Nitrogen oxide tail gas treatment process

Abstract

The invention relates to the field of waste gas treatment, in particular to a nitrogen oxide tail gas treatment process. According to the nitrogen oxide tail gas treatment process provided by the invention, the concentration of nitrogen oxide in high-concentration nitrogen oxide tail gas generated by metal dissolution and calcination can be reduced to be less than or equal to 100mg / m < 3 >, and up-to-standard emission is realized. According to the process, the nitrogen oxide tail gas absorption efficiency is effectively improved, and resource utilization of waste gas and waste water is achieved; the whole process has reliability, practicability and economical efficiency, and the production cost and the treatment cost are greatly reduced. In addition, the process further comprises the design of recycling the absorption liquid, compared with a process with the absorption liquid being urea, the process has the advantages that the agent input is reduced, nitrogen oxide in the tail gas is recycled in the treatment process, the nitrogen oxide is changed into recyclable nitric acid, resource utilization of waste gas and waste water is achieved, and the process is more environmentally friendly; and the economic benefit is higher.

Description

Technical Field

[0001] The invention relates to the field of waste gas treatment, in particular to a nitrogen oxide tail gas treatment process. Background Art

[0002] In the production process of manganese oxide, nitric acid is generally used to dissolve manganese metal. The dissolution process will produce a large amount of nitrogen monoxide, and a large amount of high-concentration nitrogen dioxide will be produced when manganese nitrate is calcined. The methods for treating nitrogen oxides mainly include catalytic reduction, catalytic decomposition, plasma treatment, biological treatment, staged combustion, adsorption and liquid absorption. At present, liquid absorption is often used to treat nitrogen oxide tail gas, and the treatment device is mostly a urea injection vacuum unit. However, the urea injection vacuum unit has extremely low reaction efficiency, high reagent cost, and it is difficult to reuse the absorption liquid. With the development of the times, a more green and environmentally friendly and economically efficient treatment process is needed to treat high-concentration nitrogen oxide tail gas. Summary of the invention

[0003] In view of this, the technical problem to be solved by the present invention is to provide a nitrogen oxide tail gas treatment process. The nitrogen oxide tail gas treatment process provided by the present invention can effectively improve the nitrogen oxide tail gas absorption efficiency and realize the resource utilization of waste gas and waste water.

[0004] The present invention provides a nitrogen oxide tail gas treatment process, comprising the following steps:

[0005] S1) subjecting the demisted and condensed nitrogen oxide tail gas to a first-stage hydrogen peroxide bubbling absorption for 2s to 3s, and then subjecting the second-stage hydrogen peroxide bubbling absorption for 2s to 3s after an interval of 2s to 5s;

[0006] S2) subjecting the tail gas treated in step S1) to first-stage water jet absorption for 10s to 15s after an interval of 2s to 5s, second-stage water jet absorption for 10s to 15s after an interval of 2s to 5s, and third-stage water jet absorption for 10s to 15s after an interval of 2s to 5s;

[0007] S3) subjecting the tail gas treated in step S2) to a third-stage hydrogen peroxide bubbling absorption for 2s to 3s after an interval of 2s to 5s;

[0008] S4) The tail gas treated in step S3) is subjected to fourth-level water jet absorption for 10s to 15s after an interval of 2s to 5s, fifth-level water jet absorption for 10s to 15s after an interval of 7s to 10s, sixth-level water jet absorption for 10s to 15s after an interval of 12s to 15s, seventh-level water jet absorption for 10s to 15s after an interval of 22s to 25s, and alkali solution spraying for 5s to 10s after an interval of 75s to 90s.

[0009] The nitrogen oxide tail gas treatment process provided by the present invention is specifically aimed at nitrogen oxides (NO x ) gas treatment process, the nitrogen oxide gas includes NO and NO2. In certain embodiments of the present invention, the nitrogen oxide tail gas is the nitrogen oxide tail gas generated by the manganese metal dissolution and manganese nitrate calcination process.

[0010] The present invention first demists and condenses the nitrogen oxide tail gas to obtain the demisted and condensed nitrogen oxide tail gas. In certain embodiments of the present invention, the nitrogen oxide tail gas is demisted and condensed through a demister and a two-stage condenser to reduce the temperature of the nitrogen oxide tail gas to about 30°C, specifically 25°C to 35°C, to obtain the demisted and condensed nitrogen oxide tail gas. The present invention recovers the liquid, metal dust and acid solution entrained in the nitrogen oxide tail gas by demisting and condensing. During the demisting and condensing process, the nitrogen dioxide in the nitrogen oxide tail gas reacts with the condensed droplets to generate nitric acid, which can slightly reduce the concentration of nitrogen oxides in the tail gas, while reducing the content of solution and particulate matter entrained in the tail gas, reducing the loss of reaction materials, and avoiding the materials from entering the bubbling absorption tank, resulting in ineffective decomposition of hydrogen peroxide.

[0011] In certain embodiments of the present invention, the nitrogen oxide tail gas is the nitrogen oxide tail gas of manganese metal dissolution and the nitrogen oxide tail gas generated by the manganese nitrate calcination process; wherein, the manganese metal dissolution is carried out in a manganese metal dissolution kettle, and the nitrogen oxide tail gas flows out from the gas outlet of the dissolution kettle, and the gas outlet of the dissolution kettle is provided with a wire mesh demister, and a two-stage condenser is connected behind the wire mesh demister; the manganese nitrate calcination process is carried out in a calcination furnace, and the nitrogen oxide tail gas flows out from the gas outlet of the calcination furnace, and the gas outlet of the calcination furnace is provided with a swirl blade demister, and a two-stage condenser is connected behind the swirl blade demister.

[0012] After obtaining the demisted and condensed nitrogen oxide tail gas, the demisted and condensed nitrogen oxide tail gas is subjected to first-stage hydrogen peroxide bubbling absorption and second-stage hydrogen peroxide bubbling absorption in sequence. During the two-stage hydrogen peroxide bubbling absorption process, most of the nitrogen oxides in the demisted and condensed nitrogen oxide tail gas are oxidized into nitric acid. The concentration of the hydrogen peroxide absorption liquid used in the first-stage hydrogen peroxide bubbling absorption and the second-stage hydrogen peroxide bubbling absorption of the present invention is independently 35wt% to 50wt%.

[0013] In certain embodiments of the present invention, the demisted and condensed nitrogen oxide tail gas is sequentially passed through a first-stage hydrogen peroxide bubbling absorption tank and a second-stage hydrogen peroxide bubbling absorption tank for the first-stage hydrogen peroxide bubbling absorption and the second-stage hydrogen peroxide bubbling absorption, the first-stage hydrogen peroxide bubbling absorption tank is connected to the gas outlet of the aforementioned condenser, the second-stage hydrogen peroxide bubbling absorption tank is connected to the gas outlet of the second-stage hydrogen peroxide bubbling absorption tank, and hydrogen peroxide absorption liquid is provided in the first-stage hydrogen peroxide bubbling absorption tank and the second-stage hydrogen peroxide bubbling absorption tank; the liquid level height of the hydrogen peroxide absorption liquid in the hydrogen peroxide bubbling absorption tank of each stage is independently 30% to 40% of the total height of the hydrogen peroxide bubbling absorption tank of each stage.

[0014] In the present invention, after the demisting and condensing nitrogen oxide tail gas is subjected to the first-stage hydrogen peroxide bubbling absorption and the second-stage hydrogen peroxide bubbling absorption in sequence, the tail gas treated in step S1) is subjected to the first-stage water jet absorption, the second-stage water jet absorption and the third-stage water jet absorption in sequence. During the three-stage water jet absorption process, nitrogen dioxide and pure water react to generate nitric acid and nitrogen monoxide. The water absorption liquid used in the first-stage water jet absorption, the second-stage water jet absorption and the third-stage water jet absorption of the present invention are all pure water absorption liquids.

[0015] In certain embodiments of the present invention, the tail gas treated in step S1) is subjected to the first-stage water jet absorption, the second-stage water jet absorption and the third-stage water jet absorption in sequence by a first-stage water jet tower, a second-stage water jet tower and a third-stage water jet tower, the first-stage water jet tower is connected to the gas outlet of the second-stage hydrogen peroxide bubbling absorption tank, the second-stage water jet tower is connected to the gas outlet of the first-stage water jet tower, and the third-stage water jet tower is connected to the gas outlet of the second-stage water jet tower; the liquid level height of the water absorption liquid in the medicine box of each stage of the water jet tower is independently 70% to 80% of the total height of the medicine box of each stage of the water jet tower.

[0016] The present invention sequentially performs first-stage water jet absorption, second-stage water jet absorption and third-stage water jet absorption on the tail gas treated in step S1), and then performs third-stage hydrogen peroxide bubbling absorption on the tail gas treated in step S2), and performs oxidation reaction with hydrogen peroxide again. The concentration of the hydrogen peroxide absorption liquid used in the third-stage hydrogen peroxide bubbling absorption of the present invention is 35wt% to 50wt%.

[0017] In certain embodiments of the present invention, the tail gas treated in step S2) is subjected to third-stage hydrogen peroxide bubbling absorption in a third-stage hydrogen peroxide bubbling absorption tank, and the third-stage hydrogen peroxide bubbling absorption tank is connected to the gas outlet of the third-stage water jet tower; the liquid level of the hydrogen peroxide absorption liquid in the third-stage hydrogen peroxide bubbling absorption tank is 30% to 40% of the total height of the third-stage hydrogen peroxide bubbling absorption tank.

[0018] After the tail gas treated in step S2) is subjected to the third-stage hydrogen peroxide bubbling absorption, the tail gas treated in step S3) is subjected to the fourth-stage water jet absorption, the fifth-stage water jet absorption, the sixth-stage water jet absorption and the seventh-stage water jet absorption in sequence, and then subjected to water absorption again. The water absorption liquid used in the fourth-stage water jet absorption, the fifth-stage water jet absorption, the sixth-stage water jet absorption and the seventh-stage water jet absorption of the present invention is all pure water absorption liquid.

[0019] In certain embodiments of the present invention, the tail gas treated in step S3) is sequentially subjected to the fourth-stage water jet absorption, the fifth-stage water jet absorption, the sixth-stage water jet absorption and the seventh-stage water jet absorption by a fourth-stage water jet tower, a fifth-stage water jet tower, a sixth-stage water jet tower and a seventh-stage water jet tower, the fourth-stage water jet unit is connected to the gas outlet of the third-stage hydrogen peroxide bubbling absorption tank, the fifth-stage water jet tower is connected to the gas outlet of the fourth-stage water jet tower, the sixth-stage water jet tower is connected to the gas outlet of the fifth-stage water jet tower, and the seventh-stage water jet tower is connected to the gas outlet of the sixth-stage water jet tower; the liquid level height of the water absorption liquid in the medicine box of each stage of the water jet tower is independently 70% to 80% of the total height of the medicine box of each stage of the water jet tower.

[0020] The present invention sequentially performs the fourth stage water jet absorption, the fifth stage water jet absorption, the sixth stage water jet absorption and the seventh stage water jet absorption, and then performs alkali spraying. After the tail gas treatment meets the standards, it is discharged through a chimney via a fan. The concentration of the alkali solution used in the present invention is 10wt% to 20wt%. The alkali solution described in the present invention is mainly one or more of sodium hydroxide, dilute ammonia water and soda ash. In certain embodiments of the present invention, the alkali spraying is performed in an alkali spray tower, and the alkali spray tower is connected to the gas outlet of the seventh stage water jet tower.

[0021] The present invention sequentially processes the nitrogen oxide tail gas after demisting and condensation through two-stage hydrogen peroxide bubbling absorption, three-stage water jet absorption, one-stage hydrogen peroxide bubbling absorption and four-stage water jet absorption, and finally completes the treatment of the nitrogen oxide tail gas through alkali solution spraying. Considering that in the treatment process of the nitrogen oxide tail gas, as NO reacts with O2, the NO concentration gradually decreases, the reaction rate gradually decreases, and the time for NO oxidation to form NO2 gradually increases, after calculating that NO is lower than a certain value, the time required for the oxidation rate is very long. The present invention solves the problem of excessive NO concentration in the process of nitrogen oxide tail gas treatment, which is gradually difficult to treat, by extending the residence time of the nitrogen oxide tail gas in the hydrogen peroxide bubbling absorption and water jet absorption at each stage.

[0022] In certain embodiments of the present invention, the residence time of the nitrogen oxide tail gas passing through is controlled by controlling the adjacent spacing between each absorption device and the adjacent next-stage absorption device, increasing the distance between towers, and increasing the length and diameter of several pipelines. Specifically, the spacing between the first-stage hydrogen peroxide bubbling absorption tank and the second-stage hydrogen peroxide bubbling absorption tank, the spacing between the second-stage hydrogen peroxide bubbling absorption tank and the first-stage water jet tower, the spacing between the first-stage water jet tower and the second-stage water jet tower, the spacing between the second-stage water jet tower and the third-stage water jet tower, the spacing between the third-stage water jet tower and the third-stage hydrogen peroxide bubbling absorption tank, and the spacing between the third-stage hydrogen peroxide bubbling absorption tank and the fourth-stage water jet tower are all independently 1. 0m~1.2m, preferably 1m; the distance between the fourth-level water jet tower and the fifth-level water jet tower is 1.0m~3.0m, preferably 3m; the distance between the fifth-level water jet tower and the sixth-level water jet tower is 3.0m~6.0m, preferably 5m; the distance between the sixth-level water jet tower and the seventh-level water jet tower is 7.0m~9.0m, preferably 8m; the distance between the seventh-level water jet tower and the alkali solution spray tower is 50m~70m, preferably 60m.

[0023] In the present invention, when performing the hydrogen peroxide bubbling absorption at each level and the water jet absorption at each level, the concentration of the inlet and outlet nitrogen oxide tail gas and the concentration of the absorption liquid are monitored in real time, the system operation status is timely understood, and the absorption liquid is replaced in time. In certain embodiments of the present invention, the hydrogen peroxide bubbling absorption tank and the water jet tower at each level are also provided with a pressure gauge, a thermometer and a density meter, so that the physical parameters and operation status of the tail gas treatment system and the density of the absorption liquid can be understood in real time.

[0024] The temperature of the hydrogen peroxide absorption liquid used in the first-stage hydrogen peroxide bubbling absorption, the second-stage hydrogen peroxide bubbling absorption and the third-stage hydrogen peroxide bubbling absorption of the present invention is independently 20° C. to 35° C.; the temperature of the water absorption liquid used in the first-stage water jet absorption, the second-stage water jet absorption, the third-stage water jet absorption, the fourth-stage water jet absorption, the fifth-stage water jet absorption, the sixth-stage water jet absorption and the seventh-stage water jet absorption is independently 20° C. to 35° C.

[0025] In certain embodiments of the present invention, cooling units and temperature control systems are provided on the condenser, the hydrogen peroxide bubbling absorption tanks at various levels, and the water jet towers at various levels, which can automatically change the flow rate, water temperature and other parameters of the cooling water according to the temperature of the condenser, the hydrogen peroxide bubbling absorption tank and the water jet tower, stabilize the ambient temperature of the system, and improve the stability of the system; the hydrogen peroxide bubbling absorption tanks at various levels and the water jet towers at various levels are provided with cooling coils; the cooling unit is combined with the temperature control system to control the hydrogen peroxide absorption liquid in the hydrogen peroxide bubbling absorption tanks at various levels and the water absorption liquid in the medicine box of the water jet towers at various levels through the cooling coils to maintain the temperature of (25-30) ± 5 ° C. The cooling system reduces the ambient temperature of hydrogen peroxide, avoids the ineffective loss of hydrogen peroxide caused by the heat release of hydrogen peroxide reaction and the heat release of self-decomposition, and also increases the solubility of nitrogen oxides in hydrogen peroxide, which can significantly improve the tail gas removal efficiency and reduce the system operation cost.

[0026] In some embodiments of the present invention, each level of the hydrogen peroxide bubbling absorption tank is also provided with an aeration system, wherein the aeration system is a microporous aeration disk, the aperture of the aeration disk near the center area is 50 μm to 100 μm, and the aperture of the aeration disk far from the center area is 100 μm to 200 μm.

[0027] In other embodiments of the present invention, each level of the water jet tower is also provided with a balancing air duct to balance the pressure of the water jet towers at each level and avoid sudden changes in pressure, which causes the absorption liquid of the previous water jet tower to be sucked into the next water jet tower by negative pressure, thereby keeping the liquid level of the water jet towers at each level stable and avoiding mutual influence of the absorption liquid between the water jet towers at each level.

[0028] During the whole process of the nitrogen oxide tail gas treatment process of the present invention, if the NO x The concentration continues to rise above 200 mg / m 3 , then during step S2) of the first-stage hydrogen peroxide bubbling absorption, O2 is continuously introduced; the molar ratio of the introduced O2 to the total NO in the nitrogen oxide tail gas after demisting and condensation is 2:1. The present invention can deal with the problem of hydrogen peroxide absorption liquid becoming ineffective due to loss during production by continuously introducing O2 during the first-stage hydrogen peroxide bubbling absorption in step S2). When the above-mentioned emergency measures are used to complete the production of the current batch, the above-mentioned emergency measures need to be used to oxidize the next batch at the beginning. If NO x The NO of the nitrogen oxide tail gas increases significantly again. x The concentration continued to rise again and exceeded 200 mg / m 3In the event of a problem, production is stopped and the hydrogen peroxide absorption liquid in the first-stage hydrogen peroxide bubbling tank and the second-stage hydrogen peroxide bubbling tank is replaced. The above emergency measures can continue to increase the acidity of the acid solution generated by treating the tail gas in the first-stage hydrogen peroxide bubbling tank and the second-stage hydrogen peroxide bubbling tank, reduce the amount of wastewater generated, and increase the amount of acid solution reused. In certain embodiments of the present invention, the hydrogen peroxide bubbling absorption tank and the water jet tower at each stage are provided with gas and liquid monitoring ports.

[0029] The hydrogen peroxide absorption liquid used in the hydrogen peroxide bubbling absorption of each level of the present invention circulates, which can improve the hydrogen peroxide and NO x The contact efficiency can be improved, and the hydrogen peroxide can be gently decomposed to increase the oxygen content of the system, thereby improving the absorption and removal efficiency of NO in each stage of the water jet tower. In certain embodiments of the present invention, by providing a connected pump and pipeline between the first stage hydrogen peroxide bubbling absorption tank, the second stage hydrogen peroxide bubbling absorption tank and the third stage hydrogen peroxide bubbling absorption tank, the hydrogen peroxide absorption liquid in each stage of the hydrogen peroxide bubbling absorption tank can be circulated.

[0030] When the acidity of the hydrogen peroxide absorption liquid used in the first-stage hydrogen peroxide bubbling absorption of the present invention is 7.5 mol / L to 8.5 mol / L, preferably 8 mol / L, the hydrogen peroxide absorption liquid used in the first-stage hydrogen peroxide bubbling absorption is removed, the hydrogen peroxide absorption liquid used in the second-stage hydrogen peroxide bubbling absorption is used for the first-stage hydrogen peroxide bubbling absorption, the hydrogen peroxide absorption liquid used in the third-stage hydrogen peroxide bubbling absorption is used for the second-stage hydrogen peroxide bubbling absorption, and new hydrogen peroxide absorption liquid is used for the third-stage hydrogen peroxide bubbling absorption. When the acidity of the water absorption liquid used for the first-level water jet absorption is 5.5mol / L to 6.5mol / L, preferably 6mol / L, the water absorption liquid used for the first-level water jet absorption is removed, the water absorption liquid used for the second-level water jet absorption is used for the first-level water jet absorption, the water absorption liquid used for the third-level water jet absorption is used for the second-level water jet absorption, the water absorption liquid used for the fourth-level water jet absorption is used for the third-level water jet absorption, the water absorption liquid used for the fifth-level water jet absorption is used for the fourth-level water jet absorption, the water absorption liquid used for the sixth-level water jet absorption is used for the fifth-level water jet absorption, the water absorption liquid used for the seventh-level water jet absorption is used for the sixth-level water jet absorption, and new water absorption liquid is used for the seventh-level water jet absorption.

[0031] In certain embodiments of the present invention, when the acidity of the hydrogen peroxide absorption liquid used in the first-stage hydrogen peroxide bubbling absorption is 7.5 mol / L to 8.5 mol / L, preferably 8 mol / L, the hydrogen peroxide absorption liquid in the first-stage hydrogen peroxide bubbling absorption tank is removed to the acid preparation tank and then returned to the dissolution kettle for use, the hydrogen peroxide absorption liquid in the second-stage hydrogen peroxide bubbling absorption tank is transferred to the first-stage hydrogen peroxide bubbling absorption tank, the hydrogen peroxide absorption liquid in the third-stage hydrogen peroxide bubbling absorption tank is transferred to the second-stage hydrogen peroxide bubbling absorption tank, and the third-stage hydrogen peroxide bubbling absorption tank is supplemented with new hydrogen peroxide absorption liquid. When the acidity of the water absorption liquid used for the first-stage water jet absorption is 5.5mol / L to 6.5mol / L, preferably 6mol / L, the water absorption liquid in the medicine box of the first-stage water jet unit is removed to the acid preparation tank and then returned to the dissolution kettle for use, the water absorption liquid in the medicine box of the second-stage water jet tower is transferred to the medicine box of the first-stage water jet tower, the water absorption liquid in the medicine box of the third-stage water jet tower is transferred to the medicine box of the second-stage water jet tower, and the water absorption liquid in the medicine box of the fourth-stage water jet tower is transferred to the medicine box of the fourth-stage water jet tower. The water absorption liquid in the medicine box of the first-stage water jet tower is transferred to the medicine box of the third-stage water jet tower, the water absorption liquid in the medicine box of the fifth-stage water jet tower is transferred to the medicine box of the fourth-stage water jet tower, the water absorption liquid in the medicine box of the sixth-stage water jet tower is transferred to the medicine box of the fifth-stage water jet tower, the water absorption liquid in the medicine box of the seventh-stage water jet tower is transferred to the medicine box of the sixth-stage water jet tower, and new water absorption liquid is added to the medicine box of the seventh-stage water jet tower.

[0032] In the process of nitrogen oxide absorption, the concentration of the process of the present invention is gradually reduced. Pumping the next-level absorption liquid to the upper level is conducive to increasing the concentration of nitric acid in the absorption liquid, accelerating the reuse of nitric acid, and improving the economy of the entire production line. As a part of the nitrogen oxide tail gas treatment system, the design also plays a role in recovering the absorption liquid, converting most of the nitrogen dioxide into nitric acid, with good treatment effect. The concentration of the generated nitric acid can reach 40% to 50%, which can be fully reused on the production line, with high economic benefits and no secondary pollution. In addition, because the design is equipped with a unique pipeline and centrifugal pump that pumps the next-level tank solution to the upper-level tank, it is only necessary to detect the absorption liquid of the first-level hydrogen peroxide bubbling absorption tank and the first-level water jet tower, discharge nitric acid in the first-level bubbling absorption tank and the first-level water jet tower, and add new absorption liquid to the third-level bubbling absorption tank and the seventh-level water jet tower, which reduces the number of detections, facilitates the automation, standardization, and standardized management of production, and reduces management costs, detection costs, and personnel input.

[0033] In certain embodiments of the present invention, an absorption liquid circulation pipeline is provided between the first-stage hydrogen peroxide bubbling absorption tank, the second-stage hydrogen peroxide bubbling absorption tank and the third-stage hydrogen peroxide bubbling absorption tank; a centrifugal pump is provided on the absorption liquid circulation pipeline, and the centrifugal pump pumps the absorption liquid in the rear-stage hydrogen peroxide bubbling absorption tank to the front-stage hydrogen peroxide bubbling absorption tank. Specifically, an absorption liquid circulation pipeline is provided between the first-stage hydrogen peroxide bubbling absorption tank and the second-stage hydrogen peroxide bubbling absorption tank, and a centrifugal pump is provided on the absorption liquid circulation pipeline, and the centrifugal pump pumps the absorption liquid of the second-stage hydrogen peroxide bubbling absorption tank to the first-stage hydrogen peroxide bubbling absorption tank; an absorption liquid circulation pipeline is provided between the second-stage hydrogen peroxide bubbling absorption tank and the third-stage hydrogen peroxide bubbling absorption tank, and a centrifugal pump is provided on the absorption liquid circulation pipeline, and the centrifugal pump pumps the absorption liquid of the third-stage hydrogen peroxide bubbling absorption tank to the second-stage hydrogen peroxide bubbling absorption tank.

[0034] In certain embodiments of the present invention, an absorption liquid circulation pipeline is arranged between the first-stage water jet tower, the second-stage water jet tower, the third-stage water jet tower, the fourth-stage water jet tower, the fifth-stage water jet tower, the sixth-stage water jet tower and the seventh-stage water jet tower; a centrifugal pump is arranged on the absorption liquid circulation pipeline, and the centrifugal pump pumps the absorption liquid of the rear-stage water jet tower to the front-stage water jet tower. Specifically, an absorption liquid circulation pipeline is provided between the first-stage water jet tower and the second-stage water jet tower, and a centrifugal pump is provided on the absorption liquid circulation pipeline, and the centrifugal pump pumps the absorption liquid of the second-stage water jet tower to the first-stage water jet tower; an absorption liquid circulation pipeline is provided between the second-stage water jet tower and the third-stage water jet tower, and a centrifugal pump is provided on the absorption liquid circulation pipeline, and the centrifugal pump pumps the absorption liquid of the third-stage water jet tower to the second-stage water jet tower; an absorption liquid circulation pipeline is provided between the third-stage water jet tower and the fourth-stage water jet tower, and a centrifugal pump is provided on the absorption liquid circulation pipeline, and the centrifugal pump pumps the absorption liquid of the fourth-stage water jet tower to the third-stage water jet tower. flow tower; an absorption liquid circulation pipeline is arranged between the fourth-level water jet tower and the fifth-level water jet tower, and a centrifugal pump is arranged on the absorption liquid circulation pipeline, and the centrifugal pump pumps the absorption liquid of the fifth-level water jet tower to the fourth-level water jet tower; an absorption liquid circulation pipeline is arranged between the fifth-level water jet tower and the sixth-level water jet tower, and a centrifugal pump is arranged on the absorption liquid circulation pipeline, and the centrifugal pump pumps the absorption liquid of the sixth-level water jet tower to the fifth-level water jet tower; an absorption liquid circulation pipeline is arranged between the sixth-level water jet tower and the seventh-level water jet tower, and a centrifugal pump is arranged on the absorption liquid circulation pipeline, and the centrifugal pump pumps the absorption liquid of the seventh-level water jet tower to the sixth-level water jet tower.

[0035] The nitrogen oxide tail gas treatment process provided by the present invention can reduce the concentration of nitrogen oxides in the tail gas to ≤100 mg / m3 after the high-concentration nitrogen oxides (15.78 g / s, 105918 mg / m3, mainly nitrogen dioxide) tail gas generated by metal dissolution and calcination is subjected to demisting condensation → two-stage hydrogen peroxide oxidation → three-stage pure water absorption → one-stage hydrogen peroxide oxidation → four-stage pure water absorption → alkali solution spraying treatment, thereby achieving standard emission. The process described in the present invention effectively improves the nitrogen oxide tail gas absorption efficiency and realizes the resource utilization of waste gas and waste water; the entire process is reliable, practical, and economical, and greatly reduces production costs and processing costs. In addition, the process described in the present invention also includes a design for recovering the absorption liquid. Compared with the process in which the absorption liquid is urea, this process not only reduces the input of reagents, but also recovers the nitrogen oxides in the tail gas during the treatment process, so that the nitrogen oxides are converted into recyclable nitric acid, realizing the resource utilization of waste gas and waste water, being greener and more environmentally friendly, and having higher economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 A schematic diagram of a treatment system used in the treatment process of the present invention;

[0037] Figure 2 The schematic diagram of the operation flow of the processing system used in the processing process of the present invention is shown in FIG. DETAILED DESCRIPTION

[0038] The present invention discloses a process for treating nitrogen oxide tail gas. Those skilled in the art can refer to the content of this article and appropriately improve the process parameters to achieve it. It is particularly important to point out that all similar substitutions and modifications are obvious to those skilled in the art and are deemed to be included in the present invention. The method and application of the present invention have been described through preferred embodiments, and relevant personnel can obviously modify or appropriately change and combine the method and application of this article without departing from the content, spirit and scope of the present invention to implement and apply the technology of the present invention.

[0039] like Figure 1 As shown, Figure 1 The following is a schematic diagram of the operation flow of the treatment system used in the treatment process of the present invention. Figure 2 As shown, Figure 2 The schematic diagram of the treatment system used in the treatment process of the present invention includes: a demister, a two-stage condenser, a two-stage series hydrogen peroxide bubbling absorption tank, a three-stage series water jet tower, a first-stage hydrogen peroxide bubbling absorption tank, a fourth-stage series water jet tower, an alkali spray tower, a fan and a chimney. The distance between the 1st hydrogen peroxide bubbling absorption tank and the 2nd hydrogen peroxide bubbling absorption tank is 1m, the time for the nitrogen oxide tail gas to be absorbed in the tank bodies of the 1st hydrogen peroxide bubbling absorption tank and the 2nd hydrogen peroxide bubbling absorption tank is 2.5s respectively, and the time interval from the 1st hydrogen peroxide bubbling absorption tank to the 2nd hydrogen peroxide bubbling absorption tank is 3.5s;

[0040] The distance between the 2 hydrogen peroxide bubbling absorption tank and the 1 water jet tower is 1m, the time interval for the nitrogen oxide tail gas to flow from the 2 hydrogen peroxide bubbling absorption tank to the 1 water jet tower is 3.5s, and the absorption time in the tank body of the 1 water jet tower is 17.5s;

[0041] The distance between the 1st water jet tower and the 2nd water jet tower is 1m, the time interval for the nitrogen oxide tail gas to flow from the 1st water jet tower to the 2nd water jet tower is 2s, and the absorption time in the tank of the 2nd water jet tower is 17.5s;

[0042] The distance between the 2nd water jet tower and the 3rd water jet tower is 1m, the time interval for the nitrogen oxide tail gas to flow from the 2nd water jet tower to the 3rd water jet tower is 2s, and the absorption time in the tank of the 3rd water jet tower is 17.5s;

[0043] The distance between the 3 water jet towers and the 3 hydrogen peroxide bubbling absorption tanks is 1m, the time interval for the nitrogen oxide tail gas to flow from the 3 water jet towers to the 3 hydrogen peroxide bubbling absorption tanks is 2s, and the absorption time in the tank body of the 3 hydrogen peroxide bubbling absorption tanks is 2.5s;

[0044] The distance between the 3 hydrogen peroxide bubbling absorption tank and the 4 water jet tower is 1m, the time interval for the nitrogen oxide tail gas to flow from the 3 hydrogen peroxide bubbling absorption tank to the 4 water jet tower is 3.5s, and the absorption time in the tank body of the 4 water jet tower is 17.5s;

[0045] The distance between the 4th water jet tower and the 5th water jet tower is 3m, the time interval for the nitrogen oxide tail gas to flow from the 4th water jet tower to the 5th water jet tower is 8s, and the absorption time in the tank of the 5th water jet tower is 17.5s;

[0046] The distance between the 5th water jet tower and the 6th water jet tower is 5m, the time interval for the nitrogen oxide tail gas to flow from the 5th water jet tower to the 6th water jet tower is 14s, and the absorption time in the tank of the 6th water jet tower is 17.5s;

[0047] The distance between the 6th water jet tower and the 7th water jet tower is 8m, the time interval for the nitrogen oxide tail gas to flow from the 6th water jet tower to the 7th water jet tower is 22s, and the absorption time in the tank of the 7th water jet tower is 17.5s;

[0048] The distance between the 7 water jet tower and the alkali liquid spray tower is 60m, the time interval for the nitrogen oxide tail gas to flow from the 7 water jet tower to the alkali liquid spray tower is 75s, and the spraying time in the alkali liquid spray tower is 8.68s.

[0049] The present invention will be further described below in conjunction with embodiments:

[0050] Example 1

[0051] This embodiment discloses a process for treating nitrogen oxide tail gas and recovering absorption liquid. The nitrogen oxide tail gas to be treated is mainly NO generated when manganese metal is dissolved, the amount of NO is 5.97 g / s, and the reaction equation is: 3Mn+8HNO3=3Mn(NO3)2+2NO+4H2O; NO2 is generated when manganese nitrate is calcined, the amount of NO2 is 9.81 g / s, and the reaction equation is: Mn(NO3)2=MnO2+2NO2; NO x The total amount is 15.78g / s, the air volume is 500m3 / h, NO x The content is 105918mg / m3, NO x The content has a peak value. The specific tail gas treatment and absorption liquid recovery process includes the following steps:

[0052] (1) The nitrogen oxide tail gas from the manganese nitrate reactor first passes through a wire mesh demister and a plate heat exchanger, and the nitrogen oxide tail gas from the calcining furnace first passes through a cyclone vane demister and a plate heat exchanger, and the entrained liquid, metal dust and acid solution are recovered and returned to the production kettle. The tail gas temperature is 30°C after cooling;

[0053] (2) The nitrogen oxide tail gas enters a two-stage hydrogen peroxide bubbling absorption tank after step (1) to react with hydrogen peroxide. The hydrogen peroxide concentration in the hydrogen peroxide bubbling absorption tank is 50wt%, the liquid level is 30%, and the ambient temperature is 30°C. Most of the nitrogen oxides in the tail gas are oxidized into nitric acid. The reaction equation is: 2NO+3H2O2=2HNO3+2H2O, 2NO2+H2O2=2HNO3;

[0054] (3) passing the tail gas treated in step (2) into a three-stage pure water jet tower for pure water jet absorption, the liquid level height of the water jet tower medicine box is 80%, the ambient temperature is 30° C., nitrogen dioxide and pure water react to generate nitric acid and nitric oxide, and the reaction equation is: 4NO+3O2+2H2O=4HNO3, 3NO2+H2O=2HNO3+NO, NO2+2H2O+O2=4HNO3;

[0055] (4) passing the tail gas treated in step (3) into a primary hydrogen peroxide bubbling absorption tank, wherein the hydrogen peroxide concentration in the hydrogen peroxide bubbling absorption tank is 50 wt %, the liquid level is 30%, and the ambient temperature is 30° C., and performing an oxidation reaction with the hydrogen peroxide again;

[0056] (5) passing the tail gas treated in step (4) into a four-stage water jet tower for pure water jet absorption, the liquid level height of the water jet tower medicine box is 80%, the ambient temperature is 30° C., and pure water absorption is performed again;

[0057] (6) passing the tail gas treated in step (5) into an alkali solution spray tower, wherein the alkali solution concentration in the spray tower is 20 wt% of sodium hydroxide, and the residual nitric oxide and nitrogen dioxide in the residual tail gas react with oxygen in the air and the sodium hydroxide absorption liquid to generate sodium nitrate and sodium nitrite, and the reaction equation is: 2NO2+2NaOH=NaNO3+NaNO2+H2O, 4NO+3O2+4NaOH=4NaNO3+2H2O;

[0058] (7) The exhaust gas that meets the standards after being treated in step (6) is discharged through a chimney via a fan.

[0059] In this embodiment, after the nitrogen oxide tail gas is treated, NO x The content is ≤100mg / m3, achieving standard emission. The specific data are shown in Table 1:

[0060] Table 1

[0061]

[0062]

[0063] After 4 batches of nitrogen oxide tail gas treatment were carried out in this embodiment, the hydrogen peroxide concentration of the 1 hydrogen peroxide bubbling absorption tank was reduced from 50% to 1%, and the nitric acid concentration was 42wt%, and the hydrogen peroxide concentration of the 2 hydrogen peroxide bubbling absorption tank was reduced from 50% to 35%, and the nitric acid concentration was 24wt%. The absorption liquid of the 1 hydrogen peroxide bubbling absorption tank was released from the bottom valve and pumped to the acid preparation tank A, and returned to the dissolving kettle in the form of production material after acid preparation, and the absorption liquid of the 2 hydrogen peroxide bubbling absorption tank was pumped into the 1 hydrogen peroxide bubbling absorption tank, and the absorption liquid of the 3 hydrogen peroxide bubbling absorption tank was pumped into the 2 hydrogen peroxide bubbling absorption tank, and new absorption liquid was added to the 3 hydrogen peroxide bubbling absorption tank, which can accelerate the increase of the nitric acid concentration of the hydrogen peroxide bubbling absorption tank, and the efficiency is improved by about 15-20%.

[0064] After 10 batches of nitrogen oxide tail gas treatment were performed in this embodiment, the nitric acid concentration of the 1st water jet tower was 40wt%, the nitric acid concentration of the 2nd water jet tower was 33wt%, and the nitric acid concentration of the 3rd water jet tower was 21wt%. The absorption liquid of the 1st water jet tower was discharged from the bottom valve and pumped to the acid preparation tank B. After acid preparation, it was returned to the dissolution kettle in the form of production materials for use. The absorption liquid of the 2nd water jet tower was pumped into the 1st water jet tower, and the absorption liquid of the 3rd water jet tower was pumped into the 2nd water jet tower. By analogy, the absorption liquid of all the next-level water jet towers was pumped into the water jet tower of the previous level, and new pure water was re-pumped into the 7th water jet tower as the absorption liquid. This operation can speed up the nitric acid concentration of all water jet towers and improve the efficiency by about 20-30%.

[0065] The above-mentioned treated waste gas meets the national emission standards and is drawn to the chimney by the centrifugal fan. The above is only a preferred specific implementation of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field within the technical scope disclosed by the present invention, according to the technical solution and its inventive concept of the present invention, shall be covered within the protection scope of the present invention.

Claims

1. A nitrogen oxide tail gas treatment process, characterized in that: The following steps are involved: S1) subjecting the demisted and condensed nitrogen oxide tail gas to a first-stage hydrogen peroxide bubbling absorption for 2s to 3s, and then subjecting the second-stage hydrogen peroxide bubbling absorption for 2s to 3s after an interval of 2s to 5s; S2) subjecting the tail gas treated in step S1) to first-stage water jet absorption for 10s to 15s after an interval of 2s to 5s, second-stage water jet absorption for 10s to 15s after an interval of 2s to 5s, and third-stage water jet absorption for 10s to 15s after an interval of 2s to 5s; S3) subjecting the tail gas treated in step S2) to a third-stage hydrogen peroxide bubbling absorption for 2s to 3s after an interval of 2s to 5s; S4) The tail gas treated in step S3) is subjected to fourth-stage water jet absorption for 10s to 15s after an interval of 2s to 5s, fifth-stage water jet absorption for 10s to 15s after an interval of 7s to 10s, sixth-stage water jet absorption for 10s to 15s after an interval of 12s to 15s, seventh-stage water jet absorption for 10s to 15s after an interval of 22s to 25s, and alkali solution spraying in a spray tower for 5s to 10s after an interval of 75s to 90s.

2. The nitrogen oxide tail gas treatment process according to claim 1, characterized in that: In step S1) and step S3), the concentration of the hydrogen peroxide absorption liquid used in the first stage hydrogen peroxide bubbling absorption, the second stage hydrogen peroxide bubbling absorption and the third stage hydrogen peroxide bubbling absorption is independently 35wt% to 50wt%; In step S2) and step S4), the water absorption liquid used in the first-stage water jet absorption, the second-stage water jet absorption, the third-stage water jet absorption, the fourth-stage water jet absorption, the fifth-stage water jet absorption, the sixth-stage water jet absorption and the seventh jet absorption are all pure water absorption liquid.

3. The nitrogen oxide tail gas treatment process according to claim 1, characterized in that: The temperature of the nitrogen oxide tail gas after demisting and condensation in step S1) is 25°C to 35°C.

4. The nitrogen oxide tail gas treatment process according to claim 1, characterized in that: In step S1) and step S3), the temperature of the hydrogen peroxide absorption liquid used in the first stage hydrogen peroxide bubbling absorption, the second stage hydrogen peroxide bubbling absorption and the third stage hydrogen peroxide bubbling absorption is independently 20°C to 35°C; In step S2) and step S4), the temperature of the water absorption liquid used in the first water jet absorption, the second water jet absorption, the third water jet absorption, the fourth water jet absorption, the fifth water jet absorption, the sixth water jet absorption and the seventh water jet absorption is independently 20°C to 35°C.

5. The nitrogen oxide tail gas treatment process according to claim 1, characterized in that: In step S1) and step S3), the hydrogen peroxide absorption liquid used in each stage of the hydrogen peroxide bubbling absorption circulates.

6. The nitrogen oxide tail gas treatment process according to claim 1, characterized in that: In step S1) and step S3), the first stage hydrogen peroxide bubbling absorption, the second stage hydrogen peroxide bubbling absorption and the third stage hydrogen peroxide bubbling absorption are respectively carried out in the first stage hydrogen peroxide bubbling absorption tank, the second stage hydrogen peroxide bubbling absorption tank and the third stage hydrogen peroxide bubbling absorption tank, and the liquid level height of the hydrogen peroxide absorption liquid in the hydrogen peroxide bubbling absorption tank of each stage is independently 30% to 40% of the total height of the hydrogen peroxide bubbling absorption tank of each stage; In step S2) and step S4), the first-level water jet absorption, the second-level water jet absorption, the third-level water jet absorption, the fourth-level water jet absorption, the fifth-level water jet absorption, the sixth-level water jet absorption and the seventh-level water jet absorption are respectively carried out by a first-level water jet tower, a second-level water jet tower, a third-level water jet tower, a fourth-level water jet tower, a fifth-level water jet tower, a sixth-level water jet tower and a seventh-level water jet tower, and the liquid level height of the water absorption liquid in the medicine box of the water jet tower at each level is independently 70% to 80% of the total height of the medicine box of the water jet tower at each level.

7. The nitrogen oxide tail gas treatment process according to claim 1, characterized in that: The concentration of the alkali solution used for the alkali solution spraying in step S4) is 10wt% to 20wt%.

8. The nitrogen oxide tail gas treatment process according to claim 1, characterized in that: During the whole process of the nitrogen oxide tail gas treatment process, if the NO x The concentration continues to rise above 200 mg / m 3 , then during step S2) the first-stage hydrogen peroxide bubbling absorption is performed, O2 is continuously introduced.

9. The nitrogen oxide tail gas treatment process according to claim 1, characterized in that: When the acidity of the hydrogen peroxide absorption liquid used in the first stage of hydrogen peroxide bubbling absorption is 7.5 mol / L to 8.5 mol / L, the hydrogen peroxide absorption liquid used in the first stage of hydrogen peroxide bubbling absorption is removed, the hydrogen peroxide absorption liquid used in the second stage of hydrogen peroxide bubbling absorption is used for the first stage of hydrogen peroxide bubbling absorption, the hydrogen peroxide absorption liquid used in the third stage of hydrogen peroxide bubbling absorption is used for the second stage of hydrogen peroxide bubbling absorption, and new hydrogen peroxide absorption liquid is used for the third stage of hydrogen peroxide bubbling absorption; When the acidity of the water absorption liquid used for the first-level water jet absorption is 5.5mol / L~6.5mol / L, the water absorption liquid used for the first-level water jet absorption is removed, the water absorption liquid used for the second-level water jet absorption is used for the first-level water jet absorption, the water absorption liquid used for the third-level water jet absorption is used for the second-level water jet absorption, the water absorption liquid used for the fourth-level water jet absorption is used for the third-level water jet absorption, the water absorption liquid used for the fifth-level water jet absorption is used for the fourth-level water jet absorption, the water absorption liquid used for the sixth-level water jet absorption is used for the fifth-level water jet absorption, the water absorption liquid used for the seventh-level water jet absorption is used for the sixth-level water jet absorption, and new water absorption liquid is used for the seventh-level water jet absorption.

10. The nitrogen oxide tail gas treatment process according to claim 1, characterized in that: The nitrogen oxide tail gas is the nitrogen oxide tail gas generated by the manganese metal dissolution and manganese nitrate calcination process.

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