Coal-gas cogeneration power generation system coupled with thermal power generation and its control method

Abstract

The present invention relates to a coke-electricity-coupling coal-gas cogeneration power generation system and a control method thereof, and belongs to the technical field of waste heat power generation. It comprises a coke oven waste heat boiler, a coal gas boiler and a steam turbine generator set, wherein the coke oven waste heat boiler and the coal gas boiler are respectively connected to the steam turbine generator set, and the coke oven waste heat boiler and / or the coal gas boiler drive the steam turbine generator set to operate; when the load rate of the coal gas boiler is ≥90%, the coke oven waste heat boiler operates at a constant pressure; when the load rate of the coal gas boiler is between 50% and 90%, the coke oven waste heat boiler operates at a sliding pressure; when the load rate of the coal gas boiler is ≤50%, the coke oven waste heat boiler operates at a constant pressure. The present invention can match a high-capacity, high-parameter steam turbine generator set, thereby improving the power generation efficiency of the coke oven waste heat boiler, and at the same time preventing the shutdown of the steam turbine generator set when the steam of the coal gas boiler fluctuates and the damage caused by the long-term low-load operation of the high-parameter, high-capacity generator set.

Description

Technical Field

[0001] The invention belongs to the technical field of waste heat power generation, and relates to a coke-electricity coupled coal-gas cogeneration power generation system and a control method thereof. Background Art

[0002] In the process of producing coke, coking plants will produce high-temperature flue gas with a temperature of 1000-1200℃. The flue gas at this temperature can be used to generate high-temperature and high-pressure, high-temperature and ultra-high-pressure, ultra-high-temperature and ultra-high-pressure high-parameter steam through the coke oven waste heat boiler. After the heat utilization is completed, the exhaust flue gas temperature is about 180℃, and the temperature before the economizer in the furnace meets the catalyst temperature requirements for denitrification in the furnace.

[0003] The steelmaking and ironmaking units of steel plants produce a large amount of low calorific value blast furnace and converter gas. In addition to being used for normal production, a large amount of this gas is still left over. Usually, this surplus gas is used to build a separate gas power plant for power generation, and the flue gas is treated by denitrification in the furnace and desulfurization after the furnace.

[0004] Coke oven waste heat power generation and coal gas power generation are usually two independent units. Due to their different operation modes, the two units are difficult to unify the deaeration steam turbine side. They have been built and used separately, requiring a larger footprint and more operating personnel. Since the coke oven waste heat power generation is stable, it adopts a constant pressure operation mode; coal gas power generation usually adopts a sliding pressure operation mode due to the frequent fluctuations of the coal gas system. When the coke oven waste heat boiler is operated alone, the steam production is limited, which is not enough to build a high-parameter, high-capacity generator set, and the power generation efficiency is low. If a high-parameter, high-capacity generator set is forcibly adopted, the high-parameter, high-capacity generator set will be damaged after long-term low-load operation, which is not worth the loss. When the coal gas boiler is operated alone, if the steam volume of the coal gas boiler is insufficient, the generator set needs to stop running, and the shutdown maintenance and restart costs are high. Due to environmental protection requirements, the emissions of the coke oven waste heat boiler must be desulfurized and denitrated. However, due to the low feed water temperature of the coke oven waste heat boiler, the denitration in the furnace will cause the by-products after denitration to corrode the economizer. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide a coke-electricity coupled coal-gas cogeneration power generation system and a control method thereof, which can match a high-capacity, high-parameter steam turbine generator set, thereby improving the efficiency of coke oven waste heat power generation, while preventing the shutdown of the steam turbine generator set when the gas boiler steam fluctuates and the damage caused by long-term low-load operation of the high-parameter, high-capacity generator set.

[0006] To achieve the above-mentioned purpose, the present invention provides the following technical solution: a coke-electricity coupled coal-gas cogeneration power generation system, comprising a coke oven waste heat boiler, a coal gas boiler and a steam turbine generator set, wherein the coke oven waste heat boiler and the coal gas boiler are respectively connected to the steam turbine generator set, and the coke oven waste heat boiler and / or the coal gas boiler drive the steam turbine generator set to operate.

[0007] Optionally, the steam turbine generator set includes a high-pressure cylinder and a low-pressure cylinder connected to each other, and the high-pressure cylinder is connected to the main steam outlet of the coke oven waste heat boiler and the gas boiler respectively; it also includes a condenser, which is arranged between the low-pressure cylinder and the coke oven waste heat boiler and the gas boiler, and the low-pressure cylinder is connected to the condenser, and the condenser is connected to the water feed inlet of the coke oven waste heat boiler and the gas boiler respectively.

[0008] Optionally, the coke oven waste heat boiler includes a coking reheater, the gas boiler includes a gas reheater, the coking reheater and the gas reheater are connected in parallel, and the exhaust port of the high-pressure cylinder is connected to the steam inlet of the low-pressure cylinder after passing through the coking reheater and the gas reheater respectively.

[0009] Optionally, a deaerator is further included, the condenser is connected to the liquid inlet of the deaerator, the liquid outlet of the deaerator is respectively connected to the coke oven waste heat boiler and the gas boiler, an exhaust port is provided on the low-pressure cylinder, and the steam inlet of the deaerator is connected to the exhaust port of the low-pressure cylinder.

[0010] Optionally, a condensate pump is arranged between the condenser and the deaerator, and a boiler feed water pump is arranged between the deaerator and the coke oven waste heat boiler and the gas boiler. The condenser is connected to the deaerator through the condensate pump, and the deaerator is connected to the coke oven waste heat boiler and the gas boiler respectively through the boiler feed water pump.

[0011] Optionally, the coke oven waste heat boiler includes a low-pressure steam drum, the liquid outlet of the deaerator is connected to the feed water inlet of the low-pressure steam drum, and the steam outlet of the low-pressure steam drum is connected to the steam inlet of the deaerator.

[0012] Optionally, the steam inlet of the deaerator is connected to the steam exhaust port of the high-pressure cylinder, a pressure regulating valve group is provided between the high-pressure cylinder and the deaerator, and the deaerator is connected to the high-pressure cylinder through the pressure regulating valve group.

[0013] Optionally, the steam turbine of the steam turbine generator set is a high-parameter steam turbine, whose pressure parameter is ≥13.7MPa, temperature parameter is ≥540°C, and reheating technology is adopted.

[0014] Optionally, the capacity of the steam turbine generator set is ≥45MW.

[0015] Optionally, the coke oven waste heat boiler and the gas boiler are both provided with a denitrification system in the furnace; the coke oven waste heat boiler and the gas boiler are both provided with a desulfurization system after the furnace;

[0016] Optionally, the boiler feed water pump is provided with an intermediate tap, the feed water inlet of the low-pressure steam drum is connected to the intermediate tap of the boiler feed water pump, and a feed water regulating valve is provided between the low-pressure steam drum and the boiler feed water pump.

[0017] Optionally, the coke oven waste heat boiler adopts a mixed denitration method of SCR and SNCR in the furnace.

[0018] Optionally, a plurality of the coke oven waste heat boilers share desulfurization or share desulfurization with a gas boiler.

[0019] Optionally, the economizer of the coke oven waste heat boiler is made of ND steel or other corrosion-resistant materials.

[0020] Optionally, a shut-off valve is provided at the main steam outlet of the coke oven waste heat boiler and the gas boiler.

[0021] Optionally, shut-off valves are provided at the inlet and outlet of the coking reheater and the coal gas reheater.

[0022] Optionally, shut-off valves are provided at the feed water inlets of the coke oven waste heat boiler and the gas boiler.

[0023] A control method for a coke-electricity coupled coal-gas cogeneration power generation system provides a coke-electricity coupled coal-gas cogeneration power generation system as any of the above items, when the gas boiler load rate is ≥90%, the coke oven waste heat boiler operates at a constant pressure; when the gas boiler load rate is between 50% and 90%, the coke oven waste heat boiler operates at a sliding pressure; when the gas boiler load rate is ≤50%, the coke oven waste heat boiler operates at a constant pressure.

[0024] The beneficial effects of the present invention are as follows: (1) The coke oven waste heat boiler and the coal gas boiler are respectively connected to the steam turbine generator set. The coke oven waste heat boiler and / or the coal gas boiler drive the steam turbine generator set to operate and generate electricity. They can drive the large-capacity, high-parameter steam turbine generator set to generate electricity, thereby improving the power generation efficiency and preventing the high-parameter, high-capacity generator set from being damaged due to long-term low-load operation. The coke oven waste heat boiler and the coal gas boiler share a set of steam turbine generator sets, thereby reducing the number of equipment and the floor space, reducing the number of operating personnel, and reducing labor costs. (2) The middle tap of the boiler feed water pump supplies water to the low-pressure drum of the coke oven waste heat boiler. The low-pressure drum can provide steam to the deaerator, thereby increasing the steam source of the deaerator and increasing the stability of the system. (3) In the present invention, the denitrification in the furnace is arranged before the economizer, and the desulfurization is arranged after the furnace. The flue gas characteristics of the coke oven waste heat boiler are utilized to treat the flue gas so that the flue gas meets the environmental emission requirements.

[0025] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0027] Figure 1 This is a schematic diagram of a cogeneration power generation system coupled with coal gas.

[0028] Figure numerals: coke oven waste heat boiler 1, gas boiler 2, steam turbine generator set 3, high-pressure cylinder 4, low-pressure cylinder 5, condenser 6, deaerator 7, condensate pump 8, boiler feed water pump 9, pressure regulating valve group 10, gas reheater 11, coking reheater 12, low-pressure steam drum 13, feed water regulating valve 14, coke oven waste heat boiler main steam outlet 15, gas boiler main steam outlet 16. DETAILED DESCRIPTION

[0029] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0030] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0031] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "rear", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0032] See also Figure 1 , which is a coke-electricity-coupling coal-gas cogeneration power generation system, including a coke oven waste heat boiler 1, a coal gas boiler 2, a steam turbine generator set 3, a condenser 6 and a deaerator 7. The steam turbine generator set 3 includes a high-pressure cylinder 4 and a low-pressure cylinder 5 that are interconnected. The high-pressure cylinder 4 is respectively connected to the main steam outlet 15 of the coke oven waste heat boiler and the main steam outlet 16 of the coal gas boiler. The coke oven waste heat boiler 1 includes a coking reheater 12, and the coal gas boiler 2 includes a coal gas reheater 11. The coking reheater 12 and the coal gas reheater 11 are connected in parallel. The exhaust port of the high-pressure cylinder 4 is connected to the steam inlet of the low-pressure cylinder 5 after passing through the coking reheater 12 and the coal gas reheater 11. The condenser 6 is arranged between the low-pressure cylinder 5 and the coke oven waste heat boiler 1 and the coal gas boiler 2. The exhaust port of the low-pressure cylinder 5 is connected to the condenser 6, and the condenser 6 is respectively connected to the feed water inlet of the coke oven waste heat boiler 1 and the coal gas boiler 2.

[0033] The condenser 6 is connected to the liquid inlet of the deaerator 7, and the liquid outlet of the deaerator 7 is connected to the coke oven waste heat boiler 1 and the gas boiler 2 respectively. An exhaust port is provided on the low-pressure cylinder 5, and the steam inlet of the deaerator 7 is connected to the exhaust port of the low-pressure cylinder 5.

[0034] A condensate pump 8 is provided between the condenser 6 and the deaerator 7, a boiler feed water pump 9 is provided between the deaerator 7 and the coke oven waste heat boiler 1 and the gas boiler 2, the condenser 6 is connected to the deaerator 7 through the condensate pump 8, and the deaerator 7 is respectively connected to the coke oven waste heat boiler 1 and the gas boiler 2 through the boiler feed water pump 9. The coke oven waste heat boiler 1 includes a low-pressure drum 13, the liquid outlet of the deaerator 7 is connected to the water feed inlet of the low-pressure drum 13, and the steam outlet of the low-pressure drum 13 is connected to the steam inlet of the deaerator 7. The steam inlet of the deaerator 7 is connected to the exhaust port of the high-pressure cylinder 4, a pressure regulating valve group 10 is provided between the high-pressure cylinder 4 and the deaerator 7, and the deaerator 7 is connected to the high-pressure cylinder 4 through the pressure regulating valve group 10.

[0035] A denitrification system is provided inside the coke oven waste heat boiler 1 and the gas boiler 2; a desulfurization system is provided behind the coke oven waste heat boiler 1 and the gas boiler 2; the boiler feed water pump 9 is provided with an intermediate tap, the feed water inlet of the low-pressure steam drum 13 is connected to the intermediate tap of the boiler feed water pump 9, and a feed water regulating valve 14 is provided between the low-pressure steam drum 13 and the boiler feed water pump 9.

[0036] The coke oven waste heat boiler 1 adopts a mixed denitration method of SCR and SNCR in the furnace, SCR is selective catalytic reduction, and SNCR is selective non-catalytic reduction. Multiple coke oven waste heat boilers 1 use a common desulfurization or share desulfurization with the gas boiler 2. The flue gas temperature entering the waste heat boiler from the coke oven is 1050±50℃, and the exhaust temperature of the flue gas passing through the coke oven waste heat boiler 11 is 180℃. The flue gas temperature before the economizer fully meets the use conditions of the high-temperature catalyst. After denitration, the flue gas enters the post-furnace desulfurization system for desulfurization. Ensure that the flue gas emissions from the coke oven waste heat boiler 11 meet the emission standards.

[0037] The economizer of the coke oven waste heat boiler 1 is made of ND steel or other corrosion-resistant materials. ND steel is 09CrCuSb alloy, which is an alloy steel widely used in preheaters and heat exchangers. The main steam outlet 15 of the coke oven waste heat boiler and the main steam outlet 16 of the gas boiler are both provided with shut-off valves. The inlet and outlet of the coking reheater 12 and the gas reheater 11 are both provided with shut-off valves. The feed water inlet of the coke oven waste heat boiler 1 and the gas boiler 2 is provided with a shut-off valve.

[0038] When the coke oven waste heat boiler 1 and the coal gas boiler 2 are in operation, high-pressure steam is transported from the main steam outlet of the coke oven waste heat boiler 1 and the main steam outlet of the coal gas boiler 2 to the high-pressure cylinder 4 of the steam turbine generator set 3, driving the generator to generate electricity. The steam in the high-pressure cylinder 4 after completing the work is respectively sent to the coking reheater 12 of the coke oven waste heat boiler 1 and the coal gas reheater 11 of the coal gas boiler 2 through pipelines for reheating, and the reheated steam enters the low-pressure cylinder 5 of the steam turbine generator set 3, driving the generator to generate electricity.

[0039] The steam discharged from the low-pressure cylinder 5 enters the condenser 6 and condenses into liquid water in the condenser 6. The condensate pump 8 sends the liquid water condensed in the condenser 6 to the deaerator 7 for deoxygenation. The steam inlet of the deaerator 7 is connected to the air extraction port of the low-pressure cylinder 5, and part of the steam in the low-pressure cylinder 5 enters the deaerator 7 for deoxygenation. The liquid water deoxygenated in the deaerator 7 enters the coke oven waste heat boiler 1 and the gas boiler 2 respectively under the action of the boiler feed water pump 9, and becomes steam after being heated, and is continuously transported to the steam turbine generator set 3 for cyclic power generation.

[0040] The boiler feed water pump 9 is provided with an intermediate tap, and a low-pressure drum 13 is provided in the coke oven waste heat boiler 1. Part of the liquid water enters the low-pressure drum 13 from the intermediate tap and is heated into steam in the low-pressure drum 13. The steam outlet of the low-pressure drum 13 is connected to the steam inlet of the deaerator 7. A feed water regulating valve 14 is provided between the boiler feed water pump 9 and the low-pressure drum 13. The feed water regulating valve 14 can adjust the amount of water entering the low-pressure drum 13, thereby controlling the amount of steam generated by the low-pressure drum 13. The steam inlet of the deaerator 7 is also connected to the exhaust port of the high-pressure cylinder 4. A pressure regulating valve group 10 is provided between the high-pressure cylinder 4 and the deaerator 7. The pressure regulating valve group 10 can adjust the pressure of the steam discharged from the high-pressure cylinder 4 to be suitable for the use of the deaerator 7.

[0041] When the load fluctuation of the gas boiler 2 causes the turbine to reduce its load, and the steam in the low-pressure cylinder 5 cannot meet the operating set pressure value of the deaerator 7, the higher-pressure steam discharged from the low-pressure drum 13 and the high-pressure cylinder 4 can provide steam for the deaerator 7, thereby improving the operating stability of the deaerator 7.

[0042] During actual production of the coke-electricity coupled coal-gas cogeneration power generation system, when the load rate of the gas boiler 2 is ≥90%, the steam parameters of the coke oven waste heat boiler 1 match the steam parameters of the gas boiler 2, the coke oven waste heat boiler 1 operates at a constant pressure, and the steam turbine generator set 3 generates electricity at full load, with high power generation efficiency and large power generation capacity.

[0043] When the load rate of the gas boiler 2 is between 50% and 90%, the steam parameters of the coke oven waste heat boiler 1 are adjusted to match the steam parameters of the gas boiler 2, and the coke oven waste heat boiler 1 operates at sliding pressure to generate partial load power by the steam turbine generator set 3, with high power generation efficiency and large power generation capacity.

[0044] When the load rate of the gas boiler 2 is ≤50%, the coke oven waste heat boiler 1 operates at a constant pressure, and the steam turbine generator set 3 generates electricity at half load, with high power generation efficiency and less power generation.

[0045] The coke oven waste heat boiler 1 and the gas boiler 2 are connected to the steam turbine generator set 3 respectively, and the coke oven waste heat boiler 1 and the gas boiler 2 drive the steam turbine generator set 3 to operate. The steam turbine of the steam turbine generator set 3 is a high-parameter steam turbine, and its pressure parameter is ≥13.7MPa and its temperature parameter is ≥540℃. The capacity of the steam turbine generator set 3 is 50MW. The use of high-parameter and large-capacity steam turbines can improve the power generation efficiency, and the gas boiler 2 can provide additional steam to prevent the high-parameter and high-capacity generator set from being damaged due to long-term low-load operation. The coke oven waste heat boiler 1 can provide stable steam to keep the steam turbine generator set 3 running. When the steam volume of the gas boiler 2 is small, the steam turbine generator set 3 can still operate at a low load to prevent the steam turbine generator set 3 from stopping, and reduce the repair and maintenance costs caused by the stoppage of the steam turbine generator set 3.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A control method for a coke-electricity coupled coal-gas cogeneration power generation system, characterized in that: The coke-electricity-coal-gas cogeneration power generation system comprises a coke oven waste heat boiler, a gas boiler and a steam turbine generator set, wherein the coke oven waste heat boiler and the gas boiler are respectively connected to the steam turbine generator set, and the coke oven waste heat boiler and / or the gas boiler drive the steam turbine generator set to operate; When the gas boiler load rate is ≥90%, the coke oven waste heat boiler operates at a constant pressure; when the gas boiler load rate is between 50% and 90%, the coke oven waste heat boiler operates at a sliding pressure; when the gas boiler load rate is ≤50%, the coke oven waste heat boiler operates at a constant pressure.

2. The control method according to claim 1, characterized in that: The steam turbine generator set comprises a high-pressure cylinder and a low-pressure cylinder which are connected to each other, and the high-pressure cylinder is connected to the main steam outlet of the coke oven waste heat boiler and the gas boiler respectively; It also includes a condenser, which is arranged between the low-pressure cylinder and the coke oven waste heat boiler and the gas boiler. The low-pressure cylinder is connected to the condenser, and the condenser is connected to the water inlet of the coke oven waste heat boiler and the gas boiler respectively.

3. The control method according to claim 2, characterized in that: The coke oven waste heat boiler includes a coking reheater, the gas boiler includes a gas reheater, the coking reheater is connected in parallel with the gas reheater, and the exhaust port of the high-pressure cylinder is connected to the steam inlet of the low-pressure cylinder after passing through the coking reheater and the gas reheater respectively.

4. The control method according to claim 2, characterized in that: It also includes a deaerator, the condenser is connected to the liquid inlet of the deaerator, the liquid outlet of the deaerator is respectively connected to the coke oven waste heat boiler and the gas boiler, and an exhaust port is provided on the low-pressure cylinder, and the steam inlet of the deaerator is connected to the exhaust port of the low-pressure cylinder.

5. The control method according to claim 4, characterized in that: A condensate pump is provided between the condenser and the deaerator, and a boiler feed water pump is provided between the deaerator and the coke oven waste heat boiler and the gas boiler. The condenser is connected to the deaerator through the condensate pump, and the deaerator is connected to the coke oven waste heat boiler and the gas boiler respectively through the boiler feed water pump.

6. The control method according to claim 4, characterized in that: The coke oven waste heat boiler comprises a low-pressure steam drum, the liquid outlet of the deaerator is connected to the water supply inlet of the low-pressure steam drum, and the steam outlet of the low-pressure steam drum is connected to the steam inlet of the deaerator.

7. The control method according to claim 4, characterized in that: The steam inlet of the deaerator is communicated with the steam exhaust port of the high-pressure cylinder. A pressure regulating valve group is arranged between the high-pressure cylinder and the deaerator. The deaerator is communicated with the high-pressure cylinder through the pressure regulating valve group.

8. The control method according to claim 1, characterized in that: The steam turbine of the steam turbine generator set is a high-parameter steam turbine.

9. The control method according to claim 1, characterized in that: The capacity of the steam turbine generator set is ≥45MW.

Images