Oxidized pellet middle denitration process

Abstract

The invention relates to the technical field of oxidized pellet production, and discloses an oxidized pellet middle denitration process which comprises the following steps: S1, preparing oxidized pellets: uniformly mixing iron ore concentrate and bentonite to obtain a uniformly mixed material; s2, preparing oxidized pellets: adding calcium peroxide, water and composite fuel into the uniformly mixed material, and pelletizing in a pelletizer to obtain green pellets; s3, preparing a polymer denitration agent; s4, the green pellets are distributed to a belt type roasting machine and sequentially treated through a drying section, a preheating section, a roasting section, a soaking section and a cooling section, and then roasted pellets are obtained; s5, denitration treatment is conducted, specifically, the high-molecular denitration agent prepared in the S3 is conveyed to a spray gun through a conveying pump in the roasting section in the S4, and the high-molecular denitration agent is atomized through compressed air at an inlet of the spray gun and then sprayed into green pellets to be distributed to a belt type roasting machine for denitration; and S6, flue gas treatment. According to the invention, the high-molecular denitration agent is atomized and sprayed into the green pellet cloth through the spray gun for denitration treatment, so that the emission of nitrogen oxides is remarkably reduced.

Description

Technical Field

[0001] The invention relates to the technical field of oxidation pellet production, and in particular to a middle denitration process for oxidation pellets. Background Art

[0002] Oxidation pelletizing is one of the important methods for powder ore agglomeration. First, add appropriate amount of water and binder to powder ore to make green balls with uniform viscosity and sufficient strength. After drying and preheating, they are roasted in an oxidizing atmosphere to make the green balls agglomerate and make pellets. This method is particularly suitable for processing fine concentrate powder. Pellets have good cold strength, reducibility and particle size composition. In the steel industry, pellets and sintered ore are also important blast furnace charges. They can form a better charge structure together and are also used in non-ferrous metal smelting. The current denitrification technologies in the production of oxidation pellets are: 1. SNCR denitrification at the head of the chain grate smoke hood; 2. Denitrification at the tail of the flue gas produced by oxidation pellets; generally, desulfurization and denitrification are integrated. First, after the flue gas is desulfurized, the flue gas temperature is reduced to about 100°C, and then the flue gas is heated to a temperature that meets the requirements of the catalyst (about 300°C) for denitrification.

[0003] The SNCR denitrification at the head of the grate has a high temperature requirement, a large amount of ammonia leakage, and low denitrification efficiency. In the denitrification of the flue gas tail of the oxidation pellet production, the flue gas temperature is first reduced to about 100°C after desulfurization, and then the flue gas is heated to a temperature that meets the catalyst requirements (about 300°C) for denitrification. The invention of the denitrification process in the middle of the oxidation pellet is due to the concern for environmental pollution and the continuous exploration of denitrification technology. With the improvement of environmental awareness and the continuous improvement of relevant laws and regulations, the requirements for reducing pollutants such as nitrogen oxides emitted by industrial equipment such as coal-fired boilers are becoming increasingly stringent. Traditional denitrification methods have problems such as high cost and low efficiency. There is an urgent need for a more efficient and reliable denitrification technology to meet environmental protection needs.

[0004] To this end, we proposed a mid-stage denitrification process for oxidized pellets. Summary of the invention

[0005] The present invention mainly solves the technical problems existing in the above-mentioned prior art and provides a process for denitrification in the middle of oxidation pellets.

[0006] In order to achieve the above-mentioned purpose, the present invention adopts the following technical scheme, a process for denitrification in the middle of an oxidized pellet, comprising the following steps: S1, batching ingredients of an oxidized pellet: mixing iron ore concentrate and bentonite to obtain a mixed material; S2, making oxidized pellets: adding calcium peroxide, water and composite fuel to the mixed material, making pellets in a pelletizing machine, and obtaining raw pellets; S3, preparing a polymer denitrification agent; S4, spreading the raw pellets to a belt roasting machine, and obtaining roasted pellets after sequentially undergoing a drying section, a preheating section, a roasting section, a soaking section and a cooling section; S5 , denitrification treatment, the roasting section in S4 uses a delivery pump to deliver the polymer denitrification agent prepared in S3 to the spray gun, and then is atomized by compressed air at the inlet of the spray gun and sprayed into the raw pellet material to the belt roasting machine for denitrification; S6, flue gas treatment, in the cooling section treatment in S4, NH3 is sprayed into the circulating exhaust gas before it enters the cooling section material layer, and it is introduced into the medium and low temperature cooling section. The nitrogen oxides in the flue gas react with NH3 under the action of magnetite catalyst to undergo denitrification reaction. The exhaust gas after denitrification in the medium and low temperature cooling section is circulated to the blast drying section and discharged after dust removal and other treatments.

[0007] Preferably, the weights of iron ore concentrate and bentonite in S1 are 1000-5000 g and 200-1000 g, respectively.

[0008] Preferably, the grams of calcium oxide, water and composite fuel in S2 are 20-200 grams, 150-700 grams and 30-200 grams respectively.

[0009] Preferably, in S3, NH4HCO3, Na2CO3, NH4Cl, V2O5, CuSO4 and KMnO4 are pre-prepared as an amino complex in a molar ratio of 30:25:1:1:2:2.5; then the amino complex, ammonium persulfate, sodium carboxymethyl cellulose, hydrogenated castor oil and organic sulfoxide are prepared; pure water is added at room temperature, and the reaction is activated by stirring to obtain a polymer denitrification agent for use.

[0010] Preferably, the amino complex, ammonium persulfate, sodium carboxymethyl cellulose, hydrogenated castor oil and organic sulfoxide are 50-80 parts, 4.0-7.0 parts, 2.0-5.0 parts, 3.0-6.5 parts and 3.2-7.2 parts respectively, and stirred for 25 min-50 min.

[0011] Preferably, the temperature of the drying section is 150-350°C and the duration is 30-60 minutes; the temperature of the preheating section is 400-600°C and the duration is 60-100 minutes; the temperature of the roasting section is 1250-2000°C and the duration is about 90-140 minutes; the temperature of the soaking section is 1000-1400°C and the duration is about 60-100 minutes.

[0012] Preferably, the outlet pressure of the delivery pump is 0.4-0.8 MPa, the pump flow rate is 0.25-0.6 m / h, and the reaction temperature in the incinerator is 750-1100°C.

[0013] Preferably, the NH3 / NO molar ratio in S6 is controlled to be 0.2-0.6, and the nitrogen oxide removal rate reaches 15-35%.

[0014] Beneficial Effects

[0015] The present invention provides a process for denitrification in the middle of an oxidized pellet, which has the following beneficial effects:

[0016] This oxidation pellet middle denitrification process places the prepared polymer denitrification agent together with the raw pellet cloth on a belt roaster, and sprays the polymer denitrification agent into the raw pellet cloth through a spray gun for denitrification treatment, thereby significantly reducing nitrogen oxide emissions. At the same time, during the flue gas treatment process, nitrogen oxides in the exhaust gas are effectively removed by spraying NH3 in the cooling section and using a catalyst for catalytic reaction. This denitrification technology can not only improve denitrification efficiency and reduce operating costs, but also effectively reduce pollution to the environment, providing beneficial technical support for environmentally friendly production of enterprises. DETAILED DESCRIPTION

[0017] In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] Embodiment 1: A process for denitrification in the middle of an oxidized pellet, comprising the following steps:

[0019] S1. Ingredients for oxidation pellets: 1000 g of iron ore concentrate and 200 g of bentonite are mixed to obtain a mixed material;

[0020] S2, making oxidation pellets: adding 20 grams of calcium peroxide, 150 grams of water and 30 grams of composite fuel to the mixed material, making pellets in a pelletizing machine to obtain green pellets;

[0021] S3. Preparation of polymer denitrifier: pre-prepare NH4HCO3, Na2CO3, NH4Cl, V2O5, CuSO4 and KMnO4 in a molar ratio of 30:25:1:1:2:2.5 to form an amino complex; then prepare 50 parts of amino complex, 4.0 parts of ammonium persulfate, 2.0 parts of sodium carboxymethyl cellulose, 3.0 parts of hydrogenated castor oil and 3.2 parts of organic sulfoxide by weight; add purified water at room temperature, stir for 25 minutes to complete the reaction activation to obtain a polymer denitrifier for use;

[0022] S4, pellet roasting: the raw pellets are placed on a belt roasting machine, and sequentially processed through a drying section (temperature of about 150°C, duration of about 30 minutes), a preheating section (temperature of about 400°C, duration of about 60 minutes), a roasting section (temperature of about 1250°C, duration of about 90 minutes), a soaking section (temperature of about 1000°C, duration of about 60 minutes) and a cooling section to obtain roasted pellets;

[0023] S5, denitration treatment: In the roasting section in S4, the polymer denitration agent prepared in S3 is delivered to the spray gun by a delivery pump, atomized by compressed air at the inlet of the spray gun, and then sprayed into the raw pellets to the belt roasting machine for denitration; the outlet pressure of the delivery pump is 0.4MPa, the pump flow rate is 0.25m / h, and the reaction temperature in the incinerator is 750°C;

[0024] S6. Flue gas treatment: In the cooling section treatment in S4, NH3 is sprayed into the circulating exhaust gas before it enters the cooling section material layer, and the NH3 / NO molar ratio is controlled to be 0.2. Then it is introduced into the medium and low temperature cooling section, which is located in the area where the average temperature of the material layer is cooled to 200°C. Nitrogen oxides in the flue gas react with NH3 under the action of magnetite catalyst to undergo denitrification reaction, and the nitrogen oxide removal rate reaches 15%. The exhaust gas after denitrification in the medium and low temperature cooling section is circulated to the blast drying section and discharged after dust removal and other treatments.

[0025] Embodiment 2: A process for denitrification in the middle of an oxidized pellet, comprising the following steps:

[0026] S1. Ingredients for oxidation pellets: 2000 g of iron ore concentrate and 400 g of bentonite are mixed to obtain a mixed material;

[0027] S2, making oxidation pellets: adding 40 grams of calcium peroxide, 300 grams of water and 60 grams of composite fuel to the mixed material, making pellets in a pelletizing machine to obtain green pellets;

[0028] S3. Preparation of polymer denitrifier: pre-prepare NH4HCO3, Na2CO3, NH4Cl, V2O5, CuSO4 and KMnO4 in a molar ratio of 30:25:1:1:2:2.5 to form an amino complex; then prepare 55 parts of amino complex, 4.5 parts of ammonium persulfate, 2.5 parts of sodium carboxymethyl cellulose, 4.0 parts of hydrogenated castor oil and 4.2 parts of organic sulfoxide by weight; add purified water at room temperature, stir for 30 minutes to complete the reaction activation to obtain a polymer denitrifier for use;

[0029] S4, pellet roasting: the raw pellets are placed on a belt roasting machine, and sequentially processed through a drying section (temperature of about 200°C, duration of about 35 minutes), a preheating section (temperature of about 450°C, duration of about 70 minutes), a roasting section (temperature of about 1450°C, duration of about 100 minutes), a soaking section (temperature of about 1100°C, duration of about 70 minutes) and a cooling section to obtain roasted pellets;

[0030] S5, denitration treatment: In the roasting section in S4, the polymer denitration agent prepared in S3 is delivered to the spray gun by a delivery pump, and after being atomized by compressed air at the inlet of the spray gun, it is sprayed into the raw pellets and distributed on the belt roasting machine for denitration; the outlet pressure of the delivery pump is 0.5MPa, the pump flow rate is 0.3m / h, and the reaction temperature in the incinerator is 800℃;

[0031] S6. Flue gas treatment: In the cooling section treatment in S4, NH3 is sprayed into the circulating exhaust gas before it enters the cooling section material layer, and the NH3 / NO molar ratio is controlled to be 0.3. Then it is introduced into the medium and low temperature cooling section, which is located in the area where the average temperature of the material layer is cooled to 300°C. Nitrogen oxides in the flue gas react with NH3 under the action of magnetite catalyst to undergo denitrification reaction, and the nitrogen oxide removal rate reaches 20%. The exhaust gas after denitrification in the medium and low temperature cooling section is circulated to the blast drying section and discharged after dust removal and other treatments.

[0032] Embodiment 3: A process for denitrification in the middle of an oxidized pellet, comprising the following steps:

[0033] S1. Ingredients for oxidation pellets: 3000 g of iron ore concentrate and 600 g of bentonite are mixed to obtain a mixed material;

[0034] S2, making oxidation pellets: adding 80 grams of calcium peroxide, 500 grams of water and 80 grams of composite fuel to the mixed material, making pellets in a pelletizing machine to obtain green pellets;

[0035] S3. Preparation of polymer denitrifier: pre-prepare NH4HCO3, Na2CO3, NH4Cl, V2O5, CuSO4 and KMnO4 in a molar ratio of 30:25:1:1:2:2.5 to form an amino complex; then prepare 60 parts of amino complex, 5.0 parts of ammonium persulfate, 3.0 parts of sodium carboxymethyl cellulose, 5.0 parts of hydrogenated castor oil and 5.2 parts of organic sulfoxide by weight; add purified water at room temperature, stir for 35 minutes to complete the reaction activation to obtain a polymer denitrifier for use;

[0036] S4, pellet roasting: the raw pellets are placed on a belt roasting machine, and sequentially processed through a drying section (temperature of about 250°C, duration of about 40 minutes), a preheating section (temperature of about 500°C, duration of about 80 minutes), a roasting section (temperature of about 1650°C, duration of about 110 minutes), a soaking section (temperature of about 1200°C, duration of about 80 minutes) and a cooling section to obtain roasted pellets;

[0037] S5, denitration treatment: In the roasting section in S4, the polymer denitration agent prepared in S3 is delivered to the spray gun by a delivery pump, atomized by compressed air at the inlet of the spray gun, and then sprayed into the raw pellets to the belt roasting machine for denitration; the outlet pressure of the delivery pump is 0.6MPa, the pump flow rate is 0.4m / h, and the reaction temperature in the incinerator is 900°C;

[0038] S6. Flue gas treatment: In the cooling section treatment in S4, NH3 is sprayed into the circulating exhaust gas before it enters the cooling section material layer, and the NH3 / NO molar ratio is controlled to be 0.4. Then it is introduced into the medium and low temperature cooling section, which is located in the area where the average temperature of the material layer is cooled to 350°C. Nitrogen oxides in the flue gas react with NH3 under the action of magnetite catalyst to undergo denitrification reaction, and the nitrogen oxide removal rate reaches 25%. The exhaust gas after denitrification in the medium and low temperature cooling section is circulated to the blast drying section and discharged after dust removal and other treatments.

[0039] Embodiment 4: A process for denitrification in the middle of an oxidized pellet, comprising the following steps:

[0040] S1. Ingredients for oxidation pellets: 4000 g of iron ore concentrate and 800 g of bentonite are mixed to obtain a mixed material;

[0041] S2, making oxidation pellets: adding 100 g of calcium peroxide, 600 g of water and 100 g of composite fuel to the mixed material, making pellets in a pelletizing machine to obtain green pellets;

[0042] S3. Preparation of polymer denitrifier: pre-prepare NH4HCO3, Na2CO3, NH4Cl, V2O5, CuSO4 and KMnO4 in a molar ratio of 30:25:1:1:2:2.5 to form an amino complex; then prepare 70 parts of amino complex, 6.0 parts of ammonium persulfate, 4.0 parts of sodium carboxymethyl cellulose, 6.0 parts of hydrogenated castor oil and 6.2 parts of organic sulfoxide by weight; add purified water at room temperature, stir for 40 minutes to complete the reaction activation to obtain a polymer denitrifier for use;

[0043] S4, pellet roasting: the raw pellets are placed on a belt roasting machine, and are sequentially processed through a drying section (temperature of about 300°C, duration of about 50 minutes), a preheating section (temperature of about 550°C, duration of about 90 minutes), a roasting section (temperature of about 1850°C, duration of about 120 minutes), a soaking section (temperature of about 1300°C, duration of about 90 minutes) and a cooling section to obtain roasted pellets;

[0044] S5, denitration treatment: In the roasting section in S4, the polymer denitration agent prepared in S3 is delivered to the spray gun by a delivery pump, atomized by compressed air at the inlet of the spray gun, and then sprayed into the raw pellets to the belt roasting machine for denitration; the outlet pressure of the delivery pump is 0.7MPa, the pump flow rate is 0.5m / h, and the reaction temperature in the incinerator is 1000℃;

[0045] S6. Flue gas treatment: In the cooling section treatment in S4, NH3 is sprayed into the circulating exhaust gas before it enters the cooling section material layer, and the NH3 / NO molar ratio is controlled to be 0.5. Then it is introduced into the medium and low temperature cooling section, which is located in the area where the average temperature of the material layer is cooled to 350°C. Nitrogen oxides in the flue gas react with NH3 under the action of magnetite catalyst to undergo denitrification reaction, and the nitrogen oxide removal rate reaches 30%. The exhaust gas after denitrification in the medium and low temperature cooling section is circulated to the blast drying section and discharged after dust removal and other treatments.

[0046] Embodiment 5: A process for denitrification in the middle of an oxidized pellet, comprising the following steps:

[0047] S1. Ingredients for oxidation pellets: 5000 g of iron ore concentrate and 1000 g of bentonite are mixed to obtain a mixed material;

[0048] S2, making oxidation pellets: adding 200 grams of calcium peroxide, 700 grams of water and 200 grams of composite fuel to the mixed material, making pellets in a pelletizing machine to obtain green pellets;

[0049] S3. Preparation of polymer denitrifier: pre-prepare NH4HCO3, Na2CO3, NH4Cl, V2O5, CuSO4 and KMnO4 in a molar ratio of 30:25:1:1:2:2.5 to form an amino complex; then prepare 80 parts of amino complex, 7.0 parts of ammonium persulfate, 5.0 parts of sodium carboxymethyl cellulose, 6.5 parts of hydrogenated castor oil and 7.2 parts of organic sulfoxide by weight; add purified water at room temperature, stir for 50 minutes to complete the reaction activation to obtain a polymer denitrifier for use;

[0050] S4, pellet roasting: the raw pellets are placed on a belt roasting machine, and sequentially processed through a drying section (temperature of about 350°C, duration of about 60 minutes), a preheating section (temperature of about 600°C, duration of about 100 minutes), a roasting section (temperature of about 2000°C, duration of about 140 minutes), a soaking section (temperature of about 1400°C, duration of about 100 minutes) and a cooling section to obtain roasted pellets;

[0051] S5, denitration treatment: In the roasting section in S4, the polymer denitration agent prepared in S3 is delivered to the spray gun by a delivery pump, and after being atomized by compressed air at the inlet of the spray gun, it is sprayed into the raw pellets and distributed on the belt roasting machine for denitration; the outlet pressure of the delivery pump is 0.8MPa, the pump flow rate is 0.6m / h, and the reaction temperature in the incinerator is 1100°C;

[0052] S6. Flue gas treatment: In the cooling section treatment in S4, NH3 is sprayed into the circulating exhaust gas before it enters the cooling section material layer, and the NH3 / NO molar ratio is controlled to be 0.6. Then it is introduced into the medium and low temperature cooling section, which is located in the area where the average temperature of the material layer is cooled to 400°C. Nitrogen oxides in the flue gas react with NH3 under the action of magnetite catalyst to undergo denitrification reaction, and the nitrogen oxide removal rate reaches 35%. The exhaust gas after denitrification in the medium and low temperature cooling section is circulated to the blast drying section and discharged after dust removal and other treatments.

[0054] The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise specified, "plurality" means two or more.

[0055] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0056] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A process for denitrification in the middle of an oxidized pellet, characterized in that: The following steps are involved: S1. Ingredients for oxidation pellets: mixing iron ore concentrate and bentonite to obtain a mixed material; S2, making oxidized pellets: adding calcium peroxide, water and composite fuel to the mixed material, making pellets in a pelletizer to obtain green pellets; S3, preparing a polymer denitrifier; S4, spreading the green pellets to a belt roaster, and successively passing through a drying section, a preheating section, a roasting section, a soaking section and a cooling section to obtain roasted pellets; S5, denitrification treatment, in the roasting section of S4, the polymer denitrifier prepared in S3 is delivered to the spray gun by a delivery pump, and after being atomized by compressed air at the inlet of the spray gun, it is sprayed into the green pellets and spread on the belt roaster for denitrification; S6, flue gas treatment, in the cooling section treatment in S4, NH3 is sprayed before the circulating exhaust gas enters the cooling section material layer, and it is introduced into the medium and low temperature cooling section, and the nitrogen oxides in the flue gas react with NH3 under the action of a magnetite catalyst to undergo a denitrification reaction, and the exhaust gas after denitrification in the medium and low temperature cooling section is circulated to the blast drying section, and discharged after dust removal and other treatments.

2. The process for denitrification in the middle of oxidation pellets according to claim 1, characterized in that: In S1, the weights of iron ore concentrate and bentonite are 1000-5000 g and 200-1000 g, respectively.

3. The process for denitrification in the middle of oxidation pellets according to claim 1, characterized in that: In S2, the grams of calcium oxide, water and composite fuel are 20-200 grams, 150-700 grams and 30-200 grams respectively.

4. The process for denitrification in the middle of oxidation pellets according to claim 1, characterized in that: In S3, NH4HCO3, Na2CO3, NH4Cl, V2O5, CuSO4 and KMnO4 are pre-prepared into an amino complex in a molar ratio of 30﹕25﹕1﹕1﹕2﹕2.5; then the amino complex, ammonium persulfate, sodium carboxymethyl cellulose, hydrogenated castor oil and organic sulfoxide are prepared; pure water is added at room temperature, and the reaction activation is completed by stirring to obtain a polymer denitrification agent for use.

5. The process for denitrification in the middle of oxidation pellets according to claim 4, characterized in that: The amino complex, ammonium persulfate, sodium carboxymethyl cellulose, hydrogenated castor oil and organic sulfoxide are 50-80 parts, 4.0-7.0 parts, 2.0-5.0 parts, 3.0-6.5 parts and 3.2-7.2 parts respectively, and stirred for 25 minutes to 50 minutes.

6. The process for denitrification in the middle of oxidation pellets according to claim 1, characterized in that: In S4, the temperature of the drying section is 150-350°C and the duration is 30-60 minutes; the temperature of the preheating section is 400-600°C and the duration is 60-100 minutes; the temperature of the roasting section is 1250-2000°C and the duration is about 90-140 minutes; the temperature of the soaking section is 1000-1400°C and the duration is about 60-100 minutes.

7. The process for denitrification in the middle of oxidation pellets according to claim 1, characterized in that: The outlet pressure of the delivery pump is 0.4-0.8 MPa, the pump flow rate is 0.25-0.6 m / h, and the reaction temperature in the incinerator is 750-1100°C.

8. The process for denitrification in the middle of oxidation pellets according to claim 1, characterized in that: In the S6, the NH3 / NO molar ratio is controlled to be 0.2-0.6, and the nitrogen oxide removal rate reaches 15-35%.