The method of separation of acetylene from waste gases

 

(57) Abstract:

The invention relates to chemical technology, more specifically, to improved method of separation of acetylene from waste gases for 1,4-butandiol (1,4-BID) on the basis of acetylene and formaldehyde. Describes a method of separation of acetylene from waste gases production of 1,4-butandiol from acetylene and formaldehyde and production of N-vinylpyrrolidone with waniliowym-pyrrolidone containing acetylene, nitrogen, methanol and formaldehyde, while implementing the absorbance at a pressure of 0.02 to 1.0 MPa using as the absorbent mixed solvent containing N-organic and 1,4-butanediol in a concentration of the latter in the absorbent 1-8 wt.% with a volumetric ratio of the discharge gas absorbent, equal (5-30):1, followed by desorption of acetylene from the saturated adsorbent at elevated temperature and pressure of 0.005-0.02 MPa. The technical result - the possibility of utilization of acetylene from waste gas, improving the quality and yield of the target product.

The invention relates to chemical technology, more specifically, to improved method of separation of acetylene from waste gases for 1,4-butandiol (the cation-pyrrolidone (Handbook of Neftekhimik edited by S. K. Ogorodnikova, so 2, L.: Chemistry, 1978, 592 S.).

The waste gases of these processes include the addition of acetylene, nitrogen, admixture of methanol and formaldehyde. According to the current technology for reducing the amount accumulated in the circulation acetylene inert gases, impurities, formaldehyde and methanol portion of the acetylene discharge to the flare for combustion (40-50 nm3/h).

Below is a method of purification of acetylene from the above impurities, allowing you to select from waste gases acetylene with a concentration of 98 wt.% and above, which can be returned to the reactor for the synthesis of 1,4-BID and N-VP.

A known method for the recovery of acetylene from mixtures obtained by pyrolysis and cracking of oil fractions, absorption of selective solvents (patent U.S. CL 55/40, B 01 D 53/16, N 4274841, Appl. 28.03.80, N 134948, publ. 23.06.81) prototype.

According to the method prototype gas pyrolysis or catalytic cracking, in addition to containing acetylene, methane, ethane, ethylene, hydrogen, carbon monoxide, is directed under pressure 1-19 ATI in the lower part of the absorber. In the upper part of the absorber serves a selective solvent, which is used as dimethylformamide, N-organic (N-MP), butyrolactone, methylethylke the second gas, containing 5-7% of acetylene, which is sent for incineration. On bottom of the absorber emit saturated with acetylene absorbent. The latter is heated in the heat exchanger and share in desorber in the gas phase, enriched with acetylene, and the liquid phase, which is subjected to additional Stripping to extract acetylene. As a result, there acetylene purity 98-99% vol. with the output from potential 78-88 wt.%.

The disadvantage of this method is low efficiency in the allocation of acetylene from waste gases production of 1,4-BID and N-EP, containing impurities of nitrogen, methanol, formaldehyde, which are absent in the gas composition, of which there acetylene in the method prototype. As follows from the data of example 6 of the present application, in which the absorbent use pure N-MP, of the combined stream of waste gas industries 1,4-BID and N-VP containing 0,47% vol. methanol, 0,73% vol. formaldehyde, 14,3 about. % nitrogen, using the prototype method produce acetylene purity 96,6% vol. with potential output 79,1 wt.%.

Known for a number of other patents on allocation of acetylene from gases of pyrolysis and cracking, used different absorbents and technology desorption of acetylene (patent Germany, to osobov the same, as in the above method.

The purpose of the present invention is the utilization of acetylene from waste gas industries 1,4-BID and N-VP, improving the quality and yield of the target product.

This goal is achieved by the absorption of waste gas mixed solvent comprising as a basic component of the N-MP, and as a promoter of the absorption process 1-8 wt.% 1,4-butanediol (1,4-BAD) the product obtained by hydrogenation of 1,4-BID.

The absorption of acetylene is carried out in the absorber efficiency 5-10 theoretical plates (so-so) at a temperature of 20-60oC, a pressure of 0.02 to 1.0 MPa, and a volume ratio discharge gas absorbent, equal (5-30):1. Saturated with acetylene absorbent sent to desorber efficiency 5-15 so so, where at a pressure of 0.005-0.02 MPa and a temperature of 100-130oC separate target acetylene from the absorbent. Acetylene is sent to the reactor for the synthesis of 1,4-BID, N-VP and absorbent recycle to the absorber.

Introduction to the absorbent diatomic alcohol is 1,4-butanediol - allows you to more fully cleaned allocated acetylene from nitrogen, as well as from impurities methanol and formaldehyde to obtain the target product purity 98% and above potential output 88-94 wt. %. the 96,6% vol. potential output is not more than 79 wt.% (see examples).

Salient features of the invention are:

the process of selection of acetylene from waste gas, containing in addition to acetylene, nitrogen, methanol, formaldehyde absorption solvent that includes as a basic component of the N-MP, and as a promoter of absorption of 1,4-BAD with its concentration in the absorbent 1-10 wt.% and the volumetric ratio of the discharge gas absorbent (5-30):1;

the process of absorption at a pressure of 0.02 to 1.0 MPa, desorption at a pressure of 0.005-0.02 MPa.

Failure to follow the above ranges of the proposed options do not allow to separate acetylene purity 98% with high output.

Applicants not known published sources, which offer a way of separating acetylene from gases containing the totality of such impurities as nitrogen, methanol, formaldehyde. This indicates compliance with the essential distinctive features of the way the criteria of novelty and non-obviousness.

The advantage of the proposed method compared with the method of the prototype is to improve the quality and yield of the target product.

Example 1

(Average values declare p is 4,20; methanol - 0,47; formaldehyde - 0,73 with a flow rate of 55 nm3/h to send in the lower part of the absorber efficiency 6 so-so In the upper part of the absorber serves 3 m3/h absorbent composition, wt.%: N-MP - 96,8; 1,4-BAD - 3,2. The process of absorption of acetylene is carried out at a volume ratio discharge gas absorbent is 18:1, the temperature of the 34oC, a gauge pressure of 0.05 MPa. Undissolved gas from the top of the absorber with a flow rate of 11.5 nm3/h composition, vol.%: acetylene - 35,88; nitrogen - 64,06; methanol - 0.05; formaldehyde - 0,01 sent to flare. Saturated absorbents consumption 3050,5 kg/h to send in the upper part of desorber. The desorption process is carried out at a pressure of 0.015 MPa and a temperature in the cube of desorber 123oC. From the top of desorber allocate target acetylene with a flow rate of 43 nm3/h composition, vol.%: acetylene - 98,7; nitrogen - 1,23; methanol - 0,04; formaldehyde - 0,03. Separated from the gases N-MP recycle to the stage of absorption. The yield of the desired acetylene is to 91.4 wt.% from the potential content in the discharge gas.

Example 2

The lower limit of the concentration of 1,4-BAD in absorbent)

Raw materials of the composition shown in example 1, is subjected to the process of absorption and desorption analogously to example 1 with the difference that the concentration of 1,4-BAD in absorb the rod, vol.%: acetylene - 98,1; nitrogen - 1,74; methanol - 0,09; formaldehyde - 0,07. The yield of the desired acetylene is 89,7 wt.% from the potential content in the discharge gas.

Example 3

(Upper limit of the concentration of 1,4-BAD in absorbent)

Raw materials of the composition shown in example 1, is subjected to the process of absorption and desorption analogously to example 1 with the difference that the concentration of 1,4-BAD in the absorbent meets the upper declare the border, namely 8 wt.%.

The result is the target product composition, vol.%: acetylene - 99,2; nitrogen - 0,77; methanol - 0,02; formaldehyde is 0.01. The yield of the desired acetylene is of 92.6 wt.% from the potential content in the discharge gas.

Example 4

The lower limit of the ratio of the discharge gas absorbent)

Raw materials of the composition shown in example 1, is subjected to the process of absorption and desorption analogously to example 1 with the difference that the ratio of the discharge gas absorbent meets the bottom of the claimed boundary, namely 5:1.

The result is the target product composition, vol.%: acetylene was 99.4; nitrogen - 0,54; methanol - 0,04; formaldehyde - 0,02. The yield of the desired acetylene is to 93.3 wt.% from the potential content in the discharge gas.

Example 5

The upper boundary of the ratio is orble analogously to example 1 with the difference, what is the ratio of the discharge gas absorbent meets the upper declare the border, namely 30:1.

The result is the target product composition, vol.%: acetylene - 98,3; nitrogen - 1,53; methanol - 0,10; formaldehyde - 0,07. The yield of the desired acetylene is 88.5 wt.% from the potential content in the discharge gas.

Example 6

(The lower bound of excess pressure absorption)

Raw materials of the composition shown in example 1, is subjected to the process of absorption and desorption analogously to example 1 with the difference that the excess pressure absorption corresponds to the lower claimed the border, namely 0.02 MPa.

The result is the target product composition, vol.%: acetylene is 98.2; nitrogen is 1.48; methanol - 0,24; formaldehyde - 0,08. The yield of the desired acetylene is 88.2 wt.% from the potential content in the discharge gas.

Example 7

(The upper bound excess pressure absorption)

Raw materials of the composition shown in example 1, is subjected to the process of absorption and desorption analogously to example 1 with the difference that the excess pressure absorption meets the upper declare the border, namely 1.0 MPa.

The result is the target product composition, vol.%: acetylene - 99,3; nitrogen - 0,65; methanol - 0,03; formaldehyde - 0,02. the 8

(The lower bound of excess pressure desorption)

Raw materials of the composition shown in example 1, is subjected to the process of absorption and desorption analogously to example 1 with the difference that the excess pressure desorption corresponds to the lower claimed the border, namely 0,005 MPa.

The result is the target product composition, vol.%: acetylene - 99,1; nitrogen - 0,85; methanol - 0,02; formaldehyde - 0,03. The yield of the desired acetylene is about 91.8 wt.% from the potential content in the discharge gas.

Example 9

(The upper bound excess pressure desorption)

Raw materials of the composition shown in example 1, is subjected to the process of absorption and desorption analogously to example 1 with the difference that the excess pressure desorption meets the upper declare the border, namely 0.02 MPa.

The result is the target product composition, vol.%: acetylene - 98,4; nitrogen is 1.48; methanol - 0,07; formaldehyde - 0,05. The yield of the desired acetylene is 89,3 wt.% from the potential content in the discharge gas.

Example 10 (method prototype)

Raw materials of the composition shown in example 1, is subjected to the process of absorption and desorption analogously to example 1 with the difference that as absorbent use pure N-MP. The process abs is absorbent, equal to 50:1. The desorption process is carried out at a gauge pressure of 0.05 MPa and a temperature of 120oC. the result of the target product composition, vol.%: acetylene - 96,6; nitrogen - 2,7; methanol - 0,22; formaldehyde - 0,48. The yield of the desired acetylene is 79,1 wt.% from the potential content in the discharge gas.

The method of separation of acetylene from waste gases production of 1,4-butandiol from acetylene and formaldehyde and production of N-vinylpyrrolidone with waniliowym-pyrrolidone containing acetylene, nitrogen, methanol and formaldehyde, wherein implementing the absorbance at a pressure of 0.02 to 1.0 MPa using as the absorbent mixed solvent containing N-organic and 1,4-butanediol, when the concentration of the latter in the absorbent 1 - 8 wt.%, with a volumetric ratio of the discharge gas absorbent is (5 - 30) : 1, followed by desorption of acetylene from the saturated adsorbent at elevated temperature and pressure of 0.005 - 0.02 MPa.

 

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