Axial inner air chamber heating structure of low rank coal pyrolysis rotary furnace

Abstract

An axial inner air chamber heat supply structure of a low-rank coal pyrolysis rotary furnace, comprising a hot air chamber main body, a discharge end cylinder, a rotary furnace cylinder, a hot air chamber side pipe plate, a cooling air sleeve, an axial inner air chamber, a connecting pipe and an air chamber outer sleeve, the hot air chamber main body is sleeved on the outer periphery of the discharge end cylinder, the cooling air sleeve is between the hot air chamber main body and the discharge end cylinder, one end of the cooling air sleeve is fixedly connected to the inner circle of the hot air chamber side pipe plate, the outer circle of the hot air chamber side pipe plate and the cooling air sleeve are respectively dynamically connected to the hot air chamber main body through sealing devices, one end of the connecting pipe is in communication with the hot air chamber main body, and the other end is in communication with the axial inner air chamber, the air chamber outer sleeve is sleeved on the outside of the connecting pipe and is fixedly connected to the hot air chamber side pipe plate and the cylinder side pipe plate at both ends, and the axial inner air chamber is in communication with the heat exchange pipe. The structure can effectively reduce the temperature of the pipe plate and the cylinder, prevent the destruction and deformation of the pipe plate and the cylinder caused by the excessively high temperature, and thus improve the overall reliability and pyrolysis capacity of the rotary furnace.

Description

Technical Field

[0001] This invention belongs to the fields of coal chemical industry, oil shale and biomass pyrolysis, and specifically relates to an axial inner wind chamber heating structure for a low-rank coal pyrolysis rotary furnace. Background Technology

[0002] Rotary kilns, with their advantages of strong adaptability to raw material particle size, large single-furnace processing capacity, and high-quality pyrolysis products, have broad application prospects in the field of low-rank coal pyrolysis. For rotary kilns in low-rank coal pyrolysis, a crucial technical aspect is ensuring reliable kiln operation while supplying heat into the furnace to achieve thorough and efficient pyrolysis. Hot air, as a commonly used heat source, is typically used in two ways: through heat exchange tubes introduced into the furnace or by directly heating the furnace shell, to achieve indirect heat exchange with the material to be pyrolyzed.

[0003] If hot air directly heats the furnace shell, even if heat-resistant steel is used for the furnace shell, it will not only significantly increase the cost of the kiln, but also, as the mechanical properties of heat-resistant steel decrease sharply under high temperature conditions, the strength and rigidity of the kiln itself cannot be guaranteed, and the upper limit of the pyrolysis temperature will be strictly limited, thereby affecting the efficiency of pyrolysis and the quality of the product.

[0004] If hot air is introduced into the heat exchange tubes inside the furnace, and the furnace shell is internally insulated, the rotary kiln cylinder can operate at a lower temperature. This reduces heat loss from the cylinder, allowing for good structural stability when using plain carbon steel. The pyrolysis temperature inside the furnace can also be further increased (hot air temperature can reach 800-900℃), thereby improving pyrolysis efficiency and yield. However, at the interface between the hot air and the furnace body, there is still the problem of locally high temperatures and large temperature gradients within the cylinder, leading to significant thermal stress that can cause weld cracking or cylinder deformation.

[0005] For rotary kilns with internal insulation and hot air introduced into the heat exchange tubes inside the furnace, existing technologies mainly employ radial air intake. This means the hot air chamber is annular, with the cylinder passing through it. The cylinder has evenly spaced perforations along its circumference at this location. The heat exchange tubes connect to the hot air chamber at this point via a 90° bend or an inner air chamber arranged circumferentially. The two sides of the hot air chamber are dynamically sealed to the cylinder using a scale-type sealing device. To prevent direct impact of hot air onto the cylinder, a concentric sleeve is added to the outer side of the cylinder at this location, forming an annular channel for cooling air to enter. The outer side of the sleeve is equipped with a heat insulation layer and rotates with the rotary kiln.

[0006] Although existing technical solutions can alleviate the problems of high temperature and large temperature gradient at the interface between hot air and furnace body to some extent, some problems and limitations still exist.

[0007] First, at the point where the heat exchange tube passes through the hole in the cylinder, because the temperature inside the heat exchange tube is higher than the temperature of the outer wall of the cylinder, the expansion will be greater than that of the hole, which will lead to the damage of the weld between the heat exchange tube and the cylinder, or even the cracking of the cylinder and the leakage of raw coal gas. Secondly, the hot air enters the furnace radially and needs to make a 90° turn before it can exchange heat with the material along the axial direction, which increases the resistance of the hot air. Furthermore, the numerous holes in the cylinder not only increase the difficulty of processing and manufacturing but also cause a loss of its own strength. In order to mitigate the above effects and allow hot air to enter each heat exchange tube evenly, the holes in the cylinder usually need to be evenly distributed in both the axial and circumferential directions. The distribution range in the axial direction is roughly the same as the width of the hot air chamber. This results in different actual lengths of each group of heat exchange tubes, wasting some cylinder length under the premise of the same heat exchange area.

[0008] In addition, for shell-and-tube heat exchangers or flue-type waste heat boilers that use axial heating, in order to prevent problems such as tube sheet deformation and leakage, the heat exchange tubes and tube sheets are usually connected by strength expansion joints, patch expansion joints, strength welding, and sealing welding. However, compared with low-rank coal pyrolysis rotary kilns, there are still the following differences: First, the heat transfer coefficient of the heat exchanger or waste boiler is much higher than that of the rotary kiln for low-rank coal pyrolysis. This means that the heat in the heat exchange tubes of the rotary kiln cannot be absorbed in time. Furthermore, due to the close arrangement of the heat exchange tubes, a high-temperature zone is easily formed between two adjacent heat exchange tubes, which leads to an overall increase in the temperature of the tube sheet. In addition, there is a large temperature gradient at different locations on the tube sheet, which in turn leads to a large amount of thermal stress and deformation between the tube sheet and the heat exchange tubes. Secondly, the diameter of heat exchange tubes in heat exchangers or waste boilers is usually no more than 57mm, and the corresponding tube expansion technology is very mature. However, with the improvement of the processing capacity of low-rank coal pyrolysis rotary kilns, the diameter of heat exchange tubes can exceed 300mm, making tube expansion difficult and unsuitable for on-site installation. Heat exchangers or waste heat boilers are static equipment, while rotary kilns for low-rank coal pyrolysis are dynamic equipment. Alternating stress exists in the heat exchange tubes and tube sheets, making them more prone to fatigue failure. Summary of the Invention

[0009] This invention provides an axial inner air chamber heating structure for a low-rank coal pyrolysis rotary furnace, which introduces a heat source into the heat exchange tubes and has internal insulation. The structure directs hot air from the air chamber along the axial direction of the rotary furnace, through connecting pipes, and through the tube sheet of the cylinder and air chamber into the inner air chamber inside the furnace. The hot air is then distributed to the heat exchange tubes within the furnace. The inner wall of the connecting pipes is insulated, while forced cooling is applied between the tube sheets on both sides and to the outer side of the cylinder at the discharge end. This effectively reduces the temperature of the tube sheet and cylinder, preventing damage and deformation caused by excessive temperature, thereby improving the overall reliability and pyrolysis capacity of the rotary furnace.

[0010] To achieve the above objectives, the present invention employs the following technical solution: An axial inner air chamber heating structure for a low-rank coal pyrolysis rotary kiln includes a hot air chamber body, a discharge end cylinder, a rotary kiln body, a hot air chamber side tube plate, a cooling air sleeve, an axial inner air chamber, a connecting pipe, and an outer air chamber sleeve. The discharge end cylinder has a diameter smaller than the rotary kiln body and is fixedly connected to the cylinder side tube plate on the end face of the rotary kiln body. The hot air chamber body is circumferentially sleeved around the outer periphery of the discharge end cylinder. The cooling air sleeve is located between the hot air chamber body and the discharge end cylinder. One end of the cooling air sleeve is fixedly connected to the inner circle of the hot air chamber side tube plate, and the outer circle of the hot air chamber side tube plate is connected to the hot air chamber... The main body is dynamically connected by a scale sealing device. The other end of the cooling air jacket is also dynamically connected to the hot air chamber main body by a scale sealing device. One end of the connecting pipe is connected to the hot air chamber main body, and the other end passes through the cylinder side tube plate and is connected to the axial inner air chamber placed in the rotary kiln cylinder. The outer sleeve of the air chamber is sleeved on the outside of the connecting pipe and its two ends are fixedly connected to the hot air chamber side tube plate and the cylinder side tube plate, respectively. The axial inner air chamber is connected to the heat exchange tube in the rotary kiln cylinder. A cooling air channel is formed between the cooling air jacket and the discharge end cylinder and between the hot air chamber side tube plate and the cylinder side tube plate. Cooling air is blown in from the discharge side, passes through the annular channel between the discharge end cylinder and the cooling air sleeve, and then enters the channel between the hot air chamber side tube plate and the cylinder side tube plate, finally flowing out of the rotary kiln.

[0011] Several of the connecting pipes are evenly distributed in the circumferential direction of the rotary kiln cylinder.

[0012] The axial inner air chambers are evenly distributed in the circumferential direction within the rotary furnace cylinder, and adjacent axial inner air chambers are staggered from each other in the axial direction.

[0013] The number of connecting pipes and axial inner air chambers is even, and one axial inner air chamber connects to multiple heat exchange pipes.

[0014] A heat insulation layer is provided inside the discharge end cylinder, inside the rotary kiln cylinder, and inside the cylinder side tube sheet. A heat insulation layer is also provided inside the connecting pipe and the hot air chamber side tube sheet, and outside the cooling air jacket.

[0015] The diameter of the connecting pipe is larger than the diameter of the heat exchange pipe.

[0016] An expansion gap is left between the connecting pipe and the pipe hole of the cylinder side plate.

[0017] A conical baffle is provided at the right-angle connection between the discharge end cylinder and the side tube plate of the cylinder.

[0018] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention adopts an axial inner air chamber heating structure. Hot air enters the rotary kiln axially through the air chamber and the connecting pipe. The diameter of the connecting pipe is much larger than the diameter of the heat exchange tube. Therefore, there is enough space inside the connecting pipe for heat insulation design. While reducing the thermal expansion of the connecting pipe itself, it also reduces the heat conduction to the tube sheet. Combined with the internal heat insulation of the rotary kiln and the tube sheet, the tube sheet and the cylinder can be kept at a low temperature, avoiding damage caused by thermal stress.

[0019] 2. This invention provides forced cooling between the two tube sheets and outside the discharge end cylinder, further reducing the temperature of the tube sheets, the outer sleeve of the air vent, and the cylinder, thus ensuring the reliability of the equipment.

[0020] 3. In this invention, a certain expansion gap is left between the connecting pipe and the pipe hole of the tube sheet on the side of the cylinder to prevent damage to the connecting pipe and tube sheet due to thermal expansion. At the same time, an outer sleeve of the air chamber is provided on the outside of the connecting pipe, and the outer sleeve of the air chamber is continuously welded to the tube sheets on both sides to ensure that the pyrolysis gas inside the furnace will not leak outward.

[0021] 4. The present invention adopts an axial inner air chamber, and the number of tube holes on the tube sheet is reduced from the original number of heat exchange tubes to the number of inner air chambers. The number is significantly reduced and the diameter is increased, which reduces the processing and manufacturing difficulty of the tube sheet, and at the same time makes it more conducive to the passage of cooling air and improves the cooling effect.

[0022] 5. In this invention, the hot air enters the rotary kiln axially, resulting in lower hot air resistance.

[0023] 6. In this invention, the hot air enters the furnace axially through the tube sheet, without damaging the rotary kiln's cylindrical structure, thus ensuring greater overall strength. Attached Figure Description

[0024] Figure 1 This is a cross-sectional view of the axial inner air chamber heating structure of the present invention.

[0025] Figure 2 This is a cross-sectional view (AA) of the present invention.

[0026] Figure 3 This is a schematic diagram of a single internal air chamber of the present invention.

[0027] In the diagram: 1. Hot air chamber main body, 2. Scale sealing device, 3. Cooling air sleeve, 4. Thermal insulation layer, 5. Discharge end cylinder, 6. Conical baffle plate, 7. Hot air chamber side tube sheet, 8. Outer sleeve of the air chamber, 9. Cylinder side tube sheet, 10. Connecting pipe, 11. Axial inner air chamber, 12. Rotary furnace cylinder, 13. Heat exchange tube. Detailed Implementation

[0028] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings: like Figures 1-3 As shown, an axial inner air chamber heating structure for a low-rank coal pyrolysis rotary kiln includes a hot air chamber body 1, a discharge end cylinder 5, a rotary kiln body 12, a hot air chamber side tube plate 7, a cooling air sleeve 3, an axial inner air chamber 11, a connecting pipe 10, and an outer air chamber sleeve 8. The discharge end cylinder 5 has a smaller diameter than the rotary kiln body 12 and is fixedly connected to the cylinder side tube plate 9 on the end face of the rotary kiln body 12. The hot air chamber body 1 is circumferentially sleeved around the outer periphery of the discharge end cylinder 5. The cooling air sleeve 3 is located between the hot air chamber body 1 and the discharge end cylinder 5. One end of the cooling air sleeve 3 is fixedly connected to the inner circle of the hot air chamber side tube plate 7, and the outer circle of the hot air chamber side tube plate 7 is connected to the hot air chamber side tube plate 7. The main body 1 of the chamber is dynamically connected through a scale sealing device. The other end of the cooling air sleeve 3 is also dynamically connected to the main body 1 of the hot air chamber through a scale sealing device. One end of the connecting pipe 10 is connected to the main body 1 of the hot air chamber, and the other end passes through the cylinder side tube plate 9 and is connected to the axial inner air chamber 11 placed in the rotary kiln cylinder 12. The outer sleeve 8 of the air chamber is sleeved on the outside of the connecting pipe 10 and its two ends are fixedly connected to the hot air chamber side tube plate 7 and the cylinder side tube plate 9 respectively. The axial inner air chamber 11 is connected to the heat exchange tube 13 in the rotary kiln cylinder 12. A cooling air channel is formed between the cooling air sleeve 3 and the discharge end cylinder 5 and between the hot air chamber side tube plate 7 and the cylinder side tube plate 9.

[0029] Several of the connecting pipes 10 are evenly distributed in the circumferential direction of the rotary kiln cylinder 12.

[0030] The axial inner air chambers 11 are evenly distributed in the circumferential direction within the rotary kiln cylinder 12, and two adjacent axial inner air chambers 11 are staggered from each other in the axial direction.

[0031] There are an even number of connecting pipes 10 and axial inner air chambers 11, and one axial inner air chamber 11 connects to multiple heat exchange pipes.

[0032] The diameter of the connecting pipe 10 is larger than the diameter of the heat exchange pipe 13.

[0033] An expansion gap is left between the connecting pipe 10 and the pipe hole of the cylinder side plate 9.

[0034] A conical baffle is provided at the right-angle connection between the discharge end cylinder 5 and the cylinder side tube plate 9.

[0035] In this invention, the hot air chamber body 1 is a static device, which is dynamically sealed to the rotating rotary kiln through the scale sealing device 2. The hot air chamber side tube plate 7 is an annular steel plate, which is connected to the cylinder side tube plate 9 through several air chamber outer sleeves 8 evenly distributed in the circumferential direction. The cylinder side tube plate 9 is also an annular steel plate, with its inner ring connected to the discharge end cylinder 5 and its outer ring connected to the rotary kiln cylinder 12. The inner circle of the hot air chamber side tube plate 7 is connected to the cooling air sleeve 3. The space formed between the two side tube plates, the air chamber outer sleeve 8, the discharge end cylinder 5 and the cooling air sleeve 3 is the cooling air circulation area. The cooling air is blown in from the discharge side, passes through the annular channel outside the discharge end cylinder 5 and enters the channel between the two side tube plates, and finally flows out of the rotary kiln. In order to reduce the resistance of the cooling air at the corner of the circulation area, a conical baffle 6 is added at the root of the discharge end cylinder 5.

[0036] The axial inner air chambers 11 are evenly distributed in the circumferential direction of the rotary kiln. They are fan-shaped. One end passes through the pipe hole on the side tube plate 9 of the cylinder through the connecting pipe 10 to the hot air chamber side tube plate 7 and is connected thereto. The other end is connected to the heat exchange tube 13. The number of axial inner air chambers 11 should preferably be even. Two adjacent axial inner air chambers 11 are staggered in the axial direction to avoid forming a continuous annular area, which would affect the smoothness of material discharge.

[0037] A heat insulation layer 4 is provided on the inner side of the discharge end cylinder 5, the rotary kiln cylinder 12 and the cylinder side tube plate 9, and a heat insulation layer 4 is provided on the inner side of the connecting pipe 10 and the hot air chamber side tube plate 7 and the outer side of the cooling air jacket 3.

[0038] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. An axial internal air chamber heating structure for a low-rank coal pyrolysis rotary furnace, characterized in that, The system includes a hot air chamber body, a discharge end cylinder, a rotary kiln body, a hot air chamber side tube plate, a cooling air sleeve, an axial inner air chamber, a connecting pipe, and an outer air sleeve. The discharge end cylinder has a smaller diameter than the rotary kiln body and is fixedly connected to the cylinder side tube plate on the end face of the rotary kiln body. The hot air chamber body is circumferentially fitted around the outer periphery of the discharge end cylinder. The cooling air sleeve is located between the hot air chamber body and the discharge end cylinder. One end of the cooling air sleeve is fixedly connected to the inner circle of the hot air chamber side tube plate. The outer circle of the hot air chamber side tube plate is connected to the hot air chamber body via a sealing device. The cooling air jacket is dynamically connected to the hot air chamber body through a sealing device. One end of the connecting pipe is connected to the hot air chamber body, and the other end passes through the cylinder side tube plate and is connected to the axial inner air chamber placed inside the rotary kiln. The outer sleeve of the air chamber is sleeved on the outside of the connecting pipe and its two ends are fixedly connected to the hot air chamber side tube plate and the cylinder side tube plate, respectively. The axial inner air chamber is connected to the heat exchange tube inside the rotary kiln. A cooling air channel is formed between the cooling air jacket and the discharge end cylinder and between the hot air chamber side tube plate and the cylinder side tube plate. Cooling air is blown in from the discharge side, passes through the annular channel between the discharge end cylinder and the cooling air sleeve, and then enters the channel between the hot air chamber side tube plate and the cylinder side tube plate, finally flowing out of the rotary kiln.

2. The axial inner air chamber heating structure of a low-rank coal pyrolysis rotary furnace according to claim 1, characterized in that, Several of the connecting pipes are evenly distributed in the circumferential direction of the rotary kiln cylinder.

3. The axial inner air chamber heating structure of a low-rank coal pyrolysis rotary furnace according to claim 1 or 2, characterized in that, The axial inner air chambers are evenly distributed in the circumferential direction within the rotary furnace cylinder, and adjacent axial inner air chambers are staggered from each other in the axial direction.

4. The axial inner air chamber heating structure of a low-rank coal pyrolysis rotary furnace according to claim 1 or 2, characterized in that, The number of connecting pipes and axial inner air chambers is even, and one axial inner air chamber connects to multiple heat exchange pipes.

5. The axial inner air chamber heating structure of a low-rank coal pyrolysis rotary furnace according to claim 1, characterized in that, A heat insulation layer is provided inside the discharge end cylinder, inside the rotary kiln cylinder, and inside the cylinder side tube sheet. A heat insulation layer is also provided inside the connecting pipe and the hot air chamber side tube sheet, and outside the cooling air jacket.

6. The axial inner air chamber heating structure of a low-rank coal pyrolysis rotary furnace according to claim 1, characterized in that, The diameter of the connecting pipe is larger than the diameter of the heat exchange pipe.

7. The axial inner air chamber heating structure of a low-rank coal pyrolysis rotary furnace according to claim 1, characterized in that, An expansion gap is left between the connecting pipe and the pipe hole of the cylinder side plate.

8. The axial inner air chamber heating structure of a low-rank coal pyrolysis rotary furnace according to claim 1, characterized in that, A conical baffle is provided at the right-angle connection between the discharge end cylinder and the side tube plate of the cylinder.

Images