Non-amino reducing agent, preparation method and application in SNCR deep denitration

Abstract

The application discloses a non-amino reducing agent, a preparation method and application in SNCR deep denitration, the reducing agent includes mixed solution and free calcium oxide, and the mixed solution includes biomass cracking solution 4 parts, cyanuric acid 0.5-1 part, desalted water 0.5-1 part and ethylene glycol 0.5-1 part by weight; the mass ratio of the mixed solution to the free calcium oxide is 6:(0.5-1); the non-amino reducing agent is applied to industrial denitration, can make the concentration of NO x concentration is less than 30mg / m 3 The following, the denitration efficiency reaches more than 92%; ammonia escape secondary pollution and ammonium salt fouling and other safety risks can also be avoided, the operation reliability and safety of the denitration system are improved, and the cost is low, and the benefit is good.

Description

Technical Field

[0001] This invention relates to the field of SNCR denitrification technology, specifically to a non-amino reducing agent, its preparation method, and its application in SNCR deep denitrification. Background Technology

[0002] With more standardized flue gas treatment, flue gas pollutants have reached near-zero ultra-clean standards, including NO. x The concentration must be controlled below 30 mg / m³ 3 .

[0003] Traditional ammonia-based selective non-catalytic reduction (SNCR) denitrification technology involves injecting a reducing agent containing amino groups (mainly urea or ammonia water) into the boiler furnace or flue gas duct within a temperature range of 850–1150°C. Under specific temperature and oxygen conditions, this selectively removes NO from the flue gas. x NO in flue gas is reduced to N2 and H2O. x End-of-pipe processing technology is one of the earliest and most mature technologies used both domestically and internationally.

[0004] NO removal technology using amino-SNCR x The reduction reaction occurs within a specific temperature range, which is relatively narrow, ranging from 850℃ to 1150℃. The reaction temperature significantly affects the NO content in the ammonia SNCR reaction. x The removal rate of NO has a significant impact. If the temperature is too low, the NH3 reaction will be incomplete, leading to so-called "ammonia penetration," which increases the amount of NH3 escaping and causes secondary pollution. As the temperature rises, molecular motion accelerates, and the diffusion process of ammonia is strengthened. For SNCR, when the temperature rises above 800℃, the chemical reaction rate increases significantly, and the NO reduction rate reaches its maximum of about 70% at around 900℃. If the temperature continues to rise, exceeding 1200℃, the oxidation reaction between NH3 and O2 will intensify, generating N2, N2O, or NO, increasing the NO concentration in the flue gas. x Concentration, but denitrification rate decreases.

[0005] The reaction temperature determines the upper limit of the denitrification rate, while the residence time of the ammonia reducing agent and the degree of mixing with the flue gas determine the reaction process and speed. The ammonia reducing agent and flue gas react and mix simultaneously, and their residence time and mixing effect directly determine the efficiency of achieving the upper limit of the denitrification rate at a given temperature. Under the same conditions, a longer residence time of the reducing agent results in better denitrification efficiency. During this time, the mixing of the reducing agent with the flue gas, the evaporation of water, the decomposition of the reducing agent, and the reaction of NO... xThe reduction and other steps must all be completed within 0.5 seconds. The residence time of atomized ammonia in the flue gas zone depends on factors such as the size of the flue gas zone, the flue gas velocity, the atomization state of the solution, and the mixing form between the atomized ammonia and the flue gas. A residence time of 0.5 seconds or more, and seamless, complete mixing, can achieve the upper limit of the aforementioned denitrification rate for NO reduction in the flue gas. However, in most cases, the residence time of the ammonia reducing agent in the flue gas zone is between 0.2 and 0.5 seconds, and due to the presence of localized NO in the ammonia diffusion area... x In actual operating conditions where the concentration is uneven and too low, the reducing agent fails to undergo a complete reduction reaction, resulting in low utilization and failure to achieve optimal denitrification efficiency. Therefore, the denitrification rate of amino-SNCR is usually only between 40% and 70%.

[0006] Given that the upper limit of the denitrification rate of amino-SNCR is only 70% and its applicable reaction temperature is relatively narrow, the NO in the factory's exhaust gas... x To achieve near-zero cleanliness standards (≤30mg / m³) 3 The flue gas temperature in the reaction zone must meet the requirements, and the initial NO... x The concentration must be 100 mg / m³ 3 The following; Initial NO x Concentration exceeding 100 mg / m 3 For this purpose, it needs to be combined with SCR to achieve deep denitrification.

[0007] Power companies are carrying out major hazard source control measures in liquid ammonia tank areas and accelerating the upgrading and transformation of urea substitution. After the upgrade, SCR will use urea as a reducing agent, requiring the construction of a new urea pyrolysis ammonia production unit, which has high operating costs, with the electricity consumption for pyrolyzing one ton of urea being approximately 2000 kWh.

[0008] In summary, using urea as a reducing agent requires a combined SNCR and SCR denitrification technology to achieve the desired NO reduction in flue gas. x The concentration reaches the ultra-clean standard, but the cost of upgrading and operating is relatively high.

[0009] According to the SNCR reaction, 0.5 mol of urea is needed to reduce 1 mol of NO. However, since it is actually a catalystless reaction, the residence time is short and the agent and fumes are not mixed evenly, the amount of reducing agent needs to be 1.5 to 2 times larger than this theoretical value. If the NH3 / NO ratio is too large, it will inevitably lead to an increase in ammonia escape, causing secondary pollution and safety risks such as ammonium salt scale buildup in the low-temperature energy-saving section, which is not conducive to long-term operation. Summary of the Invention

[0010] This invention provides a non-amino reducing agent, a preparation method, and its application in SNCR deep denitrification, which at least solves one of the many defects of the prior art.

[0011] To achieve the above objectives, the present invention provides the following solution:

[0012] A non-amino reducing agent includes a mixture and free calcium oxide. By weight, the mixture includes 4 parts of biomass pyrolysis liquid, 0.5 to 1 part of cyanuric acid, and 1 to 2 parts of excipients; the mass ratio of the mixture to free calcium oxide is 6:(0.5 to 1).

[0013] Further, by weight, the excipients are: 0.5-1 parts demineralized water and 0.5-1 parts ethylene glycol.

[0014] The present invention also provides a method for preparing the above-mentioned non-amino reducing agent, which involves mixing biomass pyrolysis liquid with cyanuric acid, demineralized water and ethylene glycol, adding free calcium oxide to the mixture and stirring for 1-2 hours, and then heating to above 70°C and holding for 2-3 hours to obtain the agent.

[0015] Furthermore, the non-amino reducing agent has a freezing point below -12°C and a kinematic viscosity of 20 mmHg at 40°C. 2 / s or less.

[0016] This invention also proposes the application of the reducing agent obtained by the above preparation method in SNCR deep denitrification.

[0017] In the above applications, the mass ratio of nitrogen to agent in the denitrification process is (0.6-0.8):1.

[0018] In the above applications, the flue gas temperature in the denitrification process is 670–1020°C.

[0019] In the above application, the denitrification method involves dividing the furnace or flue into sections with staggered openings within a suitable flue temperature range, distributing the reducing agent, and then atomizing it under high pressure through a dual-fluid spray gun to form a fan-shaped direct injection, which is then injected into the furnace or flue to make vertical contact with the high-temperature flue gas.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] 1. The non-amino reducing agent provided by this invention can reduce NO in industrial denitrification processes. x Concentration below 30 mg / m 3 The denitrification efficiency reaches over 92%, meeting the ultra-clean emission standards for flue gas.

[0022] 2. The non-amino reducing agent provided by this invention can avoid the safety risks of secondary pollution from ammonia escape and ammonium salt scale buildup when applied to industrial denitrification, improve the operational reliability of the denitrification system and the long-term operational safety of subsequent systems, and reduce multiple cost inputs, thus meeting the requirements of green denitrification processes. Detailed Implementation

[0023] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] Bio-oil is a mixture formed by the rapid decomposition of various degradation products of cellulose, hemicellulose, and lignin under anaerobic conditions. Biomass mainly includes fuelwood forests, economic forests, timber forests, crop straw, and agricultural and forestry product processing residues such as sago palm residue and sawdust. Bio-oil can be used directly as fuel for oil-fired boilers and industrial kilns; secondly, after refining, it can replace No. 0 diesel fuel as internal combustion engine fuel; and finally, it can be used for the extraction of chemical raw materials or the processing of various chemical products such as preservatives, food seasonings, desulfurization and denitrification agents, organic fertilizers, hydroxyacetaldehyde, and L-glucan. The biomass pyrolysis oil used in this invention has a density of 1.15-1.20 g / mL and contains 6.7-8.9 wt% soluble solids, 12-17 μg / L tar, 6.9-18.4 wt% total acid, 0.63-0.92 mg / L volatile phenols, 0.36-0.75 mg / L ketones, and 0.20-0.35 mg / L alcohols. The relative contents of some components are shown in Table 1.

[0025] Table 1:

[0026] Components relative content Components relative content Formic acid 4.8 3-Methyl-2-cyclopentenone 1.4 Acetic acid 47.9 phenol 2.8 1-Hydroxy-2-propanone 9.9 2-Hydroxy-3-methylcyclopentenone 2.1 propionic acid 9.9 2-Methylphenol 1 1-Hydroxy-2-Butanone 2.2 4-Methylphenol 1.8 butyric acid 3.6 4-Methoxyphenol 1.5 furfural 4 3-Ethylphenol 1 furfuryl alcohol 1.9 3-Ethyl-2-hydroxy-2-cyclopentenone 0.6 Butyl lactone 1.8 2,6-Dimethoxyphenol 0.7 2-Methyl-2-cyclopentenone 0.7 4-Ethyl-2-methoxyphenol 0.4

[0027] The non-amine reducing agent of this invention is prepared by using free calcium oxide, cyanuric acid, and bio-lysate to create a non-amine bio-based denitrification reducing agent. The biomass lysate, cyanuric acid, demineralized water, and ethylene glycol are mixed at a mass ratio of 4:(0.5-1):(0.5-1):(0.5-1). The mixture is then stirred and reacted with free calcium oxide at a ratio of 6:(0.5-1) for 1-2 hours. The reaction product is then heated to above 70°C and held at that temperature for 2-3 hours to obtain the non-amine reducing agent. The freezing point of the non-amine reducing agent is controlled below -12°C, and its kinematic viscosity (40°C) is controlled at 20 mmHg. 2 / s or less.

[0028] Free calcium oxide has desulfurization and denitrification effects on flue gas, but its utilization rate is low and its denitrification and reducing properties are not prominent because the pores of lime are easily blocked by the generated calcium sulfate. Biolysis liquid can rapidly decompose into highly reducing free radicals in a catalyst-free, high-temperature flue gas environment, reacting with NO to produce N2, CO2, and H2O. However, its physicochemical properties are unstable, mainly manifested in the fact that the composition of the biolysis liquid changes with storage time and temperature. Even to a certain extent, the originally homogeneous biolysis liquid will separate into two or three immiscible parts. Furthermore, the flue gas temperature range for the decomposition of this biolysis liquid is relatively narrow (820–1020℃).

[0029] Cyanuric acid can rapidly decompose into highly reducing monomeric HNCO groups in a catalyst-free high-temperature flue gas environment. These groups can react with NO to generate N2, CO2, and H2O, and the decomposition temperature range is relatively wide (650–1050℃).

[0030] This invention employs a mixture of biolysis solution and cyanuric acid, which broadens the suitable temperature range for rapid decomposition of the mixture in the flue gas environment, from 670 to 1020°C, thus achieving a wide temperature range. Further mixing with free calcium oxide stabilizes the physicochemical properties of the product. Ethylene glycol and demineralized water contribute to mixing and lowering the freezing point. In the presence of free calcium oxide adsorption, the biolysis solution and cyanuric acid synergistically adsorb onto the surface of free calcium oxide, preventing pore blockage and improving denitrification efficiency.

[0031] When the ammonia-free reducing agent described in this invention is applied to denitrification, it is injected into the boiler furnace or horizontal flue within a temperature range of 670–1020°C (no catalyst required). This process can decompose long-chain organic compounds into single-carbon or double-carbon free functional groups (i.e., highly reducing free groups) within 0.2 seconds. These free groups then react with NO in the flue gas. x The preferential reduction reaction (NO has high electronegativity and a strong ability to attract electrons) produces N2 and H2O, achieving non-amino selective non-catalytic reduction and deep denitrification. In SNCR, it can completely replace ammonia or urea and is more efficient. Some effective groups react with NO. x The reaction occurs at 670–1020℃. Taking NO as an example, the reaction formula is as follows:

[0032] (-CH2)+2(-CH3)+10NO═5N2+4H2O+3CO2①;

[0033] 2(-CH2)+6NO═3N2+2H2O+2CO2②;

[0034] 2(-C2H2)+10NO═5N2+2H2O+4CO2③;

[0035] 4(-H) + 2NO ═ N2 + H2O ④;

[0036] 4HCCO+18NO═9N2+2H2O+8CO2⑤;

[0037] 4HOCO+10NO═5N2+2H2O+4CO2⑥;

[0038] 4HNCO+6NO═5N2+2H2O+4CO2⑦.

[0039] Example 1

[0040] Take 400 kg of biomass pyrolysis liquid, 50 kg of cyanuric acid, 50 kg of demineralized water and 50 kg of ethylene glycol, mix and stir to emulsify. Add the emulsion and 46 kg of free calcium oxide to the reaction vessel, stir and mix for 1 hour; heat to 70℃ and keep at a constant temperature for 2 hours to obtain a non-amino reducing agent.

[0041] Example 2

[0042] Take 400 kg of biomass pyrolysis liquid, 90 kg of cyanuric acid, 50 kg of deionized water and 60 kg of ethylene glycol, mix and stir to emulsify. Add the emulsion and 100 kg of free calcium oxide to the reaction vessel, stir and mix for 1.5 hours; heat to 75℃ and keep at a constant temperature for 2.5 hours to obtain a non-amino reducing agent.

[0043] Example 3

[0044] Take 400 kg of biomass pyrolysis liquid, 80 kg of cyanuric acid, 60 kg of demineralized water and 60 kg of ethylene glycol, mix and stir to emulsify. Add the emulsion and 80 kg of free calcium oxide to the reaction vessel, stir and mix to react for 1.5 hours; heat to 75℃ and keep at a constant temperature for 2.5 hours to obtain a non-amino reducing agent.

[0045] Example 4

[0046] Take 400 kg of biomass pyrolysis liquid, 100 kg of cyanuric acid, 100 kg of demineralized water and 100 kg of ethylene glycol, mix and stir to emulsify. Add the emulsion and 100 kg of free calcium oxide to the reaction vessel, stir and mix for 2 hours; heat to 80℃ and keep at a constant temperature for 3 hours to obtain a non-amino reducing agent.

[0047] Comparative Example 1

[0048] Take 400 kg of biomass pyrolysis liquid, 100 kg of demineralized water and 100 kg of ethylene glycol, mix and stir to emulsify. Add the emulsion and 100 kg of free calcium oxide to the reaction vessel, stir and mix for 2 hours; heat to 80℃ and keep at a constant temperature for 3 hours to obtain a non-amino reducing agent.

[0049] Comparative Example 2

[0050] Take 400 kg of biomass pyrolysis liquid, 100 kg of cyanuric acid, 100 kg of demineralized water and 100 kg of ethylene glycol, mix and stir to emulsify. Add the emulsion and 50 kg of free calcium oxide to the reaction vessel, stir and mix for 2 hours; heat to 80℃ and keep at a constant temperature for 3 hours to obtain a non-amino reducing agent.

[0051] Comparative Example 3

[0052] Take 100 kg of cyanuric acid, 100 kg of deionized water and 100 kg of ethylene glycol and mix them. Then add 100 kg of free calcium oxide into the reaction vessel and stir to react for 2 hours. Heat to 80℃ and keep at that temperature for 3 hours to obtain a non-amino reducing agent.

[0053] Experimental Example 1

[0054] The kinematic viscosity (40°C) and freezing point of the non-amino reducing agents of Examples 1-4 and Comparative Examples 1-3 were tested, and the results are shown in Table 2. At the same time, the stability of the above reducing agents after storage for 15 days and 30 days were tested, and the results are shown in Table 3.

[0055] Table 2:

[0056]

[0057] Table 3:

[0058]

[0059]

[0060] Experiment Example 2

[0061] Under the following operating conditions: flue gas volume 300,000 Nm³ 3 / h, NO x Concentration 400mg / m 3 Non-amino SNCR is implemented in the flue gas of a coal-fired CFB boiler. Demineralized water is introduced to dilute the non-amino bio-agent by 50%, and different agent-to-nitrogen ratios are applied (the agent-to-nitrogen ratio is the ratio of the amount of non-amino bio-agent injected per unit time to the NO content in the flue gas). x The ratio of the generated mass (the non-amino reducing agents of Examples 1-4 and Comparative Examples 1-3) was taken, metered, pumped to a distributor, and then injected into the furnace via a two-fluid spray gun (mixed with compressed air). The agents were vertically contacted and mixed in different high-temperature flue gas zones. After 0.2 seconds, the NO content in the exhaust gas was measured. x The concentrations and results are shown in Table 4.

[0062] Table 4:

[0063]

[0064] As can be seen from Table 4, Examples 1-4 were carried out for denitrification reactions at different temperature ranges and with different agent-to-nitrogen ratios, and NO was detected. x The concentrations were all between 30 mg / m³ 3 Below, the denitrification efficiency reached over 92%. Comparative Example 1, without cyanuric acid, showed a significant decrease in denitrification efficiency. This may be because, in the absence of cyanuric acid, the denitrification temperature range of the biomass pyrolysis solution is narrower, and the thermal stability of the biomass pyrolysis solution is poorer, preventing the active substances from forming HNCO groups with cyanuric acid for synergistic denitrification. Comparative Example 2, even with reduced free calcium oxide, also showed unsatisfactory denitrification. This may be because, with reduced free calcium oxide, the NO... x The adsorption capacity decreases, on the other hand, it is related to NO. x The reduced contact area decreases the denitrification effect; in Comparative Example 3, the denitrification effect is also not ideal without biomass pyrolysis liquid. Without biomass pyrolysis liquid, the number of active groups generated in each temperature zone is greatly reduced, and the micropores on the surface of free calcium oxide will be quickly blocked, seriously affecting the denitrification efficiency.

[0065] The economic advantages of the SNCR deep denitrification technology of the present invention, which uses non-amino biological agents as reducing agents, compared with the currently used SNCR and SCR technologies are shown in Table 5.

[0066] Table 5:

[0067]

[0068] In addition, compared with the SNCR+SCR combined denitrification technology, the present invention reduces the cost of use by 40%, and has no safety risks such as ammonia escape secondary pollution and ammonium salt scale buildup, which is conducive to long-term operation.

[0069] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A non-amino reducing agent, characterized in that, The mixture includes a liquid mixture and free calcium oxide. By weight, the liquid mixture includes 4 parts of biomass pyrolysis liquid, 0.5 to 1 part of cyanuric acid, and 1 to 2 parts of excipients. The mass ratio of the mixed solution to free calcium oxide is 6:(0.5-1); by weight, the auxiliary agent is: 0.5-1 parts of deionized water and 0.5-1 parts of ethylene glycol.

2. The method for preparing the non-amino reducing agent according to claim 1, characterized in that, The biomass pyrolysis solution is mixed with cyanuric acid, demineralized water, and ethylene glycol. Free calcium oxide is added to the mixture and stirred for 1-2 hours. Then, the mixture is heated to above 70°C and kept at that temperature for 2-3 hours to obtain the final product.

3. The preparation method according to claim 2, characterized in that, The non-amino reducing agent has a freezing point below -12℃ and a kinematic viscosity of 20 mmHg at 40℃. 2 / s or less.

4. The application of the reducing agent obtained by the preparation method of claim 2 or 3 in SNCR deep denitrification.

5. The application according to claim 4, characterized in that, The mass ratio of the agent to nitrogen in the denitrification process is (0.6-0.8):

1.

6. The application according to claim 4, characterized in that, The temperature of the flue gas zone in the denitrification process is 670–1020℃.

7. The application according to claim 4, characterized in that, The denitrification method involves dividing the furnace or flue into sections with staggered openings, distributing the reducing agent, and then atomizing it under high pressure through a dual-fluid spray gun to form a fan-shaped direct spray, which is then injected into the furnace or flue to make vertical contact with the high-temperature flue gas.

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