Raw coal drying dust removal system with waste heat recovery function and raw coal drying method

Abstract

The invention discloses a raw coal drying dust removal system with a waste heat recovery function and a raw coal drying method. The raw coal drying dust removal system comprises a crushing assembly, an electric auxiliary heating rotary kiln, a cooling section rotary kiln, a gas-solid separator, a tail gas treatment dust removal assembly, a waste heat recovery heat exchanger and a heat pump system. The crushing assembly, the electric auxiliary heating rotary kiln and the cooling section rotary kiln are communicated in sequence; a first gas outlet of the electric auxiliary heating rotary kiln is communicated with the gas-solid separator; the gas-solid separator is communicated with the waste heat recovery heat exchanger through the tail gas treatment dust removal assembly; the heat pump system is connected with the cooling section rotary kiln and the waste heat recovery heat exchanger, and an air outlet of the heat pump system is communicated with an air inlet of the electric auxiliary heating rotary kiln. By means of the waste heat recovery heat exchanger and the heat pump system, originally discharged waste heat is recycled, energy consumption of electric auxiliary heating is reduced, and recovery and temperature rise of tail gas heat are achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of heat pump drying, in particular to a raw coal drying and dust removing system with waste heat recovery and a raw coal drying method. BACKGROUND

[0002] The briquettes made of coal gangue, semi-coke and coal slime raw materials have a large humidity when just made, and need to be dried to remove water. However, the ordinary heat pump drying system is not equipped with a suitable waste heat recovery device, and a large amount of latent heat is discharged with the tail gas and not effectively utilized, which makes the energy consumption advantage of the heat pump system not fully exerted, and the drying efficiency needs to be improved. At the same time, the ordinary heat pump system has limitations in providing a higher drying temperature, which limits its use in some application scenarios with higher requirements for drying temperature. SUMMARY

[0003] The technical problem to be solved by the present application is that the ordinary heat pump drying system is not equipped with a suitable waste heat recovery device, and a large amount of latent heat is discharged with the tail gas and not effectively utilized, which makes the energy consumption advantage of the heat pump system not fully exerted, and the drying efficiency needs to be improved.

[0004] To solve the above technical problems, the present application provides a raw coal drying and dust removing system with waste heat recovery, which comprises a crushing assembly, an electric auxiliary heat rotary kiln, a cooling section rotary kiln, a gas-solid separator, a tail gas treatment and dust removal assembly, a waste heat recovery heat exchanger and a heat pump system.

[0005] The crushing assembly, the electric auxiliary heat rotary kiln and the cooling section rotary kiln are sequentially connected to dry and cool the crushed raw coal to form materials;

[0006] The first gas outlet of the electric auxiliary heat rotary kiln is connected with the gas-solid separator to separate the first tail gas;

[0007] The gas-solid separator is connected with the waste heat recovery heat exchanger through the tail gas treatment and dust removal assembly to introduce the first tail gas after treatment and dust removal into the waste heat recovery heat exchanger for preliminary heat release;

[0008] The heat pump system is connected with the cooling section rotary kiln and the waste heat recovery heat exchanger to receive the mixed gas of the first tail gas after preliminary heat release and the second tail gas of the cooling section rotary kiln, and the first hot gas discharged from the waste heat recovery heat exchanger, so that the mixed gas and the first hot gas are heat exchanged to obtain the second hot gas, and the gas outlet of the heat pump system is connected with the gas inlet of the electric auxiliary heat rotary kiln to introduce the second hot gas into the electric auxiliary heat rotary kiln.

[0009] Further, the heat pump system comprises an evaporator, a condenser, a liquid-gas separator and valves, the evaporator, the condenser and the liquid-gas separator are sequentially connected in series, the liquid-gas separator is provided with the valves between the evaporator and the condenser, and the gas inlet of the evaporator is connected with the cooling section rotary kiln and the waste heat recovery heat exchanger to receive the mixed gas; the gas inlet of the condenser is connected with the waste heat recovery heat exchanger to receive the first hot gas, and the gas outlet of the condenser is communicated with the gas inlet of the electric auxiliary heating rotary kiln to guide the second hot gas into the electric auxiliary heating rotary kiln.

[0010] Further, the heat pump system further comprises two compressors and a first three-way valve, the two compressors are arranged between the evaporator and the condenser, and the first three-way valve is communicated with the two compressors and the liquid-gas separator.

[0011] Further, it further comprises a first fan, a second fan, a third fan and a second three-way valve, the gas-solid separator and the tail gas treatment and dust removal assembly are communicated through the first fan, the heat pump system is connected with the cooling section rotary kiln and the waste heat recovery heat exchanger through the second three-way valve to receive the mixed gas, the second three-way valve and the heat pump system are communicated through the second fan, and the gas outlet of the heat pump system is communicated with the gas inlet of the electric auxiliary heating rotary kiln through the third fan.

[0012] Further, the crushing assembly comprises a crusher, a shaking feeder and a connecting belt, the crusher is communicated with the shaking feeder, and the shaking feeder is connected with the electric auxiliary heating rotary kiln through the connecting belt.

[0013] Further, the tail gas treatment and dust removal assembly comprises a tail gas treatment device and a dust removal device, the gas-solid separator, the tail gas treatment device, the dust removal device and the waste heat recovery heat exchanger are sequentially communicated.

[0014] Further, the tail gas treatment and dust removal assembly further comprises a ball press, the ball press is communicated with the discharge end of the dust removal device to press the recovered small particle coal powder or material.

[0015] The application also provides a raw coal drying method applied to the raw coal drying and dust removal system with waste heat recovery, and the raw coal drying method comprises the following steps:

[0016] The raw coal is crushed and sieved into crushed materials of a first particle size, the first particle size is ≤20mm, and the sieve passing rate of the crushed materials is ≥95%;

[0017] Subsequently, the crushed material is transported to the electrically assisted heat rotary kiln, and high-temperature hot air is introduced, and the crushed material is dried for a preset time, and the temperature of the high-temperature hot air is 90-130 DEG C;

[0018] After drying, the crushed material is transported to the cooling section rotary kiln for cooling to a first temperature, and the exhaust gas flows to the gas-solid separator to separate the first tail gas, and the first temperature is < 30 DEG C;

[0019] The first tail gas flows to the tail gas treatment dust removal assembly and the waste heat recovery heat exchanger, and then flows to the heat pump system;

[0020] The mixed gas of the first tail gas and the second tail gas of the cooling section rotary kiln and the first hot gas discharged from the waste heat recovery heat exchanger are heat exchanged in the heat pump system to obtain the second hot gas, and the second hot gas is introduced into the electrically assisted heat rotary kiln.

[0021] Further, the outlet moisture of the crushed material in the electrically assisted heat rotary kiln, the first temperature and the preheating temperature rise of the cooling section rotary kiln are monitored;

[0022] If the outlet moisture is > 15%, the hot air temperature is automatically increased;

[0023] If the first temperature is > 30 DEG C, the cooling time is prolonged, the feeding speed is adjusted or the air volume of the cooling section rotary kiln is increased;

[0024] If the preheating temperature rise of the cooling section rotary kiln is < 5 DEG C, the air supply volume of the cooling section rotary kiln is reduced.

[0025] Further, the pressure difference of the waste heat recovery heat exchanger, the temperature and dust content of the first tail gas are monitored;

[0026] If the temperature of the first tail gas is > 40 DEG C, the air supply volume of the waste heat recovery heat exchanger is increased;

[0027] If the dust content of the first tail gas is > 30 mg / m 3 Or the pressure difference of the waste heat recovery heat exchanger is > 400 Pa, the high-pressure water washing or the pre-bag dust removal program is triggered.

[0028] Compared with the prior art, the coal drying and dust removal system and the coal drying method of the embodiment of the application have the beneficial effects that:

[0029] The embodiment of the present application recovers and reuses the originally discharged waste heat through the waste heat recovery heat exchanger and the heat pump system, reduces the energy consumption of the electric auxiliary heating, realizes the recovery and temperature rise of the tail gas heat, raises the low-temperature waste heat to a usable high-temperature heat source, improves the energy utilization efficiency, reduces the dependence on external heat sources (such as electric heating), solves the limitation of the heat pump system in providing a higher drying temperature, and makes it meet the large temperature rise environment and has the ability to provide high-temperature heat release at a lower ambient temperature. BRIEF DESCRIPTION OF DRAWINGS

[0030] The present application will be further described below in conjunction with the drawings and preferred embodiments, but those skilled in the art will appreciate that the drawings are only drawn for the purpose of explaining the preferred embodiments and thus should not be regarded as limiting the scope of the present application. In addition, unless specifically indicated, the drawings are only intended to conceptually represent the composition or structure of the described objects and can include exaggerated displays, and the drawings are not necessarily drawn to scale.

[0031] Figure 1 is a structural schematic diagram of a raw coal drying and dedusting system with waste heat recovery provided by the embodiment of the present application;

[0032] In the figure, 1, a crushing assembly; 101, a crusher; 102, a shaking feeder; 103, a connecting belt; 2, an electric auxiliary heating rotary kiln; 3, a cooling section rotary kiln; 4, a gas-solid separator; 5, a tail gas treatment and dedusting assembly; 501, a tail gas treatment device; 502, a dedusting device; 503, a ball press; 6, a waste heat recovery heat exchanger; 7, a heat pump system; 701, an evaporator; 702, a condenser; 703, a liquid-gas separator; 704, a valve; 705, a compressor; 706, a first three-way valve; 8, a first fan; 9, a second fan; 10, a third fan; 11, a second three-way valve. DETAILED DESCRIPTION

[0033] The embodiments of the present application are described in detail below, examples of which are shown in the drawings, wherein the same or similar reference numbers represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are intended to explain the present application, and should not be understood as limiting the present application.

[0034] In the description of the present application, it should be understood that the terms "first", "second" and the like are used to describe various information, but these information should not be limited to these terms, and these terms are only used to distinguish the same type of information from each other. For example, the "first" information can also be referred to as "second" information, and similarly, the "second" information can also be referred to as "first" information without departing from the scope of the present application.

[0035] As Figure 1As shown, the present application provides a raw coal drying and dust removal system with waste heat recovery, which comprises a crushing assembly 1, an electric auxiliary heating rotary kiln 2, a cooling section rotary kiln 3, a gas-solid separator 4, a tail gas treatment and dust removal assembly 5, a waste heat recovery heat exchanger 6 and a heat pump system 7; the crushing assembly, the electric auxiliary heating rotary kiln 2 and the cooling section rotary kiln 3 are sequentially communicated to dry and cool the crushed raw coal to form the material; wherein the crushing assembly 1 is used to crush the large raw coal into small particles suitable for drying treatment, so as to improve the drying efficiency and uniformity; the electric auxiliary heating rotary kiln 2 uses the electric heating auxiliary heat source to dry the crushed raw coal at high temperature, removes the moisture, and the high-temperature waste gas containing water vapor and dust is discharged from the first gas outlet during the drying process; the cooling section rotary kiln 3 cools the dried high-temperature coal, the rotation of the rotary kiln makes the material fully contact with the cooling air, the temperature of the material is reduced to the range required by the subsequent treatment process, which is convenient for subsequent conveying and storage, and the second tail gas with lower temperature is generated during the cooling process. The first gas outlet of the electric auxiliary heating rotary kiln 2 is communicated with the gas-solid separator 4 to separate the first tail gas and reduce the subsequent dust removal burden; the gas-solid separator 4 is communicated with the waste heat recovery heat exchanger 6 through the tail gas treatment and dust removal assembly 5 to guide the first tail gas after treatment and dust removal into the waste heat recovery heat exchanger 6 for preliminary heat release; wherein the tail gas treatment and dust removal assembly 5 treats and removes the dust of the tail gas after gas-solid separation (such as bag dust removal, electrostatic dust removal, etc.), so as to ensure that the emission meets the standard, and the waste heat recovery heat exchanger 6 uses the heat of the high-temperature first tail gas after dust removal to preheat other gases; the heat pump system 7 is connected with the cooling section rotary kiln 3 and the waste heat recovery heat exchanger 6 to receive the mixed gas of the first tail gas after preliminary heat release and the second tail gas of the cooling section rotary kiln 3 and the first hot gas discharged from the waste heat recovery heat exchanger 6, so that the mixed gas and the first hot gas are heat exchanged to obtain the second hot gas, that is, the heat pump system 7 as the core energy-saving device receives two gases, one is the mixed gas mixed by the first tail gas after preliminary heat release in the waste heat recovery heat exchanger 6 and the second tail gas generated by the cooling section rotary kiln 3, and the other is the first hot gas discharged from the waste heat recovery heat exchanger 6, the two gases are heat exchanged in the heat pump system 7 to generate the second hot gas. The gas outlet of the heat pump system 7 is communicated with the gas inlet of the electric auxiliary heating rotary kiln 2 to guide the second hot gas into the electric auxiliary heating rotary kiln 2 for recycling as hot air.

[0036] Based on the above structure, the raw coal of the embodiment is broken by the crushing assembly 1 and then enters the electric auxiliary heating rotary kiln 2 for drying. In this process, high-temperature waste gas is generated. The waste gas is introduced into the gas-solid separator 4 to separate the first tail gas, and the dried raw coal enters the cooling section rotary kiln 3 for cooling, which generates the second tail gas. The first tail gas is treated by the tail gas treatment and dust removal assembly 5, and then introduced into the waste heat recovery heat exchanger 6 for preliminary heat release. The first tail gas after heat release is mixed with the second tail gas and then enters the heat pump system 7. The gas introduced into the waste heat recovery heat exchanger 6 absorbs heat to generate the first hot gas, which is introduced into the heat pump system 7. In the heat pump system 7, the mixed gas exchanges heat with the first hot gas to generate the second hot gas, which is returned to the electric auxiliary heating rotary kiln 2 as a drying heat source, so as to realize the recycling of heat energy.

[0037] The embodiment recycles the waste heat by the waste heat recovery heat exchanger 6 and the heat pump system 7, reduces the energy consumption of the electric auxiliary heating, recovers and heats the tail gas, heats the low-temperature waste heat to a usable high-temperature heat source, improves the energy utilization efficiency, reduces the dependence on external heat sources (such as electric heating), solves the limitation of the heat pump system 7 in providing a higher drying temperature, so that it can meet the environment with a large temperature rise and has the ability to provide a high-temperature heat release at a lower environmental temperature.

[0038] It should be noted that the gas-solid separator 4 of the embodiment is a cyclone separator, which can separate the gas containing dust and solid particles by gas-solid separation. Through the cyclone separation principle, the solid particles in the gas are collected by sedimentation under the action of centrifugal force. In addition, the electric auxiliary heating rotary kiln 2 and the cooling section rotary kiln 3 are conventional electric auxiliary heating rotary kilns and cooling section rotary kilns, and their structures are not particularly limited. Compared with the traditional flue gas drying, the high-temperature waste gas of the first outlet of the electric auxiliary heating rotary kiln 2 does not contain sulfur, nitrogen and part of particulate matter when it enters the dust removal device, and has a lower dew point, which can effectively avoid the caking phenomenon existing in the tail gas dust removal of the traditional flue gas drying.

[0039] In actual application, the raw coal drying and dust removal system with waste heat recovery will introduce two new air streams. The first new air stream enters the waste heat recovery heat exchanger 6 to absorb the waste heat of the first tail gas, and then enters the heat pump system 7 to further absorb heat. The second hot gas after heat absorption is sent to the electric auxiliary heating rotary kiln 2. The other new air stream enters the cooling section rotary kiln 3 to absorb heat. The second tail gas of the cooling section rotary kiln 3 after heat absorption is mixed with the first tail gas of the waste heat recovery heat exchanger 6.

[0040] Further, the heat pump system 7 comprises an evaporator 701, a condenser 702, a liquid-gas separator 703, and a valve 704, the evaporator 701, the condenser 702, and the liquid-gas separator 703 are sequentially connected end to end, and the valve 704 is arranged between the liquid-gas separator 703 and the evaporator 701 and the condenser 702, the gas inlet of the evaporator 701 is connected with the cooling section rotary kiln 3 and the waste heat recovery heat exchanger 6 to receive the mixed gas, the gas inlet of the condenser 702 is connected with the waste heat recovery heat exchanger 6 to receive the first hot gas, and the gas outlet of the condenser 702 is communicated with the gas inlet of the electric auxiliary heating rotary kiln 2 to guide the second hot gas into the electric auxiliary heating rotary kiln 2.

[0041] Based on the above structure, the second tail gas discharged from the cooling section rotary kiln 3 and the first tail gas not completely utilized in the waste heat recovery heat exchanger 6 are mixed and guided into the evaporator 701, the mixed gas serves as a low-temperature heat source, transfers heat to the refrigerant in the evaporator 701 to evaporate the refrigerant, thereby realizing heat recovery, and the refrigerant enters the condenser 702 after being warmed and pressurized, releases heat to the refrigerant in the condenser 702 to condense the refrigerant and release heat at a higher temperature, at the same time, the first hot gas from the waste heat recovery heat exchanger 6 also enters the condenser 702 and absorbs the heat released by the condenser 702, the second hot gas produced is sent to the electric auxiliary heating rotary kiln 2 and used as preheating gas.

[0042] Further, the heat pump system 7 further comprises two compressors 705 and a first three-way valve 706, the two compressors 705 are arranged between the evaporator 701 and the condenser 702 and are responsible for compressing the refrigerant into high-temperature and high-pressure medium to provide energy for the transfer of heat from the low-temperature heat source to the high-temperature heat source, and the first three-way valve 706 is communicated with the two compressors 705 and the liquid-gas separator 703. The two-stage compression design of the present embodiment improves the system operation performance while reducing the pressure ratio of the single compressor 705, so that the heat pump system 7 has a higher condensing temperature and improves the coverage temperature range of the drying process.

[0043] Further, the first fan 8, the second fan 9, the third fan 10, and the second three-way valve 11 are further included, the gas-solid separator 4 and the tail gas treatment and dust removal assembly 5 are communicated through the first fan 8 to transport the first tail gas after gas-solid separation to the tail gas treatment and dust removal assembly 5 for further purification, the heat pump system 7 is connected with the cooling section rotary kiln 3 and the waste heat recovery heat exchanger 6 through the second three-way valve 11 to receive the mixed gas, the second three-way valve 11 and the heat pump system 7 are communicated through the second fan 9 to transport the mixed gas mixed through the second three-way valve 11 to the heat pump system 7 as a heat exchange medium, and the gas outlet of the heat pump system 7 is communicated with the gas inlet of the electric auxiliary heating rotary kiln 2 through the third fan 10 to send the second hot gas heated or tempered by the heat pump system 7 to the electric auxiliary heating rotary kiln 2 as hot air.

[0044] Further, the crushed material assembly 1 comprises a crusher 101 for crushing large pieces of raw coal into a specific particle size range by mechanical force (such as extrusion, impact, shear) to provide suitable size crushed material for subsequent processing steps, a shaking feeder 102 in communication with the crusher 101, and a connecting belt 103 connecting the shaking feeder 102 with the electric auxiliary heat rotary kiln 2.

[0045] The crusher 101 of the embodiment is a stepped pin tooth crusher 101, which can adjust the crushing particle size. According to the properties of the raw material and the requirements of the subsequent process, the parameters such as the pin tooth spacing can be flexibly adjusted to achieve precise crushing to adapt to the requirements of different production processes for the particle size of the material. In addition, by shaking, the crushed material is uniformly distributed and continuously moved in the chute, ensuring stable feeding of the subsequent equipment, and having good adaptability. It can handle materials of different particle sizes and different physical properties, such as sticky materials and fragile materials, without affecting the uniformity and stability of the feeding. The connecting belt 103 of the embodiment has good wear resistance and toughness, and has adjustable conveying speed and appropriate length.

[0046] Further, the tail gas treatment and dust removal assembly 5 comprises a tail gas treatment device 501 and a dust removal device 502, and the gas-solid separator 4, the tail gas treatment device 501, the dust removal device 502 and the waste heat recovery heat exchanger 6 are sequentially communicated.

[0047] The tail gas treatment device 501 of the embodiment is used to remove harmful gas components and other pollutants in the tail gas, so that the tail gas meets the environmental protection emission standard. The dust removal device 502 is used to remove solid particulate matter (dust) carried in the tail gas, and common ones are bag dust collectors, electric dust collectors, cyclone dust collectors, etc. Through gas-solid separation, dust removal and tail gas treatment, the embodiment effectively removes particulate matter and harmful gases in the tail gas, meets the emission standard, reduces air pollution, and recovers heat energy for preheating, etc., improves energy utilization efficiency, and reduces energy consumption.

[0048] Further, the tail gas treatment and dust removal assembly 5 further comprises a ball press 503 in communication with the discharge end of the dust removal device 502 to press the recovered small particle coal powder or material, realize solid waste resource utilization, reduce raw material waste, reduce production cost, and facilitate storage, transportation and subsequent use of the material. The ball press 503 of the embodiment should have appropriate mold design, pressure adjustment, and material ratio and additives to improve the quality of the pressed coal balls. Understandably, the ball press 503 belongs to conventional technology, and the above requirements are also conventional setting requirements and operations, so it will not be described in detail here.

[0049] The application also provides a raw coal drying method applied to the raw coal drying and dust removal system with waste heat recovery as described above, which comprises the following steps:

[0050] S110, crushing the raw coal and screening the crushed material to a first particle size, the first particle size being ≤20 mm, and the screening rate of the crushed material being ≥95%;

[0051] This step helps to improve the drying efficiency by obtaining crushed material with uniform and small particle size, so that the hot air can be more uniformly contacted with the coal, avoiding uneven drying or too long drying time of large pieces of coal, and improving the overall drying effect and system stability.

[0052] S120, then transporting the crushed material to the electric auxiliary heat rotary kiln 2 and introducing high-temperature hot air, drying for a preset time, and the temperature of the high-temperature hot air being 90-130°C;

[0053] The electric auxiliary heat rotary kiln 2 of this step is slowly rotated to make the coal material constantly turn over, wherein the coal material stays in the electric auxiliary heat rotary kiln 2 for 30-40 min, and the rotation speed of the kiln body can be flexibly adjusted according to the real-time feedback of the online moisture meter to ensure uniform heating, and the temperature requirement of 90-130°C can avoid coal quality deterioration or spontaneous combustion caused by high temperature.

[0054] It should be noted that the temperature is generated by the heat pump system 7 in a two-stage circulation dynamic temperature adjustment mode, which can be adjusted and controlled by adjusting the frequency of the compressor 705.

[0055] S130, transporting the dried crushed material to the cooling section rotary kiln 3 for cooling to a first temperature, and the waste gas flowing to the gas-solid separator 4 to separate a first tail gas, and the first temperature being <30°C;

[0056] The cooling in this step is to prevent high-temperature coal material from spontaneous combustion during subsequent storage or transportation, and the gas-solid separator 4 removes coal dust in the tail gas to avoid pollution or blockage of subsequent equipment, while reducing dust emission.

[0057] S140, the first tail gas flows to the heat pump system 7 after passing through the tail gas treatment and dust removal assembly 5 and the waste heat recovery heat exchanger 6;

[0058] This step performs dust removal to ensure that the first tail gas is clean and meets environmental emission standards, and in addition, the waste heat recovery heat exchanger 6 extracts heat from the tail gas for preheating fresh air, improving energy utilization.

[0059] S150, the mixed gas of the first tail gas and the second tail gas of the cooling section rotary kiln 3 and the first hot gas discharged from the waste heat recovery heat exchanger 6 are heat exchanged in the heat pump system 7 to obtain a second hot gas, and the second hot gas is introduced into the electric auxiliary heat rotary kiln 2.

[0060] The heat pump system 7 of this step consumes a small amount of electric energy to improve low-temperature waste heat into reusable hot air, realizing heat air recycling, greatly reducing heat energy consumption, and reducing energy consumption.

[0061] The raw coal drying method is a process integrating crushing, drying, cooling, dust removal, waste heat recovery and heat pump reuse. The low-temperature waste heat is converted into usable hot air by the heat pump system 7, realizing low energy consumption, high efficiency and environmental protection of coal drying.

[0062] It should be noted that if the particle size of the crushed material exceeds the standard, the gap of the crusher 101 or the screen mesh should be adjusted; at the same time, dust and impurities are removed, and the initial moisture content of the raw material should be 20%-60%. If the moisture content is >60%, the pre-ventilation time should be extended, the third fan 10 should be adjusted to a wind speed of 2-3 m / s, and the surface moisture should be reduced to prepare for subsequent drying. In actual application, the tail gas humidity is also monitored in real time. In the waste heat recovery heat exchanger 6, 26% of the sensible heat is preliminarily recovered to preheat fresh air, and then in the evaporator 701, 57% of the latent heat of the tail gas is deeply recovered, further reducing energy consumption.

[0063] Further, the outlet moisture of the crushed material in the electric auxiliary heat rotary kiln 2, the first temperature, and the preheating temperature rise of the fresh air in the cooling section rotary kiln 3 are monitored;

[0064] If the outlet moisture is >15%, the hot air temperature is automatically increased. Understandably, when the outlet moisture of the crushed material exceeds 15%, it indicates that the drying is insufficient, and the system automatically increases the hot air temperature to enhance the drying capacity, so that the moisture evaporation is more complete, the outlet moisture meets the standard, the product quality consistency is improved, and the subsequent processing difficulty or product unqualification caused by moisture is avoided.

[0065] If the first temperature is >30℃, the cooling time is extended, the feeding speed is adjusted, or the air volume of the fresh air in the cooling section rotary kiln 3 is increased. Understandably, if the first temperature is higher than 30℃, it indicates that the material is not fully cooled. The cooling time is extended by reducing the speed or stopping time, or the feeding speed is adjusted, such as reducing the feeding, or the cooling fresh air volume is increased to enhance the cooling effect, so as to prevent the high-temperature material from affecting the subsequent transportation, storage or causing safety hazards (such as spontaneous combustion), and to protect the equipment.

[0066] If the preheating temperature rise of the fresh air in the cooling section rotary kiln 3 is <5℃, the air supply volume of the fresh air in the cooling section rotary kiln 3 is reduced. Understandably, the smaller the temperature rise of the fresh air, the less the heat exchange between the air and the crushed material, which may be due to the excessive air volume, and the air is not fully absorbed heat before being discharged, resulting in waste of heat energy. Reducing the air supply volume makes the air stay in the cooling section rotary kiln 3 for a longer time to absorb more heat, increases the preheating temperature, improves the heat recovery efficiency, reduces energy waste, and avoids excessive cooling or excessive air volume affecting the system balance.

[0067] Further, the pressure difference of the waste heat recovery heat exchanger 6, the temperature and dust content of the first tail gas are monitored;

[0068] If the temperature of the first tail gas is > 40℃, increase the fresh air supply of the waste heat recovery heat exchanger 6; Understandably, when the waste heat is not fully recovered, the heated fresh air needs to be increased into the heat exchanger to absorb more heat in the first tail gas, and improve the waste heat recovery efficiency.

[0069] If the dust content of the first tail gas is > 30mg / m 3 or the pressure difference of the waste heat recovery heat exchanger 6 is > 400Pa, trigger the high-pressure water washing or pre-bag dust removal program. Understandably, the dust concentration in the first tail gas exceeds the standard, which may cause dust accumulation, resulting in pollution of the waste heat recovery heat exchanger 6 or too large internal resistance of the waste heat recovery heat exchanger 6. The surface of the waste heat recovery heat exchanger 6 is washed with water to remove dust and dirt. The pre-bag dust removal program is started, which can reduce the dust entering the waste heat recovery heat exchanger 6, prevent the waste heat recovery heat exchanger 6 from being blocked and corroded, maintain efficient heat transfer, prolong the service life of the equipment, reduce the frequency of manual maintenance, ensure the continuous and stable operation of the system, and avoid shutdown due to blockage.

[0070] In summary, the embodiment of the present application provides a raw coal drying and dust removal system with waste heat recovery and a raw coal drying method. The waste heat recovery heat exchanger 6 and the heat pump system 7 recycle the waste heat that is originally discharged, reduce the energy consumption of electric auxiliary heating, realize the recovery and temperature rise of tail gas heat, raise the low-temperature waste heat to a usable high-temperature heat source, improve the energy utilization efficiency, reduce the dependence on external heat sources (such as electric heating), and solve the limitations of the heat pump system 7 in providing higher drying temperature, so that it can meet the large temperature rise environment and has the ability to provide high-temperature heat release at a lower ambient temperature.

[0071] The above only describes the preferred embodiments of the present application. It should be noted that for those skilled in the art, without departing from the technical principles of the present application, several improvements and replacements can be made, which should also be considered as the protection scope of the present application.

Claims

1. A raw coal drying and dust removal system with waste heat recovery, characterized in that, It includes a crushing assembly, an electrically heated rotary kiln, a cooling section rotary kiln, a gas-solid separator, a tail gas treatment and dust removal assembly, a waste heat recovery heat exchanger, and a heat pump system. The crushing assembly, the electrically heated rotary kiln, and the cooling section rotary kiln are connected in sequence to crush the raw coal and then dry and cool it to form material. The first gas outlet of the electrically heated rotary kiln is connected to the gas-solid separator to separate the first tail gas. The gas-solid separator is connected to the waste heat recovery heat exchanger through the tail gas treatment and dust removal component, so as to introduce the first tail gas after dust removal into the waste heat recovery heat exchanger for preliminary heat release. The heat pump system is connected to the rotary kiln in the cooling section and the waste heat recovery heat exchanger to receive the mixed gas of the first exhaust gas after preliminary heat release and the second exhaust gas of the rotary kiln in the cooling section, as well as the first hot gas discharged from the waste heat recovery heat exchanger, so that the mixed gas exchanges heat with the first hot gas to obtain the second hot gas. The outlet of the heat pump system is connected to the inlet of the electric auxiliary heating rotary kiln to introduce the second hot gas into the electric auxiliary heating rotary kiln.

2. The raw coal drying and dust removal system with waste heat recovery according to claim 1, characterized in that, The heat pump system includes an evaporator, a condenser, a liquid-gas separator, and valves. The evaporator, condenser, and liquid-gas separator are connected sequentially. The valves are installed between the liquid-gas separator and the evaporator and the condenser. The air inlet of the evaporator is connected to the rotary kiln in the cooling section and the waste heat recovery heat exchanger to receive the mixed gas. The air inlet of the condenser is connected to the waste heat recovery heat exchanger to receive the first hot gas. The air outlet of the condenser is connected to the air inlet of the electric auxiliary heating rotary kiln to introduce the second hot gas into the electric auxiliary heating rotary kiln.

3. The raw coal drying and dust removal system with waste heat recovery according to claim 2, characterized in that, The heat pump system also includes two compressors and a first three-way valve. The two compressors are located between the evaporator and the condenser, and the first three-way valve is connected to the two compressors and the liquid-gas separator, respectively.

4. The raw coal drying and dust removal system with waste heat recovery according to claim 1, characterized in that, It also includes a first fan, a second fan, a third fan, and a second three-way valve. The gas-solid separator and the exhaust gas treatment and dust removal assembly are connected through the first fan. The heat pump system is connected to the cooling section rotary kiln and the waste heat recovery heat exchanger through the second three-way valve to receive the mixed gas. The second three-way valve is connected to the heat pump system through the second fan. The outlet of the heat pump system is connected to the inlet of the electric auxiliary heating rotary kiln through the third fan.

5. The raw coal drying and dust removal system with waste heat recovery according to claim 1, characterized in that, The material crushing assembly includes a crusher, a vibrating feeder, and a connecting belt. The crusher is connected to the vibrating feeder, and the vibrating feeder is connected to the electrically heated rotary kiln via the connecting belt.

6. The raw coal drying and dust removal system with waste heat recovery according to claim 1, characterized in that, The exhaust gas treatment and dust removal assembly includes an exhaust gas treatment device and a dust removal device, wherein the gas-solid separator, the exhaust gas treatment device, the dust removal device, and the waste heat recovery heat exchanger are connected in sequence.

7. The raw coal drying and dust removal system with waste heat recovery according to claim 6, characterized in that, The exhaust gas treatment and dust removal assembly also includes a briquetting machine, which is connected to the discharge end of the dust removal equipment to press and recover small granular coal powder or materials.

8. A method for drying raw coal, characterized in that, The raw coal drying and dust removal system with waste heat recovery as described in any one of claims 1-7, wherein the raw coal drying method comprises the following steps: The raw coal is crushed and screened into a first particle size, the first particle size being ≤20mm, and the screening rate of the crushed material being ≥95%. The crushed material is then transported to an electrically heated rotary kiln and circulated with high-temperature hot air for a preset drying time. The temperature of the high-temperature hot air is 90-130°C. The dried crushed material is transported to the rotary kiln in the cooling section for cooling to a first temperature. The waste gas flows to the gas-solid separator to separate the first tail gas. The first temperature is <30℃. The first exhaust gas flows to the heat pump system after passing through the exhaust gas treatment and dust removal components and the waste heat recovery heat exchanger. The mixture of the first tail gas and the second tail gas from the cooling section rotary kiln, along with the first hot gas discharged from the waste heat recovery heat exchanger, undergoes heat exchange within the heat pump system to obtain the second hot gas, which is then introduced into the electrically auxiliary heating rotary kiln.

9. The method for drying raw coal according to claim 8, characterized in that, The outlet moisture content of the crushed material in the electrically assisted heating rotary kiln, the first temperature, and the preheating temperature rise of the fresh air in the cooling section rotary kiln are monitored. If the outlet moisture content is greater than 15%, the hot air temperature will be automatically increased. If the first temperature is >30°C, then extend the cooling time, adjust the feeding speed, or increase the fresh air volume in the rotary kiln of the cooling section; If the preheating temperature rise of the fresh air in the rotary kiln of the cooling section is less than 5°C, reduce the air supply volume of the fresh air in the rotary kiln of the cooling section.

10. The method for drying raw coal according to claim 8, characterized in that, The pressure difference of the waste heat recovery heat exchanger, the temperature of the first exhaust gas, and the dust content are monitored. If the temperature of the first exhaust gas is >40℃, increase the fresh air supply volume of the waste heat recovery heat exchanger; If the dust content of the first exhaust gas is >30mg / m³ 3 If the pressure difference of the waste heat recovery heat exchanger is >400Pa, a high-pressure water wash or pre-filter dust removal procedure will be triggered.

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