KR900007861B1 - Selective removing method of sulphur dioxide - Google Patents

Abstract

A sulphur dioxide is removed by contacting gas streams containing SO2 and CO2 with an aqueous solution of formula (I) cpd. at 5-95 deg.C. In (I), X is O or NR'; R' is H or C1-5 alkyl; R is H or C1-5 alkyl. Cpd. (I) is pref. 1,4-dimethylpiperazinone or 1methyl-2-morpolynome. The concn. of SO2 in the gas streams is 10ppm-45 vol.%.

Description

Selective Removal of Sulfur Dioxide from Sulfur Dioxide and Carbon Dioxide-containing Gas Streams

1 shows a schematic of the essential components of the method used to process a gas in accordance with the present invention.

The present invention is directed to a method for selectively removing sulfur dioxide gas from a gas stream in the presence of carbon dioxide. Absorbents that remove sulfur dioxide are regenerated, thus allowing their reuse and continuous operation of the method.

Many patents and literature describe techniques for removing sulfur compounds from gas streams containing sulfur compounds. The most common technique is to add a natural gas containing at least one of acid gas, hydrogen sulfide (H ₂ S), sulfur dioxide (SO ₂ ), carbonyl sulfide (COS) and carbon dioxide (CO ₂ ) to an aqueous liquid lean (acid gas). A technique for producing a rich absorbent stream by treating it with an absorbent and regenerating it by heat treatment to produce a recyclable lean stream. Many compounds have been shown and used as some absorbents that selectively remove H ₂ S or CO ₂ , and other conventional absorbents that remove as much of each acid present as possible.

Nowadays, with great interest in the environment and renewed interest in coal-fired boilers, etc., optional low pressure (atmospheric or sub-atmospheric) pressure to remove sulfur dioxide from flue gas emitted from these plants without removing most of the carbon dioxide. ), It is necessary to provide a low temperature method. Commercially preferred absorbent modalities should be such that the absorbent can be regenerated from the absorbed gas and reusable.

One of the widely used methods of removing SO ₂ is lime removal. A disadvantage of this method is the formation of calcium sulfite-sulfate solid waste, which often needs to be disposed of in large volumes contaminated with dust. In countries where paper pulp operations are performed, waste is often useful but not prevalent in this case.

Another method recently used in industrial fronts is the use of potassium citrate or sodium citrate described in US Pat. No. 4,366,134. The absorbent material is regenerated and recycled, but the manufacturing cost may be high due to the heat stable salts formed. In addition, it is necessary to use stainless steel for all plants to prevent excessive corrosion of the metal.

(a) selectively absorbs sulfur dioxide, with the exception of the remaining acid gases, in particular carbon dioxide; (b) low chemical manufacturing costs; (c) operation cost is lowered; (d) It would be advantageous to choose a method that would allow the device construction to be economical, thereby treating low pressure high volume gas streams such as flue gas to reduce or eliminate the sulfur dioxide content of such gas.

Surprisingly, the method meets the aforementioned purpose. This method selectively removes sulfur dioxide from a gas stream containing sulfur dioxide and carbon dioxide by contacting the gas with an aqueous solution of the compound of formula (I).

Wherein X is an oxygen atom or NR ', wherein R' is a hydrogen atom or C ₁ -C ₂ alkyl; R is a hydrogen atom or C ₁ -C ₅ alkyl.

In addition, the gas stream may contain one or more of the remaining acid gases (eg H ₂ S or COS) typically associated with hydrocarbons, natural or synthetic and / or combustion gases (flue gas). In addition, for the purposes of the present invention, the gas stream does not need to contain carbon dioxide. However, if carbon dioxide is present in the gas, the method allows for selective removal of sulfur dioxide. This method preferably uses an aqueous solution of lean absorption of the compound of formula (I) at a concentration of 0.1 mol to saturation point. A lean absorbent solution is prepared to remove most of the SO ₂ and some CO ₂ rich absorbent from the absorption tower (contact tower) and thermally regenerate and recycle it to the absorption tower.

The absorption tower is preferably operated at 5 to 95 ° C. under almost atmospheric pressure conditions. Although it is necessary to modify the device design to handle high temperature and high pressure, practically high temperature and high pressure do not affect this method.

The sulfur dioxide concentration in the gas stream can vary from about 10 ppm to about 45 volume percent of the gas stream to be treated.

The regeneration method is not only one of the conventional methods used for conventional gas sweetening units but may also be a steam stripping method.

The integrated absorption tower-stripper (contact tower-regeneration tower) shown in FIG. 1 has a method of receiving a lean absorption solution at the upper end 11 and a contaminated gas stream at the lower end l2. Pipes are installed in 100,000 Oldershaw columns, 1 inch (2.54 cm) and tray spacing 1 1/4 inch (3.17 cm). The top portion 13 and the bottom portion 14 each independently connect pipes, and the treated gas is collected at the top portion, and the rich absorbent material is collected at the bottom portion. The rich absorbent is connected to the shell (shel1) and the tube cooler (15) and the tube to pass the hot lean absorbent material on the shell face and the cool rich absorbent material on the tube face. The rich absorbent material is then delivered to the upper end 16 of the stripper 17. The stripper 17 is a column having an inner diameter of 2 ft 1 in (0.635 mm) filled with l / 4 in (6.35 mm) Berl saddle. Sulfur dioxide is discharged to the top 18 with some water vapor and enters the condenser 19, where the water vapor is condensed and the condensate and sulfur dioxide enter the degassing apparatus 20, from which the ideal sulfur is exhausted and The condensate is recovered as a reflux to the top 18 of the stripper 17 through the pump 20A. The liquid collected at the bottom 21 of the stripper 17 is a lean absorbent material, some of which is passed through a reboiler 22 and recovered to the stripper under the filling. The remainder of the lean absorbent collected at the bottom 21 enters the cooler 15, where the remainder of the lean absorbent provides most of the heat to the rich absorbent. The cooling absorber flows into the input surface of the pump 23 and passes through another cooler 24 and then into the lean feed point of the absorption tower 10.

To illustrate the method, the following examples are provided.

Example 1

The data collected from several operations are described in the table below. Alphabet capital letters in FIG. 1 refer to a stream similarly represented in alphabet.

TABLE 1

1br / hr

The numbers are in equilibrium.

** N, N'-dimethylpiperazinone (or l, 4-dimethylpiperazinone)

Example 2

A series of tests are conducted to screen the efficiencies of various compounds known to absorb SO ₂ in terms of their absorption properties for CO ₂ . The valve is mounted on the iron vessel device filled with the glass ball bal1 in one word, thereby adding CO ₂ and an absorbent material. In addition, a pressure sensing mechanism is mounted on the container. The vessel is pressurized to 760 mmHg with CO ₂ and filled with the measured amount of the unique 1M absorber solution. The vessel is then left to stand at ambient temperature (about 24 ° C.) or heated as described in the table below, and the pressure drop measured over 10 minutes for each condition. The result is:

TABLE 2

¹ High loss due to high vapor pressure.

² Occurred in the presence of oxygen.

³ Solvents and caustics used in US Pat. No. 4,366,134.

⁴ diethylenetriamine

Example 3

/분으로 컬럼하부에 공급한다. 액체흐름은 상부에서 약 10cc/분이다. 개스 공급 및 방출에 대한 분석자료를 수득하고 흡수된 CO₂및/또는 SO₂(중량%)를 계산한다. 이 결과는 하기에 기술되어 있다.Various compounds are tested for CO ₂ and SO ₂ absorption properties using the 100,000 Aldershaw column described above. Synthetic N ₂ / CO ₂ / SO ₂ gas mixture of the composition described in the table below at 4 ° C.

Feed to column bottom in / min. The liquid flow is about 10 cc / min at the top. Analytical data on gas feed and discharge are obtained and the absorbed CO ₂ and / or SO ₂ (% by weight) is calculated. This result is described below.

TABLE 3

TABLE 4

This operation demonstrates that NNDP will absorb more than one mole of SO ₂ per mole of NNDP.

TABLE 5

TABLE 6

These two operations demonstrate that at 2% as well as 5% concentrations, SO ₂ will be absorbed more selectively than CO ₂ at temperatures above 50 ° C., at normal water / gas wash temperatures.

Example 4

In another series of test operations, 10% by weight of an aqueous solution of 1-methyl-2-morpholinone in deionized water was charged at 1/2 "x 2 ft (1.27 cm x 0.61 m) at a nominal rate of -5 cc / min. ) supplies, while N ₂ 3.17ℓ / min, air 1.2t / min, CO ₂ 750cc / min and a mixture of SO ₂ SO 70cc / min representing a _21% by weight passing a filling absorber column in the column bottom. column The liquid recovered from the bottom is fed to a 1/2 "x 2 ft (1.27 cm x 0.61 m) ss stripper column filled with 1/4" (0.6 cm) burr saddle equipped with a heated tub reboiler.

The gas released from the absorption tower contains 0.45% by weight SO ₂ and the absorption tower liquid contains 0.63% by weight SO ₂ and 96.8% is removed from the absorber in the stripper column. This shows a yield of 1/2 mole per 1 mole of 1-methyl-2-morpholinone: 10% solution, and the ability to regenerate the absorbent material for recycling.

Claims (9)

Contacting a gas stream containing sulfur dioxide and carbon dioxide with an aqueous solution of the compound of general formula (I) to selectively remove sulfur dioxide from the gas stream.

Wherein X is an oxygen atom or NR ', wherein R' is a hydrogen atom or C ₁ -C ₅ alkyl; R is a hydrogen atom or C ₁ -C ₅ alkyl. The method of claim 1 wherein X is oxygen. The method of claim 1, wherein X is NR ′. 4. The method of claim 3, wherein R and R 'are both C ₁ -C ₅ alkyl. The process according to claim 1 or 4, wherein the compound of general formula (I) is 1,4-dimethylpiperazinone. The method of claim 1, wherein the compound of formula (I) is 1-methyl-2-morpholinone. The method of claim 1 wherein the process is carried out continuously. 8. The method of claim 1 or 7, further comprising regenerating the aqueous solution of the compound of formula (I). 8. The method of claim 1 or 7, further comprising recovering the gas containing little sulfur dioxide from the aqueous solution.

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