An efficient waste-to-energy system coupled with a coal-fired power plant

Abstract

The invention discloses a high-efficiency garbage power generation system coupled with a coal-fired power plant, including: a coal-fired boiler; a garbage incineration boiler, wherein the main steam generated by the garbage incineration boiler is merged into the coal-fired boiler and mixed with the main steam generated by the coal-fired boiler and then output, and the flue gas generated by the garbage incineration boiler is mixed with the flue gas generated by the coal-fired boiler and then output as the total flue gas, and the exhaust temperature of the garbage incineration boiler is set to 140°C to 160°C; a power generation unit, wherein the power generation unit uses the steam output by the coal-fired boiler to generate electricity; a flue gas pretreatment unit, wherein the flue gas pretreatment unit pre-treats the flue gas generated by the garbage incineration boiler; a flue gas purification unit, wherein the flue gas purification unit purifies and discharges the total flue gas; and an air preheating unit, wherein the air preheating unit heats the cold air and provides hot air to the garbage incineration boiler, and the air preheating unit is a two-stage heating structure with a single-stage steam extraction. The invention can improve the efficiency of the garbage furnace and increase the power generation, which is beneficial to improving the overall environmental protection index and economy of the system.

Description

Technical Field

[0001] The present invention relates to the technical field of waste incineration treatment, and more particularly to a high-efficiency waste power generation system coupled with a coal-fired power plant. Background Art

[0002] With the improvement of people's living standards and the surge in the output of urban domestic waste, the trend of garbage siege is constantly expanding. The waste incineration power generation technology represented by grates and CFB boilers has developed into the mainstream technology for harmless waste treatment due to its advantages of small footprint, significant reduction and high resource utilization.

[0003] Most existing technologies treat garbage in a certain area around a waste incineration power plant by building a new one. However, due to the flue gas purification requirement for flue gas temperature, the flue gas temperature of the garbage incinerator is usually around 190°C, and the heat loss of the flue gas is large, so the boiler efficiency is low, usually around 80%. In the existing technology, the air preheater of the garbage incinerator needs to extract steam from the steam drum of the garbage incinerator, which will lead to a reduction in the main steam volume and affect the amount of power generated by garbage. On the other hand, due to the steam parameters of the steam extraction point, the steam extraction from the low-pressure cylinder of the steam turbine (usually 1.2MPa, 300°C) alone is not enough to meet the air preheating temperature requirements. The air preheater of the garbage incinerator needs to be designed with multi-stage steam extraction and a more complex structure.

[0004] Compared with building a new waste-to-energy plant, the technology of waste-to-energy coupled with coal-fired units has the advantages of low initial investment and small footprint, which is also in line with the national conditions of my country where coal-fired units are widely distributed. The existing waste-to-energy coupled with coal-fired unit power generation technology does not fully consider the differences between the flue gas purification systems of waste incinerators and coal-fired boilers, and directly introduces the untreated or incompletely treated flue gas from the waste heat furnace outlet into the coal-fired unit, which cannot effectively remove dioxins and heavy metals in the flue gas at the tail of the waste incinerator, which is likely to cause environmental problems. Summary of the invention

[0005] In view of the above problems existing in the prior art, the present invention provides a high-efficiency garbage power generation system coupled with a coal-fired power plant, which can improve the efficiency of garbage furnaces and increase power generation, thereby improving the overall environmental protection indicators and economy of the system.

[0006] To this end, the present invention provides a high-efficiency garbage power generation system coupled with a coal-fired power plant, the system comprising:

[0007] Coal-fired boilers;

[0008] A waste incineration boiler, wherein the main steam generated by the waste incineration boiler is fed into the coal-fired boiler and mixed with the main steam generated by the coal-fired boiler before being output, and the flue gas generated by the waste incineration boiler is mixed with the flue gas generated by the coal-fired boiler before being output as the total flue gas, wherein the exhaust gas temperature of the waste incineration boiler is controlled to be 140°C to 160°C;

[0009] A power generation unit, wherein the power generation unit generates electricity by using steam output from a coal-fired boiler;

[0010] A flue gas pre-treatment unit, which pre-treats the flue gas generated by the waste incineration boiler;

[0011] A flue gas purification unit, wherein the flue gas purification unit purifies the total flue gas and discharges the total flue gas;

[0012] An air preheating unit heats cold air and provides hot air to the waste incineration boiler. The air preheating unit is a two-stage heating structure with single-stage steam extraction.

[0013] Furthermore, the system also includes a steam metering unit arranged on the steam connecting pipe between the waste incineration boiler and the coal-fired boiler, and the steam metering unit includes a temperature measuring subunit, a pressure measuring subunit and a flow measuring subunit.

[0014] Furthermore, the flue gas pre-treatment unit includes an activated carbon injection subunit and a bag dust removal subunit.

[0015] Furthermore, a dry deacidification subunit capable of spraying a deacidification agent to control the acid dew point of the flue gas is also provided at the front end of the flue gas pre-treatment unit.

[0016] Furthermore, the power generation unit includes a steam turbine and a generator connected to the steam turbine, the steam turbine includes a cylinder, a condenser, a deaerator and a heater, the steam output by the coal-fired boiler enters the cylinder to do work, the exhaust steam enters the condenser to become condensed water and then passes through the heater and deaerator in sequence before returning to the waste incineration boiler and / or the coal-fired boiler.

[0017] Furthermore, a chimney is provided downstream of the flue gas purification unit.

[0018] Furthermore, the air preheating unit includes a preheater body, which includes a condensate section and a steam section arranged in sequence along the air flow direction, the steam source of the steam section is extraction steam from a coal-fired boiler or extraction steam from a steam turbine in a power generation unit, and the steam source of the condensate section is condensate from the steam section.

[0019] Furthermore, the air preheating unit also includes a flash tank connected to the preheater body, the condensate outlet of the steam section is connected to the flash tank, the condensate outlet of the flash tank is connected to the condensate section, and the condensate outlet of the condensate section is connected to the deaerator of the turbine in the power generation unit.

[0020] Compared with the existing conventional waste-to-energy system, the present invention has the following advantages:

[0021] 1) The exhaust gas temperature of the garbage incineration boiler in this system can be reduced by about 40°C compared with the existing technology, which can greatly improve the efficiency of the garbage incinerator, increase the power generation per unit of garbage, and have good system economy;

[0022] 2) The flue gas pre-treatment unit of this system is responsible for removing dioxins, heavy metals and dust from the flue gas. At the same time, a dry deacidification unit is set up. The flue gas outlet of the flue gas pre-treatment unit is introduced into the flue gas purification system unit downstream of the coal-fired unit for deacidification and denitrification. It can take into account the characteristics of flue gas purification of garbage incinerators and coal-fired units. The overall environmental protection index of the system is excellent;

[0023] 3) The air preheating unit in this system is a single-stage steam source structure. The air preheating temperature requirement can be met by only extracting steam from the coal-fired unit (extracting steam from the coal-fired boiler or from the steam turbine). The structure is simple and the preheating air does not need to consume the heat of garbage combustion, which can further increase the unit garbage power generation;

[0024] 4) The waste incineration boiler of this system shares the power generation system and flue gas purification unit with the coal-fired unit, which can significantly reduce the initial investment and land occupation of the waste incinerator side;

[0025] 5) This system is equipped with a metering unit at the steam outlet of the waste incineration boiler, which can obtain the main steam parameters of the waste incineration boiler based on the measurement and calculate the waste power generation, which is convenient for the implementation of subsequent policies such as waste disposal fees and power generation subsidies. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic structural diagram of a high-efficiency waste-to-energy system coupled with a coal-fired power plant according to an exemplary embodiment of the present invention is shown.

[0027] Figure 2 A schematic diagram of the structure and flow of an air preheating unit in a high-efficiency waste-to-energy system coupled with a coal-fired power plant according to an exemplary embodiment of the present invention is shown.

[0028] Description of reference numerals:

[0029] 1-waste incineration boiler, 2-metering unit, 3-coal-fired boiler, 4-steam turbine, 5-generator, 6-flue gas pretreatment unit, 7-flue gas purification unit, 8-chimney, 9-air preheating unit, 91-condensate section, 92-steam section, 93-flash tank. DETAILED DESCRIPTION

[0030] All features disclosed in this specification, or steps in all methods or processes disclosed, except mutually exclusive features and / or steps, can be combined in any manner.

[0031] Any feature disclosed in this specification, unless otherwise stated, can be replaced by other equivalent or alternative features with similar purposes. That is, unless otherwise stated, each feature is only an example of a series of equivalent or similar features.

[0032] Based on the problems in the prior art, the present invention proposes a high-efficiency waste power generation system for a coupled coal-fired power plant in which a waste incineration boiler and a coal-fired boiler share a power generation unit, a flue gas purification unit and a chimney, which can significantly reduce the initial investment and land occupation on the waste furnace side, and at the same time improve the economy of the system through structural optimization.

[0033] The high-efficiency garbage power generation system coupled with a coal-fired power plant of the present invention will be described in detail below.

[0034] Figure 1 A schematic structural diagram of a high-efficiency waste-to-energy system coupled with a coal-fired power plant according to an exemplary embodiment of the present invention is shown.

[0035] like Figure 1 As shown, according to an exemplary embodiment of the present invention, the high-efficiency waste power generation system coupled with a coal-fired power plant includes a coal-fired boiler 3, a waste incineration boiler 1, a power generation unit, a flue gas pretreatment unit 6, a flue gas purification unit 7 and an air preheating unit 9.

[0036] Among them, the coal-fired boiler 3 is a boiler that burns carbonaceous fuels such as coal and converts and utilizes the heat therein. It can be any coal-fired boiler in the prior art, and the main steam generated is used for power generation. The garbage incineration boiler 1 is a boiler that recovers the calorific value of garbage by incinerating garbage. It can adopt the existing grate furnace and other boiler types in the prior art. The garbage is fed into the boiler from the feed port and burned in the furnace. The high-temperature flue gas generated exchanges heat with the heating surface of the boiler and then flows out, which transfers heat to the feed water on the working medium side. The feed water absorbs the heat of the high-temperature flue gas in the boiler to generate main steam with specific parameters, which is then used for power generation.

[0037] In the present invention, the waste incineration boiler 1 and the coal-fired boiler 3 share the power generation unit and the flue gas purification unit and other equipment, which can greatly reduce the initial investment and land occupation of the waste incineration boiler side. According to the present invention, the main steam generated by the waste incineration boiler 1 is merged into the coal-fired boiler 3 and mixed with the main steam generated by the coal-fired boiler 3 before being output, and the flue gas generated by the waste incineration boiler 1 is merged into the tail flue of the coal-fired boiler 3 after pre-treatment and mixed with the flue gas generated by the coal-fired boiler 3 before being output. Among them, the exhaust temperature of the waste incineration boiler is set to 140℃ to 160℃.

[0038] Specifically, the power generation unit utilizes the steam output from the coal-fired boiler to generate electricity, which specifically includes a steam turbine 4 and a generator 5 connected to the steam turbine 4. The steam turbine 4 includes a cylinder, a condenser, a deaerator and a heater. The steam output from the coal-fired boiler enters the cylinder to perform work, and the exhaust steam enters the condenser to become condensed water and then passes through the heater and the deaerator in sequence before returning to the waste incineration boiler 1 and / or the coal-fired boiler 3 to continue the steam cycle.

[0039] Preferably, the system further comprises a steam metering unit 2 arranged on the steam connection pipe between the waste incineration boiler 1 and the coal-fired boiler 3, for real-time monitoring of the main steam parameters of the waste incineration boiler 1, and the steam metering unit 2 comprises a temperature measurement subunit, a pressure measurement subunit and a flow measurement subunit. Combined with the specific design parameters of the steam turbine 4 and the generator 5, the power generation generated by the main steam of the waste incineration boiler 1 doing work in the steam turbine 4 can be calculated.

[0040] The flue gas pretreatment unit 6 of the present invention is mainly used for removing dioxins, heavy metals and dust from the flue gas generated by the waste incineration boiler to avoid causing environmental problems. Preferably, the flue gas pretreatment unit 6 includes an activated carbon injection subunit and a bag dust removal subunit, which can be used to remove dioxins, heavy metals and dust. Furthermore, a dry deacidification interface can be left at the front end of the flue gas pretreatment unit, and a dry deacidification subunit capable of spraying a deacidification agent to control the flue gas acid dew point is provided. An appropriate amount of deacidification agent is sprayed as needed to reduce the flue gas acid dew point to prevent low-temperature corrosion. In addition, the flue gas acid dew point and the performance of each subunit in the flue gas pretreatment unit 6 are comprehensively considered, and the exhaust temperature of the waste incineration boiler is controlled to be 140°C to 160°C. If the original flue gas acid dew point of the waste incineration boiler 1 is high, it can be adjusted by the dry deacidification subunit of the flue gas pretreatment unit 6.

[0041] The flue gas at the outlet of the flue gas pre-treatment unit 6 is mixed with the flue gas of the coal-fired boiler and then enters the flue gas purification unit 7 as the total flue gas output by the coal-fired boiler for purification treatment, and is discharged into the chimney after meeting the emission standards. That is, the flue gas purification unit 7 purifies and discharges the total flue gas output by the coal-fired boiler 3, and it can further perform other purification processes such as deacidification and denitrification on the flue gas. Preferably, a chimney 8 is also provided downstream of the flue gas purification unit to discharge the flue gas after deacidification, denitrification and other treatments.

[0042] The air preheating unit 9 in the present invention is used to preheat the hot primary air and hot secondary air of the waste incineration boiler 1. The air preheating unit 9 heats the cold air and provides hot air to the waste incineration boiler. The air preheating unit used in the present invention is a two-stage heating structure with a single-stage steam extraction, which is conducive to simplifying the structure.

[0043] Figure 2A schematic diagram of the structure and flow of an air preheating unit in a high-efficiency waste-to-energy system coupled with a coal-fired power plant according to an exemplary embodiment of the present invention is shown.

[0044] like Figure 2 As shown, the air preheating unit 9 in the present invention includes a preheater body, which includes a condensate section 91 and a steam section 92 arranged in sequence along the air flow direction. The steam source of the steam section 92 is extraction steam from a coal-fired boiler or extraction steam from a steam turbine in a power generation unit, and the heating source of the condensate section 91 is condensate from the steam section 92.

[0045] Among them, the air preheating unit 9 also includes a flash tank 93 connected to the preheater body, the condensate outlet of the steam section 92 is connected to the flash tank 93, the condensate outlet of the flash tank 93 is connected to the condensate section 91, the condensate outlet of the condensate section 91 is connected to the deaerator of the steam turbine in the power generation unit to discharge condensate, and the hot air outlet of the air preheating unit 9 is connected to the waste incineration boiler 1.

[0046] The flue gas flow of this system is as follows: the combustion air is heated by the air preheating unit 9 and then sent to the waste incineration boiler 1. The waste is fed from the feed port and then burned in the waste incineration boiler 1. The high-temperature flue gas generated exchanges heat with the heating surface of the waste incineration boiler 1 and transfers heat to the working medium side. The cooled flue gas enters the flue gas pretreatment unit 6, and after the dioxins, heavy metals, dust and some acidic components are removed, it is led to the tail flue of the coal-fired boiler through the flue, mixed with the flue gas, and then sent to the flue gas purification unit 7. After purification, it is sent to the chimney 6 together and finally discharged into the atmosphere.

[0047] The steam-water process of this system is as follows: the feed water in the waste incineration boiler 1 absorbs the heat of the high-temperature flue gas to generate main steam with specific parameters, which is introduced into the appropriate position of the coal-fired boiler 3 through the steam connecting pipe, mixed with the main steam of the coal-fired boiler 3, and then sent to the cylinder of the steam turbine 4 to do work, thereby driving the generator 5 to generate electricity. The exhaust steam of the steam turbine 4 enters the condenser and becomes water, passes through the heater and deaerator in turn, and finally returns to the boiler through the feed water pump and other devices to continue the steam cycle.

[0048] The exhaust gas temperature of the garbage incineration boiler of this system can be reduced by about 50°C, which will greatly improve the efficiency of the garbage incineration boiler and the economy of the system. The air preheating unit of the garbage incineration boiler of this system is a single-stage steam extraction unit with a simple structure and helps to increase the power generation of the garbage incineration boiler; and this system only requires simple modifications to the boiler, turbine and flue gas purification unit of the coal-fired unit, which is convenient and easy to operate.

[0049] The present invention will be further described below in conjunction with specific embodiments.

[0050] Embodiment 1:

[0051] This embodiment couples the efficient waste-to-energy system of the coal-fired power plant to Figure 1 As shown, it includes components such as a waste incineration boiler 1, a metering unit 2, a coal-fired boiler 3, a steam turbine 4, a generator 5, a flue gas pretreatment unit 6, a flue gas purification unit 7, a chimney 8, and an air preheating unit 9.

[0052] The design parameters of the waste incineration boiler 1 are 2*400t / d, 2000Kcal / kg, medium temperature and sub-high pressure, and the coal-fired unit is a conventional 350MW subcritical unit.

[0053] Along the air / flue gas flow direction, the air preheating unit 9, the waste incineration boiler 1, the flue gas pretreatment unit 6, the flue gas purification unit 7 and the chimney 8 are connected in sequence. Along the steam flow direction, the waste incineration boiler 1, the metering unit 2, the coal-fired boiler 3 and the power generation unit are connected in sequence. The main steam generated by the waste incineration boiler 1 has its main steam parameters measured in the metering unit 2 and then introduced into the coal-fired boiler 3, such as an appropriate position of the reheat system.

[0054] The steam turbine 4 includes components such as a cylinder, a condenser, a deaerator, and a heater. The main steam parameters of the waste incineration boiler measured by the metering unit 2 include temperature, pressure, flow, etc. The corresponding enthalpy value is found out according to the temperature and pressure, and the main steam heat of the waste incineration boiler is calculated in combination with the main steam flow. Then, according to the exhaust parameters of the steam turbine 4 corresponding to the coal-fired unit, the steam turbine efficiency, etc., the power generation of the main steam of the garbage furnace 1 entering the steam turbine can be calculated.

[0055] The acid dew point of this system under the design working condition is 145℃, and the exhaust gas temperature is 150℃. In the flue gas pre-treatment unit 6, along the flue gas flow direction, the dry deacidification unit, the activated carbon injection unit, and the bag dust removal unit are connected in sequence, which can remove some acidic components, dioxins, heavy metals and dust in the flue gas at the outlet of the waste incineration boiler 1. After being treated by the dry deacidification unit, the flue gas acid dew point is reduced to 130℃. The emission of dioxins, heavy metals, dust, etc. in the pre-treated flue gas has reached the standard, and is introduced into the flue gas purification unit 7 through the connected flue for further purification.

[0056] The air preheating unit 9 is a tubular heat exchanger, and the air preheating temperature is set to 200°C. Its structure is as follows: Figure 2 As shown, the air preheating unit 9 includes a preheater body, a flash tank and connecting pipes. The preheater body is arranged with a condensate section and a steam section along the air flow direction. The steam source of the steam section comes from the low-pressure cylinder of the steam turbine 4, and the extraction parameters are 3.1MPa and 330℃. The condensate (3.1MPa, 235.7℃, saturated water) at the outlet of the steam section is reduced in pressure to 1.2MPa by the flash tank. After flashing, the steam is merged into the extraction steam and sent to the steam section. The condensate after flashing is sent back to the preheater body and used as the heat source of the condensate section. The condensate is exchanged with the cold air and cooled to a suitable temperature before being led to the deaerator of the steam turbine 4. Among them, the required steam extraction amount of the air preheating unit 9 can be calculated according to the heat balance equation.

[0057] Compared with the prior art, the exhaust gas temperature of this embodiment is reduced from 190°C to 150°C, and an additional 2500KW of heat can be recovered. In addition, the air preheating unit does not extract steam from the steam drum of the waste incineration boiler, which can further increase the main steam flow of the waste incineration boiler. According to calculations, the boiler efficiency of the waste incineration boiler can be increased by 3.2%, and the main steam flow entering the steam turbine can be increased by 5.3t / h.

[0058] In addition, there is no deacidification tower, SCR denitrification system and chimney on the waste incineration boiler side, which is conducive to saving land. Since the volume of the waste incineration boiler is relatively small compared to the coal-fired unit, the design fully considers the matching of the working fluid parameters of the waste incineration boiler with the parameters of the introduction point. The introduction of steam and flue gas has almost no effect on the operation of the coal-fired boiler, and the transformation of the coal-fired boiler side is easy to achieve. The main transformation contents include: adding the main steam interface of the waste incineration boiler on the boiler side, adding the extraction interface on the turbine side, and adding the flue gas interface of the waste incineration boiler to the economizer outlet flue.

[0059] Embodiment 2:

[0060] This embodiment provides a high-efficiency waste-to-energy system coupled to a coal-fired power plant similar to Embodiment 1.

[0061] The present embodiment is different from the embodiment 1 in that the acid dew point of the original flue gas in the present embodiment is 115°C, and thus the exhaust temperature under the design condition is reduced to 140°C, so that the waste heat of the flue gas can be further recovered, and the dry deacidification subunit in the flue gas pretreatment unit 6 can be cancelled or kept normally closed to save operating costs.

[0062] Embodiment 3:

[0063] This embodiment provides a high-efficiency waste-to-energy system coupled to a coal-fired power plant similar to Embodiment 1.

[0064] The present embodiment is different from the embodiment 1 in that the air preheating unit 9 is changed to extract steam from the low re-inlet of the coal-fired boiler 3, so that the modification of the steam side of the coal-fired unit is controlled within the coal-fired boiler 3, and the steam turbine 4 in the coal-fired unit does not need to be modified.

[0065] The effects of the present invention and the prior art are compared as shown in Table 1 below.

[0066] Table 1 Comparison of the effects of the present invention and the prior art

[0067]

[0068] In summary, the high-efficiency waste-to-energy system coupled with a coal-fired power plant of the present invention has the advantages of high unit waste power generation, excellent environmental protection indicators, simple system setting and low initial investment compared with existing solutions.

[0069] The present invention is not limited to the above-mentioned specific embodiments, but extends to any new features or any new combination disclosed in this specification, as well as any new method or process steps or any new combination disclosed.

Claims

1. A highly efficient waste-to-energy system coupled with a coal-fired power plant, characterized in that: The system comprises: Coal-fired boilers; A waste incineration boiler, wherein the main steam generated by the waste incineration boiler is fed into the coal-fired boiler and mixed with the main steam generated by the coal-fired boiler before being output, and the flue gas generated by the waste incineration boiler is mixed with the flue gas generated by the coal-fired boiler and output as the total flue gas, wherein the exhaust gas temperature of the waste incineration boiler is set to 140°C to 160°C; A power generation unit, wherein the power generation unit generates electricity by using steam output from a coal-fired boiler; A flue gas pre-treatment unit, which pre-treats the flue gas generated by the waste incineration boiler; A flue gas purification unit, wherein the flue gas purification unit purifies the total flue gas and discharges the total flue gas; An air preheating unit, which heats cold air and provides hot air to the waste incineration boiler, and is a two-stage heating structure with single-stage steam extraction; The system further comprises a steam metering unit arranged on a steam connection pipe between the waste incineration boiler and the coal-fired boiler, wherein the steam metering unit comprises a temperature measurement subunit, a pressure measurement subunit and a flow measurement subunit; The flue gas pre-treatment unit includes an activated carbon injection subunit and a bag dust removal subunit; The front end of the flue gas pre-treatment unit is also provided with a dry deacidification sub-unit capable of spraying a deacidification agent to control the flue gas acid dew point; The power generation unit includes a steam turbine and a generator connected to the steam turbine, the steam turbine includes a cylinder, a condenser, a deaerator and a heater, the steam output by the coal-fired boiler enters the cylinder to do work, the exhaust steam enters the condenser to become condensed water and then passes through the heater and the deaerator in sequence before returning to the waste incineration boiler and / or the coal-fired boiler; A chimney is also provided downstream of the flue gas purification unit; The air preheating unit comprises a preheater body, the preheater body comprises a condensate section and a steam section arranged in sequence along the air flow direction, the steam source of the steam section is extraction steam from a coal-fired boiler or extraction steam from a steam turbine in a power generation unit, and the steam source of the condensate section is condensate from the steam section; The air preheating unit also includes a flash tank connected to the preheater body, the condensate outlet of the steam section is connected to the flash tank, the condensate outlet of the flash tank is connected to the condensate section, and the condensate outlet of the condensate section is connected to the deaerator of the steam turbine in the power generation unit.

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