CN110813007A - Waste gas waste heat recovery and purification process of mixed gas heating system - Google Patents

Abstract

The invention relates to a waste gas waste heat recovery and purification process of a mixed gas heating system, wherein coke oven waste flue gas generated in the heating process of a coke oven is sent into a dry quenching furnace to cool high-temperature coke after heat exchange, temperature reduction and carbon dioxide removal treatment; dry quenching fire grateThe discharged waste flue gas enters a primary dust remover, a desulfurizer is sprayed into the primary dust remover, and SO in the waste flue gas is removed₂Removing; the desulfurized waste flue gas enters a waste heat boiler to recover heat carried by the waste flue gas, and the outlet temperature of the waste flue gas is controlled by the waste heat boiler, so that the waste flue gas discharged after heat exchange directly enters an SCR denitration device for denitration; and the waste flue gas after denitration is sent to a chimney for discharging after heat exchange, temperature reduction and secondary dust removal. The invention can realize the recovery of the waste heat of the red coke and the waste heat of the waste flue gas of the coke oven, and simultaneously, can complete the purification of the waste flue gas of the coke oven, so that the flue gas emission meets the national standard, the air pollution is reduced, the greenhouse gas emission is reduced, and the quality of the coke is ensured.

Description

A kind of waste heat recovery and purification process of mixed gas heating system waste gas

technical field

The invention relates to the technical field of coking waste heat recovery and flue gas purification, in particular to a waste heat recovery and purification process of waste gas of a mixed gas heating system.

Background technique

In the coke oven production process, the gas (coke oven gas or mixed gas) is burned in the combustion chamber while supplying heat to the carbonization chamber. -300℃, called coke oven exhaust gas. In coke oven production, in addition to the N ₂ carried in the air, the CO ₂ and H ₂ O generated after combustion, the waste flue gas generated by the mixed gas heating system with blast furnace gas as the main blending coke oven gas also contains a small amount of residual gas. O ₂ and SO ₂ , NO _X generated in the combustion process, SO ₂ contained in coke oven flue gas is one of the important pollution sources of the atmosphere, and NO _X is one of the sources of photochemical fog pollution, both of which cause pollution to the atmospheric environment. and very dangerous.

"Coking Chemical Industry Pollutant Emission Standards" (GB16171-2012) clearly stipulates that from January 1, 2015, the emission of sulfur dioxide in coke oven flue gas shall not exceed 50mg/m ³ and the emission of nitrogen oxides shall not exceed 500mg/m ³ However, with the increasing emphasis on ecological environmental protection in China, more and more places and industries have begun to implement more stringent special emission standards. basic requirements. At present, the purification of coke oven waste flue gas mostly adopts the process of sodium carbonate desulfurization + SCR denitration. Selective Catalytic Reduction (SCR) is the most mature flue gas denitrification technology. It uses reducing agents (NH3, urea) to selectively react with NOx under the action of metal catalysts to generate _N2 and _H2O , so that The flue gas meets the emission requirements. Mainstream SCR reactors are further divided into medium temperature (260℃～380℃) catalytic denitrification and low temperature (120℃～300℃) catalytic denitrification. Before the coke oven exhaust flue gas enters the desulfurization and denitrification device, the conveying distance is generally long, and the pipeline heat dissipation is large, which leads to obvious cooling. Therefore, it is necessary to configure a flue gas heating system to ensure that the temperature of the coke oven exhaust flue gas meets the conditions of SCR denitration reaction.

The CDQ process is a high-efficiency technology that uses inert gas to continuously recover and utilize the sensible heat of high temperature (950-1100℃) red coke. It mainly consists of CDQ furnace, circulating fan, primary dust collector, boiler, secondary Dust collector and other equipment and pipeline connections. In the process of coke quenching, the red coke enters from the top of the CDQ furnace and flows in the opposite direction with the circulating cooling gas to complete the convective heat exchange process. The cooled solid particles are discharged from the bottom of the shaft furnace, and the high temperature gas that fully absorbs the sensible heat of the red coke is passed through the CDQ. The exhaust port of the furnace enters the subsequent device for waste heat utilization, such as steam generation or power generation. This process has the advantages of high waste heat recovery rate and environmentally friendly operation and is widely used. However, in the process of CDQ, due to the burning of residual volatiles in red coke and the burning loss of part of coke powder, the circulating gas contains a certain amount of sulfur dioxide, which accumulates continuously during operation, resulting in sulfur dioxide in the circulating gas released after the fan. The content is relatively high, so it is required to carry out desulfurization and purification treatment on the circulating gas of the dissipated part before it is discharged into the atmosphere. For the desulfurization and purification treatment of this part of the released circulating gas, the current methods are different. Some of them have a separate desulfurization and purification device, but they need to invest in a complete system with complete facilities and increase a certain amount of investment. It is also introduced into the coke oven waste flue gas desulfurization and denitrification system, but because this part of the released gas contains a high concentration of dust, it is necessary to add necessary dust removal facilities, and at the same time, it will reduce the temperature of the coke oven waste flue gas to a certain extent. This will adversely affect the operation of the coke oven waste flue gas desulfurization and denitrification system.

In order to effectively recover the waste heat of red coke and coke oven waste flue gas, and at the same time complete the purification of coke oven waste flue gas, the waste flue gas waste heat recovery and desulfurization and denitration purification process and dry quenching process can be adopted after heating and burning the mixed gas. The coke process is integrated to form a process system, but since the volume of CO ₂ generated by combustion in the waste flue gas accounts for about 20% of the exhaust gas, when the CO ₂ in the waste flue gas contacts the hot coke in the CDQ furnace , it will have a certain degree of carbon melting reaction with coke to generate CO, which not only increases the content of combustible components in the flue gas, but also brings certain safety hazards to the operation of the system. The amount of coke causes the "burning loss" of the coke and the reduction of the quality of the coke. Therefore, it is necessary to take necessary measures to solve the above problems.

SUMMARY OF THE INVENTION

The invention provides a waste heat recovery and purification process of the waste gas of a mixed gas heating system. The waste heat recovery and desulfurization and denitration purification process of the waste flue gas generated after the heating and combustion of the mixed gas is organically integrated with the coke dry quenching process. The carbon dioxide is removed to realize the recovery of the waste heat of the red coke and the waste heat of the coke oven waste flue gas, and at the same time complete the purification of the coke oven waste flue gas, so that the flue gas emissions meet the national standards, reduce air pollution, reduce greenhouse gas emissions, and ensure coke coke emissions. the quality of.

In order to achieve the above object, the present invention adopts the following technical solutions to realize:

A process for recovering and purifying waste heat from waste gas of a mixed gas heating system. The coke oven waste flue gas produced in the coke oven heating process is sent to a dry quenching furnace after heat exchange, cooling, and decarbonation treatment to cool high-temperature coke; The waste flue gas enters the primary dust collector, and the desulfurizer is sprayed into the primary dust collector to remove SO ₂ in the waste flue gas; the waste flue gas after desulfurization enters the waste heat boiler to recover the heat carried by it, and passes through the waste heat boiler. The outlet temperature of the waste flue gas is controlled, so that the waste flue gas discharged after heat exchange directly enters the SCR denitrification device for denitration; the waste flue gas after denitration is cooled by heat exchange and secondary dust is sent to the chimney for discharge.

A waste heat recovery and purification process of waste gas of a mixed gas heating system, specifically comprising the following steps:

1) Through the coke oven waste flue gas introduction system, the coke oven waste flue gas generated during the coke oven heating process is led out from the coke oven general flue and enters the first heat exchanger;

2) In heat exchanger 1, the coke oven exhaust gas with a temperature of 200℃～300℃ is cooled to below 70℃ by the demineralized water from the waste heat boiler through indirect heat exchange, and part of the heat carried by the coke oven exhaust gas After being recovered by demineralized water, it is sent to the waste heat boiler, and the coke oven waste flue gas after heat exchange enters the decarbonation device;

3) In the decarbonation device, the carbon dioxide gas in the waste flue gas is separated and recovered, and the remaining waste flue gas enters the CD quenching furnace from the gas supply device at the lower part of the CD quenching furnace;

4) In the CDQ furnace, the coke oven waste flue gas is in reverse contact with the high-temperature coke, and the waste flue gas after absorbing the coke heat is discharged from the upper section of the CDQ furnace and then enters the primary dust collector, and the cooled coke passes through the lower part of the CDQ furnace. coke system discharge;

1) 5) The dry desulfurization device uses NaHCO ₃ as the desulfurizing agent, and injects NaHCO ₃ into the primary dust collector through the NaHCO ₃ conveying pipeline. In the primary dust collector, NaHCO ₃ fully contacts and reacts with SO ₂ in the exhaust gas. , generate NaHSO ₃ , Na ₂ SO ₃ , and realize the removal of SO ₂ in the waste flue gas; the generated NaHSO ₃ , Na ₂ SO ₃ and the coke powder carried by the waste flue gas are removed from the primary dust collector by inertial collision and sedimentation. separation from flue gas;

6) The waste flue gas after a dust removal enters the waste heat boiler, and the waste heat boiler uses the heat carried by the waste flue gas to generate high-temperature and high-pressure steam for power generation or equipment driving, so as to realize the recovery and utilization of coking waste heat; the waste heat after the heat recovery by the waste heat boiler The flue gas directly enters the SCR denitration device through the pipeline for denitration treatment;

7) The waste flue gas after being denitrified by the SCR denitration device enters the second heat exchanger for cooling treatment; in the second heat exchanger, the waste flue gas is cooled by the demineralized water from the waste heat boiler through indirect heat exchange, and the waste flue gas is cooled by the demineralized water from the waste heat boiler. Part of the carried heat is recovered by the demineralized water and sent to the waste heat boiler, and the cooled waste flue gas enters the secondary dust collector;

8) In the secondary dust collector, the solid particulate matter and dust carried in the waste flue gas are removed by filtering and dust removal, and the captured particulate matter and dust are recovered by the dust collection device at the lower part of the secondary dust collector and then discharged for treatment; The filtered and dedusted waste flue gas is transported by the induced draft fan and sent to the chimney for discharge.

The flue gas outlet temperature of the waste heat boiler is controlled between 300°C and 400°C.

The primary dust collector is an inertial gravity dust collector.

The secondary dust collector is a bag filter.

The carbon dioxide removal device adopts a physical and chemical solvent absorption method, a solid adsorption method or a membrane gas separation method to separate and recover carbon dioxide.

Compared with the prior art, the beneficial effects of the present invention are:

1) The present invention uses coke oven waste flue gas as a heat exchange medium to cool high-temperature coke, and organically integrates the waste heat recovery of the two waste heat resources of high temperature red coke and coke oven waste flue gas in the coking production process into a waste heat recovery system. , while improving the heat quality of waste heat recovery from coke oven waste flue gas and increasing the utilization capacity of CDQ waste heat, the desulfurization and denitration purification treatment of coke oven waste flue gas is realized, and the related flue gas treatment equipment and power such as dust removal facilities and fans are reduced. The configuration of facilities, the overall process layout is simple, the land occupation is small, and the one-time construction cost and operation cost are low;

2) The carbon dioxide gas in the coke oven exhaust flue gas is recovered by the decarbonation device to reduce the coke loss caused by the carbon-dissolving reaction between the carbon dioxide in the exhaust gas and the red coke, and at the same time reduce the emission of greenhouse gases and protect the environment.

3) Use high-temperature coke coke oven waste flue gas for heating, and by controlling the temperature of coke oven waste flue gas behind the waste heat boiler, a flue gas environment suitable for the catalytic reaction of medium-temperature SCR denitration is formed, and there is no need to add additional heating systems, reducing denitrification. Catalyst cost, improved denitration efficiency;

4) After SCR denitration, a bag-type dust removal device is used to purify the waste flue gas. The dust removal efficiency is high. The dust concentration of the secondary dust collector is below 10mg/ ^m3 , so that the induced draft fan installed after the secondary dust collector does not need to be configured. The special wear-resistant measures, compared with the traditional CDQ circulating fan, can significantly reduce the replacement and maintenance costs of the fan, reduce the failure rate, and improve the stability of CDQ continuous operation;

5) The present invention performs desulfurization and denitrification purification treatment of coke oven waste flue gas. Compared with the existing CDQ process, the present invention does not need to consider the desulfurization problem of releasing circulating gas, and the gas discharged into the chimney can fully meet the requirements of environmental protection standards.

Description of drawings

FIG. 1 is a schematic flow chart of the waste heat recovery and purification process of waste gas of a mixed gas heating system according to the present invention.

In the picture: 1. CDQ furnace 2. Dry desulfurization device 3. Primary dust collector 4. Waste heat boiler 5. SCR denitration device 6. Secondary dust collector 7. Dust collection device 8. Heat exchanger II 9. Induced draft fan 10 . Heat exchanger one 11. Coke oven general flue 12. Chimney 13. Flue flap 14. High temperature coke 15. Decarbonation device

Detailed ways

The specific embodiments of the present invention will be further described below in conjunction with the accompanying drawings:

As shown in Figure 1, the waste heat recovery and purification process of the waste gas of a mixed gas heating system according to the present invention, the coke oven waste gas produced in the coke oven heating process is sent to the CDQ 1 after heat exchange cooling and decarbonation treatment , to cool the high temperature coke 14; the waste flue gas discharged from the CDQ furnace 1 enters the primary dust collector 3, and a desulfurizer is sprayed into the primary dust collector 3 to remove SO ₂ in the waste flue gas; the waste smoke after desulfurization The gas enters the waste heat boiler 4 to recover the heat carried by it, and the outlet temperature of the waste flue gas is controlled by the waste heat boiler 4, so that the waste flue gas discharged after heat exchange directly enters the SCR denitration device 5 for denitrification; The gas is then sent to the chimney 12 for external discharge after being cooled by heat exchange and secondary dust removal.

A waste heat recovery and purification process of waste gas of a mixed gas heating system, specifically comprising the following steps:

1) Through the coke oven waste flue gas introduction system, the coke oven waste flue gas generated during the coke oven heating process is led out from the coke oven general flue 11 and enters the heat exchanger one 10;

2) In the heat exchanger 10, the coke oven waste flue gas with a temperature of 200°C to 300°C is cooled to below 70°C by the demineralized water from the waste heat boiler 4 through indirect heat exchange. Part of the heat is recovered by the demineralized water and sent to the waste heat boiler 4, and the coke oven waste flue gas after heat exchange enters the decarbonation device 15;

3) In the decarbonation device 15, the carbon dioxide gas in the waste flue gas is separated and recovered, and the remaining waste flue gas enters the CDQ furnace 1 from the gas supply device at the lower part of the CDQ furnace 1;

4) In the CDQ furnace 1, the coke oven waste flue gas is in reverse contact with the high-temperature coke 14, and the waste flue gas after absorbing the coke heat is discharged from the upper section of the CDQ furnace 1 and then enters the primary dust collector 3, and the cooled coke passes through the CDQ. The coke removal system at the lower part of furnace 1 is discharged;

2) 5) The dry desulfurization device 2 uses NaHCO ₃ as the desulfurizing agent, and injects NaHCO ₃ into the primary dust collector 3 through the NaHCO ₃ conveying pipeline. In the primary dust collector 3, NaHCO ₃ and SO ₂ in the waste flue gas are sufficient. The contact reacts to generate NaHSO ₃ , Na ₂ SO ₃ to realize the removal of SO ₂ in the waste flue gas; the generated NaHSO ₃ , Na ₂ SO ₃ and the coke powder carried by the waste flue gas pass through inertial collision in the primary dust collector 3 and sedimentation separation from flue gas;

6) The waste flue gas after the first dedusting enters the waste heat boiler 4, and the waste heat boiler 4 uses the heat carried by the waste flue gas to generate high-temperature and high-pressure steam for power generation or equipment drive, so as to realize the recovery and utilization of the coking waste heat; the heat is recovered through the waste heat boiler 4 The waste flue gas directly enters the SCR denitration device 5 through the pipeline for denitration treatment;

7) The waste flue gas after being denitrified by the SCR denitration device 5 enters the heat exchanger 2 8 for cooling treatment; in the heat exchanger 2 8, the waste flue gas is cooled by the demineralized water from the waste heat boiler 4 through indirect heat exchange , part of the heat carried by the waste flue gas is recovered by the desalinated water and sent to the waste heat boiler 4, and the cooled waste flue gas enters the secondary dust collector 6;

8) In the secondary dust collector 6, the solid particles and dust carried in the waste flue gas are removed by filtering and dust removal. The captured particles and dust are recovered by the dust collection device 7 at the lower part of the secondary dust collector 6. Exhaust and treatment; the waste flue gas after filtering and dust removal is transported by the induced draft fan 9 and sent to the chimney 12 for discharge.

The flue gas outlet temperature of the waste heat boiler 4 is controlled between 300°C and 400°C.

The primary dust collector 3 is an inertial gravity dust collector.

The secondary dust collector 6 is a bag filter.

The carbon dioxide removal device 15 adopts a physical-chemical solvent absorption method, a solid adsorption method or a membrane gas separation method to separate and recover carbon dioxide.

As shown in Figure 1, it is a specific structure of the waste heat recovery and purification process of the mixed gas heating waste gas according to the present invention, including a coke oven waste flue gas introduction system, a heat exchanger 10, a decarbonation device 15, and a dry quenching furnace. 1. Dry desulfurization device 2, primary dust collector 3, waste heat boiler 4, SCR denitration device 5, heat exchanger 2 8, secondary dust collector 6, induced draft fan 9 and chimney 12; the coke oven waste flue gas introduction system Including the coke oven general flue 11 and the flue flap 13, the coke oven exhaust gas outlet is arranged on the coke oven general flue 11, and the flue flap 13 is arranged between the coke oven exhaust flue gas outlet and the chimney 12 of the coke oven On the general flue 11; the coke oven waste gas outlet is connected to the waste flue gas inlet of heat exchanger one 10 through the coke oven waste flue gas pipeline, and the waste flue gas outlet of heat exchanger one 10 is connected to the waste flue gas inlet of the decarbonation device 15. , the waste flue gas outlet of the decarbonation device 15 is connected to the gas supply device at the lower part of the CDQ 1; the waste flue gas outlet at the upper part of the CDQ 1 is connected to the primary dust collector 3, the waste heat boiler 4, and the SCR denitration sequentially through the waste flue gas conveying pipeline. Device 5, heat exchanger 2 8, secondary dust collector 6, induced draft fan 9, chimney 12; along the flow direction of waste flue gas, a NaHCO ₃ injection port is set on the waste flue gas conveying pipeline upstream of the primary precipitator 3, through the NaHCO ₃ The injection pipeline is connected to the NaHCO ₃ supply device, and the NaHCO ₃ injection pipeline and the NaHCO ₃ supply device together form the dry desulfurization device 2 .

The first heat exchanger 10 is provided with a demineralized water inlet and a demineralized water outlet, and the demineralized water inlet and the demineralized water outlet are respectively connected to the economizer of the waste heat boiler 4 through a demineralized water pipeline.

The second heat exchanger 8 is provided with a waste flue gas inlet, a waste flue gas outlet, a demineralized water inlet and a demineralized water outlet. Connect the waste flue gas conveying pipeline downstream of the second heat exchanger 8; the demineralized water inlet and the demineralized water outlet are respectively connected to the economizer of the waste heat boiler 4 through the demineralized water pipeline.

The coke loading device, the coke discharging device matched with the CDQ furnace 1 in the present invention, and the primary dust collector 3, the secondary dust collector 6, the dry desulfurization device 2, the SCR denitration device 5, the carbon dioxide removal device The raw material supply facilities, powder discharge facilities, denitration catalyst regeneration facilities and other configurations matched with equipment such as 15 are all existing mature technologies, which are well known to those skilled in the art, and will not be repeated here.

The above description is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited to this. The equivalent replacement or change of the inventive concept thereof shall be included within the protection scope of the present invention.

Claims (6)

1. A waste gas waste heat recovery and purification process of a mixed gas heating system is characterized in that coke oven waste flue gas generated in the heating process of a coke oven is sent into a dry quenching furnace after heat exchange, temperature reduction and carbon dioxide removal treatment, and high-temperature coke is cooled; the waste flue gas discharged from the dry quenching furnace enters a primary dust remover, a desulfurizer is sprayed into the primary dust remover, and SO in the waste flue gas is removed₂Removing; the desulfurized waste flue gas enters a waste heat boiler to recover heat carried by the waste flue gas, and the outlet temperature of the waste flue gas is controlled by the waste heat boiler to ensure that the waste flue gas is discharged after heat exchangeDirectly feeding the waste flue gas into an SCR denitration device for denitration; and the waste flue gas after denitration is sent to a chimney for discharging after heat exchange, temperature reduction and secondary dust removal.

2. The waste gas waste heat recovery and purification process of the mixed gas heating system according to claim 1, which comprises the following steps:

1) the coke oven waste flue gas generated in the heating process of the coke oven is led out from the coke oven main flue through the coke oven waste flue gas leading-in system and enters the heat exchanger I;

2) in the heat exchanger I, coke oven waste flue gas with the temperature of 200-300 ℃ is cooled to below 70 ℃ by desalted water from a waste heat boiler in an indirect heat exchange mode, part of heat carried by the coke oven waste flue gas is recycled by the desalted water and then is sent to the waste heat boiler, and the coke oven waste flue gas after heat exchange enters a carbon dioxide removal device;

3) in the carbon dioxide removing device, carbon dioxide gas in the waste flue gas is separated and recovered, and the residual waste flue gas enters the dry quenching furnace from a gas supply device at the lower part of the dry quenching furnace;

4) in a dry quenching furnace, coke oven waste flue gas is in reverse contact with high-temperature coke, the waste flue gas absorbing coke heat is discharged from the upper section of the dry quenching furnace and then enters a primary dust remover, and cooled coke is discharged through a coke discharging system at the lower part of the dry quenching furnace;

5) the dry desulfurization device adopts NaHCO₃As a desulfurizing agent, by NaHCO₃The conveying pipeline sprays NaHCO into the primary dust remover₃In a primary precipitator, NaHCO₃With SO in waste flue gas₂Fully contact to react to generate NaHSO₃、Na₂SO₃Realizing SO in the waste flue gas₂Removing; produced NaHSO₃、Na₂SO₃And separating coke powder carried by the waste flue gas from the flue gas through inertial collision and sedimentation in the primary dust remover;

6) the waste flue gas after primary dust removal enters a waste heat boiler, and the waste heat boiler generates high-temperature and high-pressure steam for power generation or equipment driving by using heat carried by the waste flue gas, so that the recycling of coking waste heat is realized; waste flue gas after heat recovery by the waste heat boiler directly enters an SCR denitration device through a pipeline for denitration treatment;

7) the waste flue gas subjected to denitration treatment by the SCR denitration device enters a heat exchanger II for cooling treatment; in the second heat exchanger, the waste flue gas is cooled by the desalted water from the waste heat boiler in an indirect heat exchange mode, part of heat carried by the waste flue gas is recycled by the desalted water and then is sent to the waste heat boiler, and the cooled waste flue gas enters a secondary dust remover;

8) in the secondary dust remover, solid particles and dust carried in the waste flue gas are removed by adopting a filtering and dust removing mode, and the collected particles and dust are recycled by a dust collecting device at the lower part of the secondary dust remover and then are discharged for treatment; and conveying the filtered and dedusted waste flue gas to a chimney through a draught fan for discharging.

3. The waste gas waste heat recovery and purification process of the mixed gas heating system according to claim 1 or 2, wherein the temperature of the flue gas outlet of the waste heat boiler is controlled between 300 ℃ and 400 ℃.

4. The waste gas heat recovery and purification process of the mixed gas heating system according to claim 1 or 2, wherein the primary dust remover is an inertial gravity dust remover.

5. The waste gas heat recovery and purification process of the mixed gas heating system according to claim 1 or 2, wherein the secondary dust remover is a bag type dust remover.

6. The waste gas heat recovery and purification process of the mixed gas heating system according to claim 1 or 2, wherein the carbon dioxide removal device adopts a physical and chemical solvent absorption method, a solid adsorption method or a membrane gas separation method to separate and recover carbon dioxide.

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