Wet flue gas denitration system and method

Abstract

The invention discloses a wet catalytic flue gas denitration system and method, and belongs to the field of waste gas treatment. The wet-process catalytic flue gas denitration system mainly comprises a filler absorption tower, a circulating spraying system, a temperature control system, a pH control system and a product post-treatment system, the filler is a bimetallic modified porous catalytic material; the absorption liquid is an oxidant solution. Flue gas enters an absorption tower, contained low-valence NO makes reverse contact with spraying liquid in a filler layer and is catalytically oxidized into water-soluble high-valence nitric oxide, meanwhile, absorption liquid is used for washing the flue gas, the high-valence nitric oxide in the flue gas is washed into a solution, a nitrate solution is generated through reaction, and resource utilization is achieved after treatment is conducted through a product aftertreatment system. The flue gas denitration rate is high, the process operation is simple, the product can be recycled, the operation cost is low, the application range is wide, and the system is an efficient flue gas purification system with a wide application prospect.

Description

Technical Field

[0001] The invention relates to a flue gas denitration technology, and in particular to a low-temperature flue gas denitration technology of a bimetallic modified porous catalytic material coupled with an oxidative absorption liquid. Background Art

[0002] Against the backdrop of increasing global attention to environmental protection, the emission control of nitrogen oxides (NOx) in industrial flue gas has become a key problem that needs to be solved urgently. Conventional selective catalytic reduction (SCR) denitrification technology has exposed obvious limitations when dealing with complex flue gas conditions with low flue gas temperature and high moisture content. In a low temperature environment, the activity of the catalyst will be significantly reduced, resulting in a significant decline in the denitrification efficiency; and high-humidity flue gas can easily poison and clog the catalyst, greatly affecting the stability and service life of the system. Therefore, the development of a technology that can efficiently and economically remove NOx under low temperature conditions is particularly important for reducing air pollution and meeting increasingly stringent environmental protection regulations.

[0003] In traditional wet denitrification, the oxidation efficiency of H2O2 is low (<50%) under non-catalytic conditions, and excessive addition can easily lead to waste of reagents; and single metal catalysts (such as Fe or Mn-based) are prone to passivation and deactivation, which restricts the promotion of technology. Although the existing wet flue gas denitrification technology can use liquid absorbents to absorb and convert NOx in flue gas, a large amount of absorbent is usually required to achieve the ideal denitrification effect. Especially for flue gas with higher NOx concentrations, as the reaction continues, the absorbent is continuously consumed and needs to be continuously replenished, which undoubtedly greatly increases the operating cost. Moreover, most existing technologies are insufficient in the treatment and resource utilization of denitrification products, resulting in waste of resources and potential secondary pollution risks. The various new denitrification technologies that have been proposed currently still have many defects in terms of economic cost, treatment efficiency and applicability, and need further innovation and improvement. Summary of the invention

[0004] In view of the above problems, the present invention provides a flue gas denitrification system and method, which can achieve efficient removal of nitrogen oxides in flue gas under low temperature conditions and simultaneously perform resource utilization of products. It has the advantages of high denitrification rate, simple process operation, resource utilization of products, low operating costs, and a wide range of adaptability.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A wet flue gas denitrification system comprises a packed absorption tower, a circulating spraying system, a temperature control system, a pH control system and a product post-processing system; the packed absorption tower is filled with a bimetallic modified porous catalytic material, and the absorption liquid in the spraying system is a solution containing an oxidant.

[0007] A further improvement is that the porous carrier of the bimetallic modified porous catalytic material is any one of foam ceramics, foam nickel, zeolite molecular sieve, alumina, silicon dioxide and titanium dioxide.

[0008] A further improvement is that the bimetallic active components in the bimetallic modified porous catalytic material are a combination of any two of Fe, Co, Ni, Cu, Mn, Ti, and Ce.

[0009] A further improvement is that the oxidant is any one of hydrogen peroxide, hypochlorous acid, chlorous acid, potassium peroxymonosulfate, and potassium peroxydisulfate, or a combination of several of them.

[0010] A further improvement is that the product post-processing system is any one of an evaporation crystallization device, an adsorption-desorption device, and an electrodialysis concentration device.

[0011] A wet flue gas denitrification method, the flue gas enters a packed absorption tower, and the low-valent NO contained in it is catalytically oxidized to water-soluble high-valent nitrogen oxides in reverse contact with the spray liquid in the packing layer. At the same time, the flue gas is washed with an absorption liquid, and the high-valent nitrogen oxides in the flue gas are washed into a solution, reacting to generate a nitrate solution, which is then processed by a product post-treatment system for resource utilization.

[0012] Further improvements are: the flue gas temperature at the inlet of the packed absorption tower does not exceed 110°C, and the NO concentration in the flue gas is 50-500 mg / m 3 The temperature of the circulating absorption liquid sprayed into the packed absorption tower is 30℃-60℃, and the liquid-gas ratio is 5L / m 3 -20 L / m 3 The mass percentage concentration of the oxidant is 0.01%-20%, and the pH of the absorption liquid is controlled between 3-11.

[0013] Due to the adoption of the above technical solution, the technical progress achieved by the present invention is:

[0014] The method of the present invention is that flue gas is purified by a packed absorption tower equipped with a bimetallic modified porous catalytic material, and the coupling effect of the bimetallic modified porous catalytic material and the oxidant in the absorption liquid is utilized to catalytically oxidize low-valent NO in the flue gas into water-soluble high-valent nitrogen oxides, and the absorption liquid is used to wash the flue gas at the same time, and the high-valent nitrogen oxides in the flue gas are washed into the solution. Compared with the porous material without a catalyst load, the NO removal rate is increased by 15%-30%, and the treated flue gas NOx can meet the emission standards; the reaction generates a nitrate solution, and the nitrate byproduct is obtained after being treated by a post-treatment system, so that resource utilization can be realized.

[0015] The porous carrier of the bimetallic modified porous catalytic material used in the present invention has a wide range of sources, a simple preparation process, and good stability of the catalytic material; the reaction conditions of the oxidant in the absorption liquid are mild, the operating cost is low, and the efficient removal of NO in the flue gas can be achieved; the by-product nitrate can be used as a resource, the secondary pollution is small, and the environmental and economic benefits are obvious. It has the advantages of high denitrification rate, simple process operation, product resource utilization, low operating cost, wide application range, etc., and obvious environmental and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a process flow chart of the system of the present invention, wherein: 1. a packed absorption tower, 2. a circulating spraying system, 3. a temperature control system, 4. a pH control system, and 5. a product post-processing system.

[0017] Figure 2 1 and 2 are SEM images of the porous materials of Example 1 and Comparative Example 1.

[0018] Figure 3 It is a comparison curve diagram of Example 1 and Comparative Example 1 DETAILED DESCRIPTION

[0019] The following will be described clearly and completely in conjunction with the technical solutions in the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] Embodiment 1

[0021] Initial concentration 200mg / m 3 After the NO flue gas enters the absorption tower equipped with Fe-Ce modified foam ceramic filler, the 1% hydrogen peroxide oxidized absorption liquid is sprayed through the circulating spray system to purify the NO waste gas, and the liquid-gas ratio is 15L / m 3 At the same time, the temperature of the hydrogen peroxide oxidation absorption liquid is maintained at about 50°C through the temperature control system, and the pH control system maintains the pH of the hydrogen peroxide oxidation absorption liquid at about 9. The system has a NO removal rate of about 87.1%, and the final product of NO after purification is NO3 - , and further evaporated and crystallized through a product post-processing device to obtain a nitrate by-product.

[0022] The reaction mechanism is mainly as follows:

[0023]

[0024] Embodiment 2

[0025] Initial concentration 100 mg / m 3After the NO flue gas enters the absorption tower filled with Co-Mn modified zeolite molecular sieve packing, the 0.3% sodium hypochlorite oxidation absorption liquid is sprayed through the circulating spray system to purify the NO waste gas, and the liquid-gas ratio is 10L / m 3 At the same time, the temperature of the sodium hypochlorite oxidation absorption liquid is maintained at about 30°C through the temperature control system, and the pH control system maintains the pH of the sodium hypochlorite oxidation absorption liquid at about 3. The system has a NO removal rate of about 90.1%, and the final product of NO after purification is NO3 - , and further evaporated and crystallized through a product post-processing device to obtain a nitrate by-product.

[0026] Embodiment 3

[0027] The same simulated flue gas enters the absorption tower device of the same specifications.

[0028] Initial concentration 400mg / m 3 After the NO flue gas enters the absorption tower equipped with Fe-Co modified titanium dioxide filler, the sodium chlorite oxidation absorption liquid with a concentration of 0.02% is sprayed through the circulating spray system to purify the NO waste gas, and the liquid-gas ratio is 10L / m 3 At the same time, the temperature of the sodium chlorite oxidation absorption liquid is maintained at about 30°C through the temperature control system, and the pH control system maintains the pH of the sodium chlorite oxidation absorption liquid at about 3. The system has a NO removal rate of about 95.3%, and the final product of NO after purification is NO3 - , and further through an electrodialysis concentrated product post-treatment device to obtain a nitrate by-product.

[0029] Comparative Example 1

[0030] Simple foam ceramic filler carrier

[0031] Initial concentration 200mg / m 3 After the NO flue gas enters the absorption tower equipped with foam ceramic filler, the 1% hydrogen peroxide absorption liquid is sprayed through the circulating spray system to purify the NO waste gas. The liquid-gas ratio is 10L / m 3 At the same time, the temperature of the hydrogen peroxide solution is maintained at about 50°C through the temperature control system, and the pH control system maintains the pH of the hydrogen peroxide solution at about 9. The system has a NO removal rate of about 60.4%, and the final product of NO after purification is NO3 - , and further evaporated and crystallized through a product post-processing device to obtain a nitrate by-product.

[0032] Comparative Example 2

[0033] Simple zeolite molecular sieve filler carrier

[0034] Initial concentration 100 mg / m 3After the NO flue gas enters the absorption tower filled with zeolite molecular sieve fillers, the 0.3% sodium hypochlorite oxidation absorption liquid is sprayed through the circulating spray system to purify the NO waste gas. The liquid-gas ratio is 10L / m 3 At the same time, the temperature of the sodium hypochlorite oxidation absorption liquid is maintained at about 30°C through the temperature control system, and the pH control system maintains the pH of the sodium hypochlorite oxidation absorption liquid at about 3. The system has a NO removal rate of about 68.2%, and the final product of NO after purification is NO3 - , and further evaporated and crystallized through a product post-processing device to obtain a nitrate by-product.

Claims

1. A wet flue gas denitrification system, characterized in that: The system comprises a packing absorption tower, a circulating spraying system, a temperature control system, a pH control system and a product post-processing system; the packing absorption tower is filled with bimetallic modified porous catalytic materials, and the spraying absorption liquid is a solution containing an oxidant.

2. A wet flue gas denitrification system according to claim 1, characterized in that: The porous carrier of the bimetallic modified porous catalytic material is any one of foam ceramics, foam nickel, zeolite molecular sieve, alumina, silicon dioxide and titanium dioxide.

3. A wet flue gas denitrification system according to claim 1, characterized in that: The bimetallic active components in the bimetallic modified porous catalytic material are a combination of any two of Fe, Co, Ni, Cu, Mn, Ti, and Ce.

4. A wet flue gas denitrification system according to claim 1, characterized in that: The oxidant is any one of hydrogen peroxide, hypochlorous acid, chlorous acid, potassium peroxymonosulfate, and potassium peroxydisulfate, or a combination of several of them.

5. A wet flue gas denitrification system according to claim 1, characterized in that: The product post-processing system is any one of an evaporation crystallization device, an adsorption-desorption device, and an electrodialysis concentration device.

6. A wet flue gas denitrification method, characterized in that: The flue gas enters the packed absorption tower, and the low-valent NO contained in it is catalytically oxidized into water-soluble high-valent nitrogen oxides in the reverse contact between the packing layer and the spray liquid. At the same time, the flue gas is washed with the absorption liquid, and the high-valent nitrogen oxides in the flue gas are washed into the solution, reacting to form a nitrate solution, which is then processed by the product post-treatment system for resource utilization.

7. A wet flue gas denitrification method according to claim 4, characterized in that: The flue gas temperature at the entrance of the packed absorption tower does not exceed 110°C, and the NO concentration in the flue gas is 50-500 mg / m 3 The temperature of the circulating absorption liquid sprayed into the packed absorption tower is 30℃-60℃, and the liquid-gas ratio is 5L / m 3 -20 L / m 3 The mass percentage concentration of the oxidant is 0.01%-20%, and the pH of the absorption liquid is controlled between 3-11.

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