A dry quenching boiler blowdown water waste heat recovery system and method

Abstract

The present application relates to a kind of dry quenching coke boiler blowdown water residual energy and waste heat recycling system and method, the system includes continuous blowdown expander, periodic blowdown expander, steam compressor, dry quenching coke boiler deaerator, blowdown water tank and dry quenching furnace water seal groove water supply intermediate water tank;The present application can safely, effectively to boiler blowdown water residual energy, waste heat is fully recycled, and can simultaneously recover the flash steam of various pressure grades of boiler blowdown water, does not release the flash steam of boiler blowdown water to the outside world, there is no "white smoke" generation in blowdown field, no waste water is generated, reaches the purpose of energy saving and environmental protection.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of waste heat utilization, and particularly relates to a dry quenching boiler blowdown water residual energy and waste heat recycling system and method. BACKGROUND

[0002] The dry quenching process in the coking field is a technology for recovering the sensible heat of red-hot coke in the coke oven production process. The basic principle is to cool the red-hot coke with a temperature of 950 DEG C to 1050 DEG C to below 180 DEG C through inert circulating gas, and at the same time, the high-temperature inert circulating gas is heated from below 130 DEG C to 880 DEG C to 960 DEG C. The high-temperature inert circulating gas after heating is sent to the dry quenching boiler by the circulating fan to heat the boiler feed water to make it phase change and increase the temperature to become superheated steam, and the superheated steam is sent to the steam turbine power station for power generation and heat supply.

[0003] The quality of the dry quenching boiler feed water is an important factor affecting the safe, stable and economic operation of the boiler steam-water system. In the process of boiler operation, the salt and impurities generated in the dry quenching boiler steam-water system will affect heat exchange, block the pipeline or cause the boiler to produce false water level. Therefore, the dry quenching boiler needs to use a blowdown system to discharge waste. The blowdown system is divided into continuous blowdown and periodic blowdown. Among them, the continuous blowdown is continuously discharging the water with high salt content in the boiler drum to the continuous blowdown expander (also called continuous blowdown flash tank) to ensure that the salt content inside the boiler is controlled within the normal range; the periodic blowdown is periodically discharging the impurities and water slag inside the boiler to the periodic blowdown expander (also called periodic blowdown flash tank) to avoid pipeline scaling or blockage.

[0004] The continuous blowdown water and the periodic blowdown water in the dry quenching boiler are sent to the continuous blowdown flash tank and the periodic blowdown flash tank respectively through the continuous blowdown pipeline and the periodic blowdown pipeline for expansion flash, respectively producing flash steam with different pressures, and the blowdown water after expansion flash is also discharged into the blowdown water tank to produce flash steam.

[0005] The flash steam of the continuous blowdown flash tank has a certain pressure requirement. Due to the process limitation of the dry quenching boiler, only a thermal deaerator can be used. The flash steam of the continuous blowdown flash tank is sent back to the deaerator tank using the residual pressure (below 0.2 MPa) as power to recover part of the working medium, but the steam loss is large and the residual pressure is not effectively utilized.

[0006] Due to the low pressure of flash steam from periodic blowdown expansion tanks, recycling is difficult, and direct venting is currently the most common method. Furthermore, due to the influence of venting volume and venting back pressure, the flash steam venting pipeline is long (the silencer is located on the top of the boiler), which increases the venting back pressure of the periodic blowdown expansion tank, resulting in a decrease in vented steam volume and an increase in the remaining blowdown volume, which in turn increases the workload and venting volume of the subsequent blowdown tank system. The flash steam pressure in the blowdown tank is even lower (close to atmospheric pressure), and currently, direct venting is used, which also leads to serious "white smoke" phenomenon at the blowdown tank site. If the flash steam from the periodic blowdown expansion tank is used to recover waste heat and working fluid through other condensation heat exchange methods (such as the "A Boiler Blowdown Wastewater Heat Energy Full Recovery Device" disclosed in Chinese Utility Model No. CN 215294873 U), pressurization is required. Otherwise, due to the low flash steam pressure, it will not be able to directly exchange heat with other heat exchange equipment. However, due to the limitation of heat exchange efficiency, the actual energy recovery rate of pressurized heat exchange is extremely low.

[0007] The current standard practice is to use the residual pressure of the flash steam from the continuous blowdown expansion tank of the CDQ boiler to send it to the deaeration water tank to recover some of the working fluid. Flash steam from the periodic blowdown expansion tank is discharged through a vent pipe to the top of the boiler and then released directly into the atmosphere through a vent silencer. Flash steam from the wastewater tank, due to low pressure, cannot be directed to the top of the boiler for release and is released directly into the atmosphere on-site. With the increasing implementation of full CDQ, the number of CDQ boilers has increased significantly, and the amount of periodic wastewater and flash steam has also increased. Consequently, the amount of wastewater and flash steam discharged from the wastewater tank has also increased. However, both of these flash steam releases are released to the atmosphere on-site, causing environmental pollution and wasting working fluids and energy. Summary of the Invention

[0008] The present invention provides a system and method for recovering the waste energy and waste heat of the wastewater from a dry coke quenching boiler. The system can safely and effectively recover the waste energy and waste heat of the wastewater from the boiler, and can simultaneously recover flash steam from the wastewater from the boiler at various pressure levels without releasing the flash steam from the wastewater to the outside. No "white smoke" is generated at the wastewater discharge site, and no wastewater is produced, thereby achieving the purpose of energy conservation and environmental protection.

[0009] In order to achieve the above object, the present invention adopts the following technical solutions:

[0010] A system for recovering waste energy and waste heat from wastewater from a dry coke quenching boiler, comprising a continuous blowdown expansion tank, a periodic blowdown expansion tank, a steam compressor, a dry coke quenching boiler deaerator, a blowdown tank, and an intermediate water tank for replenishing water in a water seal tank of the dry coke quenching boiler; the water inlet of the continuous blowdown expansion tank is connected to the continuous blowdown main pipe of the dry coke quenching boiler, and the water outlet of the continuous blowdown expansion tank is connected to the replenishing water inlet of the periodic blowdown expansion tank through a first drainage pipe; the water inlet of the periodic blowdown expansion tank is connected to the periodic blowdown main pipe of the dry coke quenching boiler, and the water outlet of the periodic blowdown expansion tank is connected to the water inlet of the blowdown tank through a second drainage pipe; the blowdown tank is provided with a blowdown pump, and the water outlet of the blowdown pump is connected to the intermediate water tank for replenishing water in a water seal tank of the dry coke quenching boiler through a third drainage pipe; the flash steam outlet of the continuous blowdown expansion tank, the flash steam outlet of the periodic blowdown expansion tank, and the flash steam outlet of the blowdown tank are all connected to the steam inlet of the steam compressor through the flash steam main pipe, and the compressed steam outlet of the steam compressor is connected to the compressed steam inlet of the dry coke quenching boiler deaerator through a compressor outlet pipe.

[0011] Furthermore, the body of the continuous sewage expansion tank adopts a vertical tank structure, the water inlet of the continuous sewage expansion tank is arranged on one side of the upper part of the continuous sewage expansion tank body, and the water outlet of the continuous sewage expansion tank is arranged on the other side of the lower part of the continuous sewage expansion tank body; the flash steam outlet of the continuous sewage expansion tank is arranged at the top of the continuous sewage expansion tank body.

[0012] Furthermore, the body of the periodic sewage discharge expansion tank adopts a vertical tank structure, the water inlet of the periodic sewage discharge expansion tank is arranged on one side of the upper part of the periodic sewage discharge expansion tank body, and the supplementary water inlet is arranged on the other side of the middle part of the periodic sewage discharge expansion tank body; the water outlet of the periodic sewage discharge expansion tank is arranged at the bottom of the periodic sewage discharge expansion tank body; the flash steam outlet of the periodic sewage discharge expansion tank is arranged at the top of the periodic sewage discharge expansion tank body.

[0013] Furthermore, the sewage tank adopts a closed box-shaped structure; the water inlet of the sewage tank is arranged on one side of the upper part of the sewage tank, and the sewage pump is installed on the top plate of the sewage tank.

[0014] A method for recovering and utilizing the waste energy and waste heat of wastewater from a dry quenching boiler comprises the following steps:

[0015] 1) The continuous blowdown of the CDQ boiler enters the continuous blowdown expansion tank through the continuous blowdown main pipe. The continuous blowdown is expanded and flash evaporated in the continuous blowdown expansion tank to produce first-stage flash steam. The first-stage flash steam enters the flash steam main pipe through the flash steam pipe 1. The continuous blowdown after flash evaporation enters the periodic blowdown expansion tank through the drainage pipe 1.

[0016] 2) The periodic wastewater from the CDQ boiler enters the periodic wastewater expansion tank through the periodic wastewater main pipe. The continuous wastewater and periodic wastewater after flash evaporation are expanded and flash evaporated in the periodic wastewater expansion tank to generate second-stage flash steam. The second-stage flash steam enters the flash steam main pipe through the flash steam pipe 2. All the boiler wastewater after flash evaporation enters the wastewater tank through the drainage pipe 3.

[0017] 3) After flash evaporation, all the boiler wastewater expands and flashes in the wastewater tank to produce third-stage flash steam; the third-stage flash steam enters the flash steam main pipe through the flash steam pipe 3;

[0018] 4) The three-stage flash steam is collected in the flash steam main pipe and then sucked into the steam compressor. After being compressed and pressurized by the steam compressor, the residual energy of the flash steam is increased, and the flash steam pressure is increased from 0-0.2MPa to 0.35-0.4MPa;

[0019] 5) The steam after being pressurized by the steam compressor is sent to the deaerator of the dry coke quenching boiler through the compressor outlet pipe for deoxygenation;

[0020] 6) The remaining sewage in the sewage tank is pressurized by the sewage pump and sent to the intermediate water tank for replenishing the water seal tank of the CDQ furnace, which is used to replenish water to the water seal tank at the top of the CDQ furnace.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1) While recovering the waste heat of boiler sewage working medium, it can also recover the residual pressure of boiler sewage flash steam of various pressure levels and make effective use of it.

[0023] 2) It can simultaneously recover flash steam from boiler wastewater of various pressure levels without releasing the flash steam from CDQ boiler wastewater to the outside world. No "white smoke" is generated on site. While recovering the excess energy and waste heat of the working fluid, it can also achieve the environmental protection effect of "eliminating white smoke".

[0024] 3) After the expansion of flash evaporation, the remaining dry quenching boiler wastewater was effectively utilized and no wastewater was generated.

[0025] 4) The wastewater from multiple CDQ boilers can be treated at the same time.

[0026] 5) The process is simple and can be automatically controlled. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of a system for recovering waste energy and waste heat from wastewater from a dry quenching boiler according to the present invention.

[0028] Figure: 1. Steam compressor 2. Continuous blowdown expansion tank 3. Periodic blowdown expansion tank 4. Sewage tank 5. Sewage pump 6. CDQ boiler deaerator 7. CDQ boiler water seal tank water replenishment intermediate water tank 8. Periodic blowdown main pipe 9. Continuous blowdown main pipe 10. Flash steam pipe 1 11. Flash steam pipe 2 12. Flash steam pipe 3 13. Flash steam main pipe 14. Compressor outlet pipe 15. Drain pipe 1 16. Drain pipe 2 17. Drain pipe 3 DETAILED DESCRIPTION

[0029] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings:

[0030] like Figure 1 As shown, the present invention relates to a system for recovering waste energy and waste heat from wastewater from a dry coke quenching boiler, comprising a continuous blowdown expansion tank 2, a periodic blowdown expansion tank 3, a steam compressor 1, a dry coke quenching boiler deaerator 6, a blowdown tank 4, and an intermediate water tank 7 for replenishing water in a water seal tank of the dry coke quenching boiler; the water inlet of the continuous blowdown expansion tank 2 is connected to a continuous blowdown main pipe 9 of the dry coke quenching boiler, and the water outlet of the continuous blowdown expansion tank 2 is connected to a replenishing water inlet of the periodic blowdown expansion tank 3 through a drainage pipe 15; the water inlet of the periodic blowdown expansion tank 3 is connected to a periodic blowdown main pipe 8 of the dry coke quenching boiler, and the periodic blowdown expansion tank 3 is connected to a replenishing water inlet of the periodic blowdown expansion tank 3. The water outlet of the periodic sewage expansion tank 3 is connected to the water inlet of the sewage tank 4 through the drainage pipe 2 16; the sewage tank 4 is provided with a sewage pump 5, and the water outlet of the sewage pump 5 is connected to the CDQ boiler water seal tank water replenishment intermediate water tank 7 through the drainage pipe 3 17; the flash steam outlet of the continuous sewage expansion tank 2, the flash steam outlet of the periodic sewage expansion tank 3 and the flash steam outlet of the sewage tank 4 are all connected to the steam inlet of the steam compressor 1 through the flash steam main pipe 13, and the compressed steam outlet of the steam compressor 1 is connected to the compressed steam inlet of the CDQ boiler deaerator 6 through the compressor outlet pipe 14.

[0031] Furthermore, the body of the continuous sewage expansion tank 2 adopts a vertical tank structure, the water inlet of the continuous sewage expansion tank 2 is arranged on one side of the upper part of the continuous sewage expansion tank body, and the water outlet of the continuous sewage expansion tank 2 is arranged on the other side of the lower part of the continuous sewage expansion tank body; the flash steam outlet of the continuous sewage expansion tank 2 is arranged at the top of the continuous sewage expansion tank body.

[0032] Furthermore, the body of the periodic sewage discharge expansion tank 3 adopts a vertical tank structure, the water inlet of the periodic sewage discharge expansion tank 3 is arranged on one side of the upper part of the periodic sewage discharge expansion tank body, and the supplementary water inlet is arranged on the other side of the middle part of the periodic sewage discharge expansion tank body; the water outlet of the periodic sewage discharge expansion tank 3 is arranged at the bottom of the periodic sewage discharge expansion tank body; the flash steam outlet of the periodic sewage discharge expansion tank 3 is arranged at the top of the periodic sewage discharge expansion tank body.

[0033] Furthermore, the sewage tank 4 adopts a closed box-shaped structure; the water inlet of the sewage tank 4 is arranged on one side of the upper part of the sewage tank 4, and the sewage pump 5 is installed on the top plate of the sewage tank 4.

[0034] The present invention provides a method for recovering and utilizing the waste energy and waste heat of wastewater from a dry coke quenching boiler, comprising the following steps:

[0035] 1) The continuous blowdown from the CDQ boiler enters the continuous blowdown expansion tank 2 through the continuous blowdown main pipe 9. The continuous blowdown is expanded and flash evaporated in the continuous blowdown expansion tank 2 to produce first-stage flash steam. The first-stage flash steam enters the flash steam main pipe 13 through the flash steam pipe 10. The continuous blowdown after flash evaporation enters the periodic blowdown expansion tank 3 through the drainage pipe 15.

[0036] 2) The periodic wastewater from the CDQ boiler enters the periodic wastewater expansion tank 3 via the periodic wastewater main pipe 8. The continuous wastewater and the periodic wastewater after flash evaporation are expanded and flash evaporated in the periodic wastewater expansion tank 3 to generate second-stage flash steam. The second-stage flash steam enters the flash steam main pipe 13 via the second flash steam pipe 11. All the boiler wastewater after flash evaporation enters the wastewater tank 4 via the third drainage pipe 17.

[0037] 3) After flash evaporation, all the boiler wastewater expands and flashes in the wastewater tank 4 to produce third-stage flash steam; the third-stage flash steam enters the flash steam main pipe 13 through the flash steam pipe 3 12;

[0038] 4) The three-stage flash steam is collected in the flash steam main pipe 13 and then sucked into the steam compressor 1. After being compressed and pressurized by the steam compressor 1, the flash steam residual energy is increased, and the flash steam pressure is increased from 0-0.2 MPa to 0.35-0.4 MPa;

[0039] 5) The steam pressurized by the steam compressor 1 is sent to the CDQ boiler deaerator 6 through the compressor outlet pipe 14 for deoxygenation;

[0040] 6) The remaining sewage in the sewage tank 4 is pressurized by the sewage pump 5 and sent to the intermediate water tank 7 for replenishing the water seal tank of the CDQ furnace, which is used to replenish water in the water seal tank at the top of the CDQ furnace.

[0041] The present invention relates to a system for recovering the waste energy and waste heat of wastewater from a dry coke quenching boiler, comprising a continuous wastewater main pipe 9 and a periodic wastewater main pipe 8 connected to the dry coke quenching boiler, a continuous wastewater expansion vessel 2, a periodic wastewater expansion vessel 3, a wastewater tank 4, a wastewater pump 5, a steam compressor 1, a dry coke quenching boiler deaerator 6, and a dry coke quenching boiler water seal tank water replenishment intermediate water tank 7, and other equipment.

[0042] The continuous sewage from the dry quenching boiler is discharged into the corresponding continuous sewage expansion tank 2 through the continuous sewage main pipe 8, and the first-stage flash steam generated by the expansion flash evaporation enters the flash steam main pipe 13 through the flash steam pipe 10.

[0043] The wastewater after flash evaporation in the continuous blowdown expansion tank 2 enters the periodic blowdown expansion tank 3, and the periodic wastewater from the dry quenching boiler is also discharged into the periodic blowdown expansion tank 3 through the periodic blowdown main pipe 8. The two types of wastewater are expanded and flash evaporated in the periodic blowdown expansion tank 3, and the generated second-stage flash steam enters the flash steam main pipe 13 through the flash steam pipe 2 11.

[0044] The sewage after flash evaporation in the periodic sewage expansion tank 3 enters the sewage tank 4 , and the third-stage flash steam generated after expansion and flash evaporation in the sewage tank 4 enters the flash steam main pipe 13 through the flash steam pipeline 12 .

[0045] After the steam compressor 1 absorbs the third-stage flash steam in the flash steam main pipe 13, it compresses and increases the pressure to obtain low-pressure steam of 0.35-0.4 MPa. The low-pressure steam is sent to the dry quenching boiler deaerator 6 through the compressor outlet pipe 14 for deoxygenation of the dry quenching boiler feed water.

[0046] The remaining sewage after the expansion and flash evaporation of the sewage tank 4 is sent to the intermediate water tank 7 for replenishing the water seal tank of the CDQ furnace by the sewage pump 5 as the replenishing water for the water seal tank on the top of the CDQ furnace.

[0047] The present invention fully recovers and utilizes waste heat and waste energy in the CDQ system. However, the present invention is not only applicable to CDQ boiler systems, but also to other industrial boiler systems that require waste heat and waste energy recovery from wastewater.

[0048] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A system for recovering waste energy and waste heat from wastewater from a dry coke quenching boiler, characterized in that: It includes a continuous sewage expansion tank, a periodic sewage expansion tank, a steam compressor, a dry quenching boiler deaerator, a sewage tank and an intermediate water tank for replenishing the water seal tank of the dry quenching boiler; the water inlet of the continuous sewage expansion tank is connected to the continuous sewage main pipe of the dry quenching boiler, and the water outlet of the continuous sewage expansion tank is connected to the replenishing water inlet of the periodic sewage expansion tank through a drainage pipe 1; the water inlet of the periodic sewage expansion tank is connected to the periodic sewage main pipe of the dry quenching boiler, and the water outlet of the periodic sewage expansion tank is connected to the water inlet of the sewage tank through a drainage pipe 2; the sewage tank is provided with a sewage pump, and the water outlet of the sewage pump is connected to the intermediate water tank for replenishing the water seal tank of the dry quenching boiler through a drainage pipe 3; the flash steam outlet of the continuous sewage expansion tank, the flash steam outlet of the periodic sewage expansion tank and the flash steam outlet of the sewage tank are all connected to the steam inlet of the steam compressor through the flash steam main pipe, and the compressed steam outlet of the steam compressor is connected to the compressed steam inlet of the dry quenching boiler deaerator through the compressor outlet pipe.

2. A system for recovering waste energy and waste heat from wastewater from a dry coke quenching boiler according to claim 1, characterized in that: The body of the continuous sewage expansion tank adopts a vertical tank structure, the water inlet of the continuous sewage expansion tank is arranged on one side of the upper part of the continuous sewage expansion tank body, and the water outlet of the continuous sewage expansion tank is arranged on the other side of the lower part of the continuous sewage expansion tank body; the flash steam outlet of the continuous sewage expansion tank is arranged at the top of the continuous sewage expansion tank body.

3. The system for recovering waste heat and energy from wastewater from dry quenching boilers according to claim 1, characterized in that: The body of the periodic sewage discharge expansion tank adopts a vertical tank structure, the water inlet of the periodic sewage discharge expansion tank is arranged on one side of the upper part of the periodic sewage discharge expansion tank body, and the supplementary water inlet is arranged on the other side of the middle part of the periodic sewage discharge expansion tank body; the water outlet of the periodic sewage discharge expansion tank is arranged at the bottom of the periodic sewage discharge expansion tank body; the flash steam outlet of the periodic sewage discharge expansion tank is arranged at the top of the periodic sewage discharge expansion tank body.

4. A system for recovering waste heat and energy from wastewater from a dry quenching boiler according to claim 1, characterized in that: The sewage tank adopts a closed box-shaped structure; the water inlet of the sewage tank is arranged on one side of the upper part of the sewage tank, and the sewage pump is installed on the top plate of the sewage tank.

5. A method for recovering waste energy and waste heat from wastewater from a dry coke quenching boiler based on the system according to any one of claims 1 to 4, characterized in that: The process includes the following: 1) The continuous blowdown of the CDQ boiler enters the continuous blowdown expansion tank through the continuous blowdown main pipe. The continuous blowdown is expanded and flash evaporated in the continuous blowdown expansion tank to produce first-stage flash steam. The first-stage flash steam enters the flash steam main pipe through the flash steam pipe 1. The continuous blowdown after flash evaporation enters the periodic blowdown expansion tank through the drainage pipe 1. 2) The periodic wastewater from the CDQ boiler enters the periodic wastewater expansion tank through the periodic wastewater main pipe. The continuous wastewater and periodic wastewater after flash evaporation are expanded and flash evaporated in the periodic wastewater expansion tank to generate second-stage flash steam. The second-stage flash steam enters the flash steam main pipe through the flash steam pipe 2. All the boiler wastewater after flash evaporation enters the wastewater tank through the drainage pipe 3. 3) After flash evaporation, all the boiler wastewater expands and flashes in the wastewater tank to produce third-stage flash steam; the third-stage flash steam enters the flash steam main pipe through the flash steam pipe 3; 4) The three-stage flash steam is collected in the flash steam main pipe and then sucked into the steam compressor. After being compressed and pressurized by the steam compressor, the residual energy of the flash steam is increased, and the flash steam pressure is increased from 0-0.2MPa to 0.35-0.4MPa; 5) The steam after being pressurized by the steam compressor is sent to the deaerator of the dry coke quenching boiler through the compressor outlet pipe for deoxygenation; 6) The remaining sewage in the sewage tank is pressurized by the sewage pump and sent to the intermediate water tank for replenishing the water seal tank of the CDQ furnace, which is used to replenish water to the water seal tank at the top of the CDQ furnace.

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