A device for continuously producing calcium carbide by grading electromagnetic induction heating of calcium coke pellets or calcium coal pellets

Abstract

A kind of calcium coke / coal pellet grading electromagnetic induction heating method continuous production calcium carbide device, by mobile bed preheater, high temperature mobile bed heater, heat preservation delay mobile reaction bed and grate cooler, the conical grate type downcomer of mobile bed preheater bottom is connected with the upper portion of high temperature downlink mobile bed heater, high temperature mobile bed heater outside is provided with electromagnetic induction heating, top calcium carbide gas accumulation area is connected into gas fuel pipeline by calcium carbide gas pipeline and is connected into mobile bed preheater bottom by burner;High temperature mobile bed heater bottom is directly connected with the top of heat preservation delay mobile reaction bed, nitrogen heat exchange pipe is arranged in the middle and lower part of heat preservation delay mobile reaction bed, and the bottom is communicated with the inlet of grate cooler by narrow slit;Grate cooler bottom is provided with distributed wind box of independent air inlet respectively, calcium carbide product discharge valve is arranged at the outlet of grate cooler, high temperature nitrogen extraction port is arranged at the inlet end of grate cooler, in sequence heat exchanger, pressurized circulating fan and distributed wind box are connected.

Description

Technical Field

[0001] This invention provides an apparatus for the continuous production of calcium carbide from calcium coke pellets or calcium coal pellets using a graded electromagnetic induction heating method, which relates to the field of coal chemical industry. Background Technology

[0002] Currently, acetylene is mainly produced on a large scale through the calcium carbide process and is an important raw material for the organic synthesis industry. Calcium carbide is produced from quicklime and carbon through complex physicochemical changes in a calcium carbide furnace. As a new type of carbon material, semi-coke is a solid product made from high-volatile, weakly caking or non-caking coal. After medium- and low-temperature dry distillation and carbonization to remove tar and most of the volatile matter, semi-coke is gradually being promoted for use in the production of calcium carbide, ferroalloys, and other products due to its high fixed carbon content, high resistivity, low ash content, low sulfur content, low phosphorus content, and low price, replacing expensive metallurgical coke. Semi-coke is thus an important raw material in the metallurgical industry.

[0003] The most mature method for calcium carbide production is the traditional electrothermal method. This process has specific requirements for the particle size and quality of the raw materials. The calcium oxide content in the quicklime must be greater than 92%, and the fixed carbon in the coke must be greater than 84%, the ash content less than 15%, the moisture content less than 3%, and the volatile matter less than 1.5%. The particle size of the raw materials is crucial to the production process, especially the quicklime. If the particle size is too small, it can prevent the furnace gas from escaping smoothly, causing problems such as "bed collapse." If the particle size is too large, it reduces the contact area between the coke and calcium oxide, affecting the transfer performance and reducing the reaction rate. Industrially, the particle size range for raw materials is generally required to be 5-30 mm. Due to the small contact area between the blocky coke and CaO (5-30 mm), the solid-solid reaction is severely limited by the transfer process. The reaction process requires the quicklime to be in a molten state and to undergo a chemical reaction by penetrating into the coke block. This means that the electric arc furnace reaction must be carried out at high temperatures (2000-2200℃), with a long reaction time (1-2 h), low single-furnace capacity (70 kt / a), and energy consumption of up to 3250 kW·h per ton of calcium carbide (80% purity), with a thermal efficiency of less than 50%. In addition, the calcium carbide product is an intermittently discharged liquid melt with a temperature of over 2000℃, making heat recovery difficult. The working environment for workers is harsh, and there are secondary pollution and explosion hazards. The process urgently needs improvement.

[0004] The current electric arc furnace heating process involves a cumbersome and complex addition of quicklime and coke. Furthermore, throughout the production and use of limestone and semi-coke, processes such as solid crushing, screening, and transportation are constantly involved, generating large quantities of powdered quicklime, semi-coke, or coke smaller than 6 mm, which urgently need to be utilized. In addition, due to the scarcity of high-quality limestone resources and the severe environmental damage caused by its extraction, increasingly stringent controls on limestone mining have become a bottleneck in domestic quicklime production. Therefore, it is imperative to fully utilize the effective components in carbide slag and improve the recycling rate of limestone.

[0005] The oxythermal calcium carbide production process utilizes fuel combustion in a calcium carbide furnace instead of electric heating to produce calcium carbide, avoiding energy losses during coal-fired power generation. Furthermore, it can be coupled with coal pyrolysis and upgrading to reduce industrial waste emissions, potentially forming a new process route for comprehensive coal utilization. Research on the oxythermal calcium carbide production process has been ongoing since the 1950s. Around 1960, the United States, Germany, and the Netherlands had already built pilot-scale oxythermal calcium carbide production plants. Currently, there are also some large-scale oxythermal calcium carbide production plants abroad. According to reports, producing one ton of calcium carbide requires 1560 Nm³ of oxygen. 3 The process consumes 2.8 tons of coke and 1.2 tons of quicklime, along with 600 kWh of electricity. Although Professor Liu Zhenyu and others proposed a new method for calcium carbide production based on the concept of the oxythermal process by studying the reaction process of powdered coke and calcium oxide, using powdered carbonaceous raw materials (coal or coke) with a particle size less than 0.3 mm and powdered calcium-containing raw materials (calcium carbonate, calcium oxide, calcium hydroxide, or calcium carbide slag), and proposed two reactor structures, the reactor structure and the failure to consider the W-shaped variation of the calcium carbide melting point due to changes in calcium carbide content mean that the calcium carbide produced by the oxythermal process, like the electrothermal process, is a liquid product. The unreasonable selection of the calcium-to-coke ratio makes heat recovery from the calcium carbide difficult, and the preheating of the raw materials still utilizes the byproduct high-temperature CO. Compared with foreign oxythermal processes, neither oxygen nor carbon consumption has been significantly reduced, and no industrial pilot-scale or industrial-scale results have been observed.

[0006] The present inventors have proposed a staged oxythermal process for producing calcium carbide from calcium coke pellets (ZL201710455219.4). This process combines a moving bed preheater, a rotary kiln reactor, and a heat-insulated delayed moving reaction bed. Different combustion aids are selected for staged combustion, which reduces oxygen consumption and alleviates the difficulty of tail gas utilization and treatment. The calcium coke pellet reaction not only solves the problem of reusing quicklime powder and coke powder, but also reduces the reaction temperature, accelerates the reaction rate, reduces production energy consumption and costs, improves the processing capacity of the calcium carbide furnace, and realizes the recycling of high-quality limestone resources and eliminates solid waste pollution. In actual operation, because rotary kilns are rotating equipment, the sealing and internal lining materials are expensive and easily damaged, making it difficult to guarantee long-term stable operation and posing significant safety hazards such as leakage and lining damage and burn-through. The burner temperature of the pure oxygen semi-coke powder at the rotary kiln head is too high, resulting in severe wear and high equipment investment. In addition, in order to avoid the reaction of nitrogen with high-temperature calcium carbide to form calcium cyanamide, inert gas is used as a direct cooling medium to recover the waste heat of calcium carbide, which is costly and scarce. All of these factors seriously affect the promotion and application of the calcium coke pellet staged oxygen thermal process for producing calcium carbide.

[0007] Therefore, there is an urgent need to develop new processes and supporting equipment technologies for the continuous production of acetylene using quicklime powder and coke powder, which are characterized by simple equipment structure, low investment, low comprehensive energy consumption and cost, and the ability to operate stably for a long period of time. This will improve the recycling rate of carbide slag, reduce reaction temperature, accelerate reaction speed, reduce production energy consumption and costs, improve the processing capacity and heat recovery rate of carbide furnaces, and eliminate secondary pollution. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of existing electrothermal and oxythermal methods for acetylene production by proposing a device for the continuous production of calcium carbide using a staged electromagnetic induction heating method for calcium coke pellets or calcium coal pellets. This device rationally selects the ratio of calcium coke or calcium coal, ensuring efficient reaction while maintaining a solid product for easy waste heat recovery. It employs a stepped heating reaction combining low-temperature air and gas combustion heating with high-temperature electromagnetic induction heating, eliminating the need for oxygen consumption. The calcium coke pellets are heated internally by electronic eddy currents, significantly improving electrothermal conversion efficiency and reducing the difficulty of tail gas utilization and treatment. The calcium coke pellet reaction not only solves the problem of reusing calcium carbide slag and coke powder, but also lowers the reaction temperature, accelerates the reaction rate, reduces production energy consumption and costs, improves the processing capacity of the calcium carbide furnace, and achieves the recycling of high-quality limestone resources while eliminating solid waste pollution.

[0009] The technical solution of the present invention:

[0010] An apparatus for the continuous production of calcium carbide from calcium coke pellets or calcium coal pellets using a staged electromagnetic induction heating method mainly consists of a moving bed preheater, a high-temperature moving bed heater, a heat-insulated delayed moving reaction bed, and a grate cooler. The moving bed preheater is connected to the upper part of the high-temperature moving bed heater via a conical grate downcomer at its bottom. An electromagnetic induction heater is installed outside the high-temperature moving bed heater. The calcium carbide gas accumulation cavity at the top is connected to a gaseous fuel pipeline via a calcium carbide gas pipeline and then to the bottom of the moving bed preheater via a burner. The bottom of the high-temperature moving bed heater is directly connected to the top of the heat-insulated delayed moving reaction bed. Nitrogen gas is provided in the lower part of the heat-insulated delayed moving reaction bed. The heat exchange tubes are connected to the inlet of the grate cooler through narrow slots at the bottom. The bottom of the grate cooler is equipped with distributed air boxes with independent air inlets. The outlet of the grate cooler is equipped with a calcium carbide product discharge valve. The inlet end of the grate cooler is equipped with a high-temperature nitrogen extraction port, which is connected in sequence to the heat exchanger, pressurized circulating fan and distributed air boxes. The diameter / equivalent diameter ratio of the moving bed preheater, high-temperature moving bed heater and heat-insulating delayed moving reaction bed is 1-5:1:1-20. The height-to-diameter ratio of the moving bed preheater is 5-20:1. The height-to-diameter ratio of the high-temperature moving bed heater is 3-10:1. The equivalent height-to-diameter ratio of the heat-insulating delayed moving reaction bed is 6-40:1.

[0011] The moving bed preheater has a rotary sealed feeder and a discharge pipe at the top center, with the discharge pipe being 50-1000mm long. A tail gas outlet is located on the top side, which is sequentially connected to a gas-solid separator, a supplementary combustion air preheater, a waste heat boiler, and an induced draft fan. The bottom has a head with a conical grate-type downcomer, facilitating the entry of preheated air and high-temperature flue gas generated from the combustion of supplementary calcium carbide gas into the moving bed preheater to heat the calcium coke pellets. The opening rate is 10%-70%, and the cone angle is 45°-150°. The conical grate-type downcomer extends 200-800mm into the high-temperature moving bed heater.

[0012] The high-temperature moving bed heater is an electromagnetic induction external heating reactor, which is sealed to the upper moving bed preheater. A local cavity is formed at the top of the high-temperature moving bed heater through the extended conical grate downcomer. The cavity is connected to the gas fuel pipeline, which facilitates the accumulation of calcium carbide gas containing CO and its being drawn into the gas fuel pipeline at the bottom of the moving bed preheater. The calcium coke and coal briquettes in the conical grate downcomer form a solid material seal, increasing the pressure and preventing backflow.

[0013] The insulated delayed moving reaction bed has a rectangular structure. The top is connected to the high-temperature moving bed heater through a top-square-bottom-round connection. A nitrogen heat exchange tube is installed in the middle and downwards. The bottom is equipped with a conical head with a cone angle of 45°-150°. A narrow rectangular slit with a length equal to that of the insulated delayed moving reaction bed and a width of 50-300mm is opened in the center.

[0014] The features of the present invention will be described in detail through embodiments. Attached Figure Description

[0015] The attached figure is a schematic diagram of the process of the present invention.

[0016] The accompanying drawings are described below:

[0017] 1. Feeder 2. Moving bed preheater 3. Gas-solid separator 4. Supplementary combustion air preheater 5. Waste heat boiler 6. Exhaust fan 7. Conical grate downcomer 8. Burner 9. High-temperature moving bed heater 10. Calcium carbide gas pipeline 11. End cap 12. Insulated delayed moving reaction bed 13. Electromagnetic induction external heater 14. Heat exchanger tube 15. Pressurized blower 16. Calcium carbide product discharge valve 17. Grate cooler 18. Heat exchanger A. Calcium coke pellets B. Gaseous fuel C. Air

[0018] The process features of the present invention will be described in detail below with reference to the accompanying drawings and embodiments. Detailed Implementation

[0019] An apparatus for the continuous production of calcium carbide from calcium coke pellets or calcium coal pellets by a staged electromagnetic induction heating method mainly consists of a moving bed preheater (2), a high-temperature moving bed heater (9), a heat-insulating delayed moving reaction bed (12), and a grate cooler (17). The moving bed preheater (2) is connected to the upper part of the high-temperature moving bed heater (9) through a conical grate downcomer at the bottom. An electromagnetic induction heater is installed outside the high-temperature moving bed heater (9). A conical grate downcomer (7) extends into the top of the high-temperature moving bed heater (9) and forms a calcium carbide gas accumulation cavity with the calcium coke pellet layer. The calcium carbide gas is connected to the gas fuel pipeline through the calcium carbide gas pipeline (10) and then to the bottom of the moving bed preheater (2) through the burner (8). The bottom of the high-temperature moving bed heater (9) is directly connected to the top of the heat-insulating delayed moving reaction bed (12). The lower part of the moving reaction bed (12) is provided with a nitrogen heat exchange tube (14), and the bottom is connected to the inlet of the grate cooler (17) through a narrow strip. The bottom of the grate cooler (17) is provided with a distributed air box with independent air intake. The outlet of the grate cooler (17) is provided with a calcium carbide product discharge valve (16). The inlet end of the grate cooler (17) is provided with a high temperature nitrogen extraction outlet, which is connected in sequence to the heat exchanger (18), the pressurizing fan (15) and the distributed air box. The diameter / equivalent diameter ratio of the moving bed preheater (2), the high temperature moving bed heater (9) and the heat preservation delayed moving reaction bed (12) is 1-5:1:1-20. The height-to-diameter ratio of the moving bed preheater (2) is 5-20:1. The height-to-diameter ratio of the high temperature moving bed heater (9) is 3-10:1. The equivalent height-to-diameter ratio of the heat preservation delayed moving reaction bed (12) is 6-40:1.

[0020] Among them, the moving bed preheater (2) is equipped with a rotary sealing feeder (1) and a discharge pipe at the top center, with the discharge pipe being 50-1000 mm long; the top side is equipped with a tail gas outlet, which is connected in sequence to a gas-solid separator (3), a supplementary combustion air preheater (4), a waste heat boiler (5), and an induced draft fan (6); the bottom is a head (11) with a conical grate downcomer (7), which facilitates the entry of preheated air and high-temperature flue gas generated by the combustion of supplemented calcium carbide gas into the moving bed preheater (2) to heat the calcium coke pellets. The opening rate is 10%-70%, the cone angle is 45°-150°, and the conical grate downcomer (7) extends into the high-temperature downward moving bed heater (9) by 200-800 mm.

[0021] The high-temperature downward moving bed heater (9) is a reactor that is heated by combustion of pure oxygen or by external electromagnetic induction. It is sealed to the upper moving bed preheater (2). A local cavity is formed at the top of the high-temperature downward moving bed heater (9) through the extended conical grate downcomer (7). The cavity is connected to the gas fuel pipeline through the calcium carbide gas pipeline (10), which facilitates the accumulation of calcium carbide gas containing CO and its being drawn into the gas fuel pipeline at the bottom of the moving bed preheater (2). The calcium coke and coal pellets in the conical grate downcomer (7) form a solid material seal, which increases the pressure and prevents backflow.

[0022] The heat-insulated delayed moving reaction bed (12) has a rectangular structure. The top is connected to the high-temperature downward moving bed heater (9) through a square top and a round bottom. An inert gas heat exchange tube (14) is provided in the middle and downward. A conical head is provided at the bottom with a conical angle of 45°-150°. A narrow slit with the same length as the moving bed and a width of 50-300 mm is opened in the center.

[0023] In specific operation, a device for the continuous production of calcium carbide by a graded electromagnetic induction heating method for calcium coke pellets or calcium coal pellets is used. 5-30 mm calcium coke pellets or calcium coal pellets are fed into a moving bed preheater (2) via a feeder (1). Preheated air, gaseous fuel, and calcium carbide gas are burned in a burner (8). High-temperature flue gas rises from the bottom of the moving bed preheater (2) and exchanges heat counter-currently with the calcium coke pellets or calcium coal pellets to 900-1300℃. Then, it is heated to 1700-2000℃ by a high-temperature downward moving bed heater (9) and an electromagnetic induction external heater (13). Partial reaction produces calcium carbide while releasing CO. The CO-containing calcium carbide gas is drawn into the gaseous fuel (A) pipeline at the bottom of the moving bed preheater (2) via a calcium carbide gas pipeline (10). The calcium carbide-producing pellets flow into the heat-insulating and delayed moving reaction bed (9) for an enhanced reaction of 5-90 minutes, and are then heated by the heat exchanger tube (14). Nitrogen gas is cooled to below 800℃ and then flows into the grate cooler (13) from the bottom of the heat-insulating delayed moving reaction bed (12). In the grate cooler (13), nitrogen gas directly contacts and exchanges heat. After cooling to below 100℃, it reacts with water vapor to produce acetylene and carbide slag. The high-temperature nitrogen gas is recovered by the heat exchanger (18) and then pressurized and sent back to the heat exchange tube (14) and the grate cooler (13) for recycling. The tail gas at the top of the moving bed preheater (2) is combusted and preheated by the supplementary combustion air preheater (4). After the heat is recovered by the waste heat boiler (5), it is drawn out by the induced draft fan (6). After the ash content of the carbide slag is removed, it is mixed evenly with calcium coke or calcium coal powder and binder at a ratio of 1.3-2.0:1:0-0.1 (by weight) and pressed into 5-30 mm calcium coke and coal pellets.

[0024] This invention provides an apparatus for the continuous production of calcium carbide from calcium coke pellets or calcium coal pellets via a staged electromagnetic induction heating method. By selecting a suitable calcium-to-coke ratio, the calcium carbide content in the calcium carbide is ensured to be greater than 80%, guaranteeing that the calcium carbide product is solid, facilitating flow and waste heat recovery. The apparatus utilizes the in-situ reaction of coke powder or coal powder with calcium carbide slag to produce calcium carbide through calcium coke pellets. The use of a stepped heating method with different combinations of combustion aids or external heating reduces oxygen consumption by more than 70% (compared to the oxythermal method), alleviating the difficulty of tail gas utilization and treatment, and simultaneously reducing the difficulty of separating impurities from the calcium carbide slag. The in-situ reaction of calcium coke pellets to produce calcium carbide utilizes inexpensive coal powder or coke powder. The production of powdered and powdered calcium carbide slag reduces the reaction temperature by more than 300℃, accelerates the reaction rate by more than 2 times, enables continuous acetylene production, reduces production costs by more than 50%, reduces power consumption by 60% (compared to the electric arc method), and achieves a calcium carbide slag recycling rate of more than 90%, eliminating calcium carbide slag pollution. By using inexpensive and widely available nitrogen as a heat exchange medium, more than 90% of the waste heat from calcium carbide is recovered and discharged in a low-cost, graded manner using heat exchange tubes and grate coolers, eliminating secondary pollution and explosion hazards from high-temperature calcium carbide liquid discharge, avoiding the formation of calcium cyanamide byproducts, and improving the working environment for workers.

Claims

1. An apparatus for the continuous production of calcium carbide from calcium coke pellets or calcium coal pellets by graded electromagnetic induction heating, characterized in that... It mainly consists of a moving bed preheater, a high-temperature moving bed heater, an insulated delayed moving reaction bed, and a grate cooler. The moving bed preheater is connected to the upper part of the high-temperature moving bed heater through a conical grate downcomer at the bottom. An electromagnetic induction heater is installed outside the high-temperature moving bed heater. The high-temperature moving bed heater forms a top calcium carbide gas accumulation cavity at the top of the high-temperature moving bed heater through the extended conical grate downcomer. The top calcium carbide gas accumulation cavity is connected to a gaseous fuel pipeline. The gaseous fuel pipeline is equipped with a burner. Calcium carbide gas containing CO accumulates in the top calcium carbide gas accumulation cavity and enters the gaseous fuel pipeline, and is then introduced into the bottom of the moving bed preheater through the burner. The bottom of the high-temperature moving bed heater is connected to the insulated delayed moving reaction bed. The top of the delayed moving bed is directly connected; the lower part of the insulated delayed moving bed is equipped with a nitrogen heat exchange tube, and the bottom is connected to the inlet of the grate cooler through a narrow slit; the bottom of the grate cooler is equipped with a distributed air box with independent air inlet, the outlet of the grate cooler is equipped with a calcium carbide product discharge valve, and the inlet end of the grate cooler is equipped with a high-temperature nitrogen extraction port, which is connected in sequence to the heat exchanger, the pressurized circulating fan and the distributed air box; the diameter / equivalent diameter ratio of the moving bed preheater, the high-temperature moving bed heater and the insulated delayed moving bed is 1-5:1:1-20, the height-to-diameter ratio of the moving bed preheater is 5-20:1, the height-to-diameter ratio of the high-temperature moving bed heater is 3-10:1, and the equivalent height-to-diameter ratio of the insulated delayed moving bed is 6-40:

1.

2. The apparatus for continuous production of calcium carbide from calcium coke pellets or calcium coal pellets by graded electromagnetic induction heating according to claim 1, characterized in that... The moving bed preheater has a rotary sealed feeder and a discharge pipe at the top center, with the discharge pipe being 50-1000 mm long. The top side has an exhaust gas outlet, which is connected in sequence to a gas-solid separator, a supplementary combustion air preheater, a waste heat boiler, and an induced draft fan. The bottom has a head with a conical grate-type downcomer, which facilitates the entry of preheated air and high-temperature flue gas generated by the combustion of supplementary calcium carbide gas into the moving bed preheater to heat calcium coke pellets or calcium coal pellets. The opening ratio is 10%-70%, the cone angle is 45°-150°, and the conical grate-type downcomer extends 200-800 mm into the high-temperature moving bed heater.

3. The apparatus for continuous production of calcium carbide from calcium coke pellets or calcium coal pellets by graded electromagnetic induction heating according to claim 1, characterized in that... The insulated delayed moving reaction bed has a rectangular structure. The top is connected to the high-temperature moving bed heater through a top-square-bottom-round connection. A nitrogen heat exchange tube is installed in the middle and downwards. A conical head is installed at the bottom with a cone angle of 45°-150°. A narrow rectangular slit with a length equal to that of the insulated delayed moving reaction bed and a width of 50-300 mm is opened in the center.

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