SU1296202A1 - Method of regeneration of absorbent - Google Patents

Abstract

The invention relates to methods for absorbent regeneration in gas purification processes for COj with an aqueous solution of monoethanolamine used in the chemical, metallurgical and food industries and allowing energy consumption to be reduced. The flow of regenerable absorbent is divided into parts and sent to them in several shell-and-tube heat exchangers (TO) in parallel streams with heating of one of them with heating steam. The vapor-gas mixture formed in the pipes of each TO is fed into the annular space of the subsequent TO. At the same time, the temperature and pressure vary stepwise from not more than 0.5 MPa in TO with heating steam to at least 70 ° C and 0.05 tffla in the latter along the vapor-gas mixture TO. The condensate formed in the annular space of each TO (except the first) is fed to the lower part of the pipe space of the same TO. 1 l. f-ly, 2 ill. with (L with: tsd; o O) Is5

Description

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The invention relates to methods for absorbent regeneration in the absorption of gases from CO, and can be used in the chemical, petrochemical, metallurgical, food and other industries.

The purpose of the invention is to reduce energy consumption.

 FIG. 1 and 2 are diagrams explaining the proposed method.

Example 1 In the installation scheme shown in FIG. 1, the regeneration-directed saturation absorbent is divided into two streams in order to obtain a coarsely regenerated absorbent with a degree of carbonization of 0.3 mol / mol and a finely regenerated absorbent with a degree of carbon

bonization

ot 0.1 5.

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The installation consists of three apparatus with a flowing film, housing 1, 2 and 3, working countercurrently with tone

core-generated absorbent and directly along the heating secondary pair.

In order to obtain a finely regenerated absorbent, it is heat treated in two stages.

In the first stage, the saturated CO absorbent is heated and transferred to the housing 3, where it is subjected to heat treatment at and at a pressure of 1 AT. The vapor-gas mixture is withdrawn to the condenser 4, where it is separated into water and COj. The coarsely regenerated absorbent obtained (o1 0.3 mol / mol) from the housing 3 is pumped into the installation housing 1, in which the absorbent is heat treated at 130 ° C and pressure 0 , 25 1УША, Case 1 is heated by an acute heating steam pressure of 0.5 Sha. From the first case, the heat-regenerated absorbent (0.1 mol / mol) with a pump 5 is sent to a heat exchanger 6, in which the absorbent is cooled and fed to the absorption.

The second stream of grades 50, the intensity of the process, the easy-to-control carbon absorbent is thermally processed in one stage in the second body of the plant. The saturated absorbent is preheated in the heat exchanger 7 and fed to the body 2, which is heated by a vapor mixture obtained in the first building body. The heat treatment temperature of the absorbent is 110 ° C, the pressure is 0.15 MPa, Gru-,

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The recovered absorbent from the housing 2 is fed to the heat exchanger 7, cooled and sent to the absorption.

The gas-vapor mixture from the second building is directed to the heating of the third building of the installation.

Each installation frame is a shell-and-tube heat exchanger, in which a gravitational film flowing down along the heating tubes is arranged with the help of distribution devices. The resulting gas-vapor mixture moves upward counter-current to the flowing liquid film. In this case, as a result of the contact between the steam and the liquid, intense heat and mass transfer occurs between the saturated liquid film with a low boiling point and the gas-vapor mixture having a higher temperature.

As it drains down as the degree of carbonization decreases, the temperature of the liquid film and the vapor-gas mixture formed increases. The rising vapor gas mixture is in contact with the flowing film and is cooled.

When contacting vapor and liquid, high concentration and temperature gradients arise in countercurrent, which contributes to an increase in the intensity of the process and the efficiency of regeneration.

Thus, in the proposed method, the energy of the flow is reused during heat exchange through the wall between the liquid absorbent and the vapor-gas mixture from the preceding installation body.

Repeated use of heat significantly reduces the energy costs of regenerating the absorbent. The counter-movement of the heat carrier (vapor-gas mixture) and the regenerable absorbent both inside the heating tubes of the film apparatus and between the buildings of the installation allows to increase

l process and obtain any desired degree of regeneration of the absorbent.

A preliminary calculation shows that an installation for regenerating a saturated solution of monoethanolamine (MEA) is required for the production of ammonia with a capacity of 1360 tons / day. When regenerating in a 3-box installation, receive

550 finely regenerated absorbent with a degree of carbonization of 0.1 mol / mol and 550 coarsely regenerated absorbent with a degree of carbonization of about 0.3 mol / mol. In the process of regeneration, it is necessary to evaporate 32 t / h of water and remove 68 t / h of CO from a saturated solution of MEA. For carrying out this process, 3 evaporators with a flowing film with a heating surface F 630 m are used. (Diameter of shell 1800mm, height of heating pipes 5000 mm). The connection of the evaporators is carried out according to the counter-current scheme (Fig. 1).

The advantage of the proposed method is a clear organization of flows in the order of successive changes in pressure and temperature, which makes it possible to obtain almost any degree of regeneration of the absorbent, ease of process control, and substantial energy savings.

The vapor – gas mixture is condensed in the annular space of shells 2 and 3. Water vapor condensate is discharged from the bottom of the heating chambers and mixed with the regenerated absorbent in the same installation case. At the same time, additional heat condensate is used, increase the degree of regeneration of the absorbent and reduce the amount of heat.

Consumption of heating steam is 199.6 thousand Kcal / ton of CO.

PRI mme R 2. The method can be; It is used according to the scheme shown in figure 2, which provides finely regenerated carbonation with ot 0.1 mol / mol and coarsely regenerated with, 3 mol / mol

. In the third case of the installation, the desorption process is carried out at a pressure of 0.21 MPa and. Resulting

steam, and the carbon dioxide released.

The installation consists of seven subsequent -45 vapor-gas mixture is fed to the heating of the rubbed housing, which is interconnected in a second way, in an intertube rich couple of film apparatus (the corpuscles are condensed with water).

Coarsely regenerated absorbent is obtained by one-step heat treatment. In order to obtain a finely regenerated absorbent, the coarsely regenerated absorbent of the subgenus is removed from the upper part of the heating chamber.

In the fourth case, the process of carbon dioxide desorption is carried out at a pressure of 0.14 MPa and YuU C. The resulting gas-vapor mixture is inhibited by additional heat treatment. The original carbon dioxide-saturated monoethanolamine solution with a degree of carbonization, 65 mol / mol, is divided into five streams and is directed in parallel to five shells

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novki (buildings 3-7) for the first stage of regeneration.

The coarsely regenerated absorbent obtained from the latter cases is directed to the second regeneration stage in countercurrent with respect to the secondary ones in the heating pair. For the second stage of regeneration, the first and second buildings of the plant are used, to which coarsely regenerated absorbent is directed by pumps 9.

From the 7-7GO body, the coarsely regenerated absorbent is fed to the first body, -a from the 6th to the second building body.

The heating of the first building of the installation was done by heating steam with a pressure of 0.6 MPa (possibly 0.8 MPa). In the first installation case, the process of desorbing carbon dioxide is carried out at; pressure of 0.5 MPa and temperature.

From the first casing, the resulting vapor-gas mixture is fed into the annular space of the second casing, where water vapor condenses. Carbon dioxide is separated and removed from the upper part of the annular space of the heating chamber. In the tube space of the heating chamber of the second body, the process of desorption of carbon dioxide from a solution of monoethanolamine is carried out at a pressure of 0.35 MPa and a temperature of 129 ° C.

The vapor-gas mixture formed in the second case is fed to the heating of the third case of the installation. In the annular space of the heating chamber of the third building, water vapor condensation is produced, carbon dioxide is separated and removed. I

. In the third casing of the installation, the desorption process is carried out at a pressure of 0.21 MPa and. Resulting

steam, and the carbon-gas mixture present in the separated dioxide is fed to the heating of the scrubbed body, water is condensed in the annular space

sort of withdrawn from the top of the heating chamber.

In the fourth case, the process of desorption of carbon dioxide is carried out at a pressure of 0.14 MPa and YuU C. The resulting gas-vapor mixture is fed into the annular space of the fifth body of the installation, where water vapor condenses and the separated carbon dioxide is removed from the upper part of the chamber.

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In the fifth casing, the process of desorbing carbon dioxide is carried out at a pressure of 0.09 MPa and 95 ° C. The vapor-gas mixture formed in the fifth case is fed to the heating of the sixth case. In the sixth case, the process of desorption of carbon dioxide is carried out at a pressure of 0.06 MPa and. The resulting vapor-gas mixture is directed to the heating of the seventh housing.

In the seventh package, the carbon dioxide desorption process is carried out at a pressure of 0.05 MPa and 70 ° C. The vapor-gas mixture formed in the seventh housing is directed to the condenser 10, where the water vapor is condensed and the liberated carbon dioxide is removed.

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The coarsely regenerated absorbent streams from housings 3, 4 and 5, after being cooled in heat exchangers 8, are connected to a common stream and sent to absorption. The fine-regenerated absorbent streams are cooled in heat exchangers 8, then connected and sent to absorption.

The specific heat consumption per 1 ton of CO is 99 thousand kcal / t CO,

Claims (2)

Claim 1. Absorbent regeneration method at elevated temperature in carbon dioxide gas purification processes with an aqueous solution of monoethanolamine, which includes passing the absorbent through a system of several shell-and-tube heat exchangers with heating of one of them with heating steam and feeding the vapor-gas mixture formed in the tubes of each heat exchanger Into the annular space of the subsequent heat exchanger with the selection of gaseous carbon dioxide, about 1 and 5, because, in order to reduce energy costs, the flow of The non-absorbable absorbent is divided into parts and sent to the heat exchangers in parallel streams, while the pressure and temperature change in the heat exchangers in steps from not more than 140 ° C and 0.5 MPa in the heat exchanger with heating steam to not less than 70 ° C and 0.05 MPa in the last heat exchanger along the vapor-gas mixture. 2. The method according to claim 1, which differs from the fact that the condensate formed in the intertube space of each heat exchanger, except for the first one, is supplied to the lower part of the tube space of the same heat exchanger, coz C02 7 Compiled by G.Vinokurova Editor M.Dishsh Tehred A.Kravchuk. ZakaGbZOLo Circulation VNIIPI State Committee CbLF for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 Production Printing company, Uzhgorod, Projecto st., 4 .Z