JPH02157012A - Desorption and recovery by heating of material adsorbed in adsorbent - Google Patents

Abstract

PURPOSE:To recover materials adsorbed by an adsorbent in high concentration at high desorption efficiency within a narrow dispersion by bringing an inert heated gas into contact with the adsorbent adsorbing the materials repeatedly, and after heating the adsorbent to a desired temperature, bringing a heated carrier gas into contact with the adsorbent. CONSTITUTION:At first, a heated gas inert to a material adsorbed in an adsorb ent, e.g. air, nitrogen, steam, etc. is brought into contact with the adsorbent repeatedly. The adsorbent is desirably heated to 70-200 deg.C, preferably to 90-150 deg.C. Then, a heated carrier gas is brought into contact with the heated adsorbent to heat, desorb, and recover the adsorbed material. Moreover, a part of the heated carrier gas may be mixed with a heated circulating gas to carry out circulation. An activated carbon, silica gel, etc., in granular shapes are prefer able as the adsorbent.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention involves heating the adsorbent to a desired temperature by bringing the adsorbent into contact with a heated gas, and then heating the substance adsorbed on the adsorbent. This relates to a method of desorption and recovery.

[Prior art] A method for thermally desorbing and recovering substances adsorbed on an adsorbent is to indirectly heat the adsorbent in a packed column to raise its temperature from outside the packed column, and then bring a heated carrier gas into contact with the adsorbent. There are known methods for desorption and recovery by bringing the carrier gas into contact with an adsorbent, or methods for desorption and recovery by bringing a carrier gas at a higher temperature than a normal heated carrier gas into contact with an adsorbent.

[Problems to be Solved by the Invention] In the method of indirectly heating the adsorbent from outside the packed tower, a temperature distribution occurs between the adsorbents in the packed tower, resulting in variations in the desorption rate and Material recovery efficiency decreases. In order to minimize this variation in the desorption rate, it is necessary to make the device complicated, resulting in huge equipment costs and complicated operations. It is difficult to reduce the amount to a satisfactory level.

On the other hand, in the method using a high-temperature carrier gas, the substance to be desorbed and recovered may decompose in the adsorbent layer near the carrier gas inlet in the packed tower, or the substance to be desorbed and recovered may decompose in the adsorbent layer near the carrier gas outlet in the packed tower. Since the temperature is not raised sufficiently, it has drawbacks such as poor desorption rate.

[Means for Solving the Problems] The present invention has been made to solve the above-mentioned drawbacks, and has a high desorption efficiency of substances adsorbed to an adsorbent, and also recovers the desorbed substances at a high concentration. This provides a method that allows you to do so. That is, the present invention provides a method for thermally desorbing and recovering an adsorbed substance by bringing a heated carrier gas into contact with an adsorbent on which a substance has been adsorbed. The present invention relates to a method for thermally desorbing and recovering a substance adsorbed on an adsorbent, characterized in that the adsorbent is repeatedly brought into contact with the adsorbent in advance to raise the temperature of the adsorbent to a desired temperature.

The method of the present invention will be specifically explained below with reference to FIG. 1, which is an example of a typical flow sheet for implementing the method of the present invention.

The packed tower a is filled with an adsorbent, and the substance to be adsorbed and recovered is adsorbed thereon.

Since the adsorption operation is normally performed at room temperature, the temperature of this adsorbent is around room temperature. In order to desorb the substance adsorbed on the adsorbent, it is necessary to raise the temperature of the adsorbent, but in the present invention, this temperature raising operation is repeated by repeatedly applying a heated gas that is inert to the adsorbed substance. This is done by bringing them into contact.

As mentioned above, a preferred method of repeatedly contacting heated gas is as follows in the flow sheet in FIG.
In this method, the carrier gas population valve and the recovered gas outlet valve C are closed to circulate the gas that connects the packed tower a, the circulation fan d, the circulation valve e, the heater f, and the packed tower a. The heating gas that is inert to the adsorbed substance is preferably air, and may also be nitrogen gas, water vapor, or the like.

Although it can be changed as appropriate depending on the type of adsorbent and the type of adsorbed substance to be desorbed and recovered, the adsorbent is approximately 70 to 20
It is appropriate to raise the temperature to 0°C, preferably 90 to 150'C.

Most of the circulating gas that is inert to the adsorbed substance is the raw material gas that remains after the adsorption operation, but as the temperature increases as it is heated by heater f, desorption and recovery are added to this circulating gas. This results in the intake of many substances. This heated circulating gas is obtained by circulating the heater f and the packed tower a using a circulation fan d, but in order to proceed with partial desorption in advance and increase the desorption efficiency, a heated carrier is added to this heated circulating gas. It is also effective to mix some gas and perform a circulation operation.

After the adsorbent reaches the desired temperature, close the circulation valve e, stop the circulation fan d, open the carrier gas inlet valve and open the recovered gas outlet valve C, and heat the carrier gas with the heater f. Alternatively, the heated circulating gas containing the substance to be desorbed and recovered, which was held in the packed column before the introduction of the preheated carrier gas, is forced out as recovered gas. Subsequently, the carrier gas desorbs the substance to be desorbed and recovered that remains in the adsorbent and incorporates it into the carrier gas to become a recovered gas.

The introduction flow rate of the carrier gas during the recovery operation may be selected so that the diffusion rate of the substance to be desorbed and recovered into the carrier gas is high. It is possible to obtain recovered gas containing

The recovered gas is used as it is when the purpose is to concentrate the substance to be desorbed and recovered, and is subjected to a condensation separation operation when the purpose is to separate and use the substance to be desorbed and recovered. Note that the desorption and recovery operation may be performed under reduced pressure.

The adsorbent used in the present invention is not limited in any way, but may be selected from activated carbon, silica gel, molecular sieve, zeolite, etc., or composites thereof (in various forms such as granular, fibrous, etc.). The method of the present invention not only enables thermal desorption recovery of a single gas, but also thermal desorption recovery of only a specific component in a mixed gas by using a selective adsorbent.

According to the present invention, the gas to be recovered is not limited in any way as long as it can be adsorbed and desorbed by various adsorbents, such as ammonia, hydrogen sulfide, sulfur dioxide gas, various hydrocarbon gases, trichlorethylene, perchlorethylene,
Chlorine compounds such as methylene chloride and methyl chloroform,
Chlorinated fluorinated compounds such as trichlorofluoromethane, dichlorodifluoromethane, chlorodifluoromethane, tetrachloro-1,2-difluoroethane, 1.1.2-trichlorotrifluoroethane, 1.2-dichlorotetrafluoroethane, etc. be able to.

[Example] Example 1 Using the apparatus shown in FIG. 1, thermal desorption recovery of a substance adsorbed on an adsorbent was carried out. First, an adsorption operation was performed using only packed column a. 1,1゜2-trichlorotrifluoroethane (hereinafter referred to as R-113) gas concentration 0.1v
Packed tower a filled with activated carbon using o1% air as an adsorbent
from the bottom to the top, R-113 in the outlet gas from the top
It was flowed until 4 degrees became 0.05vo1%. After that, a packed column a is installed so that the flow is as shown in Figure 1,
A thermal desorption operation was performed. Circulation fan d - circulation valve e - heater f - packed tower a - circulation fan d is operated,
Electrical heating was carried out so that the outlet temperature of the heater was 140°C. After about 10 minutes, the gas temperature at the outlet of packed column a became about 135° C., and the R-113 concentration became about 5.6 vol%. Next, after stopping the circulation valve e and the circulation fan d, open the carrier gas inlet valve and the recovered gas outlet valve C, and let the carrier gas at 140℃ flow.
A recovered gas of o1% was obtained. No degradation of R-113 occurred.

Liquefaction recovery rate of R-113 (amount of R-113 liquefied and recovered x
100%/amount of R-113 adsorbed on activated carbon) is 7
It was 5%.

Comparative Example 1 The same procedure as Example 1 was carried out except that the circulation operation was not performed and a carrier gas at 500°C was flowed, and the R-113 concentration was 1.
A recovered gas of 5 to 0.1 vol% was obtained, but some decomposition products of R-113 were observed. Moreover, the liquefaction recovery rate was 12%.

[Effects of the Invention] Since the method of the present invention has a high desorption efficiency of substances adsorbed on an adsorbent, it is possible to recover the desorbed substances at a high concentration. Since the temperature of the adsorbent is raised by bringing it into direct contact with the heated circulating gas in the system, the temperature rise efficiency is high, temperature distribution between the adsorbents is less likely to occur, and there is little variation in the desorption rate, resulting in high recovery efficiency ( can do.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of a typical flow sheet for carrying out the method of the present invention. a: Packed tower d: Circulation fan f: Heating carrier carrier

Claims (1)

[Claims] 1. In a method of thermally desorbing and recovering the adsorbed substance by bringing a heated carrier gas into contact with the adsorbent on which the substance has been adsorbed, an inert heated gas is applied to the adsorbed substance in advance before thermally desorbing and recovering the adsorbed substance. A method for thermally desorbing and recovering substances adsorbed on an adsorbent, the method comprising repeatedly bringing the adsorbent into contact with the adsorbent to raise the temperature to a desired temperature.