JPH06510481A - Method and apparatus for regulating the humidity of a gas stream and simultaneously purifying the gas stream of undesirable acidic or alkaline gases - 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 adjusts the humidity of a gas stream and removes from the gas stream, e.g. Concerning a method for purifying potash gas.

According to this method, along the retentive side of the diaphragm through which water vapor diffuses, on the opposite permeable side, a hydroscopic liquid is introduced. flows.

condensing the liquid contained therein from the gas stream by cooling it below its dew point; Methods for removing water vapor are well known.

In order to adjust the humidity of the gas stream to a particularly desired value, the gas is first warmed and then heated at that temperature. It is also possible to saturate the liquid and then cool it to the desired dew point.

Other methods of removing water vapor from gases include hydroscopic media and salts. I have something to use.

A practical and continuously usable method of this type is described in U.S. Pat. No. 4.915.83. It is stated in No. 8. To remove water vapor from the air, a small amount of drying airflow is required. It is guided to the retaining side of the perforated septum. The membrane used is a so-called hollow fiber membrane. be.

Hydroscopic liquid flows to the permeate side of the diaphragm. Water vapor from the gas stream is Diffuses from the retentate side to the permeate side through the pores of the diaphragm, where hydroscopic Absorbed and carried away by liquids.

Methods for regulating the humidity of gases such as air can be used in a wide range of applications, including inside buildings and means of transportation. It can be applied in In particular, these gases can be converted into hydrogen sulfide, sulfur dioxide, nitrogen dioxide, Not only acidic gases such as carbon dioxide and carbon dioxide, but also alkaline gases such as ammonia, etc. It is also important to clean undesirable, e.g. hazardous gas parts, such as gases. be. In terms of removing dangerous gases from the air, industrial areas, subdivisions and roadsides In addition to the case of polluted air in Applications are also being considered inside buildings and to means of transportation, such as to prevent artwork from being damaged by transparent objects. It will be done.

This removal of undesirable parts in the air is done at the same time as the above-mentioned method of adjusting the humidity in the air. It can't happen. For example, assuming those parts have mutually matching dew points, , by cooling the air below the dew point, only the part that can condense can be removed.

If a hydroscopic medium is used, it excludes any gas except water vapor. I can't leave.

The present invention provides for this purpose the adjustment of the humidity of the gas stream and the alkaline, acidic, or to remove undesirable gases from the gas that are absorbed into neutral aqueous solutions. , relates to a method that is carried out simultaneously in one step. The method of the invention comprises: A diaphragm is also used that allows the moisture in the mixture to be disposed of. The desired humidity balance of the gas stream is adjusted and its composition is removed from the gas stream. The solubility of the acidic or alkaline components is adjusted to It is characterized by the fact that droscopic liquid is mixed with water.

The water content of this hydroscopic mixture determines the humidity balance to be adjusted. Set. The diaphragm directs water vapor either from the retention side to the permeation side or vice versa. The water vapor can also be passed through the gas to be removed. It can be added to both gases. This gas permeates from the retaining side of the diaphragm. The acidity of the hydroscopic mixture that diffuses to the permeate side and flows along the permeate side of the diaphragm. Or as a result of being absorbed by alkaline moisture, it is treated at the same time as humidity adjustment. Gas components to be removed are removed from the gas stream. For this, water is removed The solubility of the desired component is increased and/or promoted by physical or chemical action. The composition must be such that the The composition is tailored to the nature of the gas being removed. must be adjusted accordingly. For example, there are strong or weak organic Or an inorganic acid or alkali is dissolved.

Poles like triethylene glycol or polyethylene glycol or mixtures thereof Hydroscopic substances consisting of glycols, alcohols or glycerol Good results are obtained using liquids. It has hydroscopic properties. An electrolytic aqueous solution may also be used. In general, all such hydroscopic mixtures i.e. a hydroscopic liquid with a dissolved part in it is used The choice should be one that is compatible with the diaphragm and module material.

The invention includes a hydroscopic system used to control humidity during the process. Also included is a method of regenerating the mixed liquid until it once again retains the desired moisture content. this method For this purpose, the mixture is first heated or cooled to a certain temperature and then When brought into contact with the flow until equilibrium is reached and cooled or heated to working temperature, It is characterized by saying.

The membrane modules used consist of - or more membranes, which are microporous and is hydrophobic. For example, polypropylene is suitable in this respect. How For that purpose, the diaphragm must have an exchange surface of sufficient size. do not have. The diaphragm may be a hollow fiber, or a flat diaphragm may also be applied. in principle, It makes no difference which side of the diaphragm the gas or liquid is guided to. For example, hollow fiber Diaphragms allow either liquid or gas flow to pass through the fibers. .

Under certain circumstances it may be desirable to use the above membranes with a non-porous top layer. Yes. Such a diaphragm depends on the nature of the hydroscopic mixture and/or may be undesirable through the pores of the microporous membrane as a result of the way the procedure is performed. It is particularly useful when permeation of hydroscopic mixtures occurs. Upper septum For example, PDMS (silicon rubber), polytrimethylsilylpropyne, Alternatively, it consists of a thin gel layer mainly composed of polymers.

Naturally, this upper layer of water vapor and the part to be removed from the gas being treated The permeability must be large enough to ensure effective removal. Must be. Such an upper layer may be hydrophobic or hydrophilic.

When using diaphragms with non-porous top layers, effective material transfer is considered In choosing which side of the diaphragm the liquid or gas flows on, Preferably, the liquid flows over the layer. However, the possible In view of the contamination caused by Sometimes. At this time, dirt accumulates before the upper layer and penetrates into the porous layer of the diaphragm. do not.

The invention also includes an apparatus for carrying out the method described above.

For this purpose, the device combines the water vapor to be removed with e.g. A diaphragm consisting of one or more diaphragms through which both alkaline gases can diffuse The gas flow to be purified and regulated with respect to humidity is passed through the diaphragm. Direct the acidic, alkaline, or neutral hydroscopic mixture to one side. Provide means to lead to the other side.

Therefore, the membrane is microporous, hydrophobic, and has a sufficiently large exchange surface. It is desirable that the A porous top layer may also be provided.

Below, some examples of the method according to the invention are described.

In this description, various aspects of the invention are presented.

Generally, the concentration of acid or alkali in the absorption liquid or the entire mixed liquid is water removed from or added to the air stream being treated, as the case may be; The amount varies depending on the amount.

Example 1 A stream of humid nitrogen gas containing 500 ppm sulfur dioxide is passed through the hollow fiber membrane module. (Type: ENKA) LM2PO6, polypropylene fiber, microporous The flow rate was 4 liters/min through the fibers. The diaphragm module has an inner diameter of 0° It has 6 mm fibers and a total membrane surface area of 400 cm2. The bundle of fibers is , 0.251/min ethylene glycol and sodium carbonate as absorption liquid Surrounded by solution.

The ratio of ethylene glycol and sodium carbonate solution in this mixture is , 4:1. For the incoming nitrogen gas stream, the relative humidity is approximately 94%, with a dew point of 1 2.1°C was measured. The concentration of sulfur dioxide was 500 ppm.

In the exiting nitrogen gas stream, a relative humidity of approximately 61% and a dew point of 12°1°C were measured. Out The concentration of sulfur dioxide in the nitrogen gas stream detected was 0.5 ppm. Ta.

Therefore, while the humidity of the nitrogen gas stream is adjusted or reduced, the nitrogen The sulfur dioxide content of the gas stream appears to have been reduced by 99%.

Example 2 In a diaphragm module similar to Example 1, the dry nitrogen gas stream was The nitrogen content was directed through the fibers at a flow rate of 4 liters/min. around the fibers The absorption liquid is about 80% ethylene glycol and about 20% 1M sodium carbonate. A liquid consisting of lium was injected. The absorption liquid had a flow rate of 0.5 liters/min. Ta. The operating temperature was approximately 28°C.

The relative humidity in the incoming nitrogen gas stream is approximately 10%, and the dew point is.

It was measured as 5.5°C.

In the exiting nitrogen gas stream, the sulfur dioxide concentration is 0.5 ppm and the relative humidity is approximately 41% ( j1 point 14.0°C) was measured.

Therefore, while the humidity of the nitrogen gas stream is adjusted or increased, the nitrogen The amount of sulfur dioxide in the gas stream appears to have been reduced by 99%.

Example 3 With a configuration similar to Examples 1 and 2, the extent of sulfur dioxide removal from the nitrogen gas stream , it was observed what effect the concentration of sodium carbonate had. For this , sodium carbonate solutions range from 1 molar to 0.3 molar and 0°, respectively. Diluted to 1 molar concentration. At 0.3 molar concentration of sodium carbonate, the amount of sulfur dioxide The degree of removal was still above 99%. At 0.1 molar concentration of sodium carbonate It appeared that the extent of SO removal was reduced to about 90%.

Example 4 In an experimental setup similar to Examples 1 and 2, ethylene glycol and (sodium carbonate) from a nitrogen gas stream in the case of a water mixture (containing no water) and in the case of water alone It was observed whether the removal of sulfur dioxide took place. Dioxide leaving nitrogen gas The concentration of sulfur was now reduced to 51.3 ppm. The maximum removal level is 5 It was 0%. For longer experimental times, the extent of removal decreased to less than about 40%.

From the results of Examples 3 and 4, it can be seen that without adding sodium carbonate or with 0.1 molar The extent of sulfur dioxide removal can be reduced by adding sodium carbonate at a concentration below the It can be inferred that it will decline rapidly. In that case, the solution is rapidly saturated with sulfur dioxide condition, which appears to prevent further absorption. Effective sulfur dioxide removal Concentrations of sodium carbonate were added to remove and simultaneously adjust the humidity of the nitrogen gas stream. Since the concentration was 0.1 molar or more, the experimental configuration was the same as in Examples 1 and 2. However, as absorption liquids, triethylene glycol (TEG) and potassium carbonate solution ( The experiment of Example 1 was repeated with the difference that a 1 molar mixture was used. child The ratio of TEG and potassium carbonate solution in the mixture was 4:1 by weight. implementation Similar to Example 1, the degree of dehumidification and, at the same time, the removal of sulfur dioxide was measured.

From this result, as in the case of the mixtures used in Examples 1 to 4, TEG and carbonate Using a mixture of nitrogen gas solutions, the humidity of the nitrogen gas stream is adjusted and at the same time sulfur dioxide It is concluded that the content can be reduced by 99%.

Continuation of front page (51) Int, C1,5 identification symbol Internal reference number B 01 D 53/3 4 119 6953-4DI

Claims (10)

[Claims] 1. along the retentive side of the diaphragm through which water vapor can diffuse A gas stream is directed, while a hydroscopic liquid flows on the opposite permeable side. to adjust the humidity of the gas stream, e.g. acidic or alkaline In the method of purifying gases, such acidic or alkaline gases A diaphragm is used that allows the hydroscopic liquid to diffuse through the mixture. The moisture in the mixture is adjusted to the desired humidity balance of the gas stream to be treated and its composition can be used, for example, to increase the solubility of acidic or alkaline components to be removed. characterized by being mixed with moisture so as to be adjusted to promote how to. 2. Hydroscopic fluids such as triethylene glycol and polyethylene glycol polar glycols, alcohols or glycols such as alcohols or mixtures thereof; The method according to claim 1, characterized in that it consists of cerol. 3. Is the hydroscopic liquid an electrolytic aqueous solution with hydroscopic properties? The method according to claim 1 or 2, characterized in that: 4. While carrying out the method, first heating or cooling to a certain temperature and then A gas stream with constant humidity through a diaphragm permeable to water vapor until equilibrium is reached. and finally by cooling or heating the mixture again to working temperature. , the hydroscopic mixture used is re-treated until the desired water content is reached. 4. A method according to claim 1, characterized in that the method is produced by: 5. The membrane module comprises one or more microporous hydrophobic membranes with a sufficiently large membrane exchange surface. 5. A method according to claims 1 to 4, characterized in that it is used in conjunction with a sexual diaphragm. 6. If the diaphragm absorbs the water vapor to be removed, or e.g. acidic or alkaline Can be used with a non-porous top layer that has a sufficiently high permeability to both gases. The method according to claim 5, characterized in that: 7. Both the water vapor to be removed and the e.g. acidic or alkaline gases It has a diaphragm module consisting of one or more diaphragms that can be diffused and purified. Directing the gas flow to be adjusted with respect to humidity on one side of the membrane, acidic, alkaline A means of directing a potassium or neutral hydroscopic mixture to the other side. Apparatus for carrying out one of the methods according to claims 1 to 6, comprising: 8. The diaphragm is a microporous hollow fiber membrane made of hydrophobic material. 8. The device according to claim 7. 9. The membrane is flat, microporous, and hydrophobic with a sufficiently large membrane exchange surface. 8. Device according to claim 7, characterized in that it is a membrane. 10. The diaphragm is in contact with water vapor such that the method according to claim 6 can be carried out. , with a non-porous upper layer that is permeable to acidic or alkaline gases. 10. A device according to claims 7, 8 and 9, characterized in that the device comprises: