Treatment process of bisphenol a wastewater acetone

Abstract

The application discloses a kind of bisphenol A wastewater in acetone processing technology, using single column continuous rectification process to treat acetone bisphenol A (BPA) wastewater, partial condensation is used in rectification tower top, and condensate phase is used as reflux.The gaseous mixture that is not condensed is continuously entered subsequent incineration device by pressurized operation, the process can reduce the methanol and acetone concentration in tower kettle wastewater to below 50ppm, compared with general rectification processing method, combined use single column continuous rectification and incineration process can effectively reduce energy consumption, and has good application and popularization value in BPA production industry.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of treatment process of acetone in bisphenol A wastewater. BACKGROUND

[0002] Bisphenol A (BPA), chemical name 2,2-bisphenol propane, is widely used in the production of polycarbonate, epoxy resin, polysulfone resin, polyphenyl ether resin, unsaturated polyester resin, etc. At present, the industrial production of BPA generally uses phenol and acetone as raw materials, uses sulfuric acid, hydrogen chloride or strong acid cation exchange resin as catalyst, and produces in stirred tank batch or continuous method. In addition to generating BPA, some isomers, trihydroxy or monohydroxy byproducts are also generated. When used to manufacture polycarbonate, through continuous rectification, hydrogen chloride, water (after condensation, as recycled hydrochloric acid, re-injected into the reactor), acetone are sequentially distilled out, and by removing impurities, the purity of BPA can be effectively improved. As can be seen from the above production process, a series of salt-containing wastewater such as acetone, methanol and phenol will inevitably be produced during the production of BPA. Among them, acetone is not only an important solvent but also an organic chemical raw material, and direct discharge will not only pollute the environment but also be detrimental to the later refining of BPA. Therefore, in order to avoid waste of acetone, reduce cost loss, improve the purity of BPA products and protect the environment, the recovery and treatment of acetone in salt-containing BPA wastewater is imminent.

[0003] At present, there are only a few reports on the purification and treatment process of acetone in BPA wastewater. Dong Xiaohong recovered and treated acetone waste liquid by double-tower rectification of fine acetone tower and crude acetone tower. The fine acetone tower used an independent vacuum system, and the gas condensate was sprayed back into the rectification tower by vacuum. The crude acetone tower used the original total vacuum system to spray steam condensate as process water, and the tail gas in the crude acetone tower was discharged into the fine acetone tower. The operating pressures of the two towers were reduced respectively, which improved the equipment processing capacity and the separation effect of acetone, effectively solved the problem of excessive acetone content in wastewater, and reduced the acetone content in the wastewater from the fine acetone tower to below 100 ppm. However, this method requires the use of double towers of crude acetone tower and fine acetone tower, which has high cost. It is urgent to establish a single-tower process for acetone purification, and the acetone content in the wastewater after purification needs to be further reduced. Liu Huabao et al. used a membrane bioreactor to treat phenol acetone and BPA device wastewater using the "air floatation-hydrolysis acidification-primary aerobic treatment-secondary MBR" process, which could meet the discharge standard. However, this method did not recover the acetone product, which indirectly increased the cost of raw materials for producing BPA. In summary, the current treatment of acetone in BPA wastewater still has problems such as low wastewater purification rate, high energy consumption and high cost. SUMMARY

[0004] To solve the above problems of the prior art, the present application provides a treatment process of acetone in bisphenol A wastewater, which adopts single-tower continuous rectification process to treat BPA wastewater containing acetone by comprehensively considering the treatment capacity and product separation requirements, uses partial condensation at the top of the rectification tower, takes the condensed liquid phase as reflux, pumps the tower kettle liquid into a feed heat exchange device through a tower kettle pump, exchanges heat with the wastewater to be separated, and then enters a wastewater outlet area, and the uncondensed gas phase mixture (acetone purity of more than 80%) enters a subsequent incineration device through pressurized operation.

[0005] A treatment process of acetone in bisphenol A wastewater, which comprises a feed heat exchange section, a tower top condensation section and a tower kettle reboiling section; the feed heat exchange section comprises BPA wastewater after heat exchange entering the rectification tower and tower kettle reflux liquid after heat exchange flowing into a wastewater outlet area; the tower top condensation section comprises tower top gas phase material after condensation partially refluxing into the rectification tower and uncondensed gas phase after pressurized operation being sent to an external incineration; and the tower kettle reboiling section comprises tower kettle waste liquid refluxing to the feed heat exchange section and steam entering the rectification tower.

[0006] The following will introduce the treatment process of acetone in BPA wastewater in detail. Firstly, the influence of theoretical plate number on the acetone content at the top and the kettle and the methanol content at the kettle is investigated. With the increase of the theoretical plate number, the acetone content at the top gradually increases, the acetone content at the kettle gradually decreases, and the methanol content at the kettle gradually increases. When the theoretical plate number increases to a certain value, the acetone content at the top reaches the highest and tends to be stable, the acetone content at the kettle reaches the lowest and tends to be stable, and the methanol content at the kettle also reaches the highest and tends to be stable.

[0007] Further, in the treatment process, the range of the theoretical plate number is preferably 25-35 blocks, and more preferably 25 blocks.

[0008] Secondly, the present application also investigates the influence of the feed position on the treatment process of BPA wastewater acetone. With the increase of the plate number of the feed position, the acetone content at the top presents a trend of first increasing and then decreasing, the acetone content at the kettle presents a trend of first decreasing and then increasing, and the methanol content at the kettle presents a decreasing trend, and then the methanol content at the kettle tends to be stable.

[0009] Further, in the treatment process, the feed position of the rectification tower is preferably the 3rd-10th block, and more preferably the 4th block.

[0010] Thirdly, the present application also investigates the influence of the reflux ratio on the treatment process of BPA wastewater acetone. With the increase of the reflux ratio, the acetone content at the top presents a gradually increasing trend, and the acetone content at the top increases little with the continuous increase of the reflux ratio. The acetone content at the kettle is basically unchanged within a certain reflux ratio, and the acetone content at the kettle presents a gradually decreasing trend with the continuous increase of the reflux ratio. The reflux ratio has basically no influence on the methanol content at the kettle.

[0011] Further, in the treatment process, the reflux ratio of the rectification tower is preferably 2-10, more preferably 4.

[0012] Further, in the treatment process, the condensation is a circulating water, wherein the circulating water temperature is 32℃ for the circulating feed water, 40℃ for the circulating return water, and the circulating water pressure is 0.4MPaG for the circulating feed water and 0.25MPaG for the circulating return water.

[0013] Finally, the present application also investigates the influence of the stripping steam input on the BPA wastewater acetone treatment process, the higher the stripping steam input, the higher the acetone concentration at the tower top, and the lower the acetone and methanol concentrations at the tower bottom.

[0014] Further, in the treatment process, the steam input is 650-850kg / hr, preferably 780 or 850kg / hr, more preferably 780kg / hr.

[0015] Further, in the treatment process, the steam pressure is 0.35MpaG, and the temperature is 139℃.

[0016] Further, in the treatment process, the pressure of the pressurized operation is 50kPa.

[0017] Compared with the prior art, the present application has the following beneficial effects:

[0018] (1) The bisphenol A wastewater treated by the present process can reach the discharge standard.

[0019] (2) By using the single-tower continuous rectification process, the uncondensed gas phase mixture at the tower top is sent to the outside for incineration, and the tower bottom liquid is returned to the feed heat exchange device for further heat exchange treatment, and compared with the general rectification process, the single-tower continuous rectification and incineration process can reduce the steam usage by 8.2%, so the process has good application and promotion value in the BPA production industry. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a treatment process diagram for acetone in bisphenol A wastewater of the present application;

[0021] 1 - feed pipe, 2 - feed heat exchanger, 3 - rectification tower, 4 - condenser, 5 - gas outlet pipe, 6 - liquid outlet pipe;

[0022] Figure 2 is the test result of the theoretical plate number on the acetone content at the tower top (2a), the acetone content at the tower bottom (2b), and the methanol content at the tower bottom (2c);

[0023] Figure 3 is the test result of the feed position on the acetone content at the tower top (3a), the acetone content at the tower bottom (3b), and the methanol content at the tower bottom (3c);

[0024] Figure 4 The test results of the top acetone content (4a), the acetone content in the column bottom (4b) and the methanol content in the column bottom (c) are compared. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0026] The BPA wastewater used in the present application is from a chemical plant in Cangzhou, and the detailed composition is shown in Table 1. The composition and properties of the BPA wastewater used in the test are shown in Table 1.

[0027] Table 1: Composition and properties of raw materials

[0028]

[0029]

[0030] The detection method of the organic matters such as methanol, acetone and phenol involved in the present application is gas chromatography. The gas chromatography is Shimadzu GC-2010pro, and the chromatographic column is FFAP. The chromatographic conditions are as follows: gasification chamber, detector 250 DEG C, initial temperature of chromatographic column 70 DEG C, maintaining for 4 minutes, temperature programming at 20 DEG C per minute, final temperature 220 DEG C, maintaining for 4 minutes.

[0031] The acetone, methanol and the like in the material are low-boiling-point substances, and the mixture material with the required acetone content can be obtained from the top of the simple distillation, so as to reduce the organic matter content in the salt-containing wastewater. Considering the treatment capacity and product separation requirements, the acetone treatment process in the bisphenol A wastewater described in the present application comprises a feed heat exchange section, a top condensation section and a column bottom reboiling section. The feed heat exchange section comprises that the bisphenol A wastewater is introduced into the distillation column after heat exchange, and the column bottom reflux liquid is flowed into the wastewater outlet area after heat exchange. The top condensation section comprises that the top gas-phase material is condensed and part of the reflux is introduced into the distillation column, and the uncondensed gas phase is sent to the outside for incineration after pressure operation. The column bottom reboiling section comprises that the waste liquid in the column bottom is refluxed to the feed heat exchange section, and the steam is introduced into the distillation column.

[0032] The reflux liquid flowing from the top continuously multi-stages countercurrently contacts with the ascending gas phase in the packing surface, so as to realize the separation of the low-boiling-point acetone and water. The column bottom liquid of the acetone distillation column is mainly water and Na2SO4, which is transported to the outside after heat exchange with the raw material. The setting of the column bottom liquid refluxing to the feed heat exchange section effectively reduces the steam consumption, and saves the operation cost of the whole system.

[0033] Example 1: The effect of theoretical plate number on the acetone treatment process of BPA wastewater

[0034] First, the effects of the theoretical number of trays on the acetone content at the top and bottom of the column, and the methanol content at the bottom, were investigated through simulation calculations. Figure 2 As can be seen from a, when the feed position is the 3rd tray, the reflux ratio is 3, and the stripping steam flow rate is 650 kg / hr, the acetone content at the top of the column gradually increases with the increase of the theoretical number of trays. When the theoretical number of trays is 25-35, the acetone content at the top of the column reaches 0.83 and tends to stabilize. Figure 2 As shown in b, with the increase of the theoretical plate number, the acetone content in the bottom of the column gradually decreases. When the theoretical plate number is 25-35, the acetone content in the bottom of the column reaches 0.00005 and tends to stabilize. Figure 2 As shown in section c, the methanol content in the reboiler gradually increases with the increase of the number of theoretical plates. The methanol content in the reboiler reaches its highest point when the number of theoretical plates is 25-35, and then tends to stabilize. Considering both increasing the acetone content at the top of the column and decreasing the acetone content and methanol content in the reboiler, a theoretical plate number of 25-35 is selected. Based on this theoretical plate number, a 9m ZFTK752Y packing is considered for use in the actual design.

[0035] Example 2: The Influence of Feed Location on the Acetone Treatment Process for BPA Wastewater

[0036] like Figure 3 As shown, the effects of feed location on the acetone content at the top and bottom of the column, and the methanol content at the bottom, were investigated. When the theoretical number of trays was 25, the reflux ratio was 3, and the stripping steam flow rate was 650 kg / hr, the results were as follows: Figure 3 As can be seen from a, with the increase of the number of trays at the feed location, the acetone content at the top of the column shows a trend of first increasing and then decreasing; when the feed location is the 3rd to 10th tray, the acetone content at the top of the column is relatively high. Figure 3 As shown in b, with the increase of the number of trays at the feed location, the acetone content in the reboiler shows a trend of first decreasing and then increasing; when the feed location is the 3rd to 10th tray, the acetone content in the reboiler is relatively low. Figure 3 As shown in section c, the methanol content in the reboiler decreases with increasing feed position and plateaus after the 5th plate. Considering both increasing the acetone content at the top and decreasing the acetone and methanol content at the bottom, plates 3-10 are selected as the feed plates. In the actual design, the feed position is considered to be the upper section of the distillation column.

[0037] Example 3: Effect of reflux ratio on acetone treatment process for BPA wastewater

[0038] like Figure 4The effect of reflux ratio on the content of acetone at the top of the column and the content of methanol at the column bottom was investigated. When the theoretical plate number was 25, the feeding position was the 4th plate, and the stripping steam input was 650 kg / hr, it was found from Figure 4 a that with the increase of the reflux ratio, the content of acetone at the top of the column gradually increased, and when the reflux ratio was 2-10, the content of acetone at the top of the column increased from 0.8262 to 0.8273, with a small increase range; from Figure 4 b it was found that when the reflux ratio was less than 20, the content of acetone at the column bottom was basically unchanged, and with the continuous increase of the reflux ratio, the content of acetone at the column bottom gradually decreased; from Figure 4 c it was found that the reflux ratio had basically no effect on the content of methanol at the column bottom. In summary, the reflux ratio had little effect on the content of acetone at the top of the column and the content of methanol at the column bottom. Considering that the wet packing needs a certain amount of reflux, the reflux ratio was designed to be 2-10.

[0039] Example 4: Effect of stripping steam input on the BPA wastewater acetone treatment process

[0040] The test results are shown in Table 4. From the perspective of reducing the concentration of methanol and acetone in the wastewater at the column bottom, three stripping steam input conditions were compared. The theoretical plate number was 25, the feeding position was the 4th plate, the reflux ratio was 4, and when the test stripping steam input was 600 kg / hr, the concentration of methanol and acetone in the wastewater at the column bottom was still higher than 50 ppm, so the stripping steam input of 600 kg / hr did not meet the requirements. When the stripping steam input was 780 kg / hr and 850 kg / hr, the concentration of methanol and acetone in the wastewater at the column bottom was lower than 50 ppm, which met the requirements. The distillation process designed in the present application can effectively remove light components such as methanol and acetone in the wastewater.

[0041] Compared with the general distillation treatment method by directly purifying acetone to more than 98%, the present study used a single-column continuous distillation and incineration process with a stripping steam input of 780 kg / hr, which can reduce the steam usage by 8.2%, indicating that the present process can effectively reduce energy consumption.

[0042] Table 5 Test results

[0043]

[0044] Compared with the double-column distillation method through the fine acetone column and the crude acetone column, the single-column distillation method in the present study has a lower concentration of methanol and acetone in the wastewater at the column bottom, a higher concentration of acetone at the top of the column, a higher recovery rate of acetone solvent, and a lower cost. This indicates that the acetone recovery process constructed in the present study can effectively solve the problems of low recovery rate of acetone, high energy consumption, and high equipment cost.

[0045] The above merely describes the preferred embodiments of the present application, and it should be pointed out that, for those skilled in the art, several improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be considered as falling within the protection scope of the present application.

Claims

1. A process for treating acetone in bisphenol A wastewater, characterized in that, The process includes a feed heat exchange section, a top condensation section, and a bottom reboiler section. The feed heat exchange section includes bisphenol A wastewater entering the distillation column after heat exchange and the reflux liquid from the column bottom flowing into the wastewater outlet area after heat exchange. The top condensation section includes the top gaseous material being condensed and partially returned to the distillation column, and the uncondensed gaseous material being pressurized and sent to the outside for incineration. The reboiler section of the column includes the reflux of waste liquid in the column bottom to the feed heat exchange section and the entry of steam into the distillation column; The distillation column has 25 theoretical trays, the feed position is the 4th tray, the reflux ratio is 4, and the steam flow rate is 650-850 kg / hr.

2. The processing technology according to claim 1, characterized in that, The steam pressure is 0.35 MPaG and the temperature is 139°C.

3. The processing technology according to claim 1, characterized in that, The condensation is achieved by circulating water, with the circulating water temperature being 32°C for the feed water and 40°C for the return water, and the circulating water pressure being 0.4 MPaG for the feed water and 0.25 MPaG for the return water.

4. The processing technology according to claim 1, characterized in that, The pressure for the pressurization operation is 50 kPa.

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