CN115595436A - Method for reducing agglomeration of pre-reduced chromium ore pellets - Google Patents
Method for reducing agglomeration of pre-reduced chromium ore pellets Download PDFInfo
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- CN115595436A CN115595436A CN202211384083.XA CN202211384083A CN115595436A CN 115595436 A CN115595436 A CN 115595436A CN 202211384083 A CN202211384083 A CN 202211384083A CN 115595436 A CN115595436 A CN 115595436A
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Abstract
The invention belongs to the technical field of iron material pellets for blast furnace ironmaking, and particularly relates to a method for reducing agglomeration of pre-reduced chromium ore pellets, which comprises the following steps: (1) Performing fine grinding pretreatment on a mixture of chromium ore powder and coke powder, adding bentonite, and then sending to pelletization to obtain green pellets; (2) Preheating and roasting the green pellets, and then, feeding the green pellets into a rotary kiln for reduction roasting; (3) Directly feeding the pellets subjected to reduction roasting into a shaft kiln, and introducing hydrogen for cooling; (4) And discharging the cooled pellets, and then smelting in an ore furnace. The pellets internally provided with coke powder are pre-reduced at high temperature by the rotary kiln, then are directly added into the shaft kiln, and are introduced with hydrogen for cooling, and the cooled pellets are discharged and then are carried into the submerged arc furnace through the metal hopper for smelting, so that the agglomeration of the pre-reduced chromium ore pellets can be reduced, and the reduction rate of iron oxides in the chromium ore pellets is not reduced.
Description
Technical Field
The invention belongs to the technical field of iron material pellets for blast furnace iron making, and particularly relates to a method for reducing agglomeration of pre-reduced chromium ore pellets.
Background
At present, the main process flow for producing chromium-containing molten iron by using rotary kiln pre-reduced iron ore pellets is as follows: the chromium ore powder is mixed with coke powder, then is finely ground and pelletized, and then is subjected to high-temperature reduction roasting in a rotary kiln to obtain pre-reduced pellets, and then is added into an ore heating furnace to be smelted to obtain iron-containing molten iron. By adopting the process, the high-temperature pre-reduced chrome ore pellets are transported after being discharged from the kiln head of the rotary kiln and before entering the submerged arc furnace for smelting, pass through the ore tank and then enter the submerged arc furnace. However, the chrome ore pellets after high-temperature reduction roasting in the rotary kiln are easy to form large blocks of hardening after entering an ore tank due to the temperature of over 1200 ℃, so that the blanking is not smooth, and the normal production is influenced. Therefore, only proper air blowing can be carried out in the ore tank to reduce the temperature of the high-temperature chrome ore pellets, but after the air blowing, the pre-reduced pellets are re-oxidized, which is equivalent to weakening the effect of the high-temperature pre-reduction in the rotary kiln.
Therefore, whether to develop a method which can reduce agglomeration of the pre-reduced chrome ore pellets and does not reduce the reduction rate of iron oxides in the chrome ore pellets is beneficial to improving the efficiency of pre-reducing the chrome ore pellets at high temperature in the rotary kiln.
Disclosure of Invention
The invention aims to provide a method for reducing agglomeration of pre-reduced chrome ore pellets aiming at the defects of the prior art.
Specifically, the method for reducing agglomeration of the pre-reduced chrome ore pellets comprises the following steps:
(1) Performing fine grinding pretreatment on a mixture of chromium ore powder and coke powder, adding bentonite, and then conveying to pelletize to obtain green pellets;
(2) The green pellets are preheated and roasted and then enter a rotary kiln for reduction roasting;
(3) Directly feeding the pellets subjected to reduction roasting into a shaft kiln, and introducing hydrogen for cooling;
(4) And discharging the cooled pellets, and then smelting in a submerged arc furnace.
According to the method for reducing agglomeration of the pre-reduced chromium ore pellets, the water content of the green pellets is 10-11wt%, wherein the weight ratio of the chromium ore powder to the coke powder to the bentonite is 800-900:50-200:8-15.
According to the method for reducing agglomeration of the pellets of the pre-reduced chromium ore, the temperature of the kiln head hot air of the rotary kiln is 1000-1150 ℃, and the retention time of the green pellets in the kiln is 200-260 minutes.
According to the method for reducing agglomeration of the pre-reduced chrome ore pellets, the temperature of the kiln head hot air of the rotary kiln is 1080 ℃, and the green pellets stay in the kiln for 230 minutes.
According to the method for reducing agglomeration of the pellets of the pre-reduced chromium ore, the temperature of the pellets entering the shaft kiln is 1100-1300 ℃.
In the method for relieving agglomeration of the pre-reduced chromium ore pellets, the adding amount of the hydrogen is 90-150m 3 Pellets per ton.
In the method for relieving agglomeration of the pre-reduced chrome ore pellets, the temperature of the cooled pellets is 600-800 ℃.
According to the method for reducing agglomeration of the pre-reduced chromium ore pellets, the weight ratio of the chromium ore powder to the coke powder is 880:120, the adding amount of the hydrogen is 105m 3 Pellets/t, 115m 3 Pellet/t, 125m 3 Pellets/t or 145m 3 Pellets per ton.
According to the method for reducing agglomeration of the pre-reduced chromium ore pellets, the weight ratio of the chromium ore powder to the coke powder is 900:100, the adding amount of the hydrogen is 145m 3 Pellets per ton.
According to the method for reducing agglomeration of the pre-reduced chromium ore pellets, the Cr of the chromium ore powder is calculated according to the weight percentage 2 O 3 ＝38-50％，Cr/Fe＝1-2,SiO 2 ＝2-6％，MgO＝5-20％，Al 2 O 3 ＝5-25％。
The technical scheme of the invention has the following beneficial effects:
the pellets internally provided with coke powder are pre-reduced at high temperature by the rotary kiln, then are directly added into the shaft kiln, and are introduced with hydrogen for cooling, and the cooled pellets are discharged and then are carried into the submerged arc furnace through the metal hopper for smelting, so that the agglomeration of the pre-reduced chromium ore pellets can be reduced, and the reduction rate of iron oxides in the chromium ore pellets is not reduced.
Detailed Description
The invention will be described in detail with reference to the following detailed description for fully understanding the objects, features and effects of the invention. The process of the present invention employs conventional methods or apparatus in the art, except as described below. The following terms have the meanings commonly understood by those skilled in the art, unless otherwise specified.
When a range of values is disclosed herein, the range is considered to be continuous and includes both the minimum and maximum values of the range, as well as each value between such minimum and maximum values. Further, when a range refers to an integer, each integer between the minimum and maximum values of the range is included. Further, when multiple range-describing features or characteristics are provided, the ranges may be combined. In other words, unless otherwise indicated, all ranges disclosed herein are to be understood to encompass any and all subranges subsumed therein.
The invention aims to reduce agglomeration of pre-reduced chrome ore pellets without reducing the reduction rate of iron oxide in the chrome ore pellets, and adopts the following scheme: the pellets internally provided with coke powder are pre-reduced at high temperature in a rotary kiln, then are directly added into a shaft kiln, hydrogen is introduced for cooling, and the cooled pellets are discharged and then are carried into a submerged arc furnace through a metal hopper for smelting.
Specifically, the method for reducing agglomeration of the pre-reduced chromium ore pellets comprises the following steps:
(1) And (3) performing fine grinding pretreatment on the mixture of the chromium ore powder and the coke powder, adding bentonite, and then sending to pelletization to obtain green pellets.
Wherein the chromium ore powder is obtained by a commercial method, wherein the Cr is 2 O 3 ＝38-50％，Cr/Fe＝1-2,SiO 2 ＝2-6％，MgO＝5-20％，Al 2 O 3 And (5) to 25 percent. The coke powder is obtained by a commercial route, and the fixed carbon content of the coke powder is 80-86%.
Preferably, after the mixture of the chromium ore powder and the coke powder is subjected to fine grinding pretreatment, the proportion of the mixture with the particle size of less than 0.044mm is more than 80 percent, and the water content of the mixture after filtration is 8.5 to 9 weight percent.
Preferably, the weight ratio of the chromium ore powder, the coke powder and the bentonite is 800-900:50-200:8-15.
Wherein, a disk pelletizer is adopted for pelletizing, the particle diameter of the green pellets is 8-16mm, and the water content of the green pellets is 10-11wt%.
(2) And the green pellets are preheated and roasted and then enter a rotary kiln for reduction roasting.
Wherein, the green pellets are preheated and roasted by adopting a chain grate, and preferably, the hot air temperature of the preheating section is 950-1150 ℃.
Preferably, the residence time of the pellets in the rotary kiln is 200-260 minutes, and the hot air temperature at the kiln head of the rotary kiln is 1000-1150 ℃.
Further preferably, the residence time of the pellets in the rotary kiln is 230 minutes, and the temperature of hot air at the kiln head of the rotary kiln is 1080 ℃.
(3) And directly feeding the pellets subjected to reduction roasting into a shaft kiln, and introducing hydrogen for cooling.
Preferably, the pellets internally provided with the coke powder are pre-reduced at high temperature in a rotary kiln, discharged from the kiln head of the rotary kiln, directly added into a shaft kiln at the temperature of 1100-1300 ℃, and cooled by introducing hydrogen gas with the addition of 90-150m 3 And the pellets are dehydrated by hydrogen discharged from the shaft kiln and then are introduced into the shaft kiln for recycling.
(4) And discharging the cooled pellets, and then smelting in a submerged arc furnace.
Preferably, the pellets are cooled by hydrogen gas introduced into the shaft kiln, the temperature is 600-800 ℃, and the pellets are discharged from the bottom of the ore tank through a spiral discharger and are directly carried into the ore furnace by a metal hopper for smelting.
In some preferred embodiments, the weight ratio of the chromium ore powder and the coke powder in the green pellets is 880:120, directly adding the pellets discharged from the kiln head of the rotary kiln and subjected to high-temperature pre-reduction of the rotary kiln into a shaft kiln, and introducing hydrogen for cooling, wherein the addition amount of the hydrogen is 105m 3 Pellets per ton.
In some preferred embodiments, the weight ratio of the chromium ore powder and the coke powder in the green pellets is 880:120, pre-reducing the kiln head of the rotary kiln at high temperatureDirectly adding the pellets into a shaft kiln, and introducing hydrogen for cooling, wherein the addition of the hydrogen is 115m 3 And (c) pellets per ton.
In some preferred embodiments, the weight ratio of the chromium ore powder and the coke powder in the green pellets is 880:120, directly adding the pellets discharged from the kiln head of the rotary kiln and subjected to high-temperature pre-reduction of the rotary kiln into a shaft kiln, and introducing hydrogen for cooling, wherein the addition of the hydrogen is 125m 3 And (c) pellets per ton.
In some preferred embodiments, the weight ratio of the chromium ore powder and the coke powder in the green pellets is 880:120, directly adding the pellets discharged from the kiln head of the rotary kiln and subjected to high-temperature pre-reduction in the rotary kiln into a shaft kiln, and introducing hydrogen for cooling, wherein the addition amount of the hydrogen is 145m 3 And (c) pellets per ton.
In some other preferred embodiments, the weight ratio of the chromium ore powder and the coke powder in the green pellets is 900:100, directly adding the pellets discharged from the kiln head of the rotary kiln and subjected to high-temperature pre-reduction in the rotary kiln into a shaft kiln, and introducing hydrogen for cooling, wherein the addition of the hydrogen is 145m 3 And (c) pellets per ton.
Through practice, the method for reducing agglomeration of the pre-reduced chromium ore pellets can reduce agglomeration of the pre-reduced chromium ore pellets without reducing the reduction rate of iron oxide in the chromium ore pellets.
Examples
The invention is further illustrated by the following examples, which are not intended to limit the invention thereto. Experimental procedures without specifying specific conditions in the following examples were carried out according to conventional methods and conditions. The starting materials used in the following examples are all conventionally commercially available.
Reference example
Firstly, a conventional production flow for producing chromium-containing molten iron by using a rotary kiln to pre-reduce iron ore pellets is provided.
The specific production steps are as follows:
(1) Raw material preparation
The chromium ore powder and the coke powder are mixed according to the following weight percentage:
880 parts of chromium ore powder,
120 parts of coke powder, namely 120 parts of coke powder,
wherein the chromium ore powder is purchased in the market, and the chromium ore powder is Cr 2 O 3 ＝42.2％，Cr/Fe＝1.4,SiO 2 ＝4.4％，MgO＝10.1％，Al 2 O 3 =14.5%. The coke powder is purchased from the market, and the fixed carbon content of the coke powder is 82.3 percent.
(2) Fine grinding pretreatment of mineral powder: and (3) finely grinding the mixture of the chromium ore powder and the coke powder, wherein the proportion of the mixture with the particle size of less than 0.044mm is 81.5%, and the water content of the mixture after filtration is 8.8%.
(3) Material preparation and pelletizing: adding bentonite into the raw materials, uniformly mixing, and adding into a disc pelletizer to obtain green pellets with the diameter of 8-16 mm. Wherein, the bentonite accounts for 11 parts, and the green ball water content is 10.6 percent.
(4) Preheating and roasting: and (3) distributing the green pellets on a chain grate machine for preheating roasting, wherein the hot air temperature of a preheating section is 1020 ℃.
(5) High-temperature reduction roasting: the pellets preheated and roasted on the chain grate machine are carried into a rotary kiln for reduction roasting, the residence time in the kiln is 230 minutes, and the temperature of hot air at the kiln head of the rotary kiln is 1080 ℃. The oxygen loss rate of the pellets after pre-reduction is 47.6 percent through detection.
(6) And (3) cooling: the pellets internally provided with coke powder are pre-reduced at high temperature in a rotary kiln, discharged from the kiln head of the rotary kiln, enter an ore tank at the pellet ore temperature of 1230 ℃, are cooled by blowing natural air with the air volume of 45m 3 Pellets per ton. The oxygen loss rate of the pre-reduced pellet after cooling is 36.5 percent through detection.
(7) Adding into an ore furnace for smelting: the temperature of the pellets is 780 ℃ after the pellets are cooled by the ore tank, and the pellets are discharged from the bottom of the ore tank through a spiral discharger and are carried into the ore furnace by a metal hopper for smelting.
According to detection, the cooled pellet ore has the lump mineral proportion of 20-50mm of 35% and the lump mineral proportion of 50-80mm of 23%, and the operation rate of the spiral discharging machine is 73% due to the fact that the pellet ore is large in lump degree and easy to block.
The reference example shows that after the pellets internally provided with the coke powder are pre-reduced at high temperature in the rotary kiln, if blast cooling is adopted, the pellets are easy to agglomerate, the operation rate of a spiral discharging machine at the bottom of an ore tank is influenced, the normal operation of production is influenced, and the oxygen loss rate of iron oxides in the pellets is reduced by 11 percent.
Example 1
In this example, pellets discharged from the kiln head of the rotary kiln and pre-reduced at high temperature in the rotary kiln were directly fed into a shaft kiln, and cooled by introducing hydrogen gas in an amount of 105m 3 Pellets per ton.
The specific steps are characterized as follows:
(1) Raw material preparation
The chromium ore powder and the coke powder are mixed according to the following weight percentage:
880 parts of chromium ore powder, namely 880 parts of chromium ore powder,
120 parts of coke powder, namely 120 parts of coke powder,
wherein the chromium ore powder is purchased in the market, and the Cr thereof is 2 O 3 ＝42.2％，Cr/Fe＝1.4,SiO 2 ＝4.4％，MgO＝10.1％，Al 2 O 3 =14.5%. The coke powder is purchased from the market, and the fixed carbon content of the coke powder is 82.3 percent.
(2) Fine grinding pretreatment of mineral powder: and (3) finely grinding the mixture of the chromium ore powder and the coke powder, wherein the proportion of the mixture with the diameter less than 0.044mm is 81.5%, and the water content of the mixture after filtration is 8.8%.
(3) Material preparation and pelletizing: adding bentonite into the raw materials, uniformly mixing, and adding into a disc pelletizer to obtain green pellets with the diameter of 8-16 mm. Wherein, the bentonite accounts for 11 parts, and the green ball water content is 10.6 percent.
(4) Preheating and roasting: and (3) distributing the green pellets on a chain grate machine for preheating roasting, wherein the hot air temperature of a preheating section is 1020 ℃.
(5) High-temperature reduction roasting: and (3) carrying the pellets subjected to preheating roasting on a chain grate machine into a rotary kiln for reduction roasting, wherein the retention time in the kiln is 230 minutes, and the temperature of hot air at the kiln head of the rotary kiln is 1080 ℃. The oxygen loss rate of the pellets after pre-reduction is 47.6 percent through detection.
(6) Cooling hydrogenated gas: the pellets internally provided with coke powder are pre-reduced at high temperature in a rotary kiln, discharged from the kiln head of the rotary kiln, directly added into a shaft kiln at the temperature of 1230 ℃, and cooled by introducing hydrogen gas with the addition amount of the hydrogen gasIs 1050m 3 And the pellets are dehydrated by hydrogen discharged from the shaft kiln and then are introduced into the shaft kiln for recycling. The detection shows that the oxygen loss rate of the cooled pre-reduced iron oxide pellets is 59.3 percent.
(7) Adding into an ore furnace for smelting: the temperature of the pellets is 650 ℃ after the pellets are cooled by introducing hydrogen into a shaft kiln, and the pellets are discharged from the bottom of a mine groove through a spiral discharger and are carried into a mine heating furnace by a metal hopper for smelting.
Through detection, the cooled pellet ore has the lump ore proportion of 20-50mm of 22% and the lump ore proportion of 50-80mm of 13%, and the operation rate of the spiral discharging machine is 89% due to small lump degree and difficulty in material blockage.
The above examples show that pellets internally provided with coke powder are pre-reduced at high temperature in a rotary kiln, then directly added into a shaft kiln, and cooled by introducing hydrogen, the lump ore proportion of 20-50mm and 50-80mm is reduced compared with that of the reference example, the operating rate of a spiral discharger at the bottom of an ore tank is improved, the operating rate is improved to 89% from 73% of the reference example, and the oxygen loss rate of iron oxides in the pellets is improved to 59.3% from 36.5% of the reference example, and is improved by 22.8% compared with the reference example.
Example 2
In this example, pellets discharged from the kiln head of the rotary kiln and subjected to high-temperature pre-reduction in the rotary kiln were directly added into a shaft kiln, and cooled by introducing hydrogen gas in an amount of 115m 3 Pellets per ton.
The specific steps are characterized as follows:
(1) Raw material preparation
The chromium ore powder and the coke powder are mixed according to the following weight percentage:
880 parts of chromium ore powder,
120 parts of coke powder, namely, 120 parts of coke powder,
wherein the chromium ore powder is purchased in the market, and the Cr thereof is 2 O 3 ＝42.2％，Cr/Fe＝1.4，SiO 2 ＝4.4％，MgO＝10.1％，Al 2 O 3 =14.5%. The coke powder is purchased from the market, and the fixed carbon content of the coke powder is 82.3 percent.
(2) Fine grinding pretreatment of mineral powder: and (3) finely grinding the mixture of the chromium ore powder and the coke powder, wherein the proportion of the mixture with the particle size of less than 0.044mm is 81.5%, and the water content of the mixture after filtration is 8.8%.
(3) Material preparation and pelletizing: adding bentonite into the raw materials, uniformly mixing, and adding a disc pelletizer to obtain green pellets with the diameter of 8-16 mm. Wherein, the bentonite accounts for 11 parts, and the green ball water content is 10.6 percent.
(4) Preheating and roasting: and (3) distributing the green pellets on a chain grate machine for preheating roasting, wherein the hot air temperature of a preheating section is 1020 ℃.
(5) High-temperature reduction roasting: and (3) carrying the pellets subjected to preheating roasting on a chain grate machine into a rotary kiln for reduction roasting, wherein the retention time in the kiln is 230 minutes, and the temperature of hot air at the kiln head of the rotary kiln is 1080 ℃. The detection shows that the oxygen loss rate of the pre-reduced pellet ore is 47.6 percent.
(6) Cooling hydrogenated gas: the pellets internally provided with coke powder are pre-reduced at high temperature in a rotary kiln, discharged from the kiln head of the rotary kiln, directly added into a shaft kiln at the temperature of 1230 ℃, and cooled by introducing hydrogen gas, wherein the addition amount of the hydrogen gas is 115m 3 And the pellets are dehydrated by hydrogen discharged from the shaft kiln and then are introduced into the shaft kiln for recycling. The detection shows that the oxygen loss rate of the cooled pre-reduced pellet iron oxide is 62.4%.
(7) Adding into an ore furnace for smelting: the temperature of the pellets is 650 ℃ after the pellets are cooled by introducing hydrogen into a shaft kiln, and the pellets are discharged from the bottom of a mine groove through a spiral discharger and are carried into a mine heating furnace by a metal hopper for smelting.
Through detection, the cooled pellet ore has the lump ore proportion of 20-50mm being 20% and the lump ore proportion of 50-80mm being 11%, and the operation rate of the spiral discharging machine is 92% due to small lump degree and difficulty in material blockage.
The above examples show that pellets internally provided with coke powder are pre-reduced at high temperature in a rotary kiln, then directly added into a shaft kiln, and cooled by increasing the flow of introduced hydrogen, the proportion of lump ore of 20-50mm and 50-80mm is reduced, the operating rate of a spiral discharger at the bottom of an ore tank is improved, the operating rate is improved to 92% from 89% of example 1, the oxygen loss rate of iron oxide in the pellets is improved to 62.4% from 59.3% of example 1, and the percentage is improved by 3.1% compared with example 1.
Example 3
In this example, pellets discharged from the kiln head of the rotary kiln and pre-reduced at high temperature in the rotary kiln were directly fed into a shaft kiln, and cooled by introducing hydrogen gas in an amount of 125m 3 Pellets per ton.
The specific steps are characterized as follows:
(1) Raw material preparation
The chromium ore powder and the coke powder are mixed according to the following weight percentage:
880 parts of chromium ore powder,
120 parts of coke powder, namely 120 parts of coke powder,
wherein the chromium ore powder is purchased in the market, and the Cr thereof is 2 O 3 ＝42.2％，Cr/Fe＝1.4，SiO 2 ＝4.4％，MgO＝10.1％，Al 2 O 3 =14.5%. The coke powder is purchased from the market, and the fixed carbon content of the coke powder is 82.3 percent.
(2) Fine grinding pretreatment of mineral powder: and (3) finely grinding the mixture of the chromium ore powder and the coke powder, wherein the proportion of the mixture with the diameter less than 0.044mm is 81.5%, and the water content of the mixture after filtration is 8.8%.
(3) Material preparation and pelletizing: adding bentonite into the raw materials, uniformly mixing, and adding a disc pelletizer to obtain green pellets with the diameter of 8-16 mm. Wherein, the bentonite is 11 parts, and the green ball water content is 10.6 percent.
(4) Preheating and roasting: and (3) distributing the green pellets on a chain grate machine for preheating roasting, wherein the hot air temperature of a preheating section is 1020 ℃.
(5) High-temperature reduction roasting: and (3) carrying the pellets subjected to preheating roasting on a chain grate machine into a rotary kiln for reduction roasting, wherein the retention time in the kiln is 230 minutes, and the temperature of hot air at the kiln head of the rotary kiln is 1080 ℃. The oxygen loss rate of the pellets after pre-reduction is 47.6 percent through detection.
(6) Cooling hydrogenated gas: the pellets internally provided with coke powder are pre-reduced at high temperature in a rotary kiln, discharged from the kiln head of the rotary kiln, directly added into a shaft kiln at the temperature of 1230 ℃, and cooled by introducing hydrogen gas, wherein the addition amount of the hydrogen gas is 125m 3 And the pellets are dehydrated by hydrogen discharged from the shaft kiln and then are introduced into the shaft kiln for recycling. The detection shows that the oxygen loss rate of the cooled pre-reduced pellet iron oxide is 64.7 percent.
(7) Adding into an ore furnace for smelting: the temperature of the pellets is 650 ℃ after the pellets are cooled by introducing hydrogen into a shaft kiln, and the pellets are discharged from the bottom of a mine groove through a spiral discharger and are carried into a submerged arc furnace by a metal hopper for smelting.
According to detection, the cooled pellet ore has a 20-50mm lump ore proportion of 19 percent and a 50-80mm lump ore proportion of 9.5 percent, and the operation rate of the spiral discharging machine is 93 percent due to the small lump degree and difficulty in material blockage.
The above examples show that pellets internally provided with coke powder are pre-reduced at high temperature in a rotary kiln, then directly added into a shaft kiln, and cooled by increasing the flow of introduced hydrogen, the proportion of lump ore of 20-50mm and 50-80mm is reduced, the operating rate of a spiral discharger at the bottom of an ore tank is improved, the operating rate is increased to 93% from 92% of example 2, and the iron oxide in the pellets is increased to 64.7% from 62.4% of example 2, which is 2.3% higher than that of example 2.
Example 4
In this example, pellets discharged from the kiln head of the rotary kiln and subjected to high-temperature pre-reduction in the rotary kiln were directly added into a shaft kiln, and cooled by introducing hydrogen gas in an amount of 145m 3 Pellets per ton.
The specific steps are characterized as follows:
(1) Raw material preparation
The chromium ore powder and the coke powder are mixed according to the following weight percentage:
880 parts of chromium ore powder, namely 880 parts of chromium ore powder,
120 parts of coke powder, namely 120 parts of coke powder,
wherein the chromium ore powder is purchased in the market, and the Cr thereof is 2 O 3 ＝42.2％，Cr/Fe＝1.4,SiO 2 ＝4.4％，MgO＝10.1％，Al 2 O 3 =14.5%. The coke powder is purchased from the market, and the fixed carbon content of the coke powder is 82.3 percent.
(2) Fine grinding pretreatment of mineral powder: and (3) finely grinding the mixture of the chromium ore powder and the coke powder, wherein the proportion of the mixture with the particle size of less than 0.044mm is 81.5%, and the water content of the mixture after filtration is 8.8%.
(3) Material preparation and pelletizing: adding bentonite into the raw materials, uniformly mixing, and adding into a disc pelletizer to obtain green pellets with the diameter of 8-16 mm. Wherein, the bentonite accounts for 11 parts, and the green ball water content is 10.6 percent.
(4) Preheating and roasting: and (3) distributing the green pellets on a chain grate machine for preheating roasting, wherein the hot air temperature of a preheating section is 1020 ℃.
(5) High-temperature reduction roasting: the pellets preheated and roasted on the chain grate machine are carried into a rotary kiln for reduction roasting, the residence time in the kiln is 230 minutes, and the temperature of hot air at the kiln head of the rotary kiln is 1080 ℃. The oxygen loss rate of the pellets after pre-reduction is 47.6 percent through detection.
(6) Cooling hydrogenated gas: the pellets internally provided with coke powder are pre-reduced at high temperature in a rotary kiln, discharged from the kiln head of the rotary kiln, directly added into a shaft kiln at the temperature of 1230 ℃, and cooled by introducing hydrogen gas, wherein the addition amount of the hydrogen gas is 125m 3 And the pellets are dehydrated by hydrogen discharged from the shaft kiln and then are introduced into the shaft kiln for recycling. The detection shows that the oxygen loss rate of the cooled pre-reduced pellet iron oxide is 65.1 percent.
(7) Adding into an ore furnace for smelting: the temperature of the pellets is 650 ℃ after the pellets are cooled by introducing hydrogen into a shaft kiln, and the pellets are discharged from the bottom of a mine groove through a spiral discharger and are carried into a mine heating furnace by a metal hopper for smelting.
Through detection, the cooled pellet ore has the lump ore proportion of 20-50mm of 18.2 percent and the lump ore proportion of 50-80mm of 9.2 percent, and the operation rate of the spiral discharging machine is 93.6 percent because the lump degree is small and the material is not easy to block.
The above examples show that pellets internally provided with coke powder are pre-reduced at high temperature in a rotary kiln, and then directly added into a shaft kiln, and the flow of introduced hydrogen is increased for cooling, the proportion of lump ore with the size of 20-50mm and 50-80mm is reduced, the operating rate of a spiral discharger at the bottom of an ore tank is slightly improved, from 93% of example 3 to 93.6%, and the oxygen loss rate of iron oxide in the pellets is improved from 64.7% of example 3 to 65.1%, and is improved by 0.4% compared with example 3.
Example 5
The implementation reduces the proportion of the coke powder in the kiln, and simultaneously, pellets discharged from the kiln head of the rotary kiln and subjected to high-temperature pre-reduction of the rotary kiln are directly added into the shaft kiln and are communicated with the shaft kilnCooling with hydrogen gas at a hydrogen addition of 145m 3 Pellets per ton.
The specific steps are characterized as follows:
(1) Raw material preparation
The chromium ore powder and the coke powder are mixed according to the following weight percentage:
900 parts of chromium ore powder,
100 parts of coke powder, namely 100 parts of coke powder,
wherein the chromium ore powder is purchased in the market, and the Cr thereof is 2 O 3 ＝42.2％，Cr/Fe＝1.4，SiO 2 ＝4.4％，MgO＝10.1％，Al 2 O 3 =14.5%. The coke powder is purchased from the market, and the fixed carbon content of the coke powder is 82.3 percent.
(2) Fine grinding pretreatment of mineral powder: and (3) finely grinding the mixture of the chromium ore powder and the coke powder, wherein the proportion of the mixture with the diameter less than 0.044mm is 81.5%, and the water content of the mixture after filtration is 8.8%.
(3) Material preparation and pelletizing: adding bentonite into the raw materials, uniformly mixing, and adding a disc pelletizer to obtain green pellets with the diameter of 8-16 mm. Wherein, the bentonite accounts for 11 parts, and the green ball water content is 10.6 percent.
(4) Preheating and roasting: and (3) distributing the green pellets on a chain grate machine for preheating roasting, wherein the hot air temperature of a preheating section is 1020 ℃.
(5) High-temperature reduction roasting: and (3) carrying the pellets subjected to preheating roasting on a chain grate machine into a rotary kiln for reduction roasting, wherein the retention time in the kiln is 230 minutes, and the temperature of hot air at the kiln head of the rotary kiln is 1080 ℃. The oxygen loss rate of the pellets after pre-reduction is 41.3 percent through detection.
(6) Cooling hydrogenated gas: the pellets internally provided with coke powder are pre-reduced at high temperature in a rotary kiln, discharged from the kiln head of the rotary kiln, directly added into a shaft kiln at the temperature of 1230 ℃, and cooled by introducing hydrogen gas, wherein the addition amount of the hydrogen gas is 125m 3 And the pellets are dehydrated by hydrogen discharged from the shaft kiln and then are introduced into the shaft kiln for recycling. The oxygen loss rate of the cooled pre-reduced pellet iron oxide is 56.9 percent through detection.
(7) Adding into an ore furnace for smelting: the temperature of the pellets is 650 ℃ after the pellets are cooled by introducing hydrogen into a shaft kiln, and the pellets are discharged from the bottom of a mine groove through a spiral discharger and are carried into a submerged arc furnace by a metal hopper for smelting.
According to detection, the cooled pellet ore has a lump mineral proportion of 16.3% to 50mm and 5.4% to 50-80mm, and has a small lump degree, so that material blockage is not easy to occur, and the operation rate of the spiral discharging machine is 95.1%.
The above examples show that the proportion of the internally-added coke powder is reduced, and meanwhile, pellets of the internally-added coke powder are directly added into the shaft kiln after being pre-reduced at high temperature by the rotary kiln, the proportion of lump minerals of 20-50mm and 50-80mm can be further reduced, the operating rate of the spiral discharger at the bottom of the ore tank is improved to 95.1% from 73% of the reference example, and the oxygen loss rate of iron oxides in the pellets is improved to 56.9% from 36.5% of the reference example, and is improved by 20.4 percentage points.
The present invention has been disclosed in the foregoing in terms of preferred embodiments, but it will be understood by those skilled in the art that these embodiments are merely illustrative of the present invention and should not be construed as limiting the scope of the invention. It should be noted that all changes and substitutions that are equivalent to these embodiments are deemed to be within the scope of the claims of the present invention. Therefore, the protection scope of the present invention should be subject to the scope defined in the claims.
Claims (10)
1. A method for reducing agglomeration of pre-reduced chrome ore pellets, comprising:
(1) Performing fine grinding pretreatment on a mixture of chromium ore powder and coke powder, adding bentonite, and then sending to pelletization to obtain green pellets;
(2) Preheating and roasting the green pellets, and then, feeding the green pellets into a rotary kiln for reduction roasting;
(3) Directly feeding the pellets subjected to reduction roasting into a shaft kiln, and introducing hydrogen for cooling;
(4) And discharging the cooled pellets, and then smelting in a submerged arc furnace.
2. The method for reducing agglomeration of pellets of pre-reduced chromium ore as claimed in claim 1, wherein the green pellets have a water content of 10-11wt%, wherein the weight ratio of chromium ore powder, coke powder and bentonite is 800-900:50-200:8-15.
3. The method for reducing agglomeration of pellets of pre-reduced chromium ore as claimed in claim 1, wherein the temperature of hot air at the kiln head of the rotary kiln is 1000-1150 ℃ and the retention time of the green pellets in the kiln is 200-260 min.
4. The method for reducing agglomeration of pellets in pre-reduced chrome ore as claimed in claim 1, wherein the temperature of hot blast at the kiln head of the rotary kiln is 1080 ℃ and the retention time of the green pellets in the kiln is 230 minutes.
5. The method of claim 4, wherein the pellet temperature is 1100-1300 ℃ when entering the shaft kiln.
6. The method for reducing agglomeration of pellets of pre-reduced chromium ore as claimed in claim 1, wherein the amount of hydrogen added is 90-150m 3 Pellets per ton.
7. The method for reducing agglomeration of pellets of pre-reduced chromium ore as claimed in claim 1, wherein the temperature of the cooled pellets is 600-800 ℃.
8. The method for reducing agglomeration of pre-reduced chromium ore pellets as claimed in claim 1, wherein the weight ratio of the chromium ore fines to the coke powder is 880:120, the adding amount of the hydrogen is 105m 3 Pellets/t, 115m 3 Pellet/t, 125m 3 Pellets/t or 145m 3 Pellets per ton.
9. The method for reducing agglomeration of pellets of pre-reduced chromium ore as claimed in claim 1, wherein the weight ratio of the chromium ore fines to the coke fines is 900:100, the adding amount of the hydrogen is 145m 3 And (c) pellets per ton.
10. The method for reducing agglomeration of pellets of pre-reduced chromium ore as claimed in claim 1, wherein the chromium ore fines are Cr in weight percentage 2 O 3 ＝38-50％，Cr/Fe＝1-2，SiO 2 ＝2-6％，MgO＝5-20％，Al 2 O 3 ＝5-25％。
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