A method for baking lump ore using pellet afterheat

Abstract

The application discloses a method for baking lump ore by using pellet residual heat, and specifically comprises the following steps: firstly, laying a layer of lump ore on a pellet forming belt after a pellet shaft furnace cooling device; secondly, uniformly laying the hot pellet ore cooled by the pellet shaft furnace cooling device on the lump ore on the pellet forming belt; thirdly, turning the hot pellet ore and the lump ore through a funnel of a first transfer station; fourthly, uniformly mixing the lump ore and the hot pellet ore and falling the mixture on a second pellet forming belt; fifthly, falling the mixture of the lump ore and the hot pellet ore on a discharge trolley of the second pellet forming belt into a finished product bin; and finally, fully contacting the lump ore and the hot pellet ore in the finished product bin, and mixing the lump ore and the hot pellet ore to reach a temperature of 80-100 DEG C. The application directly transfers the residual heat of the cooled pellet to the lump ore laid on the bottom of the pellet, reduces the moisture in the lump ore, increases the use proportion of the blast furnace lump ore, and reduces the production cost of the blast furnace iron making.

Description

Technical Field

[0001] This invention relates to the field of pellet waste heat utilization technology, and in particular to a method for baking lump ore using pellet waste heat. Background Technology

[0002] Currently, the iron ore used in domestic blast furnace smelting generally consists of sintered ore, pellets, lump ore, and coke. Due to market competition and resource deterioration, increasing the proportion of lump ore in blast furnace production to replace artificial rich ore, especially high-priced pellets, can reduce ironmaking costs. Simultaneously, increasing the proportion of lump ore used in blast furnace ironmaking can reduce the proportion of other raw materials, reduce processing steps for other raw materials, thereby improving resource utilization and reducing pollutant emissions. Since lump ore is directly used after being mined, crushed, and transported to the user unit without secondary processing, it can reduce the cost of iron ore for blast furnaces. The moisture content of lump ore is 3%-5%, and the fines content is 20%-30%. Due to open-air storage, the moisture content will increase further during the rainy season. When using lump ore, due to its high powder and moisture content, dust and clay adhere to the surface of the lump ore and are not easy to separate. Directly entering the blast furnace will affect the permeability of the blast furnace and will not be able to increase the proportion of lump ore added. The blast furnace can only add about 8% lump ore at most, which will also increase the fuel ratio of the blast furnace and is not conducive to optimizing the cost of ironmaking.

[0003] Currently, the main methods for processing lump ore in blast furnaces are as follows: 1. Screening the lump ore to separate small particles and dust before directly feeding it into the blast furnace. However, due to the high powder and moisture content, dust and clay adhere to the surface of the lump ore, making it difficult to separate and affecting the blast furnace's permeability. 2. Washing or soaking the lump ore with water washing equipment. This requires a large space and a large amount of water, and also necessitates wastewater and sludge treatment, wasting resources. 3. Drying the lump ore using drying equipment. This requires the construction of a complete and complex set of equipment for drying, screening, and dust removal, requiring a large space and significant investment, and consuming a large amount of energy.

[0004] With the increasing demand for high-quality raw materials in ironmaking, the proportion of pellets used is constantly increasing. This increase in pellet usage leads to a greater workload in the pelletizing process. Vertical shaft furnace pelletizing, currently a relatively mature technology for pellet production in China, produces pellets with relatively stable quality. Produced pellets require cooling, which generally takes the form of natural cooling, water cooling, vertical shaft furnace cooling, and belt coolers. Using vertical shaft furnace cooling as primary cooling and external belt coolers as secondary cooling, pellets can be cooled from 1000℃ to 200℃, which is sufficient for production needs. However, even at 200℃ after cooling, the pellets still retain residual heat, usually in the form of sensible heat. Due to the large sensible heat release area, centralized recovery is impossible, resulting in poor recovery efficiency and waste.

[0005] Lump ore, as a raw material for blast furnace ironmaking, is widely accepted in ironmaking production due to its abundant reserves and low price, and can be used directly as feedstock. However, lump ore is, after all, a raw material, and its metallurgical properties limit its usage. In particular, its moisture content is crucial; lump ore with high moisture content increases the endothermic reaction of water evaporation, reducing the heat consumed in the reduction of iron-containing raw materials within the blast furnace. Therefore, the proportion of lump ore fed into the furnace is limited, generally not exceeding 10%. Many companies have attempted to adopt various methods to reduce the moisture content of the lump ore fed into the furnace, but these methods are often limited by technological constraints and cost-effectiveness. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a method for baking lump ore using the waste heat of pellets. This method directly transfers the waste heat after the pellets are cooled to the lump ore spread at the bottom of the pellets, thereby reducing the moisture content of the lump ore, increasing the proportion of lump ore used in the blast furnace, and reducing the production cost of blast furnace ironmaking.

[0007] This invention is implemented as follows: a method for baking lump ore using waste heat from pelletizing, as detailed below:

[0008] First, a layer of lump ore is laid on the pelletizing conveyor belt after the cooling equipment of the pelletizing vertical furnace. Then, the hot pellets cooled by the cooling equipment of the pelletizing vertical furnace are evenly spread on the lump ore on the pelletizing conveyor belt. The hot pellets and lump ore are turned over by the hopper of the transfer station. Then, the lump ore and hot pellets are evenly mixed and fall onto the pelletizing conveyor belt. The mixture of lump ore and hot pellets is dropped into the finished product bin by the unloading trolley of the pelletizing conveyor belt, so that the lump ore and hot pellets are fully in contact in the finished product bin. After mixing, the material temperature reaches 80-100℃.

[0009] Preferably, the thickness of the ore block laid on the pellet belt is 45-55 mm.

[0010] Preferably, the hot pellets are cooled to 200°C using a pelletizing vertical furnace cooling device.

[0011] Preferably, the amount of lump ore is 95-105 t / h, and the amount of hot pellet ore is 150-170 t / h.

[0012] Preferably, the hot pellets are evenly spread onto the block ore that has been pelletized into a belt using a scraper.

[0013] Preferably, the lump ore is transported from the enclosed material yard to the pelletizing process on a conveyor belt after passing through the pelletizing vertical furnace cooling equipment.

[0014] Preferably, the pellets are formed into a heat-resistant belt.

[0015] The present invention has the following advantages and beneficial effects:

[0016] 1. This invention mixes hot pellets and lump ore on a conveyor belt, making full use of the residual heat after the hot pellets have cooled, and directly transferring the heat to the lump ore laid at the bottom of the hot pellets. This significantly reduces the moisture content of the lump ore, increases the proportion of lump ore used in the blast furnace, and reduces the production cost of blast furnace ironmaking.

[0017] 2. By first laying a layer of lump ore on the conveyor belt during pelletizing, the present invention effectively protects the belt from being scalded by the hot pellets, increasing the belt life from 3 months to over 6 months. Furthermore, it eliminates the need for complete cooling of the pellets, raising the pellet temperature from the traditional 120℃ to 200℃, reducing the number of blowers required and lowering power consumption. The proportion of lump ore used in the blast furnace also increases from 8% to approximately 15%, effectively reducing production costs.

[0018] 3. This invention utilizes the waste heat from cooling the finished pellets in a vertical shaft furnace. Based on a normal 5% moisture content for incoming lump ore, the moisture content can be reduced to 0%. Simultaneously, the low temperature of the lump ore itself rapidly lowers the temperature of the cooled pellets. Assuming the hot pellets exit the vertical shaft furnace at 200℃, the temperature drops rapidly to below 100℃ after the lump ore is laid underneath, while the lump ore temperature rises to around 80℃. Based on a 5% reduction in lump ore moisture, the proportion of lump ore entering the furnace increases by 7% compared to traditional methods. Considering an average price difference of 200 yuan between pellets and lump ore, this can reduce the cost per ton of iron by 140 yuan. Because the waste heat from the cooled pellets is absorbed by the lump ore and not directly released into the air, the greenhouse effect caused by excessive heat loss is reduced. Attached Figure Description

[0019] Figure 1 This is a flowchart of a method for baking lump ore using waste heat from pelletizing, provided by an embodiment of the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0021] The finished pellets from the vertical shaft furnace are cooled using vertical shaft furnace cooling technology as the primary cooling method and an external belt cooler as the secondary cooling method. This can cool the pellets from 1000℃ to 200℃, which is sufficient to meet production needs. However, there is still residual heat at 200℃, which is usually wasted as sensible heat.

[0022] Currently, our company mainly uses Newman lumps and SP10 lumps. There are no specific requirements for the usage ratio; it is determined based on incoming materials and inventory levels. Generally, the proportion of Newman lumps is 9%, and the proportion of SP10 lumps is 6%. The main component data are shown in Table 1 below:

[0023] Table 1. Main components of Newman blocks and SP10 blocks

[0024] TFe <![CDATA[SiO2]]> <![CDATA[Al2O3]]> P S Powder ratio Moisture Newman block 62.24 3.62 1.53 0.068 0.026 30％ 4.69％ sp10 61.03 4.33 2.11 0.091 0.022 20％ 4.82％

[0025] To fully utilize the waste heat after pellet cooling, this waste heat can be used to dry the moisture in the ore lump fed into the blast furnace, thereby increasing the proportion of ore lump used in the blast furnace. This is an effective method for utilizing pellet cooling waste heat and reducing blast furnace ironmaking costs. Therefore, this invention proposes a method for baking ore lump using pellet waste heat, as follows:

[0026] Lump ore is conveyed from the enclosed stockyard to the pelletizing belt after the belt cooler of the pelletizing vertical furnace via a belt conveyor. First, a layer of lump ore with a thickness of about 50mm is laid on the pelletizing belt, with a quantity of about 100t / h. Then, 160t / h of hot pellets at 200℃, cooled by the belt cooler of the pelletizing vertical furnace, are evenly spread onto the lump ore on the pelletizing belt via a scraper conveyor. The hot pellets and lump ore are turned over by the hopper of the transfer station and then evenly mixed and fall onto the pelletizing belt. The mixture of lump ore and hot pellets is then discharged into the finished product bin by the unloading trolley of the pelletizing belt.

[0027] The pellets are formed into a belt that is heat-resistant.

[0028] In the finished product warehouse, the lump ore and hot pellet ore are in full contact. The heat of the hot pellet ore is transferred to the surface of the lump ore, causing the moisture on the surface of the lump ore to evaporate. After mixing, the temperature of the material reaches about 80°C, and the moisture content of the lump ore is reduced from about 5% to 0. The dust adhering to the surface of the lump ore is separated from the lump ore and sucked away by the dust collector, which can effectively improve the air permeability of the material entering the blast furnace.

[0029] The equipment required for this invention is relatively simple, requiring no complex equipment. It only necessitates that the conveyor belts for lump ore and hot pellet ore be transferred at the transfer station via a funnel. The residual heat from the cooling of the hot pellet ore is directly transferred to the lump ore that has been dried and spread on top of the pellets.

[0030] The present invention will now be described in further detail.

[0031] Please see Figure 1 The method for baking lump ore using waste heat from pelletizing provided in this embodiment is as follows:

[0032] 1. After the batching, drying, and grinding processes are completed, the raw materials are sent to the silo in the pelletizing workshop and then fed into the disc pelletizer via a disc feeder. The green pellets coming out of the disc pelletizer enter the roller screen to remove unqualified green pellets smaller than 6mm and larger than 20mm. After that, they are sent to the mixing hopper in the pelletizing chamber by a belt conveyor for re-pelleting.

[0033] 2. Qualified green pellets (6mm to 20mm) from the screening workshop are loaded into the vertical shaft furnace body for the next process via the top feeding equipment. The pellets descend continuously at a uniform speed of 40-50mm / min. Hot gas from the combustion chamber enters the furnace through the nozzle, and the exhaust gas temperature (1100-1150℃) and flow velocity (3.0m / s, from bottom to top) exchange heat with the green pellets (from top to bottom). The green pellets first undergo drying, dehydration, and preheating oxidation in the vertical shaft furnace; then they enter the roasting zone for high-temperature consolidation reaction; after passing through the soaking zone, the entire consolidation process is completed; the roasted oxidized pellets are cooled in the cooling zone at the bottom of the furnace.

[0034] 3. After processing in the vertical shaft furnace, the pellets reach a temperature above 1000℃ as they pass through the roasting and soaking zones and then into the cooling zone. Even after initial cooling within the furnace, the pellets discharged from the furnace still maintain a temperature of 600-800℃. These incandescent pellets then enter a belt cooler, where external air cooling reduces their temperature to below 200℃. Belt cooling ensures continuous production, uniform material distribution, prevents shoveling and ditching, and maintains a consistent flow rate, resulting in effective cooling.

[0035] 4. After exiting the belt cooler, the pellets are mixed with lump ore from the feed plant via the first pelletizing belt. The hot pellets and lump ore are tumbled through a hopper at a transfer station, and then the lump ore and hot pellets are evenly mixed and fall onto the second pelletizing belt. The mixture of lump ore and hot pellets is then discharged into the finished product bin via the unloading trolley of the second pelletizing belt. After being cooled by the pellets at 200°C, the moisture carried by the lump ore is dried, and then the pellets are fed into the blast furnace. If there is a surplus of pellets, they are directly fed into the finished product bin via the first pelletizing belt.

[0036] This invention mixes hot pellets and lump ore on a conveyor belt, fully utilizing the residual heat from the cooling of the hot pellets. This heat is directly transferred to the lump ore layered at the bottom of the hot pellets, significantly reducing the moisture content of the lump ore. This increases the proportion of lump ore used in the blast furnace, lowering production costs. Laying a layer of lump ore on the conveyor belt before pelletizing effectively protects the belt from being scalded by the hot pellets, extending its lifespan from 3 months to over 6 months. Furthermore, it eliminates the need for complete cooling of the pellets, increasing the pellet temperature from the traditional 120℃ to 200℃, reducing the number of blowers required and lowering power consumption. The proportion of lump ore used in the blast furnace also increases from 8% to approximately 15%, effectively reducing production costs.

[0037] This invention utilizes the waste heat from cooling the finished pellets in a vertical shaft furnace. Based on a normal 5% moisture content for incoming lump ore, the moisture content can be reduced to 0%. Simultaneously, the low temperature of the lump ore itself rapidly lowers the temperature of the cooled pellets. Assuming the hot pellets exit the vertical shaft furnace at 200°C, the temperature drops rapidly to below 100°C after the lump ore is laid underneath, while the lump ore temperature rises to around 80°C. Based on a 5% reduction in lump ore moisture, the proportion of lump ore entering the furnace increases by 7% compared to traditional methods. Considering an average price difference of 200 yuan between pellets and lump ore, this can reduce the cost per ton of iron by 140 yuan. Because the waste heat from the cooled pellets is absorbed by the lump ore and not directly released into the air, the greenhouse effect caused by excessive heat loss is reduced.

[0038] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended 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 or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for baking lump ore using waste heat from pelletizing, characterized in that, Specifically as follows: First, a layer of lump ore is laid on the pelletizing conveyor belt after the cooling equipment of the pelletizing vertical furnace. Then, the hot pellets cooled by the cooling equipment of the pelletizing vertical furnace are evenly spread on the lump ore on the pelletizing conveyor belt. The hot pellets and lump ore are turned over by the hopper of the transfer station. Then, the lump ore and hot pellets are evenly mixed and fall onto the pelletizing conveyor belt. The mixture of lump ore and hot pellets is dropped into the finished product bin by the unloading trolley of the pelletizing conveyor belt, so that the lump ore and hot pellets are fully in contact in the finished product bin. After mixing, the material temperature reaches 80-100℃.

2. The method for baking lump ore using waste heat from pelletizing according to claim 1, characterized in that, The thickness of the ore blocks laid on the belt formed by the pellets is 45-55 mm.

3. The method for baking lump ore using waste heat from pelletizing according to claim 1, characterized in that, The hot pellets are cooled to 200°C using a pelletizing vertical furnace cooling system.

4. The method for baking lump ore using waste heat from pelletizing according to claim 1, characterized in that, The amount of lump ore is 95-105 t / h, and the amount of hot pellet ore is 150-170 t / h.

5. The method for baking lump ore using waste heat from pelletizing according to claim 1, characterized in that, The hot pellets are evenly spread onto the block ore that has been pelletized into a belt using a scraper conveyor.

6. The method for baking lump ore using waste heat from pelletizing according to claim 1, characterized in that, The lump ore is transported from the closed material yard to the pelletizing cooling equipment of the pelletizing vertical furnace via a belt conveyor and then onto a belt conveyor.

7. The method for baking lump ore using waste heat from pelletizing according to claim 1, characterized in that, The pellets are formed into a heat-resistant belt.

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