RU2278148C1 - Method of purification of the industrial gas outbursts - Google Patents

Abstract

FIELD: petrochemical industry; methods of purification of industrial gases outbursts.

SUBSTANCE: the invention is pertaining to the field of petrochemical industry, in particular, to the method of, purification of the industrial gas outbursts formed in the reprocessing of alkylenes oxides. The industrial gas outbursts containing alkylenes oxides and carbonyl compounds are cooled, then they are subjected to absorption by the water solution of glycols containing 10-60 mass % of glycols and 0.1-5.0 mass % of alkali with the subsequent hydration of the alkylenes oxides and the recycling of the absorber into the phase of absorption. The gaseous outbursts before the phase of absorption are cooled up to the temperature of minus 5 - minus 40°C. The absorber after hydration of alkylenes oxides is subjected to reducing hydrogenation. The technical result of the invention is purification of the industrial gaseous outbursts from the alkylenes oxides and carbonyl compounds up to the ecologically safe concentrations.

EFFECT: the invention ensures purification of the industrial gaseous outbursts from alkylenes oxides and carbonyl compounds up to the ecologically safe concentrations.

3 cl, 3 tbl, 5 ex, 1 dwg

Description

The invention relates to the field of petrochemistry, specifically to the purification of industrial gas emissions resulting from the processing of alkylene oxides.

In various processes for the processing of alkylene oxides, in particular ethylene and propylene oxides, gaseous wastes are formed containing alkylene oxides and carbonyl compounds, for example, such as acetaldehyde and propionic aldehyde.

Known methods for cleaning industrial gas emissions from ethylene oxide by adsorption on activated carbon, limestone, silica gel, followed by regeneration of the adsorbent by washing with hot water (Application Germany No. 4405276, IPC C 07 C 31/20, publ. 24.08.95), water and water glycolic solutions of alkalis or acids (Wurster Bemd. - Effiziente Eliminirug von Ethylenoxid aus Ablluft. - Werstofe Fertig 2002, No. 2, p. 34-35).

There is also a method of cleaning gas emissions from aldehydes by adsorption using activated carbon as adsorbent (US Patent No. 39707711, IPC C 07 C 029/00, C 07 C 029/24, publ. 20.07.76).

The disadvantage of the described methods for cleaning industrial gas emissions is the need for frequent regeneration of the surface of the sorbent, especially at high concentrations of alkylene oxides and aldehydes in the gases being purified.

A known method of cleaning gas emissions from ethylene oxide on a cation exchange resin (US Patent No. 4828810, IPC B 01 J 8/00, publ. 09.05.89).

The method is applicable only for small amounts of ethylene oxide in gas emissions, in addition, over time, the resin loses activity, which leads to the need for its complete replacement.

A known method for the continuous removal of ethylene oxide from gas emissions by passing a gas stream through a 0.35-1.5 N aqueous acid solution (US Patent No. 4517167, IPC B 01 D 53/34, publ. 14.08.85).

The described cleaning method is applicable only with a small and stable gas flow rate.

A known method of purification of gases from aldehydes by absorption with an aqueous solution of an organic acid, followed by evaporation of the solution (US Patent No. 4595788, IPC C 07 C 005/09, publ. 26.11.84).

After evaporation, the solution is concentrated toxic waste products that must be disposed of.

Closest to the proposed is a continuous method for purifying industrial gas emissions from ethylene oxide (Muller U.-Absorption und Reaction zur Enhernung von Etylenoxid aus Abluft. - Chemische Ingineur Technik, 1990, No. 3, p .97). Gaseous emissions are passed through an absorption column irrigated with an absorbent having a temperature of 20 ° C. As the absorbent use water containing glycols formed in the process of hydration of ethylene oxide. The purified gas from the top of the column is discharged into the atmosphere, and the absorbent saturated with ethylene oxide from the bottom of the column is sent to the reactor, where at 60 ° C and stirring, ethylene oxide in the presence of phosphoric acid as a catalyst reacts with water to form ethylene glycols. After cooling to 20 ° C, the absorbent from the reactor is again sent to irrigate the absorption column.

The high speed of the hydration reaction in the presence of acid makes it possible to efficiently purify gases from ethylene oxide, but the use of special acid-resistant equipment is required.

The objective of the invention is to provide effective purification of industrial gas emissions from oxides of alkylene and carbonyl compounds.

The problem is solved by the method of purification of industrial gas emissions containing alkylene oxides and carbonyl compounds by absorption of an aqueous solution of glycols followed by hydration of alkylene oxides and recycling of the glycol solution to the absorption stage, while gas emissions are cooled before the absorption stage, and an aqueous solution is used as absorbent glycols containing 10-60 wt.% glycols and an additional 0.1-5.0 wt.% alkali.

In the proposed method, the gas emissions to the absorption stage are cooled to a temperature of minus 5 to minus 40 ° C.

The absorbent after hydration of alkylene oxides is subjected to reductive hydrogenation.

As aqueous solutions of glycols, aqueous solutions can be used, for example, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol or mixtures thereof.

Sodium or potassium hydroxides can be used as alkali.

Reductive hydrogenation is carried out with hydrogen in the presence of a heterogeneous hydrogenation catalyst, for example, Nickel Raney or others.

The proposed method for cleaning industrial gas emissions includes four main stages:

- cooling the flow of gas emissions;

- absorption of alkylene oxides and carbonyl compounds;

- hydration of alkylene oxides;

- reductive hydrogenation.

At the first stage, when cooling gas emissions, alkylene oxides and carbonyl compounds condense, which reduces their content in gas emissions.

In the second stage, in the absorption column, the remaining non-condensed alkylene oxides and carbonyl compounds are absorbed by an aqueous solution of glycols containing 10-60 wt.% Glycols and 0.1-5.0 wt.% Alkali. The gases thus purified are discharged into the atmosphere, and the absorbent containing the absorbed alkylene oxides and carbonyl compounds is sent to hydration.

In the third stage, hydration is carried out at elevated temperature to remove alkylene oxides from the absorbent, and glycols are formed.

In the fourth stage, carbonyl compounds and the remaining alkylene oxides are reduced with hydrogen to alcohols.

The implementation of the proposed method of purification of industrial gas emissions containing alkylene oxides and carbonyl compounds is illustrated by the following examples.

Example 1

Purified industrial gas emissions from the production of polyethers containing 325 g / m ³ propylene oxide, 0.2 g / m ³ acetaldehyde and 0.2 g / m ³ propionic aldehyde, 0.02 g / m ³ acetone, the rest is nitrogen, are fed with flow rate of 6000 m ³ / h to condenser 1 (drawing), where propylene oxide, aldehydes and acetone condense at a temperature of minus 30 ° C. Next, a gas with non-condensed propylene oxide, aldehydes and acetone enters the lower part of the packed absorption column 2. An absorbent containing 20 wt.% Propylene glycol and 2 wt.% NaOH is fed to the upper part of the absorption column. Absorbent consumption for column irrigation is 80 m ³ / h. The purified gases after absorption of propylene oxide, aldehydes and acetone are discharged into the atmosphere, and the saturated absorbent from the bottom of the column 2 is sent via pump 3 to the heat exchanger-recuperator 4, where the absorbent is heated to a temperature of 60 ° C due to the heat of the return absorbent. Next, the saturated absorbent is sent to the heat exchanger 5, where it is heated to a temperature of 100 ° C by steam supplied to the annular space with a pressure of 3 kgf / cm ² , after which the absorbent is sent to the tank 6, where, in the presence of alkali, propylene oxide reacts with water to form propylene glycol. Using the pump 7, the absorbent from the tank 6 is fed to the hydrogenation reactor 8, where, in the presence of a heterogeneous Nickel Raney catalyst, aldehydes, acetone, and the remaining propylene oxide are reduced to isopropyl and ethyl alcohols by hydrogen supplied to the lower part of the reactor 8 through distribution devices. The temperature in the reactor is 100 ° C, the pressure is 2 kgf / cm ² . From the top of the reactor 8, the gas-liquid mixture is sent to the separator 9, where the liquid absorbent is separated from the gas phase. Gas by compressor 10 is sent to the hydrogenation reactor 8 together with additionally supplied fresh hydrogen, and the absorbent is sent to the heat exchanger-recuperator 4 to heat the saturated absorbent discharged from the bottom of the column 2. Next, the absorbent is cooled in the heat exchanger 11 to a temperature of 20 ° C supplied into the annular space water with a temperature of 15 ° C, after which it returns to the column irrigation 2. As glycols accumulate, a part of the absorbent is removed from the separator 9. To replenish the absorbent, it is supplied to the pump inlet 7 fresh absorbent.

The gas leaving column 2 contains 0.005 g / m ³ propylene oxide, 0.0005 g / m ³ acetaldehyde, 0.0005 g / m ³ propionic aldehyde, and 0.0001 g / m ³ acetone.

Examples 2-5

The method of purification of industrial gas emissions containing alkylene oxides and carbonyl compounds is carried out similarly to that described in example 1.

The cleaning conditions are shown in table 1. Table 2 presents the results of the analysis of purified gas emissions.

As can be seen from the above examples, the proposed method allows for the efficient purification of industrial gas emissions from alkylene oxides and carbonyl compounds to environmentally friendly concentrations.

Table 1 Example No. The composition of the cleaned gas emissions, g / m ³ The composition of the absorbent, wt.% The temperature of the gas emissions in the condenser 1, ° C Ethylene oxide Propylene oxide Ace Talde Guide Propionic Aldehyde Acetone Ethylene glycol Dietary Leng Liquol Trieti Leng Licol Propi leng liquor Dipro-Pileng-Liquor Alkali one - 325 0.2 0.2 0.02 - - - twenty - 2.0 minus 30 2 590 - 2.0 - - 40 twenty 3 - - 1,0 minus 40 3 - 59 - 2.6 - - - - 10 - 0.1 minus 5 four - 770 0.4 0.3 - - - - 54 6 5,0 minus 35 5 392 259 3.9 1.3 - thirty 5 - fifteen 2 1,5 minus 25

table 2 Example No. The composition of the purified gas emissions, g / m ³ Ethylene oxide Propylene oxide Acetaldehyde Propionic Aldehyde Acetone one - 0.005 0,0005 0,0005 0.0001 2 0.004 - 0,0009 - - 3 - 0.003 - 0,0007 - four - 0.003 0,0004 0,0004 - 5 0.004 0.002 0,0009 0,0004 -

Claims (3)

1. The method of purification of industrial gas emissions containing alkylene oxides and carbonyl compounds by absorption with an aqueous solution of glycols followed by hydration of alkylene oxides and recycle of the glycol solution to the absorption stage, characterized in that the gas emissions are subjected to cooling before the absorption stage, and water is used as an absorbent a glycol solution containing 10-60 wt.% glycols and an additional 0.1-5.0 wt.% alkali. 2. The method according to claim 1, characterized in that the gas emissions to the stage of absorption are cooled to a temperature of minus 5 - minus 40 ° C. 3. The method according to claim 1, characterized in that the absorbent after hydration of alkylene oxides is subjected to reductive hydrogenation.