KR910003973B1 - Recovery of benzoic acid from sludge of tere phthalic acid product process - Google Patents

Abstract

A method for the recovery of benzoic acid from a waste in the mfr. of terephtalic acid comprises (a) pressurizing the waste at 4-6 atms. and heating it in the preheater at 140-200 deg.C, (b) removing water and small amt. of acetic acid in the dewatering tower, (c) recycling the fixed amt. of a crude benzoic acid in the storage tank to improve a fluidity of the dehydrated waste, (d) heating it in the preheater, (e) removing the crude benzoic acid in the top of the tower, and (f) separating high b.p. component and solid material in the bottom of the tower.

Description

Recovery of Benzoic Acid from Wastes in Terephthalic Acid Manufacturing Process

Recovery process diagram of benzoic acid according to the present invention of the accompanying drawings

* Explanation of symbols for main parts of the drawings

BD-608: Waste Slurry Drum G-1 ... G-5: Transfer Pump

E-1 ... E-5: 1st ... 5th preheater T-1: Dehydration tower

E-11,12: cooler V-1: dehydration reservoir

D-1: waste storage tank T-2,3: primary and secondary distillation column

V-2: Joan style Hyangsan reservoir D-2: Joan style Hyangsan reservoir

E-13: Reflux Cooler V-3: Refining Angighyang Storage Tank

E-6: Planter M-1: Crystallization Device

H-2: Waste Purifier F-1: Storage Tank

The present invention relates to a method for recovering benzoic acid from the by-product waste produced in the terephthalic acid manufacturing process, and more particularly to a method for separating and recovering the industrial level of benzoic acid by distillation from waste produced by the terephthalic acid manufacturing process.

P-Xylene contains impurities such as ethylbenzene and toluene, which are used as main raw materials in the production of terephthalic acid. They are oxidized to benzoic acid, and some of the xylenes are directly converted to benzoic acid by side reactions.

Most of the benzoic acid produced in this way is contained in wastes and incinerated in incinerators or sent to wastewater treatment plants for treatment by activated sludge process, and some of them are contained in the discharge gas of terephthalic acid storage tanks and crude terephthalic acid which is introduced into refining processes.

In general, the waste produced in the terephthalic acid manufacturing process contains a variety of by-products as shown in Table 1 in addition to the above materials, there is a difficulty in installing a prevention equipment to prevent the emission of pollutants during incineration.

TABLE 1

Representative Components of Process Waste

Therefore, the main object of the present invention is to separate and recover useful materials from industrial wastes that are being treated by incineration and decomposition, which is useful for industrial use, that is, recycling resources. Another object of the present invention is to solve the pollution problem in advance by recycling the wastes by-products produced during the production of terephthalic acid is incinerated to cause air pollution.

Benzoic acid recovery process of the present invention for achieving the above object is largely divided into a dehydration process and a distillation process described in detail by the accompanying drawings as follows.

end. Dehydration Process

The wastes produced in the terephthalic acid manufacturing process have melting points and boiling points as shown in Table 2, and these wastes are discharged from the waste slurry drum (BD-608) by the transfer pump (G-1). , 2) and heated to 140-220 ° C and then supplied to the dehydration tower (T-1) to dehydrate the water and a small amount of crude acid. The dehydrated waste is circulated in a Joan Hyangsan Reservoir (V-2) to prevent clogging by improving molten state or fluidity. The inside of the dehydration tower (T-1) is maintained at 140-220 ° C. Traces of water contained in the waste can be removed while staying in the buffer tank, and the removed water (vapor) is cooled by water at 50-60 ° C. in the cooler (E-11).

TABLE 2

Melting point and boiling point of each component in waste

B. Distillation process

The dehydrated waste from the dehydration process is 240-250 ° C in the preheater (E-3) of the two preheaters (E-3,4) installed in the primary distillation column (T-2). It is heated to ℃ and transferred to the fourth preheater (E-4), and heated to 280 ° -300 ℃ in the fourth preheater (E-4) is supplied to the feed stage of the primary distillation column (T-2).

Benzoic acid, which is a low boiling point component, is separated into Joan benzoic acid, which is a top tablet product, passing through the packed column, and high boiling point components and other solid substances become tower bottoms to separate benzoic acid. At this time, the temperature of the tower top is maintained at 210 ° -250 ℃ and the bottom temperature of the tower is maintained at 260 °-300 ℃.

The crude product, benzoic acid, was liquefied and cooled in a reflux condenser (E-13) at about 180 ° -200 ° C. and stored in the crude benzoic acid storage tank (V-2), which was partially dewatered to improve the fluidity of the dehydrated waste. It is supplied to the bottom of the tower (T-1), part is refluxed to the tower and part is supplied to the tank for supplying the secondary distillation column (T-3). At this time, the reflux solution returned to the tower is supplied to the fifth preheater (E-5) at the bottom of the packing and mixed with the dehydration waste solution.

The internal temperature of the secondary distillation column (T-3) supply tank is maintained at 180 ° -200 ° C, and the crude benzoic acid melt is supplied to the secondary distillation column (T-3) preheater (T-5) to provide 250 °- It is heated to about 290 ℃ and is supplied to the feed stage of the secondary distillation column (T-3). The heated crude benzoic acid solution is recovered in the tower column by the boiling point as in the first distillation column (T-2), and the benzoic acid is recovered to the tower, but the temperature of the tower is controlled in the range of 210 ° -260 ° C. The reflux ratio in the reflux cooler (E-13) is then adjusted to a range of 3-10 to determine the purity of the benzoic acid product. The purified benzoic acid solution is passed through a crystallization apparatus and becomes a final product.

On the other hand, the final residue after separation of the angular aromatic acid at the bottom of the first distillation column (T-2) is a mixture of high boiling point components and high temperature sublimable components that do not melt. Particular attention should be paid to blockages at. The operating temperature at the bottom of the column is maintained at 260 ° -300 ° C and the resulting residue is solidified as it passes through the residue cooler. At this time, the residue of the bottom of the second distillation column (T-3) is also treated with the primary.

Such benzoic acid recovered in accordance with the present invention has an industrial level of purity.

The embodiment of the present invention will be described in more detail as follows.

EXAMPLE

Test Factory Recovery Method

In order to prevent clogging in the process by putting wastes produced by terephthalic acid in the dehydration tank and improving fluidity, the industrial benzoic acid is added together, and the fruit feed valve is heated and maintained at 105 ° -120 ° C. Some residual moisture is removed by raising the temperature to 180 ° -200 ° C. While maintaining the melt at 180 ° -200 ° C, it is sent to the furnace using a pump and heated to 280 ° -300 ° C to be supplied to the distillation column. The distillation column is kept at atmospheric pressure and the filling is divided into two stages. The top of the tower maintains a temperature of 240 ° -250 ° C while the tower's gas passes through the cyclone to separate some entrained materials. The benzoic acid gas after the cyclone is transferred to the reservoir as a solution of about 180 ° C in a reflux condenser. Some of the solution in this reservoir is refluxed to the tower and some is returned to the product. At this time, the reflux ratio is maintained at 3.

In addition, the residue from which benzoic acid is separated from the distillation column is heated to 280 ° -300 ° C. in the cultivator in the tower and fed back to the distillation column, and the final residue is recovered in the bottom stream. The reboiler was used together with the heating material.

Purity of the product recovered through the test plant by the above method is shown in Table 3 and Table 4.

TABLE 3

Material balance and analysis table for recovery of crude benzoic acid in the test process

TABLE 4

Material Balance and Analysis Table for Recovery of Refined Benzoic Acid from Test Plant

Claims (4)

In the method of recovering benzoic acid from the waste of the terephthalic acid manufacturing process, the waste is pressurized to 4-6 atm and heated in a preheater to 140 °-200 ℃ and fed to the dehydration tower to remove water and a small amount of acetic acid, By circulating a certain amount of Joan Hyangsan in a storage tank to improve the fluidity of the dehydrated waste, such dehydrated waste is transferred to a preheater, heated and fed to the primary feed stage of the distillation column to separate Joan Hyangsan from the top of the tower, A method of recovering benzoic acid from waste in a terephthalic acid manufacturing process, characterized in that other high boiling point components and solids are separated into waste at the bottom. The method for recovering benzoic acid from waste in a terephthalic acid production process according to claim 1, wherein the temperature in the dehydration column is maintained at 140 ° -200 ° C. before dehydration is conducted to the distillation column. The method for recovering benzoic acid from waste in a terephthalic acid manufacturing process according to claim 1, wherein the temperature at the top of the tower is maintained at 210 ° -250 ° C and the temperature at the bottom of the tower is maintained at 260 ° -300 ° C. The method of claim 1, wherein the purity of the crude benzoic acid is 70-98% by the first distillation, the purity is 98% or more in the second distillation, and the trace metal content is removed. A method for recovering benzoic acid from wastes in a lephthalic acid manufacturing process.