JPH03164419A - Treatment of gaseous carbon dioxide - Google Patents

Abstract

PURPOSE:To reduce the amt. of gaseous carbon dioxide to be discharged into the atmosphere by mixing the carbon dioxide concentrated and separated from a waste combustion gas with seawater to form the clathrate hydrate at low temp. under pressure and discarding the hydrate into the sea. CONSTITUTION:The gaseous carbon dioxide concentrated and separated from waste combustion gas, etc., is supplied to a clathrate forming vessel 1 through a compressor 2 and mixed with seawater. The mixture is cooled by a cooler 3 and subjected to a chemical reaction at low temp. under pressure to form a clathrate hydrate including carbon dioxide molecule into crystal of water. The clathrate is a solid having about 1.11 sp. gr. and hardly soluble in water. The clathrate is separated from seawater in a separation vessel 7 and stored in a tank 8. The clathrate is packed in a container 9 and discarded into the ocean or transported to the deep sea bottom under pressure by a force-feed pump 11. The clathrate is retained on the sea bottom stably and semipermanently. Consequently, the amt. of carbon dioxide in waste combustion gas, etc., to be discharged into the atmosphere is reduced, and an increase in the carbon dioxide content of the atmosphere is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for treating carbon dioxide gas, and more particularly to a method for treating carbon dioxide gas in combustion exhaust gas to reduce the amount of carbon dioxide gas discharged into the atmosphere.

[Conventional technology]

Conventionally, carbon dioxide in the exhaust gas generated by the combustion of fossil fuels such as power generation boilers and industrial boilers is released into the atmosphere as is. At present, there is almost no demand for industrial means for reducing the amount (concentration) of carbon dioxide gas.

[Problem to be solved by the invention]

The concentration of carbon dioxide in the atmosphere was 315 ppm in 1960.
1970: 325 ppm, 1
In 1980, it gradually increased to 3359 pm and is now said to be about 350 ppm. The increase in carbon dioxide concentration is thought to be the result of a combination of various factors, including logging, desertification of forests, destruction of coral reefs, and population growth. Since the trends in the concentration increase over time are similar, it is inferred that carbon dioxide emissions from fossil fuel combustion are a major cause of the increase in atmospheric concentration.

The increase in carbon dioxide gas in the atmosphere causes the temperature of the atmosphere to rise and the climate (
This will lead to global warming (on the earth's surface) or the greenhouse effect, which in turn will lead to melting of Antarctic icebergs, rising ocean temperatures, rising sea levels, desertification of forests, food shortages, etc., endangering the future of human life. . If we continue to burn fossil fuels at the current rate and emit carbon dioxide in exhaust gas as is, we can predict that the concentration of carbon dioxide in the atmosphere will definitely increase in the future.

In order to reduce the phenomenon of increase in carbon dioxide gas in the atmosphere, the present invention
The present invention aims to provide a method for separating and recovering all or part of carbon dioxide contained in fossil fuel combustion exhaust gas and fixing it so that it will not be released into the atmosphere again.

[Means to solve the problem]

The present invention is a method for reducing the concentration of carbon dioxide emitted into the atmosphere, such as combustion exhaust gas, by mixing concentrated and separated carbon dioxide with seawater, and creating carbon dioxide molecules in water crystals through a chemical reaction at low temperatures and under pressure. This is a method for processing carbon dioxide gas, which is characterized in that it produces a permanent slate of carbon dioxide, and transports it to the deep sea under pressure, or seals it in a container and dumps it into the ocean.

In order to reduce the concentration of carbon dioxide in the atmosphere, we focused on fossil fuel combustion exhaust gas, which is the main source of carbon dioxide emissions, and diverted all or part of the gas that was traditionally released into the atmosphere from chimneys to a separate system. Only carbon dioxide gas is separated and removed, and the exhaust gas from which carbon dioxide gas has been removed is released back into the atmosphere as purified gas. The technical means to separate and remove carbon dioxide gas is to first remove carbon dioxide gas from exhaust gas by using adsorbents such as zeolites (selective adsorption and desorption operations of carbon dioxide gas) or by chemical absorption (absorption by 2-alkoxyamines) and dissipation operations. (concentration about 10%) is separated as a high concentration gas of 90% or more.

The purpose of the present invention is to process this highly concentrated gas, by mixing this gas with seawater at a low temperature below 10°C, and applying pressure corresponding to the temperature to cause the carbon dioxide gas and seawater to react, thereby hydrating the solid. It is to bring something to life. If this is separated and collected and thrown into the deep seabed (approximately 500 meters deep), this solid permanent product will not decompose in the deep seabed environment, so carbon dioxide will not be released into the atmosphere again, and therefore it will be released from the combustion exhaust gas into the atmosphere. It becomes possible to reduce the amount of carbon dioxide gas released.

[Effect]

It is possible to concentrate, separate and recover carbon dioxide in combustion exhaust gas through operations such as adsorption and desorption using existing technology, but it is possible to mix this with seawater and react under low temperature and pressurized conditions to release carbon dioxide. Since a feature of the present invention is to form a solidified body as a hydrate, this principle will be explained below.

Carbon dioxide exists in water as a gas, liquid, or solid, and this state is determined by temperature and pressure. Figure 3 (vertical axis is logarithmic scale of pressure, horizontal axis is temperature) shows CD. -L
The shaded area in the temperature range of 0 to 10°C shows the phase equilibrium state of the O system (12.4 to 35 atm. at 0°C,
At 10° C., 4 4 atm), CD, and 8.0, the following reaction produces talus slate hydrate.

It has a crystalline structure in which carbon molecules are embedded in a water crystal (a three-dimensional framework of 14 or 16 hexahedrons), and it is a solid that is difficult to dissolve in water. This Taraslate has a specific gravity of about 1.11 and is heavier than water, so it precipitates in water and can therefore be recovered from water using a solid-liquid separation process. Furthermore, since the temperature and pressure on the deep seabed are such that the Taraslate is stable, it is possible to directly insert it into the deep seabed, where it will remain semi-permanently without surfacing.

〔Example〕

An embodiment of the present invention is shown in FIGS. 1 and 2.

FIG. 1 shows the equipment structure of the COi gas slate solidification system, which is the key point of the present invention.

The concentrated i1C-ro2 gas is compressed by a compressor 2 and sent to the Taraslate tank 1 together with seawater. In the Taraslate generation tank 1, a mixture of carbon gas, water, and water is cooled to a predetermined temperature by a cooler 3, and the temperature and pressure are set while monitoring a pressure gauge 4 and a thermometer 5.

Next, the pump 6 sends the raw Taraslate to the Taraslate separation tank 7 for solid-liquid separation. The clathrate is held in a clathrate storage tank 8, and the seawater separated in the clathrate separation tank 7 is returned to the clathrate generation tank 1 for circulation use. In this way, once solid-liquid separation is performed and the cooled seawater is recycled and used, it is energy efficient. The held Taraslate is sealed in a container 9, transported by a dumping ship 10, and thrown into the deep seabed of the ocean, or directly into the deep seabed with a 1-liter pressure pump. The pressure and temperature to be set are in the range where clathrate solidification occurs, and the above-mentioned CO2-H
For example, the shaded area of the 20 series equilibrium diagram is 12. 4
atm or higher, 23 atm or higher at 5℃, 4 atm at 9.9℃
4 atm or more).

Figure 2 shows the flow of the overall treatment system of the present invention, which aims to reduce CO in combustion exhaust gas.
Conventionally, for exhaust gas containing CO2 gas emitted from
The entire amount or a portion of the gas discharged from the chimney 22 is guided to the pretreatment device 23, where the temperature of the exhaust gas is lowered,
After removing unburned carbon etc., CO, separation equipment? 4, only the CD2 gas is concentrated and separated, while the CO2 gas from which it has been removed is released into the atmosphere as purified gas.

The concentrated CD and gas are compressed by the compressor 2 and mixed with seawater as described above to produce solidified Taraslate in the Taraslate production tank 1.

This is either sealed in a container or placed into the deep sea by means of pressure transport.

In this way, the present invention can reduce CO2 in combustion exhaust gas such as fossil fuels.
In order to reduce the amount of gas released into the atmosphere, the CO gas in the exhaust gas is made into a highly concentrated CO gas using existing technology, and then a crystal body is created as a solidified Taraslate, and the CO gas is mixed into the water crystals. This project proposes a method to firmly confine CO2 and release it into the deep seabed.

〔Effect of the invention〕

According to the present invention, colloidal slate formation of CO and gas requires a relatively high temperature (0 to l
Furthermore, since the pressure to be applied may be less than 45 atm, the required power is small, which is industrially advantageous. In addition, the present invention is a system that can reduce the volume of CO2 gas by incorporating CO gas into water crystals and solidify it, and furthermore, can continuously process the solidification of CD2 slate.

As described above, the present invention, in which CO2 gas is mixed with water and recovered as a solidified Taraslate by low-temperature pressurization and then injected into the deep sea floor, reduces carbon dioxide gas in the combustion exhaust gas released into the atmosphere, and in turn reduces the amount of carbon dioxide in the atmosphere. This is an effective countermeasure against increasing carbon dioxide concentration or global warming.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram illustrating an embodiment of the present invention, FIG. 2 is a configuration diagram of an embodiment in which the present invention is applied to treatment of combustion exhaust gas,
Figure 3 shows CD. It is a phase equilibrium phase diagram of -0.0 system.

Claims (1)

[Claims] A class of methods for reducing the concentration of carbon dioxide emitted into the atmosphere, such as combustion exhaust gas, in which concentrated and separated carbon dioxide is mixed with seawater and carbon dioxide molecules are incorporated into water crystals through a chemical reaction at low temperatures and under pressure. A method for processing carbon dioxide gas, which is characterized by producing a rate hydrate and transporting it under pressure to the deep seabed or sealing it in a container and dumping it into the ocean.