CN106422733A - Heating furnace tail gas carbon capturing device and method achieved by means of slab yard waste heat - Google Patents

Abstract

The invention discloses a heating furnace tail gas carbon capture device utilizing the waste heat of a slab storage, including a carbon capture unit and a waste heat utilization unit; the invention also discloses a heating furnace tail gas carbon capture method utilizing the waste heat of a slab storage , including carbon capture cycle and waste heat utilization cycle; the exhaust gas of the heating furnace enters from the absorption tower through the fan, a chemical reaction occurs in the absorption tower, and the flue gas is discharged from the absorption tower; the rich liquid flows out from the absorption tower and enters the lean-rich liquid heat exchanger , enter the desorption tower after heating; the bottom of the desorption tower is heated by a reboiler, and the overflowing carbon dioxide is discharged from the top of the desorption tower and enters the condenser and the reflux pump in turn; the lean liquid heated by the reboiler enters the lean-rich liquid for heat exchange The lean liquid pump is pressurized into the absorption tower; the waste heat utilization cycle steps are: the exhaust gas of the heating furnace enters the slab warehouse for further temperature rise, and then enters the waste heat boiler with supplementary combustion to heat the feed water, and the water vapor enters the reboiler for carbon capture. The set unit provides heat.

Description

A carbon capture device and method for heating furnace tail gas utilizing waste heat from slab warehouse

technical field

The invention relates to the technical field of comprehensive utilization of waste heat resources and control of greenhouse gases, in particular to a carbon capture device and method for tail gas of a heating furnace that utilizes waste heat of a slab storehouse.

Background technique

At present, the greenhouse effect and global climate change are hot issues of common concern to all mankind. The greenhouse effect means that the sun's short-wave radiation can penetrate the atmosphere and enter the ground, while the long-wave radiation released by the warming of the ground is absorbed by the greenhouse gases in the atmosphere, resulting in the effect of atmospheric warming. Greenhouse gases mainly include water vapor, carbon dioxide, methane, and various chlorofluorocarbons. The content of water vapor in the atmosphere is higher than that of man-made greenhouse gases such as carbon dioxide, and it is the main gas that causes the natural greenhouse effect. However, the content of water vapor in the atmosphere is relatively stable. Therefore, it is generally believed that water vapor in the atmosphere is not directly affected by human activities, and the greenhouse gases emitted by humans, mainly carbon dioxide, are emitted with the development of human industrial and agricultural activities. The amount of carbon dioxide is increasing year by year, especially carbon dioxide, which contributes more to the greenhouse effect than other man-made greenhouse gases.

There are many technical means to control carbon dioxide emissions, such as improving energy efficiency, reducing equipment heat loss, increasing waste heat and energy recovery equipment, using clean alternative fuels, etc., but the fastest and most effective way to reduce carbon dioxide emissions is carbon dioxide emissions. Capture and storage technology.

Carbon dioxide capture and storage technology refers to the separation of carbon dioxide produced by industry and related energy industries through carbon capture technology, and then transports and stores it to places isolated from the atmosphere such as the seabed or underground through carbon storage means. This technology is currently considered to be one of the most important technologies for tackling global climate change in the short term.

The current mainstream carbon capture technologies are mainly chemical absorption and physical adsorption. Most of the more mature commercial chemical absorption methods use ethanolamine absorbent, which has a good capture effect and the separated carbon dioxide is pure, but the capture energy consumption is high. Although the physical adsorption method greatly reduces energy consumption compared with the chemical absorption method, the capture efficiency is not high, and the purity of the separated carbon dioxide is relatively low.

At present, large-scale carbon capture technologies are mainly concentrated in power plants, which provide heat for the carbon capture system by pumping low-pressure cylinder steam, which will greatly reduce the net efficiency of power generation.

Taking the feasibility of carbon capture as a starting point, many inventors have innovated in the field of absorbents, trying to reduce system energy consumption by replacing traditional absorbents. For example, the CN102294169A patent document discloses a method for enhancing the absorption of carbon dioxide by using an oil-in-water ionic liquid emulsion. The ionic liquid is used as the dispersed liquid phase to prepare an oil-in-water ionic liquid emulsion. The effect of the ionic liquid dispersion system on gas absorption According to different absorption processes, different enhanced carbon dioxide absorption processes are adopted to strengthen physical absorption, and the absorption rate can be increased by 50% of the original; intensified chemical absorption, the amount of triethanolamine is reduced by 29% of the original, thereby reducing the corrosion of the amine solution on the equipment and reducing the Small pollution to the environment, and reduce the temperature of solvent regeneration, thereby reducing the energy consumption of solvent regeneration. However, the investment consumption of the preparation of this ionic liquid has not been considered, so it may face the dilemma of practical application.

Other inventors are looking at combining other energy sources with carbon capture technologies. For example, the CN103372371A patent document proposes a system that uses solar collectors to drive organic Rankine cycle power generation, and then supplies energy for carbon capture in power plants, thereby realizing cascade utilization of energy and reducing energy consumption for carbon capture. As another example, CN204395731U patent document proposes to use the heat generated by the exhaust gas oxidation device in the pit mouth power plant for the regenerative heating system of the flue gas carbon dioxide capture system of the pit mouth power plant to achieve a significant reduction in the cost of carbon dioxide capture. At the same time, it realizes the emission reduction of methane greenhouse gas in the mining area and the energy utilization of exhaust gas. The feature of the above patents is to rationally utilize the existing low-grade heat source in the plant area to provide energy for the carbon capture system. However, for the low-grade heat sources that actually exist in iron and steel enterprises, the above scheme is not suitable for a large-scale carbon capture system.

The present invention focuses on another high energy consumption industry: iron and steel enterprises. According to statistics, 40% of global carbon dioxide emissions come from power plants, 23% from the transportation industry, and 22% from steel mills, cement plants, oil refineries and other enterprises. Due to the long process of iron and steel enterprises, many equipments and complex processes, the current status of a large amount of fuel consumption and carbon dioxide emissions cannot be ignored. However, unlike power plants, iron and steel enterprises have a large amount of steam to supply the carbon capture system, so where the energy required by the carbon capture system comes from is one of the key points that bother iron and steel enterprises to implement carbon capture technology. Related literature and The number of patents is small.

Based on the above, it can be seen that the existing related technologies cannot achieve the goal of an ideal carbon capture system suitable for iron and steel enterprises. At present, it is urgent to develop a system that utilizes the waste heat existing in iron and steel enterprises for carbon capture.

Therefore, those skilled in the art are committed to developing a carbon capture device and method for heating furnace tail gas that utilizes the waste heat of the slab warehouse, rationally utilizes waste heat resources, and significantly reduces the energy consumption of carbon dioxide regeneration, which neither affects product production, nor will Adding additional CO2 emissions during decarbonisation.

Contents of the invention

In view of the above-mentioned defects of the prior art, the technical problem to be solved by the present invention is a heating furnace tail gas carbon capture device and method that utilizes the waste heat of the slab warehouse, rationally utilizes waste heat resources, and significantly reduces the energy consumption of carbon dioxide regeneration without affecting product production without adding additional carbon dioxide emissions in the decarbonization process.

In order to achieve the above object, the present invention provides a carbon capture device and method for heating furnace tail gas utilizing the waste heat of the slab warehouse, including a carbon capture unit and a waste heat utilization unit, wherein the carbon capture unit includes a fan, an absorption tower, a desorption Tower, lean liquid pump, rich liquid pump, reflux pump, lean rich liquid heat exchanger, reboiler and condenser; waste heat utilization unit includes heating furnace, slab storage, waste heat boiler, cooling tower, feed water pump and chimney;

The absorption tower has a first end and a second end, the second end includes a first part and a second part, the fan is connected to the first part of the second end of the absorption tower, and the second end of the second end of the absorption tower The part is connected with the lean-rich liquid heat exchanger through the rich liquid pump, the first end of the absorption tower is connected with the lean-rich liquid heat exchanger through the lean liquid pump, and the lean-rich liquid heat exchanger is respectively connected with the top and bottom of the desorption tower. The top of the desorption tower is connected with the condenser and the reflux pump respectively to form a condensation return circuit; the bottom of the desorption tower is respectively connected with the waste heat boiler and the cooling tower through the reboiler;

The waste heat boiler is connected to the chimney; the cooling tower is connected to the waste heat boiler through the feed water pump; the heating furnace is connected to the waste heat boiler through the slab storage.

Further, the waste heat boiler is a waste heat boiler with supplementary combustion.

Furthermore, the waste heat boiler with supplementary combustion includes an economizer, an evaporation heating surface, a superheater and a steam drum.

Further, the absorption tower is a tray tower with 10-15 stages of trays.

The present invention also provides a carbon capture method for heating furnace tail gas utilizing the waste heat of the slab warehouse, including a carbon capture cycle and a waste heat utilization cycle;

The carbon capture cycle steps are as follows: after desulfurization, denitrification and dust removal, the exhaust gas of the heating furnace enters from the first part of the absorption tower through a fan, and a chemical reaction occurs in the absorption tower, and the flue gas is discharged from the first end of the absorption tower; the rich liquid is discharged from the absorption tower The second part of the tower flows out and enters the lean-rich liquid heat exchanger, and enters the desorption tower after being heated; the bottom of the desorption tower is heated by a reboiler, and the overflowing carbon dioxide is discharged from the top of the desorption tower and enters the condenser and the reflux pump in turn; The lean liquid heated by the reboiler enters the lean-rich liquid heat exchanger, and is pressurized by the lean liquid pump to enter the absorption tower;

The cycle steps of waste heat utilization are as follows: the tail gas of the heating furnace enters the slab warehouse for further temperature rise, and then enters the waste heat boiler with supplementary combustion to heat the feed water, and the water vapor enters the reboiler to provide heat for the carbon capture unit.

Further, the exhaust gas from the heating furnace reacts countercurrently with the absorbent in the absorption tower.

Further, the slab warehouse includes three sub-stores of high temperature, medium temperature and low temperature, and the tail gas of the heating furnace passes through the three sub-stores of low temperature, medium temperature and high temperature in sequence, so that the tail gas is heated.

Furthermore, the waste heat utilization cycle also includes a water circulation system, and the water circulation steps are: the water vapor in the reboiler is cooled into liquid water through a cooling tower, and then pressurized by a feed water pump into a waste heat boiler with supplementary combustion for heating.

Further, the absorbent is ethanolamine.

Further, the concentration of ethanolamine is 26.5%-32%.

technical effect

1. Using the exhaust gas of the heating furnace as the basic heat source, the waste heat resource is rationally used, and the energy consumption of carbon dioxide regeneration is significantly reduced. It will neither affect product production nor increase additional carbon dioxide emissions during the decarbonization process. Basically, the waste heat in the steel rolling workshop of steel enterprises is used to capture carbon dioxide, reducing the energy consumption burden for steel enterprises.

2. Use the waste heat of the slab warehouse to further heat the waste gas to realize the cascade utilization of energy.

3. Use waste heat boiler with supplementary combustion to ensure continuity of heat supply. When intermittent furnace temperature changes in iron and steel enterprises lead to fluctuations in waste heat, a small amount of fuel can be supplemented, such as blast furnace gas, to ensure that the heat supplied to the carbon capture unit remains constant.

The idea, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings, so as to fully understand the purpose, features and effects of the present invention.

Description of drawings

Fig. 1 is a schematic structural diagram of a carbon capture device for heating furnace tail gas utilizing waste heat from a slab storehouse according to a preferred embodiment of the present invention.

detailed description

As shown in Figure 1, a preferred embodiment of the present invention provides a carbon capture device and method for heating furnace tail gas utilizing the waste heat of the slab warehouse, including a carbon capture unit and a waste heat utilization unit, wherein the carbon capture unit Including fan 1, absorption tower 2, desorption tower 3, lean liquid pump 4, rich liquid pump 5, return pump 6, lean-rich liquid heat exchanger 7, reboiler 8 and condenser 9; waste heat utilization unit includes heating furnace 10 , slab warehouse 11, waste heat boiler 12, cooling tower 13, feed water pump 14 and chimney 15;

The absorption tower 2 has a first end and a second end, the second end includes a first part and a second part, the fan 1 is connected with the first part of the second end of the absorption tower 2, and the second end of the absorption tower 2 The second part of the absorption tower 2 is connected with the lean-rich liquid heat exchanger 7 through the rich liquid pump 5, and the first end of the absorption tower 2 is connected with the lean-rich liquid heat exchanger 7 through the lean liquid pump 4, and the lean-rich liquid heat exchange Device 7 is connected with the top and the bottom of desorption tower 3 respectively, and the top of desorption tower 3 is connected with condenser 9 and reflux pump 6 respectively, and forms a condensation reflux circuit; The bottom of desorption tower 3 passes through reboiler 8 respectively It is connected with waste heat boiler 12 and cooling tower 13; waste heat boiler 12 is connected with chimney 15; cooling tower 13 is connected with waste heat boiler 12 through feed water pump 14; heating furnace 10 is connected with waste heat boiler 12 through slab storage 11. The waste heat boiler 12 is a waste heat boiler with supplementary combustion. Waste heat boiler with supplementary combustion includes economizer, evaporation heating surface, superheater and steam drum, etc. The absorption tower 2 is a tray tower, the number of trays is 10-15, and the internal pressure of the absorption tower 2 is 1 atm.

Another preferred embodiment of the present invention also provides a carbon capture method for heating furnace tail gas utilizing the waste heat of the slab warehouse, including a carbon capture cycle and a waste heat utilization cycle;

The carbon capture cycle steps are as follows: after desulfurization, denitrification and dust removal, the tail gas of the heating furnace enters from the first part of the absorption tower through a fan, a chemical reaction occurs in the absorption tower, and the flue gas is discharged from the first end of the absorption tower. Before the tail gas of the heating furnace enters the carbon capture unit, it goes through desulfurization, denitrification and dust removal processes to remove sulfides, nitrides, fly ash, etc. To about 60 ℃, through the fan 1, pressurize to 1.2atm appropriately, the flue gas flow rate is 1050kmol/h (of which water vapor accounts for 1.6%, CO ₂ accounts for 28%, N ₂ accounts for 68.4%, O ₂ accounts for 2%), enter The absorption tower (2) reacts countercurrently with ethanolamine.

Heating furnaces in iron and steel enterprises are equipment used to heat billets. Since the fuel is usually a mixture of blast furnace gas and coke oven gas, the concentration of carbon dioxide in the exhaust gas after combustion is higher than that of power plants, generally reaching about 28%, while power plants Carbon dioxide in the exhaust gas of the boiler only accounts for 8%-18%, so the concentration of ethanolamine absorbent designed in the present invention is slightly higher than the decarbonization concentration of traditional power plants, which is 26.5%-32%. The final selected ethanolamine concentration is 28.5%.

The rich liquid after the reaction of the absorbent ethanolamine and carbon dioxide flows out from the second part of the absorption tower 2 and enters the lean-rich liquid heat exchanger 7 for preliminary heating, and enters the desorption tower 3 after being heated to 95-105 °C, and the internal pressure of the desorption tower 3 It is 1.9atm, the reflux ratio is 2.02, and the number of trays is 10-15; in the desorption tower 3, the rich liquid is further heated, and the equipment for providing heat is that the bottom end of the desorption tower 3 passes through the reboiler 8, and passes through the reboiler 8 Heating, heating the rich liquid to 110-120°C, so that the carbon dioxide is completely desorbed and discharged from the top of the desorption tower 3. Since the discharged carbon dioxide contains a large amount of water, the overflowing carbon dioxide is discharged from the top of the desorption tower and enters the condenser and the reflux pump in turn , the temperature of the condensed water is 25-30°C, and the refluxed water continues to enter the desorption tower 3 for circulation. The lean liquid heated by the reboiler 8 enters the lean-rich liquid heat exchanger, and after the temperature drops to 45-50°C, it is pressurized by the lean liquid pump to 1.8 atm and re-enters the absorption tower to complete a carbon capture cycle.

The waste heat utilization cycle is to use the tail gas of the heating furnace as the basic heat carrier. The exhaust gas discharge temperature of the heating furnace 10 is about 250°C, and the waste heat of the slab warehouse is used to further increase the temperature. The specific steps are: the tail gas of the heating furnace enters the slab storehouse for further heating, the cooling capacity of the continuous casting slab in the slab storehouse 11 is 400-500t/h, and the surface temperature of the billet is 400-1200°C. In the three sub-stores of medium temperature and low temperature, the temperature of the steel billet is slowly reduced. The tail gas from the heating furnace 10 first enters the low-temperature slab storage, passes through the medium-temperature slab storage, and finally flows out from the high-temperature slab storage. The temperature of the heated furnace tail gas can reach 450-500°C, and the high-temperature tail gas heats the feed water in the waste heat boiler. Then it enters the waste heat boiler with supplementary combustion to heat the feed water, and the water vapor enters the reboiler to provide heat for the carbon capture unit. If the temperature or flow rate of the exhaust gas in the heating furnace 10 fluctuates greatly, or the amount of steel slabs in the slab warehouse 11 changes greatly, an appropriate amount of blast furnace gas can be burned in the waste heat boiler 12 with supplementary combustion to maintain uniform and stable heat, and the blast furnace gas can be burned The carbon dioxide produced will not exceed 5% of the system's capture capacity, but has an insurance effect on maintaining thermal stability.

The waste heat utilization cycle also includes a water circulation system. The water circulation steps are: the water vapor in the reboiler is cooled into liquid water through the cooling tower, and then pressurized by the feed water pump into the waste heat boiler with supplementary combustion for heating.

The feed water is heated into superheated steam with a temperature of 300-350°C and a pressure of 2.45-3.25MPa, and enters the reboiler (8) of the carbon capture unit to heat the rich liquid, realizing the combination of the carbon capture unit and the waste heat utilization unit.

The recovery rate of carbon dioxide in the whole process is 90%, and the purity of separated carbon dioxide is 98%, reaching the required purity for direct industrial use. The energy consumption for capturing carbon dioxide in this method is about 3.4MJ/kgCO ₂ , which is a relatively low level among chemical absorption methods.

The advantages of the carbon capture device and method for heating furnace tail gas utilizing the waste heat of the slab storehouse of the present invention are obvious:

1. Using the exhaust gas of the heating furnace as the basic heat source, the waste heat resource is rationally used, and the energy consumption of carbon dioxide regeneration is significantly reduced. Compared with the method of pumping low-pressure cylinder steam for decarbonization in power plants, the solution proposed in this patent will neither affect product production nor increase additional carbon dioxide emissions during the decarbonization process. The capture of carbon dioxide reduces the burden of energy consumption for iron and steel enterprises. The overall recovery rate of carbon dioxide reaches over 90%, the annual capture capacity is 100,000 tons, and the purity of separated carbon dioxide reaches over 98%, which can be directly used in enhanced oil recovery (EOR).

2. Use the waste heat of the slab warehouse to further heat the waste gas to realize the cascade utilization of energy. According to preliminary statistics, the cooling capacity of the slab warehouse is about 400t/h, and the surface temperature of the continuous casting slab is about 1200°C. The slab warehouse is divided into three sub-stores, high, middle and low. Heating and cooling the billet at the same time to realize the rational use of energy.

3. Use waste heat boiler with supplementary combustion to ensure continuity of heat supply. When intermittent furnace temperature changes in iron and steel enterprises lead to fluctuations in waste heat, a small amount of fuel can be supplemented, such as blast furnace gas, to ensure that the heat supplied to the carbon capture unit remains constant. The supplementary fuel accounts for only a small part of the overall heat of the waste heat boiler, and the carbon dioxide produced by combustion only accounts for about 5% of the captured amount.

The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make many modifications and changes according to the concept of the present invention without creative efforts. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning or limited experiments on the basis of the prior art shall be within the scope of protection defined by the claims.

Claims (10)

1. the heating furnace exhaust gas carbon capturing device of a kind of utilization slab storehouse waste heat, it is characterised in that including carbon capture unit and remaining Heat utilization unit, wherein, carbon capture unit includes blower fan, absorption tower, desorber, lean pump, rich solution pump, reflux pump, lean rich solution Heat exchanger, reboiler and condenser；UTILIZATION OF VESIDUAL HEAT IN unit include heating furnace, slab storehouse, waste heat boiler, cooling tower, feed pump and Chimney；

The absorption tower has first end and the second end, and the second end includes Part I and Part II, described Blower fan is connected with the Part I of the second end on the absorption tower, and the Part II of the second end on the absorption tower passes through The rich solution pump is connected with the poor rich liquid heat exchanger, and the first end on the absorption tower is lean with described by the lean pump Rich solution heat exchanger is connected, and the poor rich liquid heat exchanger is connected with the top of the desorber and bottom respectively, the desorbing The top of tower is connected with the condenser and the reflux pump respectively, and forms a condensing reflux loop；The desorber Bottom is connected with the waste heat boiler and the cooling tower respectively by the reboiler；

The waste heat boiler connects the chimney；The cooling tower is connected to the waste heat boiler by the feed pump；Described Heating furnace is connected with the waste heat boiler by the slab storehouse.

2. the heating furnace exhaust gas carbon capturing device of utilization slab storehouse waste heat as claimed in claim 1, it is characterised in that described remaining Heat boiler is the waste heat boiler with afterburning.

3. the heating furnace exhaust gas carbon capturing device of utilization slab storehouse waste heat as claimed in claim 2, it is characterised in that the band The waste heat boiler of afterburning includes economizer, evaporating heating surface, superheater and drum.

4. the heating furnace exhaust gas carbon capturing device of utilization slab storehouse waste heat as claimed in claim 2, it is characterised in that the suction Receipts tower is plate column, and the number of plates is 10-15 level.

5. a kind of heating furnace exhaust gas carbon trapping side of the utilization slab storehouse waste heat for being used as any device in Claims 1 to 4 Method, it is characterised in that including carbon trapping circulation and UTILIZATION OF VESIDUAL HEAT IN circulation；

Wherein the carbon trapping circulation step is：Heating furnace exhaust gas are by the blower fan from the suction after desulphurization denitration dedusting The Part I for receiving tower is entered, and in the absorption tower, chemical reaction occurs, and flue gas is discharged from the first end on the absorption tower； Rich solution flows out into the poor rich liquid heat exchanger from the Part II on the absorption tower, enters the desorber after heating；Institute The bottom for stating desorber is heated by the reboiler, and the carbon dioxide of spilling is discharged and sequentially enter from the desorber top The condenser and the reflux pump；Lean solution after reboiler heating enters the poor rich liquid heat exchanger, by described Lean pump pressurization enters the absorption tower；

The UTILIZATION OF VESIDUAL HEAT IN circulation step is：The heating furnace exhaust gas are entered and are further heated up in the slab storehouse, then are entered Enter the heating of the waste heat boiler with the afterburning feedwater, vapor enters the reboiler and heat provided for the carbon capture unit.

6. the heating furnace exhaust gas carbon capture method of utilization slab storehouse waste heat as claimed in claim 5, it is characterised in that described plus There is chemical reaction with absorbent adverse current in the absorption tower in hot furnace exhaust gas.

7. the heating furnace exhaust gas carbon capture method of utilization slab storehouse waste heat as claimed in claim 5, it is characterised in that the plate Base storehouse include high temperature, in gentle three points of storehouses of low temperature, the heating furnace exhaust gas sequentially pass through low temperature, middle temperature, three points of storehouses of high temperature, So that tail gas is heated.

8. the heating furnace exhaust gas carbon capture method of utilization slab storehouse waste heat as claimed in claim 5, it is characterised in that described remaining Heat utilization circulation also includes water circulation system, and the water circulation step is：Vapor in the reboiler is by the cooling Tower cooler becomes aqueous water, then is heated by the feed pump pressurization entrance waste heat boiler with afterburning.

9. the heating furnace exhaust gas carbon capture method of utilization slab storehouse waste heat as claimed in claim 6, it is characterised in that the suction Receipts agent is ethanolamine.

10. the heating furnace exhaust gas carbon capture method of utilization slab storehouse waste heat as claimed in claim 9, it is characterised in that described The concentration of ethanolamine is 26.5%-32%.