Method for improving the compressive strength of chromium ore fines pellets

Abstract

The application discloses a method for improving the compressive strength of chromium ore powder pellets, which comprises the following steps: chromium ore powder batching and sintering, chromium sinter fine grinding, preparation of green pellets, and preparation of chromium ore pellets. In the method, lime and coke powder are added to the chromium ore powder, the chromium ore powder is first sintered into sinter on a sintering machine, the sinter is then crushed and finely ground, bentonite and water are added to the sinter to prepare green pellets with a particle size of 9-16 mm, and then the green pellets are put into a belt roaster to be prepared into chromium ore pellets according to a specified preheating, roasting and cooling procedure. The method for improving the compressive strength of the chromium ore powder pellets can improve the compressive strength of the chromium ore powder pellets by at least 370 N / pellet or more compared with the prior art without improving the roasting temperature of the belt roaster, so that the roasting temperature of the chromium ore powder in the belt roaster is lowered, the steel parts are prevented from being burnt, the probability of accidents is reduced, the equipment operation rate is improved, and the production efficiency of the chromium ore pellet belt production line is improved.

Description

Technical Field

[0001] This invention belongs to the field of chromite powder pellet production technology, and more specifically relates to a method for improving the compressive strength of chromite powder pellets. Background Technology

[0002] In existing technologies, when producing chromite pellets using belt conveyors, even with the high-temperature roasting section temperature increased to 1320–1350℃, the compressive strength of the finished chromite pellets remains around 2000 N / pellet, and in most cases, it falls below 2000 N / pellet. To improve the compressive strength of chromite pellets, the traditional method is to further increase the roasting temperature of the belt conveyor's high-temperature section. However, high-temperature roasting requires more heat-resistant steel components and refractory materials, increasing production and operating costs. Furthermore, it can easily damage steel components, potentially leading to accidents, and requires periodic shutdowns for maintenance, impacting equipment uptime.

[0003] Therefore, it is necessary to develop a method to improve the compressive strength of chromite powder pellets without increasing the roasting temperature during belt mill roasting. This would reduce the roasting temperature of chromite powder during belt mill roasting, thereby preventing damage to steel parts, reducing the probability of accidents, and improving equipment operating rate and production efficiency of the chromite pellet belt mill production line. Summary of the Invention

[0004] To address the technical problems existing in the prior art, the present invention provides a method for improving the compressive strength of chromite powder pellets, comprising the following steps:

[0005] Step 1: Chromium ore powder preparation and sintering

[0006] Weigh and mix the chromite powder, quicklime, and coke powder according to the following weight proportions, the specific ratio being:

[0007] 770-830 parts of chromite powder

[0008] 70-130 parts quicklime

[0009] 100 portions of caramel powder

[0010] Then mix well, add water, spread the mixture, and sinter it in a sintering machine to form a binary basicity of 0.7 to 1.5 chromium sinter.

[0011] Step 2: Fine grinding of chromium sinter

[0012] The chromium sinter is cooled, crushed, and finely ground into chromium sinter powder, and the proportion of particles with a particle size of less than 200 mesh in the chromium sinter powder is controlled to be more than 75%.

[0013] Step 3: Preparation of raw mineral pellets

[0014] The chromium sinter powder and bentonite are weighed and mixed according to the following weight proportions, the specific ratio being:

[0015] 985-990 parts of chromium sintered ore powder

[0016] 10-15 parts of bentonite

[0017] Then water is added, and raw pellets with a particle size of 9-16 mm are prepared in a disc pelletizer;

[0018] Step 4: Preparation of chromite pellets

[0019] Raw ore pellets are fed and roasted on a belt roaster. The roasting temperature in the high-temperature section is controlled at 1320-1340℃. After high-temperature roasting, the finished chromite pellets are obtained by cooling on the machine.

[0020] As one implementation method, in the above-described method for improving the compressive strength of chromite powder pellets:

[0021] In step one, the ratio of chromite powder, quicklime, and coke powder is as follows:

[0022] 829 parts of chromite powder

[0023] 71 parts quicklime

[0024] 100 portions of caramel powder

[0025] The binary basicity of chromium sinter is 0.8;

[0026] In step two, the proportion of particles with a diameter less than 200 mesh in the chromium sinter powder is 77.5%;

[0027] In step three, the ratio of chromium sinter powder to bentonite is:

[0028] 985 parts of chromium sintered ore powder

[0029] 15 parts bentonite;

[0030] In step four, the high-temperature roasting temperature is 1320℃ and the high-temperature roasting time is 27 minutes.

[0031] As one implementation method, in the above-described method for improving the compressive strength of chromite powder pellets:

[0032] In step one, the ratio of chromite powder, quicklime, and coke powder is as follows:

[0033] 810 parts of chromite powder

[0034] 90 parts quicklime

[0035] 100 portions of caramel powder

[0036] The binary basicity of chromium sinter is 1.0;

[0037] In step two, the proportion of particles with a diameter less than 200 mesh in the chromium sinter powder is 77.5%;

[0038] In step three, the ratio of chromium sinter powder to bentonite is:

[0039] 987 parts of chromium sintered ore powder

[0040] 13 parts bentonite;

[0041] In step four, the high-temperature roasting temperature is 1320℃, and the high-temperature roasting time is 27 minutes. As one embodiment, in the above method for improving the compressive strength of chromite powder pellets: in step one, the ratio of chromite powder, quicklime, and coke powder is:

[0042] 793 parts of chromite powder

[0043] 107 parts quicklime

[0044] 100 portions of caramel powder

[0045] The binary basicity of chromium sinter is 1.2;

[0046] In step two, the proportion of particles with a diameter less than 200 mesh in the chromium sinter powder is 77.5%;

[0047] In step three, the ratio of chromium sinter powder to bentonite is:

[0048] 988 parts of chromium sintered ore powder

[0049] 12 parts bentonite;

[0050] In step four, the high-temperature roasting temperature is 1320℃, and the high-temperature roasting time is 27 minutes. As one embodiment, in the above method for improving the compressive strength of chromite powder pellets: in step one, the ratio of chromite powder, quicklime, and coke powder is:

[0051] 776 parts of chromite powder

[0052] 124 parts quicklime

[0053] 100 portions of caramel powder

[0054] The binary basicity of chromium sinter is 1.4;

[0055] In step two, the proportion of particles with a diameter less than 200 mesh in the chromium sinter powder is 77.5%;

[0056] In step three, the ratio of chromium sinter powder to bentonite is:

[0057] 990 parts of chromium sintered ore powder

[0058] 10 parts bentonite;

[0059] In step four, the high-temperature roasting temperature is 1320℃, and the high-temperature roasting time is 27 minutes. As one embodiment, in the above method for improving the compressive strength of chromite powder pellets: in step one, the ratio of chromite powder, quicklime, and coke powder is:

[0060] 810 parts of chromite powder

[0061] 90 parts quicklime

[0062] 100 portions of caramel powder

[0063] The binary basicity of chromium sinter is 1.0;

[0064] In step two, the proportion of particles with a particle size smaller than 200 mesh in the chromium sinter powder is 77.5%;

[0065] In step three, the ratio of chromium sinter powder to bentonite is:

[0066] 987 parts of chromium sintered ore powder

[0067] 13 parts bentonite;

[0068] In step four, the high-temperature roasting temperature is 1340℃ and the high-temperature roasting time is 27 minutes.

[0069] Furthermore, in the above-mentioned method for improving the compressive strength of chromite powder pellets, the chromite powder is Turkish chromite powder with an original chromium grade of 26.37% and an iron grade of 14.1%. The chromite powder contains, by weight percentage, 8.75% SiO2, 0.6% CaO, 9.54% Al2O3, and 20.6% MgO, and the proportion of particles smaller than 200 mesh is 28.3%. The quicklime contains, by weight percentage, 83% CaO and 2.1% SiO2. The coke powder has a fixed carbon content of 83.2%, an ash content of 12.2%, and the proportion of particles smaller than 3 mm is 78%.

[0070] The method for improving the compressive strength of chromite powder pellets according to the present invention has the following advantages and beneficial effects: Chromite powder is mixed with quicklime and coke powder, first sintered in a sintering machine to form sinter, then crushed, finely ground, and mixed with bentonite and water to prepare raw pellets with a particle size of 9-16 mm. These raw pellets are then fed into a belt roaster and processed according to a prescribed preheating, roasting, and cooling procedure to produce chromite pellets. The method of the present invention can increase the compressive strength of chromite powder pellets by at least 370 N / pellet compared to existing technologies without increasing the roasting temperature during belt roasting. This reduces the roasting temperature of the chromite powder during belt roasting, thus preventing damage to steel components, reducing the probability of accidents, and improving equipment operating rate and the production efficiency of the chromite pellet belt roaster production line. Detailed Implementation

[0071] 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.

[0072] The method for improving the compressive strength of chromite powder pellets according to the present invention generally includes: adding quicklime and coke powder to chromite powder, first sintering it in a sintering machine to produce sinter, then crushing and finely grinding the sinter, adding bentonite and water to prepare raw pellets with a particle size of 9-16 mm, and then feeding them into a belt roaster according to a prescribed preheating, roasting, and cooling procedure to produce chromite pellets. The method of the present invention can improve the compressive strength of chromite powder pellets without increasing the roasting temperature during belt roasting, thereby avoiding damage to steel parts, reducing the probability of accidents, and improving equipment operating rate and production efficiency of the chromite pellet belt roaster production line by lowering the roasting temperature of the chromite powder during belt roasting.

[0073] Specifically, the method of the present invention for improving the compressive strength of chromite powder pellets includes the following steps:

[0074] Step 1: Chromium ore powder preparation and sintering

[0075] Weigh and mix the chromite powder, quicklime, and coke powder according to the following weight proportions, the specific ratio being:

[0076] 770-830 parts of chromite powder

[0077] 70-130 parts quicklime

[0078] 100 portions of caramel powder

[0079] Then mix well, add water, spread the mixture, and sinter it in a sintering machine to form chromium sinter with a binary basicity (CaO / SiO2) of 0.7 to 1.5;

[0080] Step 2: Fine grinding of chromium sinter

[0081] The above-mentioned chromium sinter is cooled, crushed, and finely ground into chromium sinter powder. The proportion of particles with a particle size of less than 200 mesh (0.074 mm) in the chromium sinter powder is controlled to be more than 75%.

[0082] Step 3: Preparation of raw mineral pellets

[0083] The above-mentioned chromium sintered ore powder and bentonite are weighed and mixed according to the following weight proportions, the specific ratio being:

[0084] 985-990 parts of chromium sintered ore powder

[0085] 10-15 parts of bentonite

[0086] Then water is added, and raw pellets with a particle size of 9-16 mm are prepared in a disc pelletizer;

[0087] Step 4: Preparation of chromite pellets

[0088] The above-mentioned raw ore pellets are fed and roasted on a belt roaster. The roasting temperature in the high-temperature section is controlled at 1320-1340℃. After high-temperature roasting, the finished chromite pellets are obtained by cooling on the machine.

[0089] In one specific embodiment, in the method for improving the compressive strength of chromite powder pellets of the present invention, the chromite powder is Turkish chromite powder with an original chromium grade of 26.37% and an iron grade of 14.1%. The chromite powder contains, by weight percentage, 8.75% SiO2, 0.6% CaO, 9.54% Al2O3, and 20.6% MgO. The proportion of particles with a diameter less than 200 mesh (0.074 mm) in the chromite powder is 28.3%. The quicklime contains, by weight percentage, 83% CaO and 2.1% SiO2. The coke powder has a fixed carbon content of 83.2% and an ash content of 12.2%, of which 78% are particles with a diameter less than 3 mm.

[0090] The following comparative examples and embodiments further illustrate the specific implementation of the method for improving the compressive strength of chromite powder pellets according to the present invention.

[0091] Compare with Example 1

[0092] As a comparative example 1, the conventional method for producing chromite pellets using a belt conveyor includes the following steps:

[0093] (1) Fine grinding of chromite powder

[0094] The chromite powder was finely ground, and the proportion of particles with a diameter less than 200 mesh (0.074 mm) after fine grinding was 78.8%. The chromite powder was Turkish chromite powder, with an original chromium grade of 26.37% and an iron grade of 14.1%. The chromite powder contained, by weight percentage, 8.75% SiO2, 0.6% CaO, 9.54% Al2O3, and 20.6% MgO. The proportion of particles with a diameter less than 200 mesh (0.074 mm) in the chromite powder was 28.3%.

[0095] (2) Ingredients

[0096] The finely ground chromite powder and bentonite are weighed and mixed according to the following weight proportions, the specific ratio being:

[0097] 987 parts of chromite powder

[0098] 13 parts of bentonite

[0099] Among them, bentonite refers to conventional bentonite that is available on the market.

[0100] (3) Mixing and pelletizing

[0101] The above-mentioned chromite powder and bentonite are mixed evenly by a mixer, and then added to a disc pelletizer with water to produce green pellets. The moisture content of the green pellets is 9.7% by weight, and the average particle size of the green pellets is 9-16 mm.

[0102] (4) Belt press preheating and cooling

[0103] The material is fed and roasted on a belt roasting machine, and then cooled on the machine to obtain finished chromite pellets. The high-temperature roasting temperature is 1320℃ and the high-temperature roasting time is 27min.

[0104] Experimental tests were conducted on the finished chromite pellets prepared as described above, and their compressive strength was 1867 N / pellet.

[0105] The above-mentioned comparative example 1 shows that after the chromite powder is finely ground into pellets and then calcined at a high temperature of 1320°C using a belt mill, its compressive strength is only 1867 N / pellet.

[0106] Compare with Example 2

[0107] As a comparative example 2, the conventional method for producing chromite pellets using a belt conveyor includes the following steps:

[0108] (1) Fine grinding of chromite powder

[0109] The chromite powder was finely ground, and the proportion of particles with a diameter less than 200 mesh (0.074 mm) after fine grinding was 78.8%. The chromite powder was Turkish chromite powder, with an original chromium grade of 26.37% and an iron grade of 14.1%. The chromite powder contained, by weight percentage, 8.75% SiO2, 0.6% CaO, 9.54% Al2O3, and 20.6% MgO. The proportion of particles with a diameter less than 200 mesh (0.074 mm) in the chromite powder was 28.3%.

[0110] (2) Ingredients

[0111] The finely ground chromite powder and bentonite are weighed and mixed according to the following weight proportions, the specific ratio being:

[0112] 987 parts of chromite powder

[0113] 13 parts of bentonite

[0114] Among them, bentonite refers to conventional bentonite that is available on the market.

[0115] (3) Mixing and pelletizing

[0116] The above-mentioned chromite powder and bentonite are mixed evenly by a mixer, and then added to a disc pelletizer with water to produce green pellets. The moisture content of the green pellets is 9.7% by weight, and the average particle size of the green pellets is 9-16 mm.

[0117] (4) Belt press preheating and cooling

[0118] The material is fed and roasted on a belt mill roasting equipment, and then cooled on the machine to obtain finished chromite pellets. The high-temperature roasting temperature is 1340℃ and the high-temperature roasting time is 27min.

[0119] The finished chromite pellets prepared as described above were tested, and their compressive strength was 2113 N / pellet.

[0120] The above-mentioned Comparative Example 2 shows that after the chromite powder is finely ground into pellets and then calcined at a high temperature of 1340°C using a belt mill, its compressive strength is 2113 N / pellet, which is only 246 N / pellet higher than that of Comparative Example 1 when the belt mill calcination temperature is 1320°C.

[0121] Example 1

[0122] In Example 1 of this invention, chromite powder is first mixed with quicklime powder and coke powder, sintered into a binary sinter with a basicity of 0.8, then finely ground into powder, and bentonite and water are added to prepare green pellets. These green pellets are then roasted on a belt mill to obtain chromite pellets. Example 1 specifically includes the following steps:

[0123] Step 1: Chromium ore powder preparation and sintering

[0124] Weigh and mix the chromite powder, quicklime, and coke powder according to the following weight proportions, the specific ratio being:

[0125] 829 parts of chromite powder

[0126] 71 parts quicklime

[0127] 100 portions of caramel powder

[0128] Then mix well, add water, spread the mixture, and sinter it in a sintering machine to form a chromium sinter with a binary basicity (CaO / SiO2) of 0.8;

[0129] Step 2: Fine grinding of chromium sinter

[0130] The above-mentioned chromium sinter is cooled, crushed, and finely ground into chromium sinter powder. The proportion of particles with a particle size of less than 200 mesh (0.074 mm) in the chromium sinter powder is controlled to be 77.5%.

[0131] Step 3: Preparation of raw mineral pellets

[0132] The above-mentioned chromium sintered ore powder and bentonite are weighed and mixed according to the following weight proportions, the specific ratio being:

[0133] 985 parts of chromium sintered ore powder

[0134] 15 parts of bentonite

[0135] Then water is added, and raw pellets with a particle size of 9-16 mm are prepared in a disc pelletizer;

[0136] Step 4: Preparation of chromite pellets

[0137] The above-mentioned raw ore pellets are fed and roasted on a belt roaster. The roasting temperature in the high-temperature section is controlled at 1320℃ and the roasting time in the high-temperature section is 27 minutes. After high-temperature roasting, the finished chromite pellets are obtained by cooling on the machine.

[0138] Experimental tests were conducted on the finished chromite pellets prepared using Example 1, and the compressive strength of the finished chromite pellets was 2237 N / pellet.

[0139] The test results of Example 1 show that when chromite powder is first mixed with quicklime powder and coke powder and sintered into a sinter with a binary basicity of 0.8, then finely ground into mineral powder, bentonite and water are added to prepare green pellets, and then roasted on a belt mill, compared with Control Example 1, at the same roasting temperature of 1320℃, the compressive strength of the finished pellets of Example 1 reaches 2237 N / ball, which is 370 N / ball higher than that of Control Example 1; even compared with Control Example 2, which has a higher roasting temperature of 1340℃, the compressive strength of the finished pellets of Example 1 is 124 N / ball higher.

[0140] Example 2

[0141] In Example 2 of this invention, the binary basicity of the sinter is increased to 1.0, specifically including the following steps:

[0142] Step 1: Chromium ore powder preparation and sintering

[0143] Weigh and mix the chromite powder, quicklime, and coke powder according to the following weight proportions, the specific ratio being:

[0144] 810 parts of chromite powder

[0145] 90 parts quicklime

[0146] 100 portions of caramel powder

[0147] Then mix well, add water, spread the mixture, and sinter it in a sintering machine to form a chromium sinter with a binary basicity (CaO / SiO2) of 1.0;

[0148] Step 2: Fine grinding of chromium sinter

[0149] The above-mentioned chromium sinter is cooled, crushed, and finely ground into chromium sinter powder. The proportion of particles with a particle size of less than 200 mesh (0.074 mm) in the chromium sinter powder is controlled to be 77.5%.

[0150] Step 3: Preparation of raw mineral pellets

[0151] The above-mentioned chromium sintered ore powder and bentonite are weighed and mixed according to the following weight proportions, the specific ratio being:

[0152] 987 parts of chromium sintered ore powder

[0153] 13 parts of bentonite

[0154] Then water is added, and raw pellets with a particle size of 9-16 mm are prepared in a disc pelletizer;

[0155] Step 4: Preparation of chromite pellets

[0156] The above-mentioned raw ore pellets are fed and roasted on a belt roaster. The roasting temperature in the high-temperature section is controlled at 1320℃ and the roasting time in the high-temperature section is 27 minutes. After high-temperature roasting, the finished chromite pellets are obtained by cooling on the machine.

[0157] Experimental tests were conducted on the finished chromite pellets prepared using Example 2, and the compressive strength of the finished chromite pellets was 2388 N / pellet.

[0158] The test results of Example 2 show that when chromite powder is first mixed with quicklime powder and coke powder and sintered into a sinter with a binary basicity of 1.0, then finely ground into mineral powder, bentonite and water are added to prepare green pellets, and then roasted on a belt mill, compared with Control Example 1, at the same roasting temperature of 1320℃, the compressive strength of the finished pellets of Example 2 reaches 2388 N / ball, which is 521 N / ball higher than that of Control Example 1; even compared with Control Example 2 with a higher roasting temperature of 1340℃, the compressive strength of the finished pellets of Example 2 is 275 N / ball higher.

[0159] Example 3

[0160] In Example 3 of this invention, the binary basicity of the sinter is increased to 1.2, specifically including the following steps:

[0161] Step 1: Chromium ore powder preparation and sintering

[0162] Weigh and mix the chromite powder, quicklime, and coke powder according to the following weight proportions, the specific ratio being:

[0163] 793 parts of chromite powder

[0164] 107 parts quicklime

[0165] 100 portions of caramel powder

[0166] Then mix well, add water, spread the mixture, and sinter it in a sintering machine to form a chromium sinter with a binary basicity (CaO / SiO2) of 1.2;

[0167] Step 2: Fine grinding of chromium sinter

[0168] The above-mentioned chromium sinter is cooled, crushed, and finely ground into chromium sinter powder. The proportion of particles with a particle size of less than 200 mesh (0.074 mm) in the chromium sinter powder is controlled to be 77.5%.

[0169] Step 3: Preparation of raw mineral pellets

[0170] The above-mentioned chromium sintered ore powder and bentonite are weighed and mixed according to the following weight proportions, the specific ratio being:

[0171] 988 parts of chromium sintered ore powder

[0172] 12 parts of bentonite

[0173] Then water is added, and raw pellets with a particle size of 9-16 mm are prepared in a disc pelletizer;

[0174] Step 4: Preparation of chromite pellets

[0175] The above-mentioned raw ore pellets are fed and roasted on a belt roaster. The roasting temperature in the high-temperature section is controlled at 1320℃ and the roasting time in the high-temperature section is 27 minutes. After high-temperature roasting, the finished chromite pellets are obtained by cooling on the machine.

[0176] Experimental tests were conducted on the finished chromite pellets prepared using Example 3, and the compressive strength of the finished chromite pellets was 2501 N / pellet.

[0177] The test results of Example 3 show that when chromite powder is first mixed with quicklime powder and coke powder and sintered into a sinter with a binary basicity of 1.2, then finely ground into mineral powder, bentonite and water are added to prepare green pellets, and then roasted on a belt mill, compared with Control Example 1, at the same roasting temperature of 1320℃, the compressive strength of the finished pellets in Example 3 reaches 2501 N / ball, which is 634 N / ball higher than that of Control Example 1; even compared with Control Example 2, which has a higher roasting temperature of 1340℃, the compressive strength of the finished pellets in Example 3 is 388 N / ball higher.

[0178] Example 4

[0179] In Example 4 of this invention, the binary basicity of the sinter is increased to 1.4, specifically including the following steps:

[0180] Step 1: Chromium ore powder preparation and sintering

[0181] Weigh and mix the chromite powder, quicklime, and coke powder according to the following weight proportions, the specific ratio being:

[0182] 776 parts of chromite powder

[0183] 124 parts quicklime

[0184] 100 portions of caramel powder

[0185] Then mix well, add water, spread the mixture, and sinter it in a sintering machine to form a chromium sinter with a binary basicity (CaO / SiO2) of 1.4;

[0186] Step 2: Fine grinding of chromium sinter

[0187] The above-mentioned chromium sinter is cooled, crushed, and finely ground into chromium sinter powder. The proportion of particles with a particle size of less than 200 mesh (0.074 mm) in the chromium sinter powder is controlled to be 77.5%.

[0188] Step 3: Preparation of raw mineral pellets

[0189] The above-mentioned chromium sintered ore powder and bentonite are weighed and mixed according to the following weight proportions, the specific ratio being:

[0190] 990 parts of chromium sintered ore powder

[0191] 10 parts bentonite

[0192] Then water is added, and raw pellets with a particle size of 9-16 mm are prepared in a disc pelletizer;

[0193] Step 4: Preparation of chromite pellets

[0194] The above-mentioned raw ore pellets are fed and roasted on a belt roaster. The roasting temperature in the high-temperature section is controlled at 1320℃ and the roasting time in the high-temperature section is 27 minutes. After high-temperature roasting, the finished chromite pellets are obtained by cooling on the machine.

[0195] Experimental tests were conducted on the finished chromite pellets prepared using Example 4, and the compressive strength of the finished chromite pellets was 2533 N / pellet.

[0196] The test results of Example 4 show that when chromite powder is first mixed with quicklime powder and coke powder and sintered into a sinter with a binary basicity of 1.4, then finely ground into mineral powder, bentonite and water are added to prepare green pellets, and then roasted on a belt mill, compared with Control Example 1, at the same roasting temperature of 1320℃, the compressive strength of the finished pellets of Example 4 reaches 2533 N / ball, which is 666 N / ball higher than that of Control Example 1; even compared with Control Example 2 with a higher roasting temperature of 1340℃, the compressive strength of the finished pellets of Example 4 is 420 N / ball higher.

[0197] Example 5

[0198] Example 5 of the present invention is similar to Example 2, with the binary basicity of the sinter being 1.0, but the roasting temperature of the high-temperature section of the belt mill is increased from 1320℃ to 1340℃. Specifically, it includes the following steps:

[0199] Step 1: Chromium ore powder preparation and sintering

[0200] Weigh and mix the chromite powder, quicklime, and coke powder according to the following weight proportions, the specific ratio being:

[0201] 810 parts of chromite powder

[0202] 90 parts quicklime

[0203] 100 portions of caramel powder

[0204] Then mix well, add water, spread the mixture, and sinter it in a sintering machine to form a chromium sinter with a binary basicity (CaO / SiO2) of 1.0;

[0205] Step 2: Fine grinding of chromium sinter

[0206] The above-mentioned chromium sinter is cooled, crushed, and finely ground into chromium sinter powder. The proportion of particles with a particle size of less than 200 mesh (0.074 mm) in the chromium sinter powder is controlled to be 77.5%.

[0207] Step 3: Preparation of raw mineral pellets

[0208] The above-mentioned chromium sintered ore powder and bentonite are weighed and mixed according to the following weight proportions, the specific ratio being:

[0209] 987 parts of chromium sintered ore powder

[0210] 13 parts of bentonite

[0211] Then water is added, and raw pellets with a particle size of 9-16 mm are prepared in a disc pelletizer;

[0212] Step 4: Preparation of chromite pellets

[0213] The above-mentioned raw ore pellets are fed and roasted on a belt roaster. The roasting temperature in the high-temperature section is controlled at 1340℃ and the roasting time in the high-temperature section is 27 minutes. After high-temperature roasting, the finished chromite pellets are obtained by cooling on the machine.

[0214] Experimental tests were conducted on the finished chromite pellets prepared using Example 5, and the compressive strength of the finished chromite pellets was 2611 N / pellet.

[0215] The test results of Example 5 show that when chromite powder is first mixed with quicklime powder and coke powder and sintered into a sinter with a binary basicity of 1.0, it is then finely ground into mineral powder, and bentonite and water are added to prepare green pellets. Then, it is roasted on a belt mill at a high-temperature roasting temperature of 1340℃. Compared with Control Example 2, at the same roasting temperature of 1340℃, the compressive strength of the finished pellets in Example 5 reaches 2611 N / ball, which is 498 N / ball higher than that of Control Example 2. Compared with Example 2 of the present invention, which has the same binary basicity of 1.0 but a high-temperature roasting temperature of 1320℃, the compressive strength of the finished pellets in Example 5 is also increased by 223 N / ball.

[0216] In summary, compared with the prior art, the method of the present invention for improving the compressive strength of chromite powder pellets involves first sintering chromite powder with quicklime and coke powder in a sintering machine to produce sinter, then crushing and finely grinding the sinter, adding bentonite and water to prepare raw pellets with a particle size of 9-16 mm, and then feeding them into a belt roaster for preheating, roasting, and cooling according to a prescribed procedure to produce chromite pellets. The method of the present invention can increase the compressive strength of chromite powder pellets by at least 370 N / pellet compared to the prior art without increasing the roasting temperature during belt roasting. This reduces the roasting temperature of the chromite powder in the belt roaster, thus preventing damage to steel parts, reducing the probability of accidents, and improving equipment operating rate and the production efficiency of the chromite pellet belt roaster production line.

[0217] 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 method for improving the compressive strength of chromite powder pellets, characterized in that, Includes the following steps: Step 1: Chromium ore powder preparation and sintering Weigh and mix the chromite powder, quicklime, and coke powder according to the following weight proportions, the specific ratio being: 770-830 parts of chromite powder 70-130 parts quicklime 100 portions of caramel powder Then mix well, add water, spread the mixture, and sinter it in a sintering machine to form a chromium sinter with a binary basicity of 0.7~1.5; Step 2: Fine grinding of chromium sinter The chromium sinter is cooled, crushed, and finely ground into chromium sinter powder, and the proportion of particles with a particle size of less than 200 mesh in the chromium sinter powder is controlled to be more than 75%. Step 3: Preparation of raw mineral pellets The chromium sinter powder and bentonite are weighed and mixed according to the following weight proportions, the specific ratio being: 985-990 parts of chromium sintered ore powder 10-15 parts of bentonite Then water is added, and raw pellets with a particle size of 9-16 mm are prepared in a disc pelletizer; Step 4: Preparation of chromite pellets Raw ore pellets are fed and roasted on a belt roaster. The roasting temperature in the high-temperature section is controlled at 1320~1340℃. After high-temperature roasting, the finished chromite pellets are obtained by cooling on the machine. The chromium ore powder is Turkish chromium ore powder, with an original chromium grade of 26.37% and an iron grade of 14.1%. The chromium ore powder contains, by weight percentage, 8.75% SiO2, 0.6% CaO, 9.54% Al2O3, and 20.6% MgO, and 28.3% of the particles are smaller than 200 mesh. The quicklime contains, by weight percentage, 83% CaO and 2.1% SiO2. The coke powder has a fixed carbon content of 83.2%, an ash content of 12.2%, and 78% of the particles are smaller than 3 mm.

2. The method for improving the compressive strength of chromite powder pellets according to claim 1, characterized in that: In step one, the ratio of chromite powder, quicklime, and coke powder is as follows: 829 parts of chromite powder 71 parts quicklime 100 portions of caramel powder The binary basicity of chromium sinter is 0.8; In step two, the proportion of particles with a diameter less than 200 mesh in the chromium sinter powder is 77.5%; In step three, the ratio of chromium sinter powder to bentonite is: 985 parts of chromium sintered ore powder 15 parts bentonite; In step four, the high-temperature roasting temperature is 1320℃ and the high-temperature roasting time is 27 minutes.

3. The method for improving the compressive strength of chromite powder pellets according to claim 1, characterized in that: In step one, the ratio of chromite powder, quicklime, and coke powder is as follows: 810 parts of chromite powder 90 parts quicklime 100 portions of caramel powder The binary basicity of chromium sinter is 1.0; In step two, the proportion of particles with a diameter less than 200 mesh in the chromium sinter powder is 77.5%; In step three, the ratio of chromium sinter powder to bentonite is: 987 parts of chromium sintered ore powder 13 parts bentonite; In step four, the high-temperature roasting temperature is 1320℃ and the high-temperature roasting time is 27 minutes.

4. The method for improving the compressive strength of chromite powder pellets according to claim 1, characterized in that: In step one, the ratio of chromite powder, quicklime, and coke powder is as follows: 793 parts of chromite powder 107 parts quicklime 100 portions of caramel powder The binary basicity of chromium sinter is 1.2; In step two, the proportion of particles with a diameter less than 200 mesh in the chromium sinter powder is 77.5%; In step three, the ratio of chromium sinter powder to bentonite is: 988 parts of chromium sintered ore powder 12 parts bentonite; In step four, the high-temperature roasting temperature is 1320℃ and the high-temperature roasting time is 27 minutes.

5. The method for improving the compressive strength of chromite powder pellets according to claim 1, characterized in that: In step one, the ratio of chromite powder, quicklime, and coke powder is as follows: 776 parts of chromite powder 124 parts quicklime 100 portions of caramel powder The binary basicity of chromium sinter is 1.4; In step two, the proportion of particles with a diameter less than 200 mesh in the chromium sinter powder is 77.5%; In step three, the ratio of chromium sinter powder to bentonite is: 990 parts of chromium sintered ore powder 10 parts bentonite; In step four, the high-temperature roasting temperature is 1320℃ and the high-temperature roasting time is 27 minutes.

6. The method for improving the compressive strength of chromite powder pellets according to claim 1, characterized in that: In step one, the ratio of chromite powder, quicklime, and coke powder is as follows: 810 parts of chromite powder 90 parts quicklime 100 portions of caramel powder The binary basicity of chromium sinter is 1.0; In step two, the proportion of particles with a diameter less than 200 mesh in the chromium sinter powder is 77.5%; In step three, the ratio of chromium sinter powder to bentonite is: 987 parts of chromium sintered ore powder 13 parts bentonite; In step four, the high-temperature roasting temperature is 1340℃ and the high-temperature roasting time is 27 minutes.