CN110437849B - Dry quenching and coke oven flue gas combined purification process and system - Google Patents

Abstract

The invention relates to a dry quenching and coke oven flue gas combined purification process and a system, wherein the system comprises a coke oven waste flue gas introduction system, a first heat exchanger, a dry quenching furnace, a dry desulfurization device, a primary dust remover, a waste heat boiler, an SCR denitration device, a second heat exchanger, a secondary dust remover, an induced draft fan and a chimney; according to the invention, the coke oven waste flue gas waste heat recovery and desulfurization and denitrification purification process and the dry quenching process are organically combined, and the purification of the coke oven waste flue gas is completed while the red coke waste heat and the coke oven waste flue gas waste heat are recovered, so that the flue gas emission meets the national standard, and the atmospheric pollution is reduced.

Description

Coke dry quenching and coke oven flue gas combined purification process and system

Technical Field

The invention relates to the technical field of coking waste heat recovery and flue gas purification, and in particular to a coke dry quenching and coke oven flue gas combined purification process and system.

Background technique

In the coke oven production process, coal gas (blast furnace gas, coke oven gas or mixed gas) burns in the combustion chamber and supplies heat to the carbonization chamber at the same time. The high-temperature flue gas generated by the combustion is discharged after heat exchange in the heat storage chamber. At this time, the flue gas temperature reaches 200-300℃, which is called coke oven waste flue gas. In addition to _N2 carried in the air, _CO2 and _H2O generated after combustion, the coke oven waste flue gas also contains a small amount of residual _O2 and _SO2 and _NOX generated during the combustion process. _SO2 contained in the coke oven waste flue gas is one of the important sources of atmospheric pollution, and _NOX is one of the sources of photochemical smog pollution. The pollution and harm caused by the two to the atmospheric environment are very serious.

The Pollutant Emission Standard for Coking Chemical Industry (GB16171-2012) clearly stipulates that from January 1, 2015, the sulfur dioxide emission in the flue gas of coke ovens shall not exceed 50mg/ ^m3 , and the nitrogen oxide emission shall not exceed 500mg/ ^m3 . As China attaches more importance to ecological and environmental protection, more and more places and industries have begun to implement more stringent special emission standards. Comprehensive treatment of pollutants in coke oven waste flue gas has become a basic requirement for coking production enterprises. At present, the purification of coke oven waste flue gas mostly adopts the process of sodium carbonate desulfurization + SCR denitrification. Selective catalytic reduction technology (SCR) is the most mature flue gas denitrification technology at present. 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. The mainstream SCR reactor is divided into medium temperature (260℃～380℃) catalytic denitrification and low temperature (120℃～300℃) catalytic denitrification. Before the coke oven waste gas enters the desulfurization and denitrification device, the transportation distance is generally long, and the pipeline heat dissipation is large, resulting in significant temperature drop. Therefore, a flue gas heating system is required to ensure that the temperature of the coke oven waste gas meets the conditions for the SCR denitrification reaction.

The dry coke quenching process is a highly efficient technology that uses inert gas to continuously recover and utilize the sensible heat of high-temperature (950-1100℃) red coke. It is mainly composed of dry quenching furnace, circulating fan, primary dust collector, boiler, secondary dust collector and other equipment and pipeline connections. During the quenching process, the red coke enters from the top of the dry quenching furnace and flows in the opposite direction with the circulating cooling gas to complete the convection heat exchange process. The cooled solid particles are discharged from the bottom of the vertical furnace. The high-temperature gas that has fully absorbed the sensible heat of the red coke enters the subsequent device through the exhaust port of the dry quenching furnace for waste heat utilization, such as generating steam or power generation. This process has the advantages of high waste heat recovery rate and environmentally friendly operation and is widely used. However, during the dry quenching process, due to the combustion of residual volatiles in the red coke and the burning of part of the coke powder, a certain amount of sulfur dioxide is contained in the circulating gas, which accumulates continuously during operation, resulting in a high sulfur dioxide content in the circulating gas released after the fan. Therefore, it is required that the released part of the circulating gas be desulfurized and purified before being discharged into the atmosphere. There are different methods for desulfurization and purification of this part of the released circulating gas. Some people set up a separate desulfurization and purification device for it, but it requires a complete system with complete facilities, which increases a certain amount of investment. Some people introduce it into the desulfurization and denitrification system of coke oven waste gas, but because this part of the released gas contains a high concentration of dust, it is necessary to add necessary dust removal facilities, and it will also reduce the temperature of the coke oven waste gas to a certain extent, thus causing adverse effects on the operation of the coke oven waste gas desulfurization and denitrification system.

Summary of the invention

The present invention provides a combined coke dry quenching and coke oven flue gas purification process and system, which organically integrates the coke oven waste flue gas waste heat recovery and desulfurization and denitrification purification process with the coke dry quenching process, while realizing the recovery of red coke waste heat and coke oven waste flue gas waste heat, completes the purification of coke oven waste flue gas, makes the flue gas emission meet the national standards, and reduces air pollution.

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

In the combined coke dry quenching and coke oven flue gas purification process, the coke oven waste flue gas generated during the coke oven heating process is sent to the dry quenching furnace after heat exchange and cooling, and the high-temperature coke is cooled by heat exchange. The waste flue gas discharged from the dry quenching furnace is dedusted by a primary dust collector, and the desulfurizer NaHCO ₃ is sprayed into the primary dust collector at the same time. The desulfurized waste flue gas enters the waste heat boiler to recover heat, and the waste flue gas outlet temperature is controlled by the waste heat boiler, so that the waste flue gas discharged after heat exchange directly enters the SCR denitrification device for SCR denitrification catalytic reaction; the denitrified waste flue gas is then sent to the chimney for discharge after heat exchange and cooling and secondary dust removal.

The combined coke dry quenching and coke oven flue gas purification process specifically includes the following steps:

1) The coke oven waste flue gas generated during the coke oven heating process is introduced from the coke oven main flue through the coke oven waste flue gas introduction system and enters the heat exchanger 1;

2) In the heat exchanger 1, the coke oven waste gas with a temperature of 200℃ to 300℃ is cooled to below 150℃ by the demineralized water from the waste heat boiler through indirect heat exchange, and part of the heat carried by the coke oven waste gas is recovered and sent to the waste heat boiler. The coke oven waste gas after heat exchange enters the dry quenching furnace through the air supply device at the bottom of the dry quenching furnace;

3) In the CDQ furnace, the coke oven waste gas contacts the high-temperature coke in reverse. After absorbing the heat of the coke, the waste gas is discharged from the upper section of the CDQ furnace and enters the primary dust collector. The cooled coke is discharged through the coke discharge system at the lower section of the CDQ furnace.

4) The dry desulfurization device sprays NaHCO ₃ into the primary dust collector through the NaHCO ₃ injection pipeline. In the primary dust collector, NaHCO ₃ fully contacts and reacts with SO ₂ in the waste flue gas to generate NaHSO ₃ and Na ₂ SO ₃ , thereby removing SO ₂ from the waste flue gas. The generated NaHSO ₃ , Na ₂ SO ₃ and coke powder carried by the waste flue gas are separated from the flue gas in the primary dust collector through inertial collision and sedimentation.

5) The waste flue gas after primary dust removal enters the waste heat boiler, which uses the heat carried by the waste flue gas to generate high-temperature and high-pressure steam for power generation or equipment driving, thereby realizing the recovery and utilization of coking waste heat; the waste flue gas after heat recovery by the waste heat boiler directly enters the SCR denitrification device through a pipeline for denitrification treatment;

6) The waste flue gas after denitration treatment 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 desalted water from the waste heat boiler through indirect heat exchange, and part of the heat carried by the waste flue gas is recovered and sent to the waste heat boiler, and the cooled waste flue gas is sent to the secondary dust collector;

7) In the secondary dust collector, filtering and dust removal are used to remove solid particles and dust carried in the waste flue gas. The captured particles and dust are recovered by the dust collection device at the bottom of the secondary dust collector and then discharged externally. The waste flue gas after filtering and dust removal is sent to the chimney by the induced draft fan for discharge.

The coke dry quenching and coke oven flue gas combined purification system comprises a coke oven waste flue gas introduction system, a heat exchanger 1, a dry quenching furnace, a dry desulfurization device, a primary dust collector, a waste heat boiler, an SCR denitration device, a heat exchanger 2, a secondary dust collector, an induced draft fan and a chimney; the coke oven waste flue gas introduction system comprises a coke oven main flue and a flue flap, a coke oven waste gas introduction outlet is arranged on the coke oven main flue, and the flue flap is arranged on the coke oven main flue between the coke oven waste flue gas introduction outlet and the chimney; the coke oven waste gas introduction outlet is connected to the waste flue gas inlet of the heat exchanger 1 through a coke oven waste flue gas pipeline, and the waste flue gas outlet of the heat exchanger 1 is connected to the air supply device at the bottom of the dry quenching furnace; the waste flue gas outlet at the top of the dry quenching furnace is connected to the primary dust collector, the waste heat boiler, the SCR denitration device, the heat exchanger 2, the secondary dust collector, the induced draft fan and the chimney in sequence through a waste flue gas conveying pipeline; and along the flow direction of the waste flue gas, a NaHCO _{3 injection inlet is arranged on the waste flue gas conveying pipeline upstream of the primary dust collector, and NaHCO 3} is injected into the waste flue gas conveying pipeline upstream of the primary dust collector through the NaHCO 3 injection inlet. 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 constitute a dry desulfurization device.

The heat exchanger 1 is provided with a desalted water inlet and a desalted water outlet, and the desalted water inlet and the desalted water outlet are respectively connected to the economizer of the waste heat boiler through a desalted water pipeline.

The heat exchanger 2 is provided with a waste flue gas inlet, a waste flue gas outlet, a desalted water inlet and a desalted water outlet. The waste flue gas inlet is connected to the waste flue gas conveying pipeline upstream of the heat exchanger 2, and the waste flue gas outlet is connected to the waste flue gas conveying pipeline downstream of the heat exchanger 2; the desalted water inlet and the desalted water outlet are respectively connected to the economizer of the waste heat boiler through the desalted water pipeline.

The primary dust collector is a gravity dust collector.

The secondary dust collector is a bag dust collector.

Compared with the prior art, the present invention has the following beneficial effects:

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

2) Use high-temperature coke to heat the coke oven waste flue gas, and by controlling the temperature of the coke oven waste flue gas after the waste heat boiler, a flue gas environment suitable for the medium-temperature SCR denitrification catalytic reaction is formed, without the need to add an additional heating system, thereby reducing the cost of the denitrification catalyst and improving the denitrification efficiency;

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

4) Compared with the existing dry coke quenching process, the present invention does not need to consider the desulfurization of the released circulating gas while desulfurizing and denitrifying the waste flue gas from the coke oven, and the gas discharged into the chimney can fully meet the requirements of environmental protection standards.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic structural diagram of the coke dry quenching and coke oven flue gas combined purification system of the present invention.

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

Detailed ways

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

As shown in FIG1 , in the combined coke dry quenching and coke oven flue gas purification process of the present invention, the coke oven waste flue gas generated during the coke oven heating process is sent to the dry quenching furnace 1 after heat exchange and cooling, and the high-temperature coke 14 is heat exchanged and cooled. The waste flue gas discharged from the dry quenching furnace 1 is dedusted by the primary dust collector 3, and the desulfurizing agent NaHCO ₃ is sprayed into the primary dust collector 3 at the same time. The waste flue gas after desulfurization enters the waste heat boiler 4 to recover heat, and the waste flue gas outlet temperature 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 SCR denitration catalytic reaction; the waste flue gas after denitration is then sent to the chimney 12 for discharge after heat exchange and cooling and secondary dust removal.

The combined coke dry quenching and coke oven flue gas purification process specifically includes the following steps:

1) The coke oven waste flue gas generated during the coke oven heating process is introduced from the coke oven main flue 11 through the coke oven waste flue gas introduction system and enters the heat exchanger 10;

2) In the heat exchanger 10, the coke oven waste gas with a temperature of 200°C to 300°C is cooled to below 150°C by the demineralized water from the waste heat boiler 4 through indirect heat exchange, and part of the heat carried by the coke oven waste gas is recovered and sent to the waste heat boiler 4. The coke oven waste gas after heat exchange enters the dry quenching furnace 1 through the air supply device at the bottom of the dry quenching furnace 1;

3) In the CDQ furnace 1, the coke oven waste gas contacts the high-temperature coke 14 in reverse direction. After absorbing the heat of the coke, the waste gas is discharged from the upper section of the CDQ furnace 1 and enters the primary dust collector 3. The cooled coke is discharged through the coke discharge system at the lower section of the CDQ furnace 1.

4) The dry desulfurization device 2 injects NaHCO ₃ into the primary dust collector 3 through the NaHCO ₃ injection pipeline. In the primary dust collector 3, NaHCO ₃ fully contacts and reacts with SO ₂ in the waste flue gas to generate NaHSO ₃ and Na ₂ SO ₃ , thereby removing SO ₂ from the waste flue gas. The generated NaHSO ₃ , Na ₂ SO ₃ and coke powder carried by the waste flue gas are separated from the flue gas in the primary dust collector 3 by inertial collision and sedimentation.

5) The waste flue gas after primary dust removal enters the waste heat boiler 4, which uses the heat carried by the waste flue gas to generate high-temperature and high-pressure steam for power generation or equipment driving, thereby realizing the recovery and utilization of coking waste heat; the waste flue gas after heat recovery by the waste heat boiler 4 directly enters the SCR denitration device 5 through a pipeline for denitration treatment;

6) The waste flue gas after denitration treatment 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 desalted water from the waste heat boiler 4 by indirect heat exchange, and part of the heat carried by the waste flue gas is recovered and sent to the waste heat boiler 4, and the cooled waste flue gas is sent to the secondary dust collector 6;

7) In the secondary dust collector 6, filtering and dust removal are used to remove solid particles and dust carried in the waste flue gas. The captured particles and dust are recovered by the dust collection device 7 at the bottom of the secondary dust collector 6 and then discharged externally. The waste flue gas after filtering and dust removal is sent to the chimney 12 by the induced draft fan 9 for discharge.

The coke dry quenching and coke oven flue gas combined purification system comprises a coke oven waste flue gas introduction system, a heat exchanger 10, a dry quenching furnace 1, a dry desulfurization device 2, a primary dust collector 3, a waste heat boiler 4, an SCR denitrification device 5, a heat exchanger 8, a secondary dust collector 6, an induced draft fan 9 and a chimney 12; the coke oven waste flue gas introduction system comprises a coke oven main flue 11 and a flue flap 13, a coke oven waste gas introduction outlet is arranged on the coke oven main flue 11, and the flue flap 13 is arranged on the coke oven main flue between the coke oven waste flue gas introduction outlet and the chimney 12 The exhaust gas outlet of the coke oven is connected to the exhaust gas inlet of the heat exchanger 10 through the exhaust gas pipeline of the coke oven, and the exhaust gas outlet of the heat exchanger 10 is connected to the air supply device at the bottom of the dry quenching furnace 1; the exhaust gas outlet of the upper part of the dry quenching furnace 1 is connected to the primary dust collector 3, the waste heat boiler 4, the SCR denitrification device 5, the heat exchanger 8, the secondary dust collector 6, the induced draft fan 9 and the chimney 12 in sequence through the exhaust gas conveying pipeline; and along the flow direction of the exhaust gas, a _NaHCO3 injection inlet is arranged on the exhaust gas conveying pipeline upstream of the primary dust collector 3, and the _NaHCO3 supply device is connected through the _NaHCO3 injection pipeline, and the _NaHCO3 injection pipeline and the _NaHCO3 supply device together constitute a dry desulfurization device 2.

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

The heat exchanger 2 8 is provided with a waste flue gas inlet, a waste flue gas outlet, a desalted water inlet and a desalted water outlet. The waste flue gas inlet is connected to the waste flue gas conveying pipeline upstream of the heat exchanger 2 8, and the waste flue gas outlet is connected to the waste flue gas conveying pipeline downstream of the heat exchanger 2 8; the desalted water inlet and the desalted water outlet are respectively connected to the economizer of the waste heat boiler 4 through the desalted water pipeline.

The primary dust collector is a gravity dust collector.

The secondary dust collector 6 is a bag dust collector.

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

The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims (4)

1. A combined coke dry quenching and coke oven flue gas purification process, characterized in that the coke oven waste flue gas generated during the coke oven heating process is sent to the dry quenching furnace after heat exchange and cooling, and the high-temperature coke is subjected to heat exchange and cooling. The waste flue gas discharged from the dry quenching furnace is dedusted by a primary dust collector, and a desulfurizing agent NaHCO ₃ is sprayed into the primary dust collector at the same time. The desulfurized waste flue gas enters a waste heat boiler to recover heat, and the waste flue gas outlet temperature is controlled by the waste heat boiler, so that the waste flue gas discharged after heat exchange directly enters an SCR denitration device for SCR denitration catalytic reaction; the denitrified waste flue gas is then sent to a chimney for discharge after heat exchange and cooling and secondary dust removal; the process specifically comprises the following steps: 1) Through the coke oven waste gas introduction system, the coke oven waste gas generated during the coke oven heating process is led out from the coke oven main flue and enters the heat exchanger 1; 2) In heat exchanger 1, the coke oven waste gas with a temperature of 200℃~300℃ is cooled to below 150℃ by desalted water from the waste heat boiler through indirect heat exchange. Part of the heat carried by the coke oven waste gas is recovered and sent to the waste heat boiler. The coke oven waste gas after heat exchange enters the dry quenching furnace through the air supply device at the bottom of the dry quenching furnace; 3) In the CDQ furnace, the coke oven waste gas contacts the high-temperature coke in reverse. After absorbing the heat of the coke, the waste gas is discharged from the upper section of the CDQ furnace and enters the primary dust collector. The cooled coke is discharged through the coke discharge system at the lower section of the CDQ furnace. 4) The dry desulfurization device sprays NaHCO ₃ into the primary dust collector through the NaHCO ₃ injection pipeline. In the primary dust collector, NaHCO ₃ fully contacts and reacts with SO ₂ in the waste flue gas to generate NaHSO ₃ and Na ₂ SO ₃ , thereby removing SO ₂ from the waste flue gas. The generated NaHSO ₃ , Na ₂ SO ₃ and coke powder carried by the waste flue gas are separated from the flue gas in the primary dust collector through inertial collision and sedimentation. 5) The waste flue gas after primary dust removal enters the waste heat boiler, which uses the heat carried by the waste flue gas to generate high-temperature and high-pressure steam for power generation or equipment driving, thereby realizing the recovery and utilization of coking waste heat; the waste flue gas after heat recovery by the waste heat boiler directly enters the SCR denitrification device through a pipeline for denitrification treatment; 6) The waste flue gas after denitration treatment 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 desalted water from the waste heat boiler through indirect heat exchange, and part of the heat carried by the waste flue gas is recovered and sent to the waste heat boiler. The cooled waste flue gas is sent to the secondary dust collector; 7) In the secondary dust collector, filtering and dust removal are used to remove solid particles and dust carried in the waste flue gas. The captured particles and dust are recovered by the dust collection device at the bottom of the secondary dust collector and then discharged externally. The waste flue gas after filtering and dust removal is sent to the chimney by the induced draft fan for discharge. 2. A coke dry quenching and coke oven flue gas combined purification system for realizing the process described in claim 1, characterized in that it comprises a coke oven waste flue gas introduction system, a heat exchanger 1, a dry quenching furnace, a dry desulfurization device, a primary dust collector, a waste heat boiler, an SCR denitrification device, a heat exchanger 2, a secondary dust collector, an induced draft fan and a chimney; the coke oven waste flue gas introduction system comprises a coke oven main flue and a flue flap, a coke oven waste gas outlet is arranged on the coke oven main flue, and the flue flap is arranged between the coke oven waste flue gas outlet and On the main flue of the coke oven between the chimneys; the coke oven waste gas outlet is connected to the waste gas inlet of the heat exchanger one through the coke oven waste gas pipeline, and the waste gas outlet of the heat exchanger one is connected to the air supply device at the bottom of the dry quenching furnace; the waste gas outlet at the top of the dry quenching furnace is connected to the primary dust collector, the waste heat boiler, the SCR denitrification device, the second heat exchanger, the secondary dust collector, the induced draft fan and the chimney in sequence through the waste gas conveying pipeline; and along the flow direction of the waste gas, _{a NaHCO3} injection inlet is arranged on the waste gas conveying pipeline upstream of the primary dust collector, which is connected to the _NaHCO3 supply device through the _NaHCO3 injection pipeline, and the _NaHCO3 injection pipeline and the _NaHCO3 supply device together constitute a dry desulfurization device; The heat exchanger 1 is provided with a desalted water inlet and a desalted water outlet, and the desalted water inlet and the desalted water outlet are respectively connected to the economizer of the waste heat boiler through a desalted water pipeline; The heat exchanger 2 is provided with a waste flue gas inlet, a waste flue gas outlet, a desalted water inlet and a desalted water outlet. The waste flue gas inlet is connected to the waste flue gas conveying pipeline upstream of the heat exchanger 2, and the waste flue gas outlet is connected to the waste flue gas conveying pipeline downstream of the heat exchanger 2; the desalted water inlet and the desalted water outlet are respectively connected to the economizer of the waste heat boiler through the desalted water pipeline. 3. The dry coke quenching and coke oven flue gas combined purification system according to claim 2, characterized in that the primary dust collector is a gravity dust collector. 4. The dry coke quenching and coke oven flue gas combined purification system according to claim 2, characterized in that the secondary dust collector is a bag dust collector.