JPS624427A - Selective absorption of sulfur dioxide from gas containing sulfur dioxide and carbon dioxide - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for selectively removing sulfur dioxide gas from a gas stream in the presence of carbon dioxide.

The absorbent that removes sulfur dioxide is regenerated, thereby making it possible to reuse the absorbent and allowing continuous operation of the process.

Numerous patents and publications exist that describe techniques for removing sulfur compounds from gas streams containing them.

Until now, the most common techniques have been to use one or more acid gases, hydrogen sulfide (H2S), sulfur dioxide (S02),
Carbonyl sulfide (CO8) and carbon dioxide (CO2)
t-To process all natural gas with aqueous liquid poor (with respect to acid gases) to produce a rich absorbent stream and heat treat the rich absorbent stream to produce a lean stream that can be recycled. This is a technology used for A number of compounds have been suggested and used as absorbents, some of which selectively remove H2S or co2'2, and others which generally remove as much of each of the acidic gases present. It has the property of removing.

There is now a renewed interest in coal-fired boilers, etc., as well as greater environmental concerns, and it is becoming increasingly important to remove sulfur dioxide from the flue gas produced in such plants without removing the main part of the carbon dioxide. There is a need to provide a low pressure (atmospheric pressure or below), low temperature, selective method of removal. A commercially desirable feature of this absorbent would be the ability to regenerate the absorbent from the absorbed gas, making it reusable.

One method of 5O2t-removal that is widely used today is limestone scrubbing. The disadvantage of this method is that the solid waste, often contaminated with fireash,
A large amount of calcium sulfite-sulfuric acid is formed, which requires disposal. In areas of the country where pulp and paper operations are carried out, the waste is often usable;
Such cases are rare.

Other methods that have recently come to the forefront are U.S. Patent No. 4.36a1
The use of potassium or sodium salts of citric acid as disclosed in No. 34. Although the absorbent can be regenerated and recycled, the cost of replenishment can be high due to the formation of thermally stable salts. Additionally, it is necessary to use stainless steel throughout the plant to prevent excessive corrosion of the metal.

It would be advantageous to provide a method that satisfies the following requirements = (α) selectively absorbing sulfur dioxide and other gases,
(b) have low replenishment costs; (C) have low operating costs; and (d) allow for economical construction of the device, allowing for large volumes of gas flow at low pressures, e.g. , flue gases can be treated to reduce or eliminate the sulfur dioxide content of such gases.

Surprisingly, the method of the invention satisfies the aforementioned objectives. This method processes a gas stream containing sulfur dioxide and carbon dioxide in the general formula: Sulfur dioxide is selectively removed from the gas stream by contacting with an aqueous solution of a compound of hydrogen atoms or C1-C5 alkyl.

The gas stream usually contains hydrocarbons, natural or synthetic and/or other acid gases (flue gases) associated with combustion gases (flue gases).
For example, it also contains one or more of H2S or CO3. Also, for purposes of the present invention, the gas stream need not contain carbon dioxide. However, when carbon dioxide is present in the gas, the method of the present invention can selectively remove sulfur dioxide. This method is
Using a lean rlean aqueous absorbent solution of a compound of formula (I), preferably at a concentration of 0.1 molar to the saturation point, a rich rlean containing a large proportion of SO□ and very little Co2t- is used. The absorbent is removed from the absorber (contacter) and thermally regenerated to produce a lean absorbent solution for recycling to the absorber.

The absorber is preferably operated at temperatures between 5 and 95°C and near atmospheric pressure. Although higher temperatures and pressures will not adversely affect the method, it may be necessary to modify the equipment to handle the higher temperatures and pressures.

The concentration of sulfur dioxide in the gas stream can vary from about 10 pP to about 45 volume J of the gas stream being treated.

The regeneration method can be one of the conventional methods used in conventional gas sweetening as well as by steam stripping.

Integrated absorption device - stripper as shown in Figure 1
The (contactor-regenerator) was constructed by connecting ten trays of Oldershaw columns 10 with nomoiso. The tower has an inner diameter of 2.5 inches (1 inch).
and tray spacing 3.17 an (1,25 inch)
't-, receiving the lean absorbent solution at its upper end 11 and the contaminated gas stream at its lower end 12. The upper part 13 and the lower part 14 were each independently connected by pipes to collect the treated gas in the upper part and the rich absorbent in the lower part, respectively. The rich absorbent was sent to the shell and tube cooler 15. The cooler 15 passed hot lean absorbent to the shell side and cool rich absorbent to the tube side. The enriched absorbent is then sent to the upper end 16 of the stripper 17. Stritz, t'-17 is 5.35cm
It had an inside diameter of 0.635 m (2 feet and 1 inch) filled with a (]/4 inch) Berl saddle. The sulfur dioxide exits the upper part 18 with some water vapor and is sent to the condenser 19, where the water vapor is condensed.
The sulfur dioxide was then sent to a degasser 20 from which it was discharged and the condensate was returned as reflux to the upper part of the stripper 17 by pump 2OA.

The liquid collected in the lower part 21 of the stripper 17 was substantially poor absorbent and a portion of it was passed through the rally boiler 22 and returned below the stripper filling section. The lean absorbent residue collected in the lower part 21 was sent to the cooler 5, where it gave most of its heat to the rich absorbent. The cold absorbent was withdrawn to the intake side of the pump 23, passed through another cooling device 24, and then sent to the absorbent lean absorbent feed point.

The following examples provide a detailed explanation of the invention.

Example 1 Data collected from several experiments are listed in the table below.

Alphabetical titles refer to the flow indicated by the alphabet in FIG.

Example 2 A series of tests was conducted to screen compounds known to absorb so2'1 for their CO□ absorption properties. The apparatus, a steel bomb filled with glass bulbs, was fitted with a valve through which the CO□ and absorbent could be added. The cylinder was also fitted with a pressure sensor.

The bomb was pressurized to 760 mHg with CO□ and filled with a measured amount of a 1 molar solution of a particular absorbent.

The Bonn M was then left at ambient temperature (approximately 24° C.) or heated as shown in the table below, and the pressure drop was measured over a 10 minute period for each condition. The results were as follows.

Table ■ Wednesday 24
0.0461 mole triethanolamine
24 0.2750 None 1 1 mol L4-dimethylpiperazinone 23
0.0875 None 1 mole triethylene glycol 24
None 21 moles of neutralized citric acid 24
None 31 moles EDTA'
24 1.3365 0.95 74 0.76 1 mol Na25o3 24
0.1744 0.16 74 0.1 1 High losses due to high vapor pressure.

2 Decomposes in the presence of oxygen.

3 Solvent in U.S. Patent No. 4.36+3,134;
Corrosive.

4 Diethylenetriamine Example 3 The absorption properties of various compounds 2c○ and S02 were tested using the 10-tray Olderschau column described above.Synthesis of the composition described in 1. was fed at 55° C. and 4151/min. The top liquid flow was approximately 10 cc/min. The incoming and outgoing gases were analyzed and the total weight percent of absorbed CO□ and/or S02 was calculated. The results are listed below.

Table ■ 5cc/min liquid supply: 781m*Hg absolute pressure, approximately 0.195ft1min gas supply and o, 1s4
ft1 min gas withdrawal, temperature °C Absorbent supply 56 56 57 Gas supply 25 25 25 Feed gas, weight % N277.17 75.18 73.27 Go219
．． 65 19.70 19.00So23.18
5.12 7.73 Gas, lightning, 1 regret N279.78 80.35 78.97C○220
．． 52 19.65 20.76SO2,OOl
Ha01. 269 This experiment established that NNDP will absorb more than one mole of 5O2t- for every mole of it.

Stripper 4 cc/min liquid supply; 76 lmmHg absolute pressure S○2 wt% (in) 7.5 7.5 7.5
7.5 Liquid (output) 2,38 2.29 2.
14 2.03 Temperature, °C Supply 81 81 82 82 Lower 104 104 104 103 Table V 5 cc 7 min liquid supply; 781 rrrmHg
Pressure gas enters ft1 minute 0.173 0.176 0.
176 0. IT7 comes out 0.169
0.175 0.175 0.176 Temperature, °C Liquid supply inlet 85 81 80 80
Upper part of tower 56 55 54 Lower part of gas tower with 55 people 25 24 21 22 Gas entering, weight % N277.83 78.11 77.85 77
．． 68Go220.56 20.27 20.66
20.75SO21,611,621,501,5
8 Output gas, weight% N279.10 79.4n 79.03 78
．． 92Go220.90 20.60 20.97
21.08SO too low to measure p=sOf Leger 8 8 10
Pressure liquid supply for stripper 761 Hg by Drager 2 (Drager), cc/e 4 4 5 3
SO2, wt% Liquid (in) 3.12 3.09 1
．． 80 1.87 Liquid (output) 1.52
1.67 1.44 1.42 Temperature, °C Supply 84 84 80 90
Lower part 100 102 102 101
Supply of liquid for SOCZ; 781 mmHg pressure gas,
ft1 minute enters 0.195 0.195 0.
195 0.195 comes out 0.184
0.184 0.185 0.184 Temperature, °C Inlet of liquid supply tower 80 80 80 80 Outlet 55 55 55 55 Lower part of gas tower 21 22 22 21 Incoming gas, weight % N278.41 78.93 77.27 78
．． 41Go219.97 19.55 21.11
19.97So21.62 1,51 1,6
1 1.62 Outgoing gas, weight % N278.53 80.15 78.54 79
．． 70Go221.47 19.85 21.46
20.30So2. 0003. 00
08. 0003. 0003 Solution So,)'' Supply of liquid for 3 8 3 3 strippers 4 CCZ by Luger: 761 mmHg pressure SO
2. Weight related liquid (entered) 2.94 2.72 2.7
4 2.74 Liquid (output) 0.71 0.
72 0,82 0.72 Temperature, °C Supply 80 86 87 87 Lower part 102 103 102 1
02 As established by these two experiments, SO
2 is temperature above 50℃, normal water/gas cleaning temperature%5%
It is selectively absorbed with respect to CO2 at concentrations of .

Example 4 A 10% by weight aqueous solution of 1-methyl-2-morpholinone in deionized water was prepared at 1.27 crn
2" x 2 ft) well-packed (low) absorption tower at a normal rate of 3.171 cc/min.
/min N2.1.2t/min air, 750cc/min (7) Go 2 Oh L Hif 0 CC/min no 80
A mixture of 2 (I N t % of 5o2) was fed to the bottom of the column. The liquid extracted from the bottom of the tower is 1.27c1
nX0.61m (1/2" x 2 feet) 0.6cm
(1/4") of Berl sodium and fed to a stripper column equipped with a heating bath reboiler.

The gas leaving the absorber contains 0.45% by weight of SO2'1 and the liquid of the absorber contains 0.63% by weight of Go2.
96.81 of SO□ was stripped from the absorbent in the stripper column. This represents an absorption of 1/2 mole per mole of 1-methyl-2-morpholinone for a 10 part solution and represents the ability to regenerate the absorbent for recycling.

[Brief explanation of the drawing]

FIG. 11 is a diagram of the essential components of the method used to treat gas according to the invention. Patent applicant The Dow Chemical Company (5 others) Procedural amendment (method) Showa θ year T 47th application No. 7 ≠ ≠ ρ / No. 2 jump% t-4
1shi) 7J-♂Two pieces of 1゛shi included p゛nuprano 5
丙ν悸47 pieces. , BiZ, 1 shaku'1F and revenue 3, Relationship with the case of the person making the amendment Applicant Address Stone, (723) The Tara γ Mill - 7J'+
/ % --4, Agent 5, Date of amendment order: February 1986, Co. day (shipment date) method■,

Claims (1)

[Claims] 1. A gas flow containing sulfur dioxide and carbon dioxide is defined by the general formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (I) In the formula, X is an oxygen atom or NR', and R' is a hydrogen atom or a C_1-C_5 alkyl, and R is a hydrogen atom or a C_1-C_5 alkyl. How to remove. 2. The method according to claim 1, wherein X is oxygen. 3. The method according to claim 1, wherein X is NR'. 4. The method of claim 3, wherein R and R' are both C_1-C_5 alkyl. 5. The method according to claim 1 or 4, wherein the compound of formula (I) is 1,4-dimethylpiperazinone. 6. The method according to claim 1, wherein the compound of formula (I) is 1-methyl-2-morpholinone. 7. The method of claim 1, wherein the method is continuous. 8. The method according to claim 1 or 7, comprising an additional step of regenerating the aqueous solution of the compound of formula (I). 9. Claim 1 comprising an additional step of recovering the gas substantially free of sulfur dioxide from the aqueous solution.
Or the method described in Section 7.