred, 3-vinyl-1-(2-propylene-1-yl)-1H-imidazole tetrafluoroborate and N,N-dimethylformamide were added, heated to 50-70 ° C and stirred for 20-30 hours, and then the titanium dioxide / montmorillonite composite material and initiator obtained in step Q2 were added. The reaction was carried out at 60-80 ° C under inert gas protection, cooled, washed, filtered, and dried to obtain modified activated carbon.

6. A method for removing SO2 and NO according to claim 5 X and HCl composite desulfurizer, characterized in that, The mass ratio of sodium montmorillonite, dimethylaminoethyl methacrylate and dodecyltrimethylammonium bromide in step Q1 is 10:(0.5-0.7):(0.35-0.55).

7. A method for removing SO2 and NO according to claim 5. X and HCl composite desulfurizer, characterized in that, The mass ratio of the pretreated montmorillonite to tetrabutyl titanate in step Q2 is 1:(0.5-1).

8. A method for removing SO2 and NO according to claim 5 X and HCl composite desulfurizer, characterized in that, The mass ratio of 3-vinyl-1-(2-propylene-1-yl)-1H-imidazole tetrafluoroborate, coconut shell activated carbon and titanium dioxide / montmorillonite composite material in step Q3 is (14-18):(400-600):

1.

9. A method for removing SO2 and NO according to claim 1 X and HCl composite desulfurizer, characterized in that, The components further include 4-6 parts of magnesium oxide by weight.

10. A method for removing SO2 and NO according to any one of claims 1 to 8 X and a method for preparing a composite desulfurizing agent for HCl, characterized in that: The following steps are included: The desulfurizer, the denitrifier and the modified activated carbon are mixed to obtain a composite desulfurizer.

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