Coal slime drying device based on coal mine ventilation air oxidation utilization

Abstract

The utility model relates to the technical field of coal mine waste comprehensive utilization, especially to a coal slime drying device based on coal mine ventilation air methane oxidation utilization, including gas oxidation device first heat recovery unit, secondary heat recovery unit, rotary dryer, rotary dryer, it has the rotating cylinder, rotating cylinder internal fixed array installs metal heat exchange pipe, rotating cylinder's air inlet is connected with secondary heat recovery unit's medium temperature air outlet through the pipeline, metal heat exchange pipe is connected with first heat recovery unit's high temperature air outlet through swivel joint, pipeline. The utility model will get high temperature flue gas after the ventilation air methane oxidation, and the high temperature air of grading heat exchange, medium temperature air, high temperature air and the coal slime of indirect heat exchange of waiting for drying, avoid contacting the flue gas containing gas, and high temperature air and the indirect heat exchange of coal slime adopt the rotary dryer of internally equipped fixed straight pipe, so that can utilize high temperature to promote the drying efficiency, and heating is more uniform.

Description

Technical Field

[0001] This utility model relates to the field of comprehensive utilization technology of coal mine waste, and in particular to a coal slime drying device based on the oxidation utilization of coal mine exhaust air. Background Technology

[0002] Exhaust air from coal mines is gas containing low concentrations of methane (typically 3-6%) discharged from the mine's ventilation system. Direct emission of this methane component would have a strong greenhouse effect. Thermal countercurrent oxidation devices can oxidize the methane in exhaust air into CO2 and H2O, releasing a large amount of heat energy, making it an effective means of utilizing exhaust air resources. On the other hand, coal slime is a high-moisture byproduct generated during coal washing, typically with a moisture content as high as 80%. Traditional coal slime drying technologies rely heavily on coal or steam, resulting in high energy consumption (700-1000 kWh per ton of coal slime for evaporation), significant pollution, and high operating costs.

[0003] Existing technologies have attempted to combine exhaust gas oxidation with coal slime drying, such as the utility model patent CN204718348U-Control System for High-Temperature Hot Air Production and Coal Slime Drying from Low-Concentration Methane Oxidation in Coal Mines. However, the following problems still exist: the outlet flue gas temperature of the hot countercurrent oxidation device exceeds 800℃. While the high-temperature flue gas has high drying efficiency, direct use can lead to equipment damage or uneven drying (the hot air temperature required for coal slime drying in existing technologies is usually 150-250℃). Furthermore, trace amounts of methane (<0.5%) may remain in the flue gas after oxidation. The high-temperature flue gas mixed with coal dust can form an explosive environment, posing a serious safety hazard. Utility Model Content

[0004] The main objective of this invention is to provide a coal slime drying device based on the oxidation and utilization of exhaust gas in coal mines, which better utilizes high-temperature flue gas to dry coal slime and improves safety. Better utilization of high-temperature flue gas for drying coal slime means retaining the high drying efficiency of high-temperature flue gas while reducing uneven drying.

[0005] To address the aforementioned problems, this invention improves upon existing technology by adding a staged heat recovery unit. The high-temperature flue gas from the oxidation device passes through this unit, where it is heated to produce high-temperature air in the primary heat recovery unit. The medium-temperature flue gas from the primary heat recovery unit is then heated to produce medium-temperature air in the same unit. Subsequently, the high-temperature air indirectly exchanges heat with the coal slime to be dried, while the low-temperature air directly exchanges heat with the coal slime.

[0006] Because the high-temperature air exchanges heat indirectly with the coal slime to be dried, the high-temperature air avoids contact with the gas-containing flue gas, thus solving the safety issue. The indirect heat exchange between the high-temperature air and the coal slime uses a rotary dryer with an internal fixed straight tube. This not only utilizes high temperature to improve drying efficiency, but also ensures more uniform heating through the rotary dryer.

[0007] Low-temperature flue gas also enters the rotary dryer, replacing the air under normal conditions, and directly exchanges heat with coal slime, making efficient use of the energy after the oxidation of coal mine exhaust air.

[0008] The specific plan is as follows.

[0009] A coal slime drying device based on coal mine exhaust gas oxidation utilization, including a gas oxidation device, and further comprising: The primary heat recovery unit is connected to the high-temperature flue gas outlet of the gas oxidation device, and is capable of heating air, and has a high-temperature air outlet and a medium-temperature flue gas outlet. The secondary heat recovery unit has its inlet connected to the medium-temperature flue gas outlet of the primary heat recovery unit, which can heat air and has a medium-temperature air outlet and a low-temperature flue gas outlet. A rotary dryer has a rotating cylinder with metal heat exchange tubes fixedly arranged inside the cylinder; the air inlet of the rotating cylinder is connected to the medium-temperature air outlet of the secondary heat recovery unit through a pipeline; the metal heat exchange tubes are connected to the high-temperature air outlet of the primary heat recovery unit through a rotary joint and a pipeline.

[0010] As a further improvement, the primary heat recovery unit employs a high-temperature ceramic regenerator.

[0011] As a further improvement, the secondary heat recovery unit adopts a shell-and-tube heat exchanger.

[0012] In a further improvement, the metal heat exchange tubes of the rotary dryer are straight tubes, parallel to the center line of the rotating cylinder.

[0013] In a further improvement, the metal heat exchange tubes are arranged in a ring array around the center line of the rotating cylinder, and are positioned close to the cylinder wall.

[0014] Further improvements include a coal slime feeding structure installed at the feed end of the rotary dryer.

[0015] As a further improvement, the low-temperature flue gas outlet is connected to a waste heat recovery device.

[0016] In a further improvement, the tail end of the metal heat exchange tube is connected to the air inlet of the rotating cylinder via a return air branch.

[0017] The technical solution of this invention has the following technical effects: This invention uses the high-temperature flue gas obtained after oxidation of exhaust gas to obtain high-temperature air and medium-temperature air through staged heat exchange. The high-temperature air exchanges heat indirectly with the coal slime to be dried, avoiding contact with the gas-containing flue gas. At the same time, the indirect heat exchange between the high-temperature air and the coal slime adopts a rotary dryer with a fixed straight tube inside. This can not only utilize high temperature to improve drying efficiency, but also make the heating more uniform. Attached Figure Description

[0018] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 A schematic diagram of the overall structure of a coal slime drying device based on the oxidation and utilization of coal mine exhaust air is shown. Figure 2 A schematic diagram of the rotary joint is shown.

[0019] In the picture: 1. Gas oxidation unit; 2. Primary heat recovery unit; 3. Secondary heat recovery unit; 4. Rotary dryer; 41. Metal heat exchange tubes; 5. Rotary joint; 51. Rotating part; 52. Fixed and moving parts 53. Sealing ring 54. Inner sealing ring 6. Coal slime feeding device. Detailed Implementation

[0020] The following will describe in detail the implementation of this application with reference to the accompanying drawings and embodiments, so that the implementation process of how this application uses technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly.

[0021] like Figure 1-2 As shown, the coal slime drying device based on the oxidation and utilization of coal mine exhaust gas mainly includes a gas oxidation device 1, a primary heat recovery unit 2, a secondary heat recovery unit 3, and a rotary dryer 4.

[0022] The gas oxidation device 1 oxidizes the coal mine exhaust air to generate high-temperature hot air. The high-temperature flue gas outlet of the primary heat recovery unit 2 of the gas oxidation device 1 is connected to the high-temperature flue gas outlet to heat the air using the high-temperature flue gas. It is equipped with a high-temperature air outlet and a medium-temperature flue gas outlet.

[0023] The inlet of the secondary heat recovery unit 3 is connected to the medium-temperature flue gas outlet of the primary heat recovery unit 2, and the medium-temperature flue gas heats the air. The secondary heat recovery unit 3 has a medium-temperature air outlet and a low-temperature flue gas outlet.

[0024] The rotary dryer 4 has a rotating cylinder, inside which metal heat exchange tubes 41 are fixedly arrayed. The feed inlet of the rotating cylinder is connected to the medium-temperature air outlet of the secondary heat recovery unit 3 via a pipeline. The metal heat exchange tubes 41 are connected to the high-temperature air outlet of the primary heat recovery unit via a rotary joint 5 and a pipeline. The primary heat recovery unit 2 uses a high-temperature ceramic regenerator, and the secondary heat recovery unit 3 uses a shell-and-tube heat exchanger.

[0025] The metal heat exchange tubes 41 of the rotary dryer 4 are straight tubes, parallel to the center line of the rotating cylinder. They are arranged in a ring array around the center line of the rotating cylinder, with the metal heat exchange tubes 41 positioned close to the cylinder wall.

[0026] The coal slime feeding device 6 is installed at the feed end of the rotary dryer's rotating cylinder. The rotating cylinder has an inclination angle of about 5 degrees, which causes the material to be driven and conveyed down the cylinder wall.

[0027] The air coming out of the metal heat exchange tube 41 is used as return air inside the tube. It is connected to the air inlet of the rotating cylinder through the return air branch, mixed with the medium-temperature air coming out of the secondary heat recovery unit 3, and enters the cylinder to heat and dry the coal slime.

[0028] The low-temperature flue gas from the secondary heat recovery unit 3, and the exhaust gas from the rear of the rotary dryer's rotating cylinder, can be connected to waste heat recovery equipment, such as waste heat power generation equipment or latent heat recovery equipment, for further energy recovery and utilization.

[0029] like Figure 2 The diagram shows the structure of the rotary joint 5. The rotary joint 5 comprises two parts: a rotating part 51, which is fixed to the end face of the rotating cylinder of the rotary dryer and connected to the outer wall of the medium-temperature air inlet pipe via a bearing; and a fixed part 52, which is fixed to the medium-temperature air inlet pipe and the working platform. The rotating part 52 and the fixed part 51 are connected by an outer sealing ring 53 and an inner sealing ring 54. A protective sleeve 55 is provided on the outside of the connection point.

[0030] The rotating part 51 includes a transverse annular cavity and radially arranged branch cavities. The outlets of the branch cavities pass through the cross-section of the cylinder and are connected to the metal heat exchange tubes 41 inside the cylinder. The fixed part 52 includes a transverse annular cavity that communicates with the annular cavity of the rotating part 51 and is provided with an air inlet.

[0031] The following describes the overall wind flow process.

[0032] The exhaust gas flow direction in coal mines is as follows: it is oxidized and released into high-temperature flue gas by the gas oxidation device, then becomes medium-temperature flue gas after passing through the first-stage heat recovery unit 2, and finally becomes low-temperature flue gas after passing through the second-stage heat recovery unit 2.

[0033] Airflow: One stream of air is heated by the primary heat recovery unit 2, becoming high-temperature hot air, and then enters the metal heat exchange tube 41 of the rotary dryer. The metal heat exchange tube 41 rotates with the cylinder, repeatedly contacting and heating the coal slime, thus breaking it up and playing a major role in drying the coal slime. Another stream of air is heated by the secondary heat recovery unit 3, becoming medium-temperature hot air, and enters the rotary dryer cylinder. It heats the coal slime through convection heat transfer and then exits from the tail end of the cylinder. The first stream of air exiting the metal heat exchange tube 41 can then enter the rotary dryer cylinder together with the medium-temperature hot air formed by the second stream through the return air branch. The fans are omitted in the diagram; they can be installed according to requirements.

[0034] As can be seen from the above working process, indirect heat exchange between high-temperature air and the coal slime to be dried avoids contact with methane-containing flue gas, ensuring safety. The metal heat exchange tubes inside the rotary dryer penetrate deep into the coal slime for drying, resulting in more uniform heating than simply using gas to dry the surface.

[0035] The above description is merely a preferred embodiment of this utility model and is not intended to limit the invention. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this utility model should be included within the protection scope of this invention.

Claims

1. A coal slime drying device based on the oxidation and utilization of coal mine exhaust gas, comprising a gas oxidation device, characterized in that, Also includes: The primary heat recovery unit is connected to the high-temperature flue gas outlet of the gas oxidation device, and is capable of heating air, and has a high-temperature air outlet and a medium-temperature flue gas outlet. The secondary heat recovery unit has its inlet connected to the medium-temperature flue gas outlet of the primary heat recovery unit, which can heat air and has a medium-temperature air outlet and a low-temperature flue gas outlet. A rotary dryer has a rotating cylinder with metal heat exchange tubes fixedly arranged inside the cylinder; the air inlet of the rotating cylinder is connected to the medium-temperature air outlet of the secondary heat recovery unit through a pipeline; the metal heat exchange tubes are connected to the high-temperature air outlet of the primary heat recovery unit through a rotary joint and a pipeline.

2. The coal slime drying device based on the oxidation and utilization of coal mine exhaust air as described in claim 1, characterized in that, The primary heat recovery unit employs a high-temperature ceramic regenerator.

3. The coal slime drying device based on the oxidation and utilization of coal mine exhaust air as described in claim 1, characterized in that, The secondary heat recovery unit uses a shell-and-tube heat exchanger.

4. The coal slime drying device based on the oxidation and utilization of coal mine exhaust air as described in claim 1, characterized in that, The metal heat exchange tubes of the rotary dryer are straight tubes, parallel to the center line of the rotating cylinder.

5. The coal slime drying device based on coal mine exhaust gas oxidation utilization as described in claim 4, characterized in that, The metal heat exchange tubes are arranged in a ring array around the center line of the rotating cylinder, and are positioned close to the cylinder wall.

6. The coal slime drying device based on the oxidation and utilization of coal mine exhaust air as described in claim 5, characterized in that, It also includes a coal slime feeding structure, installed at the feed end of the rotary dryer.

7. The coal slime drying device based on coal mine exhaust gas oxidation utilization as described in claim 1, characterized in that, The low-temperature flue gas outlet is connected to a waste heat recovery device.

8. The coal slime drying device based on coal mine exhaust gas oxidation utilization as described in claim 5, characterized in that, The tail end of the metal heat exchange tube is connected to the air inlet of the rotating cylinder through a return air branch.

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