CN209828701U - Preparation facilities of mixed denitrifier based on aqueous ammonia + hydrazine - Google Patents

Abstract

The utility model discloses a preparation facilities of mixed denitrifier based on aqueous ammonia + hydrazine, including hydrazine storage tank (1), line mixer (3), spray gun system (4) and aqueous ammonia storage tank (5), store the hydrazine solution in the hydrazine storage tank, store the aqueous ammonia in the aqueous ammonia storage tank, the liquid outlet end of hydrazine storage tank and aqueous ammonia storage tank is connected with the feed liquor end of line mixer respectively, makes aqueous ammonia and hydrazine solution fully mix into mixed denitrifier in the line mixer; the liquid outlet end of the pipeline mixer is connected to the liquid inlet end of the spray gun system, the liquid outlet end of the spray gun system sprays the mixed denitration agent through a plurality of nozzles (41), and the plurality of nozzles are installed in the low smoke temperature hearth. The utility model discloses can prepare the denitrifier of being made by aqueous ammonia and hydrazine mixture, can adapt to great furnace temperature on a large scale when flue gas denitration operation, solve the denitration problem that low furnace temperature burns burning furnace under the prerequisite of not showing improve equipment investment and operation cost.

Description

Preparation device of mixed denitrification agent based on ammonia water + hydrazine

technical field

The utility model relates to a preparation device for a flue gas denitrification agent, in particular to a preparation device for a mixed denitrification agent based on ammonia water+hydrazine.

Background technique

With the development of social economy and technology, different types of incineration kilns and boilers are widely used in all walks of life, which brings about the generation of flue gas with different pollutant components and physical and chemical characteristics.

Part of the NO _X produced during the combustion process of boilers and incinerators comes from the decomposition and transformation of N-containing organic matter in fuel, and the other part comes from the nitrogen in the air produced under oxidizing atmosphere and high temperature conditions. NOx has various forms such as NO, NO ₂ , N ₂ O, N ₂ O ₃ , N ₂ O ₇ , etc. NOx in fuel incineration flue gas is dominated by NO, and its concentration increases rapidly with the increase of temperature. The longer the residence time, the more NO is produced. Low temperature is conducive to the formation of NO ₂ . Although NOx usually consists of 95% NO and 5% NO ₂ , it is generally calculated as 100% NO ₂ , because NO is converted into NO ₂ through photochemical reactions at temperatures below 200°C. According to the reaction type of nitrogen oxide production mechanism, it is divided into:

(1) Thermal type (thermal): refers to the process in which N ₂ and O ₂ in the air react to generate NOx under ambient conditions such as oxygen and temperature. When the combustion temperature is less than 1500°C, the amount of NO generated is very small; when it is greater than 1500°C, the reaction rate increases by 6 to 7 times for every 100°C increase. The formation principle of thermal NOx: 2N ₂ +3O ₂ →2NO ₂ (g)+2NO(g).

(2) Fuel type (fuel): refers to the process in which organic nitrogen in fuel is reduced to NH ₃ during combustion, and NH ₃ and O ₂ combine to form NOx. Since the N≡N bond energy of nitrogen molecules is much larger than the CN bond energy in organic matter, oxygen first breaks the CN bond to generate NOx, and the formation temperature is 600-800°C, and when it is greater than 900°C, it drops sharply, so the combustion temperature has little effect , while the influence of the excess air ratio is significant. When the excess air ratio α<1, the NOx conversion rate decreases significantly, and when α=0.7, the NOx conversion rate tends to 0. The principle of fuel NOx formation:

CxHyOzNw+O ₂ →CO ₂ +H ₂ O+NO ₂ +NO+incomplete combustion.

(3) Rapid type (prompt): During the combustion process, hydrocarbons are burned to generate NOx. It is also combined with the thermal type, collectively referred to as the thermal type.

At present, in addition to using technologies such as low-nitrogen combustion to reduce the amount of NO _X produced at the source, traditional flue gas denitrification technologies are mainly divided into SNCR (selective non-catalytic reduction) denitrification and SCR (selective catalytic reduction) denitrification. The difference is that Whether to use a catalyst to lower the reaction conditions. Generally, the widely used denitration agent is urea or ammonia water, which can reduce NO _x to N ₂ and water under certain reaction conditions.

The reaction conditions of SCR denitrification technology are relatively mild (the reaction can occur at 220°C using a low-temperature catalyst) and the _NOx removal rate is relatively high. However, if the SCR process is adopted, referring to the high-dust layout of the current mainstream process of coal-fired power plants, under the conditions of use such as biomass power plants, the high content of flue gas dust and alkali metals (Na, K) will cause SCR Catalyst wear, blockage, or pollution, poisoning, thereby greatly reducing the service life of the catalyst. Moreover, the investment in the SCR process system is relatively high, and the temperature of the flue gas after the bag filter is not enough to support the completion of the catalytic reduction reaction, and a large amount of steam must be used to raise the temperature, resulting in high operating costs. Therefore, SNCR with lower _NOx removal rate is still the best choice in many occasions.

The disadvantage of SNCR denitrification technology using urea or ammonia water lies in its relatively strict reaction temperature range: if ammonia water is used, the flue gas temperature needs to be controlled within the range of 850°C-1050°C, and the reaction time is longer than 1s; if urea is used, the temperature window needs to be adjusted Shift 50°C. In some application areas (such as pulverized coal furnace, glass kiln or smelting furnace), it is easier to realize, but in some conditions of low furnace temperature (such as biomass boiler and waste incinerator), the denitrification efficiency of SNCR is very low.

Contents of the invention

The purpose of this utility model is to provide a preparation device for a mixed denitrification agent based on ammonia water + hydrazine, which can prepare a denitrification agent made of a mixture of ammonia water and hydrazine, and can adapt to a wider range of furnace temperatures during flue gas denitrification operations. , to solve the denitrification problem of low furnace temperature incinerators without significantly increasing equipment investment and operating costs.

The utility model is achieved in that:

A preparation device for a mixed denitrification agent based on ammonia water + hydrazine, comprising a hydrazine storage tank, a pipeline mixer, a spray gun system and an ammonia water storage tank, the hydrazine storage tank stores hydrazine solution, the ammonia water storage tank stores ammonia water, and the hydrazine storage tank stores ammonia water. The liquid outlets of the ammonia storage tank and the ammonia water storage tank are respectively connected to the liquid inlet of the pipeline mixer, so that the ammonia water and hydrazine solution are fully mixed in the pipeline mixer to form a mixed denitrification agent; the liquid outlet of the pipeline mixer is connected to the spray gun The liquid inlet end of the system and the liquid outlet end of the spray gun system spray out the mixed denitration agent through several nozzles, and several nozzles are installed in the low-smoke temperature furnace.

The preparation device of the mixed denitrification agent based on ammonia + hydrazine also includes a nitrogen preparation system, which is connected with a hydrazine storage tank and a nozzle.

The spray gun system also includes several dosage distribution cabinets, and the diluted mixed denitration agent is correspondingly distributed to several nozzles through several dosage distribution cabinets.

The preparation device of the mixed denitrification agent based on ammonia + hydrazine also includes a desalted water storage tank, which stores desalted water, and the liquid outlet of the desalted water storage tank is connected to the hydrazine storage tank.

A medicament absorption tank is connected to the hydrazine storage tank.

Compared with the prior art, the utility model has the following beneficial effects:

1. The preparation device of the present invention adapts to different furnace temperatures and initial NO _X concentrations by adjusting the concentration and injection point of the mixed denitrification agent.

2. The preparation device of the present utility model is a fully enclosed structure, which ensures that no waste gas and waste water are discharged, and the leakage control is carried out through the alarm device to ensure the safety of use.

3. The preparation device of the utility model prevents the hydrazine solution from reacting with flue gas through nitrogen in the hydrazine storage tank, further improving the use safety of the hydrazine solution.

4. The mixed denitration agent prepared by the utility model is atomized by nitrogen gas in the spray gun, and is insensitive to the oxygen content in the low temperature zone of the furnace, which greatly enhances the reaction efficiency and reduces the stoichiometric ratio.

The utility model can prepare ammonia water + hydrazine mixed denitrification agent for the working condition of low furnace temperature or high initial NO _X , and the hydrazine used has strong reducibility, low reaction temperature window (600-750°C), and smoke The temperature range moves up when the oxygen content decreases, so that the mixed denitrification agent based on ammonia water and hydrazine greatly broadens the reaction temperature range of denitrification in the furnace, and at the same time prolongs the reaction time, without significantly increasing equipment investment and operating costs. Solve the denitrification problem of low furnace temperature incinerator.

Description of drawings

Fig. 1 is the front view of the preparation device of the mixed denitration agent based on ammonia water+hydrazine of the present invention;

Fig. 2 is the front view of the spray gun system of the preparation device of the mixed denitrification agent based on ammonia water + hydrazine of the present invention.

In the figure, 1 hydrazine storage tank, 2 nitrogen preparation system, 3 pipeline mixer, 4 spray gun system, 41 nozzle, 42 dosage distribution cabinet, 5 ammonia water storage tank, 6 demineralized water storage tank, 7 chemical absorption tank.

Detailed ways

Below in conjunction with accompanying drawing and specific embodiment the utility model is further described.

Please refer to accompanying drawings 1 and 2, a preparation device for a mixed denitrification agent based on ammonia water + hydrazine, including a hydrazine storage tank 1, a pipeline mixer 3, a spray gun system 4 and an ammonia water storage tank 5, and a hydrazine storage tank The hydrazine solution is stored in 1, the ammonia water is stored in the ammonia water storage tank 5, and the liquid outlets of the hydrazine storage tank 1 and the ammonia water storage tank 5 are respectively connected with the liquid inlet ends of the pipeline mixer 3, so that the ammonia water and the hydrazine solution are mixed in the pipeline Fully mixed into the mixed denitration agent in the device 3; the liquid outlet of the pipeline mixer 3 is connected to the liquid inlet of the spray gun system 4 through the spray gun distribution main pipe, and the liquid outlet of the spray gun system 4 sprays the mixed denitration agent through several nozzles 41. It can be seen that several nozzles 41 are installed in the low-smoke temperature furnace. Preferably, the nozzles 41 should be arranged so that the temperature of the area where the denitration agent is sprayed is most suitable for the denitration reaction, and the escaping ammonia has little influence on the corrosion of the heating surface of the boiler. .

The preparation device of the mixed denitrification agent based on ammonia + hydrazine also includes a nitrogen preparation system 2, which is connected to the hydrazine storage tank 1 and the nozzle 41, and can play a role of nitrogen protection in the hydrazine storage tank 1 function, to avoid serious safety accidents caused by the reaction of hydrazine with oxygen, nitrogen can also be used for mixing denitrification agent in the atomizing nozzle 41, preferably, the nozzle 41 can adopt a two-fluid atomizing nozzle.

The spray gun system 4 also includes several dosage distribution cabinets 42. The diluted mixed denitrification agent is correspondingly distributed to several nozzles 41 through the pipelines through several dosage distribution cabinets 42, and the sprayed amount of each nozzle 41 can be precisely controlled. dose.

The preparation device of the mixed denitrification agent based on ammonia + hydrazine also includes a desalted water storage tank 6, which stores desalted water, and the outlet end of the desalted water storage tank 6 is connected to the hydrazine storage tank 1 through a pipeline. , can be used to add desalted water into the hydrazine solution, adjust the ratio of desalted water according to the required concentration, mix it with the hydrazine solution in the hydrazine storage tank 1 and fully dissolve it, pump it out of the hydrazine storage tank 1, and Mix well with ammonia solution in pipeline mixer 3. When the system is running, it is pumped to the spray gun system 4 through the denitration agent delivery pump.

The hydrazine storage tank 1 is connected with a medicament absorption tank 7. Since every time the hydrazine storage tank 1 is added with a medicament, the air above the liquid level is discharged, and the air contains volatilized hydrazine. So it can't be directly emptied, and it needs to be led to the medicament absorption tank 7 to absorb hydrazine. The absorption method is that the exhaust pipe extends below the liquid level of the absorbent, and absorbs during the rising process of the bubbles. Preferably, the connection between the drug absorption tank 7 and the hydrazine storage tank 1 can be flanged.

According to the initial concentration of nitrogen oxides in the furnace flue gas and the required removal efficiency, a mixed denitration agent solution with the required concentration is prepared and adjusted as needed. Considering the toxicity of hydrazine, and its high vapor pressure and smoke characteristics, in the preparation device of the mixed denitrification agent based on ammonia water + hydrazine, all connecting pipes, pump bodies, storage tanks, etc. adopt fully enclosed structures and Fully enclosed delivery to ensure no waste gas and waste water discharge, and a leakage alarm device is installed at the point where drug escape may occur, which is used to send the alarm to the external PLC/DCS control system, and the leakage is controlled through interlocking action.

The mixed denitration agent based on ammonia water+hydrazine produced by the preparation device of the present invention is formed by uniformly mixing ammonia water and hydrazine solution. The mass fraction of ammonia water is 25%-65%, and the mass fraction of hydrazine solution in the mixed denitration agent is 35%-75%. If the flue temperature is higher than 750°C, according to the required denitrification efficiency, the amount of hydrazine solution used can be appropriately reduced and the proportion of ammonia water can be increased. The utility model says that the mass concentration of the ammonia liquor that adopts is 20%, and the mass concentration of the hydrazine solution is 40%.

The mixed denitrification agent based on ammonia water + hydrazine prepared by the utility model is applied in the flue gas denitrification method, and its specific steps are: in the case of low smoke temperature (550-750 ° C), the ammonia water + hydrazine is prepared by the preparation device Mix the denitrification agent and pump it into the nozzle 41 of the spray gun system 4. The mixed denitrification agent is atomized by compressed nitrogen in the nozzle 41 and sprayed in the furnace for denitrification reaction. By adjusting the concentration and injection point of the mixed denitrification agent, it can adapt to different furnaces. Temperature and initial _NOx concentration.

Under the condition of lower smoke temperature, the utility model adopts the chemical formula of denitration reaction after mixing ammonia water and hydrazine solution as follows:

Ammonia: 4NH ₃ +4NO+O ₂ →4N ₂ +6H ₂ O

Hydrazine: N ₂ H ₄ +2NO→2N ₂ +2H ₂ O

The scheme of the present utility model can also be applied to the SNCR using urea. After mixing urea and hydrazine solution, denitrification reaction is carried out. The chemical reaction of urea and hydrazine solution in the furnace is as follows:

Urea: N ₂ H ₄ CO+2NO→2N ₂ +2H ₂ O+CO

Hydrazine: N ₂ H ₄ +2NO→2N ₂ +2H ₂ O

Since the hydrazine solution and ammonia water are fully mixed in the pipeline mixer 3 before use, and are atomized by the nitrogen gas prepared by the nitrogen gas preparation system 2 in the spray gun system 4, they are not sensitive to the oxygen content in the low temperature zone of the furnace, which can greatly reduce the The temperature requirement of the denitrification reaction greatly enhances the reaction efficiency, reduces the stoichiometric ratio, and improves the denitrification efficiency.

Example 1: Biomass Circulating Fluidized Bed Boiler Flue Gas Denitrification

When a circulating fluidized bed biomass boiler does not take any measures, the NOx emission concentration is between 120-150mg/ ^Nm3 ; in most cases, it is above 130mg/ ^Nm3 ; the temperature inside the furnace is between 600-700℃, The flue gas temperature before the panel superheater is 550°C. The excess air coefficient at the furnace outlet is about 1.4; the SNCR denitrification measures using ammonia water as the denitrification agent are adopted. When the stoichiometric ratio of NH ₃ : NOx = 1.5, the concentration of NOx in the exhaust gas is still between 120 and 140 mg/Nm ³ , almost no denitrification effect, can not meet the latest standard NOx emissions lower than 100mg/Nm ³ requirements; adopt the hybrid denitrification agent of the present utility model, only add hydrazine solution (concentration is 40wt%) in the original ammonia water system, after mixing as The ratio of denitrification agent and ammonia water N is 50%; denitrification agent: the stoichiometric ratio of NOx is 1.2 (based on 150mg/ ^Nm3 ); the temperature of the measuring point behind the nozzle, the volume concentration of oxygen, and the The NOx emissions are shown in Table 1.

Table 1 The denitrification efficiency when the mixture of ammonia water and hydrazine is used as the denitrification agent in the furnace

Under the condition of relatively low furnace temperature, using the mixed denitrification agent of the utility model can make the denitrification efficiency meet the emission requirements, and there is no NH ₃ escape in the flue gas.

Embodiment 2: Biomass grate furnace boiler flue gas denitrification

When no measures are taken for a biomass grate furnace boiler, the NOx emission concentration is between 220-250mg/ ^Nm3 ; in most cases, it is above 230mg/ ^Nm3 ; the temperature inside the furnace is between 730-870℃, and the screen The flue gas temperature before the type superheater is 750°C. The excess air coefficient at the furnace outlet is about 1.4; the SNCR denitrification measures using ammonia water as the denitrification agent are adopted. When the stoichiometric ratio of NH ₃ : NOx = 1.8, the concentration of NOx in the exhaust gas is still between 120 and 150mg/Nm ³ , can not meet the requirement that the latest standard NOx discharge is lower than 100mg/Nm ³ ; adopt the mixed denitrification agent of the present invention, only add hydrazine solution (concentration is 40wt%) in the original ammonia water system, mix it as denitrification agent, ammonia water N The proportion is 80%; denitrification agent: the chemical equivalent ratio of NOx is 1.2 (based on 250mg/Nm ³ ); see Table 2.

Table 2 Denitrification efficiency when ammonia water and hydrazine mixture are used as denitrification agents in the furnace

It can be seen from the table that after the denitrification reaction is carried out with the mixed denitrification agent of the present invention, not only the emission is completely up to the standard, but also there is no NH ₃ escape in the flue gas.

Example 3: Flue gas denitrification of garbage circulating fluidized bed boiler

The original nitrogen oxide concentration of a garbage circulating fluidized bed boiler is 300mg/Nm ³ , the denitrification process adopts SNCR, and urea solution (40% mass concentration) is used as the reducing agent, and the denitrification efficiency is designed to be 35%. The experiment adopts the mixed denitrification agent of the present utility model as the reducing agent, the mass fraction of the ammonia solution (20% mass concentration) in the mixed denitrification agent is 80%, the mass fraction of the hydrazine solution (40% mass concentration) is 20%, and the mixed denitrification agent The stoichiometric ratio of agent to nitrogen oxide is 1.2, and the experimental data are shown in Table 3:

Table 3: Denitrification efficiency when the mixture of ammonia water and hydrazine is used as the denitrification agent in the furnace

It can be seen from the table that under the same conditions, using the mixed denitrification agent of the present invention can greatly improve the denitrification efficiency, and there is no problem of ammonia escape.

Example 4: Denitrification of flue gas from garbage grate furnace boiler

The original nitrogen oxide concentration of a garbage grate furnace boiler in Jiangsu is 400-600mg/Nm ³ , the denitrification process adopts SNCR, and ammonia water is used as the reducing agent. The design denitrification efficiency is 55%. 200mg/Nm ³ , but due to the large instantaneous fluctuation of the original nitrogen oxide concentration, the nitrogen oxide emission concentration cannot meet the standard stably, so measures need to be taken to make the flue gas discharge stably meet the standard. Using ammonia water/hydrazine solution as reducing agent, the mass fraction of ammonia solution (20% mass concentration) in the mixed denitrification agent is 90%, the mass fraction of hydrazine solution (40% mass concentration) is 10%, and the mixed denitrification agent and nitrogen oxides are stoichiometric The ratio is 1, and the experimental data are shown in Table 4:

Table 4: Denitrification efficiency when the mixture of ammonia water and hydrazine is used as the denitrification agent in the furnace

It can be seen from the table that the mixed denitrification agent of the present invention can also achieve a higher denitrification level in a relatively high temperature range when the mass fraction of hydrazine is very small.

The above are only preferred embodiments of the utility model, and are not used to limit the scope of protection of the utility model. Therefore, any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the utility model shall include Within the protection scope of the present utility model.

Claims (5)

1. A preparation device based on the mixed denitration agent of ammonia + hydrazine, characterized in that it comprises a hydrazine storage tank (1), a pipeline mixer (3), a spray gun system (4) and an ammonia storage tank (5), The hydrazine solution is stored in the hydrazine storage tank (1), the ammonia water is stored in the ammonia storage tank (5), and the liquid outlets of the hydrazine storage tank (1) and the ammonia storage tank (5) are connected with the pipeline mixer (3) respectively. The liquid inlet is connected so that ammonia water and hydrazine solution are fully mixed into a mixed denitration agent in the pipeline mixer (3); the liquid outlet of the pipeline mixer (3) is connected to the liquid inlet of the spray gun system (4), and the spray gun system The liquid outlet of (4) sprays the mixed denitration agent through several nozzles (41), and the several nozzles (41) are installed in the low-smoke temperature furnace. 2. The preparation device of the mixed denitrification agent based on ammonia water+hydrazine according to claim 1, characterized in that: the preparation device of the mixed denitrification agent based on ammonia water+hydrazine also includes a nitrogen preparation system (2), The nitrogen preparation system (2) is connected with the hydrazine storage tank (1) and the nozzle (41). 3. the preparation device based on the mixed denitrification agent of ammonia water+hydrazine according to claim 1 or 2, is characterized in that: described spray gun system (4) also comprises several dose distribution cabinets (42), the diluted The mixed denitration agent is correspondingly distributed to several nozzles (41) through several dosage distribution cabinets (42). 4. The preparation device of the mixed denitrification agent based on ammonia water+hydrazine according to claim 1, characterized in that: the preparation device of the mixed denitrification agent based on ammonia water+hydrazine also includes a demineralized water storage tank (6) , the desalted water storage tank (6) stores desalted water, and the liquid outlet end of the desalted water storage tank (6) is connected to the hydrazine storage tank (1). 5 . The preparation device for a mixed denitrification agent based on ammonia + hydrazine according to claim 1 , characterized in that: the hydrazine storage tank ( 1 ) is connected with a chemical absorption tank ( 7 ).