CN102706102B - System and method for purifying carbon dioxide in flue gas - Google Patents

Abstract

A carbon dioxide purification system in flue gas, used for separating and purifying carbon dioxide in flue gas containing carbon dioxide, including a flue gas compression device, an air refrigeration device, a heat exchange device, and a gas-liquid separation device. The flue gas compression device is used for The flue gas is pressurized to form high-pressure flue gas. The air cooling device is used to cool the air to form low-temperature air. The heat exchange device communicates with the flue gas compression device and the air refrigeration device. The heat exchange device uses To exchange heat between the high-pressure flue gas and the low-temperature air to form high-pressure low-temperature flue gas, so that part of the carbon dioxide in the high-pressure low-temperature flue gas is liquefied, and the gas-liquid separation device is used to separate the high-pressure low-temperature flue gas liquefied carbon dioxide. The above carbon dioxide purification system in flue gas is relatively simple. The invention also provides a method for purifying carbon dioxide in flue gas.

Description

Carbon dioxide purification system in flue gas and method for purifying carbon dioxide in flue gas

technical field

The invention relates to a system for purifying carbon dioxide in flue gas and a method for purifying carbon dioxide in flue gas.

Background technique

As the basic energy of our country, coal has an irreplaceable status for a long period of time. The flue gas of thermal power plants that use coal to generate electricity contains a large amount of carbon dioxide, which will pollute the environment.

In the existing carbon dioxide purification process in flue gas, the flue gas is usually subjected to solution adsorption and enrichment first, then the solution is heated to evaporate carbon dioxide, and the liquefied carbon dioxide is collected for reuse. However, pretreatment of the flue gas is required to prevent other dust and impurities in the flue gas from contaminating the solution during solution adsorption and enrichment of the flue gas, which makes the carbon dioxide purification process more complicated and is not conducive to the promotion of carbon capture technology.

Contents of the invention

Based on this, it is necessary to provide a relatively simple system for purifying carbon dioxide in flue gas and a method for purifying carbon dioxide in flue gas.

A system for purifying carbon dioxide in flue gas, used for separating and purifying carbon dioxide in flue gas containing carbon dioxide, the system for purifying carbon dioxide in flue gas includes:

The flue gas compression device is used to pressurize the flue gas to form high-pressure flue gas;

Air cooling unit for cooling air to form low temperature air;

A heat exchange device communicates with the flue gas compression device and the air refrigeration device, and the heat exchange device is used to exchange heat between the high-pressure flue gas and the low-temperature air to form high-pressure and low-temperature flue gas, so that the Partial carbon dioxide liquefaction in high-pressure low-temperature flue gas;

The gas-liquid separation device is used for separating the liquefied carbon dioxide in the high-pressure low-temperature flue gas.

In one of the embodiments, the carbon dioxide purification system in the flue gas further includes a flue gas desulfurization device communicated with the flue gas compression device, and the flue gas desulfurization device is used to pressurize the flue gas to form a high-pressure flue gas Before removing the sulfur dioxide in the flue gas.

A method for purifying carbon dioxide in flue gas, comprising the following steps:

Compress flue gas to form high-pressure flue gas;

The high-pressure low-temperature flue gas is heat-exchanged with the low-temperature air to form high-pressure low-temperature flue gas, so that part of the carbon dioxide in the high-pressure low-temperature flue gas is liquefied, wherein the pressure of the high-pressure low-temperature flue gas is 1.5MPa~2.5MPa, and the temperature is - 25℃～-35℃;

Separating the liquefied carbon dioxide in the high-pressure low-temperature flue gas and the tail gas after removing the liquefied carbon dioxide.

In one embodiment, the flue gas is desulfurized before being compressed to remove sulfur dioxide in the flue gas.

In one of the embodiments, removing sulfur dioxide in the flue gas comprises the following steps:

The flue gas is subjected to low-temperature plasma-induced oxidation to oxidize sulfur dioxide in the flue gas to sulfur trioxide;

React the flue gas oxidized by low-temperature plasma with lye, react the sulfur trioxide in the flue gas with the lye reaction solution to generate a solution containing SO ₄ ^2- , and the lye is sodium hydroxide solution or potassium hydroxide solution.

In one embodiment, molecular sieves are used to increase the concentration of carbon dioxide in the flue gas before being compressed.

In one embodiment, after the flue gas is compressed to form high-pressure flue gas, cooling, oil-water separation, and dehydration and drying are sequentially performed before heat exchange with the low-temperature air.

In one of the embodiments, after the flue gas is subjected to oil-water separation, dehydration and drying, and before heat exchange with the low-temperature air, the flue gas is subjected to precision filtration to remove dust in the flue gas.

In one of the embodiments, the low-temperature air is prepared by the following steps: sequentially compressing the air, separating oil from water, dehydrating and drying, and precision filtering to remove water vapor and tiny impurities in the air to form purified air; cooling the purified air to form cold air.

In one of the embodiments, the low-temperature air is prepared by the following steps: sequentially compressing the air, separating oil from water, dehydrating and drying, and precision filtering to remove water vapor and tiny impurities in the air to form purified air; cooling the purified air to form cold air.

The above-mentioned carbon dioxide purification system in flue gas and the method for purifying carbon dioxide in flue gas enable heat exchange between pressurized flue gas and low-temperature air, so that high-pressure flue gas becomes high-pressure low-temperature flue gas. Under high-pressure and low-temperature conditions, the flue gas Part of the carbon dioxide in the flue gas is liquefied to form liquid carbon dioxide. Under the conditions of the pressure of 1.5MPa~2.5MPa and the temperature of -25°C~-35°C, other gases in the flue gas will not be liquefied, so that the carbon dioxide in the flue gas will be liquefied with the flue gas The other gases and impurities in the process are separated, and the purification system and purification process are relatively simple.

Description of drawings

Fig. 1 is a structural schematic diagram of a system for purifying carbon dioxide in flue gas according to an embodiment;

Fig. 2 is a schematic structural diagram of the flue gas desulfurization device in Fig. 1 .

Detailed ways

In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the associated drawings. A preferred embodiment of the invention is shown in the drawings. However, the present invention can be embodied in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of the present invention will be thorough and complete.

It should be noted that when an element is referred to as being “fixed on” another element, it may be directly on the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "left," "right," and similar expressions are used herein for purposes of illustration only.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field of the invention. The terms used herein in the description of the present invention are for the purpose of describing specific embodiments only, and are not intended to limit the present invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

Please refer to FIG. 1 , a carbon dioxide purification system 100 in flue gas according to an embodiment is used for separating and purifying carbon dioxide in flue gas containing carbon dioxide. The carbon dioxide purification system 100 in flue gas includes a flue gas precooling device 10 and a flue gas desulfurization device 20 , molecular sieve 30, flow controller 35, flue gas compression device 40, air purification device 50, air precooling device 60, air refrigeration device 70, heat exchange device 80, air emptying device 85, gas-liquid separation device 90 and carbon dioxide collection Device 95.

The flue gas precooling device 10 includes an induced draft fan 12 and a cooler 14 communicated with the induced draft fan 12 . The temperature of the flue gas discharged from thermal power plants is generally higher than normal temperature, about 130°C. The flue gas is transported to the induced draft fan 12, and after being pressurized by the induced draft fan 12, it is transported to the cooler 14 for primary cooling of the flue gas, so that the flue gas The temperature dropped to near normal temperature.

Please refer to FIG. 2 , the flue gas desulfurization device 20 includes a low-temperature plasma device 22 , an alkali solution contact chamber 24 , a calcium source contact chamber 25 , a recovery device 26 and a calcium sulfate collection device 27 .

The low-temperature plasma device 22 is used to oxidize sulfur dioxide in the flue gas to sulfur trioxide. The low-temperature plasma device 22 communicates with the cooler 14 , and the flue gas primary cooled by the cooler 14 enters the low-temperature plasma device 22 .

The plasma generated by the low-temperature plasma device 22 through pulse discharge contains a large number of high-energy electrons, ions, excited ions and highly oxidizing free radicals, wherein the average energy of active ions is higher than the bond energy of gas molecules. Active ions collide with sulfur dioxide, on the one hand, open gas molecular bonds to generate some nitrogen atom molecules and solid particles, on the other hand, excite oxygen and water vapor in the air to form extremely strong oxidants such as ozone, O- and hydroxyl radicals. These oxidants and sulfur dioxide in the flue gas undergo a series of complex electrochemical reactions with active ions or free radicals as a collective, and finally convert sulfur dioxide into sulfur trioxide.

The lye contact chamber 24 is used for reacting the sulfur trioxide generated by oxidation by the low-temperature plasma device with the lye in the lye contact chamber 120 to generate a solution containing SO ₄ ²⁻ .

The lye is sodium hydroxide (NaOH) solution or potassium hydroxide (KOH) solution. Preferably, the mass concentration of the lye is 7%-15%.

The solution containing SO ₄ ^2- produced by the reaction of sulfur trioxide and lye is sodium sulfate (Na ₂ SO ₄ ) solution or potassium sulfate (K ₂ SO ₄ ) solution. Concrete reaction formula is as follows:

2ROH+SO ₃ →R ₂ SO ₄ +H ₂ O

Wherein, R is K or Na.

In this embodiment, the alkali solution contact chamber 24 communicates with the low temperature plasma device 22 through a pipeline. The lye contact chamber 24 contains lye for reacting with sulfur trioxide. Specifically in this embodiment, a microspray device is provided in the lye contact chamber 24, and the microspray device atomizes the lye into tiny droplets, and sprays the lye to the flue gas that passes into the lye contact chamber 24, so that The flue gas and the atomized lye fully contact and react to form a solution containing SO ₄ ^2- . It should be pointed out that the micro-spraying device can be omitted, and at this time, the flue gas can also be directly passed into the lye to make the sulfur trioxide in the flue gas react with the lye.

The calcium source contact chamber 25 is used to react the solution containing SO ₄ ^2- generated in the alkali liquid contact chamber 24 with the calcium source to convert it into calcium sulfate and recover the alkali liquid.

The calcium source is calcium oxide, calcium hydroxide or calcium hydroxide solution. Preferably, the mass concentration of the calcium hydroxide solution is 5% to 13%.

Specifically, calcium oxide reacts with water in the solution containing SO ₄ ^2- to generate calcium hydroxide (Ca(OH) ₂ ). Therefore, the recovered lye produced by the reaction of the calcium source and the solution containing SO ₄ ^2- is sodium hydroxide solution or potassium hydroxide solution. Concrete reaction formula is as follows:

R ₂ SO ₄ +Ca(OH) ₂ →Ca ₂ SO ₄ +2ROH

Among them, R is K or Na, calcium sulfate (Ca ₂ SO ₄ ) is slightly soluble in water, and calcium sulfate exists in the form of precipitation after multiple reactions.

In this embodiment, the calcium source contact chamber 25 communicates with the alkali solution contact chamber 24 through a pipeline.

Specifically in this embodiment, the calcium source contact chamber 25 is provided with a reaction tank, and the calcium source is accommodated in the reaction tank. During use ^, the solution containing SO produced in the lye contact chamber ₂₄ can be passed into the reaction tank by a pipeline. , react with the calcium source in the reaction tank to generate calcium sulfate precipitation and recover lye. In other embodiments, the calcium source in the calcium source contact chamber can be added to the solution containing SO ₄ ^2- to react.

The recovery device 26 is used to transport the recovered lye to the lye contact chamber 24 . Specifically, in this embodiment, the recovery device 26 is a pipeline, and the recovery device 26 transports the recovered lye to the lye contact chamber 24 and enters the microspray device.

The calcium sulfate collection device 27 is used to collect the calcium sulfate produced in the calcium source contact chamber 25 . The calcium sulfate collected by the calcium sulfate collecting device 27 can be used for the production of industrial gypsum.

The molecular sieve 30 communicates with the lye contact chamber 24 of the flue gas desulfurization device 20 , and the flue gas reacted with the lye in the lye contact chamber 24 enters the molecular sieve 30 . The molecular sieve 30 is used to filter the flue gas to increase the content of carbon dioxide in the flue gas. In this embodiment, the molecular sieve 30 increases the volume percentage of carbon dioxide in the flue gas to more than 50%. Ineffective components separated by the molecular sieve 30 are discharged directly.

The flow controller 35 communicates with the molecular sieve 30 and is used for controlling the flow rate of the flue gas filtered by the molecular sieve 30 .

The flue gas compression device 40 includes a compressor 41 , a cooler 42 , an oil-water separator 43 , a dryer 44 , and a precision filter 45 .

The compressor 41 communicates with the flow controller 35 . Compressor 41 is used to compress flue gas. In this embodiment, the compressor 41 increases the pressure of the flue gas to 1.5MPa~2.5MPa.

The cooler 42 communicates with the compressor 41 . The cooler 42 is used to reduce the temperature of the flue gas output by the compressor 41 .

The oil-water separator 43 communicates with the cooler 42 . The oil-water separator 43 is used for separating the oil-water in the flue gas cooled by the cooler 42 . After the flue gas is compressed by the compressor 41 and cooled by the cooler 42, some impurities are liquefied, and the oil and water in the flue gas can be removed by using the oil-water separator 43 to purify the flue gas. In this embodiment, the oil-water separator 43 is a cyclone separator.

The dryer 44 communicates with the oil-water separator 43 . The dryer 44 is used for dehydrating and drying the flue gas purified by the oil-water separator 43 .

The precision filter 45 communicates with the drier 44 . The precision filter 45 is used to remove the dust in the flue gas dehydrated and dried by the drier 44 .

The air cleaning device 50 includes an air compressor 51 , an oil-water separator 52 , a dryer 53 and a precision filter 54 .

The air compressor 51 is used to compress air. The air at normal temperature and pressure increases to 0.6MPa~1.2MPa after being compressed by the air compressor 51 .

The oil-water separator 52 communicates with the air compressor 51 . The oil-water separator 52 is used for separating oil-water in the air compressed by the air compressor 51 . After the air is compressed by the air compressor 51, some impurities are liquefied, and the oil and water in the flue gas can be removed by using the oil-water separator 52 to purify the air preliminarily. In this embodiment, the oil-water separator 52 is a cyclone separator.

The dryer 53 communicates with the oil-water separator 52 . The dryer 53 is used for dehydrating and drying the air purified by the oil-water separator 52 .

The precision filter 54 communicates with the drier 53 . The precision filter 54 is used to remove dust in the air dehydrated and dried by the drier 53 .

The air precooling device 60 includes a cooler 61 and a heat exchanger 62 .

The cooler 61 communicates with the precision filter 54 . The cooler 61 is used to pre-cool the air purified by the air purification device 50 to normal temperature.

The heat exchanger 62 communicates with the cooler 61 .

Air cooling unit 70 communicates with heat exchanger 62 . The air cooling device 70 is used to cool the air delivered by the heat exchanger 62 to -40°C~-60°C. In this embodiment, the air cooling device 70 is a gas wave refrigerator. Preferably, there are two gas wave refrigerators, the two gas wave refrigerators are arranged in parallel, and one of the gas wave refrigerators is in standby. It can be understood that the air cooling device 70 may also be a turbo expander.

The heat exchange device 80 communicates with the air refrigeration device 70 and the precision filter 45 of the flue gas compression device 40 at the same time. The low-temperature air prepared by the air refrigeration device 70 and the high-pressure flue gas prepared by the compression device 40 perform heat exchange in the heat exchange device 80, so that the high-pressure flue gas becomes a pressure of 1.5MPa~2.5MPa and a temperature of -25°C~-35°C. ℃ high-pressure low-temperature flue gas. Under the conditions of high pressure and low temperature, part of the carbon dioxide in the flue gas is liquefied to form liquid carbon dioxide.

The air evacuation device 85 communicates with the heat exchange device 80 . The air after heat exchange in the heat exchanging device 80 enters into the air exhausting device 85 and is exhausted through the air discharging device 85 .

The gas-liquid separation device 90 communicates with the heat exchange device 80 and the heat exchanger 62 of the air precooling device 60 at the same time. The flue gas containing liquid carbon dioxide after heat exchange in the heat exchange device 80 enters the gas-liquid separation device 90 to separate the liquid carbon dioxide and remove the tail gas of liquefied carbon dioxide. Due to its low temperature, the exhaust gas is sent to the heat exchanger 62 of the air precooling device 60 as a cooling source, and exchanges heat with the air pre-cooled by the cooler 61 . Since the carbon dioxide in the flue gas cannot be completely liquefied, the tail gas still contains a relatively high concentration of carbon dioxide. The tail gas after heat exchange by the heat exchanger 62 enters the compressor 41 of the flue gas compression device 40 again to separate the carbon dioxide.

The carbon dioxide collection device 95 is used to collect the liquid carbon dioxide separated by the gas-liquid separation device 90 . The carbon dioxide collecting device 95 cans the liquid carbon dioxide.

In the above-mentioned carbon dioxide purification system 100 in flue gas, the flue gas compression device 40 pressurizes the flue gas to form high-pressure flue gas, and the air refrigeration device 70 cools the air to form low-temperature air, and the high-pressure flue gas and low-temperature air are heated through the heat exchange device 80 Exchange to make high-pressure flue gas into high-pressure low-temperature flue gas, and use high-pressure and low-temperature methods to liquefy part of the carbon dioxide in the flue gas to form liquid carbon dioxide. Under this condition, other gases in the flue gas will not be liquefied, so that the liquefaction of carbon dioxide in the flue gas is separated from other gases and impurities in the flue gas, which is relatively simple; while other low-temperature gases that are not liquefied can recover the cold energy in the heat exchanger 67 It is used for pre-cooling the air of the air refrigeration device 70, so as to realize the comprehensive utilization of energy.

It can be understood that when the temperature of the flue gas for carbon dioxide purification is close to normal temperature, the flue gas precooling device 10 can be omitted; when the sulfur dioxide content in the flue gas is low, the flue gas desulfurization device 20 can be omitted, and the molecular sieve 30 can be omitted. It is enough to directly transport the flue gas to the flue gas compression device 40 to compress it into high-pressure flue gas; It can be omitted, and the compressed flue gas can be directly transported to the heat exchange device 80; similarly, when there is less oil gas, water vapor and dust in the air, the air purification device 50 can be omitted, and the air is directly transported to the air pre-cooling The device 60 is enough; the air precooling device 60 can be omitted, and at this time, it is enough to directly transport the air to the air cooling device 70 .

Please refer to Fig. 1 to Fig. 2 at the same time, the method for purifying carbon dioxide in flue gas in one embodiment is used to separate and purify carbon dioxide in flue gas containing carbon dioxide, including the following steps:

Step S101, pre-cooling the flue gas.

The temperature when the flue gas is discharged is about 130°C. Pre-cooling the flue gas includes pre-pressurizing the flue gas and pre-cooling the pre-pressurized flue gas.

When pre-pressurizing the flue gas, increase the pressure of the flue gas to 0.15MPa~0.5MPa. In this embodiment, pre-pressurization is performed using the induced draft fan 12 .

When pre-cooling the flue gas, pre-cool the flue gas to normal temperature. In this embodiment, the cooler 14 is used to pre-cool the flue gas.

Step S102, performing desulfurization treatment on the flue gas.

Desulfurization of flue gas includes the following steps:

The flue gas is subjected to low-temperature plasma-induced oxidation to oxidize sulfur dioxide in the flue gas to sulfur trioxide;

The flue gas oxidized by the low-temperature plasma is reacted with the lye, and the sulfur trioxide in the flue gas is reacted with the lye reaction solution to form a solution containing SO ₄ ^2- .

The lye is sodium hydroxide (NaOH) solution or potassium hydroxide (KOH) solution. Preferably, the mass concentration of the lye is 7%-15%.

Further, it is possible to react the solution containing SO ₄ ^2- with the calcium source, then collect the calcium sulfate and reclaim the lye generated by the reaction of the solution containing SO ₄ ^2- and the calcium source, and use the collected reclaimed lye for the process The low-temperature plasma stimulates the oxidizing flue gas reaction.

In this embodiment, the flue gas is desulfurized using the flue gas desulfurization device 20 .

Step S103, using molecular sieves to increase the concentration of carbon dioxide in the flue gas.

The desulfurized flue gas enters the molecular sieve 30 to increase the volume percentage of carbon dioxide in the flue gas to more than 50%.

Step S104, compressing the flue gas to form high-pressure flue gas.

Preferably, the pressure of the high-pressure flue gas is 1.5MPa~2.5MPa.

In this embodiment, a compressor 41 is used to compress the flue gas treated with molecular sieves to increase the pressure of the flue gas to 1.5MPa~2.5MPa.

Further, a flow controller 35 is used to control the flow of flue gas delivered to the compressor 41 .

Step S105 , cooling, oil-water separation, and dehydration and drying are performed sequentially on the flue gas.

After the flue gas is cooled, the temperature drops to 35°C~55°C. In this embodiment, the high-pressure flue gas compressed by the compressor 41 first enters the cooler 42 for cooling to reduce the temperature of the flue gas output by the compressor 41 .

The flue gas cooled by the cooler 42 uses the oil-water separator 43 to remove the oil and water in the flue gas to purify the flue gas. In this embodiment, the oil-water separator 43 is a cyclone separator.

The flue gas that has undergone oil-water separation to remove oil and water is dehydrated and dried with a drier 44 to remove water vapor in the flue gas.

Step S106, performing precision filtration on the flue gas to remove impurities in the flue gas

In this embodiment, a precision filter 45 is used to filter the flue gas.

Step S107, sequentially compressing the air, separating oil from water, dehydrating and drying, and precision filtering to form purified air.

In this embodiment, use the air purification device 50 to purify the air, specifically, use the compressed air machine 51 to compress the air, so that the air pressure of the compressed air is 0.6MPa~1.2MPa; after the air is compressed by the air compressor 51, some impurities are liquefied into Oil and water, use the oil and water in the air compressed by the air compressor 51 to separate; use the dryer 53 to further remove the water vapor in the air; use the precision filter 54 to remove dust and particles in the dried and dehydrated air.

Preferably, the oil-water separator 52 is a cyclone separator.

Step S108, pre-cooling the purified air.

In this embodiment, the cooler 61 is used to pre-cool the purified air to normal temperature.

Step S109, cooling the purified air to form low-temperature air.

The temperature of low-temperature air is -40°C to -60°C.

In this embodiment, the air is cooled to -40°C to -60°C using the air cooling device 70 . Preferably, the air cooling device 70 is a gas wave refrigerator.

The pressure of the low temperature air is 0.6MPa~1.2MPa, preferably 0.8MPa.

Step S110, heat-exchange the precision-filtered flue gas with low-temperature air to form high-pressure low-temperature flue gas, so that part of the carbon dioxide in the high-pressure low-temperature flue gas is liquefied, the pressure of the high-pressure low-temperature flue gas is 1.5MPa~2.5MPa, and the temperature is -25 ℃～-35℃.

In this embodiment, the finely filtered flue gas and low-temperature air exchange heat through the heat exchange device 80, so that the high-pressure flue gas becomes high-pressure and low-temperature flue gas. Under the conditions of air pressure of 1.5MPa~2.5MPa and temperature of -25℃~-35℃, part of the carbon dioxide in the flue gas is liquefied to form liquid carbon dioxide.

The low-temperature air becomes normal-temperature air after heat exchange and can be discharged. In this embodiment, the normal-temperature air is evacuated through the air evacuation device 85 .

Step S110, separating the liquefied carbon dioxide in the high-pressure low-temperature flue gas and the tail gas from which the liquefied carbon dioxide is removed.

The flue gas containing liquid carbon dioxide formed after heat exchange in the heat exchange device 80 enters the gas-liquid separation device 90 to separate the liquid carbon dioxide and remove the tail gas of liquefied carbon dioxide.

Step S111, collecting liquefied carbon dioxide.

In this embodiment, the carbon dioxide collection device 95 is used to collect the liquid carbon dioxide and fill the liquid carbon dioxide.

Step S112, exchanging heat between the exhaust gas and the pre-cooled air.

The temperature of the separated tail gas is lower, and it can be used as a cold source to pre-cool the pre-cooled air again. In this embodiment, the separated tail gas exchanges heat with the pre-cooled air through the heat exchanger 62 .

Step S113, re-separating and purifying the heat-exchanged tail gas.

Since the carbon dioxide in the flue gas cannot be completely liquefied, the tail gas still contains a relatively high concentration of carbon dioxide. In the embodiment of this municipality, the tail gas after heat exchange by the heat exchanger 62 enters the compressor 41 of the flue gas compression device 40 again to separate the carbon dioxide.

In the above method for purifying carbon dioxide in flue gas, heat exchange is performed between the pressurized flue gas and low-temperature air, so that the high-pressure flue gas becomes high-pressure low-temperature flue gas, and under the conditions of high pressure and low temperature, part of the carbon dioxide in the flue gas is liquefied to form a liquid Carbon dioxide, under the conditions of pressure of 1.5MPa~2.5MPa and temperature of -25℃~-35℃, other gases in the flue gas will not be liquefied, so that the carbon dioxide in the flue gas will be liquefied and other gases and impurities in the flue gas will be liquefied The separation and purification process is relatively simple; while other unliquefied low-temperature gases exchange heat with the pre-cooled air to recycle the cold energy, thereby realizing the comprehensive utilization of energy.

It should be noted that the steps in the method for purifying carbon dioxide in flue gas are not necessarily performed in the order listed, for example, the steps of processing flue gas to form high-pressure flue gas (step S101 to step S106) and the treatment of air The step of forming low-temperature air (step S107 to step S109 ) can be performed simultaneously, as long as the high-pressure flue gas and the low-temperature air perform heat exchange to form high-pressure low-temperature flue gas.

It can be understood that steps S101 to S103 can be omitted, and in this case, step S104 can be directly performed to compress the flue gas. When there are few impurities in the flue gas, no purification or desulfurization is required, and there is little water vapor, steps S105 and S106 can also be omitted. In this case, the air compressed in step S104 can be directly exchanged with low-temperature air. When there are few impurities in the air that do not need to be purified and there is little water vapor, step S106 and step S107 can be omitted, and step S108 can be directly executed at this time. Step S108 can also be omitted, and in this case, the air is directly cooled to form low-temperature air. Step S109 can be omitted, and low-temperature air can also be directly purchased at this time, without self-made. Step S112 and step S113 can be omitted.

The above-mentioned embodiments only express several implementation modes of the present invention, and the description thereof is relatively specific and detailed, but should not be construed as limiting the patent scope of the present invention. It should be pointed out that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent for the present invention should be based on the appended claims.

Claims (9)

1. a carbon dioxide in flue gas purification system, for separating of, the carbon dioxide of purifying in the flue gas that contains carbon dioxide, is characterized in that, described carbon dioxide in flue gas purification system comprises:

Flue gas compression set, described flue gas compression set comprises compressor, for flue gas pressurization is formed to high pressure flue gas;

Air refrigerating devie, for by the cooling formation Cryogenic air of air;

Heat-exchange device, be communicated with described flue gas compression set and described air refrigerating devie, described heat-exchange device is for described high pressure flue gas and described Cryogenic air are carried out to heat exchange formation high pressure low temperature flue gas, so that part co 2 liquefaction in described high pressure low temperature flue gas;

Gas-liquid separation device, for separating of the carbon dioxide liquefying in described high pressure low temperature flue gas and the tail gas of removing the carbon dioxide of liquefaction;

Air precooler, described air precooler comprises cooler and heat exchanger, the heat exchanger of described air precooler is communicated with described gas-liquid separation device, tail gas due to temperature compared with the low heat exchanger that is delivered to air precooler as low-temperature receiver, the air pre-cooled with the cooler of process air precooler carries out heat exchange, and the compressor that the tail gas after heat exchanger heat exchange enters flue gas compression set again carries out the separation of carbon dioxide again;

Flue gas pre-cooler, comprises air-introduced machine and the cooler being communicated with air-introduced machine;

Flue gas desulfur device, comprise low temperature plasma device, alkali lye contact chamber, calcium source contact chamber, retracting device and calcium sulfate gathering-device, it is sulfur trioxide by the oxidizing sulfur dioxide of flue gas that low temperature plasma device is used for, low temperature plasma device is communicated with the cooler of flue gas pre-cooler, the elementary cooled flue gas of cooler through flue gas pre-cooler enters low temperature plasma device, and alkali lye contact chamber is for containing SO by the sulfur trioxide that oxidation generates through low temperature plasma device and the generation of the alkaline reaction in alkali lye contact chamber ₄ ^2-solution, alkali lye contact chamber is communicated with low temperature plasma device by pipeline, the contain SO of calcium source contact chamber for alkali lye contact chamber is generated ₄ ^2-solution react with calcium source and be converted into calcium sulfate and reclaim alkali lye, calcium source contact chamber is communicated with alkali lye contact chamber by pipeline, retracting device is for recovery alkali lye is delivered to alkali lye contact chamber, and calcium sulfate gathering-device is for collecting the calcium sulfate producing in the contact chamber of calcium source.

2. carbon dioxide in flue gas purification system according to claim 1, it is characterized in that, described carbon dioxide in flue gas purification system also comprises the flue gas desulfur device being communicated with described flue gas compression set, and described flue gas desulfur device is for removing the sulfur dioxide of described flue gas before forming high pressure flue gas in described flue gas pressurization.

3. a carbon dioxide in flue gas method of purification, is characterized in that, comprises the following steps:

Compression flue gas forms high pressure flue gas;

Described high pressure flue gas and Cryogenic air are carried out to heat exchange formation high pressure low temperature flue gas, so that part co 2 liquefaction in described high pressure low temperature flue gas, the air pressure of wherein said high pressure low temperature flue gas is 1.5MPa～2.5MPa, and temperature is-25 ℃～-35 ℃;

The carbon dioxide of the liquefaction in separated described high pressure low temperature flue gas and remove the carbon dioxide of liquefaction after tail gas;

Described tail gas and the air through pre-cooled are carried out to heat exchange, the tail gas through heat exchange is re-started to separating-purifying;

Described flue gas first carries out desulfurization processing to remove the sulfur dioxide in flue gas to flue gas before compression, flue gas is carried out to desulfurization processing to be comprised the following steps: flue gas is carried out to low temperature plasma and excite oxidation, making the oxidizing sulfur dioxide in flue gas is sulfur trioxide, to through low temperature plasma, excite flue gas and the alkaline reaction of oxidation, and make sulfur trioxide and the generation of alkaline reaction solution reaction in described flue gas contain SO ₄ ^2-solution, will contain SO ₄ ^2-solution react with calcium source, regather and contain SO ₄ ^2-solution react the calcium sulfate generating with calcium source and reclaim alkali lye, and by the recovery alkali lye of collection for and through low temperature plasma, excite the smoke reaction of oxidation.

4. carbon dioxide in flue gas method of purification according to claim 3, is characterized in that, described alkali lye is sodium hydroxide solution or potassium hydroxide solution.

5. carbon dioxide in flue gas method of purification according to claim 3, is characterized in that, described flue gas is first used molecular sieve to improve carbon dioxide in flue gas concentration before compression.

6. carbon dioxide in flue gas method of purification according to claim 3, is characterized in that, compression flue gas forms after high pressure flue gas, carry out carrying out successively before heat exchange cooling, water-oil separating and dehydrate processing with described Cryogenic air.

7. carbon dioxide in flue gas method of purification according to claim 6, is characterized in that, described flue gas carried out secondary filter to remove the dust in flue gas carry out heat exchange after carrying out water-oil separating and dehydrating, with described Cryogenic air before.

8. carbon dioxide in flue gas method of purification according to claim 3, it is characterized in that, described Cryogenic air is prepared by following steps: air is compressed successively, water-oil separating, dehydrated and secondary filter forms and purifies air to remove airborne steam and minute impurities; Described in cooling, purify air to form Cryogenic air.

9. carbon dioxide in flue gas method of purification according to claim 8, is characterized in that, described in purify air and before cooling forms Cryogenic air, carry out heat exchange with described tail gas and carry out pre-cooled.