Manufacturing method of biomass derived fuel for gradient utilization of steam extraction and energy storage of large coal-fired boiler

Abstract

The invention relates to the technical field of fuel manufacturing, in particular to a manufacturing method of biomass derived fuel for steam extraction energy storage gradient utilization of a large coal-fired boiler, which comprises the following steps: S1, under a normal working condition, steam at an outlet of a boiler superheater enters a high-pressure cylinder to do work; and S2, under the peak-shaving low-load operation condition, the electric quantity of the power grid is excessive, and steam of the steam turbine is excessive. Through the fused salt energy storage module and a biomass pretreatment system for drying, baking, crushing, extruding, forming and the like of biomass, under the peak regulation working condition, the fused salt energy storage module is used for storing heat, the heat is provided for condensate water for heating, low-temperature waste heat steam at an outlet of a steam turbine provides heat for drying of the biomass, and therefore the heat efficiency of the system is improved; heat resources of power plant steam and boiler flue gas are fully utilized, energy consumption of biomass derived fuel manufacturing is reduced, and in addition, biomass baked by high-temperature flue gas is utilized to improve the crushing performance.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel manufacturing, and in particular to a method for manufacturing biomass-derived fuel for cascade utilization of steam extraction and energy storage in large coal-fired boilers. Background Art

[0002] my country's current energy consumption structure is primarily coal-based, and thermal power will continue to exist as a flexible peak-shaving power source in the country's power generation structure for a long time. Carbon emissions from coal-fired power generation account for 50% of my country's total carbon emissions. To achieve a low-carbon power system, coupling coal with biomass, and ultimately burning only biomass, is the primary focus of low-carbon retrofits for coal-fired units. The key to coupled combustion of biomass and coal in pulverized coal furnaces lies in the pulverization and transportation of the biomass. Currently, the equipment used to manufacture biomass-derived fuels consumes a lot of energy and fails to fully utilize the thermal resources of power plant steam and boiler flue gases. Summary of the Invention

[0003] The technical problem to be solved by the present invention is: in order to solve the technical problem of high energy consumption of existing biomass-derived fuel manufacturing equipment, the present invention provides a method for manufacturing biomass-derived fuel for cascade utilization of steam extraction and energy storage in large coal-fired boilers. By improving the manufacturing method, the energy consumption of biomass-derived fuel manufacturing can be reduced.

[0004] The technical solution adopted by the present invention to solve the technical problem is: a method for manufacturing biomass-derived fuel for cascade utilization of steam extraction energy storage in large coal-fired boilers, comprising the following steps:

[0005] S1. Under normal operating conditions, steam from the boiler superheater outlet enters the high-pressure cylinder to perform work;

[0006] S2. Under peak load operation, the grid has excess power and the turbine has excess steam;

[0007] The S2 comprises the following steps:

[0008] S2-1: Extract part of the steam from the high-pressure cylinder outlet to the molten salt energy storage module, where the steam heats the phase-change heat storage medium. The steam after heat exchange is then sent to the low-pressure cylinder to perform work.

[0009] S2-2, the steam from the low-pressure cylinder outlet goes to the dryer to dry the biomass, and then goes to the cooling tower to form condensed water. The condensed water enters the molten salt energy storage heat exchanger and then enters the superheater;

[0010] S2-3, extracting high-temperature flue gas from the power plant boiler between the bag filters and using the high-temperature characteristics of the high-temperature flue gas to roast the biomass;

[0011] S2-4, using an electrically driven pulverizer to pulverize biomass;

[0012] S2-5. Using an electrically driven extrusion molding machine to extrude biomass, and after extrusion, forming biomass-derived fuel.

[0013] Therefore, through the molten salt energy storage module and the biomass drying, baking, crushing, extrusion, molding and other biomass pretreatment systems, under peak-shaving conditions, the molten salt energy storage module is used to store heat, and this part of the heat is provided to the condensed water for heating and heating. The low-temperature waste heat steam at the steam turbine outlet provides heat for biomass drying, thereby improving the thermal efficiency of the system; making full use of the heat resources of power plant steam and boiler flue gas to reduce the energy consumption of biomass-derived fuel manufacturing. In addition, the biomass baked with high-temperature flue gas is used to improve the crushing performance. By controlling the ratio of garbage, straw and sludge, the form and calorific value of the biomass-derived fuel are made close to coal.

[0014] Furthermore, in S1, the temperature of the steam at the boiler superheater outlet is 500°C.

[0015] Furthermore, in S2-1, the temperature of part of the steam is 400°C.

[0016] Furthermore, in S2-1, the melting point of the phase change heat storage medium is 300°C-350°C;

[0017] The temperature of the steam after heat exchange is 300℃.

[0018] Furthermore, in S2-2, the temperature of the steam at the outlet of the low-pressure cylinder is 200°C, the temperature of the machine-dried biomass is 90°C, and the temperature of the condensed water is 40°C.

[0019] Furthermore, in S2-3, the high-temperature flue gas of the power plant boiler is 300°C-400°C.

[0020] Furthermore, in S2-3, the composition and properties of the biomass will change at a temperature of 300°C to 400°C.

[0021] Furthermore, in S2-3, the pyrolysis temperature of hemicellulose in the biomass is 200°C-315°C.

[0022] Furthermore, in S2-3, the pyrolysis temperature of cellulose in the biomass is 315°C-400°C.

[0023] Furthermore, in S2-3, the temperature of the low-temperature flue gas is 100°C-150°C, and the low-temperature flue gas carries the combustible gas generated by baking and returns to the boiler to assist combustion.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] Through the molten salt energy storage module and the biomass drying, baking, crushing, extrusion, molding and other biomass pretreatment systems, the molten salt energy storage module is used to store heat under peak-shaving conditions. This part of the heat is provided to the condensed water for heating and the low-temperature waste heat steam at the steam turbine outlet provides heat for biomass drying, thereby improving the thermal efficiency of the system; fully utilize the heat resources of power plant steam and boiler flue gas to reduce the energy consumption of biomass-derived fuel manufacturing. In addition, the biomass baked with high-temperature flue gas is used to improve the crushing performance. By controlling the ratio of garbage, straw and sludge, the form and calorific value of biomass-derived fuel are made close to coal. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present invention will be further described below with reference to the accompanying drawings and examples.

[0027] Figure 1 This is a flow chart of the method for producing biomass-derived fuel for cascade utilization of extracted steam energy storage in large coal-fired boilers according to the present invention;

[0028] Figure 2 This is a flow chart of S2 of the present invention;

[0029] Figure 3 This is a process flow chart for preparing biomass-derived fuel for cascade utilization of steam extraction energy storage in large coal-fired boilers according to the present invention. DETAILED DESCRIPTION

[0030] The present invention will now be described in further detail with reference to the accompanying drawings, which are simplified schematic diagrams that illustrate the basic structure of the present invention in a schematic manner.

[0031] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, features defined as "first" or "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0032] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0033] like Figures 1 to 3 FIG. 1 is a preferred embodiment of the present invention. The method for producing biomass-derived fuel for cascade utilization of steam extraction energy storage in large coal-fired boilers in this embodiment comprises the following steps:

[0034] S1. Under normal operating conditions, steam from the boiler superheater outlet enters the high-pressure cylinder to perform work;

[0035] S2. Under peak load operation, the grid has excess power and the turbine has excess steam;

[0036] The S2 comprises the following steps:

[0037] S2-1: Extract part of the steam from the high-pressure cylinder outlet to the molten salt energy storage module, where the steam heats the phase-change heat storage medium. The steam after heat exchange is then sent to the low-pressure cylinder to perform work.

[0038] S2-2, the steam from the low-pressure cylinder outlet goes to the dryer to dry the biomass, and then goes to the cooling tower to form condensed water. The condensed water enters the molten salt energy storage heat exchanger and then enters the superheater;

[0039] S2-3, extracting high-temperature flue gas from the power plant boiler between the bag filters and using the high-temperature characteristics of the high-temperature flue gas to roast the biomass;

[0040] S2-4, using an electrically driven pulverizer to pulverize biomass;

[0041] S2-5. Utilize an electrically driven extruder to extrude biomass, and after extrusion, form biomass-derived fuel. Thus, through the molten salt energy storage module and the biomass pretreatment system, including drying, torrefaction, crushing, extrusion, and molding, the molten salt energy storage module stores heat during peak-shaving conditions. This heat is then used to heat condensed water. Low-temperature waste steam from the steam turbine outlet provides heat for biomass drying, thereby improving system thermal efficiency. This fully utilizes the thermal resources of power plant steam and boiler flue gas to reduce energy consumption in biomass-derived fuel production. Furthermore, high-temperature flue gas torrefaction of biomass improves crushing performance. By controlling the ratio of garbage, straw, and sludge, the form and calorific value of the biomass-derived fuel approach those of coal.

[0042] Specifically, the cascade utilization of power plant steam and boiler flue gas heat resources is based on the principle of different uses for steam at different temperatures; under peak-shaving conditions, high-temperature steam uses molten salt energy storage modules to store heat, and low-temperature waste heat steam provides heat for biomass drying.

[0043] Specifically, in S2-2, the moisture content of the biomass after drying is reduced to less than 10%; in S2-4, the composition of the crushed biomass is more uniform, which is conducive to the subsequent production of molded fuel and ensures the stability of the molded fuel composition; in S2-5, the density of the biomass-derived fuel after molding is greater, which is conducive to transportation.

[0044] In this embodiment, in S1, the temperature of the steam at the boiler superheater outlet is 500°C.

[0045] In this embodiment, in S2-1, the temperature of part of the steam is 400°C; the melting point of the phase-change heat storage medium is 300°C-350°C; and the temperature of the steam after heat exchange is 300°C.

[0046] In this embodiment, in S2-2, the temperature of the steam at the outlet of the low-pressure cylinder is 200°C, the temperature of the machine-dried biomass is 90°C, and the temperature of the condensed water is 40°C.

[0047] In this embodiment, in S2-3, the high-temperature flue gas from the power plant boiler is 300°C-400°C. At temperatures between 300°C and 400°C, the composition and properties of biomass change. The pyrolysis temperature of hemicellulose in biomass is between 200°C and 315°C, and the pyrolysis temperature of cellulose in biomass is between 315°C and 400°C. The temperature of the low-temperature flue gas is between 100°C and 150°C, carrying combustible gases produced by torrefaction and returning to the boiler to assist combustion. Specifically, because both hemicellulose and cellulose undergo varying degrees of pyrolysis, the biomass composition changes, reducing the carbon and hydrogen content, and pyrolysis produces combustible gases such as carbon monoxide, hydrogen, and methane.

[0048] In summary, the present invention uses a molten salt energy storage module and a biomass pretreatment system for drying, baking, crushing, extruding, and molding biomass. Under peak-shaving conditions, the molten salt energy storage module is used to store heat, and this heat is provided to the condensed water for heating and heating. The low-temperature waste heat steam at the steam turbine outlet provides heat for biomass drying, thereby improving the thermal efficiency of the system; making full use of the heat resources of power plant steam and boiler flue gas to reduce the energy consumption of biomass-derived fuel production. In addition, the biomass baked with high-temperature flue gas is used to improve the crushing performance. By controlling the ratio of garbage, straw, and sludge, the form and calorific value of the biomass-derived fuel are close to those of coal.

[0049] The above description is intended to serve as a guide for the preferred embodiments of the present invention. Based on the above description, relevant personnel are fully capable of making various changes and modifications without departing from the technical scope of the present invention. The technical scope of the present invention is not limited to the contents of the specification and must be determined according to the scope of the claims.

Claims

1. A method for producing biomass-derived fuel for cascade utilization of steam extraction and energy storage in large coal-fired boilers, characterized in that: The following steps are involved: S1. Under normal operating conditions, steam from the boiler superheater outlet enters the high-pressure cylinder to perform work; S2. Under peak load operation, the grid has excess power and the turbine has excess steam; The S2 comprises the following steps: S2-1: Extract part of the steam from the high-pressure cylinder outlet to the molten salt energy storage module, where the steam heats the phase-change heat storage medium. The steam after heat exchange is then sent to the low-pressure cylinder to perform work. S2-2, the steam from the low-pressure cylinder outlet goes to the dryer to dry the biomass, and then goes to the cooling tower to form condensed water. The condensed water enters the molten salt energy storage heat exchanger and then enters the superheater; S2-3, extracting high-temperature flue gas from the power plant boiler between the bag filters and using the high-temperature characteristics of the high-temperature flue gas to roast the biomass; S2-4, using an electrically driven pulverizer to pulverize biomass; S2-5. Using an electrically driven extrusion molding machine to extrude biomass, and after extrusion, forming biomass-derived fuel.

2. The method for producing biomass-derived fuel for cascade utilization of steam extraction energy storage in large coal-fired boilers according to claim 1, characterized in that: In S1, the temperature of the steam at the boiler superheater outlet is 500℃.

3. The method for producing biomass-derived fuel for cascade utilization of steam extraction energy storage in large coal-fired boilers according to claim 1, characterized in that: In S2-1, the temperature of part of the steam is 400°C.

4. The method for producing biomass-derived fuel for cascade utilization of steam extraction energy storage in large coal-fired boilers according to claim 1, characterized in that: In S2-1, the melting point of the phase change heat storage medium is 300°C-350°C; The temperature of the steam after heat exchange is 300℃.

5. The method for producing biomass-derived fuel for cascade utilization of steam extraction energy storage in large coal-fired boilers according to claim 1, characterized in that: In S2-2, the temperature of the steam at the outlet of the low-pressure cylinder is 200°C, the temperature of the machine-dried biomass is 90°C, and the temperature of the condensed water is 40°C.

6. The method for producing biomass-derived fuel for cascade utilization of steam extraction energy storage in large coal-fired boilers according to claim 1, characterized in that: In S2-3, the high-temperature flue gas from the power plant boiler is 300℃-400℃.

7. The method for producing biomass-derived fuel for cascade utilization of steam extraction energy storage in large coal-fired boilers according to claim 1, characterized in that: In S2-3, the composition and properties of biomass will change at a temperature of 300℃-400℃.

8. The method for producing biomass-derived fuel for cascade utilization of steam extraction energy storage in large coal-fired boilers according to claim 1, characterized in that: In S2-3, the pyrolysis temperature of hemicellulose in the biomass is 200°C-315°C.

9. The method for producing biomass-derived fuel for cascade utilization of steam extraction energy storage in large coal-fired boilers according to claim 1, characterized in that: In S2-3, the cellulose in the biomass is pyrolyzed at a temperature of 315°C to 400°C.

10. The method for producing biomass-derived fuel for cascade utilization of steam extraction energy storage in large coal-fired boilers according to claim 1, characterized in that: In S2-3, the temperature of the low-temperature flue gas is 100℃-150℃. The low-temperature flue gas carries the combustible gas generated by baking and returns to the boiler to assist combustion.

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