CN101239898A - Method for preparing pure terephthalic acid with purity more than 99.98wt% by using high efficiency dehydration filtering machine - Google Patents
Method for preparing pure terephthalic acid with purity more than 99.98wt% by using high efficiency dehydration filtering machine Download PDFInfo
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- CN101239898A CN101239898A CNA2007100068502A CN200710006850A CN101239898A CN 101239898 A CN101239898 A CN 101239898A CN A2007100068502 A CNA2007100068502 A CN A2007100068502A CN 200710006850 A CN200710006850 A CN 200710006850A CN 101239898 A CN101239898 A CN 101239898A
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Abstract
The invention provides a method for preparing pure terephthalic acid with purity above 99.98%, which uses a one-section high-efficiency dehydration rotary pressure filter, the filter is composed of four functional regions: hydraulic pressure filtering, first steam drying, second steam drying and feeding. Serum containing 25-43% PTA by weight is pumped into the rotary pressure filter under 3.5-5.5 Kg/cm2 (the surface pressure), and then filtered when passing through the first functional region, pure terephthalic acid crystals and the filtrate are seperated to form a filter cake with water content less than 43% by weight, the filter cake enters into the first stream drying region, the pressure is controlled in 4.0-4.5 Kg/cm2 (the surface pressure), most of filtrate in the filter cake is removed. Then the filter cake passes through the second stream drying region, the water content is reduced under 8% by weight, thereby obtaining pure terephthalic acid products with the purity of 99.98%. The invention has flexible operation, stable running, high yield. The filter device has advantages of low rotate speed, low investment and operation cost, effectively electric power saving and expense maintaining, etc.
Description
Affiliated technical field
The present invention relates to a kind of method that from aqueous slurry, reclaims pure terephthalic acid (PTA).
Background technology
The solid-liquid separation of purification section adopts pressure type whizzer and rotation vacuum filter more in traditional pure terephthalic acid (PTA) (abbreviating PTA as) manufacturing processed, promptly first section is adopted the pressure type whizzer, the slurry that the 5th crystallizer is come out carries out solid-liquid separation, rate of cake moisture content after the separation is between 10～15 weight %, at 2.5～4.0Kg/cm
2(gauge pressure) pulls an oar with the water that is heated to 138～151 ℃ in 138～151 ℃ the repulper again, to reach the impurity dissolved dilution and to avoid sepn process to produce the effect that crystal is separated out.Deliver to second section gerotor type whizzer or rotation vacuum filter then, the filter cake after the separation is delivered to the drying machine drying, reaches PTA product more than 99.98% to obtain preparation purity.
But because the pressure type whizzer adopts high speed rotating to make solid-liquid separation, to the equipment requirements height, so the equipment cost height, needing often to stop maintenance, and exist the separate unit treatment capacity little, energy consumption is big, shortcomings such as spare unit costliness.The pressure drop that the rotation vacuum filter produces when then existing owing to filtration, thus product crystallization blocking problem on filter cloth caused, the normal operation that influence is produced.
Chinese invention patent specification sheets CN 1035815C discloses number of patent application and has been: 92103686.8, and a kind of technical scheme of " being used to reclaim improving one's methods of pure terephthalic acid (PTA) " by name.It proposes, exceed that system pressure accounts under .034atm or the higher pressure and about 100 ℃ to about 205 ℃ temperature range, filter a kind of aqueous slurry that contains the pure terephthalic acid (PTA) of paratolunitrile solution, prepare a kind of filter cake of pure terephthalic acid (PTA) with this.Under exceeding a kind of pressure gradient of system pressure and about 100 ℃ to about 205 ℃ temperature range water from filter cake, displace the paratolunitrile solution that is retained in the pure terephthalic acid (PTA) filter cake.Employing release system pressure is to lower pressure and follow the method that makes temperature reduce to lesser temps that the moisture content that is retained in the filter cake is carried out pressure flash distillation processing.Make thus contain 200ppm or still less the pure terephthalic acid (PTA) crystalline product of paratolunitrile can under atmospheric pressure carry out drying.Because this technical scheme, be after the first step pressure filtration on the equipment of a continuous operation obtains the filter cake of pure terephthalic acid (PTA), to under pressurized conditions, wash this filter cake with water, water displaces the paratolunitrile solution that wherein keeps, remove the moisture content of this filter cake again with blowing inert gas, last decrease temperature and pressure utilizes flash distillation to remove remaining moisture content in this filter cake; Problem is that the key that improves pure terephthalic acid (PTA) crystalline product purity in this technical scheme is to increase the amount that water is used in the pressurized conditions underlying instead, and being divided into five cells, the equipment of continuous operation in this technical scheme, particularly rotary pressure filter inside carries out five kinds of different operations---the formation of filtration/filter cake, displacement washing, filtration cakes torrefaction, draw off filter cake, rinsing filter cloth.Preparing that purity reaches more than 99.98% is 150ppm or still less to the pure terephthalic acid (PTA) crystalline product of toluene dioctyl phthalate, will increase the pressurized conditions underlying and use the amount of water instead, and the minimizing of the content of the increasing amount of displacement water and water-soluble impurity is the relation of a pair of non-linear growth, this just means will strengthen the displacement washing district significantly on equipment, to have the production paratolunitrile now increases significantly in the displacement washing district of the pure terephthalic acid (PTA) equipment of 200ppm, and reduce the pressure filtration district, promptly reduce the output of equipment significantly; For keeping output to increase the dimensions of equipment, promptly increase equipment drops into.Another problem is that this technical scheme is to be divided into five zones to carry out five kinds of different operations realization solid-liquid separation and purifications on the equipment of a continuous operation, the through performance of structure more complicated and equipment filter cloth in service progressively descends, and operating parameters is difficult for changing in five zones, corresponding setting range is little, in case the through performance parameter overshoot scope of equipment operation filter cloth, quality product is difficult for guaranteeing.These washing water are as wastewater treatment simultaneously, and it is unacceptable that the quantity increase then has the occasion of strict demand at some to wastewater treatment.
Summary of the invention
The present invention aims to provide a kind of can the filtration and secondary pressure process obtains the filter cake of pure terephthalic acid (PTA), the device structure that uses is simple, big and the equipment operating parameter wide ranges of output, the preparation purity of being convenient to adjust reaches the method for the pure terephthalic acid (PTA) more than 99.98%.
The objective of the invention is to realize by following scheme: the method that preparation purity reaches the pure terephthalic acid (PTA) more than 99.98% comprises:
A. the aqueous slurry that contains terephthalic acid crystals is delivered in the hydraulic filtering district of high-effect dehydration rotary pressure filter and is formed filter cake, and wherein the temperature and pressure of filter cloth both sides, hydraulic filtering district maintains aqueous slurry and filtrate and all do not reach and be hypersaturated state so that the temperature and pressure that crystallization is separated out; The filter cake that filter to form rotates into next district, and promptly first section steam drying district is dry by the low-pressure steam extruding, and wherein the temperature and pressure of filter cloth both sides, first section steam drying district maintains filter cake and filtrate and all do not reach and be hypersaturated state so that the temperature and pressure that crystallization is separated out; Filter cake through first section steam drying district rotates into the i.e. second section air pressure drying zone in next district.
B. in second section air pressure drying zone, push drying by rare gas element; Rotating into next district through second section air pressure exsiccant filter cake is discharging area, the rate of cake moisture content that enters discharging area is controlled in the 8 weight %, through blowback air filter cake is blown into the blanking conduit, the filter cake blanking enters the feed auger device of rotary steam drying machine, after heating, remove residue moisture content, obtain purity and reach high purity terephthalic acid's product more than 99.98%.The embodiment of recommending is: described aqueous slurry terephthalic acid crystals content is 25～45 weight %, and the saturation pressure of this slurry is 2.0～6.0Kg/cm
2(gauge pressure), temperature of saturation is at 133～164.4 ℃; This aqueous slurry is sent into the hydraulic filtering district of high-effect rotary pressure filter through pressurization, rests on filter cake wet in this filter filter pocket after filtering and enters the pressure of filtrate of filtrate collection system and saturation pressure and the temperature of saturation that temperature all is not less than described slurry; Be collected in filter cake wet in this filter pocket through the hydraulic filtering district and rotate into first section steam drying district immediately, in first section steam drying district, use the liquid in the low-pressure steam removal filter cake, the steam condensate that contains filtrate enters knockout drum, obtain after the filtration moisture percentage at 12 weight % with interior filter cake, the filter cake in first section steam drying district and enter the pressure of low-pressure steam of filtrate of knockout drum and saturation pressure and the temperature of saturation that temperature all is not less than described slurry; Filter cake through first section steam drying district rotates into second section air pressure drying zone, and the pressure that uses rare gas element is at 1.0～6.0Kg/cm
2(gauge pressure), after two sections rare gas elementes were handled, filter cake entered discharging area and uses rare gas element to blow off or use scraper to scrape, and makes filter cake fall into the feed auger device of rotary steam drying machine through corresponding blanking conduit.
Preferred embodiment is: described aqueous slurry terephthalic acid crystals content is 35～45 weight %, and the saturation pressure of this slurry is 4Kg/cm
2(gauge pressure), temperature of saturation is at 151 ℃; Pressure is at 4.0～6.0Kg/cm in the hydraulic filtering district of high-effect rotary pressure filter
2(gauge pressure), the pressure drop of this filtrating area are 1Kg/cm
2(gauge pressure), the pressure of first section steam drying district low-pressure steam is 4.0～5.0Kg/cm
2(gauge pressure) and the pressure drop of filtration is about 1.0Kg/cm
2(gauge pressure); The pressure of second section air pressure drying zone rare gas element is at 1.0～4.0Kg/cm
2(gauge pressure).The recovered steam that described low-pressure steam can come automatic oxidation reaction to produce, or the high pressure steam decompression forms; Dried tail gas or nitrogen that described rare gas element can come automatic oxidation reaction to produce through being heated to 90 ℃～100 ℃, divide two sections extruding to remove filter cake institute water content.This carries the steam of aqueous vapor and rare gas element secretly respectively behind knockout drum, and condensation water drains into mother liquor tank, and saturated rare gas element discharges atmosphere through washing tower washing back.The present invention prepares the method that purity reaches the pure terephthalic acid (PTA) more than 99.98%, adopt one section to filter two sections exsiccant rotary pressure filters, this high-effect dewatering filter is divided into four functional zone again: hydraulic filtering district, first section steam drying district, second section air pressure drying zone and discharging area.This high-effect dewatering filter adopts pressure filtration, is controlled at all the time to be unlikely to the crystalline temperature and pressure on the filter cloth; Form moisture percentage 15 weight % with interior filter cake, dry via steam and two sections of rare gas elementes towards drying up, form moisture percentage 8 weight % and carry out the subsequent drying processing with interior filter cake.Make the aqueous slurry that contains terephthalic acid crystals when reaching the solid-liquid separation purpose, also effectively removed the impurity that is dissolved in the water.Impurity p-methylbenzoic acid in the product can be controlled in the 150ppm reliably, has improved the purity of product.Even operating parameter change in filtering, residual impurity increases, and guarantees that product is qualified after can regulating the parameter of second section rare gas element drying.Therefore turndown ratio is big, stable, the output height.Because this filter plant adopts the slow speed of revolution, than the high rotating speed centrifugation of known technology, not only cost of investment is low, and running cost is low, has saved electric power and pure water equal energy source, and the separate unit treatment capacity is big, the operational reliability height.Simultaneously because of in filtration procedure with steam extruding removal filtrate and be dissolved in impurity in the filtrate, further remove filtrate and be dissolved in impurity in the filtrate through the extruding of second section gas is dry again, reach highly purified purpose, relatively correlation technique after filtrating area forms filter cake immediately with the impure aqueous solution in the clear water displacement filter cake, remove moisture content with gas extruding filter cake then, last expansion drying becomes the mode of product, and device structure is simple.In theory, correlation technique uses continuous substitution method and the present invention earlier with most of liquid removal, and then adopts the QT Quality Target that reaches expection with filtrate in steam and the rare gas element two-stage drying method removal filter cake and impurity.The present invention has obviously saved water resources, has alleviated the load of wastewater treatment, has the tangible value of environmental protection.
Description of drawings
Fig. 1 is that the present invention prepares the schematic flow sheet that purity reaches the method for the pure terephthalic acid (PTA) more than 99.98%.
Fig. 2 is that the present invention prepares the Production Flow Chart synoptic diagram of an embodiment that purity reaches the method for the pure terephthalic acid (PTA) more than 99.98%.
Embodiment
The present invention prepares the method that purity reaches the pure terephthalic acid (PTA) more than 99.98%, and the rotary pressure filter is divided four functional zone---hydraulic filtering district, first section steam drying district, second section air pressure drying zone and discharging area.By strengthening hydraulic filtering district and air pressure drying zone increasing the filtration treatment ability, and set up filter cloth at discharging area and clean facility, effectively improve the filter treatment capacity to prolong the filter feed time.Adopt two sections dry rotary pressure filters to contain terephthalic acid (PTA) crystalline aqueous slurry solid-liquid separation, remove the most of impurity that is dissolved in the water simultaneously, to satisfy the requirement of the refining section of PTA solid-liquid separation.
The flow process of method of the present invention sees also Fig. 1.Contain that terephthalic acid crystals content is 25～45 weight % in the aqueous slurry 101 of terephthalic acid crystals, its saturation pressure is 2.0～6.0Kg/cm
2(gauge pressure), temperature of saturation is at 133 ℃～164.4 ℃.This aqueous slurry 101 is sent into the hydraulic filtering district of rotary pressure filter through pressurization, form wet filter cake after filtration in the hydraulic filtering district, wherein the temperature and pressure of filter cloth both sides, hydraulic filtering district maintains aqueous slurry 101 and filtrate 102 and does not all reach and be hypersaturated state so that the temperature and pressure that crystallization is separated out; Filter the wet filter cake that forms and rotate into i.e. first section steam drying district, next district, push drying by low-pressure steam 103, remove the liquid in the filter cake, wherein the temperature and pressure of filter cloth both sides, first section steam drying district maintains filter cake and filtrate 105 (claiming first section baric area filtrate again) and does not all reach and be hypersaturated state so that the temperature and pressure that crystallization is separated out.Obtain after the filtration moisture percentage at 15 weight % with interior filter cake, in 12 weight %, rotate into the i.e. second section air pressure drying zone in next district through the rate of cake moisture content in first section steam drying district, carry out press filtration by rare gas element 104; And discharge filtrate 108 (claiming second section baric area filtrate again).Rare gas element 104 pressure of second section air pressure drying zone are at 1.0～6.0Kg/cm
2(gauge pressure).Rotating into next district through the filter cake of the second air pressure drying zone is discharging area, the rate of cake moisture content that enters discharging area is controlled in the 8 weight %, use rare gas element 111 filter cake that blows off at discharging area, make filter cake fall into the rotary steam drying machine and after heating, remove residue moisture content, obtain purity and reach high purity terephthalic acid's product more than 99.98%.
The present invention prepares the Production Flow Chart of a specific embodiment that purity reaches the method for the pure terephthalic acid (PTA) more than 99.98%, sees also Fig. 2.Be mixed with solid impurity 4-carboxyl phenylformic acid in the crude terephthalic acid crystal (CTA) by the oxidation preparation, its content is about 2500～3000ppm, in purification section process hollander tub water dissolution, by being pumped into well heater and hydrogenation reactor hydrogenation reaction, these 4-carboxyl phenylformic acid have 99% to be reduced to water-soluble p-methylbenzoic acid (Para-Toluic Acid), make terephthalic acid crystals content be increased to about 40 weight % through four sections or the five sections crystallizations of reducing pressure again, obtain containing terephthalic acid (PTA) crystalline aqueous slurry 101.More than be known technology, needn't go through.Method of the present invention lays particular emphasis on from contain terephthalic acid (PTA) crystalline aqueous slurry 101 and realizes solid-liquid separation, remove the most of impurity p-methylbenzoic acid that is dissolved in the water simultaneously, to satisfy the requirement that the refining section preparation of PTA purity reaches the pure terephthalic acid (PTA) more than 99.98%.
Contain that the PTA crystalline content is about 25～45 weight % in the PTA crystalline aqueous slurry 101,151 ℃ of temperature, the concentration of major impurity p-methylbenzoic acid (Para-Toluic Acid) is 1100～1500ppm, the saturation pressure of this slurry 101 is 4.0Kg/cm
2(gauge pressure), temperature of saturation are 151 ℃.This aqueous slurry 101 is pressurized to 5.0～6.0Kg/cm through pump
2The pressure of (gauge pressure) is delivered in the hydraulic filtering district of high-effect dewatering filter, rests on after filtering to produce wet filter cake in the filter pocket of filtrating area, and filtrate 102 is drawn out to the mother liquor tank of filtrate collection system, does recycling.The pressure drop in this hydraulic filtering district is 1.0Kg/cm
2(gauge pressure), filter cake and filter after enter the pressure of filtrate 102 of filtrate collection system and the saturation pressure 4.0Kg/cm that temperature all is not more than described slurry 101
2151 ℃ of (gauge pressure) and temperature of saturation have been avoided in filtration procedure being created in owing to supersaturation appears in pressure drop that crystallization causes the filter cloth blocking problem on the filter cloth.About 75% moisture content can be removed by this hydraulic filtering district.Filter cake after the filtration can rotate into i.e. first section steam drying district, next district with filter pocket, pushes drying with low-pressure steam 103, removes the liquid in the filter cake.The steam and the phlegma thereof that contain filtrate 105 are drawn out to first section knockout drum, do corresponding Separation and Recovery and handle.Isolated gas 106 is discharged into vent scrubber, discharges atmosphere after carrying powder secretly with removal, and liquid 107 is delivered to the mother liquor tank of filtrate collection system, does recycling.The pressure of first section steam drying district low pressure steam 103 is 4.0～5.0Kg/cm
2(gauge pressure), temperature are 140-150 ℃, and the pressure drop of filtration is about 1.0Kg/cm
2(gauge pressure), the filter cake in first section steam drying district and enter the pressure of the steam that contains filtrate 105 of first knockout drum and temperature all greater than the saturation pressure 4.0Kg/cm of described slurry 101
2151 ℃ of (gauge pressure) and temperature of saturation have reached equally and have avoided making the filter cloth blocking problem owing to the supersaturation crystallization occurring.About 30% filtrate can be removed by this first section steam drying district, filter and after first section drying, obtain moisture percentage at 12 weight % with interior filter cake, removed the overwhelming majority and be dissolved in impurity p-methylbenzoic acids in the slurry 101.The content of p-methylbenzoic acid can be controlled in 160～180ppm in the filter cake.Filter cake through this first section steam drying district will rotate into the i.e. second section air pressure drying zone in next district with filter pocket, push drying by 104 pairs of filter cakes of rare gas element.The pressure of rare gas element 104 is operable in 1.0～4.0Kg/cm equally
2(gauge pressure), temperature are 90 ℃～120 ℃, and second section air pressure drying zone can be removed in the filter cake about 60% moisture content, and rate of cake moisture content is controlled in the 8 weight %, and then the content of impurity p-methylbenzoic acid is easy to be controlled in the 150ppm in the filter cake.The rare gas element that contains filtrate 108 that produces in second section air pressure drying zone is drawn out to second section knockout drum, does corresponding gas-liquid separation recycling.Second section isolated gas 109 of knockout drum discharging atmosphere after the vent scrubber washing.The pressure of rare gas element 104 is operable in 1.0～4.0Kg/cm equally
2(gauge pressure).In discharging area,, make it drop the blanking conduit, and introduce pure water 100 spray Cleaning for High Capacity filter clothes through being heated to 90 ℃ with the dried filter cake in the rare gas element 111 blowback filters.Backwater after the cleaning can be reclaimed use.
The situation of another group of concrete controlled variable correspondence in the present embodiment Production Flow Chart: contain that PTA content is about 33.4～37.1 weight % in the PTA crystalline aqueous slurry 101,133 ℃ of temperature, the concentration of p-methylbenzoic acid is 1100～1230ppm, and the saturation pressure of this slurry 101 is 2.0Kg/m
2(gauge pressure), temperature of saturation are 133 ℃.This aqueous slurry 101 is pressed in about 3.0～4.0Kg/cm through adding
2Deliver under the pressure of (gauge pressure) in the hydraulic filtering district of high-effect dewatering filter, rest on after filtering and produce wet filter cake in this filter filter pocket, filtrate 102 is drawn out to the filtrate collection system and does recycling.The pressure drop in this hydraulic filtering district is about 0.8Kg/cm
2(gauge pressure), filter cake and filter after enter the pressure of filtrate 102 of filtrate collection system and temperature all greater than the saturation pressure 2.0Kg/cm of described slurry 101
2133 ℃ of (gauge pressure) and temperature of saturation have been avoided causing the filter cloth blocking problem owing to pressure drop produces supersaturation crystallization on filter cloth in filtration procedure.Filter cake after the filtration rotates into first section steam drying district with filter pocket, with pressure 3.0～4.0Kg/cm
2(gauge pressure), temperature are that 140 ℃ low-pressure steam 103 is pushed drying, remove the filtrate in the filter cake, and the rare gas element that contains filtrate 105 is drawn does corresponding gas-liquid separation recycling.The pressure drop of this first section steam drying district filtration is about 1.0Kg/cm
2(gauge pressure), the pressure of the filter cake in first section steam drying district and the temperature of filtrate 105 and low-pressure steam are all greater than the saturation pressure 2.0Kg/cm of described slurry 101
2133 ℃ of (gauge pressure) and temperature of saturation have been avoided equally owing to crystallization makes the filter cloth blocking problem.Obtain after filter in this first section steam drying district moisture percentage at 12 weight % with interior filter cake, the content of p-methylbenzoic acid is at 155～185ppm in the filter cake of this moment.Rotate into second section air pressure drying zone through the filter cake in this first section steam drying district with filter pocket, by pressure at 1.0～4.0Kg/cm
2(gauge pressure), temperature are that 104 pairs of filter cakes of rare gas element of 90 ℃～120 ℃ carry out extruding second time drying, and rate of cake moisture content is controlled in the 8 weight %, and then the content of impurity p-methylbenzoic acid is controlled in the 150ppm in the filter cake.The filtrate 108 that produces in second section air pressure drying zone is drawn out to knockout drum and does corresponding gas-liquid separation recycling.Filter cake through this district rotates into discharging area with filter pocket, by pressure 0.5Kg/cm
2(gauge pressure), temperature are that the filter cake in 111 pairs of filter pockets of rare gas element of 90 ℃～100 ℃ is oppositely jetted and made its blanking, and fall into the feed auger device 201 that enters the rotary steam drying machine through corresponding blanking conduit, residue moisture content is removed in drying machine 202 heating backs, obtains the PTA product 203 of high purity.And with pure water 100 its filter cloth is cleaned up behind the filter cake blanking of discharging area, rotate into next filtration drying circulation again.
The situation of the 3rd group of concrete controlled variable correspondence in the present embodiment Production Flow Chart: contain that PTA content is 31.7～35.3 weight % in the PTA crystalline aqueous slurry 101,164.4 ℃ of temperature, the concentration of p-methylbenzoic acid is 1050～1170ppm, and the saturation pressure of this slurry 101 is 6.0Kg/cm
2(gauge pressure), temperature of saturation are 164.4 ℃.This aqueous slurry 001 is delivered under adding the pressure that is pressed in 7.0～8.0Kg/cm2 (gauge pressure) in the hydraulic filtering district of filter, filters to produce wet filter cake, and filtrate 102 is drawn out to the filtrate collection system, does recycling.The pressure drop in this hydraulic filtering district is about 1.0Kg/cm
2(gauge pressure).It is 5.0Kg/cm with pressure that filter cake after the filtration rotates into first section steam drying district with filter pocket
2(gauge pressure), temperature are that 151 ℃ low-pressure steam 103 is pushed drying, remove the liquid in the filter cake, and the pressure drop of filtration is about 1.0Kg/cm
2(gauge pressure), obtain after the filtration moisture percentage at 12 weight % with interior filter cake, the content of p-methylbenzoic acid is at 150～185ppm in the filter cake of this moment.。The rare gas element that contains filtrate 105 is drawn out to knockout drum, does corresponding gas-liquid separation recycling.Filter cake through first section steam drying district rotates into second section air pressure drying zone with filter pocket, by pressure at 1.0～6.0Kg/cm
2(gauge pressure), temperature are that 90 ℃～120 ℃ rare gas element pushes drying to filter cake, and rate of cake moisture content is controlled in the 8 weight %, and then the content of impurity p-methylbenzoic acid is controlled in the 150ppm in the filter cake.The filtrate 108 that produces in second section air pressure drying zone is drawn does corresponding gas-liquid separation recycling.Filter cake through this district rotates into discharging area with filter pocket, by pressure at 0.6Kg/cm
2Filter cake in 111 pairs of filter pockets of the rare gas element of (gauge pressure) is oppositely jetted and is made its blanking, and falls into the feed auger device 201 that enters rotary steam drying machine 202 through corresponding blanking conduit, removes residue moisture content after heating, and obtains the PTA product 203 of high purity.And with pure water 100 its filter cloth is cleaned behind the filter cake blanking of discharging area.
According to technical scheme of the present invention, only use a high-effect dehydration rotary pressure filter, can effectively separate PTA crystal and mother liquor in the PTA slurries, reach the function of removing impurity simultaneously.Not only exempt the filter cake process of pulp again, also the two-part filtering function is incorporated in the high-effect dewatering filter and reaches.In every case this allly utilizes technical scheme deutero-of the present invention that the rotary pressure filter is divided into four functional zone---hydraulic filtering district, first section steam drying district, second section air pressure drying zone and discharging area; adopt the high-effect dehydration rotary pressure of single seat filter to contain PTA crystalline aqueous slurry solid-liquid separation; make that impurity p-methylbenzoic acid content and the benzoic total content of 4-carboxyl all belong to protection scope of the present invention in the method and the application thereof of 200ppm with interior purification PTA in the product.
Claims (5)
1. one kind prepares the method that purity reaches the pure terephthalic acid (PTA) more than 99.98%: this method comprises:
The aqueous slurry that contains terephthalic acid crystals is delivered in the hydraulic filtering district of high-effect dehydration rotary pressure filter and is formed filter cake, and wherein the temperature and pressure of filter cloth both sides, hydraulic filtering district maintains aqueous slurry and filtrate and all do not reach and be hypersaturated state so that the temperature and pressure that crystallization is separated out; The filter cake that filter to form rotates into next district and promptly pushes drying by low-pressure steam in first section steam drying district, and wherein the temperature and pressure of filter cloth both sides maintains filter cake and filtrate and all do not reach and be hypersaturated state so that the temperature and pressure that crystallization is separated out; Filter cake through first section steam drying district rotates into the i.e. second section air pressure drying zone in next district, and filter cake is further dewatered enters discharging area to 8 weight %.The rate of cake moisture content that enters discharging area is controlled in the 8 weight %.
This water ratio with interior filter cake, enters the feed auger device of rotary steam drying machine through the blanking conduit at 8 weight %, removes through heating after and remains moisture content, obtains purity and reaches high purity terephthalic acid's product more than 99.98%.
2. a kind of method that purity reaches the pure terephthalic acid (PTA) more than 99.98% for preparing according to claim 1 is characterized in that: described aqueous slurry terephthalic acid crystals content is 25～45 weight %, and the saturation pressure of this slurry is 2.6～6.0Kg/cm
2(gauge pressure), temperature of saturation is at 133～164.4 ℃; This aqueous slurry is sent into the hydraulic filtering district of high-effect dehydration rotary pressure filter through pressurization, rests on filter cake wet in this filter filter pocket after filtering and enters the pressure of filtrate of filtrate collection system and saturation pressure and the temperature of saturation that temperature all is not less than described slurry; Be collected in filter cake wet in this filter pocket through the hydraulic filtering district and rotate into first section steam drying district immediately, in first section steam drying district, use the liquid in the low-pressure steam removal filter cake, the steam condensate that contains filtrate enters gas-liquid separator, obtain after the filtration moisture percentage at 8～12 weight % with interior filter cake, the filter cake in the steam drying district and enter gas-liquid separator and contain the pressure of steam condensate of filtrate and saturation pressure and the temperature of saturation that temperature all is not less than described slurry; Filter cake through first section steam drying district rotates into second section air pressure drying zone, uses rare gas element that moisture content that filter cake is carried secretly further is removed to below the 8 weight %; Dewatered cake rotates into discharging area, uses rare gas element to blow off or uses scraper to scrape filter cake at discharging area, makes filter cake fall into rotary steam drying machine drying through the blanking conduit, obtains purity and reaches pure terephthalic acid (PTA) more than 99.98%.
3. a kind of method that purity reaches the pure terephthalic acid (PTA) more than 99.98% for preparing according to claim 1 and 2 is characterized in that: described aqueous slurry terephthalic acid crystals content is 25～45 weight %, and the saturation pressure of this slurry is 4.0Kg/cm
2(gauge pressure), temperature of saturation is at 151 ℃; High-effect dehydration rotary pressure filter to the hydraulic filtering pressure at 4.5～6.0Kg/cm
2(gauge pressure), the pressure drop of this filtrating area are 1Kg/cm
2(gauge pressure), first section steam drying district inert gas pressure is 4.0～5.0Kg/cm
2(gauge pressure) and the pressure drop of filtration is 1.0Kg/cm
2(gauge pressure); The pressure of second section air pressure drying zone rare gas element is at 3.0～5.0Kg/cm
2(gauge pressure).
4. a kind of method that purity reaches the pure terephthalic acid (PTA) more than 99.98% for preparing according to claim 1 and 2, it is characterized in that: only use a high-performance dewatering filter, the two-section type of utilization low-pressure steam and rare gas element dehydrates method and removes the filtrate that contains high impurity in the pure terephthalic acid (PTA), thereby obtain high purity product, omit pulp process again, save a large amount of waters.
5. a kind of method that purity reaches the pure terephthalic acid (PTA) more than 99.98% for preparing according to claim 1 and 2, it is characterized in that: use the byproduct-low-pressure steam of pure terephthalic acid (PTA) factory and the dried tail gas or the nitrogen of oxidizing reaction, remove the filtrate that contains high impurity in the filter cake, not only reach the purpose of purifying, and can fully reclaim the utilization energy, reach the target of recycling economy and environmental protection.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNA2007100068502A CN101239898A (en) | 2007-05-23 | 2007-05-23 | Method for preparing pure terephthalic acid with purity more than 99.98wt% by using high efficiency dehydration filtering machine |
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| CNA2007100068502A CN101239898A (en) | 2007-05-23 | 2007-05-23 | Method for preparing pure terephthalic acid with purity more than 99.98wt% by using high efficiency dehydration filtering machine |
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| CNA2007100068502A Pending CN101239898A (en) | 2007-05-23 | 2007-05-23 | Method for preparing pure terephthalic acid with purity more than 99.98wt% by using high efficiency dehydration filtering machine |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111386281A (en) * | 2017-09-26 | 2020-07-07 | 拜康生物制品印度有限公司 | Integrated automated filtration for separation, washing and drying of peptide crystals |
| CN115445290A (en) * | 2022-09-13 | 2022-12-09 | 天华化工机械及自动化研究设计院有限公司 | Method for reducing moisture content of filter cake of pressure filter |
-
2007
- 2007-05-23 CN CNA2007100068502A patent/CN101239898A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111386281A (en) * | 2017-09-26 | 2020-07-07 | 拜康生物制品印度有限公司 | Integrated automated filtration for separation, washing and drying of peptide crystals |
| CN111386281B (en) * | 2017-09-26 | 2024-03-19 | 拜康生物制品印度有限公司 | Integrated automated filtration for separation, washing and drying of peptide crystals |
| CN115445290A (en) * | 2022-09-13 | 2022-12-09 | 天华化工机械及自动化研究设计院有限公司 | Method for reducing moisture content of filter cake of pressure filter |
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