阅读说明：本技术 一种渗氮生物质先进再燃脱硝剂的制备方法与应用 (preparation method and application of nitridized biomass advanced reburning denitration agent ) 是由 王菁 程芳琴 杨凤玲 孟江涛 王飞 于 2019-09-02 设计创作，主要内容包括：本发明属于生物质应用与锅炉烟气脱硝技术领域,公开了一种渗氮生物质先进再燃脱硝剂的制备方法与应用。本发明主要解决SNCR技术温度窗窄,效率低,工艺复杂和生物质难以大规模利用等问题。本发明渗氮生物质先进再燃脱硝剂的制备方法包括：(1)将生物质原料进行预处理；(2)将预处理的生物质原料直接进行表面氨化处理,或将预处理的原料低温烘焙,得到炭化生物质焦,将其进行表面氨化处理；(3)氨化处理后经过充分搅拌,低温烘干,冷却至室温,得到渗氮生物质先进再燃脱硝剂。本发明的应用方法为：将脱硝剂与再循环烟气混合,从燃尽区上部喷入炉膛,在炉膛出口和水平烟道内还原NO<Sub>x</Sub>。(The invention belongs to the technical field of biomass application and boiler flue gas denitration, and discloses a preparation method and application of a nitridized biomass advanced reburning denitration agent. The invention mainly solves the problems of narrow temperature window, low efficiency, complex process, difficult large-scale utilization of biomass and the like of the SNCR technology. The preparation method of the advanced reburning denitration agent for nitriding biomass comprises the following steps: (1) pretreating a biomass raw material; (2) directly carrying out surface ammoniation treatment on the pretreated biomass raw material, or baking the pretreated raw material at low temperature to obtain carbonized biomass coke, and carrying out surface ammoniation treatment on the carbonized biomass coke; (3) and fully stirring, drying at low temperature and cooling to room temperature after ammoniation treatment to obtain the nitridized biomass advanced reburning denitrifier. The application method of the invention comprises the following steps: mixing the denitrifier with the recirculated flue gas, spraying the denitrifier into the hearth from the upper part of the burnout zone, and reducing NOx in the hearth outlet and the horizontal flue.)

1. A preparation method of a nitridized biomass advanced reburning denitration agent is characterized by comprising the following steps: the method comprises the following steps:

(1) Pretreating a biomass raw material;

(2) directly carrying out surface ammoniation treatment on the pretreated biomass raw material, or baking the pretreated biomass raw material at low temperature to obtain carbonized biomass coke, and carrying out surface ammoniation treatment on the carbonized biomass coke;

(3) And fully stirring, drying at low temperature and cooling to room temperature after ammoniation treatment to obtain the nitridized biomass advanced reburning denitrifier.

2. The method for preparing the nitridized biomass advanced reburning denitration agent according to claim 1, wherein the method comprises the following steps: the biomass raw material in the step (1) is straw, rice hull, wood chip or corncob.

3. the method for preparing the nitridized biomass advanced reburning denitration agent according to claim 1, wherein the method comprises the following steps: the pretreatment method in the step (1) comprises the following steps: the biomass raw material is dried, crushed, ground and screened, and the selected particle size range of the screening is 0.5-2 mm.

4. The method for preparing the nitridized biomass advanced reburning denitration agent according to claim 1, wherein the method comprises the following steps: the specific method for performing surface ammoniation treatment in the step (2) comprises the following steps: spraying the biomass for 1-2 hours or dipping the biomass for 6-24 hours by using the additive solution.

5. The method for preparing the nitridized biomass advanced reburning denitration agent according to claim 1, wherein the method comprises the following steps: the low-temperature baking conditions in the step (2) are as follows: under the protection of nitrogen atmosphere or boiler circulating flue gas, the temperature is 200-300 ℃, and the time is 20-30 min.

6. The method for preparing the nitrified biomass advanced reburning denitration agent according to claim 4, wherein the method comprises the following steps: the additive solution in the step (2) is as follows: saturated solution of urea or ammonia solution with concentration of 25-28%.

7. The method for preparing the nitridized biomass advanced reburning denitration agent according to claim 1, wherein the method comprises the following steps: and (4) drying at low temperature in the step (3), wherein the waste heat of a boiler is used for drying, the drying temperature is 50 ℃, and the drying is carried out until the water content is lower than 15%.

8. The application of the nitridized biomass advanced reburning denitration agent as defined in any one of claims 1-7, which is characterized in that: the nitridized biomass advanced reburning denitration agent is applied to denitration of flue gas of a coal-fired boiler, and the specific application method comprises the following steps:

Mixing the nitriding biomass reburning denitrifier particles with the recirculating flue gas, and spraying the mixture into the hearth from the upper part of a burnout zone in a flue region with the temperature of 850-1100 ℃, so that part of NOx formed in the main burning zone reacts in the outlet of the hearth and the flue to generate N2.

Technical Field

the invention belongs to the technical field of biomass application and boiler flue gas denitration, and particularly relates to a preparation method and application of a nitridized biomass advanced reburning denitration agent.

Background

Nitrogen oxides (NOx) seriously damage the ecological environment and threaten human health. Increasingly stringent environmental regulations require the development of advanced technologies to reduce the emission of pollutants such as NOx. Currently, there are two broad categories of measures to control NOx emissions, one being low NOx combustion technology during coal combustion and the other being flue gas denitrification technology after combustion.

the reburning technology is a high-efficiency low NOx combustion technology, 15-20% of main fuel is arranged above a main combustion area, oxygen in flue gas is consumed, and NOx is reduced to N2 by using hydrocarbons formed by incomplete combustion under the condition that the excess air factor is less than 1. The reburning technology changes the burning mode in the hearth, the denitration effect is limited by the fuel property, and the incomplete burning loss is large. The SNCR technology is a typical flue gas denitration technology, does not need a catalyst, has the operation cost far lower than that of SCR, has short construction period and is easy to modify. However, the SNCR reaction temperature window is narrow (900 ℃ -1100 ℃), NH3 is oxidized to generate NOx when the temperature is higher than 1100 ℃, and the reaction rate of NH3 and NOx is low when the temperature is lower than 900 ℃ and limited by OH. In practical application, because the temperature in the flue is rapidly reduced, the temperature gradient is large, the retention time is limited, the sprayed reducing agent is difficult to effectively mix and fully react with the flue gas, and the actual denitration efficiency can only reach 30-50%. In addition, because of insufficient reaction, incompletely reacted ammonia remains in the tail gas, high ammonia leakage is formed, a flue is easily corroded, and secondary pollution is caused.

In order to further improve the denitration efficiency, the reburning technology is combined with the SNCR technology to form an advanced reburning technology, and the technology can improve the denitration efficiency by spraying the amino reducing agent into a reburning area. The utility model with patent publication number CN 1387006A discloses a method and a device for reducing nitrogen oxide emission of a coal-fired boiler, and the method provides staged combustion of main fuel, improves reburning, and injects a promoter and a nitrogen agent into a reburning area to improve the denitration effect. However, the combustion mode influence generated by fuel classification still exists, and the accelerant used in the method is sodium hydroxide powder or solution, and natural gas is used as reburning gas, so that the denitration cost is increased. In patent application CN 101244361 a and CN 101433799 a, ultrafine coal powder, natural gas and biomass gasified gas are respectively used as promoters for SNCR reaction, although the reaction temperature window can be reduced to different degrees, burnout of ultrafine coal powder is difficult to guarantee, the natural gas and biomass gasified gas device process is complicated, and it is difficult to ensure sufficient mixing of reburning fuel as promoter and amino reducing agent, and it is difficult to control ammonia escape to a very low level.

The biomass has the characteristics of low sulfur, low nitrogen, high volatile matter, high coke ash activity, zero CO2 net emission and the like. According to measurement and calculation, the total amount of biomass energy resources which can be developed in China is about 10 hundred million tons of standard coal per year in a long term, and the biomass energy resources are abundant in quantity and various in variety. However, biomass has the defects of high water content, low energy density, easy decay, unsuitability for long-term storage and long-distance transportation and the like, so that the large-scale utilization of the biomass is limited. Therefore, how to combine the characteristics of biomass and effectively combine biomass energy utilization with flue gas pollutant control is an urgent problem to be solved in the current energy environment field.

Disclosure of Invention

Aiming at the problems of narrow temperature window, low efficiency, complex process, difficult large-scale utilization of biomass and the like of the SNCR technology, the invention provides a preparation method and application of a nitridized biomass advanced reburning denitrifying agent.

in order to achieve the purpose, the invention adopts the following technical scheme:

A preparation method of a nitridized biomass advanced reburning denitration agent comprises the following steps:

(1) Pretreating a biomass raw material;

(2) directly carrying out surface ammoniation treatment on the pretreated biomass raw material, or baking the pretreated biomass raw material at low temperature to obtain carbonized biomass coke, and carrying out surface ammoniation treatment on the carbonized biomass coke;

(3) and fully stirring, drying at low temperature and cooling to room temperature after ammoniation treatment to obtain the nitridized biomass advanced reburning denitrifier.

The biomass raw material in the step (1) is straw, rice hull, wood chip or corncob and the like. The biomass raw materials have the characteristics of low sulfur, low nitrogen, high volatile matter, high coke ash activity, zero CO2 net emission and the like, are excellent reburning fuels, have the promotion effect on SNCR due to coal dust, and are easy to burn out compared with the coal dust; alkali metal elements in the biomass can catalyze the SNCR reaction, so that the SNCR denitration efficiency is further improved. In addition, the biomass is abundant in various places in China, is cheap and easy to obtain, can consume a large amount of biomass waste through the technology, and simultaneously realizes effective utilization of biomass energy.

The pretreatment method in the step (1) comprises the following steps: the biomass raw material is dried, crushed, ground and screened, and the selected particle size range of the screening is 0.5-2 mm. The biomass has the defects of high water content, low energy density, easy decay and the like, and the large-scale utilization of the biomass is limited. Before the biomass fuel is used as fuel, the biomass must be air-dried, so that the moisture and volume of the raw material are reduced, and the grinding treatment is convenient. Through grinding and screening, the particle size of the raw material is controlled to be 2-0.5mm, so that the specific surface area of the material in contact with the additive solution in the ammoniation stage can be increased, the ammoniation efficiency is improved, and the denitration agent can be fully mixed with the flue gas after entering the furnace, so that the reaction efficiency is improved.

The specific method for performing surface ammoniation treatment in the step (2) comprises the following steps: spraying the biomass for 1-2 hours or dipping the biomass for 6-24 hours by using the additive solution. The spraying time of the additive solution is determined according to the concentration of NOx in the flue gas. Through spraying and ammonia agent solution, the biomass and the ammonia agent are fully combined and enter the furnace together, the problem that the liquid ammonia agent and the solid biomass furnace are not contacted fully in the traditional biomass advanced reburning process is solved, the using amount of the ammonia agent is reduced, and the ammonia escape is reduced.

the low-temperature baking conditions in the step (2) are as follows: under the protection of nitrogen or boiler circulating flue gas atmosphere, the baking temperature is 200-300 ℃, and the baking time is 20-30 min. The biomass is baked at low temperature in inert atmosphere and is subjected to mild pyrolysis, the quality of the biomass is improved, the water content, the C/H ratio and the O/C ratio are reduced after baking, the porosity and the specific surface area are greatly improved, the heat value and the energy density are increased, and the ammonification efficiency and the combustion efficiency after charging are improved. And the boiler circulating flue gas is adopted to replace nitrogen, so that the process cost can be reduced.

The additive solution in the surface ammoniation treatment in the step (2) is as follows: saturated solution of urea or ammonia solution with concentration of 25-28%. The use of the additive solution with higher concentration improves the ammoniation efficiency, reduces the ammoniation time and reduces the volume of the liquid storage tank.

and (4) drying at low temperature in the step (3), wherein the waste heat of a boiler is used for drying, the drying temperature is 50 ℃, and the drying is carried out until the water content is lower than 15%. The ammoniated material has large water content and must be dried, so that the energy density of the material is improved and the requirement of entering a furnace is met; because ammonia water and urea are volatile, the drying temperature must be controlled below 50 ℃, and the loss of ammonia agent in drying is reduced; and the waste heat of the boiler is adopted, so that the energy consumption of the process is reduced, and the cost is reduced.

the application of the nitriding biomass advanced reburning denitration agent is characterized in that the nitriding biomass advanced reburning denitration agent is applied to denitration of flue gas of a coal-fired boiler, and the specific application method comprises the following steps:

Nitriding biomass is firstly mixed with re-burning denitrifying agent particles and recycled flue gas, and the mixture is sprayed into a hearth from the upper part of a burnout zone in a flue region with the temperature of 850-1100 ℃, so that part of NOx formed in a main burning zone reacts in the outlet of the hearth and the flue to generate N2.

Compared with the prior art, the invention has the following advantages:

1. the combination of the reburning technology and the SNCR technology can obviously improve the denitration efficiency, effectively reduce the dosage of the amino reducing agent required when the SNCR technology is used alone, reduce the denitration cost and reduce the ammonia escape.

2. the biomass raw material is rich and has wide sources, and the utilization rate of the biomass resource is greatly improved; the efficient and cheap denitration agent is prepared by utilizing biomass renewable resources, so that the problem of incomplete fuel combustion caused by taking 15% of main fuel as reburning fuel in the traditional reburning technology is solved; the double effects of biomass energy utilization and environmental protection are realized.

3. the biomass is fully contacted with the amino reducing agent, and then the circulating flue gas is sprayed into the outlet area of the hearth, so that the mixing degree of reactants can be enhanced, the SNCR reaction rate is improved, and the ammonia leakage is reduced; and can avoid the reduction of denitration efficiency caused by overhigh oxygen concentration in the SNCR reaction zone.

4. alkali metal elements in the biomass are gasified, and the number of OH groups in the SNCR reaction zone is increased through the alkali metal elements, so that the aim of increasing the NOx removal efficiency of the SNCR is fulfilled.

5. The advanced reburning denitration agent has wide application range, and can be applied to various boiler flues, such as power station boilers, waste incineration boilers, coke ovens and the like; and pollutants such as SO2 in the flue gas can be removed in an auxiliary manner during denitration.

Detailed Description