Sensible heat recovery system for high-temperature steel slag

Abstract

The utility model discloses a sensible heat recovery system of high-temperature steel slag, which relates to the technical field of sensible heat recovery of high-temperature slag, and comprises a sensible heat high-temperature collector and a sensible heat low-temperature collector which are arranged up and down, and a gate is arranged between the sensible heat high-temperature collector and the sensible heat low-temperature collector; a feeding hole is formed in the side surface of the sensible heat high-temperature collector; a granulating fan capable of spraying high-pressure airflow is mounted at the feeding hole; the sensible heat recovery system further comprises an air supply system used for providing cooling air for the sensible heat low-temperature collector and a heat recovery unit capable of recovering heat in the sensible heat high-temperature collector and the sensible heat low-temperature collector. The device is simple in process and device, low in investment, low in energy consumption, few in operating parts, high in productivity, high in sensible heat recovery efficiency and good in environmental protection effect, and has good economic benefits and social benefits.

Description

Technical Field

[0001] The utility model relates to the technical field of sensible heat recovery of high-temperature slag, in particular to a sensible heat recovery system of high-temperature steel slag. Background Art

[0002] The steel industry is a huge heavy industry sector and the material basis for the development of the national economy and national defense construction. At the same time, the steel industry is also a resource-intensive, energy-intensive, and emission-intensive industry. It uses iron ore as raw material, supplemented by coal, water, oxygen, etc., and uses energy inputs such as electricity and heat to produce a series of products such as steel, iron products, and by-products. my country's crude steel output has accounted for half of the world's total for more than 20 years, and China's crude steel output has increased by nearly 25% cumulatively. Data show that in 2019, my country's carbon dioxide emissions reached 9.826 billion tons, accounting for 28.76% of the global proportion, making it the world's largest carbon-emitting economy. Among them, carbon emissions from the steel industry account for 18% of the country's carbon emissions, making it the industry with the highest carbon emissions in the entire production activity except power generation.

[0003] On September 22, 2020, at the United Nations Climate Conference, President Xi Jinping pledged for the first time that "my country will strive to peak its carbon dioxide emissions before 2030, and strive to achieve carbon neutrality before 2060". Under the goal of "carbon peak and carbon neutrality", carbon reduction in the steel industry is a top priority. On January 20, 2021, China Baowu Steel Group Co., Ltd. announced its "carbon peak and carbon neutrality" timetable - "strive to peak carbon dioxide emissions in 2023, have the technological capabilities to reduce carbon emissions by 30% in 2025, strive to reduce carbon emissions by 30% in 2035, and achieve 'carbon neutrality' in 2050."

[0004] At present, there has been no revolutionary breakthrough in the smelting technology and energy structure of my country's steel industry. An important way to promote the carbon reduction goals of the steel industry is to promote the recycling of secondary resources. The secondary resources of steel enterprises mainly include solid waste, wastewater, and waste gas, commonly known as "three wastes". So far, the indicators such as the amount of new water used, the amount of discharged wastewater, and the reuse rate of production water in the production of my country's steel enterprises have been significantly improved, and the reuse rate of steel plant wastewater is as high as 99%. The emission indicators of major pollutants in waste gas have been significantly improved, and the industrial dust, COD emissions, SO 2 and NO x The concentration meets the national standard. However, there has been no major breakthrough in the resource utilization rate of steel solid waste, especially steel slag. In recent years, the resource utilization rate of steel slag has been below 30%. If the resource utilization of steel slag can be greatly improved, it will surely make a great contribution to the realization of the "dual carbon" goal.

[0005] Steel slag is a slag with silicates, ferrites and oxides as the main components (GB / T51387-2019) discharged from the smelting process of converters, electric furnaces and refining furnaces, which is formed by impurities in metal raw materials, flux and furnace lining. It mainly includes converter slag, electric furnace slag, casting slag, open-hearth slag, etc. For every ton of crude steel produced, 100 to 150 kg of steel slag is produced. In recent years, the annual production of steel slag in my country has basically maintained or exceeded 100 million tons. In addition, its resource utilization rate has not been high, resulting in about 70 million tons of steel slag being dumped every year. This not only occupies a large amount of land, but also causes pollution to soil, air and water.

[0006] The tapping temperature of steel slag is as high as 1400-1600℃, which contains a large amount of heat energy. The specific heat capacity of molten steel slag is about 1.2kJ / (kg·℃). If the temperature of the molten slag before and after heat recovery is 1400℃ and 500℃ respectively, 1.2GJ of sensible heat can be recovered per ton of steel slag, which is approximately equivalent to the heat generated by the complete combustion of 41kg of standard coal. If the sensible heat of steel slag produced by steel mills across the country is recycled, China can save at least 4.9 million tons of standard coal every year. Even if the waste heat recovery rate is 50%, the energy saving of recycling sensible heat of steel slag nationwide can reach nearly 2.5 million tons of standard coal. In addition, if the heat energy generated by steel slag is recovered at 60%, the recovered heat energy is converted into electrical energy, and 1GJ of heat energy can be converted into 277kW·h of electrical energy. The price of electrical energy is 0.53 yuan / kW·h, and the annual energy saving benefit is about 12.7 billion yuan. Steel slag is mainly composed of Ca, Si, Fe, Mn, Al, Mg, P, O, etc. Its mineral phases mainly include dicalcium silicate (C2S), tricalcium silicate (C3S), RO (R represents the solid solution formed by the oxides of magnesium, iron and manganese), dicalcium ferrite (C2F), free calcium oxide (f-CaO), metallic iron (MFe), etc. Since steel slag contains metallic iron, it can be used as a material for iron resource recycling; since it contains mineral phases such as C3S, C2S and ferroaluminate, steel slag has certain gelling activity and has the use value of gelling materials.

[0007] The different chemical compositions of steel slag result in different properties of steel slag. Steel slag with lower basicity is gray, while steel slag with higher basicity is brown-gray or off-white. Steel slag is loose and not easy to bond, and has a hard and dense texture. The density of steel slag is 3.0-3.5g / cm3. It is difficult to grind due to the iron content, and the grindability index is 0.7 (standard sand is 1). Steel slag has good compressive resistance, and the crushing value is 20%-32%.

[0008] To sum up, if the recycling of steel slag waste heat, iron resources and tailings can be achieved, it will be an important means for steel enterprises to achieve energy conservation and emission reduction, increase efficiency and reduce carbon emissions, and will also help achieve the "dual carbon" goals.

[0009] At present, the mainstream technology route for recycling waste heat, iron resources and tailings of steel slag is: roller crushing + pressure heat stuffing technology of steel slag. However, this technology has the disadvantages of too large equipment, huge workload of equipment maintenance, low operation rate, large investment, low sensible heat recovery rate, etc. At the same time, the steel slag of this method is slow to cool, resulting in a decrease in the content of glass formed inside the steel slag, and the activity of the steel slag is very low. Utility Model Content

[0010] The utility model aims to overcome the deficiencies of the prior art and provide a sensible heat recovery system for high-temperature steel slag, which can recover the sensible heat of the steel slag to the maximum extent.

[0011] In order to achieve the above purpose, the technical solution adopted by the utility model is as follows:

[0012] A sensible heat recovery system for high-temperature steel slag, comprising a sensible heat high-temperature collector and a sensible heat low-temperature collector arranged up and down, a gate being arranged between the sensible heat high-temperature collector and the sensible heat low-temperature collector; a feed port is arranged on the side of the sensible heat high-temperature collector, and a granulating fan capable of spraying high-pressure airflow is installed at the feed port;

[0013] The sensible heat recovery system also includes an air supply system for providing cooling air to the sensible heat low-temperature collector, and a heat recovery unit capable of recovering heat from the sensible heat high-temperature collector and the sensible heat low-temperature collector.

[0014] Furthermore, the air supply system includes an air duct connected to the interior of the sensible heat low-temperature collector, an air chamber connected to the air duct, and a cooling fan connected to the air chamber; in addition, a water mist nozzle is provided on the air outlet duct of the cooling fan.

[0015] Furthermore, an air outlet is provided at the upper end of the sensible heat high temperature collector, and an exhaust port is provided at the upper end of the sensible heat low temperature collector; the heat recovery unit is a boiler drum, and the air outlet and the exhaust port are both connected to the boiler drum.

[0016] Furthermore, a superheater capable of performing heat exchange on the gas inside the sensible heat high-temperature collector is installed inside the sensible heat high-temperature collector.

[0017] Furthermore, a discharge unit is provided at the lower end of the sensible heat low-temperature collector.

[0018] Furthermore, the unloading unit includes a unloading hopper and a vibrating feeder installed below the unloading hopper; a magnetic separation belt conveyor is installed below the vibrating feeder, and an iron magnet is provided on the magnetic separation belt conveyor.

[0019] Furthermore, the discharge hopper is provided in plurality, and the vibrating feeder is also provided in plurality accordingly.

[0020] Furthermore, the output end of the drum is connected to a cooling fan.

[0021] Furthermore, the output end of the drum is connected to an external bag dust collector.

[0022] Compared with the prior art, the utility model has the following beneficial effects:

[0023] (1) The system provided by the utility model is a fully enclosed environment, which can maximize the recovery of sensible heat of slag. According to tests, the sensible heat recovery rate is increased by more than 30% compared with the prior art.

[0024] (2) In the utility model, a granulating fan is provided to crush the liquid slag. The gas source of the granulating fan is a high-pressure inert gas. After the sensible heat in the system is recovered, the inert gas is also recovered to realize the recycling of the inert gas source. The advantages are low gas cost (it is a by-product of oxygen-enriched smelting), high operating rate (no operating parts such as crushers), and low operating cost.

[0025] (3) The sensible heat recovery system in the utility model is divided into a high temperature zone and a low temperature zone, which is convenient for the graded collection and treatment of heat. An adjustment plate (gate) is set between the high temperature zone and the low temperature zone. According to the principle of "material blocking wind", the zoning effect is basically achieved, so that the steel slag particles can be heated and stuffy at normal pressure in the low temperature zone, thereby greatly accelerating the digestion rate of calcium oxide and magnesium oxide in the steel slag; in addition, the low temperature zone uses the low temperature tail gas of the waste heat boiler as the cooling gas, which can reduce the heat discharged as much as possible through recycling. The cooling air in the low temperature zone adopts a (two-layer) annular wind chamber structure, and multiple air ducts are inserted into the box body to evenly exchange heat with the steel slag particles to prevent the cooling air from "short-circuiting" and affecting the heat exchange effect. The utility model also adds a water mist nozzle on the cooling air duct to digest the calcium oxide and magnesium oxide in the steel slag as soon as possible to form more glass, thereby improving the performance of the steel slag and creating conditions for the high-value utilization of the steel slag.

[0026] (4) The unloading unit of the utility model includes a magnetic separation belt conveyor, on which a plurality of electromagnetic iron removal devices (iron absorbers) are arranged, which can completely remove the slag iron in the steel slag to achieve the purpose of magnetic separation. The steel slag finally discharged is dry slag, which eliminates the disadvantages of the prior art that the water content is high and a large cost is required for drying, thus creating conditions for low-cost use by downstream workers. Compared with the existing steel slag sensible heat recovery technology, the system provided by the utility model is used to recover the sensible heat of the steel slag, which can directly reduce water consumption by 80%, avoid the dangerous situation of explosion caused by water-quenched steel slag, and successfully solve the social image of metallurgical slag as "water slag". Since the moisture content of the system is properly controlled, the steel slag is discharged dry, and the social benefits are significant.

[0027] (5) The entire system can be automatically controlled by DCS and can be integrated into the steelmaking enterprise's smelting system to achieve unified management.

[0028] (6) The system investment provided by the utility model is low, which is only about 40% of the investment of roller crushing + pressure heat stuffing technology. Since the equipment is simple and reliable, the operating rate is increased by more than 30%. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic structural diagram of the sensible heat recovery system provided by the utility model.

[0030] Among them, the names corresponding to the figure numbers are: 1-slag ladle, 2-tundish, 3-granulation fan, 4-sensible heat high-temperature collector, 5-sensible heat low-temperature collector, 6-boiler drum, 7-cooling fan, 8-vibrating feeder, 9-magnetic separation belt conveyor, 10-magnetic absorber, 11-gate, 12-superheater, 13-discharging hopper, 14-wind chamber, 15-air outlet, 16-exhaust port. DETAILED DESCRIPTION

[0031] The present invention is further described below in conjunction with the accompanying drawings and embodiments. The present invention includes but is not limited to the following embodiments.

[0032] like Figure 1 As shown, this embodiment provides a sensible heat recovery system for high-temperature steel slag, including a sensible heat high-temperature collector 4 and a sensible heat low-temperature collector 5 arranged up and down, and a gate 11 is provided between the sensible heat high-temperature collector 4 and the sensible heat low-temperature collector 5. The gate 11 is an automatically adjustable valve, a feed port is provided on the side of the sensible heat high-temperature collector 4, and a granulating fan 3 capable of spraying high-pressure airflow is installed at the feed port; in addition, a superheater 12 capable of heat exchange of nitrogen therein is installed inside the sensible heat high-temperature collector 4, and an air outlet is provided at the upper end of the sensible heat high-temperature collector 4. In actual operation, the high-pressure airflow ejected by the granulating fan 3 toward the sensible heat high-temperature collector 4 breaks the material (liquid slag) into particles. While the high-temperature material contacts the nitrogen ejected by the granulating fan 3, heat exchange is also performed to achieve cooling and solidification of the slag particles. At this time, the nitrogen ejected by the granulating fan 3 absorbs heat and its temperature rises. After the heated nitrogen exchanges heat with the superheater 12, it is discharged from the gas outlet 15 at the upper end of the sensible heat high-temperature collector 4.

[0033] The lower end of the sensible heat low temperature collector 5 is a discharge hopper 13. In order to better realize the discharge, multiple discharge hoppers can be set, and a vibrating feeder 8 is set below each discharge hopper. A magnetic separation belt conveyor 9 is installed below the vibrating feeder 8. The magnetic separation belt conveyor 9 is provided with an iron absorber 10 that can adsorb slag steel in the slag particles. A wind chamber 14 and a cooling fan 7 that can provide cooling air to the wind chamber 14 are also provided. The wind chamber 14 is connected to the inside of the sensible heat low temperature collector 5. The cooling fan 7 conveys cooling air to the sensible heat low temperature collector 5 through the wind chamber 14; in addition, a water mist nozzle is provided on the air outlet duct of the cooling fan 7, and water mist is introduced while blowing. The steel slag particles that have been initially cooled by the sensible heat high temperature collector 4 enter the sensible heat low temperature collector 5 due to gravity, and heat is exchanged with the cooling air. The water mist introduced by the cooling fan 7 becomes water vapor, and the cooling air becomes hot air. An exhaust port 16 that can discharge the hot air is opened at the upper end of the sensible heat low temperature collector 5.

[0034] This embodiment is also provided with a drum 6 capable of heat exchange, and the gas outlet 15 at the upper end of the sensible heat high temperature collector 4 and the exhaust port 16 at the upper end of the sensible heat low temperature collector 5 are both connected to the drum 6, which is used to recover the heat in the high temperature gas in the high temperature collector 4 and the sensible heat low temperature collector 5. The output end of the drum 6 can be connected to the cooling fan 7 to realize the recycling of the gas; it can also be connected to the bag dust collector to be emptied after purification.

[0035] The method of using the system is as follows: the liquid slag (temperature 1600℃) is tilted from the slag ladle 1 to the tundish 2, and the liquid slag flows down from the slag flow trough of the tundish 2 and is crushed by the high-pressure airflow ejected from the granulator (small holes arranged in a U shape or rectangle in front) at the front end of the granulating fan 3. Due to the effect of surface tension, the crushed liquid slag droplets quickly shrink and solidify into spherical particles (temperature 1000℃) with very small particle size. The spherical particles enter the sensible heat high temperature collector 4 horizontally along the tangent direction of the outer wall circle of the high temperature collector 4 to continue cooling and solidification, and the hot air from the lower sensible heat low temperature collector 5 exchanges heat with the slag particles. Due to the effect of gravity, the slag particles fall into the sensible heat low temperature collector 5 and continue to exchange heat with the cooling air supplied by the cooling fan 7. A water mist nozzle is provided on the air outlet pipe of the cooling fan 7. While blowing, water mist is introduced, and the water mist turns into water vapor in the sensible heat low temperature collector 5. Between the sensible heat high temperature collector 4 and the sensible heat low temperature collector 5, there is an automatically adjustable gate. According to the principle of "material blocking wind", the effect of zoning is basically achieved, so that the steel slag particles are heated and stuffy by normal pressure water vapor in the low temperature zone (residence time 1-2 hours), thereby greatly accelerating the digestion rate of calcium oxide and magnesium oxide in the steel slag. The steel slag particles cooled and heated by the sensible heat low temperature collector 5 are unloaded to the magnetic separation belt conveyor 9 through the vibrating feeder 8 under the unloading hopper 13; the slag steel in the steel slag particles is adsorbed and dropped by the magnet 10 (multiple units) on the magnetic separation belt conveyor 9 to form a slag steel pile, which is finally collected and returned to the furnace. The steel slag after magnetic separation is transported to the finished steel slag warehouse for storage by the magnetic separation belt conveyor.

[0036] The nitrogen gas blown into the sensible heat high temperature collector 4 by the granulating fan 3 first exchanges heat with the superheater 12 arranged in the sensible heat high temperature collector 4 after absorbing the sensible heat of the slag particles. The cooled gas is mixed with the hot air from the sensible heat low temperature collector 5 (about 600°C) and enters the drum 6, and exchanges heat with the superheater, economizer, air preheater, etc. in the drum 6 in turn. The cooled nitrogen is divided into two paths, one is pulled back to the system for recycling by the cooling fan 7, and the other is discharged after purification in the bag dust collector.

[0037] In this embodiment, nitrogen is used as the gas source to achieve the crushing and cooling of the liquid slag. In addition, other inert gases can also be used. The working pressure of the gas source is 0.2-0.6Mpa, and the gas consumption per ton of granulated slag is 30-100NM3 / t. The diameter of the granulator spray hole is 4-14mm, among which the diameter of the bottom horizontal hole takes the larger value.

[0038] Take the sensible heat recovery device of 200,000 tons of steel slag as an example: the total slag volume is 200,000 tons, and the slag steel recovery is calculated at 12%, the slag steel is 24,000 tons, and the waste slag can be used 176,000 tons. The annual benefit is calculated as follows:

[0039] (1) Recycle 24,000 tons of slag steel, at RMB 1,000 per ton, with an annual benefit of RMB 24 million;

[0040] (2) Steam sales: 8.2 tons / hour × 7,000 hours × RMB 180 / ton = RMB 10.33 million;

[0041] (3) Sales of steel slag: 176,000 tons × 20 yuan / ton = 3.52 million yuan;

[0042] Total: 37.85 million yuan. Therefore, the use of the system provided by the utility model to recover sensible heat has high economic benefits.

[0043] The utility model has simple process and device, low investment, low energy consumption, few operating parts, high productivity, fully enclosed operation, high sensible heat recovery efficiency, good environmental protection effect, and good economic and social benefits. The sensible heat recovery system provided by the utility model is also suitable for sensible heat recovery of other high-temperature molten slags besides metallurgical slag.

[0044] The above embodiment is only one of the preferred implementation modes of the present utility model and should not be used to limit the protection scope of the present utility model. Any changes or modifications that are made to the main design concept and spirit of the present utility model without any substantive significance, as long as the technical problems solved are still consistent with the present utility model, should be included in the protection scope of the present utility model.

Claims

1. A sensible heat recovery system for high temperature steel slag, characterized in that: It comprises a sensible heat high temperature collector (4) and a sensible heat low temperature collector (5) arranged in an upper and lower position, and a gate (11) is arranged between the sensible heat high temperature collector (4) and the sensible heat low temperature collector (5); a feed port is arranged on the side of the sensible heat high temperature collector (4), and a granulating fan (3) capable of spraying high-pressure airflow is installed at the feed port; The sensible heat recovery system also includes an air supply system for providing cooling air to the sensible heat low-temperature collector (5), and a heat recovery unit capable of recovering heat from the sensible heat high-temperature collector (4) and the sensible heat low-temperature collector (5).

2. A sensible heat recovery system for high temperature steel slag according to claim 1, characterized in that: The air supply system comprises an air duct connected to the interior of the sensible heat low-temperature collector (5), an air chamber (14) connected to the air duct, and a cooling fan (7) connected to the air chamber (14); in addition, a water mist nozzle is provided on the air outlet duct of the cooling fan (7).

3. A sensible heat recovery system for high temperature steel slag according to claim 2, characterized in that: An air outlet (15) is provided at the upper end of the sensible heat high temperature collector (4), and an exhaust port (16) is provided at the upper end of the sensible heat low temperature collector (5); the heat recovery unit is a boiler drum (6), and the air outlet (15) and the exhaust port (16) are both connected to the boiler drum (6).

4. A sensible heat recovery system for high temperature steel slag according to claim 3, characterized in that: A superheater (12) is installed inside the sensible heat high-temperature collector (4) to perform heat exchange on the gas inside the collector.

5. A sensible heat recovery system for high temperature steel slag according to claim 4, characterized in that: A discharging unit is provided at the lower end of the sensible heat low-temperature collector (5).

6. A sensible heat recovery system for high temperature steel slag according to claim 5, characterized in that: The unloading unit comprises a unloading hopper (13) and a vibrating feeder (8) installed below the unloading hopper (13); a magnetic separation belt conveyor (9) is installed below the vibrating feeder (8), and an iron absorber (10) is provided on the magnetic separation belt conveyor (9).

7. A sensible heat recovery system for high temperature steel slag according to claim 6, characterized in that: The discharge hopper (13) is provided in plurality, and the vibrating feeder (8) is also provided in plurality accordingly.

8. A sensible heat recovery system for high temperature steel slag according to claim 7, characterized in that: The output end of the drum (6) is connected to a cooling fan (7).

9. The sensible heat recovery system of high temperature steel slag according to claim 7, characterized in that: The output end of the boiler drum (6) is connected to an external bag dust collector.

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