Methods to reduce the agglomeration of alkaline pellets during roasting

Abstract

This invention discloses a production method for reducing the agglomeration of alkaline pellets during roasting. The method includes: mixing iron ore powder, limestone powder, and bentonite in a mixer; adding the mixture to a disc pelletizer and supplementing with water to produce pellets with an average particle size of 8-16 mm; feeding the pellets onto a chain grate-rotary kiln roasting equipment; preheating and roasting in the chain grate and high-temperature roasting in the rotary kiln; and cooling the pellets in an annular cooler to obtain the finished pellets. The method further includes: using bituminous coal for the second stage of preheating in the chain grate; and using two pulverized coal injection guns in the rotary kiln. The first pulverized coal injection gun is inserted into the center of the rotary kiln, injecting a mixture of 50% bituminous coal and 50% anthracite; and the second pulverized coal injection gun is inserted into the kiln head of the rotary kiln and supplements with an appropriate amount of 100% anthracite. This invention can effectively reduce the agglomeration of alkaline pellets during rotary kiln roasting, thereby reducing the manual cleaning burden of unclogging the strip screen and ensuring normal production.

Description

Technical Field

[0001] This invention belongs to the field of iron ore powder alkaline pellet production technology, and more specifically relates to a method for reducing the agglomeration of alkaline pellets during roasting. Background Technology

[0002] When producing alkaline iron ore pellets using a chain grate rotary kiln, the pellets exiting the kiln head tend to form large, agglomerated lumps of 30-60 mm or more. After cooling in the annular cooler, these lumps easily clog the bar screen, requiring constant manual cleaning and potentially leading to production accidents and disrupting normal operations. Therefore, it is necessary to develop a production method that reduces agglomeration during the roasting process of alkaline pellets, thereby improving the efficiency of the chain grate rotary kiln production line and reducing the incidence of production accidents. Summary of the Invention

[0003] To address the technical problems existing in the prior art, the present invention provides a method for reducing the agglomeration of alkaline pellets during roasting, comprising the following steps:

[0004] Step 1: Ingredient preparation and pelleting

[0005] Iron ore powder, limestone powder, and bentonite are mixed evenly in a mixer and then added to a disc pelletizer to produce pellets with added water, resulting in green pellets with an average particle size of 8-16 mm.

[0006] Step 2: Calcination and Cooling

[0007] The material is fed into a chain grate-rotary kiln roasting equipment, preheated and roasted in the chain grate and then roasted at high temperature in the rotary kiln. After cooling in an annular cooler, the finished pellets are obtained, wherein:

[0008] The coal powder used for the second stage of preheating and supplementary heating of the chain grate machine is bituminous coal. The bituminous coal contains 29-35% volatile matter, less than 10% ash, and more than 58% fixed carbon by weight percentage. The proportion of the bituminous coal with a fineness of less than 200 mesh is controlled to be more than 80%.

[0009] The rotary kiln is equipped with two pulverized coal injection lances. The first lance is inserted into the center of the rotary kiln, and the pulverized coal injected by the first lance is a mixture of 50% bituminous coal and 50% anthracite. The proportion of the mixed pulverized coal with a fineness of less than 200 mesh is controlled to be above 80%, and the volatile matter content of the mixed pulverized coal is 18-25% by weight, the ash content is less than 13%, and the fixed carbon content is greater than 67%. The second lance is inserted into the kiln head of the rotary kiln, and the pulverized coal injected by the second lance is 100% anthracite. The proportion of the anthracite with a fineness of less than 200 mesh is controlled to be above 80%, and the volatile matter content of the anthracite is 9-12% by weight, the ash content is less than 11%, and the fixed carbon content is greater than 75%.

[0010] Furthermore, in the above method for reducing the expansion rate of pellets, in the batching and pelletizing steps, the moisture content of the green pellets is controlled at 9.6% by weight, and the iron ore powder, limestone powder, and bentonite are weighed and batched according to the following weight proportions:

[0011] 37 parts limestone powder

[0012] 953 parts of iron ore powder

[0013] 10 parts bentonite

[0014] The iron ore powder has an iron grade of 65.8%, a SiO2 content of 4.4% and an FeO content of 17.5% by weight, and a particle size of less than 325 mesh of 98.8%; the limestone powder has a CaO content of 51.8% by weight, and a particle size of less than 325 mesh of 95.7%.

[0015] Furthermore, in the above-mentioned method for reducing the expansion rate of pellets, in the roasting and cooling steps, the coal injection rate of the second stage of preheating bituminous coal in the chain grate is controlled at 1.22 t / h, and the temperature of the second stage of preheating hood in the chain grate is controlled at 1150~1170℃.

[0016] Furthermore, in the above-mentioned method for reducing the expansion rate of pellets, during the roasting and cooling steps, the first pulverized coal injection gun inserted at the center of the rotary kiln is about 20 meters away from the kiln head, and the pulverized coal injection rate is controlled at 3.5 to 4.0 t / h; the second pulverized coal injection gun inserted at the kiln head is about 5 meters away from the kiln head, and the pulverized coal injection rate is controlled at 0.2 to 0.6 t / h; and the temperature at the kiln head of the rotary kiln is controlled at 1140 to 1160℃.

[0017] Furthermore, in the above-mentioned method for reducing the expansion rate of pellets, the coal injection rate of the second stage of preheating bituminous coal in the chain grate is 1.22 t / h; the first coal injection gun inserted at the center of the rotary kiln is about 20 meters away from the kiln head, with a coal injection rate of 3.92 t / h. The proportion of the fineness of the mixed coal powder injected by the first coal injection gun is less than 200 mesh, which accounts for 82.3%. The volatile matter, ash, and fixed carbon in the mixed coal powder are 21.93% by weight, 8.74% by weight, and 69.33% by weight. The second coal injection gun inserted at the kiln head of the rotary kiln is about 5 meters away from the kiln head, with a coal injection rate of 0.2 t / h.

[0018] Furthermore, in the above-mentioned method for reducing the expansion rate of pellets, the coal injection rate of the second stage of preheating bituminous coal in the chain grate is 1.22 t / h; the first coal injection lance inserted at the center of the rotary kiln is about 20 meters away from the kiln head, with a coal injection rate of 3.82 t / h. The proportion of the fineness of the mixed coal powder injected by the first coal injection lance is less than 200 mesh, which accounts for 82.3%. The mixed coal powder contains 21.93% volatile matter, 8.74% ash, and 69.33% fixed carbon by weight percentage; the second coal injection lance inserted at the kiln head of the rotary kiln is about 5 meters away from the kiln head, with a coal injection rate of 0.3 t / h.

[0019] Furthermore, in the above-mentioned method for reducing the expansion rate of pellets, the coal injection rate of the second stage of preheating bituminous coal in the chain grate machine is 1.22 t / h; the first coal injection gun inserted at the center of the rotary kiln is about 20 meters away from the kiln head, with a coal injection rate of 3.72 t / h. The proportion of fine coal powder with a fineness of less than 200 mesh in the mixed coal powder injected by the first coal injection gun is 82.3%, and the volatile matter, ash content, and fixed carbon content in the mixed coal powder are 21.93%, 8.74%, and 69.33% by weight percentage; the second coal injection gun inserted at the kiln head of the rotary kiln is about 5 meters away from the kiln head, with a coal injection rate of 0.4 t / h.

[0020] Furthermore, in the above-mentioned method for reducing the expansion rate of pellets, the coal injection rate of the second stage of preheating bituminous coal in the chain grate is 1.22 t / h; the first coal injection gun inserted at the center of the rotary kiln is about 20 meters away from the kiln head, with a coal injection rate of 3.62 t / h. The proportion of the fineness of the mixed coal powder injected by the first coal injection gun is less than 200 mesh, and the volatile matter, ash content, and fixed carbon content in the mixed coal powder are 21.93%, 8.74%, and 69.33% by weight percentage; the second coal injection gun inserted at the kiln head of the rotary kiln is about 5 meters away from the kiln head, with a coal injection rate of 0.5 t / h.

[0021] Furthermore, in the above-mentioned method for reducing the expansion rate of pellets, the coal injection rate of the second stage of preheating bituminous coal in the chain grate machine is 1.22 t / h; the first coal injection gun inserted at the center of the rotary kiln is about 20 meters away from the kiln head, with a coal injection rate of 3.52 t / h. The proportion of the fineness of the mixed coal powder injected by the first coal injection gun is less than 200 mesh, which accounts for 82.3%. The volatile matter, ash, and fixed carbon in the mixed coal powder are 21.93% by weight, 8.74% by weight, and 69.33% by weight. The second coal injection gun inserted at the kiln head of the rotary kiln is about 5 meters away from the kiln head, with a coal injection rate of 0.6 t / h.

[0022] Furthermore, in the above-mentioned method for reducing the expansion rate of coal pellets, the bituminous coal contains 32.39% volatile matter, 7.08% ash, and 60.53% fixed carbon by weight, while the anthracite contains 82.8% of its components with a fineness of less than 200 mesh; the anthracite contains 82.1% of its components with a fineness of less than 200 mesh, and the anthracite contains 11.48% volatile matter, 10.39% ash, and 78.13% fixed carbon by weight; in the mixed coal powder injected by the first pulverized coal injection gun, the Al2O3 content in the anthracite is controlled at 5.75% by weight, and the Al2O3 content in the bituminous coal is controlled at 6.68% by weight.

[0023] The production method of the present invention for reducing the agglomeration of alkaline pellets during roasting has the following advantages and beneficial effects: the pulverized coal used for the second stage of preheating of the chain grate is changed from anthracite to bituminous coal, and the pulverized coal injection guns of the rotary kiln are changed from one to two. One pulverized coal injection gun is located in the center of the rotary kiln, and the other pulverized coal injection gun is located at the kiln head of the rotary kiln and supplements the injection with an appropriate amount of anthracite. This can effectively reduce the agglomeration of alkaline pellets during the roasting process in the rotary kiln, thereby reducing the manual cleaning burden of unblocking the bar screen and ensuring the normal operation of production. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0025] To reduce the agglomeration of alkaline pellets during rotary kiln roasting, thereby alleviating the manual cleaning burden of unclogging the bar screen and ensuring normal production, this invention provides a production method for reducing agglomeration during alkaline pellet roasting. The main technical measures are: replacing the anthracite used for preheating the chain grate machine with bituminous coal; and changing the number of pulverized coal injection guns in the rotary kiln from one to two, with one gun positioned at the center of the kiln and the other at the kiln head, supplemented with an appropriate amount of anthracite. Specifically, the production method for reducing agglomeration of alkaline pellets during roasting provided by this invention includes the following steps:

[0026] Step 1: Ingredient preparation and pelleting

[0027] Iron ore powder, limestone powder, and bentonite are mixed evenly in a mixer and then added to a disc pelletizer to produce pellets with added water, resulting in green pellets with an average particle size of 8-16 mm.

[0028] Step 2: Calcination and Cooling

[0029] The material is fed into a chain grate-rotary kiln roasting equipment, preheated and roasted in the chain grate and then roasted at high temperature in the rotary kiln. After cooling in an annular cooler, the finished pellets are obtained, wherein:

[0030] The coal powder used for the second stage of preheating and supplementary heating of the chain grate machine is bituminous coal. The bituminous coal contains 29-35% volatile matter, less than 10% ash, and more than 58% fixed carbon by weight percentage. The proportion of the bituminous coal with a fineness of less than 200 mesh (0.074mm) is controlled to be more than 80%.

[0031] The rotary kiln is equipped with two pulverized coal injection lances. The first lance is inserted into the center of the rotary kiln, and the pulverized coal injected by the first lance is a mixture of 50% bituminous coal and 50% anthracite. The proportion of the fineness of the mixed pulverized coal with a particle size of less than 200 mesh (0.074 mm) is controlled to be above 80%. The volatile matter content of the mixed pulverized coal is 18-25% by weight, the ash content is less than 13%, and the fixed carbon content is greater than 67%. The second lance is inserted into the kiln head of the rotary kiln, and the pulverized coal injected by the second lance is 100% anthracite. The proportion of the fineness of the anthracite with a particle size of less than 200 mesh (0.074 mm) is controlled to be above 80%. The volatile matter content of the anthracite is 9-12% by weight, the ash content is less than 11%, and the fixed carbon content is greater than 75%.

[0032] Preferably, in the ingredient preparation and pelletizing steps, the moisture content of the raw pellets is controlled at 9.6% by weight.

[0033] Preferably, in the batching and pelletizing steps, iron ore powder, limestone powder, and bentonite are weighed and batched according to the following weight proportions:

[0034] 37 parts limestone powder

[0035] 953 parts of iron ore powder

[0036] 10 parts bentonite

[0037] The iron ore powder is a mixed iron ore powder mainly composed of magnetic ore powder, with an iron grade of 65.8%. The iron ore powder contains 4.4% SiO2 and 17.5% FeO by weight percentage, and 98.8% of the iron ore powder has a particle size smaller than 325 mesh (0.044 mm). The limestone powder contains 51.8% CaO by weight percentage, and 95.7% of the limestone powder has a particle size smaller than 325 mesh (0.044 mm). The bentonite is conventional bentonite that is available on the market.

[0038] Preferably, in the roasting and cooling steps, the amount of pulverized coal injected into the second stage of the chain grate preheating is controlled at 1.22 t / h, and the temperature of the smoke hood in the second stage of the chain grate preheating is controlled at 1150~1170℃.

[0039] Preferably, in the roasting and cooling steps, the first pulverized coal injection gun inserted into the center of the rotary kiln is about 20 meters away from the kiln head, and the pulverized coal injection rate is controlled at 3.5 to 4.0 t / h. The second pulverized coal injection gun inserted into the kiln head is about 5 meters away from the kiln head, and the pulverized coal injection rate is controlled at 0.2 to 0.6 t / h.

[0040] Preferably, during the roasting and cooling steps, the temperature at the kiln head of the rotary kiln is controlled at 1140–1160°C.

[0041] Preferably, in the roasting and cooling steps, the content of Al2O3 in the mixed coal powder injected by the first pulverized coal injection gun is controlled at 5.75% by weight for anthracite and 6.68% by weight for bituminous coal.

[0042] Preferably, the binary basicity (CaO / SiO2) of the finished pellet is 0.5.

[0043] After screening the pellets obtained as described above, the proportion of large lumps of 30-60mm in the pellets is less than 10%. It can be seen that the production method of the present invention for reducing the agglomeration of alkaline pellets during the roasting process can effectively reduce the agglomeration of alkaline pellets during the rotary kiln roasting process, thereby reducing the manual cleaning burden of unblocking the bar screen and ensuring the normal operation of production.

[0044] The following comparative examples and embodiments further illustrate the production method of the present invention for reducing the agglomeration of alkaline pellets during roasting.

[0045] Comparison Example

[0046] As a comparative example, the conventional method for producing alkaline pellets using a chain grate-rotary kiln includes the following steps:

[0047] (1) Ingredients

[0048] Iron ore powder, limestone powder, and bentonite are weighed and mixed according to the following weight proportions, with the specific ratio as follows:

[0049] 37 parts limestone powder

[0050] 953 parts of iron ore powder

[0051] 10 parts bentonite

[0052] The iron ore powder is a mixed iron ore powder mainly composed of magnetic ore powder from Lanxian County, Shanxi Province, with an iron grade of 65.8%. The iron ore powder contains 4.4% SiO2 and 17.5% FeO by weight percentage, and 98.8% of the iron ore powder has particles smaller than 325 mesh (0.044 mm). The limestone powder contains 51.8% CaO by weight percentage, and 95.7% of the limestone powder has particles smaller than 325 mesh (0.044 mm). The bentonite is conventional bentonite that is available on the market.

[0053] (2) Mixing and pelletizing

[0054] The limestone powder, iron ore powder and bentonite are mixed evenly by a mixer, and then added to a disc pelletizer to supplement water to produce pellets. The resulting pellets have a moisture content of 9.6% by weight and an average particle size of 8mm to 16mm.

[0055] (3) Calcination and cooling

[0056] The pellets are fed and fired on a chain grate-rotary kiln firing equipment to obtain finished pellets, wherein:

[0057] The pulverized coal used for the second stage of preheating of the chain grate machine is anthracite, with a pulverized coal injection rate of 1.2 t / h. The temperature of the second stage preheating hood is 1150-1170℃. The anthracite is Lu'an coal from Shanxi Province. The proportion of fineness components less than 200 mesh (0.074 mm) in the anthracite is 82.1%. The volatile matter content is 11.48%, the ash content is 10.39%, and the fixed carbon content is 78.13% by weight.

[0058] There is only one pulverized coal injection lance in the rotary kiln, inserted into the center of the kiln, about 20 meters from the kiln head. The temperature at the kiln head is 1140–1160℃. The pulverized coal injected by the lance is a mixture of 50% bituminous coal and 50% anthracite, with an injection rate of 4.0 t / h. The anthracite is still the aforementioned Lu'an coal from Shanxi, and the bituminous coal is Fugu coal from Shaanxi. The bituminous coal has a volatile matter content of 32.39% and an ash content of 7.08% by weight. The fixed carbon content is 60.53%; the proportion of components with a fineness of less than 200 mesh (0.074 mm) in the mixed coal powder is 82.3%; the volatile matter content, ash content, and fixed carbon content in the mixed coal powder are 21.93% by weight, 8.74% by weight, and 69.33% by weight; and in the mixed coal powder, the Al2O3 content in anthracite is 5.75% by weight, and the Al2O3 content in bituminous coal is 6.68% by weight.

[0059] The binary basicity (CaO / SiO2) of the finished pellet is 0.5.

[0060] After screening the pellets prepared using the control example, the proportion of large lumps (30-60 mm) in the pellets was 10.3%. The control example indicates that when roasting alkaline pellets, a high proportion of large lumps (30-60 mm) easily clogs the bar screen, requiring frequent manual cleaning and potentially leading to production accidents and disrupting normal production.

[0061] Example 1

[0062] In the production method for reducing agglomeration during the roasting of alkaline pellets in Example 1, the pulverized coal used for the second stage of preheating and supplementary heating of the chain grate machine is changed from anthracite to bituminous coal. Two pulverized coal injection guns are inserted into the rotary kiln, with the second gun supplementing the injection of an appropriate amount of anthracite. The specific steps of Example 1 are as follows:

[0063] Step 1: Ingredient preparation and pelleting

[0064] Iron ore powder, limestone powder, and bentonite are mixed evenly in a mixer, then added to a disc pelletizer with added water to produce green pellets with a moisture content of 9.6% by weight and an average particle size of 8–16 mm.

[0065] Iron ore powder, limestone powder, and bentonite shall be weighed and mixed according to the following weight proportions:

[0066] 37 parts limestone powder

[0067] 953 parts of iron ore powder

[0068] 10 parts bentonite

[0069] The iron ore powder is from Lanxian County, Shanxi Province. It is a mixed iron ore powder mainly composed of magnetic ore powder, with an iron grade of 65.8%. The iron ore powder contains 4.4% SiO2 and 17.5% FeO by weight percentage, and 98.8% of the particles are smaller than 325 mesh (0.044 mm). The limestone powder contains 51.8% CaO by weight percentage, and 95.7% of the particles are smaller than 325 mesh (0.044 mm). The bentonite is commercially available conventional bentonite.

[0070] Step 2: Calcination and Cooling

[0071] The material is fed into a chain grate-rotary kiln roasting equipment, preheated and roasted in the chain grate and then roasted at high temperature in the rotary kiln. After cooling in an annular cooler, the finished pellets are obtained, wherein:

[0072] The pulverized coal used for the second stage of preheating of the chain grate machine is bituminous coal, with a pulverized coal injection rate of 1.22 t / h. The temperature of the second stage preheating hood is 1150-1170℃. The bituminous coal is Shaanxi Fugu coal. The bituminous coal contains 32.39% volatile matter, 7.08% ash, and 60.53% fixed carbon by weight percentage. The proportion of components with a fineness of less than 200 mesh (0.074 mm) in the bituminous coal is controlled at 82.8%.

[0073] Two pulverized coal injection lances are installed in the rotary kiln. The first lance is inserted into the center of the kiln, approximately 20 meters from the kiln head, with a pulverized coal injection rate of 3.92 t / h. The pulverized coal injected by the first lance is a mixture of 50% bituminous coal and 50% anthracite. 82.3% of the mixed pulverized coal has a fineness of less than 200 mesh (0.074 mm). The mixed pulverized coal contains 21.93% volatile matter, 8.74% ash, and 69.33% fixed carbon by weight. The bituminous coal is as described above. The Shaanxi Fugu coal has a fineness of less than 200 mesh (0.074 mm) of 82.8% and a volatile matter content of 32.39%, an ash content of 7.08%, and a fixed carbon content of 60.53% by weight. The Shanxi Lu'an coal has a fineness of less than 200 mesh (0.074 mm) of 82.1% and a volatile matter content of 11.48%, an ash content of 10.39%, and a fixed carbon content of 78.13% by weight.

[0074] The second pulverized coal injection gun is inserted into the kiln head of the rotary kiln, about 5 meters away, with a pulverized coal injection rate of 0.2 t / h. The kiln head temperature is 1140-1160℃. The pulverized coal injected by the second pulverized coal injection gun is 100% anthracite, which is the aforementioned Shanxi Lu'an coal. The anthracite has a fineness of less than 200 mesh (0.074 mm) of 82.1% and, by weight percentage, volatile matter of 11.48%, ash of 10.39%, and fixed carbon of 78.13%.

[0075] The binary basicity (CaO / SiO2) of the finished pellet is 0.5.

[0076] The pellets produced using the production method described in Example 1 for reducing lumps formed during the roasting of alkaline pellets, after testing, showed that the proportion of large lumps with a particle size of 30-60 mm in the pellets after screening was 9.6%. Example 1 demonstrates that by changing the pulverized coal used for the second stage of preheating in the chain grate machine from anthracite to bituminous coal, and by inserting two pulverized coal injection guns into the rotary kiln, with the second gun supplementing with a small amount of anthracite, the proportion of large lumps with a particle size of 30-60 mm in the pellets can be reduced by 0.7 percentage points compared to the control example. This effectively reduces the lumps formed during the roasting of alkaline pellets in the rotary kiln, thereby reducing the manual cleaning burden of unclogging the strip screen and ensuring normal production.

[0077] Example 2

[0078] In the production method for reducing agglomeration during the roasting of alkaline pellets in Example 2, the pulverized coal used for the second stage of preheating in the chain grate machine is changed from anthracite to bituminous coal. Two pulverized coal injection guns are inserted into the rotary kiln, and the amount of anthracite injected by the second pulverized coal gun is appropriately increased to 0.3 t / h. The specific steps of Example 2 are as follows:

[0079] Step 1: Ingredient preparation and pelleting

[0080] Iron ore powder, limestone powder, and bentonite are mixed evenly in a mixer, then added to a disc pelletizer with added water to produce green pellets with a moisture content of 9.6% by weight and an average particle size of 8–16 mm.

[0081] Iron ore powder, limestone powder, and bentonite shall be weighed and mixed according to the following weight proportions:

[0082] 37 parts limestone powder

[0083] 953 parts of iron ore powder

[0084] 10 parts bentonite

[0085] The iron ore powder is from Lanxian County, Shanxi Province. It is a mixed iron ore powder mainly composed of magnetic ore powder, with an iron grade of 65.8%. The iron ore powder contains 4.4% SiO2 and 17.5% FeO by weight percentage, and 98.8% of the particles are smaller than 325 mesh (0.044 mm). The limestone powder contains 51.8% CaO by weight percentage, and 95.7% of the particles are smaller than 325 mesh (0.044 mm). The bentonite is commercially available conventional bentonite.

[0086] Step 2: Calcination and Cooling

[0087] The material is fed into a chain grate-rotary kiln roasting equipment, preheated and roasted in the chain grate and then roasted at high temperature in the rotary kiln. After cooling in an annular cooler, the finished pellets are obtained, wherein:

[0088] The pulverized coal used for the second stage of preheating of the chain grate machine is bituminous coal, with a pulverized coal injection rate of 1.22 t / h. The temperature of the second stage preheating hood is 1150-1170℃. The bituminous coal is Shaanxi Fugu coal. The bituminous coal contains 32.39% volatile matter, 7.08% ash, and 60.53% fixed carbon by weight percentage. The proportion of components with a fineness of less than 200 mesh (0.074 mm) in the bituminous coal is controlled at 82.8%.

[0089] Two pulverized coal injection lances are installed in the rotary kiln. The first lance is inserted into the center of the kiln, approximately 20 meters from the kiln head, with a pulverized coal injection rate of 3.82 t / h. The pulverized coal injected by the first lance is a mixture of 50% bituminous coal and 50% anthracite. 82.3% of the mixed pulverized coal has a fineness of less than 200 mesh (0.074 mm). The mixed pulverized coal contains 21.93% volatile matter, 8.74% ash, and 69.33% fixed carbon by weight. The bituminous coal is as described above. The Shaanxi Fugu coal has a fineness of less than 200 mesh (0.074 mm) of 82.8% and a volatile matter content of 32.39%, an ash content of 7.08%, and a fixed carbon content of 60.53% by weight. The Shanxi Lu'an coal has a fineness of less than 200 mesh (0.074 mm) of 82.1% and a volatile matter content of 11.48%, an ash content of 10.39%, and a fixed carbon content of 78.13% by weight.

[0090] The second pulverized coal injection gun is inserted into the kiln head of the rotary kiln, about 5 meters away, with a pulverized coal injection rate of 0.3 t / h. The kiln head temperature of the rotary kiln is 1140-1160℃. The pulverized coal injected by the second pulverized coal injection gun is 100% anthracite, which is the aforementioned Shanxi Lu'an coal. The proportion of the fineness of the anthracite is less than 200 mesh (0.074 mm), which is 82.1%. The anthracite contains 11.48% volatile matter, 10.39% ash, and 78.13% fixed carbon by weight.

[0091] The binary basicity (CaO / SiO2) of the finished pellet is 0.5.

[0092] The pellets produced using the production method described in Example 2 for reducing lumps formed during the roasting of alkaline pellets, after testing, showed that the proportion of large lumps with a particle size of 30-60 mm in the pellets was 9.1%. Example 2 demonstrates that by changing the pulverized coal used for the second stage of preheating in the chain grate machine from anthracite to bituminous coal, and inserting two pulverized coal injection guns into the rotary kiln, with the second gun injecting 0.1 t / h more anthracite than in Example 1, the proportion of large lumps with a particle size of 30-60 mm in the pellets can be reduced by 1.2 percentage points compared to the control example. This effectively reduces the lumps formed during the roasting of alkaline pellets in the rotary kiln, thereby reducing the manual cleaning burden of unclogging the strip screen and ensuring normal production.

[0093] Example 3

[0094] In the production method for reducing agglomeration during the roasting of alkaline pellets in Example 3, the pulverized coal used for the second stage of preheating in the chain grate machine is changed from anthracite to bituminous coal. Two pulverized coal injection guns are inserted into the rotary kiln, and the amount of anthracite injected by the second pulverized coal gun is appropriately increased to 0.4 t / h. The specific steps of Example 3 are as follows:

[0095] Step 1: Ingredient preparation and pelleting

[0096] Iron ore powder, limestone powder, and bentonite are mixed evenly in a mixer, then added to a disc pelletizer with added water to produce green pellets with a moisture content of 9.6% by weight and an average particle size of 8–16 mm.

[0097] Iron ore powder, limestone powder, and bentonite shall be weighed and mixed according to the following weight proportions:

[0098] 37 parts limestone powder

[0099] 953 parts of iron ore powder

[0100] 10 parts bentonite

[0101] The iron ore powder is from Lanxian County, Shanxi Province. It is a mixed iron ore powder mainly composed of magnetic ore powder, with an iron grade of 65.8%. The iron ore powder contains 4.4% SiO2 and 17.5% FeO by weight percentage, and 98.8% of the particles are smaller than 325 mesh (0.044 mm). The limestone powder contains 51.8% CaO by weight percentage, and 95.7% of the particles are smaller than 325 mesh (0.044 mm). The bentonite is commercially available conventional bentonite.

[0102] Step 2: Calcination and Cooling

[0103] The material is fed into a chain grate-rotary kiln roasting equipment, preheated and roasted in the chain grate and then roasted at high temperature in the rotary kiln. After cooling in an annular cooler, the finished pellets are obtained, wherein:

[0104] The pulverized coal used for the second stage of preheating of the chain grate machine is bituminous coal, with a pulverized coal injection rate of 1.22 t / h. The temperature of the second stage preheating hood is 1150-1170℃. The bituminous coal is Shaanxi Fugu coal. The bituminous coal contains 32.39% volatile matter, 7.08% ash, and 60.53% fixed carbon by weight percentage. The proportion of components with a fineness of less than 200 mesh (0.074 mm) in the bituminous coal is controlled at 82.8%.

[0105] Two pulverized coal injection lances are installed in the rotary kiln. The first lance is inserted into the center of the kiln, approximately 20 meters from the kiln head, with a pulverized coal injection rate of 3.72 t / h. The pulverized coal injected by the first lance is a mixture of 50% bituminous coal and 50% anthracite. 82.3% of the mixed pulverized coal has a fineness of less than 200 mesh (0.074 mm). The mixed pulverized coal contains 21.93% volatile matter, 8.74% ash, and 69.33% fixed carbon by weight. The bituminous coal is as described above. The Shaanxi Fugu coal has a fineness of less than 200 mesh (0.074 mm) of 82.8% and a volatile matter content of 32.39%, an ash content of 7.08%, and a fixed carbon content of 60.53% by weight. The Shanxi Lu'an coal has a fineness of less than 200 mesh (0.074 mm) of 82.1% and a volatile matter content of 11.48%, an ash content of 10.39%, and a fixed carbon content of 78.13% by weight.

[0106] The second pulverized coal injection gun is inserted into the kiln head of the rotary kiln, about 5 meters away from the kiln head. The pulverized coal injection rate is 0.4 t / h, and the kiln head temperature is 1140-1160℃. The pulverized coal injected by the second pulverized coal injection gun is 100% anthracite. The anthracite is the aforementioned Lu'an coal from Shanxi. The proportion of the fineness of the anthracite is less than 200 mesh (0.074 mm), which is 82.1%. The anthracite contains 11.48% volatile matter, 10.39% ash, and 78.13% fixed carbon by weight.

[0107] The binary basicity (CaO / SiO2) of the finished pellet is 0.5.

[0108] The pellets produced using the production method described in Example 3 for reducing lumps formed during the roasting of alkaline pellets, after screening, showed that the proportion of large lumps with a particle size of 30-60 mm was 8.6%. Example 3 demonstrates that by changing the pulverized coal used for the second stage of preheating in the chain grate machine from anthracite to bituminous coal, and inserting two pulverized coal injection guns into the rotary kiln, with the second gun injecting 0.2 t / h more anthracite than in Example 1, the proportion of large lumps with a particle size of 30-60 mm in the pellets can be reduced by 1.7 percentage points compared to the control example. This effectively reduces the lumps formed during the roasting of alkaline pellets in the rotary kiln, thereby reducing the manual cleaning burden of unclogging the strip screen and ensuring normal production.

[0109] Example 4

[0110] In the production method for reducing agglomeration during the roasting of alkaline pellets in Example 4, the pulverized coal used for the second stage of preheating in the chain grate machine is changed from anthracite to bituminous coal. Two pulverized coal injection guns are inserted into the rotary kiln, and the amount of anthracite injected by the second pulverized coal gun is appropriately increased to 0.5 t / h. The specific steps of Example 4 are as follows:

[0111] Step 1: Ingredient preparation and pelleting

[0112] Iron ore powder, limestone powder, and bentonite are mixed evenly in a mixer, then added to a disc pelletizer with added water to produce green pellets with a moisture content of 9.6% by weight and an average particle size of 8–16 mm.

[0113] Iron ore powder, limestone powder, and bentonite shall be weighed and mixed according to the following weight proportions:

[0114] 37 parts limestone powder

[0115] 953 parts of iron ore powder

[0116] 10 parts bentonite

[0117] The iron ore powder is from Lanxian County, Shanxi Province. It is a mixed iron ore powder mainly composed of magnetic ore powder, with an iron grade of 65.8%. The iron ore powder contains 4.4% SiO2 and 17.5% FeO by weight percentage, and 98.8% of the particles are smaller than 325 mesh (0.044 mm). The limestone powder contains 51.8% CaO by weight percentage, and 95.7% of the particles are smaller than 325 mesh (0.044 mm). The bentonite is commercially available conventional bentonite.

[0118] Step 2: Calcination and Cooling

[0119] The material is fed into a chain grate-rotary kiln roasting equipment, preheated and roasted in the chain grate and then roasted at high temperature in the rotary kiln. After cooling in an annular cooler, the finished pellets are obtained, wherein:

[0120] The pulverized coal used for the second stage of preheating of the chain grate machine is bituminous coal, with a pulverized coal injection rate of 1.22 t / h. The temperature of the second stage preheating hood is 1150-1170℃. The bituminous coal is Shaanxi Fugu coal. The bituminous coal contains 32.39% volatile matter, 7.08% ash, and 60.53% fixed carbon by weight percentage. The proportion of components with a fineness of less than 200 mesh (0.074 mm) in the bituminous coal is controlled at 82.8%.

[0121] Two pulverized coal injection lances are installed in the rotary kiln. The first lance is inserted into the center of the kiln, approximately 20 meters from the kiln head, with a pulverized coal injection rate of 3.62 t / h. The pulverized coal injected by the first lance is a mixture of 50% bituminous coal and 50% anthracite. 82.3% of the mixed pulverized coal has a fineness of less than 200 mesh (0.074 mm). The mixed pulverized coal contains 21.93% volatile matter, 8.74% ash, and 69.33% fixed carbon by weight. The bituminous coal is as described above. The Shaanxi Fugu coal has a fineness of less than 200 mesh (0.074 mm) of 82.8% in its anthracite composition. By weight percentage, it contains 32.39% volatile matter, 7.08% ash, and 60.53% fixed carbon. The Shanxi Lu'an coal has a fineness of less than 200 mesh (0.074 mm) of 82.1% in its anthracite composition. By weight percentage, it contains 11.48% volatile matter, 10.39% ash, and 78.13% fixed carbon.

[0122] The second pulverized coal injection gun is inserted into the kiln head of the rotary kiln, about 5 meters away, with a pulverized coal injection rate of 0.5 t / h. The kiln head temperature of the rotary kiln is 1140-1160℃. The pulverized coal injected by the second pulverized coal injection gun is 100% anthracite, which is the aforementioned Shanxi Lu'an coal. The proportion of the fineness of the anthracite is less than 200 mesh (0.074 mm) of 82.1%. The volatile matter, ash, and fixed carbon in the anthracite are 11.48%, 10.39%, and 78.13% by weight.

[0123] The binary basicity (CaO / SiO2) of the finished pellet is 0.5.

[0124] The pellets produced using the production method described in Example 4 for reducing agglomeration during the roasting of alkaline pellets, after testing, showed that the proportion of large lumps with a particle size of 30-60 mm in the pellets was 8.3%. Example 4 demonstrates that by changing the pulverized coal used for the second stage of preheating in the chain grate machine from anthracite to bituminous coal, and inserting two pulverized coal injection guns into the rotary kiln, with the second gun injecting 0.3 t / h more anthracite than in Example 1, the proportion of large lumps with a particle size of 30-60 mm in the pellets can be reduced by 2.0 percentage points compared to the control example. This effectively reduces the agglomeration of alkaline pellets during the rotary kiln roasting process, thereby reducing the manual cleaning burden of unclogging the strip screen and ensuring normal production.

[0125] Example 5

[0126] In the production method for reducing agglomeration during the roasting of alkaline pellets in Example 5, the pulverized coal used for the second stage of preheating in the chain grate machine is changed from anthracite to bituminous coal. Two pulverized coal injection guns are inserted into the rotary kiln, and the amount of anthracite injected by the second pulverized coal gun is appropriately increased to 0.6 t / h. The specific steps of Example 5 are as follows:

[0127] Step 1: Ingredient preparation and pelleting

[0128] Iron ore powder, limestone powder, and bentonite are mixed evenly in a mixer, then added to a disc pelletizer with added water to produce green pellets with a moisture content of 9.6% by weight and an average particle size of 8–16 mm.

[0129] Iron ore powder, limestone powder, and bentonite shall be weighed and mixed according to the following weight proportions:

[0130] 37 parts limestone powder

[0131] 953 parts of iron ore powder

[0132] 10 parts bentonite

[0133] The iron ore powder is from Lanxian County, Shanxi Province. It is a mixed iron ore powder mainly composed of magnetic ore powder, with an iron grade of 65.8%. The iron ore powder contains 4.4% SiO2 and 17.5% FeO by weight percentage, and 98.8% of the particles are smaller than 325 mesh (0.044 mm). The limestone powder contains 51.8% CaO by weight percentage, and 95.7% of the particles are smaller than 325 mesh (0.044 mm). The bentonite is commercially available conventional bentonite.

[0134] Step 2: Calcination and Cooling

[0135] The material is fed into a chain grate-rotary kiln roasting equipment, preheated and roasted in the chain grate and then roasted at high temperature in the rotary kiln. After cooling in an annular cooler, the finished pellets are obtained, wherein:

[0136] The pulverized coal used for the second stage of preheating of the chain grate machine is bituminous coal, with a pulverized coal injection rate of 1.22 t / h. The temperature of the second stage preheating hood is 1150-1170℃. The bituminous coal is Shaanxi Fugu coal. The bituminous coal contains 32.39% volatile matter, 7.08% ash, and 60.53% fixed carbon by weight percentage. The proportion of components with a fineness of less than 200 mesh (0.074 mm) in the bituminous coal is controlled at 82.8%.

[0137] Two pulverized coal injection lances are installed in the rotary kiln. The first lance is inserted into the center of the kiln, approximately 20 meters from the kiln head, with a pulverized coal injection rate of 3.52 t / h. The pulverized coal injected by the first lance is a mixture of 50% bituminous coal and 50% anthracite. 82.3% of the mixed pulverized coal has a fineness of less than 200 mesh (0.074 mm). The mixed pulverized coal contains 21.93% volatile matter, 8.74% ash, and 69.33% fixed carbon by weight. The bituminous coal is as described above. The Shaanxi Fugu coal has a fineness of less than 200 mesh (0.074 mm) of 82.8% and a volatile matter content of 32.39%, an ash content of 7.08%, and a fixed carbon content of 60.53% by weight. The Shanxi Lu'an coal has a fineness of less than 200 mesh (0.074 mm) of 82.1% and a volatile matter content of 11.48%, an ash content of 10.39%, and a fixed carbon content of 78.13% by weight.

[0138] The second pulverized coal injection gun is inserted into the kiln head of the rotary kiln, about 5 meters away, with a pulverized coal injection rate of 0.6 t / h. The kiln head temperature is 1140-1160℃. The pulverized coal injected by the second pulverized coal injection gun is 100% anthracite, which is the aforementioned Shanxi Lu'an coal. The proportion of the fineness of the anthracite is less than 200 mesh (0.074 mm), and the volatile matter, ash content, and fixed carbon content are 11.48%, 10.39%, and 78.13% by weight.

[0139] The binary basicity (CaO / SiO2) of the finished pellet is 0.5.

[0140] The pellets produced using the production method described in Example 5 for reducing lumps formed during the roasting of alkaline pellets, after screening, showed that the proportion of large lumps with a particle size of 30-60 mm was 8.0%. Example 5 demonstrates that by changing the pulverized coal used for the second stage of preheating in the chain grate machine from anthracite to bituminous coal, and inserting two pulverized coal injection guns into the rotary kiln, with the second gun injecting 0.4 t / h more anthracite than in Example 1, the proportion of large lumps with a particle size of 30-60 mm in the pellets can be reduced by 2.3 percentage points compared to the control example. This effectively reduces the lumps formed during the roasting of alkaline pellets in the rotary kiln, thereby reducing the manual cleaning burden of unclogging the strip screen and ensuring normal production.

[0141] In summary, compared with the prior art, the production method of the present invention for reducing the agglomeration of alkaline pellets during roasting changes the pulverized coal used for the second stage of preheating of the chain grate machine from anthracite to bituminous coal, and changes the number of pulverized coal injection guns in the rotary kiln from one to two. One pulverized coal injection gun is located in the center of the rotary kiln, and the other pulverized coal injection gun is located at the kiln head of the rotary kiln and supplements the injection with an appropriate amount of anthracite. This can effectively reduce the agglomeration of alkaline pellets during the roasting process in the rotary kiln, thereby reducing the manual cleaning burden of unclogging the bar screen and ensuring normal production.

[0142] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A production method for reducing clumping in the process of sintering alkaline pellets, characterized in that, Comprise the following steps: Step one, batching and pelletizing Iron ore powder, limestone powder, bentonite are mixed uniformly by a mixer, then added into a disc pelletizer to pelletize by adding water, to produce green pellets with an average particle size of 8-16mm; Step two, roasting and cooling The material is distributed on a grate-kiln roasting device, preheating and roasting in the grate, high-temperature roasting in the rotary kiln, and cooling in a ring cooler to produce finished pellets, wherein: The pulverized coal for the second-stage preheating and reheating in the grate is bituminous coal, the volatile content of the bituminous coal is 29-35% by weight, the ash content is less than 10%, the fixed carbon content is greater than 58%, and the content of components with a particle size less than 200 mesh is controlled to be more than 80%; The coal injection guns in the rotary kiln are arranged in two, the first coal injection gun is inserted into the center of the rotary kiln, the pulverized coal injected by the first coal injection gun is a mixture of 50% bituminous coal and 50% anthracite, the content of components with a particle size less than 200 mesh in the mixed pulverized coal is controlled to be more than 80%, the volatile content of the mixed pulverized coal is 18-25% by weight, the ash content is less than 13%, and the fixed carbon content is greater than 67%; the second coal injection gun is inserted into the kiln head position of the rotary kiln, the pulverized coal injected by the second coal injection gun is 100% anthracite, the content of components with a particle size less than 200 mesh in the anthracite is controlled to be more than 80%, the volatile content of the anthracite is 9-12% by weight, the ash content is less than 11%, and the fixed carbon content is greater than 75%.

2. A production method for reducing clumping in the process of basic pellet induration according to claim 1, characterized in that, In the batching and pelletizing step, the moisture content of the green pellets is controlled to be 9.6% by weight, and the iron ore powder, limestone powder, and bentonite are weighed and batched according to the following weight proportions: Limestone powder 37 parts Iron ore powder 953 parts Bentonite 10 parts, The iron grade of the iron ore powder is 65.8%, the SiO2 content of the iron ore powder is 4.4% by weight, the FeO content is 17.5%, the particle size of the iron ore powder is 98.8% less than 325 mesh, the CaO content of the limestone powder is 51.8% by weight, and the particle size of the limestone powder is 95.7% less than 325 mesh.

3. The production method of reducing clumping in the process of basic pellet induration according to claim 1, characterized in that, In the roasting and cooling step, the coal injection amount of the bituminous coal injected in the second-stage preheating and reheating in the grate is controlled to be 1.22t / h, and the temperature of the smoke hood in the second-stage preheating and reheating in the grate is controlled to be 1150-1170℃.

4. A production method for reducing clumping in the process of basic pellet induration according to claim 3, characterized in that, In the roasting and cooling step, the first coal injection gun inserted into the center of the rotary kiln is 20 meters away from the kiln head, the coal injection amount is controlled to be 3.5-4.0t / h, the second coal injection gun inserted into the kiln head position of the rotary kiln is 5 meters away from the kiln head, the coal injection amount is controlled to be 0.2-0.6t / h, and the kiln head temperature of the rotary kiln is controlled to be 1140-1160℃.

5. The production method of reducing clumping in the process of basic pellet induration according to claim 1, characterized in that, The coal injection amount of the bituminous coal injected in the second-stage preheating and reheating in the grate is 1.22t / h; the first coal injection gun inserted into the center of the rotary kiln is 20 meters away from the kiln head, the coal injection amount is 3.92t / h, the content of components with a particle size less than 200 mesh in the mixed pulverized coal injected by the first coal injection gun is 82.3%, the volatile content of the mixed pulverized coal is 21.93% by weight, the ash content is 8.74%, and the fixed carbon content is 69.33%; the second coal injection gun inserted into the kiln head position of the rotary kiln is 5 meters away from the kiln head, the coal injection amount is 0.2t / h.

6. The production method of reducing clumping in the process of basic pellet induration according to claim 1, characterized in that, The chain grate preheating second stage sprays bituminous coal at a rate of 1.22t / h; the first coal injection gun inserted at the center of the rotary kiln is 20m from the kiln head, and sprays coal at a rate of 3.82t / h; the fine content of the mixed coal powder injected by the first coal injection gun is less than 200 mesh, accounting for 82.3% by weight; the volatile content of the mixed coal powder is 21.93% by weight, the ash content is 8.74% by weight, and the fixed carbon content is 69.33% by weight; the second coal injection gun inserted at the kiln head is 5m from the kiln head, and sprays coal at a rate of 0.3t / h.

7. The production method of reducing clumping in the process of basic pellet induration according to claim 1, characterized in that, The chain grate preheating second stage sprays bituminous coal at a rate of 1.22t / h; the first coal injection gun inserted at the center of the rotary kiln is 20m from the kiln head, and sprays coal at a rate of 3.72t / h; the fine content of the mixed coal powder injected by the first coal injection gun is less than 200 mesh, accounting for 82.3% by weight; the volatile content of the mixed coal powder is 21.93% by weight, the ash content is 8.74% by weight, and the fixed carbon content is 69.33% by weight; the second coal injection gun inserted at the kiln head is 5m from the kiln head, and sprays coal at a rate of 0.4t / h.

8. The production method of reducing clumping in the process of basic pellet induration according to claim 1, characterized in that, The chain grate preheating second stage sprays bituminous coal at a rate of 1.22t / h; the first coal injection gun inserted at the center of the rotary kiln is 20m from the kiln head, and sprays coal at a rate of 3.62t / h; the fine content of the mixed coal powder injected by the first coal injection gun is less than 200 mesh, accounting for 82.3% by weight; the volatile content of the mixed coal powder is 21.93% by weight, the ash content is 8.74% by weight, and the fixed carbon content is 69.33% by weight; the second coal injection gun inserted at the kiln head is 5m from the kiln head, and sprays coal at a rate of 0.5t / h.

9. The production method of reducing clumping in the process of basic pellet induration according to claim 1, characterized in that, The chain grate preheating second stage sprays bituminous coal at a rate of 1.22t / h; the first coal injection gun inserted at the center of the rotary kiln is 20m from the kiln head, and sprays coal at a rate of 3.52t / h; the fine content of the mixed coal powder injected by the first coal injection gun is less than 200 mesh, accounting for 82.3% by weight; the volatile content of the mixed coal powder is 21.93% by weight, the ash content is 8.74% by weight, and the fixed carbon content is 69.33% by weight; the second coal injection gun inserted at the kiln head is 5m from the kiln head, and sprays coal at a rate of 0.6t / h.

10. A production method for reducing clumping in a basic pellet ore roasting process according to any one of claims 1 to 9, characterized in that, The volatile content of the bituminous coal is 32.39% by weight, the ash content is 7.08% by weight, and the fixed carbon content is 60.53% by weight; the fine content of the bituminous coal is controlled at 82.8% by weight; the fine content of the anthracite is 82.1% by weight; the volatile content of the anthracite is 11.48% by weight, the ash content is 10.39% by weight, and the fixed carbon content is 78.13% by weight; the Al2O3 content of the anthracite in the mixed coal powder injected by the first coal injection gun is controlled at 5.75% by weight, and the Al2O3 content of the bituminous coal is controlled at 6.68% by weight.