CN101143286A

CN101143286A - Method for removing COS from acid airflow

Info

Publication number: CN101143286A
Application number: CNA2006100415857A
Authority: CN
Inventors: 毛松柏; 朱道平; 丁雅萍; 叶宁; 黄晓燕
Original assignee: Research Institute of Nanjing Chemical Industry Group Co Ltd
Current assignee: Research Institute of Sinopec Nanjing Chemical Industry Co Ltd
Priority date: 2006-09-15
Filing date: 2006-09-15
Publication date: 2008-03-19
Anticipated expiration: 2026-09-15
Also published as: CN101143286B

Abstract

The invention belongs to the gas purification technology field. The invention uses a compound amine solution as absorbent, and proper amount of activator is added to totally remove H<SUB>2</SUB>S from airflow. When the removing rate is not high, the invention can remove most of the COS, and the absorbent can be regenerated and circulating used. The invention has a higher COS removing rate than the method by using conventional amine.

Description

From acid gas stream, remove the method for COS

Technical field:

The invention belongs to the gas purification technique field, be specifically related to from acid gas stream, remove the method for COS.This acid gas stream comprises natural gas, synthesis gas, refinery gas, liquefied petroleum gas etc.

Background technology:

Usually contain H in the industrial gasses ₂S, CO ₂With objectionable impurities such as COS, various mercaptan, thioethers, before further utilizing, they must removed totally, up to the present, the technology that is applied to the decarburization of qi exhaustion sulphur is descended hundreds of.Modal is that acid gas stream contacts in gas cleaning plant with organic solvent (or aqueous solution of organic solvent).A large amount of patent documentations have been arranged in these processes.Generally speaking, two kinds of different gas purification solvents are roughly arranged.

First kind is physical solvent, and what lean on is Physical Absorption.Typical physical solvent has the mixture of sulfolane and its derivative, straight chain acid amides, NMP (N-methyl pyrrolidone), N-alkyl pyrrolidone, relevant pyrrolidones, methyl alcohol and polyvinyl alcohol dialkyl ether.

Another kind is a chemical solvent.Based on chemical reaction, make sour gas generate the compound of easily removing.For instance, industrial the most frequently used chemical solvent is a hydramine, because the salt that generates decomposes easily or carried by steam gas easily, therefore amine can recycle.From air-flow, remove the MDEA that the reasonable amine of acid ingredient has monoethanolamine (MEA), diethanol amine (DEA), triethanolamine (TEA), diisopropanolamine (DIPA) (DIPA), amido ethoxy ethanol (AEE), methyl diethanolamine (MDEA) and added various activators.

Usually, above-mentioned solvent is to removing H ₂S and CO ₂Have higher efficient, but then there are many difficulties in COS.Physical solvent can be removed COS fully, but this process is inappropriate, because these physical solvents can absorb other linear paraffin, regeneration deals with very expensive.In the chemical solvent, primary amine and secondary amine and COS directly react the loss increase that generates metastable compound and cause effective amine, also can cause the corrosion of equipment simultaneously, and tertiary amine then only depends on physical dissolution to remove COS, and its effect is obviously very poor.

Therefore, there is Many researchers to propose suggestion, comprises removing COS:

Adopt the COS hydrolyst that COS is hydrolyzed into H ₂S and CO ₂, and then with alkanolamine solution with H ₂S and CO ₂Remove;

Air-flow is contacted with the mixed solvent of MDEA and DIPA, and here 50%～80% COS is hydrolyzed into H ₂S and CO ₂The remaining peralkaline amine liquid of the air communication that contains COS washs into Na ₂S or Na ₂CO ₃At last, Yu Xia COS removes by alkali lye.This process comprises three sections, all will regenerate for every section, therefore deals with expensive;

Air-flow is contacted with the pure amine solvent that has added catalyst, and COS is hydrolyzed into H ₂S and CO ₂After be absorbed and remove.But this method need be at CO ₂Could partly remove COS under the very high situation of removal efficiency.

Summary of the invention:

The present invention adopts a kind of varies aqueous solution to make absorbent, adds an amount of activator, can remove H from air-flow fully ₂S removes most COS; And at CO ₂Remove under the not high situation of rate, remove most COS, (as natural gas purification) reserve part CO in some processes ₂Need.

The present invention is achieved like this: it adopts a kind of aqueous solution absorbent and air-flow counter current contacting and removes H ₂S and COS, it is that 15-55%6 varies and weight ratio are the activator of 5-12% that absorbent contains weight ratio, varies is made up of methyl diethanolamine (MDEA) and diisopropanolamine (DIPA) (DIPA), and activator is made up of diazabicylo (DBU) and piperazine or diazabicylo (DBU) and morpholine.

The weight ratio of varies is preferably 30～50%, and wherein, MDEA:DIPA is 2-3: 1;

Activator is made up of with morpholine (MAL) diazabicylo (DBU) and piperazine (PZ) or diazabicylo (DBU), and wherein the ratio of diazabicylo and piperazine or diazabicylo (DBU) and morpholine is 1-3: 1.

In the varies aqueous solution used in the present invention, also can comprise additive as corrosion inhibitor, defoamer and similar components.Typically, the concentration range of these additives is 0%～5% (wt), and the use of these additives is that present technique field personnel are known.

Adopt the employed device of solvent removal COS of the present invention can with habituation use identical.Even the H in the air-flow ₂S, CO ₂And COS is removed by contacting with the mixed amine aqueous solution of the present invention.

Absorption process can one-time-reach-place, also can continuous several times carry out.Can use the solution of multiply to carry out the gas-liquid contact among the latter from the order that reduces successively by temperature to cat head at the bottom of the tower.

The rich solution that has absorbed acid gas is realized regeneration by decompression, can realize by choke valve.The energy that rich solution contains can reclaim by turbine.

Flash tank can be adopted when removing acid gas, also repeatedly flash distillation can be carried out.Rich solution passes through and further regenerates the back and then be recycled to absorption step after the flash distillation.

Any known equipment in this area may be used to absorb, regenerate and other step.

The specific embodiment:

Embodiment:

Below the invention will be further described by embodiment, its objective is in order to understand content of the present invention better, but it does not limit protection scope of the present invention.

Operating characteristics to concrete absorbent on an experimental rig is directly measured.The absorption tower internal diameter 20mm of test usefulness, interior dress φ 3 * 3 stainless steel θ ring, regenerator internal diameter 50mm, interior dress φ 6 * 6 * 1 porcelain Raschig ring, reboiler is equipped with in the regenerator bottom.

The unstripped gas for preparing (contains H ₂S14%, CO ₂9%, COS1043 * 10 _-6) entering the solution counter current contacting that absorption tower bottom and cat head enter, the acid gas in the gas is absorbed, and purified gas comes out to enter gas-liquid separator from cat head and reclaims emptying after institute's droplets entrained.

The rich solution that has absorbed acid gas leads to the regenerator top at the bottom of the absorption tower, contact and obtain regeneration with the steam counter-flow of rising in regenerator.Lean solution after the regeneration is sent into absorption tower jacking row and is absorbed after cooling.The gas that comes out from regeneration overhead enters the regeneration gas cooler with the recovery of the water vapour the gas, and regeneration gas is emptying after separating.

Certain at gas flow, the operating characteristics of different absorbents sees Table one.

Table one: the operating characteristics of different composite absorbers

Absorbent is formed	Purify in the gas of back
	Purify in the gas of back			H ₂S：×10 ^-6	CO ₂：v％	COS：10 ^-6
	MDEA50％	26	2.2	H ₂S：×10 ^-6	CO ₂：v％	COS：10 ^-6	531
MDEA10％+DIPA5％+DBU2.5％+MAL2.5％	MDEA50％	26	2.2	20	5.0	127	531
MDEA10％+DIPA5％+DBU2.5％+MAL2.5％	MDEA15％+DIPA8％+DBU8％+PZ3％	15	2.8	20	5.0	127	90
MDEA25％+DIPA12％+DBU5％+MAL3％	MDEA15％+DIPA8％+DBU8％+PZ3％	15	2.8	13	3.0	96	90
MDEA25％+DIPA12％+DBU5％+MAL3％	MDEA30％+DIPA10％+DBU2.5％+PZ2.5％	10	3.4	13	3.0	96	82
MDEA40％+DIPA15％+DBU8％+MAL4％	MDEA30％+DIPA10％+DBU2.5％+PZ2.5％	10	3.4	18	2.7	113	82

Table one data show uses absorbent composition of the present invention, and its removal efficiency to COS can obviously improve.

Claims

1. from acid gas stream, remove the method for COS, it is characterized in that it adopts a kind of aqueous solution absorbent and air-flow counter current contacting and remove H ₂S and COS, it is that 15-55% varies and weight ratio are the activator of 5-12% that absorbent contains weight ratio, varies is made up of methyl diethanolamine (MDEA) and diisopropanolamine (DIPA) (DIPA), and activator is made up of diazabicylo (DBU) and piperazine or diazabicylo (DBU) and morpholine.

2. according to the described method of claim 1, the weight ratio that it is characterized in that varies is 30～50%.

3. according to the described method of claim 1, it is characterized in that the weight ratio of MDEA and DIPA is 2-3 in the varies: 1.

4. according to the described method of claim 1, the weight ratio that it is characterized in that diazabicylo and piperazine is 1-3: 1.

5. according to the described method of claim 1, the weight ratio of its feature diazabicylo and morpholine is 1-3: 1.

6. according to the described method of claim 1, it is characterized in that absorbent can regenerate.

7. according to the described method of claim 1, it is characterized in that having added in the absorbent an amount of corrosion inhibitor, defoamer and antisludging agent.