Bulk fuel biomass furnace feeding device capable of preventing backfire

Abstract

The utility model relates to a backfire-preventing feeding device of a bulk fuel biomass furnace, which can reduce the construction cost of the bulk fuel biomass furnace, and is not exceptional even if fast and inflammable biomass bulk fuel is intermittently operated and used. Biomass bulk fuel is upwards fed into the gasification chamber (1) through a plurality of spiral conveyors (4) with water-cooled walls, and the bulk fuel in a blanking groove (3) arranged at the front parts of the spiral conveyors (4) can realize air tightness by virtue of self weight. The biomass bulk fuel can be sealed through the design of the thread length and angle of a spiral impeller (8) of the spiral conveying machine (4). The tempering safety baffle (5) is installed on the top of the discharging groove (3) and can cut off falling bulk fuel to be closed under the self-weight effect of the tempering safety baffle (5).

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of biomass fuel feeding device, in particular to a biomass furnace feeding device capable of preventing backfire. BACKGROUND

[0002] When the relatively dry biomass bulk fuel enters the biomass gasification furnace or direct combustion furnace with chain grate, water-cooled vibrating grate or circulating fluidized bed, etc. through the feeding system, the risk of backfire during the feeding process is generally increased. The intermittent shutdown of industrial steam boilers may also cause the risk of backfire during the feeding process. The present application relates to a biomass bulk fuel, particularly suitable for chopped crop straw, energy crops and other broken solid waste fuel, and a biomass furnace feeding device capable of preventing backfire.

[0003] To prevent backfire in the feeding system, patent CN117167728A discloses a device composed of a horizontally arranged screw conveyor, a vertical fuel passage, a wheel-type rotary unit gate and a backfire safety valve. In addition, a spiral distribution conveyor is also provided for lateral distribution of fuel within the width of the combustion equipment. Generally, biomass power plants mainly burn bulk materials without drying, and continuously and continuously burn at high speed and high temperature. The above technical device can generally prevent backfire. However, the system structure is complex, and the screw conveyor, wheel-type rotary unit gate, etc. must be designed to be no less than the minimum size to prevent material blockage, so it is difficult to apply the above device to the backfire prevention of small biomass combustion systems.

[0004] According to CN117167728A, the bulk material slides downward at an angle and is subjected to upward buoyancy resistance, which can even push the bulk material to the horizontally arranged screw conveyor, so the screw conveyor is designed as two stages and assisted by a wheel-type rotary unit gate.

[0005] As described in CN115654508A, the horizontally arranged screw conveyor, even with a certain inclination, may have the possibility of backfire, which affects the safe operation of the system, so additional measures such as backfire safety baffle need to be considered. For example, the backfire safety baffle arranged at the end of the CN204880191 pipeline may have corrosion risk, and the backfire safety baffle installed in the CN219341018U feeding channel may not be able to achieve backfire plugging during fuel flow or in the case of uneven fuel size and uniformity.

[0006] The bulk fuel can only prevent backfire together with the backfire safety baffle installed in the fuel supply pipeline when it is in a dense state, but the bulk fuel cannot seal and block backfire when it is filled with a large amount of air during the natural scattering of the fuel into the fuel supply pipeline.

[0007] The gasification of the bulk fuel on the moving grate requires a certain fuel layer height to ensure the set power, and therefore a material level signal is required to feedback and adjust the fuel delivery. CN201811060698.0 shows a whole-straw gasifier with a material level sensor arranged in the gasification chamber, but this sensor can only give a material level signal for the whole fuel, and cannot give a material level height signal for the bulk fuel layer in the range of 0.5-1.5 meters or more.

[0008] The chopped straw and other bulk fuel are often used in small and dispersed heat supply systems, such as industrial steam biomass boilers with large changes in daytime load, and the backfire safety device will also play a role when the load of the small industrial steam boiler decreases or is stopped. When the bulk biomass fuel is relatively dry, the above backfire safety needs to be greatly improved, and there is currently no efficient solution to this problem. SUMMARY

[0009] The present application relates to a biomass bulk fuel feeding device with a spiral feeder that can prevent backfire, which is simple in design, economical, and can also be applied to biomass bulk fuel containing irregular fragments, and can avoid the safety hazards caused by backfire when the fire is stopped. The backfire safety baffle in the present application can be closed quickly at any time. Without increasing additional expensive components, the bulk fuel level and width can be controlled and varied.

[0010] The gasification chamber is fed with bulk fuel by one or more spiral feeders containing water-cooled walls. The spiral feeder is lifted upward at an upward angle, and bulk fuel is loaded from above the discharge chute arranged in the front of the spiral feeder. The discharge chute is widened downward from top to bottom and completely covers the front of all spiral feeders. The filling height of the bulk fuel in the discharge chute is always maintained above 4 meters and connected to the spiral feeder in a gas-tight manner. The bulk fuel in the discharge chute continuously falls downward and compacts due to its own weight, thereby isolating air flow.

[0011] This sealing effect can prevent fresh air from being sucked into the bulk fuel feeding device by the negative pressure in the biomass furnace through the backfire prevention device. Without air, backfire can be avoided to a certain extent.

[0012] The screw feeder is raised at an angle of elevation, and the bulk material fuel entering the screw feeder slides down the downwardly inclined feed chamber into the gasification chamber. In this process, hot flue gas from the gasification chamber can flow back up, so a water-cooled wall is arranged in the area of the screw feeder adjacent to the gasification chamber.

[0013] Since the screw feeder is inclined upward at an angle of at least 45 degrees, the hot flue gas is somewhat blocked from entering the lower part of the screw feeder, so the front half of the screw feeder, which is downward, will remain at a relatively low temperature.

[0014] To ensure that even poor-flowing bulk material fuel can enter the screw feeder from above and flow out of the top of the screw feeder, which is raised at an angle of elevation, the angle of elevation between the screw feeder and the horizontal plane should be between 45 and 55 degrees.

[0015] To ensure the tightness of the screw feeder during operation, the bulk material fuel must always be in contact with all the sides of the inner surface of the screw feeder during the feeding process, so as to close the gap between the bulk material fuel screw wave and the inner surface of the screw feeder. To achieve the tightness of the bulk material fuel with the upper and lower inner wall surfaces at the same time when the screw feeder is rotating, it is necessary to ensure that the angle between the screw feeder and the horizontal plane is greater than 45 degrees, and the length of the screw part of the feeder is at least 1.7x the diameter D. In this way, even if only a certain amount of bulk material fuel enters the screw feeder and the rotation speed of the bulk material fuel screw wave is very slow, the bulk material fuel can still be pressed against the upper inner surface of the screw feeder to achieve the tightness of the screw feeder.

[0016] If the above-mentioned angle is between 45 and 55 degrees, and the length of the screw part of the screw feeder is greater than 2.5xD, the filling and tightness of the bulk material fuel in the screw feeder will be better, because at this time the bulk material fuel is almost vertically lifted by the screw feeder, and the gravity of the bulk material fuel hardly changes the position of the bulk material fuel, so the same amount of bulk material fuel will be more evenly attached to the upper inner surface of the screw feeder to achieve tightness.

[0017] Since the temperature and intensity of the gasification and combustion of bulk material fuel are much lower than those of traditional bulk material fuel direct combustion equipment, the amount of fuel required in the bulk material fuel gasification furnace is much larger than that in the direct combustion furnace, so the bulk material fuel gasification furnace requires a larger grate length, width, and higher bulk material fuel layer height. Tests and researches have shown that the bulk material fuel layer height on the grate should be more than 1 meter to ensure the uniformity and compactness of the bulk material fuel, and to avoid the bulk material fuel burning in places where the bulk material fuel layer on the grate is too thin.

[0018] One or more screw feeders in the present application are arranged in a fan shape to evenly spread the bulk material fuel as much as possible over the entire grate width of the bulk material fuel biomass furnace without adding additional equipment.

[0019] The level of the bulk material in the gasification furnace is monitored by one or more level sensors in the gasification furnace and timely signals are sent out. The sensing rods of the level sensors are made of high-temperature-resistant stainless steel and are suspended at different depths in the gasification furnace. The sensing rods rotate when they come into contact with the moving fuel level. The screw conveyor adjusts the speed of the physical conveyor according to the feedback signals of the sensors to adjust the height of the bulk fuel level.

[0020] The fuel in the discharge chute of the present application is always full during normal operation, and the fuel density is higher at the bottom. The discharge chute is tapered and widens from top to bottom. The sidewalls of the discharge chute are at an angle of 5-8 degrees to the vertical, which makes it impossible for the bulk fuel to bridge. This ensures that the discharge chute has sufficient height for the bulk fuel to be evenly distributed in the discharge chute. When the bulk fuel enters the discharge chute from the middle of the top of the discharge chute, the bulk fuel can be distributed to all widths and angles of the discharge chute by dropping. To achieve this dropping distribution function of the bulk fuel, the drop height of the discharge chute should be at least 4 meters or more.

[0021] The present application controls the level of the bulk fuel in the discharge chute according to the feedback signals from at least three level sensors arranged at different heights. The above-mentioned level sensors are preferably suspended level sensors, which are suspended at the top to prevent being buried by the bulk fuel.

[0022] The bulk fuel is fed into the discharge chute from above by the steep slope feeding belt. The feeding port of the discharge chute is closed at any time by a sealing and tempering safety baffle. The tempering safety baffle is preferably fixed by an electromagnet at the open position of the feeding port and can completely rely on its own weight to fall and close the feeding port. When the feeding port is closed, the tempering safety baffle falls freely above the discharge chute in a direction roughly consistent with the direction of the falling bulk fuel flow and cuts off the bulk fuel flow, so that the continuous flow of bulk fuel does not hinder the closing of the safety baffle, thereby ensuring that tempering does not occur.

[0023] If the bulk fuel in the discharge chute is overfilled and accumulates due to unexpected circumstances, the bulk fuel that is overfilled and accumulates in the discharge chute can also achieve a sealing function.

[0024] When the bulk fuel falling onto the tempering safety baffle from above the discharge chute slides back into the steep slope feeding belt through the chute, a movable bottom plate is arranged below the rotating roller at the bottom of the steep slope feeding belt. The flexible load plate can pick up the bulk fuel that slides onto the movable bottom plate, thereby preventing the flexible load plate on the steep slope feeding belt from being jammed. BRIEF DESCRIPTION OF DRAWINGS

[0025] The embodiments of the present application will be described in detail below with the help of seven drawings.

[0026] Figure 1 Shown is a side view of the feeding device with anti-backfire safety device of the chain grate bulk material fuel gasification furnace.

[0027] Figure 2 Shown is a side view of the design of the spiral impeller (8) when the bulk material fuel cannot be tightly attached to all surfaces of the spiral feeder (4) to achieve air tightness.

[0028] Figure 3 Shown is a side view of the design of the spiral impeller (8) when the bulk material fuel can be effectively tightly attached to all surfaces of the spiral feeder (4) to achieve air tightness.

[0029] Figure 4 Shown is a top view of the anti-backfire safety feeding device with three parts of the spiral feeder (4) arranged in a fan shape.

[0030] Figure 5 Shown is a side view of the upper half of the discharge chute (3) with a backfire safety baffle (5) and a material level sensor (10).

[0031] Figure 6 Shown is a side view of the material level sensor arrangement method in the gasification chamber (1).

[0032] Figure 7 Shown is a side view of the steep slope type feeding belt (2) that sends the sliding bulk material fuel back.

[0033] In the figure: 1-gasification chamber, 2-steep slope type feeding belt, 3-discharge chute, 4-spiral feeder, 5-backfire safety baffle, 6-water-cooled wall, 7-firefighting water inlet, 8-spiral impeller, 9-electromagnet, 10-material level sensor, 11-rotatable sensing rod, 12-pivot point, 13-retention ring, 14-maintenance door, 15-hopper feeder bottom plate, 16-movable bottom plate, 17-flexible load-carrying plate, 18-lower rotating pivot, 19-counterweight rod, 20-upper rotating pivot. DETAILED DESCRIPTION

[0034] Figure 1 Shown is a feeding device with anti-backfire safety device for delivering bulk material fuel to the gasification chamber (1), where the bulk material fuel is from the upstream fuel drying equipment of the CN202211552835.9 patent, so its burning speed will be very fast. If the gasification chamber (1) here is part of an industrial steam boiler, the industrial steam boiler may often be out of fire or out of furnace due to discontinuous and undetermined steam output, and the safety requirements for preventing backfire of the gasification chamber (1) in the above two cases will be very high.

[0035] When the industrial steam boiler load requirement is reduced to zero or the screw feeder (4) is stopped or power failure, the excess loading and accumulated bulk solid fuel in the hopper (3) can also be sealed to prevent backfire.

[0036] The steep slope feeding belt (2) conveys the bulk solid fuel upward and feeds it into the hopper (3) from above. The hopper (3) is connected to one or more screw feeders (4) at the bottom. The loading height of the hopper (3) is about 5 meters higher than the screw feeder (4) in the figure, so that the bulk solid fuel can be compressed by its own weight to prevent it from being affected by the flowing air. In this embodiment, the pressure in the gasification chamber (1) is about -90 Pa, so it will not affect the airtightness of the bulk solid fuel.

[0037] The design length of the screw feeder (4) is about 9 meters, and the front half of about 4 meters has good airtightness. External air must come down from the upper opening of the hopper (3) and pass through the front half of the screw feeder (4) to cause backfire. It is not easy for external air to penetrate about 9 meters of bulk solid material, so backfire is not easy to occur.

[0038] However, hot flue gas from the gasification chamber (1) may enter the area near the gasification chamber of the screw feeder (4) under some emergency conditions, causing the temperature to rise, so the area near the gasification chamber of the screw feeder (4) can be provided with a water-cooled wall (6) for cooling, which can effectively prevent the screw feeder (4) from being damaged when backfire occurs.

[0039] The fire-fighting water inlet (7) is a separate control safety device. When the temperature in the fire-fighting water inlet (7) area exceeds the limit value (such as 100℃), the fire-fighting water inlet (7) valve will automatically open and introduce an appropriate amount of water. The steam generated by the high temperature will push the air in the area out, thereby reliably extinguishing the fire without the need for electrical equipment.

[0040] At this time, the feeding port at the top of the hopper (3) will also be automatically closed by the backfire safety baffle (5). The top feeding port of the feeding device of the present invention is always open when it is working normally, and will only be closed in the event of backfire or emergency. At the same time, the anti-backfire safety feeding device will be sealed, and the backfire will be blocked. At this time, the backfire and the fuel in the hopper (3) are pushed into the gasification chamber (1), or the fire-fighting water inlet (7) in the screw feeder (4) is activated to extinguish the backfire in the screw feeder (4).

[0041] The vertically arranged hopper (3) is flared from top to bottom, and all surfaces of the hopper (3) are at an angle of 7 degrees with the vertical line of the hopper (3), which can effectively prevent the bulk solid fuel from bridging and blocking and make the bulk solid fuel evenly spread horizontally.

[0042] The conical design of the chute (3) means that it has a large surface area connected to the screw conveyor (4), in the present embodiment the area of the chute (3) connected to each screw conveyor (4) is approximately 2.1 square meters, this area or greater is advantageous for the delivery of bulk fuel containing large branches and bark.

[0043] The screw conveyor (4) in the present embodiment has a 48 degree angle to the horizontal, the buoyancy force created by the hot flue gases from the gasification chamber (1) acts to prevent further penetration of the hot flue gases into the front of the screw conveyor (4).

[0044] Figure 2 The geometry of the screw conveyor (4) and the design of the screw flight (8) are shown to have an effect on the air tightness. The screw conveyor (4) has a 48 degree angle. The screw flight (8) has a diameter of 80 cm or greater, so that the chopped crop straw, branches or bulk fuel with a certain size of wood block, etc. are not easy to cause blockage.

[0045] The length of the screw flight (8) is only 1.2 times the diameter D of the screw flight (8). The force F of the bulk fuel cannot resist the gravity of the bulk fuel to make the bulk fuel tilt to the left in the figure, towards the bottom of the screw conveyor (4), so that the bulk fuel at the bottom accounts for a large proportion, and the bulk fuel at the top accounts for a small proportion, so that the uneven distribution of the bulk fuel affects the air tightness during the conveying process.

[0046] Figure 3 The screw flight (8) is shown, the length of the screw flight (8) is 2.7 times the diameter D of the screw flight (8), so that the gravity of the bulk fuel is offset and the bulk fuel is no longer offset to one side, at this time the bulk fuel is in uniform contact with all the inner wall surfaces to achieve better air tightness. Therefore, the length of the screw flight (8) of the present application should be at least 2.4 times the diameter D of the screw flight (8), and the angle of the screw conveyor (4) is preferably 45-55 degrees. In this way, the air tightness of the bulk fuel flow of the screw conveyor (4) combined with the chute (3) can more effectively prevent backfire, so that more complex structures such as impeller air tightness valves are no longer needed, which makes the equipment structure simple and the cost reasonable.

[0047] Figure 4 Three screw conveyors (4) of the device are shown arranged in a fan shape on an inclined plane. The chute (3) meets the working condition requirements of the width (1.6 meters) of the steep slope type feeding belt (2) and the width (2.7 meters) of the feeding port of the screw conveyor (4). The fan-shaped arrangement of the screw conveyors (4) enables them to adapt to the bulk fuel gasification chamber (1) without the need for additional cross-conveying devices.

[0048] As Figure 5The top of the hopper (3) is provided with a tempering safety baffle (5), which is kept in the open position of the hopper (3) by an electromagnet (9). When the signal is triggered, the tempering safety baffle (5) will automatically fall to the closed position of the hopper (3) under the action of its own weight, thus blocking the flow of bulk fuel.

[0049] In order to continuously adjust the bulk fuel loading level in the hopper (3), the embodiment contains four height-adjustable level sensors (10). These sensors are designed in a pendulum type, containing a rotating plate close to the wall and a cover on the top. The fuel feeding speed and amount can be controlled by these level sensors (10). When the actual fuel level exceeds the set value, the tempering safety baffle (5) will fall to the closed position of the hopper (3).

[0050] Figure 6 The level sensor (10) in the gasification chamber (1) is mainly composed of a rotating sensing rod (11) made of refractory stainless steel. The rotating sensing rod (11) in this embodiment is about 1.7 meters long and can rotate around the fulcrum (12). The operator can set the height of the rotating sensing rod (11) through the retaining ring (13) through the maintenance door (14).

[0051] According to Figure 1 and Figure 7 When the tempering safety baffle (5) falls to the closed position, the bulk fuel will slide onto the hopper bottom plate (15) and slide down below the steep slope feeding belt (2). A movable bottom plate (16) is arranged below the steep slope feeding belt (2). When the bulk fuel is blocked, the movable bottom plate (16) will move downward, thus protecting the flexible load plate (17) of the steep slope feeding belt (2). Then the steep slope feeding belt (2) will pick up the bulk fuel from above the movable bottom plate (16) and send it back to the feeding system to ensure stable operation of the system.

[0052] Obviously, the above embodiments are only examples for the purpose of clarity, and are not limiting of the embodiments. Based on the above description, other different forms of changes or variations can be made by those of ordinary skill in the art. Here, it is not necessary and impossible to exhaust all embodiments. The obvious changes or variations derived therefrom are still within the scope of the present application.

Claims

1. A feed device of a non-backfire bulk fuel biomass furnace, comprising a gasification chamber, a screw feeder, a discharge chute, a steep slope feeding belt, and a material level sensor; characterized in that, The gasification chamber (1) is fed with bulk fuel by one or more screw conveyors (4) with water-cooled walls, which are raised at an upward angle, and are loaded with bulk fuel from above a feed chute (3) arranged in front of the screw conveyors (4), the feed chute (3) being widened in a conical shape from top to bottom and covering completely the front of all screw conveyors (4), the filling height of bulk fuel in the feed chute (3) being kept above 4 meters and being connected to the screw conveyors (4) in a gas-tight manner.

2. A feed arrangement for a bulk fuel biomass furnace that prevents backfiring according to claim 1, wherein, The screw conveyors (4) are arranged in a fan shape and are raised at an upward angle of 45-55 degrees to the horizontal plane.

3. A feed arrangement for a bulk fuel biomass furnace that prevents backfiring as claimed in claim 2, wherein, The thread length of the spiral impeller (8) in the screw conveyor (4) is 1.7-2.7 times the diameter of the spiral impeller (8).

4. A feed arrangement for a bulk fuel biomass furnace that prevents flashbacks according to claim 1, wherein, All side walls of the feed chute (3) are inclined at an angle of 5-8 degrees to the vertical, and the filling height of bulk fuel in the feed chute (3) can be adjusted by level sensors (10) arranged at different heights.

5. A feed arrangement for a non-backfiring bulk fuel biomass furnace as defined in claim 1, wherein: The top of the feed chute (3) can be closed by a tempering safety flap (5), which can be moved in the bulk fuel flow in the feed chute (3) after signal triggering and can be closed by the weight of the tempering safety flap (5) acting on its own.

6. A feed arrangement for a non-backfiring bulk fuel biomass furnace as defined in claim 1, wherein, There is one or more level sensors in the gasification chamber (1), which consist of a rotatable sensor rod (11) that can rotate depending on the change in fuel layer height.

7. A feed arrangement for a non-backfiring bulk fuel biomass furnace as defined in claim 1, wherein, A movable floor (16) is arranged below the rotating rollers at the bottom of the steep slope type feeding belt (2), and a flexible load carrier plate (17) can pick up the bulk fuel that slides onto the movable floor (16).

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