Liquid non-amino reducing agent as well as preparation method and application thereof

Abstract

The invention provides a liquid non-amino reducing agent as well as a preparation method and application thereof. Belongs to the technical field of industrial flue gas SNCR denitration. The liquid non-amino reducing agent is prepared from the following components in percentage by mass: 15 to 17 percent of industrial vegetable oil, 68 to 71 percent of methanol, 2.5 to 4.5 percent of ethyl acetate, 2 to 3 percent of pyridine and 6 to 10 percent of triazine compounds. When the liquid non-amino reducing agent is applied to industrial flue gas denitration, NOx in flue gas can be effectively reduced into nitrogen, the concentration of NOx can be lower than 50 mg / m < 3 >, and the denitration efficiency reaches 85% or above; the problems of ammonium salt scale deposition, equipment corrosion and the like caused by ammonia escape can also be avoided; the method is safe, reliable and low in cost, does not cause secondary pollution to the environment, and has very high practicability.

Description

Technical Field

[0001] The invention belongs to the technical field of SNCR denitration of industrial flue gas, and specifically relates to a liquid non-amino reducing agent and a preparation method and application thereof. Background Art

[0002] As the country and the industry pay more and more attention to air pollution, the national and local governments have successively formulated new air pollutant emission control requirements and strengthened the strict control of NOx emission concentration. At present, the more mature industrial flue gas back-end denitrification technologies are mainly SCR (selective catalytic reduction technology), SNCR (selective non-catalytic reduction technology) and the combined use of the two technologies. The reducing agents used in these three processes are all amino reducing agents, including liquid ammonia, ammonia water or urea solution.

[0003] Traditional SNCR technology uses amino reducing agents, and its denitrification efficiency is generally 30~60%, and its reaction temperature range is 850~1150℃. The reducing agent enters the flue gas at 850~1150℃, and in the presence of oxygen, it selectively reacts with NOx in the flue gas to produce nitrogen and water. The reaction temperature, residence time and contact degree have a decisive influence on the denitrification efficiency. When the reaction temperature is lower than 850℃, the reaction efficiency is low. When the reaction temperature is higher than 1150℃, the rate of reaction between the amino reducing agent and oxygen accelerates to reversely generate NOx. The residence time of the amino reducing agent in the flue gas within the reaction temperature range is short, about 0.2~0.5s, or the flue gas and the amino reducing agent are not in sufficient contact, which will result in low reaction efficiency. The two consequences of low reaction efficiency are that NOx cannot meet the emission standards after denitrification or that the amount of amino reducing agent added is increased to meet environmental protection requirements during industrial application, which in turn causes ammonia escape, secondary pollution and equipment corrosion.

[0004] For industrial installations that have already been built, SNCR technology is used for denitrification. In order to achieve standard NOx emissions in industrial flue gas, it is necessary to combine SNCR technology with SCR technology, and the cost of the transformation is extremely high. Summary of the invention

[0005] In view of the problems in the prior art, the present invention provides a liquid non-amino reducing agent and a preparation method and application thereof.

[0006] In order to achieve the above purpose, the technical solution adopted in this application is: A liquid non-amino reducing agent, the raw materials of which include 15-17% of industrial vegetable oil, 68-71% of methanol, 2.5-4.5% of ethyl acetate, 2-3% of pyridine and 6-10% of triazine compounds.

[0007] Preferably, the liquid non-amino reducing agent has a freezing point of less than -15°C and a kinematic viscosity of less than 20 mm at 50°C. 2 / s.

[0008] A preparation method of a liquid non-amino reducing agent, the specific preparation method is as follows: the industrial vegetable oil is mixed with methanol, ethyl acetate and pyridine, stirred at 50-60°C for 1-1.5h, then a triazine compound is added, heated to above 70°C, stirred for 1-2h, and then kept warm for 1-2h to obtain the reducing agent.

[0009] Application of a liquid non-amino reducing agent in SNCR denitrification of industrial flue gas.

[0010] Preferably, the denitrification method is as follows: when the flue or furnace can only open more than 3 holes or can use the existing more than 3 holes, the flue or furnace is opened in sections and staggered, and the liquid non-amino reducing agent is distributed and sprayed into the flue gas through a double-fluid spray gun with high pressure atomization, and the spraying direction of the double-fluid spray gun is perpendicular to the flue gas; when the flue or furnace can only open less than 3 holes or can use the existing less than 3 holes, the double-fluid spray gun is used to spray into the flue gas with high pressure atomization, and the spraying direction of the double-fluid spray gun is opposite to the direction of the flue gas flow.

[0011] Preferably, the flue gas temperature range of the denitration process is 400-1000°C.

[0012] Preferably, the mass ratio of the agent to NOX in the denitrification process is (0.3~1.2):1.

[0013] Compared with the prior art, the advantages and positive effects of the present invention are: The present application discloses a liquid non-amino reducing agent and a preparation method and application thereof. The raw materials of the liquid non-amino reducing agent include, by mass percentage, 15-17% of industrial vegetable oil, 68-71% of methanol, 2.5-4.5% of ethyl acetate, 2-3% of pyridine and 6-10% of triazine compounds. The liquid non-amino reducing agent is applied to industrial flue gas denitration to effectively reduce NOx in the flue gas to nitrogen, and can reduce the NOx concentration to less than 50mg / m 3 The denitrification efficiency reaches more than 85%; it can also avoid problems such as ammonium salt scaling and equipment corrosion caused by ammonia escape; the present invention is safe and reliable, low in cost, will not cause secondary pollution to the environment, and has strong practicality. DETAILED DESCRIPTION

[0014] In order to more clearly understand the above-mentioned purpose, features and advantages of the present invention, the present invention is further described below in conjunction with embodiments. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0015] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways than those described herein. Therefore, the present invention is not limited to the specific embodiments of the following disclosure.

[0016] Example 1: A liquid non-amino reducing agent of the present application, the raw material composition includes 15-17% industrial vegetable oil, 68-71% methanol, 2.5-4.5% ethyl acetate, 2-3% pyridine and 6-10% triazine compounds.

[0017] Among them, industrial vegetable oil is a liquid mixture obtained by rapidly thermally degrading biomass raw materials containing cellulose, hemicellulose and lignin in the absence of oxygen. Biomass raw materials mainly include rice husks, crop straws, economic forests, etc. The industrial vegetable oil used in the present invention contains ethers, esters, aldehydes, ketones and organic acids, and the relative content of each component is shown in Table 1.

[0018] Table 1 Components and contents of industrial vegetable oils

[0019] A preparation method of a liquid non-amino reducing agent, the specific preparation method is as follows: the industrial vegetable oil is mixed with methanol, ethyl acetate and pyridine, stirred at 50-60°C for 1-1.5h, then a triazine compound is added, heated to above 70°C and stirred for 1-2h, and then kept warm for 1-2h to obtain the obtained liquid non-amino reducing agent, the solidification point of which is less than -15°C, and the kinematic viscosity at 50°C is less than 20mm 2 / s.

[0020] The industrial vegetable oil, ethyl acetate and pyridine used in the present invention improve the solubility of triazine compounds in methanol. Industrial vegetable oil can be quickly decomposed in high-temperature flue gas to produce free radical gas with reducing properties, but the properties of these free radical gases are unstable and require a high decomposition temperature (800-1050°C). Triazine compounds can also be quickly pyrolyzed in high-temperature flue gas to generate HNCO gas with strong reducing properties, which can reduce NOX to nitrogen, water and carbon dioxide. Triazine compounds can be pyrolyzed at above 400°C, and the pyrolysis temperature range is 400-950°C.

[0021] When the liquid non-amino reducing agent of the present invention is applied to SNCR denitrification, the liquid non-amino reducing agent is sprayed into the flue gas at a position where the flue gas temperature ranges from 600 to 1000° C. in the furnace or flue of an industrial boiler. The reducing agent is pyrolyzed within 1 second to produce free radicals and HNCO with strong reducing properties, and NOX in the flue gas is reduced to nitrogen and water, thereby achieving deep denitrification.

[0022] Example 1 Take 150kg of industrial vegetable oil, 680kg of methanol, 25kg of ethyl acetate and 20kg of pyridine and stir them at 50℃ for 1h, then add 60kg of triazine compound, heat to 80℃ and keep warm and stir for 1h, and then keep warm for 1h to obtain the product.

[0023] Example 2 Take 160kg of industrial vegetable oil, 690kg of methanol, 25kg of ethyl acetate and 20kg of pyridine and stir them at 50℃ for 1.5h, then add 65kg of triazine compound, heat to 80℃, keep warm and stir for 1h, and then keep warm for 2h to obtain the product.

[0024] Example 3 Take 150kg of industrial vegetable oil, 700kg of methanol, 30kg of ethyl acetate and 25kg of pyridine and stir at 60℃ for 1h, then add 100kg of triazine compound, heat to 90℃ and keep warm and stir for 2h, then keep warm for 2h to obtain the product.

[0025] Comparative Example 1 Take 150kg of industrial vegetable oil, 680kg of methanol, 25kg of ethyl acetate and 20kg of pyridine, stir at 50℃ for 1h, heat to 80℃ and keep stirring for 1h, then keep warm for 1h to obtain the product.

[0026] Comparative Example 2 Take 690 kg of methanol, 25 kg of ethyl acetate and 20 kg of pyridine and stir at 50°C for 1.5 hours, then add 65 kg of triazine compound, heat to 80°C, keep warm and stir for 1 hour, and then keep warm for 2 hours to obtain the product.

[0027] Comparative Example 3 Take 150kg of industrial vegetable oil, 700kg of methanol and 30kg of ethyl acetate and stir them at 60℃ for 1h, then add 100kg of triazine compound, heat to 90℃ and keep warm and stir for 2h, then keep warm for 2h to obtain the product.

[0028] The liquid non-amino reducing agent SNCR denitrification technology was implemented under the regeneration flue gas working conditions of the catalytic cracking unit with a flue gas volume of 250000Nm3 / h and a NOx concentration of 240mg / m3. The liquid reducing agent obtained in Examples 1-3 and Comparative Examples 1-3 was transported to the distributor through a metering pump and then sprayed into the furnace through a dual-fluid spray gun according to different agent-nitrogen ratios (the agent-nitrogen ratio is the ratio of the amount of liquid non-amino reducing agent injected per unit time to the mass of NOx in the flue gas). The agent was added in different high-temperature flue gas intervals, and each area had 4 dosing ports. After 1s, the NOx concentration in the exhaust flue gas was detected (in mg / m³). The results are shown in Table 2.

[0029] Table 2 Detection results of NOx concentration in exhaust gas after 1 second in Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2 and Comparative Example 3

[0030] From the results in Table 2, it can be seen that Examples 1 to 3 can all achieve controlling the NOx concentration in the flue gas below 50 mg / m³, and the denitration efficiency reaches more than 85%; Comparative Example 1 obtains a liquid reducing agent in the absence of triazine compounds, and its denitration efficiency is significantly reduced. The reason is that the reducing free radicals generated by the pyrolysis of industrial vegetable oils are unstable in nature, and the HNCO generated by the pyrolysis of triazine compounds and the free radicals synergize to play a better denitration effect; Comparative Example 2 obtains a liquid reducing agent in the absence of industrial vegetable oils, and its denitration effect is also not ideal. The reason is that the reducing free radical gaseous substances generated by the pyrolysis of industrial vegetable oils are lacking, and the solubility of triazine compounds is affected, and the content of HNCO generated is reduced; Comparative Example 3 obtains a liquid reducing agent in the absence of pyridine, and its denitration efficiency is also not ideal. The reason is that the solubility of triazine compounds is affected, and the content of HNCO generated is reduced.

[0031] The above description is only a preferred embodiment of the present invention and does not limit the present invention in other forms. Any technician familiar with the profession may use the technical content disclosed above to change or modify it into an equivalent embodiment with equivalent changes and apply it to other fields. However, any simple modification, equivalent change and modification made to the above embodiment based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A liquid non-amino reducing agent, characterized in that: The raw material composition of the liquid non-amino reducing agent includes 15-17% of industrial vegetable oil, 68-71% of methanol, 2.5-4.5% of ethyl acetate, 2-3% of pyridine and 6-10% of triazine compounds.

2. A liquid non-amino reducing agent according to claim 2, characterized in that: The liquid non-amino reducing agent has a freezing point of less than -15°C and a kinematic viscosity of less than 20 mm at 50°C. 2 / s.

3. The method for preparing a liquid non-amino reducing agent according to claim 2, characterized in that: The specific preparation method is as follows: the industrial vegetable oil is mixed with methanol, ethyl acetate and pyridine, stirred at 50-60° C. for 1-1.5 hours, then a triazine compound is added, heated to above 70° C., stirred for 1-2 hours, and then kept warm for 1-2 hours.

4. Use of a liquid non-amino reducing agent according to claim 3 in SNCR denitrification of industrial flue gas.

5. The use of a liquid non-amino reducing agent in SNCR denitrification of industrial flue gas according to claim 4, characterized in that: The denitrification method is as follows: when the flue or furnace can only open more than 3 holes or can use the existing more than 3 holes, the flue or furnace is staggeredly opened, and the liquid non-amino reducing agent is distributed and then sprayed into the flue gas by high-pressure atomization with a double-fluid spray gun, and the spraying direction of the double-fluid spray gun is perpendicular to the flue gas; when the flue or furnace can only open less than 3 holes or can use the existing less than 3 holes, the double-fluid spray gun is used to spray into the flue gas by high-pressure atomization, and the spraying direction of the double-fluid spray gun is opposite to the direction of the flue gas flow.

6. The use of a liquid non-amino reducing agent in SNCR denitrification of industrial flue gas according to claim 5, characterized in that: The flue gas temperature range of the denitrification process is 400-1000°C.

7. The use of a liquid non-amino reducing agent in SNCR denitrification of industrial flue gas according to claim 5, characterized in that: The mass ratio of the agent to NOX in the denitrification process is (0.3~1.2):1.

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