Closed-loop control system for fuel distribution regulation in large-scale co-firing of biomass in coal-fired units

Abstract

The invention discloses a closed-loop control system for fuel distribution regulation in large-scale co-firing of biomass in coal-fired units, which includes a first Roots blower, a first air flow emitter, a second Roots blower, a second air flow emitter, a biomass fuel input pipeline, a distributor, a first equalizing device, a second equalizing device and a DCS control system. This system can adjust the biomass powder quantity and air volume deviation in each biomass powder pipeline to ensure that the pulverized coal quantity in the furnace is always evenly distributed.

Description

Technical Field

[0001] The invention belongs to the field of biomass co-firing, and relates to a closed-loop control system for fuel distribution regulation for large-scale biomass co-firing in coal-fired power units. Background Art

[0002] The technology of biomass direct combustion coupled with coal-fired power units started relatively late in China and is more maturely applied abroad. A complete biomass co-firing system includes a discharging unit, a screening unit, a silo storage unit, a furnace front bin and a coal pulverizing unit, a biomass powder transportation and coupling unit, conveying equipment between each unit, etc. Among them, the biomass pulverizing and coupling unit directly affects the operation state of the original coal-fired power unit, so it is crucial. At present, for the fuel distribution regulation of the biomass powder pulverizing and coupling unit, the commonly adopted solution at home and abroad is that the biomass powder falls into the outlet of the Roots blower and is blown into the primary air pipe. The primary air pipe is divided into two by a bifurcated pipe in front of the furnace and enters the original pulverized coal pipeline or burner.

[0003] For coal-fired power units, when large-scale biomass co-firing is carried out, it is crucial to ensure the uniform distribution of biomass powder in each burner. If the distribution deviation of biomass powder in each burner is large, it will lead to a series of problems such as uneven burning in the furnace, local overheating, local coking, serious local high-temperature corrosion, increased NOX, and easy deposition and blockage of individual biomass powder pipes, affecting the safe and environmental protection operation of the original coal-fired boiler. For coal-fired power units, the pulverized coal distribution at the outlet of the direct-fired pulverizing system mainly relies on a rotary separator or a diffuser or a distributor to ensure, and a lot of research and development and improvement have been done on the distributor. However, for the biomass co-firing system, there is no air supply in the biomass mill, and the biomass powder in the mill falls into the air supply system by gravity. Moreover, the biomass powder is filamentous, lighter than pulverized coal particles, has good followability with the air flow, small inertia force, and is easy to hang wire. Limited by the physical properties of the biomass powder, its fuel distribution regulation system cannot draw on the rotary separator and various types of distributors of coal-fired power units.

[0004] After various types of distributors are installed at present, after the commissioning personnel adjust the pulverized coal amount and the wind speed deviation to be appropriate, the baffle opening remains unchanged during operation. However, during the process of changing coal quality, different working conditions, and rapid load increase and decrease, there are certain differences in the pulverized coal amount and the wind speed deviation. The fixed baffle opening for adjusting the pulverized coal amount and the air volume cannot ensure that the pulverized coal amount in the furnace is always evenly distributed. For large-scale biomass co-firing in coal-fired power units, the distribution deviation of biomass powder and wind speed is also affected by the characteristics of biomass feedstock, output, etc. Summary of the Invention

[0005] The purpose of the invention is to overcome the above-mentioned shortcomings of the prior art and provide a closed-loop control system for fuel distribution regulation for large-scale biomass co-firing in coal-fired power units, which can adjust the biomass powder amount and the wind volume deviation in each biomass powder pipeline to ensure that the pulverized coal amount in the furnace is always evenly distributed.

[0006] To achieve the above object, the closed-loop control system for fuel distribution regulation for large-scale co-firing of biomass in coal-fired units according to the present invention includes a first Roots blower, a first air flow emitter, a second Roots blower, a second air flow emitter, a biomass fuel input pipeline, a distributor, a first equalizing device, a second equalizing device and a DCS control system;

[0007] The outlet of the first Roots blower is communicated with the inlet of the first air flow emitter, the outlet of the second Roots blower is communicated with the inlet of the second air flow emitter, the biomass fuel input pipeline is communicated with the inlet of the distributor, the outlet of the distributor is communicated with the inlet of the first air flow emitter and the inlet of the second air flow emitter, the outlet of the first air flow emitter is communicated with the inlet of the first equalizing device through a first main powder pipe, the outlet of the second air flow emitter is communicated with the inlet of the second equalizing device through a second main powder pipe, the two outlets of the first equalizing device are respectively communicated with a first branch pipe and a second branch pipe, and the two outlets of the second equalizing device are respectively communicated with a third branch pipe and a fourth branch pipe;

[0008] On the first branch pipe, the second branch pipe, the third branch pipe and the fourth branch pipe, there are respectively installed on-line measuring devices for air and powder in the branch pipes; on the first main powder pipe and the second main powder pipe, there are respectively installed on-line measuring devices for air and powder in the main pipes; the on-line measuring devices for air and powder in the branch pipes and the on-line measuring devices for air and powder in the main pipes are communicated with the DCS control system;

[0009] The DCS control system is connected to the control end of the distributor, the control end of the first Roots blower, the control end of the second Roots blower, the control end of the first equalizing device and the control end of the second equalizing device.

[0010] The biomass fuel input pipeline is communicated with the inlet of the distributor through a weighing belt feeder. The outlet of the distributor is communicated with the inlet of the first air flow emitter through a first hammer mill

[0011] The outlet of the distributor is communicated with the inlet of the second air flow emitter through a second hammer mill.

[0012] The outlets of the first air flow emitter and the second air flow emitter are connected through a pipe and then communicated with the inlets of the first equalizing device and the second equalizing device through a main powder pipe.

[0013] The on-line measuring device for air and powder in the branch pipe is communicated with the DCS control system through a branch pipe signal processor.

[0014] The on-line measuring device for air and powder in the main pipe is communicated with the DCS control system through a main pipe signal processor.

[0015] It also includes a furnace, a first biomass co-firing coupler, a second biomass co-firing coupler, a third biomass co-firing coupler, and a fourth biomass co-firing coupler; the outlet of the first equalizing device is connected to the inlet of the first biomass co-firing coupler through a first branch pipe, the outlet of the first equalizing device is connected to the inlet of the second biomass co-firing coupler through a second branch pipe, the outlet of the second equalizing device is connected to the inlet of the third biomass co-firing coupler through a third branch pipe, and the outlet of the second equalizing device is connected to the inlet of the fourth biomass co-firing coupler through a fourth branch pipe;

[0016] The first biomass co-firing coupler, the second biomass co-firing coupler, the third biomass co-firing coupler, and the fourth biomass co-firing coupler are connected to the furnace.

[0017] The present invention has the following beneficial effects:

[0018] When the closed-loop control system for fuel distribution regulation of large-scale biomass co-firing in a coal-fired unit described in the present invention is in specific operation, the DCS control system measures the wind speed and pulverized coal concentration signals of the air-pulverized coal in the first main pulverized coal pipe and the second main pulverized coal pipe through the main pipe air-pulverized coal online measuring device 16, measures the wind speed and pulverized coal concentration signals of the air-pulverized coal in the first branch pipe, the second branch pipe, the third branch pipe, and the fourth branch pipe through the branch pipe air-pulverized coal online measuring device, and controls the distributor, the first Roots blower, the second Roots blower, the first equalizing device, and the second equalizing device based on this, so that the wind speed and pulverized coal concentration in the first branch pipe, the second branch pipe, the third branch pipe, and the fourth branch pipe are balanced, to adjust the biomass powder amount and air volume deviation in each biomass powder pipeline, ensure that the pulverized coal amount in the furnace is always evenly distributed, increase the biomass co-firing ratio, and reduce the local corrosion and coking problems after biomass co-firing. Description of the Drawings

[0019] Figure 1 It is a schematic structural diagram of the present invention.

[0020] Among them, 1 is a weighing belt feeder, 2 is a distributor, 3 is a first hammer mill, 4 is a second hammer mill, 5 is a first air emitter, 6 is a second air emitter, 7 is a first Roots blower, 8 is a second Roots blower, 9 is a first equalizing device, 10 is a second equalizing device, 11 is a first biomass co-firing coupler, 12 is a second biomass co-firing coupler, 13 is a third biomass co-firing coupler, 14 is a fourth biomass co-firing coupler, 15 is a furnace, 16 is a main pipe air-pulverized coal online measuring device, 17 is a main pipe signal processor, 18 is a DCS control system, 19 is a branch pipe air-pulverized coal online measuring device, and 20 is a branch pipe signal processor. Detailed Embodiments

[0021] To enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments, and are not intended to limit the scope of the present invention disclosure. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessarily confusing the concepts disclosed in the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention.

[0022] The structural schematic diagrams according to the disclosed embodiments of the present invention are shown in the accompanying drawings. These figures are not drawn to scale, and for the purpose of clear expression, some details are enlarged and some details may be omitted. The shapes of various regions and layers shown in the figures, as well as their relative sizes and positional relationships, are merely exemplary. In practice, there may be deviations due to manufacturing tolerances or technical limitations, and those skilled in the art can design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0023] Referring to Figure 1 , the closed-loop control system for fuel distribution regulation for large-scale co-firing of biomass in coal-fired units according to the present invention includes a first Roots blower 7, a first air emitter 5, a second Roots blower 8, a second air emitter 6, a biomass fuel input pipeline, a distributor 2, a first equalizing device 9, a second equalizing device 10, a DCS control system 18, a furnace 15, a first biomass co-firing coupler 11, a second biomass co-firing coupler 12, a third biomass co-firing coupler 13, and a fourth biomass co-firing coupler 14;

[0024] The outlet of the first Roots blower 7 is communicated with the inlet of the first air flow emitter 5, and the outlet of the second Roots blower 8 is communicated with the inlet of the second air flow emitter 6. The biomass fuel input pipeline is communicated with the inlet of the distributor 2 through the weighing belt feeder 1. The outlet of the distributor 2 is communicated with the inlet of the first hammer mill 3 and the inlet of the second hammer mill 4. The outlet of the first hammer mill 3 is communicated with the inlet of the first air flow emitter 5. The outlet of the second hammer mill 4 is communicated with the inlet of the second air flow emitter 6. The outlets of the first air flow emitter 5 and the second air flow emitter 6 are communicated with the inlet of the main powder pipe. The outlet of the main powder pipe is communicated with the inlet of the first equalizing device 9 and the inlet of the second equalizing device 10. The outlet of the first equalizing device 9 is communicated with the inlet of the first biomass co-firing coupler 11 through the first branch pipe. The outlet of the first equalizing device 9 is communicated with the inlet of the second biomass co-firing coupler 12 through the second branch pipe. The outlet of the second equalizing device 10 is communicated with the inlet of the third biomass co-firing coupler 13 through the third branch pipe. The outlet of the second equalizing device 10 is communicated with the inlet of the fourth biomass co-firing coupler 14 through the fourth branch pipe. The outlets of the first biomass co-firing coupler 11, the second biomass co-firing coupler 12, the third biomass co-firing coupler 13 and the fourth biomass co-firing coupler 14 are communicated with the furnace 15.

[0025] On the first branch pipe, the second branch pipe, the third branch pipe and the fourth branch pipe, there are all arranged branch pipe air-powder on-line measuring devices 19. Among them, the branch pipe air-powder on-line measuring device 19 is communicated with the DCS control system 18 through the branch pipe signal processor 20;

[0026] The outlet of the first air flow emitter 5 is communicated with the inlet of the first equalizing device 9 through the first main powder pipe. The outlet of the second air flow emitter 6 is communicated with the inlet of the second equalizing device 10 through the second main powder pipe. Among them, on the first main powder pipe and the second main powder pipe, there are all arranged main pipe air-powder on-line measuring devices 16. Among them, the main pipe air-powder on-line measuring device 16 is connected with the input end of the main pipe signal processor 17, and the output end of the main pipe signal processor 17 is connected with the DCS control system 18.

[0027] The DCS control system 18 is connected with the control ends of the distributor 2, the first Roots blower 7, the second Roots blower 8, the first equalizing device 9 and the second equalizing device 10.

[0028] The working process of the present invention is as follows:

[0029] The biomass fuel is quantitatively fed into the distributor 2 by the weighing belt feeder 1. The distributor 2 has the function of uniform distribution, and is further finely adjusted by the adjusting baffle in the distributor 2. The biomass fuel evenly falls into the first hammer mill 3 and the second hammer mill 4 for crushing. Among them, the biomass fuel output by the first hammer mill 3 enters the first air emitter 5, and is mixed with the air output by the first Roots blower 7 in the first air emitter 5, and then enters the first equalizing device 9 through the first main powder pipe. The biomass fuel output by the second hammer mill 4 enters the second air emitter 6, and is mixed with the air output by the first Roots blower 7 in the first air emitter 5, and then enters the second equalizing device 10 through the second main powder pipe;

[0030] The air-powder output by the first equalizing device 9 is evenly divided into the first biomass co-firing coupler 11 and the second biomass co-firing coupler 12 through the first branch pipe and the second branch pipe. The air-powder output by the second equalizing device 10 is evenly divided into the third biomass co-firing coupler 13 and the fourth biomass co-firing coupler 14 through the third branch pipe and the fourth branch pipe.

[0031] The main pipe air-powder online measuring device 16 measures the wind speed and pulverized coal concentration signals of the air-powder in the first main powder pipe and the second main powder pipe, and then sends them into the main pipe signal processor 17 through the transmission cable, and then forwards them to the DCS control system 18; The main pipe air-powder online measuring device 16 measures the wind speed and pulverized coal concentration signals in the first branch pipe, the second branch pipe, the third branch pipe and the fourth branch pipe, and then sends them to the DCS control system 18 after passing through the branch pipe signal processor 20;

[0032] Compare the wind speed signal in the first main powder pipe with the wind speed signal in the second main powder pipe, and control the first Roots blower 7 and the second Roots blower 8 according to the comparison result, so that the wind speed in the first main powder pipe is the same as the wind speed in the second main powder pipe;

[0033] Compare the pulverized coal concentration signal in the first main powder pipe with the pulverized coal concentration signal in the second main powder pipe, and control the position of the adjusting baffle in the distributor 2 according to the comparison result to adjust the amount of pulverized coal entering the first hammer mill 3 and the second hammer mill 4, so as to make the pulverized coal concentration in the first main powder pipe communicate with the pulverized coal concentration in the second main powder pipe.

[0034] Compare the wind speed and pulverized coal concentration signals in the first branch pipe with those in the second branch pipe, and adjust the baffle position in the first equalizing device 9 according to the comparison result, so that the wind speed and pulverized coal concentration in the first branch pipe are the same as those in the second branch pipe; compare the wind speed and pulverized coal concentration signals in the third branch pipe with those in the fourth branch pipe, and then control the baffle position in the second equalizing device 10 according to the comparison result, so that the wind speed and pulverized coal concentration in the third branch pipe are the same as those in the fourth branch pipe.

[0035] It should be noted that after the closed-loop control adjustment of the wind speed and powder volume between the first main pulverized coal pipe and the second main pulverized coal pipe and their corresponding branch pipes is achieved in sequence, the closed-loop control adjustment of the wind speed and powder volume between all branch pipes is realized, so as to ensure that the air volume and biomass powder volume entering the first biomass co-firing coupler 11, the second biomass co-firing coupler 12, the third biomass co-firing coupler 13 and the fourth biomass co-firing coupler 14 are balanced.

Claims

1. A closed-loop control system for fuel distribution regulation of large-scale co-firing of biomass in coal-fired units, characterized in that, It includes a first Roots blower (7), a first air flow emitter (5), a second Roots blower (8), a second air flow emitter (6), a biomass fuel input pipeline, a distributor (2), a first equalizing device (9), a second equalizing device (10) and a DCS control system (18); The outlet of the first Roots blower (7) is communicated with the inlet of the first air flow emitter (5), the outlet of the second Roots blower (8) is communicated with the inlet of the second air flow emitter (6), the biomass fuel input pipeline is communicated with the inlet of the distributor (2), the outlet of the distributor (2) is communicated with the inlets of the first air flow emitter (5) and the second air flow emitter (6), the outlet of the first air flow emitter (5) is communicated with the inlet of the first equalizing device (9) through a first main powder pipe, the outlet of the second air flow emitter (6) is communicated with the inlet of the second equalizing device (10) through a second main powder pipe, the two outlets of the first equalizing device (9) are respectively communicated with a first branch pipe and a second branch pipe, and the two outlets of the second equalizing device (10) are respectively communicated with a third branch pipe and a fourth branch pipe; Branch pipe air-powder online measuring devices (19) are arranged on the first branch pipe, the second branch pipe, the third branch pipe and the fourth branch pipe; Main pipe air-powder online measuring devices (16) are arranged on the first main powder pipe and the second main powder pipe; The branch pipe air-powder online measuring devices (19) and the main pipe air-powder online measuring devices (16) are communicated with the DCS control system (18); The DCS control system (18) is connected to the control ends of the distributor (2), the first Roots blower (7), the second Roots blower (8), the first equalizing device (9) and the second equalizing device (10); The outlet of the distributor (2) is communicated with the inlet of the first air flow emitter (5) through a first hammer mill (3); The outlet of the distributor (2) is communicated with the inlet of the second air flow emitter (6) through a second hammer mill (4).

2. The closed-loop control system for fuel distribution regulation of large-scale co-firing of biomass in coal-fired units according to claim 1, characterized in that, The biomass fuel input pipeline is communicated with the inlet of the distributor (2) through a weighing belt feeder (1).

3. The closed-loop control system for fuel distribution regulation for large-scale co-firing of biomass in coal-fired units according to claim 1, wherein The outlets of the first air flow emitter (5) and the second air flow emitter (6) are connected through a pipe and then communicated with the inlets of the first equalizing device (9) and the second equalizing device (10) through a main powder pipe.

4. The closed-loop control system for fuel distribution regulation for large-scale co-firing of biomass in coal-fired units according to claim 1, wherein, The branch pipe air-powder online measuring device (19) is communicated with the DCS control system (18) through a branch pipe signal processor (20).

5. The closed-loop control system for fuel distribution regulation in large-scale co-firing of biomass in coal-fired units according to claim 1, wherein The main pipe air-powder online measuring device (16) is communicated with the DCS control system (18) through a main pipe signal processor (17).

6. The closed-loop control system for fuel distribution regulation for large-scale co-firing of biomass in coal-fired units according to claim 1, wherein It further includes a furnace (15), a first biomass co-firing coupler (11), a second biomass co-firing coupler (12), a third biomass co-firing coupler (13) and a fourth biomass co-firing coupler (14); the outlet of the first equalizing device (9) is connected to the inlet of the first biomass co-firing coupler (11) through a first branch pipe, the outlet of the first equalizing device (9) is connected to the inlet of the second biomass co-firing coupler (12) through a second branch pipe, the outlet of the second equalizing device (10) is connected to the inlet of the third biomass co-firing coupler (13) through a third branch pipe, and the outlet of the second equalizing device (10) is connected to the inlet of the fourth biomass co-firing coupler (14) through a fourth branch pipe; The first biomass co-firing coupler (11), the second biomass co-firing coupler (12), the third biomass co-firing coupler (13) and the fourth biomass co-firing coupler (14) are connected to the furnace (15).

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