CS258194B1 - A method for removing organic matter from wastewater - Google Patents

Abstract

The solution relates to a method of removing organic substances from wastewater, in particular aromatic hydrocarbons from the water phase separated from the product formed during the dehydrogenation of ethylbenzene to styrene. Wastewater with an aromatic substance content of 5.10-2 to 5.10-1 g/1 is brought into contact with a layer of activated carbon after stripping with steam at a surface load of 1.6 to 300 m3/h of water per 1 m2 of the activated carbon layer. The volumetric load is 0.5 to 240 m3/h of water per 1 m3 of the activated carbon layer.

Description

BACKGROUND OF THE INVENTION The present invention relates to a process for the removal of organic matter from waste water, in particular flavorings from the aqueous phase separated from the product resulting from the dehydrogenation of ethylbenzene to styrene, to a purity allowing the use of this water, for example as a return condenser.

In the production of styrene by catalytic dehydrogenation of ethylbenzene, a product is formed which is a mixture of hydrocarbons and water. At rest, this product is separated into a hydrocarbon layer of hydrocarbon and a lower layer of the aqueous phase, which however contains traces of hydrocarbons. Outside this pollution, however, this water is at the level of steam condensate. Therefore, after removal of flavoring substances and possibly. other organic substances quite widely used.

It is known that these substances can be partially removed by distillation or aeration of the waste water.

The disadvantage of these processes, however, is that distillation must be carried out under vacuum, and that none of these processes allows organic matter, in particular hydrocarbons, to be removed economically to an acceptable low level and, in addition, has an adverse environmental impact associated with air leakage. .

In the first case, the trace content of aromatic substances A.10 ^-4 to 1. g0 ^-3 g / l will remain in the waste water and further reduction of their content can be done only with a disproportionate increase in costs.

In the second case, i.e. when cleaning the aeration remains water residual amount of aromatics 10.5 * ^ to 5.10 ^-3 g / 1st

In the book J. Dvořák Sewage Treatment of Oil-containing Wastes, SNTL 1982, page 172 states that the method of cleaning impurities by contact with activated carbon is also applicable to treatment of oil-containing waste water. However, no detailed information is given on the necessary parameters of conducting such a process. However, this process is expensive at higher organic concentrations.

These disadvantages of the prior art are overcome by a process for removing organic matter from waste water, in particular aromatic hydrocarbons, from the aqueous phase separated from the product resulting from the dehydrogenation of ethylbenzene to styrene by stripping and contact with activated carbon, according to the invention. With aromatic substances from 5.10

5.10 ^-1 g / l is first subjected to steam stripping at a temperature of 100 to 200 ° C and an absolute pressure of 0.5 to 1.0 MPa and the amount of stripping steam is 0.02 to 0.5 t / m ^{3 of} waste water, whereupon 3 is contacted with an activated carbon layer at a surface load of 1.6 to 300 m / h of water 3 3 3 per 1 m of activated carbon layer with a volumetric load of 0.5 to 240 m / h of water per 1 m of activated carbon layer.

The advantage of the method of removing organic substances from waste water according to the invention is that after passing the water through the purification column the organic contamination is eliminated absolutely, especially contamination by organic substances such as styrene, ethylbenzene, benzene, toluene and others.

After the first trace of organic substances, the cleaning capacity of activated carbon is renewable by some of the methods known for its regeneration, for example by steam blowing.

The effects and advantages of the wastewater treatment according to the invention are further illustrated in more detail and more specifically by the following examples.

Example 1

For comparison with the process of the invention, the waste water produced in the separation of the hydrocarbon and aqueous phases of the product of catalytic dehydrogenation of ethylbenzene to styrene with a total aromatic content of 1.5 x 10 ^-1 g / l was purified by steam stripping on a multistore column with Ra- 3 Schig rings. The steam was metered in an amount of 0.043 t / m at an absolute pressure of 0.65 MPa and a temperature of 185 ° C.

Despite a significant reduction in aromatics avoid their absolute removal and waste water continues to contain 1.10 ^-4 to l.io ³ g / 1 of organic substances.

Example 2

For comparison with the method of the invention, the waste water of Example 1 was also purified by air purge desorption. The air was dosed at 5,000 l / l of water.

Water pollution was reduced, but the water still contained 5.10 ^-4 to 5.10 g / l of aromatics. Further increases in the amount of air have failed to reduce the aroma content below the above-mentioned value.

Example 3

The waste water of Example 1 was purified by the method of the invention first by stripping according to Example 1 and then contacted with an activated carbon layer under surface loading

2 3

17.46 m water per hour per 1 m layer of activated carbon and a volume load of 14.95 m water per hour per 1 m layer of activated carbon.

Activated carbon was placed in a bed in a closed column. Activated carbon HS 4 Supersorbon according to CSN 668421 was used.

The resulting effluent did not contain analytically detectable amounts of aromatics or other organic matter and was of steam condensate quality.

Due to the accuracy of the analytical method used, the organic matter content had to be below 1.10 ^- ® g / l.

_2

The process according to the invention made it possible to purify 5,500 m of waste water per 1 kg of activated carbon in waste water containing 1.2.10 g / l of organic substances after stripping. It was then necessary to carry out the regeneration of activated carbon in a manner known per se.

Claims (1)

Process for the removal of organic matter from waste water, in particular aromatic hydrocarbons, from the aqueous phase separated from the product resulting from dehydrogenation of ethylbenzene to styrene by stripping and contact with activated carbon, characterized in that the waste water with aromatic content from 5.10 to 5.10 g / l is first subjected to steam stripping at a temperature of 100 to 100 ° C 200 ° C and an absolute pressure of 0.5 to 1.0 MPa and the amount of stripping steam is 0.02 to 0.05 t / m ^{3 of} wastewater, and then it is contacted with an activated carbon layer at a surface load of 3 2 3 1.6 to 300 m / h of water per m of activated carbon layer with a volumetric load of 0.5 to 240 m / h of water per m ³ of activated carbon layer.