WO2014056301A1 - 生产醋酸乙烯的方法 - Google Patents

生产醋酸乙烯的方法 Download PDF

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Publication number
WO2014056301A1
WO2014056301A1 PCT/CN2013/001225 CN2013001225W WO2014056301A1 WO 2014056301 A1 WO2014056301 A1 WO 2014056301A1 CN 2013001225 W CN2013001225 W CN 2013001225W WO 2014056301 A1 WO2014056301 A1 WO 2014056301A1
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Prior art keywords
vinyl acetate
ethylene
gas
heat exchanger
column
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PCT/CN2013/001225
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English (en)
French (fr)
Inventor
张敏华
董秀芹
李永辉
刘成
马静
李桂明
耿中峰
余英哲
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天津大学
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Publication of WO2014056301A1 publication Critical patent/WO2014056301A1/zh

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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C67/00—Preparation of carboxylic acid esters
    • C07C67/04—Preparation of carboxylic acid esters by reacting carboxylic acids or symmetrical anhydrides onto unsaturated carbon-to-carbon bonds
    • C07C67/05—Preparation of carboxylic acid esters by reacting carboxylic acids or symmetrical anhydrides onto unsaturated carbon-to-carbon bonds with oxidation

Definitions

  • the present invention relates to a process for producing vinyl acetate, and more particularly to a process for producing vinyl acetate having reduced energy consumption. Background technique
  • Vinyl acetate (VAC) also known as vinyl acetate
  • VVA polyvinyl alcohol
  • EVA vinyl acetate-ethylene copolymer
  • PVAC polyvinyl acetate
  • EVC vinyl acetate-vinyl chloride copolymer
  • sizing agents for adhesives, paper or fabrics, paints, inks, leather processing, emulsifiers, water soluble films, soil conditioners, and the like.
  • the production route of vinyl acetate is either ethylene or acetylene.
  • ethylene production is currently dominant.
  • the ethylene vinyl acetate production process is to feed the raw materials ethylene, oxygen and acetic acid into the reactor and contact with the catalyst, and react at a pressure of 0.5-1.4 MPa (G) and a temperature of 130-220 °C to form VA (:, water and a small amount of deputy
  • G 0.5-1.4 MPa
  • VA water and a small amount of deputy
  • the product, the high-temperature reaction gas is cooled and condensed in multiple stages and then enters the gas separation tower to achieve the purpose of gas-liquid separation.
  • the unreacted ethylene gas is returned to the compressor.
  • the condensed acetic acid and VAC mixture are sent to the fine boring process for VAC refining.
  • the reactor steam drum In the early stage of operation of the ethylene vinyl acetate production unit, the reactor steam drum only produces low pressure steam for a long period of time. Since the low temperature of the low pressure steam cannot meet the heating requirements of other equipment, this part of the steam in the actual production is emptied for a long time until the pressure reaches the required level.
  • the venting time varies depending on the rate of temperature rise of the reactor, ranging from 3-5 months to 6-8 months, which causes a huge waste of energy.
  • the high-temperature reaction gas is generally subjected to multi-stage cooling condensation by a shell-and-tube heat exchanger, wherein the tube of the reaction gas condenser is a process medium, and the shell side is cooled. medium.
  • a shell-and-tube heat exchanger In order to prevent scaling of the shell side, no ionized water is used as a cooling medium in the production. This not only causes a large consumption of ion-free water, but also requires a separate ion-free water cooling system to provide temperature-free, ion-free water; this results in complex operations and a large equipment investment.
  • the first separator of the gas separation tower With multi-tube shell-and-tube heat exchangers, full backflow operation is not possible and a large amount of cooling water is consumed.
  • the acetic acid tower condensate cooler and the crude VAC tower condensate cooler of the rectification section of the ethylene vinyl acetate production process are required to supercool the overhead material to 37 ° C and then enter the phase separator, and the separated coarse
  • the VAC enters the subsequent rectification tower for further processing; the coolers used are all shell-and-tube heat exchangers, the heat exchange temperature difference is small, and the cooling water consumption is large.
  • the present invention relates to a process for producing vinyl acetate, particularly a process for the production of vinyl acetate by vapor phase oxidation of ethylene.
  • the invention relates to a process for the vapor phase oxidation of ethylene to produce vinyl acetate comprising an optional ethylene preparation process, a vinyl acetate synthesis process and a vinyl acetate refining process.
  • ethylene, oxygen and acetic acid are converted into ethyl acetate by a catalyst in a vinyl acetate synthesis reactor.
  • a catalyst known in the art for the vapor phase oxidation of ethylene to produce vinyl acetate such as a USI catalyst and a Bayer catalyst
  • a USI catalyst and a Bayer catalyst can be used.
  • Those skilled in the art will appreciate that other catalysts capable of effecting the vapor phase oxidation of ethylene to produce vinyl acetate can also be used.
  • the process of the invention uses a Bayer catalyst.
  • a reactor known in the art for the vapor phase oxidation of ethylene to produce vinyl acetate can be used.
  • the reactor described in "Ethylene Derivative Engineering", Chapter 9, Section 9.3.3, Chemical Industry Press, July 1995, can be used.
  • the ethylene can be commercially available ethylene. For example, from a petrochemical plant or other source.
  • the ethylene may be prepared from ethanol in the ethylene production section (i.e., the ethylene preparation process) in the process of the present invention.
  • the ethylene production section i.e., the ethylene preparation process
  • CN101798265A discloses a process for the preparation of vinyl acetate from bioethanol, the entire contents of which are incorporated herein by reference.
  • the ethylene production section comprises an ethylene synthesis system and an ethylene refining system.
  • the raw material ethanol is sent to the reactor.
  • the raw material ethanol is sent from the raw material tank area to the ethanol tank, and is preheated by the ethanol preheater to enter the ethanol evaporation tank.
  • the ethanol heated by the heater enters the heating furnace, is heated by the heating furnace, and is sent to the reactor.
  • the reactor used in the preparation of ethylene may be a reactor having three fixed beds in which ethanol is directly contacted with the catalyst bed to dehydrate to form ethylene while the temperature is lowered in the direction of the bed.
  • the reaction may be a gas phase reaction at a reaction temperature ranging from about 47 CTC to about 358 ° C, and the main component of the catalyst used is ⁇ - ⁇ 1 2 0 3 .
  • the reaction is an endothermic process and the heat required in the reaction can be provided by direct contact of the superheated steam with the reactant ethanol.
  • the present invention is not particularly limited in the conversion of ethanol to ethylene, and any suitable reaction type and reactor can be used as long as ethylene can be obtained from ethanol.
  • the reaction product after the reaction is then cooled.
  • the reaction product is cooled by heat exchange with superheated ethanol, as a heating medium for the ethanol evaporation can, and heat exchange with the raw material ethanol.
  • the cooled reaction product was sent to an ethylene condenser for further condensation.
  • the ethylene condenser can be condensed by air (i.e., using an air cooler).
  • the air cooler outlet temperature is from about 40 to about 50 °C, most preferably about 45 °C.
  • air e.g., ambient air
  • Air coolers are known to those skilled in the art; for example, an air cooler as described in detail later herein can be used.
  • the condensed gas-liquid mixture is separated in a gas-liquid separation tank to obtain gas phase ethylene and liquid phase wastewater.
  • the resulting vapor phase ethylene can then be further processed to obtain ethylene for the preparation of vinyl acetate.
  • the present invention is not limited to the treatment of the vapor phase ethylene as long as ethylene which can be used for the production of vinyl acetate can be obtained.
  • the gas phase ethylene is sent to an ethylene compressor, and the liquid phase wastewater is sent to a wastewater treatment unit outside the boundary area for treatment.
  • the compressed ethylene is sent to a caustic scrubber to remove co 2 from the crude ethylene.
  • the crude ethylene from which the co 2 and the polar compound are removed is dried by a molecular sieve dryer and sent to an ethylene refined product. System.
  • the ethylene is cooled by a cooler and sent to a desulfurization tower, and the top gas of the demethanizer is sent to a gas-liquid separation tank.
  • the tower liquid is ethylene which removes light component impurities, and is sent to an ethylene purification tower.
  • the ethylene product from the top of the ethylene purification tower is cooled and sent to the vinyl acetate synthesis section.
  • the tower kettle is an ethylene material containing heavy impurities and can be sent to a furnace for combustion.
  • ethylene is only partially converted in the vinyl acetate reactor, which results in a large amount of unconverted ethylene requiring recycling.
  • fresh ethylene from the ethylene source or from the ethylene production section, optionally mixed with recycled ethylene is then preheated and passed from the bottom to the acetic acid evaporator.
  • the preheating can be carried out using an outlet gas of a vinyl acetate synthesis reactor.
  • acetic acid is sprayed from the top, in which ethylene and acetic acid are countercurrently contacted, and a mixture of ethylene and acetic acid is taken out from the top of the evaporator.
  • the acetic acid content of the mixture gas can be achieved by controlling the top temperature of the evaporator.
  • the mixed gas of ethylene and acetic acid comes out from the top of the acetic acid evaporator, it is first preheated.
  • the acetic acid reactor outlet gas may be first heated and then further heated with steam.
  • the heated mixed gas is sent to an oxygen mixer and mixed with oxygen.
  • the oxygen mixer which is well known in the art, various oxygen mixers known in the art can be employed. For example, in the "Ethylene Derivative Engineering", Chapter 9, pp. 590-591, Chemical Industry Press, July 1995, a conventional oxygen mixer is disclosed; the present invention can employ such an oxygen mixer.
  • the mixed gas from the oxygen mixer is sent from the top to the vinyl acetate synthesis reactor.
  • a reactor known in the art for the vapor phase oxidation of ethylene to produce vinyl acetate can be used.
  • the acetic acid synthesis reactor can be, for example, a tubular fixed bed reactor. Ethylene, oxygen and acetic acid are converted to vinyl acetate by a catalyst in a reactor.
  • the catalyst may be, for example, a USI catalyst and a Bayer catalyst.
  • a Bayer catalyst is used.
  • the active ingredient of the Bayer catalyst is palladium and gold; the support is typically silica gel.
  • the reaction temperature is from about 138 to about 1 85 ° C and the pressure is generally about 785 kPa (gauge pressure). It will be understood by those skilled in the art that the process of the present invention has no particular requirements on the catalyst, support, temperature and pressure employed, as long as vinyl acetate is obtained from ethylene, oxygen and acetic acid in a gas phase process.
  • the vinyl acetate synthesis reactor is a tubular fixed bed reactor, and pressurized water is used between the tubes of the tubular fixed bed reactor for removing heat of reaction and producing Raw steam.
  • the tubular fixed bed reactor produces only low pressure steam at the beginning of the run. Typically the pressure of the low pressure steam is less than about 0.4 MPa.
  • the low pressure steam is treated using a steam mechanical recompression MVR technique.
  • medium pressure steam is produced by MVR technology, typically the medium pressure steam pressure is greater than about 0.4 MPa and less than about 0.8 MPa.
  • MVR technology is a new type of high-efficiency energy-saving technology. Its working principle is to use waste steam to pass through a mechanical steam compressor, so that its temperature, pressure and enthalpy are improved and used as a heat source to heat other equipment, thus effectively recovering waste heat steam. The latent heat, to achieve the purpose of energy saving. For MVR technology, you can refer to
  • the gas obtained after the reaction contains, in addition to the target product vinyl acetate, a large amount of unconverted ethylene and acetic acid, as well as carbon dioxide, water, oxygen and nitrogen. Since the ethylene single pass conversion is low during the synthesis of ethyl acetate, a large amount of unconverted ethylene must be recycled.
  • the reaction gas leaving the reactor may first be exchanged with the raw material gas through the first gas cooler (which can be used to heat the mixed gas of ethylene and acetic acid) and the second cooler (which can be used to heat the feed ethylene gas) to recover the product gas. The heat from the heat is cooled.
  • reaction gas cooled by the first and second coolers enters a water condenser, which is further cooled with cooling water to condense components such as acetic acid and vinyl acetate contained therein.
  • the reaction gases cooled by the first and second coolers are passed to an air cooler for further cooling.
  • the condensate outlet temperature of the air cooler is from about 70 to about U 0 °C.
  • the air cooler is a cooler that uses ambient air as a cooling medium, referred to as "air cooler".
  • air cooler Various known air coolers can be used herein. Those skilled in the art will know and understand how to select a suitable air cooler to meet the cooling needs. For example, in one type of air cooler, power is used to drive the impeller to rotate, and the generated eddy current continuously draws in air. The cold air contacts the heat pipe to transfer heat, so that the high temperature process fluid in the pipe is cooled or condensed.
  • an air cooler can adjust the cooling capacity by configuring the frequency modulation motor and adjusting the blade angle.
  • a common air cooler is mainly composed of a tube bundle, a fan and a frame.
  • the national standard GB/T 15386-94 describes the structure and performance requirements of the air cooler. Since the reacted gas contains a large amount of non-condensing components such as ethylene, oxygen, etc., it is difficult to completely condense acetic acid and vinyl acetate by means of indirect cooling. If the separation is not complete, it may cause acetic acid to be contained in the recycled ethylene. Even a very small amount of acetic acid may cause corrosion of the circulating gas compressor. Therefore, in general, a direct cooling device-gas separation column is used in the production of vinyl acetate.
  • the gas-liquid two phases of the reaction gas directly enter the lower portion of the gas separation column without being separated.
  • the gas-liquid two phases may be separated into gas separation columns after gas-liquid separation using a water condenser.
  • the gas separation tower is divided into three sections: upper, middle and lower.
  • the lower stage reaction liquid cooled by cooling water is circulated, and is in countercurrent contact with rising gas such as ethylene, carbon dioxide, acetic acid or vinyl acetate to condense the acetic acid contained therein; low temperature water (for example, chilled brine, methanol aqueous solution, etc.) is used in the middle stage.
  • the cooled reaction liquid circulates, and is in countercurrent contact with the rising gas to condense the high-boiling substance such as acetic acid or vinyl acetate contained therein; the upper stage is eluted with acetic acid.
  • the gas separation tower bottom liquid is cooled by the first cooler of the gas separation tower and then partially enters the lower part of the separation tower, and the other part is further cooled by the second cooler of the gas separation tower with low temperature water, and then enters the middle section of the gas separation tower, respectively.
  • the ascending gas is directly contacted in reverse flow to condense acetic acid and VAC in the gas phase.
  • the first separator of the gas separation column employs a plate heat exchanger or a double-shell tube-and-tube heat exchanger, such as a double-shell fixed shell-and-tube heat exchanger.
  • the first separator of the gas separation column employs a double-shell tube-and-tube heat exchanger, such as a double-shell fixed shell-and-tube heat exchanger.
  • any double-shell shell-and-tube heat exchanger or double-shell fixed shell-and-tube heat exchanger known in the art can be used as long as it achieves the desired cooling effect.
  • Those skilled in the art will know and understand how to select a suitable double-shell shell-and-tube heat exchanger or a double-shell fixed shell-and-tube heat exchanger to meet cooling needs.
  • a double shell shell-and-tube heat exchanger places a partition in the center of the bundle, the baffles being spaced up and down, and the shell side being split into two.
  • Plate heat exchanger is made up of a series A new type of high-efficiency heat exchanger with a corrugated metal sheet stacked. A thin rectangular channel is formed between the various sheets, and heat is exchanged through the sheets. It has a much higher heat transfer coefficient than conventional shell-and-tube heat exchangers.
  • the plate heat exchanger has a large logarithmic mean temperature difference and a small temperature difference at the end, which enables full countercurrent heat transfer. Any plate heat exchanger known in the art can be used as long as it achieves the desired cooling effect. Those skilled in the art know and master how to select a suitable plate heat exchanger
  • the gas coming out from the top of the gas separation column is substantially free of high boiling components such as acetic acid and vinyl acetate; its main components are ethylene, carbon dioxide and oxygen.
  • high boiling components such as acetic acid and vinyl acetate
  • its main components are ethylene, carbon dioxide and oxygen.
  • most of the circulation is returned to the vinyl acetate synthesis reactor; and a small portion is taken to remove the inert component such as carbon dioxide to ensure that the ethylene concentration is not lowered by the accumulation of the inert component. Thereby the synthesis reaction proceeds smoothly.
  • reaction liquid a mixture of acetic acid and vinyl acetate
  • degassing tank a degassing tank.
  • the gas dissolved in the liquid phase is desorbed by reducing the pressure, compressed by the recovery gas compressor, and sent to the water washing tower in combination with the gas for removing the carbon dioxide.
  • the gas fed into the water washing tower is washed with water, and the acetic acid and acetaldehyde contained therein are removed, and then sent to the absorption tower to absorb the carbon dioxide therein by the hot potassium carbonate aqueous solution, and sent to the fine unit from the reactor; :
  • the ethylene recovery tower is used to recover the ethylene and then burned to the torch to balance the inert gas in the reaction system.
  • the absorption liquid at the bottom of the absorption tower can be sent to the desorption column to desorb the carbon dioxide under reduced pressure and elevated temperature, and the carbon dioxide is discharged from the desorption column; the desorbed potassium carbonate solution is returned to the absorption tower for use as an absorption liquid.
  • the vinyl acetate synthesis reaction liquid contains, in addition to vinyl acetate, acetic acid, water, a low boiling component, and a high boiling component.
  • the gas phase composition is different from the composition of the liquid phase, and the proportion of the volatile matter in the gas phase is larger than that of the volatile matter in the liquid phase.
  • the ratio can be separated and purified by means of rectification. A series of rectification operations are carried out to give the components a fraction.
  • the vinyl acetate fine section includes acetic acid tower, coarse
  • VAC tower fine VAC tower, de-weighting tower, aldehyde ester concentration tower, acetaldehyde tower, dehydration tower and acetic acid Recycling tower.
  • the reaction liquid from the vinyl acetate synthesis section degassing tank (for example, as described above) is fed as a feed to the acetic acid column.
  • the bottom of the column recovers acetic acid, a majority of which is sent to the acetic acid evaporator of the vinyl acetate synthesis section, and the remainder is sent to a gas separation column and a water wash column for use as a rinse acetic acid.
  • Vapor is withdrawn at the top of the acetic acid column, the main components of which are vinyl acetate and water.
  • the vapor is condensed by a condenser and sent to an acetate column phase separation tank for stratification. A portion of the upper organic phase is refluxed, a portion of which is sent to the crude VAC column and the lower aqueous phase is sent to the dewatering column.
  • the overhead vapor of the acetic acid column is first condensed by a condenser, and the condensate is cooled by a condensate cooler and then passed to a phase separation tank of the acetic acid column for stratification.
  • the condensate cooler of the acetic acid column employs a plate heat exchanger or a double shell shell-and-tube heat exchanger, preferably a plate heat exchanger. Without being bound by any theory, it is believed that the use of a plate heat exchanger or a double-shell tube-and-tube heat exchanger achieves full backflow, increases the heat transfer temperature difference, and reduces the amount of cooling water.
  • Any plate heat exchanger or double shell shell and tube heat exchanger known in the art can be used as long as it achieves the desired cooling effect.
  • Those skilled in the art will know and understand how to select a suitable plate heat exchanger or double shell shell and tube heat exchanger.
  • a plate heat exchanger or a double-shell shell-and-tube heat exchanger as described above with respect to a gas separation column can be used.
  • a portion of the organic phase of the phase separation tank of the acetic acid column is sent to the crude VAC column.
  • the crude VAC column is a rectification column for separating water and low boiling point impurities dissolved in vinyl acetate.
  • the acetic acid containing no low boilers was taken out of the crude VAC tower and sent to the fine VAC tower.
  • the crude VAC column is topped with distilled water, low boiling point components, and a small amount of vinyl acetate, which, after condensation by the condenser, enters the coarse VAC column phase separation tank for stratification.
  • the upper organic phase is vinyl acetate and a low boiling component, partially refluxed, and partially sent to the aldehyde ester concentration column; the lower aqueous phase is sent to a dehydration column to recover the VAC therein.
  • the overhead vapor of the crude VAC column is first condensed by a condenser, and after the condensate is cooled by the condensate cooler, it enters the coarse VAC tower phase separation tank for stratification.
  • the crude VAC tower condensate cooler employs a plate heat exchanger or a double shell shell and tube heat exchanger, preferably a plate heat exchanger. Any plate heat exchanger or double shell shell and tube heat exchanger known in the art can be used as long as it achieves the required cooling effect fruit. Those skilled in the art will know and understand how to select a suitable plate heat exchanger or a double shell shell and tube heat exchanger.
  • the same plate heat exchanger or double shell shell and tube heat exchanger as described above can be used. It is believed that after using a plate heat exchanger or a double-shell tube-and-tube heat exchanger, full backflow can be achieved, the heat transfer temperature difference can be increased, and the amount of cooling water can be reduced.
  • the bottoms of the crude VAC column are sent to the fine VAC column feed.
  • the fine VAC column is used to remove high boiling components. Pure vinyl acetate is distilled off from the top of the fine VAC tower and condensed before being sent to the storage tank.
  • the column liquid is ethylene acetate and a high boiling component, which is sent to a de-weighting tower.
  • the de-weighting tower fine VAC is distilled from the top of the tower by means of rectification, partially refluxed, and partially sent to the crude VAC tower; the tower liquid is a vinyl acetate having a high concentration of heavy components, and is sent to the waste liquid treatment system. deal with.
  • the feed to the aldehyde ester concentration column is the organic phase separated by the coarse VAC column phase separation tank.
  • a low-boiling component mainly composed of acetaldehyde is distilled off, which is cooled by condensation, partially refluxed, and partially sent to an acetaldehyde column; the bottom liquid contains mainly vinyl acetate and is sent to the crude VAC tower.
  • the top reflux is carried out. Pure acetaldehyde is distilled off at the top of the acetaldehyde column, for example at a concentration of at least about 99%. After condensation through a condenser, by-product acetaldehyde is obtained.
  • the bottom of the acetaldehyde tower is the remaining light impurity component and is sent to a waste liquid treatment device for treatment.
  • the water separated from the aqueous phase of the acetic acid column phase separation tank and the crude VAC tower phase separation tank has a certain amount of vinyl acetate dissolved therein.
  • this portion of the material is sent to a dehydration column.
  • An azeotrope of vinyl acetate and water was distilled off from the top of the dehydration column, and after condensation by the condenser, it was returned to the above-mentioned coarse VAC tower phase separation tank for stratification.
  • the bottom material of the dehydration tower is water containing almost no vinyl acetate, and is discharged after being treated with wastewater.
  • the aqueous material separated from the aqueous phase of the acetic acid column phase separation tank and the crude VAC tower phase separation tank is preheated and then passed to the dehydration column.
  • the preheating of the water material is carried out using the bottoms of the dewatering column, wherein the preheating is carried out using a plate heat exchanger or a double shell shell and tube heat exchanger, preferably using a plate heat exchanger Implementation. Any plate heat exchanger or double shell shell and tube heat exchanger known in the art can be used as long as it achieves the desired cooling effect. Those skilled in the art will know and understand how to select a suitable plate heat exchanger or a double shell shell and tube heat exchanger.
  • the same plate heat exchanger or double shell shell and tube heat exchanger as described above can be used. It is believed that by using a plate heat exchanger or a double-shell tube-and-tube heat exchanger, the full countercurrent operation of the cold and heat medium is realized, the heat exchange temperature difference is increased, the feed temperature is increased, and the dehydration column reboiler is reduced. Fresh steam usage. As will be understood by those skilled in the art, if the recovered recycled acetic acid contains impurities having a boiling point higher than that of acetic acid, they will accumulate at the bottom of the acetic acid evaporator. To this end, it is necessary to periodically take out this part of the kettle liquid and send it to the acetic acid recovery tower.
  • the acetic acid recovery tower adopts a forced circulation type reboiler, and the acetic acid distilled from the top of the column is partially refluxed after being condensed, and partially returned to the rectification unit; the column is a high boiling point impurity, a polymer and other solid materials, and the bottom residue is pumped Send to a high boiling waste tank for centralized treatment.
  • FIG. 1 is a schematic flow chart showing an ethylene preparation section according to an embodiment of the present invention.
  • Fig. 2 is a schematic flow chart showing a vinyl acetate synthesis section according to an embodiment of the present invention.
  • Fig. 3 is a schematic flow chart showing a vinyl acetate rectification section according to an embodiment of the present invention. detailed description
  • the ethylene process vinyl acetate production process of the present invention mainly comprises an ethylene preparation stage (optional), a vinyl acetate synthesis section and a vinyl acetate rectification section.
  • the ethylene preparation section includes an ethylene synthesis system and an ethylene refining system.
  • the raw material ethanol is sent from the raw material tank to the ethanol tank 101, preheated by the ethanol preheater 102, and then enters the ethanol evaporation tank 103.
  • the ethanol heated by the heat exchanger 104 enters the heating furnace 105, is heated by the heating furnace, and is sent to the reactor 106. .
  • the ethylene condenser adopts the method of air condensation, which can save a large amount of circulating water.
  • the condensed gas-liquid mixture is separated in the gas-liquid separation tank 1 10, and the gas phase ethylene de-ethylene compressor 1 1 1 is sent to the outside of the boundary.
  • the wastewater treatment unit is processed.
  • the compressed ethylene is sent to the caustic scrubber 1 12 to remove C0 2 from the crude ethylene.
  • the crude ethylene from which C0 2 and the polar compound were removed was dried by a molecular sieve dryer 1 13 and then removed to an ethylene refining system.
  • the dried ethylene is cooled by the cooler 1 14 and sent to the dehydrohalide column 1 15 , and the demethanizer overhead gas is sent to 1 10 , and the bottom liquid is the ethylene which removes the light component impurities, and is sent to the ethylene purification tower 1 17.
  • the ethylene product from the top of the ethylene purification tower is cooled and sent to the vinyl acetate synthesis section.
  • Tower kettle The ethylene material containing heavy component impurities is sent to a heating furnace for combustion.
  • Fresh acetic acid is sent from the boundary zone to the ethylene recovery tower 201, and is in countercurrent contact with the gas at the top of the absorption tower.
  • the ethylene is recovered, and the inert gas such as N 2 is discharged from the top of the ethylene recovery tower to the flare system, and the tower liquid is sent to the acetic acid for evaporation. 202.
  • Fresh ethylene is mixed with the circulating gas at the outlet of the circulating gas compressor 204, and after being coupled with the high temperature reaction gas, the acetic acid evaporator is introduced, and the acetic acid evaporator is added to the top of the acetic acid evaporator, and the sprayed acetic acid from the ethylene recovery tower is added, and the heating is performed by the reboiler 203.
  • the amount of steam adjusts the temperature of the top of the acetic acid evaporator and controls the acetic acid content of the mixed gas of ethylene and acetic acid.
  • the gas at the top of the column is a mixed gas of ethylene and acetic acid.
  • the mixed gas of ethylene and acetic acid is distilled off from the top of the evaporator, it is preheated by the first heat exchanger 205 of the reaction gas, and then heated to the reaction temperature by high pressure steam through the circulating ethylene preheater 206.
  • the gas is mixed with oxygen in the oxygen mixer 207, it is fed to the bed of the vinyl acetate synthesis catalyst from the top of the synthesis reactor 208 for catalytic reaction.
  • the synthesis reactor is a tubular fixed bed reactor, and the materials ethylene, oxygen and acetic acid are chemically converted into vinyl acetate at 138 ⁇ 1 85 °C and 785 kPa (gauge pressure).
  • the tubes are pressurized water, relying on their heated vaporization in the synthesis reactor 208 and the vapor-liquid separation in the reactor drum 209 to form a thermosyphon natural circulation, removing the heat of reaction.
  • the low-pressure steam generated by the reactor steam drum at the initial stage of the operation of the vinyl acetate production unit is supercharged by steam mechanical recompression MVR technology, and the generated medium-pressure steam (pressure greater than 0.4 MPa, less than 0.8 MPa) is incorporated into the medium-pressure steam pipe network. It avoids the large amount of steam venting at the beginning of the operation of the device and effectively realizes the utilization of waste heat. After the steam pressure has reached the required level, the steam pipe network of the corresponding grade is incorporated.
  • the gas after the reaction contains, in addition to the desired product, vinyl acetate, a large amount of unconverted ethylene and acetic acid, carbon dioxide, water, oxygen and nitrogen. Since the ethylene single pass conversion is low during the synthesis of vinyl acetate, a large amount of unconverted ethylene must be recycled.
  • the reaction gas is first cooled by the first and second coolers 205, 210 of the reaction gas, and then further condensed by the air cooler 21 1 to a condensation temperature of 70-1 10 ° C. After condensation, the gas-liquid two phases are directly separated into the gas without separation. The column 212 is separated.
  • the gas separation tower is divided into upper, middle and lower sections.
  • a part of the reaction liquid of the tower kettle is cooled by the circulating water by the first cooler 213 of the separation tower, and a part of the reaction liquid is cooled into the lower part of the gas separation tower, and is in countercurrent contact with the rising gas to condense the acetic acid contained therein; the other part is passed through the second cooler of the separation tower.
  • 214 After cooling by low temperature water, enter the middle section of the gas separation tower and make countercurrent contact with the rising gas.
  • the acetic acid, vinyl acetate and the like contained therein are condensed; the top of the column is rinsed with fresh acetic acid to further recover vinyl acetate.
  • the circulating gas at the top of the tower is returned to the circulating gas compressor, and the mixture of the acetic acid and the VAC is sent to the rectification unit via the degassing tank 215 for VAC purification.
  • the first cooler 213 is a double-shell tube-and-tube heat exchanger.
  • the reaction proceeds smoothly.
  • a part of the sidestream gas is extracted from the circulating gas of the circulating gas compressor to be purified, and the gas is removed after removing carbon dioxide and other impurities.
  • the system is recycled.
  • the side stream gas refining includes a water washing column 217, an absorption column 218, and a desorption column 219.
  • the gas removed from the degassing tank is pressurized by the recovery gas compressor 216 and mixed with the side stream gas to enter the water washing tower, and is in countercurrent contact with the cold acetic acid introduced in the middle to recover the vinyl acetate therein.
  • the top of the washing tower is passed through pure water to rinse the rising gas to remove residual acetic acid.
  • the overhead gas is sent to the absorption tower, and the kettle liquid is used to recover the sealing liquid of the gas compressor group, and then mixed with the reaction liquid and sent to the rectification unit.
  • the gas discharged from the top of the washing tower enters the absorption tower 218, and the carbon dioxide therein is absorbed by a hot aqueous solution of potassium carbonate under pressure.
  • the refined gas from the top of the absorption tower is returned to the recycle gas compressor; a small portion is sent to the rectification unit as a polymerization inhibitor and preservative; the rest is sent to the ethylene recovery tower 201 to recover the ethylene and then discharged to balance the reaction system.
  • the inert gas concentration The absorption liquid in the absorption tower is sent to the top of the desorption column 219, and the carbon dioxide is desorbed under reduced pressure and elevated temperature.
  • the carbon dioxide gas is discharged from the top of the desorption tower, and the desorption tower is a desorbed potassium carbonate solution, and is returned to the absorption tower for use as an absorption liquid.
  • the vinyl acetate synthesis reaction solution contains acetic acid, water, low-boiling components and high-boiling components in addition to vinyl acetate, and needs to be separated by distillation.
  • the gas phase composition is different from the composition of the liquid phase, and the proportion of the volatile matter in the gas phase is larger than that of the volatile matter in the liquid phase.
  • the ratio can be separated and purified by means of precise methods.
  • Vinyl acetate rectification utilizes the difference in relative volatility of the components in the reaction mixture, and the components are separated by a series of rectification operations.
  • the vinyl acetate rectification unit mainly comprises an acetic acid column 301, a crude VAC column 302, a refined VAC column 303, a de-weighting column 304, an aldehyde ester concentration column 305, an acetaldehyde column 306, a dehydration column 307, and an acetic acid recovery column 308.
  • the reaction liquid from the vinyl acetate synthesis unit is degassed through the degassing tank 215, and then sent to the vinegar.
  • Acid column 301 separates acetic acid.
  • the acetic acid Tata kettle produces distilled acetic acid, most of which is sent to the acetic acid evaporator of the synthesis section, and the rest is sent to the gas separation tower and the water washing tower for washing acetic acid; the overhead vapor is condensed by the condenser, and the condensate is condensed again.
  • the liquid cooler 310 After the liquid cooler 310 is cooled, it enters the acetic acid column to distill off the phase separation tank 31 1 .
  • the acetic acid tower condensate cooler adopts a plate heat exchanger to realize full counterflow, increase the heat exchange temperature difference, and reduce the amount of cooling water.
  • the upper organic phase is partially refluxed and partially recovered to the crude VAC column 302.
  • the lower aqueous phase is sent to dehydration column 307 to recover the VAC therein.
  • the VAC tower kettle produces vinyl acetate containing no low boilers and sends it to the fine VAC tower 303; the overhead vapor is condensed by the condenser 312, and the condensate is cooled by the condensate cooler 313, and then enters the crude VAC tower to separate the phases.
  • Tank 314 is layered.
  • the coarse VAC tower condensate cooler uses a plate heat exchanger to achieve full counterflow, increase the heat transfer temperature difference, and reduce the amount of cooling water.
  • the upper organic phase is partially refluxed, partially recovered to the aldehyde ester concentration column 305, and the lower aqueous phase is sent to the dehydration column 307 to recover the VAC therein.
  • the refined VAC tower 303 is fed with a crude VAC tower liquid, and the high-boiling component is cut by rectification, and the high-purity vinyl acetate product is distilled from the top; the tower liquid is sent to the de-weighting tower 304.
  • the refined VAC is distilled from the top of the tower by means of rectification, partially refluxed, and partially sent to the crude VAC tower; the tower liquid is a vinyl acetate having a high concentration of heavy components and is sent to the waste liquid treatment system. Centralized processing.
  • the feed of the aldehyde ester concentration column 305 is the organic phase separated by the crude VAC column distillation phase separation tank 314, and the low-boiling component mainly composed of acetaldehyde is collected at the top of the aldehyde ester concentration tower, and after partial cooling by condensation cooling Part of the acetaldehyde column 306 is sent; the kettle liquid is sent to the top of the crude VAC column for reflux.
  • the aldehyde ester concentration tower tops the stream to the upper portion of the acetaldehyde column 306.
  • the acetaldehyde tower is steamed out of the bottom of the acetaldehyde tower. After condensation, part of it is used for the reflux of the top of the acetaldehyde tower, and part of the by-product acetaldehyde is produced.
  • the tower kettle is the remaining light component impurities and is sent to the waste liquid treatment system for centralized treatment.
  • the feed to the dehydration column 307 is the aqueous phase separated from the lower phase of each phase separation tank of the rectification unit. This portion of the material is preheated by the dehydration column feed preheater 322 and then enters the top of the dehydration column.
  • the dewatering tower feed preheater adopts a plate heat exchanger, which increases the heat exchange temperature difference, increases the feed temperature, and reduces the amount of fresh steam in the dehydrator reboiler.
  • the azeotrope of vinyl acetate and water is taken from the top of the dehydration tower, and after condensing, it is returned to the crude VAC tower to distill out the phase separation tank 314; the bottom waste water is exchanged with the feed water to be treated with waste water.
  • the acetic acid evaporator kettle liquid is sent to the acetic acid recovery column 308.
  • the acetic acid recovery tower adopts a forced circulation type reboiler, and the acetic acid distilled from the top of the column is partially refluxed after being condensed, and partially returned to the rectification unit; the column is a high boiling point impurity, a polymer and other solid materials, and is pumped to a high boiling waste. Liquid tank set Processing.

Abstract

本发明涉及生产醋酸乙烯的方法。本发明提供一种乙烯气相氧化生产醋酸乙烯的方法，其包括任选的乙烯制备过程，醋酸乙烯合成过程和醋酸乙烯精制过程，其中在所述乙烯制备过程，醋酸乙烯合成过程和醋酸乙烯精制过程的至少一个过程中使用以下至少之一：蒸汽机械再压缩技术，空气冷却器，板式换热器，和双壳程管壳式换热器。

Description

生产醋酸乙烯的方法 技术领域
本发明涉及生产醋酸乙烯的方法， 特别地涉及一种能耗得到降低 的生产醋酸乙烯的方法。 背景技术
醋酸乙烯（VAC)， 也称为醋酸乙烯酯， 是一种重要的有机化工原 料。 通过自身聚合或与其它单体共聚， 醋酸乙烯可以生成聚乙烯醇 (PVA)、 醋酸乙烯一乙烯共聚物（EVA)、 聚醋酸乙烯 (PVAC)、 醋酸乙烯 —氯乙烯共聚物 (EVC)等等产物。 这些产物的用途十分广泛， 一般可用 于粘接剂、 纸张或织物的上胶剂、 油漆、 墨水、 皮革加工、 乳化剂、 水溶性膜、 土壤改良剂等方面。
一般而言， 醋酸乙烯的生产工艺路线有乙烯法和乙炔法两种。 在 世界范围内， 目前乙烯法生产占主导地位。 乙烯法醋酸乙烯生产过程 是将原料乙烯、 氧气和醋酸气体送入反应器与催化剂接触， 在 0.5- 1.4MPa ( G ) 压力和 130 ~ 220 °C温度下反应生成 VA (：、 水及少量 副产物， 高温反应气体经过多级冷却、 冷凝后进入气体分离塔， 以达 到气液分离的目的。 未反应乙烯气体返回压缩机。 冷凝的醋酸和 VAC 混合液送精镏工序进行 VAC的精制。
乙烯法醋酸乙烯生产装置在运行初期， 反应器汽包在较长的时间 内只产生低压蒸汽。 由于低压蒸汽温度较低无法满足其它设备的加热 需求， 因此实际生产中这部分蒸汽被长期放空， 直至压力达到要求。 该放空时间依据反应器升温速度不同而不同， 少则 3-5个月， 多则 6-8 个月， 这造成了能量的巨大浪费。
此外， 对于醋酸乙烯生产装置反应器出口的高温反应气体， 一般 采用管壳式换热器对该高温反应气体进行多级冷却冷凝， 其中反应气 体冷凝器的管方为工艺介质， 壳方为冷却介质。 为了防止壳方结垢， 生产中是以无离子水为冷却介质。 这不仅造成无离子水的大量消耗， 并且还需要单独的无离子水冷却系统来提供符合温度的无离子水； 这 导致操作复杂并且设备投资较大。
一般地， 在乙烯法醋酸乙烯生产工艺中， 气体分离塔第一冷却器 采用多管程管壳式换热器， 无法实现全逆流操作， 需要消耗大量冷却 水。 另外， 乙烯法醋酸乙烯生产工艺的精馏段的醋酸塔凝液冷却器及 粗 VAC塔凝液冷却器都是要将塔顶物料过冷至 37 °C后进入分相器，分 离出的粗 VAC进入后续精馏塔进一步处理； 所采用的冷却器都是管壳 式换热器， 换热温差小， 冷却水消耗量大。
随着对节约能源， 提高能源利用效率的重视， 开发低能耗的醋酸 乙烯生产方法是非常有利的。
本发明的一个目的就在于提供一种醋酸乙烯生产方法， 该方法通 过对过程的集成与强化， 改变与优化工艺流程， 减少蒸汽及循环水的 用量， 大幅度降低醋酸乙烯生产的能耗。 发明内容
一般地， 本发明涉及一种生产醋酸乙烯的方法， 特别是乙烯气相 氧化生产醋酸乙烯的方法。
根据本发明的一个方面， 本发明涉及一种乙烯气相氧化生产醋酸 乙烯的方法， 其包括任选的乙烯制备过程， 醋酸乙烯合成过程和醋酸 乙烯精制过程。
一般地， 在本发明的乙烯气相氧化生产醋酸乙烯的方法中， 乙烯、 氧气和醋酸在醋酸乙烯合成反应器中在催化剂的作用下转变为醋酸乙 烯。
对于所述催化剂， 可以使用本领域中已知的用于乙烯气相氧化生 产醋酸乙烯的催化剂， 例如 USI催化剂和 Bayer催化剂。 本领域技术 人员理解， 也可以使用其它能够实现乙烯气相氧化生产醋酸乙烯的催 化剂。根据本发明的一个优选实施方案， 本发明的方法使用 Bayer催化 剂。 关于所述催化剂的详细描述， 可参见 《乙烯衍生物工学》 , 第九 章， 第 9.2.1节， 化学工业出版社， 1995年 7月， 其全部并入本文作为 参考。
对于用于乙烯、 氧气和醋酸反应来制备醋酸乙烯的反应器， 可以 使用本领域中已知的用于乙烯气相氧化生产醋酸乙烯的反应器。 例如， 可以使用 《乙烯衍生物工学》 , 第九章， 第 9.3.3节， 化学工业出版社， 1995年 7月， 中描述的反应器。
本发明的方法使用的原料之一是乙烯。 该乙烯可以是商购的乙烯， 例如来自石油化工厂或者其他来源。
作为选择， 在本发明的一个实施方案中， 所述乙烯可以是在本发 明的方法中的乙烯生产段（即乙烯制备过程） 中由乙醇制备的。 例如，
CN101798265A公开了一种由生物乙醇制备醋酸乙烯的方法，其全部内 容并入本文作为参考。
一般地， 所述乙烯生产段包括乙烯合成系统和乙烯精制系统。 首 先， 原料乙醇被送入反应器。 例如， 原料乙醇自原料罐区送入乙醇罐， 经乙醇预热器预热后进入乙醇蒸发罐， 经过热器过热后的乙醇进入加 热炉， 经加热炉加热后送入反应器。 例如， 乙烯制备所使用的反应器 可以是具有三个固定床的反应器， 在反应器中乙醇直接与催化剂床层 接触， 脱水生成乙烯， 同时温度沿床层方向降低。 根据一个实施方案， 该反应可以为气相反应， 反应温度范围为约 47CTC〜约 358 °C , 所使用 的催化剂主要组分为 γ -Α1203。 该反应为吸热过程， 反应中所需的热量 可以由过热蒸汽与反应物乙醇直接接触提供。 本发明对于乙醇到乙烯 的转化没有特别的限制， 可以使用任何合适的反应类型以及反应器， 只要能够实现由乙醇得到乙烯。
反应后的反应生成物然后被冷却。 例如反应生成物经与过热乙醇 换热、 作为乙醇蒸发罐的加热介质及与原料乙醇换热这三级耦合换热 而被冷却。 冷却后的反应生成物被送至乙烯冷凝器进一步冷凝。 根据 一个优选的实施方案， 该乙烯冷凝器可采用空气冷凝的方式 （即使用 空气冷却器） 。 空气冷却器出口温度为约 40 -约 50 °C , 最优选约 45 °C。 在采用空气冷凝方式时， 以空气 (例如环境空气)作为冷却介质替代 循环水对反应生成物进一步冷凝， 从而能够节约大量循环水。 空气冷 却器是本领域技术人员已知的； 例如可以使用本文后面详细介绍的空 气冷却器。
冷凝后的气液混合物在气液分离罐中进行分离以得到气相乙烯和 液相废水。 得到的气相乙烯然后可以进一步进行处理以得到用于制备 醋酸乙烯的乙烯。 对于处理气相乙烯， 本发明没有任何限制， 只要能 够得到能够用于制备醋酸乙烯的乙烯。
例如， 气相乙烯送到乙烯压缩机， 液相废水送到界区外的废水处 理装置进行处理。经过压缩后的乙烯送至碱洗塔，除去粗乙烯中的 co2。 脱除 co2和极性化合物的粗乙烯经分子筛干燥器干燥后送到乙烯精制 系统。 千燥后的乙烯经冷却器冷却后送入脱曱烷塔， 脱甲烷塔塔顶气 送至气液分离罐， 塔釜液为脱除轻组分杂质的乙烯， 送入乙烯提纯塔。 乙烯提纯塔塔顶采出乙烯产品经冷却后送至醋酸乙烯合成段。 塔釜为 含有重杂质的乙烯物料， 可送至加热炉燃烧。
在本发明的生产醋酸乙烯的方法中， 乙烯在醋酸乙烯反应器中只 是部分转化， 这导致大量未转化的乙烯需要循环使用。 因此， 根据一 个实施方案， 来自乙烯源或来自乙烯生产段的新鲜乙烯， 任选地与循 环的乙烯混合， 然后被预热， 并从底部进入醋酸蒸发器。 根据一个实 施方案， 所述预热可以采用醋酸乙烯合成反应器的出口气体进行。
在醋酸蒸发器中， 醋酸由顶部进行喷淋， 在该蒸发器内乙烯和醋 酸逆流接触， 蒸发器顶部引出乙烯和醋酸的混合气体。 该混合物气体 中的醋酸含量可以通过控制该蒸发器的顶部温度实现。
乙烯和醋酸的混合气体从醋酸蒸发器顶部出来后， 首先进行预热。 例如， 可以先用醋酸乙烯反应器出口气体进行加热， 然后再用蒸汽进 一步加热。 加热后的混合气体被送入氧气混合器与氧气混合。 关于该 氧气混合器， 其是本领域公知的， 并且可以采用本领域公知的各种氧 气混合器。 例如在 《乙烯衍生物工学》 , 第九章， 第 590-591 页， 化学 工业出版社， 1995年 7月， 就公开了一种常用的氧气混合器； 本发明 可以采用这种氧气混合器。
从氧气混合器出来的混合气体被从顶部送入醋酸乙烯合成反应 器。 如上所述， 可以使用本领域中已知的用于乙烯气相氧化生产醋酸 乙烯的反应器。 根据一个实施方案， 所述醋酸乙婦合成反应器例如可 以为列管式固定床反应器。 乙烯、 氧气和醋酸在反应器中在催化剂的 作用下转变为醋酸乙烯。 如上所述， 所述催化剂可以是例如 USI催化 剂和 Bayer催化剂。 根据本发明的一个优选实施方案， 使用 Bayer催化 剂。 根据一个实施方案， 所述 Bayer催化剂的活性成分是钯和金； 载体 一般为硅胶。 根据一个实施方案， 反应温度为约 138-约 1 85 °C , 压力一 般为约 785kPa (表压） 。 本领域技术人员理解， 本发明的方法对所用 催化剂、 载体、 温度和压力没有特殊要求， 只要能够实现以气相法由 乙烯、 氧气和醋酸得到醋酸乙烯即可。
在一个实施方案中， 醋酸乙烯合成反应器为列管式固定床反应器， 在所述列管式固定床反应器的管间为加压水， 其用于移除反应热并产 生蒸汽。 根据一个实施方案， 在本发明的醋酸乙烯生产方法中， 所述 列管式固定床反应器在运行初期只产生低压蒸汽。 一般地该低压蒸汽 的压力小于约 0.4MPa。 根据一个有利的实施方案， 对该低压蒸汽采用 蒸汽机械再压缩 MVR技术进行处理。 根据一个实施方案， 通过 MVR 技术产生中压蒸汽， 一般地该中压蒸汽压力大于约 0.4MPa, 小于约 0.8MPa。通过采用蒸汽机械再压缩 MVR技术， 避免了运行初期低压蒸 汽的大量放空， 有效的实现废热利用。 MVR技术是一种新型高效节能 技术， 其工作原理是将废热蒸汽经机械式蒸汽压缩机作用， 使其温度、 压力、 焓值均得到提升后作为热源用于加热其它设备， 从而有效回收 废热蒸汽的潜热， 达到节能降耗的目的。 关于 MVR技术， 可以参考以
Figure imgf000007_0001
反应后得到的气体除含有目标产物醋酸乙烯外， 还含有大量未转 化的乙烯和醋酸， 以及二氧化碳、 水、 氧气和氮气等。 由于在醋酸乙 烯的合成过程中， 乙烯单程转化率较低， 因此大量未转化的乙烯必须 循环使用。 离开反应器的反应后气体可以首先经反应气第一冷却器（可 用于加热乙烯和醋酸混合气体） 和第二冷却器 （可用于加热进料乙烯 气体） 与原料气体进行换热， 回收产物气体中所带出的热量， 进行冷 却。
之后， 经第一和第二冷却器冷却的反应气体进入水冷凝器， 用冷 却水将其进一步冷却， 使其中所含的醋酸和醋酸乙烯等组分冷凝。
根据本发明方法的一个优选实施方案， 经第一和第二冷却器冷却 的反应气体进入空气冷却器进行进一步冷却。 根据一个实施方案， 空 气冷却器的冷凝液出口温度为约 70-约 U 0 °C。 空气冷却器是以环境空 气作为冷却介质的冷却器， 简称 "空冷器" 。 在此可以使用各种已知 的空气冷却器。 本领域技术人员知道并掌握如何选择合适的空气冷却 器来满足冷却需要。 例如， 在一种类型的空气冷却器中， 利用动力带 动叶轮转动， 产生的涡流不断将空气吸入， 冷空气与热管道接触后传 递热量， 使管内高温工艺流体得到冷却或冷凝。 例如， 空冷器可以通 过配置调频电机和调节扇叶角度来调节制冷量。 一种常见的空冷器主 要由管束、 风机和构架三部分组成。 例如， 国标 GB/T 15386-94对空冷 器的结构及性能要求等进行了详细说明。 由于反应后的气体中含有大量的不冷凝组分， 如乙烯、 氧气等等， 因此只借助于间接冷却的方法， 很难将醋酸和醋酸乙烯全部冷凝下来。 如果分离得不彻底， 就可能使循环的乙烯中含有醋酸， 即使是很微量 的醋酸存在也会导致循环气压缩机受到腐蚀。 因此， 一般地， 醋酸乙 烯生产中要使用直接冷却设备-气体分离塔。
根据本发明的一个实施方案， 在使用如上所述的空气冷却器冷凝 后， 反应气体的气液两相不经分离直接进入气体分离塔下段。 根据本 发明的另一个实施方案， 采用水冷凝器时气液两相可以经过气液分离 后分别进入气体分离塔。
一般地， 气体分离塔分上、 中、 下三段。 下段用冷却水冷却后的 塔釜反应液循环， 与上升的乙烯、 二氧化碳、 醋酸、 醋酸乙烯等气体 逆流接触， 将其中所含醋酸冷凝下来； 中段用低温水（例如冷冻盐水、 甲醇水溶液等） 冷却后的反应液循环， 与上升气体逆流接触， 将其中 所含醋酸、 醋酸乙烯等高沸点物质冷凝下来； 上段用醋酸淋洗气体。
具体而言， 气体分离塔塔釜液经气体分离塔第一冷却器冷却后一 部分进入分离塔下段， 另一部分再经气体分离塔第二冷却器用低温水 进一步冷却后进入气体分离塔中段， 分别与上升气体逆流直接接触， 使气相中的醋酸、 VAC冷凝。
根据本发明的一个有利的实施方案， 所述气体分离塔第一冷却器 采用板式换热器或双壳程管壳式换热器， 例如双壳程固定管壳式换热 器。 根据本发明的一个特别有利的实施方案， 所述气体分离塔第一冷 却器采用双壳程管壳式换热器， 例如双壳程固定管壳式换热器。 不受 任何理论限制， 据信双壳程管壳式换热器的使用实现了冷热介质的全 逆流操作， 节约了冷却水。 可以使用本领域中已知的任何双壳程管壳 式换热器或双壳程固定管壳式换热器， 只要其能实现所需的冷却效果。 本领域技术人员知道并掌握如何选择合适的双壳程管壳式换热器或双 壳程固定管壳式换热器来满足冷却需要。 如本领域技术人员通常已知 的那样， 双壳程管壳式换热器是在管束中心放置一块隔板， 折流板被 上下隔开， 壳程被一分为二。 由于壳体被中间隔板分成两部分， 能实 现冷、 热流介质在纯逆流条件下进行热交换， 传热效率远大于单壳程 管壳式换热器。 不受任何理论限制， 据信板式换热器的使用实现了全 逆流， 增大了换热温差， 减少了冷却水用量。 板式换热器是由一系列 具有一定波纹形状的金属片叠装而成的一种新型高效换热器。 各种板 片之间形成薄矩形通道， 通过板片进行热量交换。 它与常规的管壳式 换热器相比， 传热系数要高出很多。 板式换热器对数平均温差大， 末 端温差小， 能够实现全逆流换热。 可以使用本领域中已知的任何板式 换热器， 只要其能实现所需的冷却效果。 本领域技术人员知道并掌握 如何选择合适的板式换热器
从气体分离塔顶部出来的气体， 基本不含醋酸、 醋酸乙烯等高沸 点组分； 其主要组成为乙烯、 二氧化碳和氧气。 一般地， 该气体经循 环气压缩机压缩后， 大部分循环返回醋酸乙烯合成反应器； 另外抽出 一小部分去脱除二氧化碳等惰性组分， 以确保乙烯浓度不致因惰性组 分积聚而降低， 从而使合成反应得以顺利进行。
一般地，从气体分离塔塔釜连续采出一定量的液体作为反应液（醋 酸和醋酸乙烯混合液） ， 送往脱气槽。 借助于减低压力使溶解在液相 中的气体解吸出来， 通过回收气体压缩机压缩后， 和送去脱除二氧化 碳的气体合并送入水洗塔。
一般地， 送入水洗塔中的气体通过水洗， 将其中含有的醋酸及乙 醛除去后， 送入吸收塔中以热碳酸钾水溶液吸收其中的二氧化碳， 从 成 应器； 小部分送至精 单元: 作为阻聚剂及防腐剂； 余送 乙烯回收塔回收其中的乙烯后放至火炬烧掉， 以平衡反应系统中的惰 性气体。 吸收塔底部的吸收液可以送至解吸塔， 在减压及升温条件下 使二氧化碳解吸， 二氧化碳由解吸塔排出； 解吸后的碳酸钾溶液， 重 新返回吸收塔做吸收液使用。
如本领域技术人员理解的那样， 醋酸乙烯合成反应液中， 除含有 醋酸乙烯外， 还含有醋酸、 水、 低沸点组分及高沸点组分。 对于各组 分沸点存在明显差异的液体混合物， 在一定的温度下部分汽化后， 其 气相组成不同于液相的组成， 气相中易挥发物质所占的比例大于液相 中易挥发物质所占的比例， 可借助精馏的方法进行分离纯化。 一系歹 的精馏操作使其各组份得到分^。 ' 一般地， 醋酸乙烯精镏段 （醋酸乙烯精制过程） 包括醋酸塔、 粗
VAC塔、 精 VAC塔、 脱重塔、 醛酯浓缩塔、 乙醛塔、 脱水塔及醋酸 回收塔。
来自醋酸乙烯合成段脱气槽（例如如上所述）的反应液作为进料， 送入醋酸塔。 根据一个实施方案， 塔底采出回收醋酸， 其大部分送至 醋酸乙烯合成段的醋酸蒸发器， 其余部分分别送至气体分离塔和水洗 塔用作淋洗醋酸。
在醋酸塔顶部引出蒸气， 该蒸气主要组分为醋酸乙烯和水。 根据 一个实施方案， 该蒸气经冷凝器冷凝后， 送入醋酸塔分相罐进行分层。 上层有机相一部分回流， 一部分采出送至粗 VAC塔， 下层水相送至脱 水塔。
根据一个有利的实施方案， 醋酸塔的塔顶蒸气先经冷凝器冷凝， 凝液再经凝液冷却器冷却后， 进入醋酸塔分相罐分层。 根据一个特别 有利的实施方案， 醋酸塔的凝液冷却器采用板式换热器或双壳程管壳 式换热器， 优选采用板式换热器。 不受任何理论限制， 据信板式换热 器或双壳程管壳式换热器的使用实现了全逆流， 增大了换热温差， 减 少了冷却水用量。 可以使用本领域中已知的任何板式换热器或双壳程 管壳式换热器， 只要其能实现所需的冷却效果。 本领域技术人员知道 并掌握如何选择合适的板式换热器或双壳程管壳式换热器。 例如， 可 以使用前面关于气体分离塔所描述的板式换热器或双壳程管壳式换热 器。
根据一个实施方案， 醋酸塔的分相罐的部分有机相被送至粗 VAC 塔。 该粗 VAC塔是精馏塔， 用于分离出溶解在醋酸乙烯中的水及低沸 点杂质。 在粗 VAC塔塔釜取出的是不含低沸物的醋酸乙烯， 并被送至 精 VAC塔。
根据一个实施方案， 粗 VAC塔塔顶蒸出水、 低沸点组分以及少量 醋酸乙烯， 在经冷凝器冷凝后， 进入粗 VAC塔分相罐分层。 上层有机 相为醋酸乙烯及低沸点组分， 部分回流， 部分送至醛酯浓缩塔； 下层 水相送至脱水塔回收其中的 VAC。
根据一个有利的实施方案，粗 VAC塔的所述塔顶蒸气先经冷凝器 冷凝， 凝液再经凝液冷却器冷却后， 进入粗 VAC塔分相罐分层。 根据 一个特别有利的实施方案， 粗 VAC塔凝液冷却器采用板式换热器或双 壳程管壳式换热器， 优选采用板式换热器。 可以使用本领域中已知的 任何板式换热器或双壳程管壳式换热器， 只要其能实现所需的冷却效 果。 本领域技术人员知道并掌握如何选择合适的板式换热器或双壳程 管壳式换热器。 例如， 可以采用与前面描述的相同的板式换热器或双 壳程管壳式换热器。 据信， 采用板式换热器或双壳程管壳式换热器后， 能够实现全逆流， 增大换热温差， 减少冷却水用量。
粗 VAC塔的塔釜液被送至精 VAC塔进料。该精 VAC塔用于除掉 高沸点组分。 在该精 VAC塔的塔顶蒸出纯醋酸乙烯， 冷凝后可以送入 储槽。 塔釜液为醋酸乙烯及高沸点组分， 被送往脱重塔。
在脱重塔中， 借助于精馏作用从塔顶蒸出精 VAC , 部分回流， 部 分送至粗 VAC塔； 塔釜液为重组分杂质浓度较高的醋酸乙烯， 送至废 液处理系统集中处理。
醛酯浓缩塔的进料是粗 VAC塔分相罐分出的有机相。在该醛酯浓 缩塔的塔顶蒸出以乙醛为主的低沸点组分， 其经冷凝冷却后， 部分回 流， 部分送乙醛塔； 塔釜液主要包含醋酸乙烯， 送至粗 VAC塔进行塔 顶回流。 在乙醛塔塔顶蒸出纯乙醛， 例如浓度可达至少约 99%。 在经 冷凝器冷凝后， 得到副产物乙醛。 该乙醛塔塔底为剩余轻杂质组分， 送往废液处理装置进行处理。
由上述醋酸塔分相罐和粗 VAC塔分相罐下层水相分离出的水，其 中溶解有一定量的醋酸乙烯。 为了回收醋酸乙烯， 将这部分物料送至 脱水塔。 从该脱水塔塔顶蒸出醋酸乙烯和水的恒沸物， 经冷凝器冷凝 后， 返回上述粗 VAC塔分相罐分层。 该脱水塔的塔底物料为几乎不含 醋酸乙烯的水， 经废水处理后排放。
根据一个特别有利的实施方案，上述醋酸塔分相罐和粗 VAC塔分 相罐下层水相分离出的水物料经预热后进入脱水塔。 根据一个特别优 选的实施方案， 该水物料的预热采用脱水塔的塔底物料进行， 其中该 预热使用板式换热器或双壳程管壳式换热器实施， 优选使用板式换热 器实施。 可以使用本领域中已知的任何板式换热器或双壳程管壳式换 热器， 只要其能实现所需的冷却效果。 本领域技术人员知道并掌握如 何选择合适的板式换热器或双壳程管壳式换热器。 例如， 可以采用与 前面描述的相同的板式换热器或双壳程管壳式换热器。 据信， 通过采 用板式换热器或双壳程管壳式换热器， 实现了冷热介质的全逆流操作， 增大了换热温差， 提高了进料温度， 减少了脱水塔再沸器新鲜蒸汽用 量。 如本领域技术人员理解的那样， 回收的循环醋酸中， 如果含有沸 点高于醋酸的杂质， 它们就会在醋酸蒸发器的底部积聚。 为此， 需要 将这部分釜液定期取出， 送至醋酸回收塔。 醋酸回收塔采用强制循环 式再沸器， 塔顶蒸出的醋酸， 经冷凝后部分回流， 部分返回精馏单元； 塔釜为高沸点杂质、 聚合物及其它固态物料， 塔釜残液经泵送至高沸 废液罐集中处理。 附图说明
图 1 示出了根据本发明的一个实施方案的乙烯制备段的流程示意 图。
图 2 示出了根据本发明的一个实施方案的醋酸乙烯合成段的流程 示意图。
图 3 示出了根据本发明的一个实施方案的醋酸乙烯精馏段的流程 示意图。 具体实施方式
本发明的乙烯法醋酸乙烯生产方法主要包括乙烯制备段（任选）、 醋酸乙烯合成段和醋酸乙烯精馏段。 下面， 将结合附图对上述各段进 行描述。
1 . 乙烯制备段
乙烯制备段包括乙烯合成系统和乙烯精制系统。 原料乙醇自原料 罐区送入乙醇罐 101 , 经乙醇预热器 102预热后进入乙醇蒸发罐 103 , 经过热器 104过热后的乙醇进入加热炉 105 ,经加热炉加热后送入反应 器 106。 反应生成物经多级冷却后， 送至乙烯冷凝器 109进一步冷凝。 乙烯冷凝器采用空气冷凝的方式， 能够节约大量循环水， 冷凝后的气 液混合在气液分离罐 1 10中进行分离， 气相乙烯去乙烯压缩机 1 1 1， 液 相废水送到界区外的废水处理装置进行处理。 经过压缩后的乙烯送至 碱洗塔 1 12 , 除去粗乙烯中的 C02。 脱除 C02和极性化合物的粗乙烯经 分子筛干燥器 1 13干燥后去乙烯精制系统。
干燥后的乙烯经冷却器 1 14冷却后送入脱曱烷塔 1 15 ,脱甲烷塔塔 顶气送至 1 10 ,塔釜液为脱除轻组分杂质的乙烯，送入乙烯提纯塔 1 17。 乙烯提纯塔塔顶采出乙浠产品经冷却后送至醋酸乙烯合成工段。 塔釜 为含有重组分杂质的乙烯物料， 送至加热炉燃烧。
2. 醋酸乙烯合成段
新鲜醋酸自界区外送至乙烯回收塔 201 ,与吸收塔塔顶气体逆流接 触， 回收其中的乙烯， N2等惰性气体由乙烯回收塔塔顶排出至火炬系 统， 塔釜液送至醋酸蒸发器 202。
新鲜乙烯在循环气体压缩机 204 出口与循环气体混合， 经与高温 反应气耦合换热后， 进入醋酸蒸发器， 醋酸蒸发器顶部加入来自乙烯 回收塔的喷淋醋酸， 通过再沸器 203 的加热蒸汽量调节醋酸蒸发器的 塔顶温度， 控制乙烯和醋酸混合气体中的醋酸含量。 塔顶气体为乙烯 和醋酸的混合气体。
乙烯和醋酸的混合气体从蒸发器顶部蒸出后， 先经反应气第一热 交换器 205预热， 而后再经循环乙烯预热器 206用高压蒸汽加热到反 应温度。 该气体在氧气混合器 207中与氧气混合后， 由合成反应器 208 顶部送入醋酸乙烯合成催化剂床层进行催化反应。 合成反应器为列管 式固定床反应器， 物料乙烯、 氧气和醋酸在 138〜1 85 °C、 785kPa (表压) 下进行化学反应转变成醋酸乙烯。 管间为加压水， 依靠其在合成反应 器 208 中的受热汽化和在反应器汽包 209 中的汽液分离构成热虹吸自 然循环， 移除反应热。 对醋酸乙烯生产装置运行初期反应器汽包产生 的低压蒸汽， 采用蒸汽机械再压缩 MVR技术进行增压， 所产生的中压 蒸汽（压力大于 0.4MPa, 小于 0.8MPa )并入中压蒸汽管网， 避免了装 置运行初期蒸汽的大量放空， 有效的实现废热利用。 待蒸汽压力达到 要求后并入相应等级的蒸汽管网。
反应后的气体除含有目的产物醋酸乙烯外， 还含有大量未转化的 乙烯和醋酸， 以及二氧化碳、 水、 氧气和氮气等。 由于在醋酸乙烯的 合成过程中， 乙烯单程转化率较低， 因此大量未转化的乙烯必须循环 使用。 反应气体首先经反应气第一和第二冷却器 205、 210冷却， 而后 经空气冷却器 21 1 进一步冷凝， 冷凝温度为 70- 1 10 °C , 冷凝后气液两 相不经分离直接进入气体分离塔 212。
气体分离塔分上、 中、 下三段。 塔釜的部分反应液经分离塔第一 冷却器 213 由循环水冷却后， 一部分进入气体分离塔下段， 与上升气 体逆流接触， 将其中所含醋酸冷凝下来； 另一部分经分离塔第二冷却 器 214 由低温水冷却后， 进入气体分离塔中段与上升气体逆流接触， 将其中所含醋酸、 醋酸乙烯等物质冷凝下来； 塔顶加入新鲜醋酸淋洗， 进一步回收其中的醋酸乙烯。 塔顶的循环气体返回循环气体压缩机， 釜液为醋酸和 VAC混合液经脱气罐 215送精馏单元进行 VAC的精制。 该第一冷却器 213是双壳程管壳式换热器。
为防止氮气及副反应生成的二氧化碳等不凝气体累积后降低乙烯 浓度影响反应的顺利进行， 从循环气体压缩机出口循环气中抽出一部 分侧流气体进行精制， 除去二氧化碳和其他杂质后的气体返回系统循 环使用。 侧流气精制包括水洗塔 217、 吸收塔 218和解吸塔 219。
脱气罐中脱除的气体经回收气体压缩机 216增压后与侧流气体混 合进入水洗塔塔釜， 与在中部通入的冷醋酸逆流接触， 以回收其中的 醋酸乙烯。 水洗塔塔顶通入纯水对上升气体进行淋洗， 以除去其中的 残余醋酸。 塔顶气送至吸收塔， 釜液用于回收气体压缩机组的封液， 而后与反应液混合送至精馏单元。
水洗塔塔顶排出的气体进入吸收塔 218 中， 在加压条件下用热碳 酸钾水溶液吸收其中的二氧化碳。 从吸收塔顶部出来的精制气体， 返 回循环气体压缩机； 小部分送至精馏单元， 作为阻聚剂及防腐剂； 其 余送至乙烯回收塔 201 回收其中的乙烯后排放， 以平衡反应系统中的 惰性气体浓度。 吸收塔塔釜的吸收液送至解吸塔 219 顶， 在减压及升 温条件下使二氧化碳解吸。 二氧化碳气体由解吸塔塔顶排出， 解吸塔 塔釜为解吸后的碳酸钾溶液， 重新返回吸收塔作吸收液使用。
3. 醋酸乙烯精熘段
醋酸乙烯合成反应液中， 除含有醋酸乙烯外， 还含有醋酸、 水、 低沸点组分及高沸点组分， 需采用精馏技术进行分离。
对于各组分沸点存在明显差异的液体混合物， 在一定的温度下部 分汽化后， 其气相组成不同于液相的组成， 气相中易挥发物质所占的 比例大于液相中易挥发物质所占的比例， 可借助精镏的方法进行分离 纯化。 醋酸乙烯精馏就是利用反应液中各组份相对挥发度的差异， 通 过一系列的精馏操作使其各组份得到分离。
醋酸乙烯精馏单元主要包括醋酸塔 301、 粗 VAC塔 302、 精 VAC 塔 303、 脱重塔 304、 醛酯浓缩塔 305、 乙醛塔 306、 脱水塔 307及醋 酸回收塔 308。
来自醋酸乙烯合成单元的反应液， 经脱气罐 215脱气后， 送入醋 酸塔 301 进行醋酸的分离。 醋酸塔塔釜采出蒸馏醋酸， 大部分送至合 成工段的醋酸蒸发器， 其余部分分别送至气体分离塔和水洗塔用作淋 洗醋酸； 塔顶蒸气经冷凝器冷凝， 凝液再经凝液冷却器 310 冷却后， 进入醋酸塔馏出分相罐 31 1。 醋酸塔凝液冷却器采用板式换热器， 实现 全逆流， 增大换热温差， 减少冷却水用量。 上层有机相部分回流， 部 分采出送至粗 VAC塔 302。下层水相送至脱水塔 307回收其中的 VAC。
VAC塔釜采出不含低沸物的醋酸乙烯经送至精 VAC塔 303 ; 塔顶蒸气 经冷凝器 312冷凝， 凝液再经凝液冷却器 313冷却后， 进入粗 VAC塔 馏出分相罐 314分层。 粗 VAC塔凝液冷却器采用板式换热器， 实现全 逆流， 增大换热温差， 减少冷却水用量。 上层有机相部分回流， 部分 采出送至醛酯浓缩塔 305 , 下层水相送至脱水塔 307回收其中的 VAC。
精 VAC塔 303以粗 VAC塔塔釜液为加料， 通过精馏切除高沸点 组分， 由塔顶蒸出高纯度醋酸乙烯产品； 塔釜液送脱重塔 304。
在脱重塔 304中，借助于精馏作用从塔顶蒸出精 VAC ,部分回流， 部分送至粗 VAC塔； 塔釜液为重组分杂质浓度较高的醋酸乙烯， 送至 废液处理系统集中处理。
醛酯浓缩塔 305 的进料是粗 VAC塔馏出分相罐 314分出的有机 相， 醛酯浓缩塔塔顶采出以乙醛为主的低沸点组分， 经冷凝冷却后， 部分回流， 部分送乙醛塔 306; 釜液送至粗 VAC塔塔顶回流。
醛酯浓缩塔塔顶采出流股进入乙醛塔 306 上部。 乙醛塔塔顶蒸出 乙酪蒸汽， 经过冷凝后， 部分用于乙醛塔塔顶回流， 部分采出副产品 乙醛。 塔釜为剩余的轻组分杂质， 送至废液处理系统集中处理。
脱水塔 307 的进料为精馏单元各分相罐下层分出的水相， 这部分 物料经脱水塔进料预热器 322 预热后进入脱水塔顶部。 脱水塔进料预 热器采用板式换热器， 增大了换热温差， 提高进料温度， 减少脱水塔 再沸器新鲜蒸汽用量。 脱水塔塔顶采出醋酸乙烯和水的恒沸物， 经冷 凝后， 返回粗 VAC塔馏出分相罐 314; 塔底废水与进料换热后去废水 处理。
醋酸蒸发器釜液送至醋酸回收塔 308。醋酸回收塔采用强制循环式 再沸器， 塔顶蒸出的醋酸， 经冷凝后部分回流， 部分返回精馏单元； 塔釜为高沸点杂质、 聚合物及其它固态物料， 经泵送至高沸废液罐集 中处理。
尽管已经结合特定实施方案和附图描述了本发明， 但是本发明并 不预期限于本文所述的特定形式。 相反地， 本发明的范围仅由所附权 利要求限制。 此外， 尽管单独的特征可以包含在不同的权利要求中， 但是这些特征可以有利地进行组合， 并且包含在不同的权利要求中并 不意味着特征的组合不是可行的和 /或有利的。 对 "第一" 、 "第二" 等的引用并没有排除复数。

Claims

权 利 要 求
1. 一种乙烯气相氧化生产醋酸乙烯的方法， 其包括醋酸乙烯合成 过程和醋酸乙烯精制过程， 其中在所述醋酸乙烯合成过程和醋酸乙烯 精制过程的至少一个过程中使用以下至少之一： 蒸汽机械再压缩技术， 空气冷却器， 板式换热器， 和双壳程管壳式换热器。
2. 根据权利要求 1的方法， 其中在醋酸乙烯合成过程中， 乙烯、 氧气和醋酸在醋酸乙烯合成反应器中在催化剂的存在下转变为醋酸乙 烯， 其特征在于从该醋酸乙烯合成反应器取出的反应后的气体经第一 冷却器和第二冷却器冷却， 然后进入空气冷却器进行进一步冷却。
3. 根据权利要求 2的方法， 其中所述空气冷却器的冷凝液出口温 度为约 70-约 uo°c。
4. 根据权利要求 2或 3的方法，其中使用所述空气冷却器冷凝后， 反应后的气体的气液两相不经分离直接进入气体分离塔， 其中该气体 分离塔塔釜液经气体分离塔第一冷却器冷却后一部分进入分离塔下 段， 另一部分再经气体分离塔第二冷却器进一步冷却后进入气体分离 塔中段， 其特征在于所述气体分离塔第一冷却器是双壳程管壳式换热 器或板式换热器， 优选双壳程管壳式换热器。
5. 根据权利要求 1 的方法， 其中在醋酸乙烯合成过程中， 从醋酸 体分离塔， 其^该气体分离 ^塔釜液经气体 ^离塔第一冷却器冷却后 一部分进入分离塔下段， 另一部分再经气体分离塔第二冷却器进一步 冷却后进入气体分离塔中段， 其特征在于所述气体分离塔第一冷却器 是双壳程管壳式换热器或板式换热器， 优选双壳程管壳式换热器。
6. 根据权利要求 1 - 5 任一项的方法， 其中所述醋酸乙烯精制过 程包括醋酸塔和粗 VAC塔，其特征在于醋酸塔凝液冷却器和 /或粗 VAC 塔凝液冷却器是板式换热器或双壳程管壳式换热器， 优选板式换热器。
7. 根据权利要求 1 -6任一项的方法， 其中所述醋酸乙烯合成过程 包括醋酸乙烯合成反应器， 该醋酸乙烯合成反应器是列管式固定床反 应器， 其特征在于对所述列管式固定床反应器在运行初期产生的低压 蒸汽采用蒸汽机械再压缩 MVR技术进行处理。
8. 根据权利要求 1 -7任一项的方法， 其中还包括乙烯制备过程。
9. 根据权利要求 8的方法， 其中所述乙烯制备过程包括乙烯反应 器， 其中来自乙烯反应器的反应生成物经多级冷却后被送至乙烯冷凝 器进一步冷凝， 其特征在于该乙烯冷凝器采用空气冷却器。
10. 根据权利要求 1 - 9任一项的方法， 其中所述醋酸乙烯精制过 程包括醋酸塔和粗 VAC塔， 所述醋酸塔的分相罐和 /或粗 VAC塔的分 相罐的下层水相经预热后进入脱水塔， 该水相的预热采用脱水塔的塔 底物料进行， 其中该预热使用板式换热器或双壳程管壳式换热器实施， 优选使用板式换热器实施。
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