Low-calorific-value coal drying system

Abstract

The utility model relates to the technical field of coal-fired power plants, and discloses a low-calorific-value coal drying system which comprises an air heater, a drying oven and a processing device which are connected together to form a circulation structure, the air heater is communicated with the drying oven through an air duct, low-calorific-value coal to be dried is contained in the drying oven, and the air heater provides high-temperature airflow for drying for the drying oven. The oven is further connected with a treatment device for dedusting and cooling tail gas discharged by the oven, the oven and the treatment device are communicated through an air duct, and the treatment device is communicated with the heater through an air duct. The device has the beneficial effects of greatly saving resources, protecting the environment, saving manpower, reducing the drying cost, improving the drying efficiency and saving the labor cost.

Description

Technical Field

[0001] The utility model relates to the technical field of coal-fired power plants, in particular to a low calorific value coal drying system. Background Art

[0002] Fossil fuels are non-renewable resources. In order to adapt to changes in the energy structure, many power plants have begun to burn low-calorific value coal. Low-calorific value coal is coal that produces less heat when completely burned. If low-calorific value coal is discarded, it will waste resources and pollute the environment. Measures can be taken to recycle it, but the moisture content in low-calorific value coal is too high. Currently, low-calorific value coal is widely used in coal-fired power plants. Due to its high moisture content, easy wall adhesion and easy agglomeration, it becomes difficult to transport low-calorific value coal for boiler combustion.

[0003] There are many ways to mix low calorific value coal in power plants. The most common way is to mix low calorific value coal with coal powder and send it into the pulverizer. Another way is to use a booster pump to spray low calorific value coal into the furnace from the top of the furnace at high pressure. Both forms may cause low calorific value coal to be blocked in the pipeline. Low calorific value coal has a high moisture content and a calorific value of 2000 to 3000 kcal / kg. When mixed with low calorific value coal, it will affect the efficiency of the boiler, that is, the low calorific value coal is often dried first.

[0004] The existing low calorific value coal drying method easily causes energy waste and causes environmental pollution due to exhaust gas emissions. The exhaust gas is also subject to emission requirements, resulting in high drying costs and low efficiency. Utility Model Content

[0005] In order to overcome the problems of energy waste and environmental pollution caused by exhaust gas emissions in the low calorific value coal drying method in the above-mentioned background technology, the utility model provides a low calorific value coal drying system, which can achieve zero exhaust gas emissions by forming a circulating structure of a warm air device, an oven and a processing device, and the airflow used for heating can be recycled, which has the beneficial effects of greatly saving resources, protecting the environment, saving manpower, reducing drying costs, improving drying efficiency and saving labor costs.

[0006] The technical solution of the utility model is as follows:

[0007] A low calorific value coal drying system comprises a warm air device, an oven and a processing device connected together to form a circulation structure, the warm air device is connected to the oven through an air duct, the oven is filled with low calorific value coal to be dried, the warm air device provides a high-temperature airflow for drying the oven, the oven is also connected to a processing device for dust removal and cooling of exhaust gas discharged from the oven, the two are connected through the air duct, and the processing device is connected to the warm air device through the air duct.

[0008] Compared with the prior art, the beneficial effects of this technical solution are:

[0009] (1) This system uses convection heat exchange to dry low calorific value coal. By transferring heat through convection heat exchange, the high-temperature airflow heated in the warm air device is introduced into the drying oven, and the high-temperature airflow and the low calorific value coal are subjected to convection heat exchange, thereby increasing the calorific value of the low calorific value coal in the drying oven, drying the low calorific value coal, and solving the problem of low calorific value coal being blocked in the pipeline due to adhesion;

[0010] (2) The entire system uses recycled airflow to fully utilize energy while not emitting exhaust gas to the outside, thus avoiding environmental pollution caused by exhaust gas emissions, reducing drying costs and improving drying efficiency;

[0011] (3) The entire process can be automated, saving labor costs.

[0012] Preferably, the heating device comprises an air heater, the heating channel of the air heater is a closed cavity, and a plurality of evenly arranged heating pipes are arranged inside the cavity. High-temperature steam flows through the heating pipes to heat the airflow passing through the heating channel.

[0013] Further preferably, the air inlet of the heating pipe is connected to the low-pressure steam pipe of the steam turbine to provide a heating steam source for the warm air device.

[0014] Further preferably, the outlet of the heating pipe is connected to a water tank, and the water tank transports the condensed water to the deaerator through a water pump for recycling.

[0015] Preferably, the processing device comprises a dust collector, and the air inlet of the dust collector is connected to the air outlet of the oven through an air duct.

[0016] Further preferably, the processing device also includes a cooling device, which includes a first-stage heat exchanger and a second-stage heat exchanger with a closed structure, the air outlet of the dust collector is connected to the air inlet of the first-stage heat exchanger through an air duct, cooling water flows through the heat exchange pipe of the first-stage heat exchanger, and is connected to the heat exchange pipe of the second-stage heat exchanger through a circulating water pipe, and the air outlet of the first-stage heat exchanger is connected to the air inlet of the second-stage heat exchanger through the air duct, and the air outlet of the second-stage heat exchanger is connected to the air inlet of the heating device through the air duct.

[0017] Further preferably, a circulating fan is provided on the air duct connecting the first-stage heat exchanger and the second-stage heat exchanger.

[0018] Further preferably, the water inlet of the heat exchange pipe of the first-stage heat exchanger is connected to the water outlet of the condensation tower through a circulating water pipe, and the condensation tower provides cooling water for it. The water outlet of the heat exchange pipe of the second-stage heat exchanger is connected to the water inlet of the condensation tower through a circulating water pipe, thereby realizing the recycling of cooling water.

[0019] Further preferably, a circulating water pump is provided on the circulating water pipeline connecting the first-stage heat exchanger and the condensing tower.

[0020] Further preferably, the air duct is made of steel plate to form a closed air circulation system. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention will be described with reference to the accompanying drawings, in which:

[0022] Figure 1 It is a schematic diagram of the overall structure of the utility model.

[0023] Figure numerals: heating device 1, heater 10, heating channel 11, heating pipe 110, steam turbine 12, water tank 13, water pump 14, deaerator 15, oven 2, feeding port 21, discharge port 22, conveyor belt 23, dust collector 3, cooling device 4, first-stage heat exchanger 41, second-stage heat exchanger 42, heat exchange pipe 43, condensation tower 44, circulating water pipe 45, circulating water pump 46, air duct 5, circulating fan 51. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the utility model more clear, the utility model is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the utility model and are not used to limit the utility model.

[0025] Example 1: Figure 1 The low calorific value coal drying system shown in the figure comprises a heating device 1, an oven 2 and a processing device connected together to form a circulation structure, the air outlet of the heating device 1 is connected to the air inlet of the oven 2 through an air duct 5, the oven 2 is filled with low calorific value coal to be dried, the heating device 1 provides a high-temperature airflow for drying for the oven 2, the air outlet of the oven 2 is connected to a processing device for dust removal and cooling of the exhaust gas discharged from the oven 2, the air outlet of the oven 2 is connected to the air inlet of the processing device through the air duct 5, and the air outlet of the processing device is connected to the heating device 1. The air inlet is connected through the air duct 5. The top of the oven 2 is also provided with a feed port 21, and the bottom is provided with a discharge port 22. Several conveyor belts 23 arranged in the horizontal direction are fixed from top to bottom in the oven 2. The running directions of adjacent conveyor belts 23 are opposite. The low calorific value coal at the end of each layer of conveyor belt 23 must fall into the starting point of the adjacent conveyor belt below it, that is, the starting point of each layer of conveyor belt 23 extends to the running direction of the adjacent conveyor belt 23 above it, and the starting point of each conveyor belt 23 must exceed the end point of the adjacent conveyor belt 23 above it. All the air ducts 5 in this system are made of steel plates to form a closed air circulation system.

[0026] The low calorific value coal enters the conveyor belt 23 from the feed port 21 and reaches the discharge port 22 along the conveying direction of the conveyor belt, and the high-temperature airflow generated in the warm air device 1 enters the oven 2 from the air inlet through the air duct 5 and flows along each layer of the conveyor belt 23 to fully contact with the low calorific value coal. The high-temperature airflow performs convection heat exchange with the low calorific value coal, so that the moisture in the low calorific value coal on the conveyor belt 23 evaporates and is carried by the flowing high-temperature airflow to enter the processing device from the air outlet of the oven 2. The airflow after fully contacting with the low calorific value coal for convection heat exchange contains more coal powder and water vapor. The processing device can remove dust and dry it, absorb the coal powder and water vapor therein, and the airflow after dust removal and drying enters the warm air device 1 through the air duct 5 again, and is heated again to become high-temperature airflow, forming a circulating drying system.

[0027] This system uses convection heat exchange to dry low calorific value coal, transfers heat through convection heat exchange, and flows the high-temperature airflow heated in the warm air device 1 into the drying oven 2, and performs convection heat exchange between the high-temperature airflow and the low calorific value coal, thereby increasing the calorific value of the low calorific value coal in the drying oven 2, drying the low calorific value coal, and solving the problem of low calorific value coal being blocked in the pipeline due to adhesion; the whole system adopts recycled airflow, fully utilizing energy while not emitting exhaust gas to the outside, avoiding environmental pollution caused by exhaust gas emission, reducing drying costs, and improving drying efficiency; the whole process can be automated, saving labor costs.

[0028] Embodiment 2: Based on Embodiment 1, a preferred design of the heating device 1 is performed. The heating device 1 includes a heater 10. The heating channel 11 of the heater 10 is a closed cavity. A plurality of heating pipes 110 are evenly laid in the heating channel 11. High-temperature steam flows through the heating pipes 110. The heat in the high-temperature steam is transferred to the airflow in the heating channel 11 by convection heat exchange. The airflow entering the heater 10 is in full contact with the surface of the heating pipe 110 to cause relative displacement, thereby forming a high-temperature airflow.

[0029] Furthermore, the air inlet of the heating pipe 110 is connected to the air outlet of the low-pressure steam pipe of the turbine 12. The turbine 12 provides a heating steam source for the warm air device 1, and the low-pressure steam temperature is above 200°. The outlet of the heating pipe 110 is connected to the water tank 13. The low-pressure steam after convective heat exchange in the heating pipe 110 condenses into water and collects in the water tank 13. The water tank 13 then transports the condensed water to the deaerator 15 through the water pump 14 for recycling. The low-pressure steam generated by the steam turbine 12 in the power plant is often directly converted into condensed water through the condenser, and the heat therein is released into the atmosphere without being utilized. In this embodiment, the heating pipe 110 is connected to the low-pressure steam pipe of the steam turbine 12. The low-pressure steam heats the airflow in the heating channel 11 through the heating pipe 110 to increase the calorific value of the coal. This can fully utilize the heat in the low-pressure steam and at the same time, the low-pressure steam also completes the condensation effect, which can greatly improve the economy of the power plant, save energy and reduce consumption, ensure safe operation, further improve the utilization rate of resources, and be more energy-saving and environmentally friendly.

[0030] Embodiment 3: Based on Embodiment 1, the processing device is optimally designed, and the processing device includes a dust collector 3 and a cooling device 4, wherein the dust collector 3 is a bag-type dust collector 3, and the bag-type dust collector 3 has the advantages of large air volume per unit volume, high dust removal efficiency, low energy consumption, stability and reliability. The air inlet of the dust collector 3 is connected with the air outlet of the oven 2 through the air duct 5, and the airflow flowing out of the oven 2 enters the dust collector 3, and then enters the cooling device 4 after filtering the coal powder from the dust collector 3.

[0031] The cooling device 4 includes a first-stage heat exchanger 41 and a second-stage heat exchanger 42 of a closed structure. The air outlet of the dust collector 3 is connected to the air inlet of the first-stage heat exchanger 41 through an air duct 5. Cooling water flows through the heat exchange pipe 43 of the first-stage heat exchanger 41. The heat exchange pipe 43 is connected to the heat exchange pipe 43 of the second-stage heat exchanger 42 through a circulating water pipe 45. The air outlet of the first-stage heat exchanger 41 is connected to the air inlet of the second-stage heat exchanger 42 through the air duct 5. The air outlet of the second-stage heat exchanger 42 is connected to the air inlet of the warm air device 1 through the air duct 5. Among them, a circulating fan 51 is provided on the air duct 5 connecting the first-stage heat exchanger 41 and the second-stage heat exchanger 42 to provide overall air circulation power. A blower is also provided at the position of the air duct 5 before the circulating fan 51. The blower blows air when the system is started, and the blower is directly cut off after operation, and the air flow circulates automatically.

[0032] The airflow entering the first-stage heat exchanger 41 from the air outlet of the dust collector 3 still has a certain temperature, which is above 100°C. When passing through the surface of the heat exchange pipe 43 of the first-stage heat exchanger 41, since cooling water is passed through the above-mentioned heat exchange pipe 43, the hot air flow will perform convection heat exchange with the cooling water in the heat exchange pipe 43 to heat the cooling water. At the same time, its own temperature drops to below 100°C, and the water vapor carried in the hot air flow condenses. The condensed water is collected by the collection box under the first-stage heat exchanger 41, and the hot air flow completes its own dehydration. The above-mentioned heat exchange pipe 43 is connected to the heat exchange pipe 43 of the second-stage heat exchanger 42, and the air outlet of the first-stage heat exchanger 41 is connected to the second-stage heat exchanger 42. The air inlet of the secondary heat exchanger 42 is connected through the air duct 5, so the hot water heated in the heat exchange pipe 43 of the first-stage heat exchanger 41 enters the heat exchange pipe 43 of the second-stage heat exchanger 42, and the cold air flow after cooling and drying in the first-stage heat exchanger 41 enters the second-stage heat exchanger 42 and contacts the surface of the heat exchange pipe 43 of the second-stage heat exchanger 42. The cold air flow then performs convection heat exchange with the hot water in the heat exchange pipe 43, and the cold air flow itself is heated, and the heated air flow enters the warm air device 1 for recycling, and the heating of the air flow by the second-stage heat exchanger 42 and the warm air device 1 can further reduce its moisture content, so that the high-temperature air flow can achieve a better drying effect.

[0033] Since the water vapor in the airflow has a saturation degree, the airflow exceeding the saturation degree will not be able to carry excess water vapor, and the hot air temperature at the outlet of the dust collector 3 is higher than 100°C, and direct discharge will cause a large amount of heat loss. In order to reduce the heat loss, a cooling device 4 is provided at the outlet of the dust collector 3 in this embodiment, which can reduce the water vapor content in the airflow, reduce heat loss, and recycle the airflow, while reducing the energy loss caused by discharge, and maximizing the use of energy. This process greatly improves the utilization rate of heat in the low-pressure steam of the turbine 12, and is energy-saving and efficient.

[0034] Furthermore, the water inlet of the heat exchange pipe 43 of the first-stage heat exchanger 41 is connected to the water outlet of the condensation tower 44 through a circulating water pipe 45. The condensation tower 44 provides cooling water for the first-stage heat exchanger 41. The circulating water pipe 45 is provided with a circulating water pump 46. The circulating water pump 46 provides circulation power for water circulation. The water outlet of the heat exchange pipe 43 of the second-stage heat exchanger 42 is connected to the water inlet of the condensation tower 44 through the circulating water pipe 45. Thus, the hot water in the second-stage heat exchanger 42 passes heat to the air flow through convection heat exchange and enters the condensation tower 44 for cooling, thereby realizing the recycling of cooling water, saving water resources, and further improving resource utilization.

[0035] The above embodiments only express the specific implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the protection scope of the present application. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the technical solution concept of the present application, and these all belong to the protection scope of the present application.

Claims

1. A low calorific value coal drying system, characterized in that: The invention comprises a warm air device (1), an oven (2) and a processing device which are connected together to form a circulation structure. The warm air device (1) is connected to the oven (2) through an air duct (5). The oven (2) contains low calorific value coal to be dried. The warm air device (1) provides a high-temperature airflow for drying the oven (2). The oven (2) is also connected to a processing device for removing dust and cooling the exhaust gas discharged from the oven (2). The two are connected through the air duct (5). The processing device is connected to the warm air device (1) through the air duct (5).

2. A low calorific value coal drying system according to claim 1, characterized in that: The heating device (1) comprises a heater (10), wherein a heating channel (11) of the heater (10) is a closed cavity, and a plurality of evenly arranged heating pipes (110) are arranged inside the heating pipes (110), and high-temperature steam flows through the heating pipes (110) to heat the airflow passing through the heating channel (11).

3. A low calorific value coal drying system according to claim 2, characterized in that: The air inlet of the heating pipe (110) is in communication with the low-pressure steam pipe of the steam turbine (12), providing a heating steam source for the warm air device (1).

4. A low calorific value coal drying system according to claim 2, characterized in that: The outlet of the heating pipe (110) is connected to a water tank (13), and the water tank (13) transports condensed water to a deaerator (15) for recycling via a water pump (14).

5. A low calorific value coal drying system according to claim 1, characterized in that: The processing device comprises a dust collector (3), and the air inlet of the dust collector (3) is connected to the air outlet of the oven (2) through an air duct (5).

6. A low calorific value coal drying system according to claim 5, characterized in that: The treatment device also includes a cooling device (4), which includes a first-stage heat exchanger (41) and a second-stage heat exchanger (42) of a closed structure. The air outlet of the dust collector (3) is connected to the air inlet of the first-stage heat exchanger (41) through an air duct (5). Cooling water flows through the heat exchange pipe (43) of the first-stage heat exchanger (41) and is connected to the heat exchange pipe (43) of the second-stage heat exchanger (42) through a circulating water pipe (45). The air outlet of the first-stage heat exchanger (41) is connected to the air inlet of the second-stage heat exchanger (42) through the air duct (5), and the air outlet of the second-stage heat exchanger (42) is connected to the air inlet of the heating device (1) through the air duct (5).

7. A low calorific value coal drying system according to claim 6, characterized in that: A circulating fan (51) is provided on the air duct (5) connecting the first-stage heat exchanger (41) and the second-stage heat exchanger (42).

8. A low calorific value coal drying system according to claim 6, characterized in that: The water inlet of the heat exchange pipe (43) of the first-stage heat exchanger (41) is connected to the water outlet of the condensation tower (44) through a circulating water pipe (45), and the condensation tower (44) provides cooling water for it. The water outlet of the heat exchange pipe (43) of the second-stage heat exchanger (42) is connected to the water inlet of the condensation tower (44) through a circulating water pipe (45), thereby realizing the recycling of cooling water.

9. A low calorific value coal drying system according to claim 8, characterized in that: A circulating water pump (46) is provided on the circulating water pipeline (45) connecting the first-stage heat exchanger (41) and the condensing tower (44).

10. A low calorific value coal drying system according to any one of claims 1 to 9, characterized in that: The air duct (5) is made of steel plates to form a closed air circulation system.

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