Device and method for preparing acetylene through hydrolysis of calcium carbide

Abstract

The invention belongs to the technical field of acetylene generation devices, and provides a device and a method for preparing acetylene through calcium carbide hydrolysis. The device comprises an electric hoist, a calcium carbide hopper, a calcium carbide oscillator, an acetylene generator and a heat exchanger which are sequentially connected, a heat exchange area is connected with a compressor, a separation area is connected with a water ring compressor, a gas holder and a steam condensate delivery pump, and the gas holder is sequentially connected with a reverse water seal, a safe water seal and the acetylene generator. The acetylene generator is respectively connected with the steam condensate delivery pump and the slurry treatment unit, and an overflow pipe and a slag discharge pipe of the acetylene generator are connected with the slurry treatment unit and externally provided with a jacket outer pipe. According to the device, the acetylene yield can be remarkably increased, meanwhile, reaction heat is recycled, low-pressure steam is obtained, meanwhile, wastewater-free discharge is basically achieved, and water consumption is extremely low.

Description

Technical Field

[0001] The present invention relates to the technical field of acetylene generating devices, and in particular to a device and method for preparing acetylene by hydrolyzing calcium carbide. Background Art

[0002] Polyvinyl chloride (PVC) possesses excellent physical, chemical, and mechanical properties and is widely used in industry, agriculture, medicine, and other fields. It is the second most common synthetic resin after polyethylene. With economic development and increasing awareness of environmental protection, the demand for PVC as a high-quality plastic raw material is increasing. Vinyl chloride, the monomer of PVC, can be synthesized by multiple process routes, the most common of which are the calcium carbide process and the ethylene process. my country, as the world's largest PVC producer, primarily produces vinyl chloride using the calcium carbide process. In 2024, the ethylene process accounted for approximately 26% of total PVC production capacity, while the calcium carbide process accounted for approximately 74% of total production capacity.

[0003] The calcium carbide process produces vinyl chloride by reacting calcium carbide with water to generate acetylene gas. Under certain process conditions, acetylene reacts with hydrogen chloride in the presence of a catalyst to produce vinyl chloride. The reaction of calcium carbide with water to produce acetylene gas can be divided into dry and wet processes. The dry acetylene process sprays calcium carbide powder and slightly more water than the theoretical amount onto the powder in a mist form, causing it to hydrolyze and produce acetylene. The resulting carbide slag is a dry powder with a very low water content. The wet acetylene process requires the addition of a large amount of water, resulting in a slurry of carbide slag that needs to be filtered to obtain a filter cake, resulting in high wastewater discharge.

[0004] Currently, most acetylene manufacturers use the wet method, the process is as follows Figure 2 As shown, crushed calcium carbide is placed in a calcium carbide hopper 2. Using an electric hoist 1, it is continuously fed into an acetylene generator 4 via a calcium carbide oscillator 3 through the first and second hoppers. The amount of calcium carbide added is controlled by the oscillator current. The calcium carbide reacts with water in the reactor according to the following reaction equation:

[0005] CaC2+2H2O→C2H2↑+Ca(OH)2+130KJ / mol

[0006] CaO+H2O→Ca(OH) 2+ 63.4 kJ / mol

[0007] The generated crude acetylene gas containing trace dust and the generated water vapor escape from the top of the acetylene generator, enter the cooling tower 8 and the water washing tower 9 through the positive water seal 6, cool the crude acetylene gas to 35-45°C and remove the dust, and then send it to the purification system by the pump 12 for purification treatment (to remove harmful impurities such as S, P, As, etc.); the excess crude acetylene gas is sent to the gas cabinet 10. When the generated crude acetylene gas cannot meet the load of the compressor 12, it is supplemented by the acetylene gas in the gas cabinet 10.

[0008] The heat released by the hydrolysis reaction is removed by continuously adding excess water to the acetylene generator. The resulting carbide slag slurry continuously overflows from the overflow pipe. The concentrated slag slurry and impurities such as ferrosilicon are rake-fed to the bottom of the acetylene generator cone by the stirring rake teeth and intermittently discharged into the slag pool 11 through a pneumatic slag discharge valve. If the pressure within the acetylene generator falls below the specified value due to a feeding failure, the acetylene in the gas tank enters the acetylene generator through the reverse water seal 7 and the safety water seal pipeline to maintain positive pressure and ensure safe production. To prevent overpressure due to blockage of subsequent pipelines or equipment, the acetylene or materials in the reactor are discharged through the safety water seal 5.

[0009] Table 1 Solubility of acetylene gas in water

[0010] Temperature (℃) 70 80 90 100 Solubility (L / L) 0.25 0.15 0.05 ～0

[0011] The solubility of acetylene gas in water is shown in Table 1. Higher reaction temperatures lead to more complete hydrolysis reactions and less acetylene dissolved in water, which improves acetylene yields. However, this increases the load on the cooling and cleaning towers. Lower water levels in the reactor reduce acetylene dissolution losses, but this can lead to incomplete reactions and reduced acetylene yields. Excessive solids content in the carbide slag slurry can also affect slag discharge, resulting in reduced productivity and even safety issues. Taking all factors into consideration, the reaction temperature should be controlled between 80 and 90°C, and the solids content of the carbide slag slurry should be controlled between 18 and 22%. The feed water temperature should be adjusted to meet both the reaction temperature and carbide slag slurry solids content requirements. To balance pressure and ensure overflow of the carbide slag slurry, some acetylene is carried away, resulting in acetylene losses. Existing acetylene production processes maintain a reaction temperature of 85°C and consume 10 to 12 tons of clarified water per ton of carbide hydrolyzed. Therefore, it is urgent to address the high water consumption, high wastewater discharge, low acetylene yield, and wasted reaction heat in this process.

[0012] Chinese patent CN206188747U proposes a device for recycling wastewater containing dissolved acetylene in wet acetylene production. The device collects and reuses the dissolved acetylene in the wastewater, reducing calcium carbide consumption, but does not mention water reuse.

[0013] Chinese patent CN105273760A proposes a wet process for producing acetylene from calcium carbide. The diluted calcium carbide slag slurry overflowing from the acetylene generator is passed through a second desorption tower to recover acetylene gas, and then enters a concentration tank for concentration. The supernatant in the concentration tank is cooled through a cooling tower and a heat exchanger is added to cool it with circulating water before entering the acetylene generator for acetylene generation. The patent only mentions the recycling of water, while removing heat as an unfavorable factor.

[0014] Chinese patent CN106967192A proposes that the carbide slag slurry overflowing from the acetylene generator be discharged into a sedimentation tank for sedimentation, the bottom slurry be discharged for other uses, and the upper clear liquid be cooled and returned to the acetylene generator as water for hydrolysis reaction; the waste water used for acetylene gas dust removal and cooling be returned to the acetylene generator as water for hydrolysis reaction; the hot water coming out of the shell of the converter is heat-exchanged in a heat exchanger and enters the upper part of the steam absorption tower, absorbs the heat evaporated from the hot water tank and then flows into the hot water tank by gravity, and the heat exchanger is used in other processes; the emphasis is on the full utilization of water resources and the removal of reaction heat rather than the effective utilization of heat. Summary of the Invention

[0015] The object of the present invention is to provide a device and method for preparing acetylene by hydrolysis of calcium carbide, which can significantly improve the acetylene yield, while recycling the reaction heat to obtain low-pressure steam, basically achieving no wastewater discharge and extremely low water consumption.

[0016] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0017] The present invention provides an apparatus for preparing acetylene by hydrolyzing calcium carbide, comprising an electric hoist 1, a calcium carbide hopper 2, a calcium carbide oscillator 3, an acetylene generator 4, and a heat exchanger 6, which are connected in sequence. The apparatus also comprises a gas cabinet 8, a water ring compressor 9, a slurry processing unit 10, a steam condensate delivery pump 11, and a compressor 12.

[0018] The heat exchanger 6 includes a heat exchange zone 6a and a separation zone 6b;

[0019] The gas cabinet 8 is connected to the separation area 6b;

[0020] The water ring compressor 9 is connected to the separation zone 6b;

[0021] The slurry processing unit 10 is connected to the acetylene generator 4;

[0022] One end of the steam condensate delivery pump 11 is connected to the acetylene generator 4, and the other end is connected to the separation zone 6b;

[0023] The compressor 12 is connected to the heat exchange area 6a.

[0024] Preferably, the heat exchanger 6 is a high-efficiency shell-and-tube heat exchanger, and the temperature difference between the hot-end material inlet and the cold-end material outlet of the high-efficiency shell-and-tube heat exchanger is ≤5°C, and the temperature difference between the hot-end material outlet and the cold-end material inlet is ≤5°C.

[0025] Preferably, the overflow pipe and the slag discharge pipe of the acetylene generator 4 are provided with jacketed outer pipes.

[0026] Preferably, the acetylene generator 4, the heat exchanger 6 and the outer pipe of the overflow pipe of the acetylene generator 4 are insulated by foamed cement.

[0027] Preferably, the device for preparing acetylene by hydrolysis of calcium carbide further comprises a safety water seal 5 and a reverse water seal 7; the acetylene generator 4 is connected to the safety water seal 5, the reverse water seal 7 and the gas cabinet 8 in sequence.

[0028] The present invention provides a method for preparing acetylene by hydrolyzing calcium carbide, comprising the following steps:

[0029] The calcium carbide placed in the calcium carbide hopper 2 is fed into the acetylene generator 4 through the first and second hoppers by means of an electric hoist 1 and a calcium carbide oscillator 3. The calcium carbide reacts with the water in the acetylene generator 4 to produce crude acetylene gas, saturated water vapor and calcium carbide slag slurry.

[0030] The crude acetylene gas and saturated water vapor are indirectly heat exchanged with cooling water between the heat exchange zone 6a and the heat exchange tubes in the heat exchanger 6 to obtain a first steam-water mixture and a second steam-water mixture;

[0031] The first steam-water mixture is subjected to gas-liquid separation in the separation zone 6b to obtain acetylene gas containing saturated water and condensed water. The acetylene gas containing saturated water is sent to a purification system via a water ring compressor 9, or the acetylene gas containing saturated water enters a gas cabinet 8, and the condensed water is returned to the acetylene generator 4 via a steam condensate delivery pump 11.

[0032] The second steam-water mixture is fed into the compressor 12 for pressurization to obtain low-pressure steam;

[0033] The carbide slag slurry exchanges heat with the cooling water of the jacket outer tube in countercurrent flow and is sent to the slurry treatment unit 10 to obtain the carbide slag filter cake and filtrate, and the filtrate is sent to the acetylene generator 4 for reuse.

[0034] Preferably, the content of CaC2 in the calcium carbide is 80.6wt%, the content of CaO is 10wt%, and the content of impurities is 9.4wt%; the temperature of the hydrolysis reaction is 95-110°C, and the gauge pressure is 0.008-0.012MPa;

[0035] The temperature of the crude acetylene gas and saturated water vapor is 95-105°C, and the gauge pressure is 0.01-0.02 MPa; the temperature of the carbide slag slurry is 98-100°C.

[0036] Preferably, the temperature of the first soda-water mixture is ≤40°C; the temperature of the second soda-water mixture is 90-100°C, and the gauge pressure is -0.01--0.005MPa.

[0037] Preferably, the temperature of the low-pressure steam is 120-150° C., and the gauge pressure is 0.1-0.4 MPa.

[0038] Preferably, the water content of the carbide slag filter cake is 35-45wt%; and the cooling water of the outer tube of the jacket is heated to 80-90°C.

[0039] Beneficial effects of the present invention:

[0040] The acetylene generator of the present invention retains the acetylene generator, safety water seal, reverse water seal, and gas holder of the existing process, eliminating the positive water seal, cooling tower, and cleaning tower, and adding a heat exchanger. The acetylene generator and heat exchanger are insulated, and the carbide slag slurry overflow pipe and slag discharge pipe are jacketed with outer pipes, which are also insulated to improve thermal energy utilization.

[0041] Through the acetylene production device and process of the present invention, acetylene can be obtained in high yield, steam can be co-produced, and heat can be fully recovered. Except that the calcium carbide slag filter cake contains 35-40% water, there is no wastewater discharge in the whole process, the water demand is extremely low, and the environmental and economic benefits are significant. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a diagram of an apparatus for producing acetylene by a wet process according to Example 1 of the present invention, wherein 1 is an electric hoist, 2 is a calcium carbide hopper, 3 is a calcium carbide oscillator, 4 is an acetylene generator, 5 is a safety water seal, 6a is a heat exchanger, 6b is a separator, 7 is a reverse water seal, 8 is a gas cabinet, 9 is a water ring compressor, 10 is a slurry processing unit, 11 is a steam condensate delivery pump, and 12 is a compressor;

[0043] Figure 2 This is a diagram of the device for producing acetylene using the traditional wet process, where 1 is an electric hoist, 2 is a calcium carbide hopper, 3 is a calcium carbide oscillator, 4 is an acetylene generator, 5 is a safety water seal, 6 is a positive water seal, 7 is a reverse water seal, 8 is a cooling tower, 9 is a water scrubber, 10 is a gas holder, 11 is a slag pool, and 12 is a water ring pump. DETAILED DESCRIPTION

[0044] The present invention provides an apparatus for preparing acetylene by hydrolyzing calcium carbide, comprising an electric hoist 1, a calcium carbide hopper 2, a calcium carbide oscillator 3, an acetylene generator 4, and a heat exchanger 6, which are connected in sequence. The apparatus also comprises a safety water seal 5, a reverse water seal 7, a gas cabinet 8, a water ring compressor 9, a slurry processing unit 10, a steam condensate delivery pump 11, and a compressor 12.

[0045] The heat exchanger 6 includes a heat exchange zone 6a and a separation zone 6b;

[0046] The gas cabinet 8 is connected to the separation area 6b;

[0047] The water ring compressor 9 is connected to the separation zone 6b;

[0048] The slurry processing unit 10 is connected to the acetylene generator 4;

[0049] One end of the steam condensate delivery pump 11 is connected to the acetylene generator 4, and the other end is connected to the separation zone 6b;

[0050] The compressor 12 is connected to the heat exchange area 6a.

[0051] The present invention preferably connects the electric hoist 1, the calcium carbide hopper 2, the calcium carbide oscillator 3, the acetylene generator 4, and the heat exchanger 6 in sequence.

[0052] In the present invention, the heat exchanger 6 is preferably a high-efficiency shell-and-tube heat exchanger, which can avoid the problem of heat exchanger blockage caused by a small amount of dust in the cooled materials (acetylene and water vapor).

[0053] In the present invention, the heat exchanger 6 is preferably vertical, so that the water vapor in the cooled material (acetylene and water vapor) is condensed into water, which flows from top to bottom by gravity and flushes the dust into the separation area. Therefore, this heat exchanger can simultaneously perform cooling and water washing functions.

[0054] In the present invention, the temperature difference between the hot-end material inlet and the cold-end material outlet of the heat exchanger 6 is preferably ≤5°C, and the temperature difference between the hot-end material outlet and the cold-end material inlet is preferably ≤5°C; the present invention has no special restrictions on the type of heat exchanger 6, as long as the temperature difference between the hot-end material inlet and the cold-end material outlet of the heat exchanger 6 is ≤5°C, and the temperature difference between the hot-end material outlet and the cold-end material inlet is ≤5°C.

[0055] In the present invention, the heat exchanger 6 is preferably divided into a heat exchange zone 6a and a separation zone 6b.

[0056] In the present invention, the crude acetylene gas containing trace dust and the generated saturated water vapor in the heat exchange zone 6a flow from top to bottom and indirectly exchange heat with the cooling water between the heat exchange tubes from bottom to top.

[0057] In the present invention, the separation zone 6b is responsible for separating the acetylene gas saturated with water and the condensed water containing acetylene in the first steam-water mixture.

[0058] In the present invention, the gas cabinet 8 is preferably connected to the separation zone 6b, and the water ring compressor 9 is preferably connected to the separation zone 6b.

[0059] In the present invention, the gas tank 8 is connected to the separation zone 6b, and the water ring compressor 9 is connected to the separation zone 6b in order to send the saturated water-containing acetylene gas obtained by gas-liquid separation of the first steam-water mixture into the water ring compressor 9 or the gas tank 8 for subsequent treatment. Specifically, the separation zone 6b is connected to the water ring compressor 9, and the saturated water-containing acetylene gas is sent to the purification system through the water ring compressor 9 for purification treatment to obtain product acetylene gas; the separation zone 6b is also connected to the gas tank 8 in order to supplement it with the acetylene gas stored in the gas tank 8 when the saturated water-containing acetylene gas sent to the water ring compressor 9 cannot meet the load of the water ring compressor 9.

[0060] In the present invention, the slurry processing unit 10 is preferably connected to the acetylene generator 4 .

[0061] In the present invention, the slurry processing unit preferably includes a filter press and a slurry tank.

[0062] In the present invention, the overflow pipe and slag discharge pipe of the acetylene generator 4 are preferably equipped with an external jacketed outer pipe, and cooling water is introduced into the jacketed outer pipe. The amount of water is equal to the amount of water required for the hydrolysis of calcium carbide to generate calcium hydroxide plus the amount of water contained in the calcium carbide slag slurry plus the amount of water contained in the acetylene entering the water ring compressor 9 or the gas tank 8. The amount of water comes from the water contained in the calcium carbide slag slurry and a small amount of supplementary water. These waters are countercurrently heat exchanged with the calcium carbide slag slurry and are heated to 80-90°C.

[0063] In the present invention, the carbide slag slurry generated in the acetylene generator 4 is subjected to countercurrent heat exchange with the cooling water of the jacket outer tube. The cooled carbide slag slurry enters the slurry treatment unit 10 and is filtered by a filter press to obtain a carbide slag filter cake and a filtrate. The filtrate is reused for acetylene generation, and the carbide slag filter cake is sent to the slag pool.

[0064] In the present invention, the acetylene generator 4 and the heat exchanger 6 as well as the outer pipe of the overflow pipe of the acetylene generator 4 are preferably insulated by foamed cement to improve the utilization rate of thermal energy; foamed cement is water-resistant, corrosion-resistant, and high-temperature resistant, and the material is cheap and suitable for use as an insulation material; in addition, the length of the outer jacket of the calcium carbide slurry overflow pipe to the slurry treatment unit can be appropriately extended to meet the heat exchange area required for indirect heat exchange.

[0065] In the present invention, the slurry treatment unit 10 is connected to the acetylene generator 4 in order to, on the one hand, send the carbide slurry in the acetylene generator 4 into the slurry treatment unit 10 through the overflow pipe and the slag discharge pipe, and on the other hand, to reuse the filtrate obtained from the slurry treatment unit for acetylene generation.

[0066] In the present invention, one end of the steam condensate delivery pump 11 is preferably connected to the acetylene generator 4, and the other end is connected to the separation zone 6b.

[0067] In the present invention, one end of the steam condensate delivery pump 11 is connected to the acetylene generator 4, and the other end is connected to the separation zone 6b in order to return the condensed water obtained by the gas-liquid separation of the first steam-water mixture to the acetylene generator 4 via the steam condensate delivery pump 11 and reuse it for acetylene generation; the condensed water contains a small amount of acetylene gas, which is returned to the acetylene generator for circulation without loss or impact.

[0068] In the present invention, the compressor 12 is preferably connected to the heat exchange area 6a.

[0069] In the present invention, the heat exchange zone 6 a is connected to the compressor 12 in order to transport the second steam-water mixture into the compressor 12 .

[0070] In the present invention, the compressor 12 is preferably a one-stage spiral steam compressor; if steam with higher temperature and gauge pressure is required, a multi-stage spiral steam compressor can be used; the compressor 12 can provide compression energy and kinetic energy at the same time, and more effectively provide thermal energy for low-pressure steam.

[0071] In the present invention, the outlet steam temperature of the compressor 12 is preferably 120-150° C., and the outlet gauge pressure is preferably controlled at 0.1-0.4 MPa.

[0072] The present invention preferably connects the gas cabinet 8 to the reverse water seal 7 , the safety water seal 5 , and the acetylene generator 4 in sequence.

[0073] In the present invention, the gas tank 8 is connected to the reverse water seal 7, the safety water seal 5, and the acetylene generator 4 in sequence so that when the internal gauge pressure of the acetylene generator 4 is lower than the specified value due to a feeding failure, the acetylene in the gas tank 8 can enter the acetylene generator 4 through the reverse water seal 7 and the safety water seal 5 pipeline to maintain positive pressure and ensure safe production; in order to prevent overpressure due to blockage of subsequent pipelines and equipment, the acetylene or material in the acetylene generator 4 enters the safety water seal 5 and is discharged.

[0074] The present invention provides a method for preparing acetylene by hydrolyzing calcium carbide, comprising the following steps:

[0075] The calcium carbide placed in the calcium carbide hopper 2 is fed into the acetylene generator 4 through the first and second hoppers by means of an electric hoist 1 and a calcium carbide oscillator 3. The calcium carbide reacts with the water in the acetylene generator 4 to produce crude acetylene gas, saturated water vapor and calcium carbide slag slurry.

[0076] The crude acetylene gas and saturated water vapor are indirectly heat exchanged with cooling water between the heat exchange zone 6a and the heat exchange tubes in the heat exchanger 6 to obtain a first steam-water mixture and a second steam-water mixture;

[0077] The first steam-water mixture is subjected to gas-liquid separation in the separation zone 6b to obtain acetylene gas containing saturated water and condensed water. The saturated water and acetylene gas are sent to a purification system via a water ring compressor 9, or the saturated water acetylene gas enters a gas cabinet 8, and the condensed water is returned to the acetylene generator 4 via a steam condensate delivery pump 11.

[0078] The second steam-water mixture is fed into the compressor 12 for pressurization to obtain low-pressure steam;

[0079] The carbide slag slurry exchanges heat with the cooling water of the jacket outer tube in countercurrent, and is sent to the slurry treatment unit 10 to obtain the carbide slag filter cake and filtrate, and the filtrate is sent to the acetylene generator 4 for reuse.

[0080] In the present invention, unless otherwise specified, the raw materials required for preparation are all commercially available products well known to those skilled in the art.

[0081] The present invention preferably places the crushed calcium carbide into the calcium carbide hopper 2, and uses an electric hoist to continuously add it into the acetylene generator 4 through the first and second hoppers and the calcium carbide oscillator 3. The amount of addition is controlled by the current of the calcium carbide oscillator 3. The calcium carbide and water undergo a hydrolysis reaction in the acetylene generator 4 to obtain crude acetylene gas, saturated water vapor and calcium carbide slag slurry.

[0082] In the present invention, the content of CaC2 in the calcium carbide is preferably 80.6wt%, the content of CaO is preferably 10wt%, and the content of impurities is preferably 9.4wt%.

[0083] In the present invention, the temperature of the hydrolysis reaction is preferably 95 to 110° C., more preferably 105 to 110° C., and the gauge pressure is preferably 0.008 to 0.012 MPa, more preferably 0.01 to 0.012 MPa.

[0084] In the present invention, the temperature of the crude acetylene gas and saturated water vapor is preferably 95-105°C, more preferably 100°C, and the gauge pressure is preferably 0.01-0.02MPa, more preferably 0.015MPa; the formation of such a steam-water mixture with a high water vapor content greatly reduces the risk of explosion and improves safety and reliability. It not only meets the pressure level of the original equipment and ensures the complete hydrolysis reaction of calcium carbide, but also can obtain more water vapor.

[0085] In the present invention, the temperature of the carbide slag slurry is preferably 98-100°C.

[0086] In the present invention, the crude acetylene gas and saturated water vapor are preferably fed into the heat exchange zone 6a for indirect heat exchange with cooling water between the heat exchange tubes to obtain a first steam-water mixture and a second steam-water mixture.

[0087] In the present invention, the crude acetylene gas and saturated water vapor enter heat exchange zone 6a and flow downward, indirectly exchanging heat with cooling water flowing between the heat exchange tubes from bottom to top. The acetylene gas is cooled and the saturated water vapor is condensed, producing a first steam-water mixture. The cooling water between the heat exchange tubes is heated until it vaporizes, producing a second steam-water mixture. In the present invention, the temperature of the first steam-water mixture is preferably ≤40°C, more preferably 30°C.

[0088] In the present invention, the cooling water between the heat exchange tubes is desalted water, and its replenishment amount is equal to the amount of steam delivered by the compressor 12.

[0089] In the present invention, the temperature of the second soda-water mixture is preferably 90 to 100° C., more preferably 97 to 100° C., and the gauge pressure is preferably -0.01 to -0.005 MPa, more preferably -0.01 MPa.

[0090] In the present invention, the first steam-water mixture is preferably subjected to gas-liquid separation in the separation zone 6b to obtain acetylene gas containing saturated water and condensed water.

[0091] In the present invention, the flow rate of the acetylene gas containing saturated water is preferably 1750-1950m 3 / h (0.01MPaG), more preferably 1850m 3 / h (0.01MPaG); the condensed water contains a small amount of acetylene gas, and the flow rate of the condensed water is preferably 2.5 to 2.8m 3 / h, more preferably 2.65m 3 / h.

[0092] In the present invention, the second steam-water mixture is preferably pressurized by a compressor 12 to obtain low-pressure steam.

[0093] In the present invention, the temperature of the low-pressure steam is preferably 120-150° C., more preferably 140° C., and the gauge pressure is preferably 0.1-0.4 MPa, more preferably 0.25-0.35 MPa.

[0094] In the present invention, the flow rate of the low-pressure steam is preferably 1.9 to 2.3 tons / h, more preferably 2.2 tons / h.

[0095] The present invention preferably carries out a stirring rake to the cone bottom of the acetylene generator 4 by rakes containing the carbide slag slurry and impurities such as ferrosilicon that continuously overflow from the overflow pipe. The carbide slag slurry is subjected to countercurrent heat exchange with the cooling water of the jacket outer tube. The carbide slag slurry is cooled from high temperature to room temperature and is intermittently discharged into the slag pool through a pneumatic slag discharge valve. After filtration, the carbide slag filter cake and filtrate are obtained.

[0096] In the present invention, the overflow rate of the carbide slag slurry is preferably 44 to 46 tons / h, and more preferably 45 tons / h.

[0097] In the present invention, the amount of cooling water in the jacket outer tube preferably includes the amount of water required for the hydrolysis of calcium carbide to generate calcium hydroxide, the amount of water contained in the calcium carbide slag slurry, and the amount of water contained in the acetylene entering the water ring compressor or gas holder; the water flowing through the jacket outer tube added to the overflow pipe and the slag discharge pipe of the acetylene generator adopts a countercurrent operation, and the water flowing through the jacket outer tube added to the overflow pipe and the slag discharge pipe is heated by the calcium carbide slag slurry and then enters the acetylene generator, maintaining the liquid level in the generator basically constant, thereby realizing the maximum utilization of the reaction heat.

[0098] In the present invention, the flow rate of the cooling water in the jacket outer tube is preferably 38 to 42 m / s. 3 / h, more preferably 40m 3 / h; the cooling water of the jacket outer tube is preferably heated to 80-90°C, and further preferably heated to 85°C; if the temperature is lower than 80°C, the heat utilization rate is low; if the temperature is higher than 90°C, the requirements for insulation materials are too high.

[0099] In the present invention, the discharge rate of the carbide slag filter cake is preferably 12 to 13 tons / h, more preferably 12.5 tons / h.

[0100] In the present invention, the water content of the carbide slag filter cake is preferably 35-45%, more preferably 35-40%.

[0101] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0102] Example 1

[0103] It uses five-layer baffles and five-layer tooth rakes with a diameter of φ2.8 and a volume of 28m 3 Large generator with a PVC production capacity of 40,000 tons / year.

[0104] Use Figure 1 The device shown produces acetylene. Crushed calcium carbide (CaC2 is 80.6%, CaO is about 10%, and other impurities are 9.4%) is placed into the calcium carbide hopper 2 at a rate of 6.6 tons / h. It is then continuously added to the acetylene generator 4 via the first and second hoppers using an electric hoist 1 and a calcium carbide oscillator 3. The amount added is controlled by the current of the calcium carbide oscillator 3. The calcium carbide and water undergo a hydrolysis reaction in the acetylene generator 4 at 105°C and 0.01MPa. The generated crude acetylene gas and saturated water vapor (temperature is 100°C, gauge pressure is 0.01MPa) escape from the top of the acetylene generator 4 and enter the heat exchange zone 6a of the heat exchanger 6. At the same time, the generated calcium carbide slag slurry (temperature is 99°C) continuously overflows from the overflow pipe at a rate of 45 tons / h.

[0105] After entering the heat exchange zone 6a, the crude acetylene gas and the generated saturated water vapor flow from top to bottom, indirectly exchanging heat with the cooling water between the heat exchange tubes (the cooling water between the heat exchange tubes is desalted water, and its replenishment amount is equal to the amount of low-pressure steam delivered by the compressor 12). The acetylene gas is cooled and the saturated water vapor is condensed to obtain a first steam-water mixture at 30°C. The cooling water between the heat exchange tubes is heated to produce a second steam-water mixture at approximately 98.5°C, which vaporizes at -0.01 MPa.

[0106] The first steam-water mixture carries dust into the separation zone 6b, and the separated crude acetylene gas containing saturated water is 1848m 3 / h (0.01MPaG), the temperature is 30℃, the gauge pressure is 0.01MPa, and it is sent to the purification system for treatment through the water ring compressor 9; the flow rate of the separated condensed water is 2.65m 3 / h, and returns to the acetylene generator 4 through the steam condensate delivery pump 11 and is reused for acetylene generation.

[0107] The second steam-water mixture is pressurized to 0.4 MPa and its temperature is raised to 150° C. by compressor 12 and provided to users as low-pressure steam. The outlet flow meter of compressor 12 shows a flow rate of 2.2 tons / h.

[0108] The carbide slag slurry with a temperature of 98-100℃ continuously overflows from the overflow pipe at a rate of 45 tons / h. Together with impurities such as ferrosilicon, it is rake-fed to the bottom of the acetylene generator cone 4 and discharged intermittently through the pneumatic slag discharge valve. The overflow pipe and slag discharge pipe are equipped with a jacketed outer pipe, which is also insulated. The flow rate in the jacketed outer pipe is 40m 3 / h of cooling water, including the water required for the hydrolysis of calcium carbide to produce calcium hydroxide, the water contained in the carbide slag slurry, and the water contained in the acetylene entering the water ring compressor or gas tank. This water exchanges heat with the carbide slag slurry in countercurrent flow, heating it to 85°C. The carbide slag slurry is cooled from high temperature to room temperature before entering the slurry treatment unit, producing a carbide slag filter cake with a moisture content of 40%, with a discharge rate of 12.5 tons / h.

[0109] 1) Material balance was performed on Example 1, specifically:

[0110] Reaction formula 1: CaC2+2H2O→C2H2↑+Ca(OH)2+130kj / mol;

[0111] Calculated based on the mass of calcium carbide as 1 ton, the mass of CaC2 is 1000×80.6%=806 kg;

[0112] The mass of water required is (806 / 64)×36=453.375Kg;

[0113] The mass of acetylene gas produced is (806 / 64)×26=324.4375Kg;

[0114] The mass of calcium hydroxide produced is (806 / 64)×74=931.9375Kg;

[0115] The heat generated is (806 / 64)×1000×130=1637187.5KJ;

[0116] Reaction formula 2: CaO + H2O → Ca(OH)2 + 63.4 kJ / mol;

[0117] Taking the mass of calcium carbide as 1 ton, the mass of CaO is 1000×10%=100 kg;

[0118] The mass of water required is (100 / 56)×18=32.14Kg;

[0119] The mass of calcium hydroxide produced is (100 / 56)×74=132.14Kg;

[0120] The heat generated is (100 / 56)×1000×63.4=113214.29KJ;

[0121] In addition, if the mass of calcium carbide is 1 ton, the mass of other impurities is 1000×9.4%=94Kg;

[0122] To summarize the above data, taking the mass of calcium carbide as 1 ton, it is calculated that the mass of acetylene gas produced by 1 ton of calcium carbide is 324.44 kg (to two decimal places, the same below), the mass of water consumed in the hydrolysis reaction is 485.52 kg, and the mass of calcium carbide slag (Ca(OH)2 and impurities) produced is 1158.08 kg, and a total of 1750401.79 kJ of heat is generated.

[0123] 2) Carry out water balance, specifically:

[0124] The mass of water consumed by the hydrolysis reaction of 1 ton of calcium carbide is W1, which is 485.52 kg (453.375 kg + 32.14 kg).

[0125] Since the solid content of carbide slag slurry is 20%, the mass of water in the carbide slag slurry produced by 1 ton of carbide is (1158.08 / 20%)×80%=4632.32Kg;

[0126] Since the water content in the carbide slag filter cake is 40%, the mass W2 of water in the carbide slag filter cake produced by 1 t of carbide is 1158.08×40 / (100-40)=772 kg.

[0127] It is known that the saturated vapor pressure of water at 30°C is 0.0043 MPa. The gauge pressure of the separation zone 6b in Example 1 is 0.01 MPa. At this time, the absolute pressure is 0.1113 MPa (0.01 MPa + standard atmospheric pressure 0.101325 MPa, rounded to four decimal places). The partial pressure ratio (molar ratio) of the saturated water in the crude acetylene gas containing saturated water separated from the separation zone 6b is 0.0043 / (0.1113-0.0043)=0.0402, and the mass W3 of the saturated water is 806×0.0402×18 / 64=9 kg. (Note: The saturated vapor pressure of water at 0°C is 0.004255 MPa. For convenience, it is calculated as 0.0043. The partial pressure ratio of saturated water in crude acetylene gas is 0.004255 / (0.1113-0.004255)=0.03975. Based on 0.04, W3 is 806×0.04×18 / 64=9 kg, which has no effect on the actual result.)

[0128] The mass of water that needs to be replenished during the process includes clarified water and desalted water. The clarified water that needs to be replenished is the cooling water introduced into the outer pipe of the jacket, with a mass W = W1 + W2 + W3 = 1267 kg. The mass of desalted water that needs to be replenished is equal to the amount of low-pressure steam generated. See the heat balance section for details.

[0129] 3) Perform thermal balance calculation, specifically:

[0130] The specific heat capacity of calcium carbide is known to be 1.1 kJ / (kg·K). When 1 ton of calcium carbide is heated from an ambient temperature of 25°C to 100°C, the heat Q1 consumed is: 1000×(100-25)×1.1=82500 kJ;

[0131] Given that the specific heat capacity of water is 4.2 kJ / (kg·K), the heat Q2 carried away by the carbide slag slurry is: 4632.32×(100-25)×4.2=1459180.8 kJ;

[0132] The specific heat capacity of carbide slag is known to be 0.963 kJ / (kg·℃). The heat Q3 carried away by carbide slag is: 1158.08×(100-25)×0.963=83642.33 kJ;

[0133] The heat Q4 obtained by heat exchange between carbide slag slurry filtrate and make-up water and carbide slag slurry is: (4632.32+485.52+9)×(85-25)×4.2=1291963.68kJ (recycled);

[0134] It is known that acetylene Cp = 1.64KJ / (kg·K), and the heat Q5 carried away by acetylene gas is: 327.44×(30-25)×1.64=2608.91kJ,

[0135] The heat Q6 required to replenish water to reach the reaction temperature is: (4632.32+485.52+9)×(100-85)×4.2=322990.92kJ

[0136] The total heat consumed by 1 ton of calcium carbide through the process of Example 1 is Q = Q1 + Q2 + Q3 + Q5 + Q6 - Q4 = 658959.28 kJ

[0137] Therefore, the heat that 1 t of calcium carbide can provide for generating low-pressure steam through the process of Example 1 is 1750402 kJ (generated heat) - 658959.3 = 1091442.7 kJ, and the final amount of low-pressure steam generated is 1091442.7 / {(100-30)×4.2+2256}=428 kg, where 4.2 and 2256 are the specific heat capacity and vaporization heat of water respectively, and 30 is the temperature in the separator (°C).

[0138] Comparative Example 1

[0139] It uses five-layer baffles and five-layer tooth rakes with a diameter of φ2.8 and a volume of 28m 3 Large generator with a PVC production capacity of 40,000 tons / year.

[0140] Use Figure 2 The device shown produces acetylene. Crushed calcium carbide (CaC2 is 80.6%, CaO is about 10%, and other impurities are 9.4%) is put into the calcium carbide hopper 2 at a rate of 6.6 tons / h. It is continuously added to the generator 4 through the first and second hoppers using an electric hoist 1 and a calcium carbide oscillator 3. The amount added is controlled by the oscillator current. The calcium carbide and water undergo a hydrolysis reaction at 85°C and 0.01MPa in the acetylene reactor 4. The generated crude acetylene gas and water vapor escape from the top of the acetylene generator 4 and enter the cooling tower 8 and the water washing tower 9 through the bottom of the positive water seal 6.

[0141] In the tower, about 30 tons / h of spray water below 25℃ is used for countercurrent heat transfer with acetylene gas to cool the crude acetylene gas to ≤30℃ and remove the dust to obtain 1755~1842m 3 Crude acetylene gas at a rate of 0.01 MPaG / h is fed into the purification system by a water ring compressor 12 for purification (removal of harmful impurities such as S, P, and As). Spray water (25°C) from cooling tower 8 and water scrubber 9 is fed into the acetylene generator for acetylene production. The heat released by the hydrolysis reaction is removed by continuously adding excess water to the generator.

[0142] The generated carbide slag slurry continuously overflows from the overflow pipe and, along with impurities such as acetylene and ferrosilicon, is rake-fed to the bottom of the generator cone 4 via the stirring rake teeth. It is then intermittently discharged into the slag pool via a pneumatic slag discharge valve. The solids content of the carbide slag slurry is controlled at 14.3% (to achieve a solids content of 20%, the water temperature entering the generator must be significantly lowered). The carbide slag slurry is filtered through a filter press, producing 12-13 tons / hour of carbide slag filter cake with a water content of 35-40% and 39-40 tons / hour of filtrate. After natural cooling, the filtrate is partially recycled into acetylene generation. The feed water temperature must be adjusted to meet both the reaction temperature and the carbide slag slurry solids content requirements. Balancing the pressure ensures the carbide slag slurry overflows, but this also carries away some acetylene, resulting in losses.

[0143] 6.6 tons / h of calcium carbide hydrolysis releases 11,552,653.2 kJ / h of heat. Assuming the water temperature entering the generator (ambient temperature) is 25°C, 45.86 tons / h of water must be added to maintain a reaction temperature of 85°C. Cooling tower 8 and water scrubber 9 each produce 30 tons / h of water, but only 15.86 tons / h of filtrate can be reused, leaving 23-24 tons / h of filtrate for discharge.

[0144] Data Analysis

[0145] The actual addition amount of calcium carbide is 6.6 tons / h. Under this condition, the material balance data and thermal data of Example 1 and Comparative Example 1 are calculated. The results are shown in Table 2.

[0146] Table 2 Comparison of material balance and thermal data between Example 1 and Comparative Example 1

[0147]

[0148] As can be seen from Table 2, compared with the production of acetylene using the traditional wet process in Comparative Example 1, the technology and apparatus of the present invention can increase the yield of acetylene, while recycling the reaction heat to obtain low-pressure steam, and basically achieve no wastewater discharge, extremely low water consumption, and significant dual-carbon effect.

[0149] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A device for preparing acetylene by hydrolysis of calcium carbide, characterized in that: The device comprises an electric hoist (1), a calcium carbide hopper (2), a calcium carbide oscillator (3), an acetylene generator (4) and a heat exchanger (6) which are connected in sequence, and further comprises a gas cabinet (8), a water ring compressor (9), a slurry processing unit (10), a steam condensate delivery pump (11) and a compressor (12); The heat exchanger (6) comprises a heat exchange zone (6a) and a separation zone (6b); The gas cabinet (8) is connected to the separation zone (6b); The water ring compressor (9) is connected to the separation zone (6b); The slurry processing unit (10) is connected to the acetylene generator (4); One end of the steam condensate delivery pump (11) is connected to the acetylene generator (4), and the other end is connected to the separation zone (6b); The compressor (12) is connected to the heat exchange area (6a).

2. The device according to claim 1, characterized in that The heat exchanger (6) is a high-efficiency shell-and-tube heat exchanger, wherein the temperature difference between the hot end material inlet and the cold end material outlet of the high-efficiency shell-and-tube heat exchanger is ≤5°C, and the temperature difference between the hot end material outlet and the cold end material inlet is ≤5°C.

3. The device according to claim 1, characterized in that The overflow pipe and the slag discharge pipe of the acetylene generator (4) are provided with a jacketed outer pipe.

4. The device according to claim 3, characterized in that The acetylene generator (4), the heat exchanger (6) and the outer pipe of the overflow pipe of the acetylene generator (4) are insulated by foaming cement.

5. The device according to claim 1, characterized in that The device for preparing acetylene by hydrolysis of calcium carbide further comprises a safety water seal (5) and a reverse water seal (7); the acetylene generator (4) is connected to the safety water seal (5), the reverse water seal (7) and the gas cabinet (8) in sequence.

6. A method for preparing acetylene by hydrolysis of calcium carbide, characterized in that: The following steps are involved: The calcium carbide placed in the calcium carbide hopper (2) is fed into the acetylene generator (4) via the electric hoist (1) through the first and second hoppers and the calcium carbide oscillator (3). The calcium carbide undergoes a hydrolysis reaction with the water in the acetylene generator (4) to obtain crude acetylene gas, saturated water vapor and calcium carbide slag slurry. The crude acetylene gas and saturated water vapor are indirectly heat exchanged with cooling water between the heat exchange tubes in the heat exchange zone (6a) of the heat exchanger (6) to obtain a first steam-water mixture and a second steam-water mixture; The first steam-water mixture is subjected to gas-liquid separation in the separation zone (6b) to obtain acetylene gas containing saturated water and condensed water. The acetylene gas containing saturated water is sent to a purification system via a water ring compressor (9), or the acetylene gas containing saturated water enters a gas cabinet (8), and the condensed water is returned to the acetylene generator (4) via a steam condensate delivery pump (11); The second steam-water mixture is fed into a compressor (12) for pressurization to obtain low-pressure steam; The carbide slag slurry is subjected to countercurrent heat exchange with the cooling water of the jacket outer tube and is sent to the slurry treatment unit (10) to obtain the carbide slag filter cake and filtrate, and the filtrate is sent to the acetylene generator (4) for reuse.

7. The method according to claim 6, characterized in that The content of CaC2 in the calcium carbide is 80.6wt%, the content of CaO is 10wt%, and the content of impurities is 9.4wt%; the temperature of the hydrolysis reaction is 95-110°C, and the gauge pressure is 0.008-0.012MPa; The temperature of the crude acetylene gas and saturated water vapor is 95-105° C., and the gauge pressure is 0.01-0.02 MPa; the temperature of the carbide slag slurry is 98-100° C.

8. The method according to claim 6, characterized in that The temperature of the first soda-water mixture is ≤40° C.; the temperature of the second soda-water mixture is 90-100° C., and the gauge pressure is -0.01--0.005 MPa.

9. The method according to claim 6, characterized in that The temperature of the low-pressure steam is 120-150° C., and the gauge pressure is 0.1-0.4 MPa.

10. The method according to claim 6, characterized in that The water content of the carbide slag filter cake is 35-45wt%; the cooling water of the outer tube of the jacket is heated to 80-90°C.

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