Coke oven flue gas waste heat recovery power generation system

Abstract

The utility model relates to a coke oven flue gas waste heat recovery power generation system which comprises a coke oven flue gas waste heat recovery unit and an organic Lamberkine cycle power generation unit, the coke oven flue gas waste heat recovery unit consists of a flue gas source flue, a waste heat recovery flue, a flue gas heat exchanger, a flue gas fan, a chimney and a bypass flue; the organic Lamberkine cycle power generation unit consists of a working medium expansion machine, a power generator, a power generation grid-connected cabinet, a working medium condenser and a working medium pump; coke oven flue gas with the temperature of about 210 DEG C is subjected to heat exchange and cooling through a flue gas heat exchanger, then pressurized through a fan, led to a chimney and exhausted to the atmosphere, and waste heat recovery of the coke oven flue gas is completed. Heat of coke oven flue gas in the flue gas heat exchanger is converted into the organic working medium, the high-temperature organic working medium expands in the working medium expansion machine to do work, then the power generator is driven to generate power, and energy conversion and utilization are achieved.

Description

Technical Field

[0001] The utility model relates to the technical field of coke oven waste heat recovery and utilization, in particular to a coke oven flue gas waste heat recovery and power generation system using an organic Rankine cycle. Background Art

[0002] During the coking process, coke oven flue gas is the waste gas generated by the combustion and heat exchange of heated coal gas. The heat it carries with it accounts for approximately 17% of the total heat input to the coking process. Directly discharging this waste gas into the atmosphere without purification and heat recovery results in energy loss and environmental pollution. The waste heat from coke oven flue gas is low-grade and has a low calorific value. While flue gas temperatures vary across different coke oven types, the vast majority remain below 270°C or even lower, making it difficult to recycle.

[0003] Recovering heat from coke oven flue gas is crucial for reducing energy consumption and overall carbon emissions during the coking process. Currently, the mainstream method for recovering waste heat from coke oven flue gas is to use waste heat boilers to generate hot water or low-pressure saturated steam, which is then fed into the steam network.

[0004] For example, the Chinese utility model patent with publication number CN204373429U discloses a "coke oven flue gas waste heat recovery device", which includes a flue gas system part, a steam-water system part and a power generation system part. The flue gas of the coke oven flue gas part is sequentially introduced into the chimney by the induced draft fan through the heat pipe waste heat boiler and the economizer; the industrial water of the steam-water system part is softened and deoxygenated, and then sent into the economizer for heat exchange with the flue gas from the heat pipe waste heat boiler. After that, the steam and water are separated in the steam drum of the heat pipe waste heat boiler to produce 0.7-1.0MPa saturated steam; the steam after steam-water separation enters the power generation system part for power generation, so that the saturated steam is reduced in pressure to 0.3-0.5MPa.

[0005] However, for coking plants, the overall demand for hot water and low-pressure steam is relatively low, and the hot water and steam produced by utilizing waste heat from other production processes can already meet the needs of users. Therefore, it is necessary to explore a feasible method to efficiently recover waste heat from coke oven flue gas, while also ensuring that the recovered energy can be more directly utilized by users. Summary of the Invention

[0006] The utility model provides a coke oven flue gas waste heat recovery power generation system, which cools the coke oven flue gas with a temperature of about 210°C through heat exchange in a flue gas heat exchanger, and then pressurizes it through a fan and leads it to a chimney to be discharged into the atmosphere, thereby completing the waste heat recovery of the coke oven flue gas; the heat of the coke oven flue gas in the flue gas heat exchanger is converted into an organic working fluid, and the high-temperature organic working fluid expands and performs work in a working fluid expander, thereby driving a generator to generate electricity, thereby realizing energy conversion and utilization.

[0007] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0008] A coke oven flue gas waste heat recovery power generation system, comprising a coke oven flue gas waste heat recovery unit and an organic Langken cycle power generation unit; the coke oven flue gas waste heat recovery unit is composed of a flue gas source flue, a waste heat recovery flue, a flue gas heat exchanger, a flue gas fan, a chimney and a bypass flue; the flue gas source flue is connected to the flue gas heat exchanger, the flue gas fan and the chimney in sequence through the waste heat recovery flue, and the flue gas source flue is directly connected to the chimney through the bypass flue; a waste heat recovery unit inlet damper is provided on the waste heat recovery flue close to the flue gas source flue; a bypass flue close to the flue gas source flue is provided flue damper; a waste heat recovery unit outlet damper is provided on the waste heat recovery flue near the chimney; the flue gas heat exchanger is a radial heat pipe heat exchanger; the organic Langken cycle power generation unit consists of a working fluid expander, a generator, a power generation grid cabinet, a working fluid condenser and a working fluid pump; the organic working fluid outlet of the flue gas heat exchanger is connected to the organic working fluid inlet of the flue gas heat exchanger through an organic working fluid circulation pipeline; a working fluid expander, a working fluid condenser and a working fluid pump are provided in sequence on the organic working fluid circulation pipeline along the flow direction of the organic working fluid; the working fluid expander is also connected to a generator, and the generator is connected to the external power grid through the power generation grid cabinet.

[0009] Furthermore, the flue gas heat exchanger is composed of a shell and a heat exchange element, one end of the shell is the flue gas inlet end, and the other end is the flue gas outlet end; the interior of the shell is divided into a preheating section, an evaporation section and a superheating section in sequence from the flue gas outlet end to the flue gas inlet end; the heat exchange element is composed of an inlet header, an internal coil, and an outlet header; the inlet header and the outlet header are both arranged perpendicular to the internal coil; the inlet header is arranged close to the flue gas outlet end, and the outlet header is arranged close to the flue gas inlet end; the internal coil is a radial heat exchange tube, which is composed of a heat exchange tube body and a jacket structure, and the jacket structure is filled with liquid working medium.

[0010] Furthermore, the internal coil is composed of multiple rows and columns of radial heat exchange tubes, and two adjacent radial heat exchange tubes are connected through elbows.

[0011] Furthermore, an expander inlet filter is provided on the organic working fluid circulation pipeline upstream of the working fluid expander, and a working fluid pump inlet filter is provided on the organic working fluid circulation pipeline upstream of the working fluid pump.

[0012] Furthermore, the inlet damper of the waste heat recovery unit, the bypass flue damper and the outlet damper of the waste heat recovery unit are interlocked and controlled by a control system.

[0013] Compared with the prior art, the beneficial effects of the present invention are:

[0014] 1) The waste heat from low-grade coke oven flue gas is converted into high-grade energy;

[0015] 2) Set up a safety interlock mechanism to ensure continuous and stable operation of the system;

[0016] 3) The flue gas heat exchanger uses radial heat pipe forced circulation, which has better stability and safety than the heat exchanger using conventional natural circulation, higher circulation rate and higher thermal efficiency;

[0017] 4) The organic working fluid circulating in the organic Langken cycle power generation unit is preferably pentafluoropropane, which has a low boiling point and can be vaporized at a lower temperature. For coke oven flue gas with low calorific value, the waste heat recovery efficiency is higher and the recovery capacity is stronger, while meeting the work requirements of the generator.

[0018] 5) The flue gas heat exchanger adopts a steam drum-free design, which has a more compact structure and lower manufacturing cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural schematic diagram of a coke oven flue gas waste heat recovery power generation system described in the utility model.

[0020] Figure 2a It is a structural schematic diagram of the flue gas heat exchanger of the present invention.

[0021] Figure 2b This is a schematic diagram of the structure of the heat exchange element in the flue gas heat exchanger of the utility model. Figure 1 ( Figure 2a side view).

[0022] Figure 2c This is a schematic diagram of the structure of the heat exchange element in the flue gas heat exchanger of the utility model ( Figure 2a looking down).

[0023] Figure 3 It is a schematic diagram of the principle of the flue gas heat exchanger of the present invention.

[0024] Figure: Ⅰ. Coke Oven Flue Gas Waste Heat Recovery Unit Ⅱ. Organic Langken Cycle Power Generation Unit 1. Flue Gas Source Flue 2. Flue Gas Heat Exchanger Inlet Flue 3. Flue Gas Heat Exchanger Outlet Flue 4. Flue Gas Fan Outlet Flue 5. Bypass Flue 6. Waste Heat Recovery Unit Inlet Dam 7. Flue Gas Heat Exchanger 71. Radial Heat Exchange Tubes 72. Jacket Structure 73. Inlet Header 74. Outlet Header A. Preheating Section B. Evaporation Section C. Superheating Section 8. Flue Gas Fan 9. Waste Heat Recovery Unit Outlet Dam 10. Chimney 11. Bypass Duct Dam 12. Expander Inlet Filter 13. Working Medium Expander 14. Generator 15. Power Generation Grid Cabinet 16. Working Medium Condenser 17 Working Medium Pump Inlet Filter 18. Working Medium Pump 19. Organic Working Medium Outlet Pipe 20. Organic Working Medium Inlet Pipe 21. Cooling Water Inlet Pipe 22. Cooling Water Return Pipe DETAILED DESCRIPTION

[0025] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings:

[0026] like Figure 1 As shown, the coke oven flue gas waste heat recovery and power generation system described in the present invention is a process system that uses an organic Rankine cycle to recover the waste heat of coke oven flue gas and generate electricity. It is also a process system that stably and efficiently converts low-grade coke oven flue gas waste heat into high-grade energy.

[0027] The coke oven flue gas waste heat recovery power generation system described in the present invention comprises two subsystems: a coke oven flue gas waste heat recovery unit I and an organic Rankine cycle power generation unit II.

[0028] The coke oven flue gas waste heat recovery unit I consists of a flue gas source flue 1, a waste heat recovery flue, a flue gas heat exchanger 7, a flue gas fan 8, a chimney 10 and a bypass flue 5; the waste heat recovery flue further includes a flue gas heat exchanger inlet flue 2, a flue gas heat exchanger outlet flue 3 and a flue gas fan outlet flue 4.

[0029] Organic Rankine cycle power generation unit II consists of a working fluid expander 13, a generator 14, a power generation grid cabinet 15, a working fluid condenser 16 and a working fluid pump 18. It also includes an expander inlet filter 12, a working fluid pump inlet filter 17, an organic working fluid outlet pipe 19, an organic working fluid inlet pipe 29, a cooling water inlet pipe 21 and a cooling water return pipe 22.

[0030] like Figure 2a-2c As shown, the flue gas heat exchanger 7 consists of a shell and a heat exchange element, one end of the shell is the flue gas inlet end, and the other end is the flue gas outlet end; the interior of the shell is divided into a preheating section A, an evaporation section B and a superheating section C in the direction from the flue gas outlet end to the flue gas inlet end; the heat exchange element consists of an inlet header 73, an internal coil, and an outlet header 74; the inlet header 73 and the outlet header 74 are both arranged perpendicular to the internal coil; the inlet header 73 is arranged close to the flue gas outlet end, and the outlet header 74 is arranged close to the flue gas inlet end; the internal coil is a radial heat exchange tube 71, which consists of a heat exchange tube body and a jacket structure 72, and the jacket structure 72 is filled with liquid working medium.

[0031] like Figure 3 As shown, the working principle of the flue gas heat exchanger 7 is as follows:

[0032] Gas side: Flue gas heat exchanger 7 is positioned vertically or horizontally. High-temperature flue gas enters through the flue gas inlet, passes through the superheating section C, evaporation section B, and preheating section A in sequence, and finally flows out through the flue gas outlet. The superheating section C, evaporation section B, and preheating section A are connected in series via elbows.

[0033] Medium side: The superheating section C, evaporation section B and preheating section A in the flue gas heat exchanger 7 have the same structure, and all include radial heat exchange tubes (or enhanced heat transfer tubes).

[0034] When the coke oven flue gas enters the flue gas heat exchanger 7 and flows through the internal coil, it transfers heat to the liquid working medium in the jacket structure. The liquid working medium absorbs heat and vaporizes, transferring heat to the organic working medium in the heat exchange tube body. After heat exchange, the liquid working medium condenses into liquid again. This repeated absorption and release of heat completes the heat exchange process between the coke oven flue gas and the organic working medium.

[0035] The organic working fluid first enters the flue gas heat exchanger 7 through the organic working fluid circulation pipeline, is distributed to each radial heat exchange tube through the inlet header 73, and is heated by the liquid working fluid in the jacket structure that has been heated by heat exchange with the coke oven flue gas. That is, the heat of the flue gas is transferred to the organic working fluid through the liquid working fluid. The organic working fluid after absorbing the heat is collected in the outlet header 74 and enters the organic working fluid circulation pipeline, and then drives the working fluid expander 13 to do work, and then drives the generator 14 to generate electricity. The above process is repeated.

[0036] Conventional radial tube heat exchangers typically employ natural circulation with a steam drum. However, the flue gas heat exchanger 7 of the present invention eliminates the steam drum required for conventional natural circulation. Forced circulation is achieved through a working fluid pump 18, simplifying the system's internal structure. Pipeline height is no longer restricted by the steam drum, significantly reducing equipment weight and auxiliary support structures, and lowering investment costs. Forced circulation significantly increases the organic working fluid's circulation rate, resulting in higher heat utilization and enhanced safety and stability in equipment operation.

[0037] In the present invention, after dust removal, the coke oven flue gas enters the coke oven flue gas waste heat recovery unit I through the flue gas source flue 1. The temperature of the coke oven flue gas entering the coke oven flue gas waste heat recovery unit I is about 210°C. Under normal system operation, the waste heat recovery unit inlet damper 6 is open, the bypass flue damper 11 is closed, and the waste heat recovery unit outlet damper 9 is open. The coke oven flue gas in the flue gas source flue 1 enters the flue gas heat exchanger 7 through the flue gas heat exchanger inlet flue 2. After heat exchange, the flue gas temperature is reduced to below 165°C, and its heat is carried away by the organic working medium. After completing heat exchange and cooling, the coke oven flue gas is drawn out from the flue gas heat exchanger outlet flue 3, pressurized by the flue gas fan 8, and discharged into the atmosphere through the flue gas fan outlet flue 4 into the chimney 10.

[0038] When the coke oven flue gas waste heat recovery unit is operating abnormally (due to a malfunction or maintenance), the waste heat recovery unit inlet damper 6 is closed, the bypass flue damper 11 is opened, and the waste heat recovery unit outlet damper 9 is closed. The coke oven flue gas in the flue gas source flue is directly introduced into chimney 10 without undergoing cooling or heat exchange, and is exhausted to the atmosphere through the chimney 10's suction force.

[0039] The organic working fluid circulating in the organic Rankine cycle power generation unit II of the present invention is heated by the flue gas heat exchanger 7 to generate superheated steam. After being filtered by the expander inlet filter 12, it enters the working fluid expander 13, driving the working fluid expander 13 to perform work, thereby driving the generator 14 to generate electricity. The electricity generated by the generator 14 is transmitted to the external power grid via the power generation grid cabinet 15. The organic working fluid exiting the working fluid expander 13 is sent to the working fluid condenser 16 for cooling and condensation, returning to a 35°C liquid state. The condensed organic working fluid is filtered by the working fluid pump inlet filter 17 and enters the working fluid pump 18. The working fluid pump 18 pressurizes the low-temperature liquid organic working fluid and returns it to the flue gas heat exchanger 7 for heating, completing the organic working fluid cycle.

[0040] To make the purpose, technical solution, and technical effects of the present invention more clearly understood, the technical solutions in the embodiments of the present invention are now described clearly and completely. However, the embodiments described below are only a portion of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art without inventive effort in conjunction with the embodiments of the present invention are also within the scope of protection of the present invention.

[0041] [Example]

[0042] like Figure 1 As shown, in this embodiment, the coke oven flue gas waste heat recovery power generation system includes a coke oven flue gas waste heat recovery unit I and an organic Rankine cycle power generation unit II.

[0043] The coke oven flue gas waste heat recovery unit I includes a hot flue gas source flue 1, a flue gas heat exchanger inlet flue 2, a flue gas heat exchanger outlet flue 3, a flue gas fan outlet flue 4, a bypass flue 5, a waste heat recovery unit inlet damper 6, a flue gas heat exchanger 7, a flue gas fan 8, a waste heat recovery unit outlet damper 9, a chimney 10, a bypass flue damper 11, etc.

[0044] The organic Rankine cycle power generation unit II includes a working fluid expander inlet filter 12, a working fluid expander 13, a generator 14, a power generation grid cabinet 15, a working fluid condenser 16, a working fluid pump inlet filter 17, a working fluid pump 18, an organic working fluid outlet pipe 19, an organic working fluid inlet pipe 20, a cooling water inlet pipe 21, a cooling water return pipe 22, etc.

[0045] Taking the typical coke oven working condition as an example, the flue gas temperature at the inlet of the coke oven flue gas waste heat recovery unit I is about 210℃, and the flue gas flow rate is about 400000Nm 3 / h, the main components of coke oven flue gas are CO2, H2O, N2, and O2, and the volume fractions of the above components are 4.18, 13.58%, 72.64%, and 9.6% respectively.

[0046] During normal operation of the coke oven flue gas waste heat recovery power generation system, the waste heat recovery unit inlet damper 6 is open, the bypass flue damper 11 is closed, and the waste heat recovery unit outlet damper 9 is open. Coke oven flue gas from flue gas source flue 1 passes through flue gas heat exchanger inlet flue 2 and enters flue gas heat exchanger 7. After heat exchange, the temperature drops to 165°C and is discharged through flue gas heat exchanger outlet flue 3. After being pressurized by flue gas fan 8, it is introduced into chimney 10.

[0047] According to calculation, in this embodiment, the waste heat recovered per unit volume of coke oven flue gas is 61.6kJ / Nm 3 , combined with the flue gas volume and considering the heat exchange efficiency, the waste heat recovery heat achieved by the flue gas heat exchanger 7 is 61.6×400000×0.96=23654400 kJ / h, or 6571 kW.

[0048] Meanwhile, the organic refrigerant enters the flue gas heat exchanger 7 for heat exchange, then enters the refrigerant expander inlet filter 12 through the organic refrigerant outlet pipe 19. After filtration, it enters the refrigerant expander 13 to perform work, further driving the generator 14 to generate electricity. The generated electricity is then transmitted to the external power grid via the power generation grid cabinet 15. The expanded organic refrigerant undergoes heat exchange in the refrigerant condenser 16, condenses into a liquid, passes through the refrigerant pump inlet filter 17, and enters the refrigerant pump 18. After being pressurized, it is delivered to the flue gas heat exchanger 7 through the organic refrigerant inlet pipe 20 for heat exchange, completing the organic Rankine cycle.

[0049] In this embodiment, considering that the comprehensive power generation efficiency of the organic Rankine cycle is about 13%, the electric energy delivered to the grid is about 6571×0.13=854 kW, that is, the energy obtained through waste heat recovery is 854 kW.

[0050] The above is only a preferred specific implementation method of the present invention, but the protection scope of the present invention is not limited to this. Any technician familiar with the technical field within the technical scope disclosed by the present invention can make equivalent replacements or changes based on the technical solution and inventive concept of the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A coke oven flue gas waste heat recovery power generation system, characterized in that: It includes a coke oven flue gas waste heat recovery unit and an organic Langken cycle power generation unit; the coke oven flue gas waste heat recovery unit is composed of a flue gas source flue, a waste heat recovery flue, a flue gas heat exchanger, a flue gas fan, a chimney and a bypass flue; the flue gas source flue is connected to the flue gas heat exchanger, the flue gas fan and the chimney in sequence through the waste heat recovery flue, and the flue gas source flue is directly connected to the chimney through the bypass flue; a waste heat recovery unit inlet damper is provided on the waste heat recovery flue close to the flue gas source flue; a bypass flue damper is provided on the bypass flue close to the flue gas source flue; A waste heat recovery unit outlet gate is provided on the waste heat recovery flue of the chimney; the flue gas heat exchanger is a radial heat pipe heat exchanger; the organic Langken cycle power generation unit is composed of a working fluid expander, a generator, a power generation grid cabinet, a working fluid condenser and a working fluid pump; the organic working fluid outlet of the flue gas heat exchanger is connected to the organic working fluid inlet of the flue gas heat exchanger through an organic working fluid circulation pipeline; a working fluid expander, a working fluid condenser and a working fluid pump are provided in sequence on the organic working fluid circulation pipeline along the flow direction of the organic working fluid; the working fluid expander is also connected to a generator, and the generator is connected to the external power grid through the power generation grid cabinet.

2. The coke oven flue gas waste heat recovery power generation system according to claim 1, characterized in that: The flue gas heat exchanger consists of a shell and a heat exchange element, one end of the shell is the flue gas inlet end, and the other end is the flue gas outlet end; the interior of the shell is divided into a preheating section, an evaporation section and a superheating section in sequence from the flue gas outlet end to the flue gas inlet end; the heat exchange element consists of an inlet header, an internal coil and an outlet header; the inlet header and the outlet header are both arranged perpendicular to the internal coil; the inlet header is arranged close to the flue gas outlet end, and the outlet header is arranged close to the flue gas inlet end; the internal coil is a radial heat exchange tube, consisting of a heat exchange tube body and a jacket structure, and the jacket structure is filled with liquid working medium.

3. The coke oven flue gas waste heat recovery power generation system according to claim 2, characterized in that: The internal coil is composed of multiple rows and columns of radial heat exchange tubes, and two adjacent radial heat exchange tubes are connected through elbows.

4. The coke oven flue gas waste heat recovery power generation system according to claim 1, characterized in that: An expander inlet filter is provided on the organic working medium circulation pipeline upstream of the working medium expander, and a working medium pump inlet filter is provided on the organic working medium circulation pipeline upstream of the working medium pump.

5. The coke oven flue gas waste heat recovery power generation system according to claim 1, characterized in that: The waste heat recovery unit inlet damper, the bypass flue damper and the waste heat recovery unit outlet damper are interlocked and controlled by a control system.

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