JPS60172331A - Recovering method of mechanical power - Google Patents

Abstract

PURPOSE:To recover mechanical power in a wet absorption process of gaseous CO2 by introducing a gaseous mixture discharged from a regeneration tower to an expansion turbine and cooling the mixture to separate the moisture. CONSTITUTION:A gaseous mixture consisting of carbon dioxide and water vapor discharged from a regeneration tower R is introduced to a turbine T and the mixture is once expanded up to the atmosphere or less to generate mechanical power. After recovering the mechanical power, the gaseous mixture is cooled by a cooler CL1 and the water contained therein is separated by a separator D1. Thereafter, it is discharged to the outside of the system from a pipe 6 and disposed or recovered to utilize it. When an inexpensive heat source exists, gaseous mixture consisting of carbon dioxide and water vapor can be preheated by the heat source before the mixture is entered the turbine. The effect of less energy consupmtion is increased by the recovery of mechanical power.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to energy saving in a novel carbon dioxide absorption process, and in particular, in a process of absorbing carbon dioxide in gas using a carbon dioxide absorption solution, the present invention relates to the regeneration of the carbon dioxide absorption solution. The carbon dioxide/steam mixture gas coming out of the top of the tower is either preheated or directly introduced into an expansion turbine to generate power, and then cooled and water is separated, or after the water is separated, the reduced pressure carbon dioxide/steam mixture gas is produced. This is a power recovery method in which a part of the generated power is used to recompress the fuel, and if desired, it is cooled and water is separated.

Conventionally, when reformed gas with a composition obtained by reforming natural gas, naphtha, etc. is used as a raw material for ammonia synthesis, for example, due to inconveniences in synthesis or from the aspect of effective use of by-products, Carbon dioxide gas is usually absorbed and removed and recovered by a method using a carbon dioxide absorption solution.

In the conventional process of absorbing carbon dioxide in gas using an absorption liquid such as a potassium carbonate solution, regeneration of the solution is carried out near atmospheric pressure and at a temperature of about 100°C from the viewpoint of regeneration rate and subsequent cooling. The carbon dioxide/steam coming out of the regeneration tower is cooled, and the entrained water is separated and sent out of the system.

The present inventors conducted a meter reading regarding the improvement of the above process,
As a result of focusing on the moisture in the mixed gas of carbon dioxide gas / water vapor coming out of the regeneration tower, it was noticed that the mixed gas has a cooling water content Mu11t, which is a fraction of the number of moles immediately after leaving the regeneration tower, The present invention has now been completed.

The present invention will be explained below.

In the present invention, first, the carbon dioxide/steam mixture gas discharged from the regeneration tower is introduced into an expansion turbine, where it is once expanded to atmospheric pressure or below atmospheric pressure to generate power.

The mixed gas is then cooled and water separated.

The gas, which is mainly composed of carbon dioxide gas after water separation, is heated to the generated gas again up to the required pressure, depending on the pressure after expansion in the expansion turbine and the method of using the gas (disposal or reuse). Part of the power is used to increase the pressure (atmospheric pressure or natural pressure at the raw material gas introduction part).

A specific example will be described below with reference to the drawings.

Fig. 1 is a flowchart showing the power recovery method of the present invention, and Fig. 2 is an improvement on the method shown in Fig. 1, which further includes a compressor and a cooling/moisture-recovering device. .

FIG. 3 shows the conventional method.

In Fig. 3, the reformed gas reformed in the ref A-mer etc. is recovered as necessary at the bottom of the regeneration tower R, cooled and water separated, and then transferred to the absorption tower A through the pipe 21. will be introduced in The reformed gas from which carbon dioxide has been absorbed in the absorption tower A is passed through the pipe 22.
It is sent outside the system as raw material gas for ammonia and other manufacturing plants. The absorption liquid that has absorbed carbon dioxide gas from absorption tower A is introduced into regeneration tower R through hydration turbine H, where it is flushed, etc., to discharge carbon dioxide gas, and is regenerated. is circulated. The insufficient water groups are replenished from the top of the regeneration tower R, etc.

The mixed gas of carbon dioxide/steam from the regeneration tower R passes through a pipe 3, is cooled by a cooler CL, and after separating water in a separator, is discharged from the system through a pipe 5, and is disposed of or recycled. .

As described above, in the conventional method, recovery of power from the gas from the regeneration tower is not normally performed.

On the other hand, in the case of Fig. 1, the carbon dioxide gas/steam mixture gas from the regeneration tower R is introduced into the turbine T, where it generates power, and then cooled with the cooler CLI, and then into the separator D1. After the water is separated, it is discharged from the system through a tube 6 and is disposed of or recycled. Also, in the case of Figure 2,
The mixed gas of carbon dioxide/steam from the pipe 6 is sent to the turbine T.
After being introduced into the compressor C driven by a part of the power of the
After the water is separated in step 2, it is discharged from the system through pipe 6 and is disposed of or recycled.

Although the method of the present invention has been explained above using a flow diagram, the method of the present invention is not limited to this diagram. It is possible to preheat a mixed gas of water vapor.

The method of the present invention as described above makes it possible to recover power in a system in which power was not recovered conventionally, and is highly effective in saving energy.

Example of Study The method of the present invention was carried out according to the flow shown in Fig. 2, and the results of the study on the case where the carbon dioxide component in the mixed gas of carbon dioxide/steam from the regeneration tower was 16.250 N n (/H) were as follows. Shown in the table.

For comparison, Table 2 shows the heat and material balance of the conventional method (the case shown in FIG. 3) when the amount of carbon dioxide gas/steam mixture gas etc. from the regeneration tower is the same.

Comparing the results in Tables 1 and 2, it can be seen that when the pressure and temperature of the carbon dioxide/steam mixture gas exhausted to the outside of the system are the same, the recovered power is approximately 750 -. .

As an example, in the case of a production equipment with a production capacity of 1000 T/D for ammonia from natural gas, naphtha, etc., the generated carbon dioxide gas is usually about 28.00 ONnr/I+, and the recovery power is about 1.300 T/D.

The efficiency of the turbine and compressor is 0.8, the enthalpy (■) and entropy (S) are 0°C, Iata
(+120 is liquid) was used as the standard.

Table 1 Table 2 11EO6, 1EO4, 1EO3 Others are (x+oI'
+x+o', x+n etc.

[Brief explanation of drawings]

1 and 2 are flow diagrams showing the flow of the present invention, and FIG. 3 is a flow diagram showing the flow of the conventional method. The symbols in the diagram are respectively: A: Absorption tower R: Regeneration tower P: Bomb H: Hydraulic turbine M: Drive machine T: Turbine
C: Compressor L: Load CLSCLI, Cl3: Cooler, Di, D2: Separator 1-12.21.22: Shows the tube. Patent applicant Mitsubishi Gas Chemical Co., Ltd. Representative Nagano Japanese calligraphy funeral, 1 curtain, 3 incasses

Claims (1)

[Scope of Claims] In a process for absorbing carbon dioxide in gas using a carbon dioxide absorption solution, the carbon dioxide/steam mixture gas discharged from the top of the regeneration tower of the carbon dioxide absorption solution is preheated or directly guided to an expansion turbine. After the input power is generated, the water is separated by cooling, or after the water is separated, the reduced pressure carbon dioxide/steam mixture gas is compressed again using a part of the generated power and cooled if desired. Method for recovering power by separating water