A system and method for recovering sensible heat from calcium carbide for power generation

Abstract

The present invention relates to a system and method for recovering sensible heat from calcium carbide for power generation. The device comprises: a spray granulation unit for granulating molten calcium carbide, a cooling and heat-exchanging material receiving unit for cooling calcium carbide particles and heating CO2 gas, a power generation unit for CO2 gas power generation, and a gas circulation unit for controlling the temperature and pressure of CO2 circulating gas. The spray granulation unit comprises a calcium carbide discharge port and a high-pressure spraying device in sequence; the cooling and heat-exchanging material receiving unit comprises a cooling material receiving bin, a cooling rotary kiln, a large gear ring, a transmission base, a closed-loop material receiving device, and a material cart in sequence; the power generation unit comprises a compressor, a pressure gauge, a gas thermometer, a gas heating device, a turbine, a generator, and a control computer in sequence; the gas circulation unit comprises a gas valve, a waste heat recovery device, a sealed gas storage tank, and a gas pressure reducing device in sequence. The present invention provides a device for recovering sensible heat from calcium carbide for power generation, which has the advantages of stable product quality, low operating cost, compact structure, and high power generation efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of power generation systems, and relates to a waste heat recovery device and method, and in particular to a system and method for recovering sensible heat from calcium carbide for power generation. Background Art

[0002] The common process for industrial calcium carbide production is the electrothermal method, in which quicklime (CaO) and coke (C) react at high temperatures of 1800°C to 2200°C in a submerged arc electric furnace, producing carbon monoxide as a byproduct. Smelted calcium carbide is discharged from the furnace mouth approximately every hour, with the molten carbide flowing into a carbide pot on a traction trolley. The pot is then transported by winches, bridge cranes, and other transport equipment to a "hot pot pre-cooling zone" for cooling. After two hours of cooling, the calcium carbide mass is removed from the pot and placed in a cooling zone for further cooling. During the cooling process, the calcium carbide cools from 2000°C to 80°C, dissipating a significant amount of sensible heat, resulting in significant heat waste. This heat also dissipates into the workshop, polluting the production environment, increasing the working temperature, and causing significant harm to production workers. Furthermore, the calcium carbide reacts with oxygen and nitrogen in the air, significantly reducing its quality.

[0003] Chinese patent CN105066715B provides a heat collection device for recovering waste heat from the calcium carbide cooling process. Solutions using tunnel kiln heat recovery technology require the installation of a tunnel kiln to extract heat from the calcium carbide pot when placed in the tunnel kiln. Chinese patent CN109084588B provides a furnace discharge system for calcium carbide sensible heat power generation, comprising a conveyor track, a furnace discharge vehicle, a mobile platform, a manipulator, a traction track, a tractor, a winch, and a tunnel kiln. This system enables the continuous transportation of the calcium carbide pot to the tunnel kiln for unloading and removal, thereby reducing heat loss during the calcium carbide transportation process. The above devices all have a prominent problem: high-temperature molten calcium carbide is exposed to air for cooling, and the N2 and O2 in the air react with the hot calcium carbide to form calcium cyanamide and calcium oxide, reducing the quality of the calcium carbide product. Patent CN106276905B discloses a method for granulating molten calcium carbide. The cooling gas used in the granulation process is an inert gas such as neon or argon. This recovers heat while also eliminating the need for further pulverization of the granulated calcium carbide. However, this method uses neon or argon as a heat exchange gas, which has a high gas cost and is not conducive to reducing the production cost of the enterprise. Patent CN104792184A provides a system and method for recovering waste heat from molten calcium carbide, which uses N2 or CO2 to cool the hot calcium carbide in the calcium carbide forming chain and cooling chain, and then uses high-temperature gas to heat steam to generate electricity. However, the calcium carbide in this method is cooled in a large solid state, and it is difficult to ensure its cooling rate. In addition, the energy loss in the process of high-temperature gas thermal energy → hot steam → electrical energy is large, and the presence of water makes the system operation risky. Patents CN106823774A and CN111100957A also mention methods of using high-temperature gas to generate superheated steam for power generation, but the above-mentioned safety issues also exist.

[0004] Therefore, there is an urgent need for a device for recovering sensible heat from calcium carbide for power generation that is safe, stable, has low operating costs, a compact structure, high heat recovery efficiency, and stable calcium carbide quality. Summary of the Invention

[0005] The purpose of the present invention is to solve the problem of waste of sensible heat of hot calcium carbide, provide a system and method for recovering sensible heat of calcium carbide for power generation, reduce the floor space required for cooling and crushing calcium carbide, and reduce the production cost of calcium carbide.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention provides a system for recovering sensible heat from calcium carbide for power generation. The device comprises a spraying and granulating unit, a cooling and heat-exchanging material-collecting unit, a power generation unit and a gas circulation unit.

[0008] Furthermore, the spray granulation unit includes a calcium carbide discharge port and a high-pressure spray device in sequence; the cooling and heat exchange material receiving unit includes a cooling material receiving bin, a cooling rotary kiln, a large gear ring, a transmission base, a closed cycle material receiving device and a material cart in sequence; the power generation unit includes a compressor, a pressure gauge, a gas thermometer, a gas heating device, a turbine and a generator in sequence; the gas circulation unit includes a gas valve, a waste heat recovery device, a sealed gas storage tank, and a gas pressure reducing device in sequence;

[0009] Among them, the calcium carbide discharge port is located above the high-pressure blowing device, the calcium carbide discharge port is located at the outlet of the high-pressure blowing device, and the calcium carbide discharge port and the outlet of the high-pressure blowing device are both inserted into the wall side of the cooling receiving bin, the cooling rotary kiln, the large gear ring and the transmission base are all located inside the cooling receiving bin, the cooling rotary kiln is located on the blowing direction side of the high-pressure blowing device, and is installed on the large gear ring and the transmission base, the receiving port of the closed-loop receiving device extends into the cooling receiving bin and is arranged on the lower side of the cooling rotary kiln outlet, the material cart is arranged below the discharge port of the closed-loop receiving device, the compressor, pressure gauge and gas thermometer are arranged on the air outlet pipe of the cooling receiving bin, the gas heating device, turbine and generator are all arranged after the compressor, and the gas heating device is arranged before the turbine, the waste heat recovery device is connected to the air outlet of the turbine, the sealed gas storage pipe is arranged after the waste heat recovery device and is connected to the gas pressure reducing device.

[0010] Furthermore, the blowing, cooling and circulating gases in the blowing granulation unit, cooling heat exchange and material collecting unit, power generation unit and gas circulation unit are all CO2.

[0011] Furthermore, the injection angle of the high-pressure blowing device is 10°~60° with respect to the horizontal direction, and the nozzle outlet pressure is 0.2 MPa~2 MPa.

[0012] Furthermore, the closed-loop material collecting device is provided with a sealing ring to perform a cyclical material discharging operation.

[0013] Furthermore, the compressor outlet gas pressure is not less than 7.8 MPa.

[0014] Furthermore, the temperature of the CO2 gas at the turbine inlet is not lower than 600°C.

[0015] Furthermore, the temperature of the CO2 gas at the outlet of the waste heat recovery device is not higher than 150°C.

[0016] Furthermore, the gas pressure at the outlet of the gas decompression device is not higher than 0.15 MPa.

[0017] Furthermore, the pressure gauge, gas thermometer and gas valve are all connected to a computer, and the pressure and temperature data are transmitted to the computer in real time, and the opening and closing of the gas valve are automatically controlled.

[0018] The present invention also provides a method for recovering sensible heat from calcium carbide for power generation, comprising the following steps:

[0019] (1) Granulation and cooling of calcium carbide melt: The molten calcium carbide flows out from the calcium carbide discharge port, and is blown by the high-pressure blowing device below it to form calcium carbide particles. The particles are quickly cooled by the low-temperature CO2 gas and fall into the cooling rotary kiln. The calcium carbide particles continuously exchange heat with the low-temperature CO2 gas in the rotary kiln, and then fall into the sealed circulation receiving device and finally enter the material truck for transportation;

[0020] (2) After the low-temperature CO2 gas undergoes heat exchange with the calcium carbide particles, it is pressurized by a compressor and then measured by a gas thermometer. If the temperature is lower than the threshold, it enters the gas heating device to increase its temperature. If the temperature is higher than the threshold, it directly drives the generator through the turbine to generate electricity.

[0021] (3) The CO2 gas after passing through the turbine is cooled by a waste heat recovery device, and after the pressure is reduced by a gas pressure reducing device, it enters the cooling and collecting bin for recycling.

[0022] The present invention has the following beneficial effects:

[0023] The calcium carbide sensible heat recovery power generation device and method of the present invention has the advantages of stable calcium carbide product quality, high yield rate, low operating cost, compact structure, and high power generation efficiency.

[0024] First, calcium carbide is directly sprayed into granules in a molten state, which greatly improves its heat transfer rate and eliminates the previous cooling and crushing process, greatly helping to reduce production costs.

[0025] Secondly, CO2 is used as the cooling circulating gas, which does not react chemically with hot calcium carbide, thus ensuring the quality of calcium carbide products;

[0026] Third, the temperature of CO2 gas and calcium carbide particles can reach above 600℃ after heat exchange. After compression, it can form a "supercritical fluid" to drive the turbine to rotate and generate electricity. Compared with heating steam to generate electricity, this method has fewer energy conversion links, so its power generation efficiency is higher.

[0027] The efficiency is 3%~5% higher than that of steam units with the same installed capacity, and the volume is only about 5% of that of steam units;

[0028] Fourthly, the high-temperature CO2 gas after power generation can also be used for waste heat recovery, making the maximum use of sensible heat;

[0029] The present invention creates a low-temperature, comfortable and healthy working environment for production workers, and has a promising prospect in better application and promotion in the calcium carbide industrial system.

[0030] Of course, any product implementing the present invention does not necessarily need to achieve all of the above-mentioned technical effects at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0032] Figure 1 A structural diagram of a device for recovering sensible heat from calcium carbide for power generation according to one embodiment of the present invention;

[0033] In the figure: 101-calcium carbide outlet; 102-high-pressure blowing device; 201-cooling and collecting bin; 202-cooling rotary kiln; 203-large ring gear; 204-transmission base; 205-closed cycle collecting device; 206-material cart; 301-compressor; 302-pressure gauge; 303-gas thermometer; 304-gas heating device; 305-turbine; 306-generator; 307-control computer; 401-gas valve; 402-waste heat recovery device; 403-sealed gas storage tank; 404-gas pressure reducing device. DETAILED DESCRIPTION

[0034] In order to better understand the technical solution of the present invention, the embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0035] It should be understood that the embodiments described are only a portion of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative work are within the scope of protection of the present invention.

[0036] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The singular forms "a", "an", "the" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise.

[0037] like Figure 1 As shown, the present invention provides a system for recovering sensible heat from calcium carbide for power generation. The device consists of a spraying granulation unit, a cooling heat exchange and material collection unit, a power generation unit and a gas circulation unit.

[0038] The spray granulation unit includes a calcium carbide discharge port 101 and a high-pressure spray device 102. The high-pressure spray device is used for spraying to form granular calcium carbide and is arranged below the calcium carbide discharge port.

[0039] The cooling, heat exchange, and material collection unit includes a cooling material collection bin 201, a cooling rotary kiln 202, a large ring gear 203, a drive base 204, a closed-loop material collection device 205, and a material cart 206. The cooling rotary kiln is used to collect, cool, and transport calcium carbide particles and is located on one side of the calcium carbide discharge port and the gas outlet of the high-pressure injection device. The large ring gear and drive base are used to rotate the cooling rotary kiln and are located below the cold zone rotary kiln. The closed-loop material collection device is used to collect calcium carbide particles and is located below the cooling rotary kiln outlet.

[0040] The power generation unit includes a compressor 301, a pressure gauge 302, a gas thermometer 303, a gas heating device 304, a turbine 305, a generator 306, and a control computer 307. The compressor is used to pressurize the CO2 gas to above 7.8 MPa, the gas heating device is used to heat the CO2 gas to form a "supercritical fluid", and the turbine rotates to drive the generator to generate electricity. The compressor, gas heating device, turbine, and generator are connected in sequence. The pressure gauge and gas thermometer are connected to the control computer, transmitting pressure and temperature information in real time and regulating the opening and closing of various gas valves through the control computer.

[0041] The gas circulation unit includes a gas valve 401, a waste heat recovery device 402, a sealed gas storage tank 403, and a gas pressure reducing device 404. The gas valve is used to control whether the CO2 gas in the pipeline enters the gas heating device, the waste heat recovery device and the sealed gas storage tank, and the opening or closing of the gas valve is adjusted by the control computer. The waste heat recovery device is used to recover the heat of the high-temperature CO2 gas after passing through the turbine and reduce its temperature to below 150°C. It is arranged at the rear end of the turbine. The sealed gas storage pipe is used to store CO2 gas and replenish or reduce CO2 gas to the circulation system by controlling the opening and closing of the gas valve. It is arranged after the waste heat recovery device. The gas pressure reducing device is used to reduce the pressure of the cooled CO2 gas to below 0.15 MPa. It is arranged at the front end of the air inlet of the cooling and collecting bin.

[0042] The injection angle of the high-pressure blowing device is 10°~60° with the horizontal direction, and the nozzle outlet pressure is 0.2 MPa~2MPa; the closed-loop material receiving device is provided with a sealing ring, which can perform cyclic discharging operations; the compressor outlet gas pressure is not less than 7.8 MPa; the CO2 gas temperature at the turbine inlet is not less than 600℃; the CO2 gas temperature at the waste heat recovery device outlet is not higher than 150℃; the gas pressure at the gas pressure reducing device outlet is not higher than 0.15 MPa; the pressure gauge, gas thermometer, and gas valve are all connected to the computer, and the pressure and temperature data are transmitted to the computer in real time, and the opening and closing of the gas valve are automatically controlled.

[0043] The specific recovery power generation method of the present invention is as follows:

[0044] 1. Granulation and cooling of calcium carbide melt: The molten calcium carbide flows out from the calcium carbide discharge port and is blown by 0.4 MPa ~ 1.5 MPa gas from the high-pressure blowing device installed below it to form calcium carbide particles. The particles are quickly cooled by the low-temperature CO2 gas and fall into the cooling rotary kiln. The calcium carbide particles are continuously heat exchanged by the low-temperature CO2 gas in the rotary kiln, and then fall into the sealed circulation collecting device and finally enter the material truck for transportation.

[0045] 2. After the low-temperature CO2 gas undergoes heat exchange with the calcium carbide particles, it is pressurized to above 0.78 MPa through a compressor and measured by a gas thermometer. The pressure and temperature data are transmitted to the control computer in real time. If the temperature is lower than 600°C, the control computer closes valve 401-1 and opens valve 401-2 to allow the CO2 to enter the gas heating device for heating. If the temperature is higher than 600°C, the control computer opens valve 401-1 and closes valve 401-2 to allow the CO2 gas to pass directly through the turbine. The turbine rotates to drive the generator to generate electricity.

[0046] 3. The temperature of the CO2 gas after passing through the turbine is measured. If the temperature is lower than 150°C, the control computer opens valve 401-3 and closes valve 401-4, allowing the CO2 to enter the gas decompression device. If the temperature is higher than 150°C, the control computer opens valve 401-4 and closes valve 401-3, allowing the CO2 gas to enter the waste heat recovery device and be cooled to below 150°C. After the pressure is reduced by the gas decompression device, the CO2 gas enters the cooling and receiving bin for recycling.

[0047] The above describes in detail the device and method for recovering sensible heat from calcium carbide for power generation provided in the embodiments of the present application. The description of the above embodiments is only intended to help understand the method and core concept of the present application; at the same time, for those skilled in the art, based on the concept of the present application, there may be changes in the specific implementation method and application scope. In summary, the contents of this specification should not be understood as limiting the present application.

[0048] For example, certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that hardware manufacturers may use different nouns to refer to the same component. This specification and claims do not use differences in names as a way to distinguish components, but use differences in the functions of components as the criteria for distinction. For example, "including" and "comprising" mentioned throughout the specification and claims are open-ended terms, so they should be interpreted as "including / including but not limited to". "Approximately" means that within an acceptable error range, those skilled in the art can solve the technical problems within a certain error range and basically achieve the technical effects. The subsequent description in the specification is a preferred embodiment of the present application, but the description is for the purpose of illustrating the general principles of the present application, and is not used to limit the scope of the present application. The scope of protection of the present application shall be as defined in the attached claims.

[0049] It should also be noted that the terms "include," "comprises," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a product or system comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such product or system. In the absence of further limitations, an element defined by the phrase "comprises a..." does not exclude the presence of other identical elements in the product or system comprising the element.

[0050] It should be understood that the term "and / or" as used herein is merely a description of the relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A exists alone, A and B exist simultaneously, or B exists alone. Furthermore, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0051] The above description shows and describes several preferred embodiments of the present application. However, as previously mentioned, it should be understood that the present application is not limited to the form disclosed herein and should not be construed as excluding other embodiments. Instead, the present application can be used in various other combinations, modifications, and environments and can be modified within the scope of the application concept described herein through the above teachings or technology or knowledge in the relevant field. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present application should be protected by the claims appended hereto.

Claims

1. A system for recovering sensible heat from calcium carbide for power generation, characterized in that: The system comprises: The spray granulation unit is used to granulate the molten calcium carbide; Cooling and heat exchange receiving unit, used for cooling calcium carbide particles and heating CO2 gas; A power generation unit, used to recover the heated CO2 gas to generate electricity; Gas circulation unit, used to control the temperature and pressure of CO2 circulating gas; The spray granulation unit, cooling heat exchange material receiving unit, power generation unit and gas circulation unit are connected in sequence, and the spraying, cooling, power generation and circulating gases in the spray granulation unit, cooling heat exchange material receiving unit, power generation unit and gas circulation unit are all CO2; The spray granulation unit includes a calcium carbide discharge port and a high-pressure spray device; The cooling heat exchange material collecting unit includes a cooling material collecting bin, a cooling rotary kiln, a large gear ring, a transmission base, a closed cycle material collecting device and a material cart; The power generation unit includes a compressor, a pressure gauge, a gas thermometer, a gas heating device, a turbine and a generator; The gas circulation unit includes a gas valve, a waste heat recovery device, a sealed gas storage tank and a gas pressure reducing device; in: The calcium carbide discharge port is located above the high-pressure blowing device, the calcium carbide discharge port is located at the outlet of the high-pressure blowing device, and the calcium carbide discharge port and the outlet of the high-pressure blowing device are both inserted into one side of the wall of the cooling receiving bin; The cooling rotary kiln, the large gear ring and the transmission base are all located inside the cooling material receiving bin. The cooling rotary kiln is located on the blowing direction side of the high-pressure blowing device and is installed on the large gear ring and the transmission base. The receiving port of the closed-loop receiving device extends into the cooling material receiving bin and is arranged at the lower side of the cooling rotary kiln outlet. The material cart is arranged below the discharge port of the closed-loop receiving device. The compressor, pressure gauge and gas thermometer are arranged on the gas outlet pipe of the cooling and receiving bin, the gas heating device, turbine and generator are all arranged after the compressor, and the gas heating device is arranged before the turbine; The waste heat recovery device is connected to the gas outlet of the turbine, and the sealed gas storage pipe is arranged after the waste heat recovery device and connected to the gas decompression device; The injection angle of the high-pressure blowing device is 10° to 60° with respect to the horizontal direction, and the nozzle outlet pressure is 0.2MPa to 2MPa; The closed cycle receiving device is equipped with a sealing ring to perform a cyclic discharging operation; The temperature of calcium carbide particles at the outlet of the cooling rotary kiln is not higher than 200℃; The gas pressure at the outlet of the compressor is not less than 7.8 MPa; The CO2 gas temperature at the turbine inlet is not lower than 600°C, and the CO2 gas temperature at the outlet of the waste heat recovery device is not higher than 150°C; The gas pressure at the outlet of the gas pressure reducing device is not higher than 0.15 MPa; The calcium carbide sprayed by the spray granulation unit is directly sprayed into granules in a molten state. No chemical reaction occurs between the CO2 and the hot calcium carbide in the spraying, cooling, power generation and circulating gas. After heat exchange between the CO2 gas and the calcium carbide particles, the temperature reaches above 600°C, and after compression, it forms a "supercritical fluid", which drives the turbine to rotate and generate electricity.

2. A system for recovering sensible heat from calcium carbide for power generation according to claim 1, characterized in that: The system also includes a control computer. The pressure gauge, gas thermometer and gas valve are all connected to the control computer. Pressure and temperature data are transmitted to the computer in real time, and the opening and closing of the gas valve are automatically controlled.

3. A method for recovering sensible heat from calcium carbide for power generation, comprising a system for recovering sensible heat from calcium carbide for power generation according to any one of claims 1 to 2, characterized in that: The method comprises the following steps: (1) Granulation and cooling of calcium carbide melt: The molten calcium carbide flows out from the calcium carbide discharge port, and is blown by the high-pressure blowing device below it to form calcium carbide particles. The particles are quickly cooled by the low-temperature CO2 gas and fall into the cooling rotary kiln. The calcium carbide particles continuously exchange heat with the low-temperature CO2 gas in the rotary kiln, and then fall into the sealed circulation receiving device and finally enter the material truck for transportation; (2) After the low-temperature CO2 gas undergoes heat exchange with the calcium carbide particles, it is pressurized by a compressor and then measured by a gas thermometer. If the temperature is lower than the threshold, it enters the gas heating device to increase its temperature. If the temperature is higher than the threshold, it directly drives the generator through the turbine to generate electricity. (3) The CO2 gas after passing through the turbine is cooled by a waste heat recovery device, and after the pressure is reduced by a gas pressure reducing device, it enters the cooling and collecting bin for recycling.

Images