CN114272752A - Organic coated denitration agent and preparation method thereof - Google Patents
Organic coated denitration agent and preparation method thereof Download PDFInfo
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Abstract
The invention provides an organic coated denitration agent and a preparation method thereof, wherein the preparation method comprises the following steps: melting urea, mixing with a catalyst, and granulating to obtain spherical particles; and putting the obtained spherical particles into coating equipment, uniformly rotating the spherical particles, and spraying isocyanate and polyol to coat to obtain the organic coated denitration agent. According to the method, the catalyst is added in the urea denitration agent forming process, so that the distribution of the catalyst in each local area is ensured when the denitration agent is used, the denitration effect is improved, and the denitration efficiency is improved; the method carries out surface modification on the surface of the molded particle in a coating mode to form a polyurethane polymer film, has a slow release effect, reduces ineffective decomposition of urea in a denitration process, fully uses the urea for reduction of nitric oxide, and improves the utilization rate of the urea; the method has the advantages of simple operation steps, wide raw material source, low equipment investment and production cost and easy industrial implementation.
Description
Technical Field
The invention belongs to the technical field of flue gas denitration, and relates to an organic coated denitration agent and a preparation method thereof.
Background
With the rapid development of economy and the improvement of living standard, coal-fired units are in a growing trend, the problem of air pollution caused by the growth of the coal-fired units is gradually aggravated, and the removal of nitrogen oxides in coal-fired flue gas is the key point for preventing environmental pollution, so that flue gas denitration technology is the key point of current research and application, and the current mainstream denitration technology mainly comprises Selective Catalytic Reduction (SCR) denitration and selective non-catalytic reduction (SNCR), wherein the former means that a reducing agent and NO in flue gas are subjected to the action of a catalystxReact to generate harmless nitrogen and water, thereby removing NO in the flue gasxThe method has the advantages of low reaction temperature and high denitration efficiency, but has the defects of large equipment investment, easy inactivation of the catalyst, high price and the like; the latter does not need catalyst, but the treatment temperature is higher, and the denitration efficiency is lower.
In the denitration process, in addition to the catalyst, the selection of the reducing agent is also a key factor, and the commonly used denitration agent is mainly ammonia, but in many cases, the denitration agent is not suitable for using a gas-phase denitration agent, but needs to be used as a solid-phase denitration agent, urea is one of the solid-phase denitration agents frequently selected, and urea is unstable and easy to decompose at a high temperature, so that the required addition amount is large, the loss is also large, and the urea needs to be modified to improve the utilization rate of the urea in order to control the use amount of the urea.
CN 109224801A discloses a flue gas denitration agent, which comprises the following components: 2-12 parts of activated carbon, 1-9 parts of potassium permanganate, 15-25 parts of rhodochrosite, 2-12 parts of magnesium oxide, 0.2-3.8 parts of silicon oxide, 24.5-34.5 parts of urea and 24.5-34.5 parts of sodium carbonate, wherein the parts are all parts by weight. The activated carbon in the denitrifier can enhance the adsorption effect of the denitrifier, and the urea plays the role of a reducing agent, and reacts with the urea to generate NH3All can react with NOxThe reaction has the effect of denitration, but the urea accounts for the denitration agentThe urea is low in content, the urea still has the problem of self decomposition, the required addition amount is large, secondary pollution is easy to cause, and the solid waste amount is large.
CN 108057326A discloses a preparation method of a slow-release flue gas denitration agent, which takes 3, 3' -diaminobenzidine, 3, 4-diaminobenzoic acid and isophthalic acid as precursors, takes polyphosphoric acid as a solvent, synthesizes polybenzimidazole copolymer at low temperature through catalysis under the irradiation of ultraviolet light, and then coats urea to prepare the flue gas denitration agent with the slow-release function; the focus of this process is on the preparation of polybenzimidazole copolymers, and there is no explicit description of how to coat urea.
In summary, for the preparation and use of the solid-phase denitration agent, improvement of the solid-phase raw material such as urea and the like is needed, so that the solid-phase raw material has better heat resistance, and the ineffective decomposition of the solid-phase raw material at high temperature is avoided, thereby improving the utilization rate and reducing the cost.
Disclosure of Invention
Aiming at the problems in the prior art, the invention aims to provide an organic coated denitration agent and a preparation method thereof, wherein the catalyst is added in the urea denitration agent forming process, so that the denitration efficiency can be correspondingly improved, and the problem of reduction of the denitration efficiency caused by larger particle size is avoided; meanwhile, the surface of the molded particles is modified in a coating mode to form a polymer film, so that the heat resistance of the polymer film is improved, the ineffective decomposition of urea at the denitration temperature is effectively slowed down, and the utilization rate of the urea is improved.
In order to achieve the purpose, the invention adopts the following technical scheme:
in one aspect, the invention provides a preparation method of an organic coated denitration agent, which comprises the following steps:
(1) melting urea, mixing with a catalyst, and granulating to obtain spherical particles;
(2) and (2) putting the spherical particles obtained in the step (1) into coating equipment, uniformly rotating the spherical particles, and spraying isocyanate and polyol to coat the spherical particles to obtain the organic coated denitration agent.
In the invention, for the preparation and application of the denitration agent, the utilization rate and the denitration efficiency of the denitration agent are considered, in order to ensure the uniform mixing of urea and the catalyst, the urea is firstly formed into a molten state and then mixed with the denitration catalyst for molding, so that the denitration agent can react in each local area when in use, and the denitration efficiency is improved; meanwhile, urea is decomposed at the denitration temperature, the surface of the urea molding particles is modified in a coating mode to form a polyurethane polymer film, and the polyurethane polymer film has heat resistance, can slow down ineffective decomposition of urea, is fully used for reduction of nitric oxide, and improves the utilization rate of urea; the method has the advantages of simple operation steps, wide raw material source, low equipment investment and production cost and easy industrial implementation.
The following technical solutions are preferred technical solutions of the present invention, but not limited to the technical solutions provided by the present invention, and technical objects and advantageous effects of the present invention can be better achieved and achieved by the following technical solutions.
As a preferred embodiment of the present invention, the urea melting conditions in the step (1) are: the temperature is 132 to 140 ℃, for example 132 ℃, 134 ℃, 135 ℃, 136 ℃, 137 ℃ or 140 ℃, but is not limited to the recited values, and other values not recited in the range of the values are also applicable.
Preferably, the atmosphere in the urea melting in the step (1) is air.
In the invention, as the urea is likely to be decomposed during heating, the process conditions are controlled to ensure that the urea is molten, so that the urea is convenient to mix and form with the denitration catalyst.
As a preferred technical scheme of the invention, the catalyst in the step (1) comprises transition metal oxide.
Preferably, the transition metal oxide comprises any one of copper oxide, iron oxide or manganese dioxide or a combination of at least two of these, typical but non-limiting examples being: copper oxide and iron oxide, iron oxide and manganese dioxide, copper oxide, iron oxide and manganese dioxide, and the like.
Preferably, the catalyst of step (1) is independently added in an amount of 0 to 500ppm, such as 0, 50ppm, 100ppm, 200ppm, 300ppm, 400ppm or 500ppm, but not limited to the recited values, and other values not recited within the range of values are equally applicable.
In the invention, the catalyst is added mainly to ensure that the catalyst exists in the reaction zone when the urea reacts with the nitrogen oxide, so that the problem of uneven denitration reaction is avoided, the adding amount of the catalyst does not need to be excessive, and the main body of the catalyst is still the urea denitration agent.
As a preferable technical scheme of the invention, the mixture in the step (1) is stirred uniformly.
Preferably, the granulation molding in the step (1) is carried out in a granulation device.
Preferably, the temperature for the granulation molding in step (1) is 95 to 115 ℃, for example, 95 ℃, 100 ℃, 105 ℃, 110 ℃ or 115 ℃, but is not limited to the recited values, and other values not recited in the range of the values are also applicable.
In the invention, the granulation molding adopts a fluidized bed granulation mode, the molten urea is pressurized and sprayed to the surface of the urea seed crystal to grow the required urea particles, and the temperature is the operating temperature of the fluidized bed.
Preferably, the spherical particles of step (1) have a particle size of 2 to 5mm, such as 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, or 5mm, but not limited to the recited values, and other values not recited within the range of values are also applicable.
As a preferable technical scheme, the coating equipment in the step (2) comprises a coating machine, and the coating machine comprises a drum assembly.
Preferably, the speed of rotation of the drum is 20 to 50r/min, such as 20r/min, 25r/min, 30r/min, 35r/min, 40r/min or 50r/min, but not limited to the values listed, and other values not listed in this range are equally applicable.
Preferably, the spherical particles follow the drum uniformly.
As a preferred embodiment of the present invention, the isocyanate in step (2) comprises any one of toluene diisocyanate, diphenylmethane diisocyanate or dicyclohexylmethane diisocyanate, or a combination of at least two of them, and the combination is exemplified by, but not limited to: combinations of toluene diisocyanate and diphenylmethane diisocyanate, combinations of diphenylmethane diisocyanate and dicyclohexylmethane diisocyanate, combinations of toluene diisocyanate, diphenylmethane diisocyanate, and dicyclohexylmethane diisocyanate, and the like.
Preferably, the polyol of step (2) comprises a polyether polyol and/or a polyester polyol.
In the present invention, the isocyanate is selected from diisocyanate, including toluene diisocyanate, diphenylmethane diisocyanate, and minor species of isocyanates such as: dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, 1, 5-naphthalene diisocyanate, and the like; the polyols are mainly classified into polyether polyols and polyester polyols according to the difference of functional groups, and the commonly used polyether polyols include polypropylene glycol, polyethylene glycol and the like, and the commonly used polyester polyols include butanediol adipate polyester glycol, polycarbonate polyol and the like.
Preferably, the isocyanate and the polyol are sprayed in the sequence of step (2): the isocyanate is sprayed first and then the polyol.
In the invention, the isocyanate and the polyol are sprayed in sequence according to the following steps: the isocyanate is active in chemical property and is easier to react with moisture in the air at high temperature, and if the isocyanate is sprayed on the outermost layer of the urea particles, the dosage of the isocyanate is increased and the formed denitration agent is adhered, so that the isocyanate is sprayed at room temperature, then the polyol is sprayed, and finally the heating and coating are carried out.
In a preferred embodiment of the present invention, the total amount of the isocyanate and the polyol added in step (2) is 0.3 to 5.0 wt% of the spherical particles, for example, 0.3 wt%, 0.6 wt%, 1.0 wt%, 1.5 wt%, 2.0 wt%, 3.0 wt%, 4.0 wt%, or 5.0 wt%, but is not limited to the above-mentioned values, and other values not listed in the above-mentioned range are also applicable.
In the invention, the addition amount of the isocyanate and the polyol is an important factor influencing the formation and the characteristics of the polyurethane film, if the total addition amount of the isocyanate and the polyol is too much, the coating outside the urea is too thick, the relative content of the urea is less, the urea is slowly released, the flue gas denitration rate is influenced, the manufacturing cost of the denitration agent is also improved, and if the total addition amount of the isocyanate and the polyol is too little, the coating outside the urea particles is incomplete, the slow release effect of the urea is weaker, the invalid decomposition is easily caused, and the consumption of the denitration agent in the denitration process is increased.
Preferably, the isocyanate and the polyol in step (2) are present in a mass ratio of 1:0.9 to 1:4.0, such as 1:0.9, 1:1.0, 1:1.2, 1:1.5, 1:2.0, 1:2.5, 1:2.8, 1:3.0, 1:3.5 or 1:4.0, but not limited to the recited values, and other values not recited within this range are equally applicable, preferably 1:1.0 to 1: 3.0.
In a preferred embodiment of the present invention, the temperature of the coating film in the step (2) is 60 to 100 ℃, for example, 60 ℃, 65 ℃, 70 ℃, 75 ℃, 80 ℃, 85 ℃, 90 ℃ or 100 ℃, but is not limited to the above-mentioned values, and other values not shown in the above-mentioned range of values are also applicable.
Preferably, hot air is introduced during the coating in the step (2) to maintain the coating temperature.
Preferably, the coating time in step (2) is 0.25 to 1 hour, such as 0.25 hour, 0.33 hour, 0.4 hour, 0.5 hour, 0.6 hour, 0.75 hour, 0.9 hour or 1 hour, but not limited to the recited values, and other values not recited in the range of the values are also applicable.
Preferably, unloading and air-drying are carried out after the coating is finished, so as to obtain the polymer denitration agent.
As a preferred technical scheme of the invention, the preparation method comprises the following steps:
(1) mixing melted urea with a catalyst, wherein the temperature of the melted urea is 132-140 ℃, the catalyst comprises transition metal oxide, the addition amount of the transition metal oxide is 0-500 ppm, the mixture is uniformly stirred and then put into granulation equipment, and granulation molding is carried out, wherein the temperature of the granulation molding is 95-115 ℃, spherical particles are obtained, and the particle size of the spherical particles is 2-5 mm;
(2) putting the spherical particles obtained in the step (1) into a coating machine, wherein the rotating speed of a rotating cylinder in the coating machine is 20-50 r/min, uniformly rotating the spherical particles, and then sequentially spraying isocyanate and polyol for coating, wherein the isocyanate comprises any one or a combination of at least two of toluene diisocyanate, diphenylmethane diisocyanate or dicyclohexylmethane diisocyanate, the polyol comprises polyether polyol and/or polyester polyol, the total adding amount of the polyether polyol and the polyester polyol accounts for 0.3-5.0 wt% of the spherical particles, the mass ratio of the polyether polyol to the polyester polyol is 1: 1.0-1: 3.0, the coating temperature is 60-100 ℃, hot air is introduced during coating to maintain the coating temperature, the coating time is 0.25-1 h, and the organic coating denitration agent is obtained after coating.
On the other hand, the invention provides the organic coated denitration agent prepared by the preparation method.
Compared with the prior art, the invention has the following beneficial effects:
(1) according to the method, the catalyst is added in the urea denitration agent forming process, so that the distribution of the catalyst in each local area is ensured when the denitration agent is used, the denitration effect is improved, and the denitration rate can reach more than 94%;
(2) according to the method, the surface of the urea molding particles is modified in a coating mode to form the polyurethane polymer film, so that the slow release effect is achieved, the ineffective decomposition of urea in the denitration process is reduced, the urea is fully used for reducing nitric oxide, and the utilization rate of the urea is improved;
(3) the method has the advantages of simple operation steps, wide raw material source, low equipment investment and production cost and easy industrial implementation.
Detailed Description
In order to better illustrate the present invention and facilitate the understanding of the technical solutions of the present invention, the present invention is further described in detail below. However, the following examples are only simple examples of the present invention and do not represent or limit the scope of the present invention, which is defined by the claims.
The specific embodiment of the invention provides an organic coated denitration agent and a preparation method thereof, wherein the preparation method comprises the following steps:
(1) melting urea, mixing with a catalyst, and granulating to obtain spherical particles;
(2) and (2) putting the spherical particles obtained in the step (1) into coating equipment, uniformly rotating the spherical particles, and spraying isocyanate and polyol to coat the spherical particles to obtain the organic coated denitration agent.
The following are typical but non-limiting examples of the invention:
example 1:
the embodiment provides a preparation method of an organic coated denitration agent, which comprises the following steps:
(1) melting urea, mixing the urea with a catalyst, wherein the melting temperature of the urea is 132 ℃, the melting is carried out in the atmosphere of normal pressure air, the catalyst is copper oxide, the adding amount of the catalyst is 500ppm, the urea is uniformly stirred and then put into granulation equipment, and the granulation molding is carried out at the temperature of 95 ℃ to obtain spherical particles, and the average particle size of the spherical particles is 3 mm;
(2) putting the spherical particles obtained in the step (1) into a coating machine, wherein the rotating speed of a rotating cylinder in the coating machine is 40r/min, uniformly rotating the spherical particles, and then sequentially spraying isocyanate and polyol for coating, wherein the isocyanate is diphenylmethane diisocyanate, the polyol is polyethylene glycol, the total adding amount of the isocyanate and the polyol accounts for 1.0 wt% of the spherical particles, the mass ratio of the isocyanate to the polyol is 1:2, the temperature of the coating is 80 ℃, hot air is introduced during coating to maintain the coating temperature, the coating time is 0.5h, and the organic coating denitration agent is obtained after coating is completed.
Example 2:
the embodiment provides a preparation method of an organic coated denitration agent, which comprises the following steps:
(1) melting urea, mixing the urea with a catalyst, wherein the melting temperature of the urea is 134 ℃, the melting is carried out in the atmosphere of normal pressure air, the catalyst is copper oxide and ferric oxide, the adding amount of the copper oxide and the ferric oxide is 200ppm, the adding amount of the ferric oxide and the adding amount of the cupric oxide is 100ppm, uniformly stirring, putting into granulation equipment, and carrying out granulation molding, wherein the granulation molding temperature is 115 ℃, so that spherical particles are obtained, and the average particle size of the spherical particles is 2 mm;
(2) putting the spherical particles obtained in the step (1) into a coating machine, wherein the rotating speed of a rotating cylinder in the coating machine is 30r/min, uniformly rotating the spherical particles, and then sequentially spraying isocyanate and polyol for coating, wherein the isocyanate is toluene diisocyanate, the polyol is polypropylene glycol, the total adding amount of the isocyanate and the polyol accounts for 3.0 wt% of the spherical particles, the mass ratio of the isocyanate to the polyol is 1:3, the temperature of the coating is 60 ℃, hot air is introduced during coating to maintain the coating temperature, the coating time is 0.75h, and the organic coating denitration agent is obtained after coating is completed.
Example 3:
the embodiment provides a preparation method of an organic coated denitration agent, which comprises the following steps:
(1) melting urea, mixing the melted urea with a catalyst, wherein the melting temperature of the urea is 140 ℃, the melting is carried out in the atmosphere of normal pressure air, the catalyst is copper oxide, ferric oxide and manganese dioxide, the adding amount of the catalyst is 200ppm, the catalyst is uniformly stirred and then is put into granulation equipment, and granulation molding is carried out, wherein the granulation molding temperature is 100 ℃, so that spherical particles are obtained, and the average particle size of the spherical particles is 4 mm;
(2) putting the spherical particles obtained in the step (1) into a coating machine, wherein the rotating speed of a rotating cylinder in the coating machine is 50r/min, uniformly rotating the spherical particles, and then sequentially spraying isocyanate and polyol for coating, wherein the isocyanate is diphenylmethane diisocyanate, the polyol is polypropylene glycol, the total adding amount of the isocyanate and the polyol accounts for 5.0 wt% of the spherical particles, the mass ratio of the isocyanate to the polyol is 1:1.5, the coating temperature is 100 ℃, hot air is introduced during coating to maintain the coating temperature, the coating time is 0.3h, and the organic coating denitration agent is obtained after coating is completed.
Example 4:
the embodiment provides a preparation method of an organic coated denitration agent, which comprises the following steps:
(1) melting urea, mixing the urea with a catalyst, wherein the melting temperature of the urea is 136 ℃, the melting is carried out in the atmosphere of normal pressure air, the catalyst is manganese dioxide, the adding amount of the manganese dioxide is 400ppm, the manganese dioxide is uniformly stirred and then put into granulation equipment, and granulation molding is carried out, wherein the granulation molding temperature is 105 ℃, so that spherical particles are obtained, and the average particle size of the spherical particles is 3.5 mm;
(2) putting the spherical particles obtained in the step (1) into a coating machine, wherein the rotating speed of a rotating cylinder in the coating machine is 25r/min, uniformly rotating the spherical particles, and then sequentially spraying isocyanate and polyol for coating, wherein the isocyanate is dicyclohexylmethane diisocyanate, the polyol is adipic acid butanediol polyester glycol, the total adding amount of the isocyanate and the polyol accounts for 0.6 wt% of the spherical particles, the mass ratio of the isocyanate to the polyol is 1:1, the coating temperature is 90 ℃, hot air is introduced during coating to maintain the coating temperature, the coating time is 0.6h, and the organic coating denitration agent is obtained after coating.
Example 5:
the embodiment provides a preparation method of an organic coated denitration agent, which comprises the following steps:
(1) melting urea, mixing the urea with a catalyst, wherein the melting temperature of the urea is 135 ℃, the melting is carried out in the atmosphere of normal pressure air, the catalyst is ferric oxide and manganese dioxide, the addition amount of the ferric oxide and the manganese dioxide is 500ppm, the urea is uniformly stirred and then put into granulation equipment, and the granulation molding is carried out at the temperature of 100 ℃ to obtain spherical particles, wherein the average particle size of the spherical particles is 5 mm;
(2) putting the spherical particles obtained in the step (1) into a coating machine, wherein the rotating speed of a rotating cylinder in the coating machine is 35r/min, uniformly rotating the spherical particles, and then sequentially spraying isocyanate and polyol for coating, wherein the isocyanate is dicyclohexylmethane diisocyanate, the polyol is polycarbonate polyol, the total adding amount of the isocyanate and the polyol accounts for 2.0 wt% of the spherical particles, the mass ratio of the isocyanate to the polyol is 1:2.5, the coating temperature is 70 ℃, hot air is introduced during coating to maintain the coating temperature, the coating time is 0.8h, and the organic coating denitration agent is obtained after coating.
Example 6:
the embodiment provides a preparation method of an organic coated denitration agent, which comprises the following steps:
(1) melting urea, mixing the melted urea with a catalyst, wherein the melting temperature of the urea is 137 ℃, the melting is carried out in the atmosphere of normal pressure air, the catalyst is copper oxide and manganese dioxide, the addition amount of the copper oxide and the manganese dioxide is 100ppm, the mixture is uniformly stirred and then put into granulation equipment, and the granulation molding is carried out, wherein the granulation molding temperature is 110 ℃, so that spherical particles are obtained, and the average particle size of the spherical particles is 2.5 mm;
(2) putting the spherical particles obtained in the step (1) into a coating machine, wherein the rotating speed of a rotating cylinder in the coating machine is 45r/min, uniformly rotating the spherical particles, and then sequentially spraying isocyanate and polyol for coating, wherein the isocyanate is toluene diisocyanate and diphenylmethane diisocyanate in a mass ratio of 1:1, the polyol is polypropylene glycol, the total adding amount of the isocyanate and the polyol accounts for 4.0 wt% of the spherical particles, the mass ratio of the isocyanate to the polyol is 1:3.5, the coating temperature is 75 ℃, hot air is introduced during coating to maintain the coating temperature, the coating time is 0.4h, and the organic coated denitration agent is obtained after coating is completed.
Example 7:
this example provides a method for preparing an organic coated denitration agent, which is similar to that of example 4 except that: the total amount of isocyanate and polyol added in step (2) accounted for 0.2 wt% of the spherical particles.
Example 8:
this example provides a method for preparing an organic coated denitration agent, which is similar to that of example 5 except that: the total amount of isocyanate and polyol added in step (2) accounted for 6.0 wt% of the spherical particles.
Comparative example 1:
this comparative example provides a preparation method of an organic coated denitration agent, which is similar to that of example 1 except that: no catalyst is added in the step (1).
Comparative example 2:
this comparative example provides a preparation method of a denitration agent, which is similar to that of example 1 except that: the coating in step (2) is not performed.
The above examples 1 to 8 and comparative example 1 were combined to giveThe organic coated denitration agent and the denitration agent obtained in the comparative example 2 are used for denitration application tests, and the test conditions comprise that: the reaction temperature is 700-750 ℃, and NO in the flue gas to be treatedxAt a concentration of 410mg/Nm3Testing NO in the outlet flue gasxThe denitration rate was calculated from the concentration of (b), and the results are shown in table 1.
TABLE 1 test results of denitration agent denitration application described in examples 1 to 8 and comparative examples 1 to 2
From the results in table 1, it can be seen that the organic coated denitration agent prepared by the method of the present invention has a denitration rate of 94% or more according to the results of examples 1 to 6; in example 7, too little polyurethane polymer coating results in incomplete coating of the molded particles, which is likely to cause ineffective decomposition of urea and decrease of denitration rate; in example 8, the denitration rate was not significantly increased due to the excessive coating weight of the polyurethane polymer, but rather the denitration rate was lower and the cost was increased.
In the comparative example 1, no catalyst is added during urea forming, the denitration agent cannot achieve a sufficient denitration effect at a low temperature of 700-750 ℃, and the denitration rate is reduced to 79.27%; in comparative example 2, the polyurethane film was not coated, and urea was also decomposed in a large amount during the denitration reaction, resulting in a decrease in the urea utilization rate, and the urea used for denitration was less, and the denitration rate was also significantly decreased to 74.39%.
By integrating the embodiment and the comparative example, the method provided by the invention has the advantages that the catalyst is added in the urea denitration agent forming process, the distribution of the catalyst in each local area is ensured when the denitration agent is used, the denitration effect is improved, and the denitration rate can reach more than 94%; according to the method, the surface of the urea molding particles is modified in a coating mode to form a polyurethane polymer film, so that the slow release effect is achieved, the ineffective decomposition of urea in the denitration process is reduced, the urea is fully used for reducing nitric oxide, and the utilization rate of the urea is improved; the method has the advantages of simple operation steps, wide raw material source, low equipment investment and production cost and easy industrial implementation.
The present invention is illustrated in detail by the examples described above, but the present invention is not limited to the details described above, i.e., it is not intended that the present invention be implemented by relying on the details described above. It will be apparent to those skilled in the art that any modification, equivalent substitution of the process of the invention and addition of ancillary operations, selection of specific means, etc., of the present invention are within the scope and disclosure of the invention.
Claims (10)
1. The preparation method of the organic coated denitration agent is characterized by comprising the following steps:
(1) melting urea, mixing with a catalyst, and granulating to obtain spherical particles;
(2) and (2) putting the spherical particles obtained in the step (1) into coating equipment, uniformly rotating the spherical particles, and spraying isocyanate and polyol to coat the spherical particles to obtain the organic coated denitration agent.
2. The preparation method according to claim 1, wherein the temperature of the urea melt in the step (1) is 132-140 ℃;
preferably, the atmosphere in the urea melting in the step (1) is air.
3. The production method according to claim 1 or 2, wherein the catalyst of step (1) comprises a transition metal oxide;
preferably, the transition metal oxide comprises any one of copper oxide, iron oxide or manganese dioxide or a combination of at least two of the same;
preferably, the addition amount of the catalyst in the step (1) is independently 0-500 ppm.
4. The method according to any one of claims 1 to 3, wherein the step (1) of mixing is followed by stirring to homogeneity;
preferably, the granulation molding in the step (1) is carried out in a granulation device;
preferably, the temperature of the granulation molding in the step (1) is 95-115 ℃;
preferably, the particle size of the spherical particles in the step (1) is 2-5 mm.
5. The method according to any one of claims 1 to 4, wherein the coating apparatus of step (2) comprises a coating machine comprising a drum assembly;
preferably, the rotating speed of the rotating drum is 20-50 r/min;
preferably, the spherical particles follow the drum uniformly.
6. The method according to any one of claims 1 to 5, wherein the isocyanate in step (2) comprises any one of toluene diisocyanate, diphenylmethane diisocyanate or dicyclohexylmethane diisocyanate or a combination of at least two thereof;
preferably, the polyol of step (2) comprises a polyether polyol and/or a polyester polyol;
preferably, the isocyanate and the polyol are sprayed in the sequence of step (2): the isocyanate is sprayed first and then the polyol.
7. The method according to any one of claims 1 to 6, wherein the isocyanate and the polyol are added in the step (2) in a total amount of 0.3 to 5.0 wt% based on the spherical particles;
preferably, the mass ratio of the isocyanate to the polyol in the step (2) is 1: 0.9-1: 4.0, preferably 1: 1.0-1: 3.0.
8. The method according to any one of claims 1 to 7, wherein the temperature of the coating film in the step (2) is 60 to 100 ℃;
preferably, hot air is introduced to maintain the temperature of the coating during the coating in the step (2);
preferably, the coating time in the step (2) is 0.25-1 h;
preferably, unloading and air-drying are carried out after the coating is finished, so as to obtain the polymer denitration agent.
9. The method of any one of claims 1 to 8, comprising the steps of:
(1) mixing melted urea with a catalyst, wherein the temperature of urea melting is 132-140 ℃, the catalyst comprises transition metal oxide, the adding amount of the transition metal oxide is 0-500 ppm, uniformly stirring the mixture, putting the mixture into granulation equipment, and performing granulation molding, wherein the temperature of the granulation molding is 95-115 ℃ to obtain spherical particles, and the particle size of the spherical particles is 2-5 mm;
(2) putting the spherical particles obtained in the step (1) into a coating machine, wherein the rotating speed of a rotating cylinder in the coating machine is 20-50 r/min, uniformly rotating the spherical particles, and then sequentially spraying isocyanate and polyol for coating, wherein the isocyanate comprises any one or a combination of at least two of toluene diisocyanate, diphenylmethane diisocyanate or dicyclohexylmethane diisocyanate, the polyol comprises polyether polyol and/or polyester polyol, the total adding amount of the polyether polyol and the polyester polyol accounts for 0.3-5.0 wt% of the spherical particles, the mass ratio of the polyether polyol to the polyester polyol is 1: 1.0-1: 3.0, the coating temperature is 60-100 ℃, hot air is introduced during coating to maintain the coating temperature, the coating time is 0.25-1 h, and the organic coating denitration agent is obtained after coating.
10. An organic coated denitration agent obtained by the preparation method of any one of claims 1 to 9.
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