CN1884241A - Process for producing vinyl chloride by acetylene method and dedicated device for realizing same - Google Patents
Process for producing vinyl chloride by acetylene method and dedicated device for realizing same Download PDFInfo
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- CN1884241A CN1884241A CN 200610098607 CN200610098607A CN1884241A CN 1884241 A CN1884241 A CN 1884241A CN 200610098607 CN200610098607 CN 200610098607 CN 200610098607 A CN200610098607 A CN 200610098607A CN 1884241 A CN1884241 A CN 1884241A
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Abstract
The invention discloses a new method of chloroethylene through acetylene method and specific equipment, which comprises the following steps: disposing raw material gas strictly; reacting two-segment compensation; recycling heptane; cooling; radiating; providing specific catalyst and reactor to synthesize chloroethylene; disposing effluent with mercury to obtain high-purity chloroethylene monomer.
Description
Technical Field
The invention relates to a method for producing chloroethylene, in particular to a novel method for producing chloroethylene by an acetylene method and special equipment for realizing the method.
Background
Chloroethylene is a colorless gas slightly soluble in water, twice as heavy as air at normal temperature, has anesthetic fragrance, and has molecular formula of C2H3Cl, molecular weight 62.5, boiling point-13.9 ℃, critical temperature 142 ℃, critical pressure 5.22MPa (52.22 atm), so that liquid vinyl chloride can be obtained by slightly pressurizing it. It was first discovered by the french chemist Reqnauk in 1835. Because it is the main raw material for producing polyvinyl chloride, i.e. polyvinyl chloride is polymerized by vinyl chloride. Therefore, the rapid development of polyvinyl chloride production has been accompanied by a rapid development. The world production capacity of vinyl chloride has exceeded the statistics in 20043700 ten thousand tons.
The production methods of vinyl chloride are many, and the general industrial production methods of vinyl chloride mainly include:
1. an acetylene method:
the acetylene method is that chlorine and hydrogen obtained by electrolyzing saline solution are treated by combustion synthesis reaction, cooling purification and the like to obtain refined hydrogen chloride, then the refined hydrogen chloride reacts with calcium carbide acetylene, namely calcium carbide reacts with water to generate crude acetylene, and then the crude acetylene is treated by cleaning, neutralization, drying and the like to obtain refined acetylene; or the acetylene (natural gas or methane) is partially oxidized and cracked by a natural gas method to obtain dilute acetylene, and then the dilute acetylene is quenched, compressed, concentrated, rectified and the like to obtain the refined acetylene. The crude chloroethylene is generated through addition reaction under the action of mercuric chloride catalyst, and then the chloroethylene monomer is obtained through refining after the treatments of water washing, alkali washing, compression, rectification and the like. The main chemical reaction equation is as follows:
the method has the advantages of easily available raw materials, simple production operation, low investment, high energy consumption, difficult carbide slag treatment and high environmental pollution. The natural gas acetylene has relatively high cost and relatively low pollution because the natural gas is relatively expensive.
2. Combination method:
with the development of the petroleum industry, it has appeared that in the manufacture of vinyl chloride a part of the carbon originates from petroleum ethylene,then the method is combined with acetylene by calcium carbide method (or acetylene by natural gas method) to obtain chloroethylene, and the method is called a combined method. The process is to electrolyze petroleum ethylene and Cl obtained from common salt2Reacting to generate 1-2-dichloroethane, refining and cracking to obtain HCl and C2H3CL and HCL are subjected to addition reaction with calcium carbide-process acetylene (or natural gas-process acetylene), and the obtained crude chloroethylene is purified and refined to obtain refined chloroethylene. The main chemical reaction equation is as follows:
the method is slightly better than the calcium carbide acetylene method, obtains partial chloroethylene, recycles hydrogen chloride, reduces partial energy consumption and reduces some pollution.
3. Ethylene oxychlorination process:
the ethylene oxychlorination method is a method for preparing vinyl chloride by cracking petroleum to obtain ethylene and then using the ethylene, chlorine, oxygen and hydrogen chloride, and has the following main chemical reaction equation:
(1) direct chlorination of ethylene: ethylene is chlorinated in the liquid phase to produce 1, 2-dichloroethane:
(2) cracking of dichloroethane: the ethylene dichloride is cracked at about 500 ℃ to produce vinyl chloride and hydrogen chloride:
(3) oxychlorination of ethylene: ethylene is subjected to oxychlorination reaction with oxygen and hydrogen chloride under the action of a molybdenum catalyst:
the method has the advantages of advanced process technology, large device scale, high automation degree, good comprehensive utilization, low energy consumption and good product quality. However, in recent years, due to the steep rise in petroleum price and high residence time, the ethylene raw material is limited in price increase, production and development.
At present, the ethylene oxychlorination method is generally adopted in the production of vinyl chloride abroad, and about 70 percent of manufacturers in China still adopt the calcium carbide acetylene to produce the vinyl chloride because petroleum resources are in short supply, coal resources and limestone resources are abundant, and the current practical situation of the chlor-alkali industry is determined. Particularly, in recent years, the price of petroleum is greatly increased and the contradiction between supply and demand of polyvinyl chloride (PVC) is more prominent, and more methods for producing PVC by the calcium carbide acetylene method are adopted.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a novel method for producing vinyl chloride by an acetylene method and special equipment for realizing the method, and the defects of the existing method are overcome.
The technical problem to be solved by the invention is realized by the following technical scheme:
the invention provides a new method for producing chloroethylene by an acetylene method, which comprises the following steps:
(1) the two-stage pressure reaction and the heptane circulation heat dissipation process are adopted to prepare the crude chloroethylene:
acetylene and hydrogen chloride with water content below 10ppm are mixed in the volume ratio of 1 to 1-1.02, preheated to 100-150 deg.c and fed into HgCl carrier filled with active carbon2Reacting in a first-stage reactor of the catalyst, controlling the temperature to be 100-180 ℃, and reacting to generate crude chloroethylene mixed gas; cooling the mixed gas, filtering to remove solid particles larger than 10 microns, compressing to 370-400KPa (G), cooling, condensing, and partially condensing to obtain liquid chloroethylene;
condensing a part of the chloroethylene gas into liquid chloroethylene, sequentially entering a stripping tower, a rectifying tower and a finished product tower for treatment, and refining the chloroethylene;
the uncondensed mixed gas containing unreacted acetylene and hydrogen chloride is preheated to 100 ℃ and 150 ℃, enters a two-stage reactor under the pressure of 270kpa (g), and is subjected to HgCl reaction2Under the action of the catalyst, the reaction is continued to generate chloroethylene, and the reaction temperature is controlled at 100-180 ℃.
Mixing a part (50-60%) of chloroethylene generated by the second-stage reactor with chloroethylene mixed gas including unreacted acetylene and hydrogen chloride generated by the first-stage reactor, cooling, filtering to remove solid particles larger than 10 microns, compressing to 370-400KPa (G), cooling and condensing, partially condensing to obtain liquid chloroethylene, and then feeding the liquid chloroethylene into a stripping tower to refine chloroethylene;
the other part (about 40-50 percent, the mixed gas comprises inert gas and a small amount of unreacted hydrogen chloride and acetylene) of the chloroethylene generated by the two-stage reactor is cooled, condensed and deeply condensed, the liquid chloroethylene is sent to a stripping tower, and the uncondensed gas is subjected to alkali cleaning and then is discharged after reaching the standard.
The reaction heat generated by the reaction is removed by boiling liquid heptane outside the pipe;
(2) refining vinyl chloride:
heating liquid chloroethylene containing saturated hydrogen chloride and acetylene in a stripping tower to remove the hydrogen chloride, acetylene and a small amount of inert gas dissolved in the chloroethylene, cooling and condensing the partially evaporated material, refluxing condensate to the stripping tower, and feeding uncondensed gas into a second-stage reactor.
The temperature of the bottom of the stripping tower is 29-32 ℃, the temperature of the top of the stripping tower is-10 ℃, and the pressure is 312-.
And (3) feeding the material containing heavy components at the bottom of the stripping tower into a rectifying tower, heating, condensing the evaporated chloroethylene gas, refluxing part of condensate into the rectifying tower, feeding the rest liquid chloroethylene into a finished product tower filled with active aluminum chloride, and removing trace HCl in the chloroethylene to obtain the refined chloroethylene.
And the heavy component separated from the rectifying tower enters a heavy component stripping tower, and is indirectly heated by steam, and chloroethylene dissolved in the heavy component is removed and recovered, and then the heavy component can be packaged and sold as a byproduct.
The temperature of the bottom of the rectifying tower is 65-85 ℃, the temperature of the top of the rectifying tower is 45-55 ℃, and the pressure is 550-690Kpa (g).
The novel method for producing vinyl chloride by the acetylene method also comprises the following steps:
preparing acetylene and hydrogen chloride respectively: acetylene gas is compressed, dewatered at low temperature, and then put into a carbon steel dryer filled with a molecular sieve for drying, so that the water content of the acetylene gas is below 10 ppm; the hydrogen chloride is prepared by a known hydrochloric acid desorption method, the obtained hydrogen chloride does not contain free chlorine, and the water content in the hydrogen chloride is removed by three series-connected packed towers which take sulfuric acid as circulating liquid, and the water content is lower than 10 ppm.
The novel method for producing vinyl chloride by the acetylene method comprises the following steps:
the quality indexes of the raw material acetylene prepared in the step reach: the content of acetylene is more than or equal to 99.6 percent (V), the content of nitrogen is less than or equal to 0.37 percent (V), the content of chlorine sulfide is less than or equal to 0.004 percent (V), and the content of phosphine is less than or equal to 0.04 percent (V); the quality indexes of the prepared raw material hydrogen chloride reach: the content of hydrogen chloride is more than or equal to 99.95 percent (V), and the content of water is less than or equal to 10 ppm; the steps are subjected to two-stage reaction, and the final conversion rate of acetylene can reach more than 99%;
the chloroethylene treated by the steps reaches the following standard: the purity of the chloroethylene is more than or equal to 99.95 percent; the acetylene content is less than or equal to 5 ppm; the acetaldehyde content is less than or equal to 5 ppm; the butadiene content is less than or equal to 8 ppm; the content of dichloroethane is less than or equal to 30 ppm; the water content is less than or equal to 100 ppm; the other heavy chlorinated hydrocarbons are less than or equal to 200 ppm; the iron content is less than or equal to 1 ppm; the total amount of impurities is less than or equal to 500 ppm.
The novel method for producing vinyl chloride by the acetylene method also further comprises the following steps: HgCl used in addition reaction of acetylene and hydrogen chloride2And (3) treating the mercury-containing sewage generated by the catalyst, adding sodium hydrosulfide and filter aid diatomite into the mercury-containing sewage, performing filter pressing, collecting waste liquid, performing further conventional treatment and discharging, and recycling waste residues to mercury ore.
The invention also provides a shell-and-tube heat exchanger for realizing the novel method for producing chloroethylene by the acetylene method, which is a first-stage reactor or a second-stage reactor and comprises a cylinder body (1), an upper end enclosure (2) and a lower end enclosure (3) which are matched with the cylinder body (1), and the shell-and-tube heat exchanger is characterized in that: a reaction tube (4) is arranged in the cylinder body (1), and the catalyst (5) is filled in the reaction tube (4).
The second-stage reactor in the novel method for producing vinyl chloride by the acetylene method adopts a reaction tube with a small diameter (phi 19 x 2).
The other devices are all the existing devices.
The temperature and pressure ranges of the present invention are all conventional in the art and the expected variation is consistent.
The method for producing chloroethylene by the acetylene method has the following advantages and characteristics:
1. the treatment of raw material gas is very strict. The acetylene and the hydrogen chloride with high quality and the proportion of the acetylene and the hydrogen chloride after the treatment by the special process are favorable for the smooth proceeding of the reaction of the chloroethylene, can effectively prevent the caking of the catalyst and the corrosion of equipment, ensure the catalyst and the equipment to be in a good running state, are very favorable for the normal, stable, safe, high-efficiency, high-quality and low-consumption production of the chloroethylene, and greatly reduce the parking loss caused by the corrosion of the equipment and the caking of the catalyst.
2. The reaction is carried out in a first-stage reactor and a second-stage (main reactor and circulating) reactor, and the pressure of the second-stage reactor is about 8-10 times of the pressure of the second-stage reactor of thedomestic device. The two-stage pressure reaction process has great space flow rate and space-time yield over twice that of available reactor, and this is favorable to raising reaction speed and raising the conversion rate of the un-reacted matter. Therefore, the single reactor has high production strength and large production capacity, which is several times of the existing reactor, and has small occupied area and less investment.
3. The catalyst adopts mercury chloride (HgCl) of selected high-activity activated carbon2) The catalyst has short induction period or no induction period and needs no activation from the test production, while the domestic hydrogen chloride needs hours for activating the catalyst,even up to tens of hours; high activity, greatly shortened auxiliary production time, and high synthesis conversion rate up to over 99%.
4. The heat released in the synthesis reaction process is transferred by adopting heptane boiling heat. Because the latent heat of vaporization of heptane is large, and the reaction with hydrogen chloride and the like is avoided, the reaction temperature is easy to control, the reaction process is quite stable, the catalyst is not easy to sublimate and has low consumption, the catalytic consumption is 1/3-1/2 in China, the potential danger of equipment corrosion caused by the reaction of equipment leakage and water is particularly avoided, and the smooth and stable operation of production is ensured.
5. The chloroethylene refining system adopts an optimal process flow. Firstly removing low-boiling-point substances such as hydrogen chloride and acetylene light components, and then removing high-boiling-point substances such as dichloroethane heavy components. The tail gas of the rectifying tower adopts deep condensation, the product adopts the technologies of active alumina deep adsorption drying and the like, the product quality is good, therecovery rate of chloroethylene is high, the discharge of three wastes is less, the international advanced level is reached, and the improvement of the quality of PVC products is facilitated.
6. Strict treatment of three wastes (waste gas, waste liquid and waste residue) and less environmental pollution. The waste gas, waste liquid and waste residue discharged by the device can be recycled, so that the pollution to the environment is reduced. Particularly, all the mercury-containing sewage from a mercury pollution area, a catalyst unloading area, a mercury cleaning area and a mercury treatment area is treated, and the emission standard specified by the state is completely met.
7. The parking is easy to start and stop, and the automatic degree is high: the production process of the whole device adopts DCS monitoring, the operation is simple, accurate, safe and reliable, and the start and stop of the vehicle are easy.
8. The invention adopts high-quality raw material gas, reasonable process flow, unique reactor structure and catalyst, high-efficiency heptane heat dissipation and mercury treatment process and the like which are unique to the invention. The technical and economic indexes are advanced, the consumption of acetylene is 440 kg/ton of chloroethylene, and the consumption of hydrogen chloride is 615 kg/ton of chloroethylene; the purity of the vinyl chloride is as high as more than 99.96 percent (in the domestic acetylene method device, acetylene consumes 540-558 kg/ton of vinyl chloride, hydrogen chloride consumes 750-800 kg/ton of vinyl chloride, and the purity of the vinyl chloride is 99.9 percent). The content of impurities such as acetylene, high-boiling residues, water and the like is low, and the advanced international level is reached.
9. The invention relates to a method for producing chloroethylene by a digestive absorption and independent innovation acetylene method, which comprises the following steps: the special two-stage pressure reaction and heptane circulating cooling heat dissipating process produces vinyl chloride in a reactor with special structure through the reaction of catalyst, and the vinyl chloride monomer with high purity, low cost and less pollution is obtained through optimal refining, recovering and three-waste treatment.
In conclusion, the method has the advantages of reasonable process flow, high equipment production strength, high production capacity, good product quality, low production cost, less three-waste discharge, small environmental pollution and the like, and has good development prospect in the production of PVC by the calcium carbide acetylene method.
The advantages of the method of the invention are proved by the material feeding trial production test of Haiji company of Uhai city of Mongolia in 2004 at 9 and 18 months. The test successfully gets through the whole process and produces qualified products. As a result, the single reactor (also called as a main reactor) has high production intensity, large production capacity which is several times of the existing reactor, small occupied area and less investment. For example, a vinyl chloride plant producing 6 ten thousand tons annually requires only 5 to 6 main reactors (also called first-stage reactors) and 2 circulating reactors (also called second-stage reactors). From the current pilot production situation, the single production capacity of the main reactor exceeds 1 ten thousand tons/year of vinyl chloride, and reaches 1.3 ten thousand tons/year of vinyl chloride.
Drawings
FIG. 1 is a block diagram of the process flow of the method of the present invention.
FIG. 2 is a schematic diagram of the reactor configurationof the process of the present invention.
Detailed Description
Example 1
A new method for producing vinyl chloride by an acetylene process as shown in fig. 1 and fig. 2, comprising the following steps:
(1) respectively preparing acetylene and hydrogen chloride as raw materials;
acetylene is cleaned, neutralized and treated to remove impurities in the acetylene, after the pressure is increased by 107KPa, the acetylene is cooled to 2-5 ℃ by a tubular heat exchanger taking Freon as a refrigerant, a large amount of water carried by the acetylene gas is removed at low temperature, and then the acetylene gas enters a carbon steel dryer filled with aluminosilicate molecular sieves, so that the moisture content of the acetylene gas is extremely low and reaches below 10ppm through the adsorption effect of the molecular sieves on the water;
the hydrogen chloride is prepared by a known hydrochloric acid desorption method, has the purity higher than 99.95 percent and does not contain free chlorine, the moisture contained in the hydrogen chloride is removed by three series-connected packed towers which take sulfuric acid as circulating liquid, and the water content is lower than 10 ppm;
after the treatment by the process, the quality indexes of acetylene and hydrogen chloride reach: acetylene: acetylene content is not less than 99.6% (V), nitrogen content is not more than 0.37% (V), chlorine sulfide content is not more than 0.004% (V), phosphine content is not more than 0.04% (V), hydrogen chloride: the content of hydrogen chloride is more than or equal to 99.95 percent (V) and the content of water is less than or equal to 10 ppm.
(2) The two-stage pressure reaction and heptane circulation heat dissipation process are adopted to prepare the crude chloroethylene:
acetylene and hydrogen chloride are mixed according to the volume ratio of 1: 1, and enter a first-stage reactor after being preheated to 100 ℃; the reactor is a shell-and-tube heat exchanger, HgCl of active carbon carrier2The catalyst is filled in the tube pass;
acetylene and hydrogen chloride are passed through the tube side in HgCl2Performing addition reaction under the action of a catalyst to generate a chloroethylene mixed gas; removing reaction heat from heptane boiling outside the tube; controlling the reaction temperature to be 100-180 ℃; acetylene, hydrogen chloride in HgCl2Under the action of the catalyst, crude chloroethylene gas is generated by reaction, and the synthesis conversion rate is controlled to be about 85%;
cooling to 40 deg.C by reactor discharge cooler, introducing into compressor suction filter to remove solid particles larger than 10 μm, introducing into chloroethylene compressor, and compressing gas to 370 KPa 400KPa (G); then the refrigerant is cooled by a cooler behind a compressor and then enters a two-stage condenser for cooling and condensation by using a refrigerant;
condensing part of the gas into liquid chloroethylene, and feeding the liquid chloroethylene into a stripping tower feeding tank; the non-condensable gas (uncondensed chloroethylene, unreacted acetylene, hydrogen chloride and the like) enters a two-stage reactor (also called a circulating reactor), the reactor is a vertically installed shell-and-tube heat exchanger, and the heat exchange tube adopts a small-diameter seamless steel tube. Catalyst is filled in the tube pass, non-condensable gas flows through the tube pass under higher pressure, and acetylene and hydrogen chloride in the non-condensable gas continuously perform additionreaction to generate chloroethylene under the action of the catalyst; the reaction heat is removed by boiling heptane outside the tube; after two-stage reaction, the final conversion rate of acetylene can reach more than 99 percent; about 50-60% of generated chloroethylene gas is mixed with material flow produced by a first-stage reactor, and the rest chloroethylene gas also comprises inert gas and a small amount of unreacted hydrogen chloride and acetylene, and is discharged after reaching the standard after cooling, deep condensation and alkali cleaning.
(3) Refining treatment of vinyl chloride:
liquid chloroethylene containing saturated hydrogen chloride and acetylene in a stripping tower feeding tank enters a light component stripping tower, and is heated by a light component stripping tower reboiler to remove hydrogen chloride, acetylene and a small amount of inert gas light component low-boiling-point substances dissolved in chloroethylene; the gas enters a secondary condenser through a pressure control valve at the top of the tower for condensation, chloroethylene is condensed and enters a feeding tank of a stripping tower, and the non-condensable gas of light components such as removed acetylene, hydrogen chloride and the like enters a secondary reactor; the tower is a sieve plate tower, the temperature of the bottom of the stripping tower is 29-32 ℃, the temperature of the top of the stripping tower is-10 ℃, and the pressure is 312-.
Then the tower bottom material enters a rectifying tower to separate heavy components such as dichloroethane and the like;
boiling in the chloroethylene rectifying tower is realized by a reboiler at the bottom of the chloroethylene rectifying tower, so that the temperature at the bottom of the rectifying tower is controlled at 65 ℃, and the temperature at the top of the rectifying tower is controlled at 45 ℃ to ensure the quality ofchloroethylene monomers; condensing the tower top steam by a rectifying tower top condenser, then feeding the condensed tower top steam into a reflux tank, wherein part of materials are used for refluxing, cooling the rest materials to 38 ℃ by a chloroethylene product condenser, and then feeding the cooled materials into a finished product tower filled with activated alumina to remove trace HCl in chloroethylene, so that refined chloroethylene is obtained; the chloroethylene rectifying tower is a sieve plate tower;
the refined chloroethylene can be sent to a polymerization process to produce PVC. The dichloroethane heavy component high-boiling residue separated from the rectifying tower enters a heavy component stripping tower, is indirectly heated by steam, and can be packaged and sold as a byproduct after removing and recovering the chloroethylene dissolved in the heavy component.
The treated chloroethylene can reach the following standard: the purity of the chloroethylene is more than or equal to 99.95 percent; the acetylene content is less than or equal to 5 ppm; the acetaldehyde content is less than or equal to 5 ppm; the butadiene content is less than or equal to 8 ppm; the content of dichloroethane is less than or equal to 30 ppm; the water content is less than or equal to 100 ppm; the other heavy chlorinated hydrocarbons are less than or equal to 200 ppm; the iron content is less than or equal to 1 ppm; the total amount of impurities is less than or equal to 500 ppm.
The invention also provides a shell-and-tube heat exchanger for realizing the novel method for producing chloroethylene by the acetylene method, which is a reactor and comprises a cylinder body 1, an upper end enclosure 2 and an upper end enclosure 3, wherein the upper end enclosure 2 and the upper end enclosure 3 are matched with the cylinder body 1, and the shell-and-tube heat exchanger is characterized in that: a reaction tube 4 is arranged in the cylinder 1, and a catalyst 5 is arranged in the reaction tube 4.
The invention also relates to HgCl used in the addition reaction of acetylene and hydrogen chloride2And (3) treating the mercury-containing sewage generated by the catalyst, adding sodium hydrosulfide and filter aid diatomite into the mercury-containing sewage, performing filter pressing, collecting waste liquid, performing further conventional treatment and discharging, and recycling waste residues to mercury ore.
The process has the following advantages:
1. high-quality chloroethylene is obtained through the two-stage pressure reaction process and is used for producing the polyvinyl chloride or used as a raw material for producing products in other industries.
2. The heptane is utilized for circulating cooling and heat dissipation, the synthesis reaction temperature is easy to control, the reaction process is quite stable, the catalyst is not easy to sublimate, the consumption is low, the potential risk of equipment corrosion caused by water cooling leakage is particularly avoided, and the stable operation of production is ensured.
3. The ethylene synthesis uses mercury chloride (HgCl) impregnated by activated carbon as carrier2) The catalyst of (1). High activity, greatly shortened auxiliary production time, and high synthesis conversion rate up to over 99%.
4. The high-efficiency improved main and circulating reactors are fixed bed tubular reactors, which are equivalent to a large tubular heat exchanger, catalyst is filled in the tube, heptane is used for circulating cooling and heat dissipation outside the tube, the reaction temperature is controlled, and acetylene and hydrogen chloride are subjected to addition reaction under the action of the catalyst to generate vinyl chloride. Has thecharacteristics of simple structure, high production strength, large production capacity and the like.
5. The mercury-containing sewage is treated. It is necessary to use an HgCl in the addition reaction of acetylene and hydrogen chloride2The catalyst, the device, treats the sewage to make the sewage reach the national discharge standard. Adding sodium hydrosulfide, reacting the mercury in the waste water with the sodium hydrosulfide to generate water-insoluble mercury sulfide precipitate, adding diatomite as filter aid, press-filtering by a filter press, and collecting the waste liquid in a reservoirPumping the waste residue into a sewage treatment plant by a pump for further treatment, and barreling the waste residue and sending the waste catalyst back to the mercury ore for recycling treatment. The mercury content of the treated mercury-containing sewage can be reduced to 0.02 mg/L, which is lower than the requirement of 0.05 mg/L of the Integrated wastewater discharge Standard, and the mercury-containing sewage completely reaches the discharge Standard specified by the state.
Example 2
Referring to fig. 1 and fig. 2, the process flow diagram and the reactor of the present invention are the same as those of example 1, except that:
the step (1): for the preparation of acetylene and hydrogen chloride respectively: acetylene gas is compressed and dried at low temperature, so that the moisture content of the acetylene gas reaches below 10 ppm; removing water by adopting hydrogen chloride without free chlorine and taking sulfuric acid as circulating liquid to ensure that the water content of the hydrogen chloride is less than 10 ppm;
the step (2): the acetylene and the hydrogen chloride are mixed according to the volume ratio of 1: 1.02; the crude vinyl chloride gas was cooled to 45 ℃; the first stage reactor pressure is 80KPa (G) andthe second stage reactor pressure is 270KPa (G).
The step (3): the temperature of the bottom of the stripping tower is 32 ℃, the temperature of the top of the stripping tower is 0 ℃, and the pressure is 312KPa (G);
the temperature of the bottom of the rectifying tower is 85 ℃, the temperature of the top of the rectifying tower is 55 ℃, steam at the top of the rectifying tower enters a reflux tank after being condensed, part of materials are used for reflux, and the rest materials are cooled to 38 ℃ by a chloroethylene condenser and then enter a finished product tower filled with activated alumina.
A shell-and-tube heat exchanger in the new method for producing chloroethylene by acetylene method is a first-stage reactor, which comprises a cylinder body 1, an upper end enclosure 2 and an upper end enclosure 3, wherein the upper end enclosure 2 and the upper end enclosure 3 are matched with the cylinder body 1, and the shell-and-tube heat exchanger is characterized in that: the cylinder (1) is internally provided with a reaction tube 4, and the catalyst 6 is positioned in the reaction tube 4. The second stage reactor employs a reaction tube of small diameter phi 19 x 2.
The main reactor (first stage reactor) operating pressure: tube pass: 0.04MPa, and the shell pass is 0.006-0.367 MPa; operating temperature: the tube side is 100-180 ℃, and the shell side is 100-160 ℃. The circulating reactor (also called two-stage reactor) does not have a core protection block. Operating pressure: the tube pass is 0.27MPa, the shell pass is 0.006-0.367 MPa, and the operating temperature is as follows: the tube side is 100-180 ℃, and the shell side is 100-160 ℃. A heat exchange tube: 2186 are used.
Compared with the domestic acetylene method chloroethylene production technology, the chloroethylene production technology has the following characteristics:
1. strict treatment of raw material gas
1) Domestic device: mixing hydrogen chloride and acetylene gas, and freeze-dehydrating to obtain mixed gas (HCl, C)2H2) The water content is as high as 600-2000 ppm.
2) The hydrogen chloride is dried by three-stage sulfuric acid, acetylene gas is dried by a molecular sieve and then mixed, and the moisture content of the mixed gas is less than 10 ppm. Therefore, the catalyst is prevented from caking due to the fact that a large amount of moisture is brought into the raw material gas, the service life of the catalyst is prolonged, the low water content of the raw material gas is beneficial to reducing equipment corrosion and the generation of byproducts, and normal, stable, safe, high-efficiency, high-quality and low-consumption production is guaranteed.
2. The single reactor has high production capacity
1) Domestic device: the acetylene flow introduced into the catalyst layer of the first-stage converter (equivalent to the main reactor of the device of the invention) is limited to 25-40 m3Acetylene/m3Catalyst h, conversion rate is about 65%.
2) The heat exchange tube of the main reactor adopts heptane boiling heat transfer, domestic softened water is adopted, and the acetylene flow introduced into the catalyst layer of the reactor reaches 140m3Acetylene/m3Catalyst, h, conversion rate is 85% -95%.
3. Two-stage pressure reaction
1) Domestic device: the mixed gas (comprising chloroethylene, acetylene and hydrogen chloride) after the reaction of the first-stage converter directly enters a second-stage converter, and the second-stage conversion rate is about 60%.
2) The mixed gas after the reaction of the main reactor is firstly compressed and condensed, the uncondensed gas (comprising chloroethylene, acetylene and hydrogen chloride) enters the circulating reactor, the reaction pressure is 270Kpa, the reaction speed is favorably improved, and the unreacted substance of the circulating reactor can still reach higher conversion rate which is more than 80 percent under the condition of higher inert gas partial pressure.
Claims (6)
1. A new method for producing vinyl chloride by an acetylene method comprises the following steps:
(1) the two-stage pressure reaction and the heptane circulation heat dissipation process are adopted to prepare the crude chloroethylene:
acetylene and hydrogen chloride with water content below 10ppm are mixed in the volume ratio of 1 to 1-1.02, preheated to 100-150 deg.c and fed into HgCl carrier filled with active carbon2Reacting in a first-stage reactor of the catalyst at 100-180 ℃ to generate crude chloroethylene mixed gas; cooling the mixed gas, filtering to remove solid particles larger than 10 microns, compressing to 370-400KPa (G), cooling, condensing, and partially condensing to obtain liquid chloroethylene;
condensing a part of the chloroethylene gas into liquid chloroethylene, sequentially entering a stripping tower, a rectifying tower and a finished product tower for treatment, and refining the chloroethylene;
the uncondensed mixed gas containing unreacted acetylene and hydrogen chloride is preheated to 100 ℃ and 150 ℃, enters a two-stage reactor under the pressure of 270kpa (g), and is subjected to HgCl reaction2Under the action of the catalyst, the reaction is continued to generate chloroethylene, and the reaction temperature is controlled at100-180 ℃.
Mixing a part of chloroethylene generated by the second-stage reactor with chloroethylene mixed gas including unreacted acetylene and hydrogen chloride generated by the first-stage reactor, cooling, filtering to remove solid particles larger than 10 microns, compressing to 370-400KPa (G), cooling, condensing, partially condensing to obtain liquid chloroethylene, and then refining chloroethylene in a stripping tower;
the other part of the chloroethylene generated by the second-stage reactor comprises inert gas and a small amount of unreacted hydrogen chloride and acetylene), cooling, condensing and deeply condensing the mixed gas, sending the liquid chloroethylene to a stripping tower, and discharging the uncondensed gas after reaching the standard after alkaline cleaning.
The reaction heat generated by the reaction is removed by boiling liquid heptane outside the pipe;
(2) refining vinyl chloride:
heating liquid chloroethylene containing saturated hydrogen chloride and acetylene in a stripping tower to remove the hydrogen chloride, acetylene and a small amount of inert gas dissolved in the chloroethylene, cooling and condensing the partially evaporated material, refluxing condensate to the stripping tower, and feeding uncondensed gas into a second-stage reactor.
The temperature of the bottom of the stripping tower is 29-32 ℃, the temperature of the top of the stripping tower is-10 ℃, and the pressure is 312-.
And (3) feeding the material containing heavy components at the bottom of the stripping tower into a rectifying tower, heating, condensing the evaporated chloroethylene gas, refluxing part of condensate into the rectifying tower, feeding the rest liquid chloroethylene into a finished product tower filled with active aluminum chloride, and removing trace HCl in thechloroethylene to obtain the refined chloroethylene.
The temperature of the bottom of the rectifying tower is 65-85 ℃, the temperature of the top of the rectifying tower is 45-55 ℃, and the pressure is 550-690Kpa (g).
2. The novel process for producing vinyl chloride by the acetylene process according to claim 1, further comprising:
preparing acetylene and hydrogen chloride respectively: acetylene gas is compressed, dewatered at low temperature, and then put into a carbon steel dryer filled with a molecular sieve for drying, so that the water content of the acetylene gas is below 10 ppm; the hydrogen chloride is prepared by a known hydrochloric acid desorption method, the obtained hydrogen chloride does not contain free chlorine, and the water content in the hydrogen chloride is removed by three series-connected packed towers which take sulfuric acid as circulating liquid, and the water content is lower than 10 ppm.
3. The novel process for producing vinyl chloride by the acetylene process according to claim 1 or 2, further comprising:
preparing acetylene and hydrogen chloride respectively: acetylene gas is compressed and dried at low temperature, so that the moisture content of the acetylene gas reaches below 10 ppm; removing water by adopting hydrogen chloride without free chlorine and taking sulfuric acid as circulating liquid to ensure that the water content of the hydrogen chloride is less than 10 ppm;
the acetylene and the hydrogen chloride are mixed according to the volume ratio of 1: 1; cooling the crude chloroethylene gas to 40 +/-5 ℃; the reactor pressure was 312KPa (G),
the temperature of the bottom of the stripping tower is 32 ℃, the temperature of the top of the stripping tower is 0 ℃, and the pressure is 312KPa (G);
the temperature of the bottom of the rectifying tower is 85 ℃, steam at the top of the rectifying tower enters a reflux tank after being condensed, part of materials are used for refluxing, and the rest materials are cooled to 38 ℃ by a chloroethylene condenser and then enter a finished product tower filled with activated alumina.
4. A novel process for the production of vinyl chloride according to the acetylene process of claim 1 or 2:
the quality indexes of the raw material acetylene prepared in the step reach: the content of acetylene is more than or equal to 99.6 percent (V), the content of nitrogen is less than or equal to 0.37 percent (V), the content of chlorine sulfide is less than or equal to 0.004 percent (V), and the content of phosphine is less than or equal to 0.04 percent (V); the quality indexes of the prepared raw material hydrogen chloride reach: the content of hydrogen chloride is more than or equal to 99.95 percent (V), and the content of water is less than or equal to 10 ppm; the steps are subjected to two-stage reaction, and the final conversion rate of acetylene can reach more than 99%;
the chloroethylene treated by the steps reaches the following standard: the purity of the chloroethylene is more than or equal to 99.95 percent; the acetylene content is less than or equal to 5 ppm; the acetaldehyde content is less than or equal to 5 ppm; the butadiene content is less than or equal to 8 ppm; the content of dichloroethane is less than or equal to 30 ppm; the water content is less than or equal to 100 ppm; the other heavy chlorinated hydrocarbons are less than or equal to 200 ppm; the iron content is less than or equal to 1 ppm; the total amount of impurities is less than or equal to 500 ppm.
And the heavy component separated from the rectifying tower enters a heavy component stripping tower, and is indirectly heated by steam, and chloroethylene dissolved in the heavy component is removed and recovered, and then the heavy component can be packaged and sold as a byproduct.
5. The novel process for producing vinyl chloride by the acetylene process according to claim 1 or 2, further comprising: HgCl used in addition reaction of acetylene and hydrogen chloride2And (3) treating the mercury-containing sewage generated by the catalyst, adding sodium hydrosulfide and filter aid diatomite into the mercury-containing sewage, performing filter pressing, collecting waste liquid, performing further conventional treatment and discharging, and recycling waste residues to mercury ore.
6. A shell-and-tube heat exchanger for implementing the new method for producing vinyl chloride by acetylene method according to any one of claims 1 to 4, comprising a cylinder (1), an upper end enclosure (2) and a lower end enclosure (3) which are matched with the cylinder (1), characterized in that: a reaction tube (4) is arranged in the cylinder body (1), and the catalyst (5) is filled in the reaction tube (4).
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| CN102516023B (en) * | 2011-12-08 | 2014-06-18 | 内蒙古宜化化工有限公司 | Vinyl chloride rectification process low tower reflux novel technology |
| CN102516023A (en) * | 2011-12-08 | 2012-06-27 | 内蒙古宜化化工有限公司 | Vinyl chloride rectification process low tower reflux novel technology |
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