Pebble coal waste heat utilization system and pebble coal waste heat utilization method for coal-fired unit coupling heat insulation furnace

Abstract

The invention discloses a pebble coal waste heat utilization system and method of a coal-fired unit coupled heat insulation furnace, and belongs to the technical field of energy utilization and energy conservation. Comprising a heat insulation furnace body, a pebble coal crushing unit, an air supply unit, a diesel oil ignition unit, an ash blowing unit, a high-temperature flue gas mixing unit and an ash slag unit, wherein the pebble coal crushing unit, the air supply unit and the diesel oil ignition unit are connected with the feeding end of the heat insulation furnace body; the ash blowing unit and the high-temperature flue gas mixing unit are connected with the flue gas outlet end of the heat insulation furnace body; and the compressed air unit is respectively connected with the heat insulation furnace body, the soot blowing unit and the air supply unit. Based on the stable combustion characteristic of an adiabatic furnace, pebble coal is crushed and then combusted through the adiabatic furnace, after combustion, the pebble coal is mixed with a hot secondary air system of a pulverized coal furnace through hot flue gas, meanwhile, an effective pebble coal treatment mode and hot secondary air temperature rising are provided, solid waste treatment of a unit is achieved, and the flexibility of the unit is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of energy utilization and energy saving, and in particular relates to a pebble coal waste heat utilization system and method of a coal-fired unit coupled with an adiabatic furnace. Background Art

[0002] Low calorific value solid waste, also known as inferior fuel, can be divided into two categories according to the source. One is the waste generated by social life, such as domestic garbage, sludge, etc.; the other is the waste generated by low calorific value coal and coal chemical process, such as coal gangue, coal slime, ash and slag after coal gasification, etc. Due to the relatively low calorific value of inferior fuel, it is difficult to completely burn and utilize it with general combustion technology, and the energy quality generated by combustion is relatively poor. How to use inferior fuel for resource combustion has always been an important topic in the field of combustion. Incineration technology is a technology that uses inferior fuel for high-temperature thermochemical treatment. It has the characteristics of short processing cycle, small footprint, and high combustion efficiency. At present, there are more than 1,600 large-scale waste incinerators built around the world that can generate and recycle waste heat, and can process up to 195 million tons of waste each year. Compared with domestic garbage, coal-related waste has the potential for recycling and reuse. The products of coal gangue, pebble coal and other inferior fuels after combustion are usually amorphous Al2O3 and SiO2, which can react with alkaline substances at room temperature and pressure to form hydraulic cementitious materials, while ash and sedimentation ash can also be used to produce ordinary silicate cement, mortar, refractory bricks and other construction, insulation and heat insulation materials. Pebble coal is one of the solid wastes generated in the process of coal mining. It has the characteristics of high hardness, low calorific value and high ash content. At the same time, its output is extremely high, which seriously occupies the land resources of coal production enterprises and power generation enterprises. Pebble coal is prone to spontaneous combustion and pollution of the environment after being piled for a long time, which brings safety risks to surrounding equipment. The cost of external transportation and disposal is high, generally up to 100 yuan / t or more. In order to deal with this inferior fuel, the commonly used method is to mix it with pulverized coal boilers. Although it can achieve better treatment effects, the extremely high hardness of pebble coal increases the energy consumption of wear machines and causes serious wear, which greatly reduces the economic efficiency of boiler unit operation. After more than a hundred years of development and optimization, fluidized bed incinerator technology has become a relatively mature industrial technology with excellent fuel adaptability and operational reliability.

[0003] In recent years, there has been a large difference between the coal type used in boiler operation and the designed coal type, resulting in a large amount of pebble coal produced by the coal mill. A coal-fired power plant with a 300MW unit produces about 10,000 tons of pebble coal a year. As a solid waste, pebble coal has a low calorific value of between 1500-1951kcal / kg and a high sulfur content. t,ad ) is between 6.6% and 7.1%, and the volatile matter (V ad )12%-15%, internal water (M ad )0.6%-1%, ash content (Aad) 68%-74%, and the hardness is high, which makes it difficult to grind in conventional medium-speed mills, and the pulverized coal furnace cannot fully burn and utilize it. In order to properly place the pebble coal, it is necessary to set up a special pebble coal stacking area in the closed coal yard. The pebble coal stacking not only occupies the raw coal site and squeezes the coal storage capacity, but also spontaneously ignites due to long-term stacking, and sulfide corrosion occurs on the top of the closed coal yard, which poses serious environmental pollution and safety risks. At present, the pebble coal utilization methods commonly used in power plants are pulverized coal furnace blending and fluidized bed combustion. When pulverized coal furnace blending is used, the pebble coal has a large wear index and causes more serious wear on the coal mill. For fluidized bed combustion, a new set of fluidized bed boilers is built, the system is complex, and the cost is high. Therefore, a set of adiabatic furnace solid waste disposal technology has many mature application cases in the field of sludge disposal, and there has been no relevant research and application of pebble coal and coal-fired boiler coupling treatment technology. Combined with the characteristics of the adiabatic furnace and the resource characteristics of pebble coal, the method of the pebble coal utilization system based on the coupling adiabatic furnace of the coal-fired unit has not been disclosed. Chinese patent document CN113713948B discloses a pebble coal recycling device and recycling method, and provides a pebble coal recycling device and recycling method, which structure includes an external transport device, a sorting device and a return device, the external transport device includes a pebble coal collection bin, the pebble coal collection bin is located below the roller mill, the mesh separation bin is connected to the mechanical separation bin, the ball mill separation module is connected to the outlet of the mechanical separation bin, the building material collection bin is connected to the outlet of the ball mill separation module, the collection pipe is connected to the ball mill separation module, a bag filter is provided above the pulverized coal bin, the pulverized coal bin pump is connected to the discharge port of the pulverized coal bin, one end of the return pipe is connected to the bottom of the pulverized coal bin pump, and the other end is connected to the coal drop pipe of the roller mill. The transport, sorting and return of pebble coal are realized, and the process difficulty of pebble coal reuse is solved. The coal energy with calorific value in pebble coal is separated to the greatest extent through the ball mill separation module, and these coal powders are added back to the coal drop pipe of the roller mill to realize on-site utilization. The recycling of pebble coal is realized on the basis of the original pebble coal disposal method, but it will cause difficulty in recycling when the pebble coal emission is high, so the pebble coal disposal of some coal-fired units is relatively limited.Chinese patent document CN114669233B proposes a device and method for mixed utilization of pebble coal and coal gasification fine slag, which relates to the technical field of solid waste resource utilization, and in particular to a device for mixed utilization of pebble coal and coal gasification fine slag, comprising a roller coal mill and a coal gasification fine slag storage tank, a pebble coal collecting bucket is arranged below the roller coal mill, a plunger pump is connected below the coal gasification fine slag storage tank, the pebble coal collecting bucket and the plunger pump are respectively connected to a vacuum stirring evaporator through pipelines, a discharge valve located below the vacuum stirring evaporator is connected to a grinding device, a condenser is connected to the top of the vacuum stirring evaporator through a pipeline, a first dust collector is connected to the outlet of the condenser, a vacuum pump is connected to the outlet of the first dust collector through a pipeline, an air outlet of the vacuum pump is communicated with the inside of the grinding device through an exhaust pipeline, the outlet of the grinding device is connected to a second dust collector through a conveying pipe, an air push sending tank is connected to the bottom of the second dust collector, and the bottom of the air push sending tank is communicated with a coal drop pipe on the upper part of the roller coal mill. However, pebble coal gasification is greatly affected by the characteristics of pebble coal, and it is more difficult to treat some pebble coals with low volatile matter.

[0004] Chinese patent document CN103599858A proposes a pebble coal sorting and recycling system, and discloses a pebble coal sorting and recycling system, including an acceleration pipeline, a pebble coal pneumatic sorting device, a cyclone separator, a dust collector, a collection bin and a fan, the outlet of the acceleration pipeline is connected to the inlet of the pebble coal pneumatic sorting device, the raw coal particle outlet of the pebble coal pneumatic sorting device is connected to the inlet of the cyclone separator, the gas outlet of the cyclone separator is connected to the inlet of the dust collector, the dust outlet of the cyclone separator is connected to the inlet of the collection bin, and the gas outlet of the dust collector is connected to the gas inlet of the fan. The pebble coal can be sorted and recycled. However, it is difficult to dispose of the flame-retardant pebble coal as solid waste, and there are still a series of problems after the pebble coal is piled up. Chinese patent document CN117053222A proposes a system and method for disposing pebble coal based on a pulverized coal boiler in a coal-fired power plant, and discloses a system and method for disposing pebble coal based on a pulverized coal boiler in a coal-fired power plant, including a pebble coal storage system, a crushing system, a boiler furnace, a crushing and screening system, a fan system and a pebble coal burner; the outlet of the pebble coal storage system is connected to the inlet of the crushing system; the high-temperature flue gas interface on the tail flue of the boiler furnace is connected to the flue gas inlet of the crushing system; the outlet of the crushing system is connected to the inlet of the crushing and screening system, and the powdered material outlet of the crushing and screening system is connected to the inlet of the fan system; the coarse particle material outlet of the crushing and screening system is connected to the reverse material inlet of the pebble coal storage system; the outlet of the fan system is connected to the inlet of the pebble coal burner, and the outlet of the pebble coal burner is connected to the boiler furnace. The system and method can dispose of and utilize the raw coal in the pebble coal as a resource, while ensuring that the impurity components in the pebble coal do not affect the boiler and the pulverizing system. Chinese patent document CN 111229439 A proposes a closed system for handling pebble coal, including: a pebble coal storage tank, a manual gate valve, a first pneumatic gate valve, a second pneumatic gate valve, a material level meter, a feeder, a primary conveyor, a main conveyor and a terminal conveyor; the manual gate valve is arranged at the entrance of the pebble coal storage tank, and is used to communicate with the pebble coal discharge outlet of the coal mill; the first pneumatic gate valve is arranged at the entrance of the pebble coal storage tank, and is used to communicate with the pebble coal discharge outlet of the coal mill; the pebble coal discharged from the pebble coal discharge outlet of the coal mill passes through the manual gate valve and the first pneumatic plug-in valve and enters the pebble coal storage tank; the second pneumatic gate valve is arranged at the outlet of the pebble coal storage tank, and is connected to the feeder; the feeder is connected to the feeding end of the primary conveyor. The closed system for handling pebble coal enables the coal mill to discharge pebble coal in a timely, safe, economical, stable and environmentally friendly manner. However, this system is difficult to treat non-flammable stone coal as solid waste, and the stone coal piles cannot be disposed of at the source.Chinese patent document CN 118287236 A proposes a positive pressure conveying coal mill stone coal grinding and recycling system, including: a positive pressure conveying device, a stone coal conveying device and a dust removal device; the positive pressure conveying device is arranged at the input end of the stone coal; the dust removal device is arranged at the output end of the stone coal conveying device; the positive pressure conveying device includes a blower, and a muffler, a pressure gauge, a pressure reducing valve, a blower base and a pipeline arranged on the blower; wherein the output end of the pipeline is connected to the stone coal conveying device; the positive pressure conveying device is used to provide positive pressure air to the stone coal conveying device through the pipeline. With the above design, the start-up of the positive pressure conveying device can be automatically controlled to ensure the effective supply of stone coal materials in the stone coal conveying device, and the dust removal device can effectively remove dust from the stone coal and recycle the stone coal dust. In addition, a large amount of dust and harmful gases contained in the stone coal can be effectively filtered to reduce pollution, which has good environmental protection benefits. However, relying on other disposal equipment cannot solve the problem of stone coal emissions from coal-fired units.

[0005] Among the various methods currently disclosed for the disposal and collection of pebble coal in coal-fired units, except for the discharge, collection and sorting of pebble coal in the unit's coal combustion volume, most methods use existing coal mills to dispose of damaged pebble coal, and are unable to directly dispose of difficult-to-grind low-volatile pebble coal. There is a lack of comprehensive pebble coal disposal methods based on the characteristics of pebble coal in the existing disclosed patents. It is urgent to find a pebble coal waste heat utilization system and method for a coal-fired unit coupled with an adiabatic furnace to solve the storage problem of pebble coal in coal yards and improve the flexibility of coal-fired units. Summary of the invention

[0006] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a pebble coal waste heat utilization system and method for a coal-fired unit coupled with an insulated furnace, so as to solve the technical problem of how to effectively dispose of pebble coal and improve its waste heat utilization rate, while enhancing the flexibility and solid waste treatment capacity of the coal-fired unit.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions: The present invention discloses a pebble coal waste heat utilization system of a coal-fired unit coupled with an insulated furnace, comprising: an insulated furnace body, a pebble coal crushing unit, an air supply unit and a diesel ignition unit connected to a feeding end of the insulated furnace body, a soot blowing unit and a high-temperature flue gas mixing unit connected to a flue gas outlet end of the insulated furnace body, an ash unit connected to a slag discharge port of the insulated furnace body, and a compressed air unit respectively connected to the insulated furnace body, the soot blowing unit and the air supply unit.

[0008] Preferably, the pebble coal crushing unit comprises: a pebble coal material yard, a crushed pebble coal temporary storage yard, a feeding screw conveyor and a bucket elevator which are connected in sequence.

[0009] Preferably, the air supply unit comprises: primary air for providing the air required for the initial combustion of the adiabatic furnace and secondary air delivered by the high-temperature flue gas mixing unit.

[0010] Preferably, the diesel ignition unit comprises: a light diesel oil storage tank, a delivery station, and an ignition burner connected in sequence.

[0011] Preferably, the sootblowing unit comprises: a cyclone separator connected to the flue gas outlet end of the insulated furnace body, and a secondary air bellows connected to the outlet end of the cyclone separator via a high-temperature mixing flue.

[0012] Further preferably, the high-temperature flue gas mixing unit comprises: an air mixing section connected between the cyclone separator and the secondary air box.

[0013] Preferably, the ash unit comprises: a furnace front bunker connected to the stone coal crushing unit, and a coal feeder connected to the furnace front bunker.

[0014] Further preferably, the ash slag unit also includes: a multi-tube liquid cylinder slag cooler, an ash slag bin and a dry slag tank truck which are sequentially connected to the slag outlet end of the insulation furnace body.

[0015] Preferably, the compressed air unit comprises: a sealed fan respectively connected to the insulated furnace body, the soot blowing unit and the air supply unit.

[0016] The present invention also discloses a method for using the above-mentioned pebble coal waste heat utilization system of the coal-fired unit coupled with an adiabatic furnace, comprising the following steps: 1) Ensure that the insulated furnace body, stone coal crushing unit, air supply unit, diesel ignition unit, soot blowing unit, high-temperature flue gas mixing unit, ash unit and compressed air unit are in good working condition; start the compressed air unit to provide the necessary compressed air for the entire system; 2) The pebble coal produced by the coal-fired unit is sent to the pebble coal crushing unit for crushing, and the crushed pebble coal is sent to the feed end of the adiabatic furnace body through appropriate conveying equipment; 3) Adjust the air volume and wind speed of the air supply unit to provide the necessary combustion air for the adiabatic furnace body; use the diesel ignition unit to ignite the stone coal in the adiabatic furnace body; 4) When high-temperature flue gas is generated in the adiabatic furnace body, the adiabatic furnace body starts the soot blowing unit to perform soot blowing operations inside the adiabatic furnace body; the high-temperature flue gas enters the high-temperature flue gas mixing unit through the flue gas outlet end, and the ash generated after the combustion is completed enters the ash unit through the slag discharge port of the adiabatic furnace body for treatment.

[0017] Compared with the prior art, the present invention has the following beneficial effects: The present invention discloses a pebble coal waste heat utilization system of a coal-fired unit coupled with an adiabatic furnace. The adiabatic furnace is used to stably burn the pebble coal, effectively solving the problems of high sulfur content, high hardness, low calorific value and difficulty in handling of the pebble coal, realizing efficient and environmentally friendly disposal of the pebble coal, and the maximum annual disposal amount of the pebble coal can reach more than 30,000 tons. The high-temperature flue gas generated by the adiabatic furnace is mixed with the hot secondary air of the coal-fired unit, which significantly increases the temperature of the hot secondary air (not less than 5°C), helps the ignition, burnout and low-load stable combustion of coal powder, thereby improving the combustion efficiency and stability of the coal-fired unit. By increasing the temperature of the hot secondary air, the comprehensive coal consumption is reduced by about 1.38g / kwh. For Unit 2, the annual coal saving can reach 2,310 tons, and the two units can save about 2.65 million yuan in costs each year, achieving significant economic benefits. The introduction of the adiabatic furnace not only solves the problem of pebble coal disposal, but also enhances the adaptability and flexibility of the coal-fired unit to load changes by increasing the temperature of the hot secondary air, etc., which helps to improve the overall operating performance of the unit. The efficient disposal of pebble coal reduces solid waste emissions, and the combustion process of the adiabatic furnace also meets environmental protection requirements, reduces pollutant emissions, and has positive significance for environmental protection. According to the fuel characteristics of pebble coal and the smoke and wind characteristics of coal-fired boilers, the present invention develops a pebble coal combustion system for coal-fired units coupled with an adiabatic furnace, which provides an effective solution for the emission and disposal of pebble coal in coal-fired units, and has a good demonstration and guiding significance for similar situations.

[0018] The present invention also discloses a method for using the pebble coal waste heat utilization system of the above-mentioned coal-fired unit coupled with an adiabatic furnace. By crushing and burning the pebble coal that may have been discarded and utilizing the waste heat generated by it, the comprehensive utilization rate of energy is significantly improved. This utilization method not only reduces the waste of energy, but also increases the overall output of the coal-fired unit. The utilization of pebble coal waste heat reduces the dependence of the coal-fired unit on raw coal, thereby reducing the emission of harmful gases such as sulfur dioxide and nitrogen oxides generated during the coal combustion process, which helps to improve air quality and protect the environment. The implementation of this system can reduce the fuel cost of the coal-fired unit and reduce the additional costs incurred by processing discarded pebble coal. Through the utilization of waste heat, heat sources can also be provided for other production processes, further increasing economic benefits. The coupling technology of the coal-fired unit and the adiabatic furnace is combined to achieve efficient utilization of pebble coal waste heat. It not only provides new ideas for improving the energy efficiency of coal-fired units, but also provides a reference example for waste heat utilization in other industries. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the technical process diagram of the pebble coal bubbling fluidized bed incinerator; Figure 2 It is a process flow chart of the pebble coal waste heat utilization system of the coal-fired unit coupled with the adiabatic furnace of the present invention; Figure 3It is a schematic structural diagram of the low calorific value self-sustaining incineration fluidized bed incinerator of the present invention.

[0020] Among them: 1-stone coal material yard; 2-crushed stone coal temporary storage yard; 3-feeding screw conveyor; 4-bucket elevator; 5-furnace front silo; 6-coal feeder; 7-insulated furnace body; 8-primary air; 9-secondary air; 10-ignition burner; 11-sealed fan; 12-circulating ash discharge pipeline; 13-transportation station; 14-light diesel storage tank; 15-multi-tube liquid cylinder slag cooler; 16-ash slag bin; 17-dry slag tanker; 18-cyclone separator; 19-secondary air bellows; 20-mixing air section; 21-secondary air duct access port; 22-gate valve. DETAILED DESCRIPTION

[0021] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0022] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0023] The present invention is further described in detail below in conjunction with the accompanying drawings: The present invention proposes a pebble coal waste heat utilization system for a coal-fired unit coupled with an adiabatic furnace. Relying on the stable combustion characteristics of the adiabatic furnace, the pebble coal is crushed and disposed of and then burned in the adiabatic furnace. After combustion, the hot flue gas is mixed with the hot secondary air system of the pulverized coal furnace. At the same time, an effective pebble coal disposal method and hot secondary air temperature increase are provided to achieve solid waste disposal of the unit and improve the flexibility of the unit. In response to the problem of pebble coal emission and disposal, a low calorific value material adiabatic self-sustaining incineration system is proposed. The high-temperature flue gas generated is coupled with the hot secondary air system to increase the temperature of the secondary air sent to the boiler, thereby improving the boiler efficiency. At the same time, the storage problem of pebble coal in the coal yard is solved, the flexibility of the coal-fired unit is improved, and a strong guarantee is provided for the unit to exert its solid waste disposal capacity. The present invention adopts a circulating fluidized bed technology for self-sustaining combustion of pebble coal without combustion support, which has high combustion efficiency, strong processing capacity, and good operating economy, and is expected to achieve efficient resource energy utilization of pebble coal.

[0024] See also Figure 1 This is the technical process diagram of the pebble coal bubbling fluidized bed incinerator; as can be seen from the figure, the pebble coal is first fed into the furnace silo through the bucket elevator, and then enters the furnace screw conveyor through the gate valve 1 and gate valve 2, and the CaCO3 in the CaCO3 silo enters the furnace screw conveyor through the CaCO3 feeding screw conveyor. In this process, CaCO3 and pebble coal are evenly fed into the bubbling fluidized bed. The bubbling fluidized bed is evenly fed with air through the air distribution plate at the bottom of the furnace, so that the pebble coal particles form a fluidized state under the action of air, ensuring the uniform distribution of the fuel in the furnace. This fluidized state not only improves the combustion efficiency, but also helps to reduce the emission of solid waste. During the combustion process, the primary combustion air and the secondary combustion air are respectively fed into the furnace through different paths to provide sufficient oxygen for combustion. The technical process of the pebble coal bubbling fluidized bed incinerator is based on an adiabatic furnace, and the incineration system adopts an adiabatic incinerator technical process combining a bubbling fluidized bed with a cyclone separator. The stone coal is stored in the storage silo through the transportation equipment. The storage tank system sends the material to the screw conveyor and then enters the bubbling fluidized bed for incineration to achieve continuous feeding. At the beginning, the diesel is ignited to heat up and assist combustion. Since the calorific value of the residue is very high, the combustion basically does not require auxiliary fuel, and the temperature can reach about 850~900℃. The CaCO3 mixed material is added to the incinerator for in-furnace desulfurization. The flue gas after combustion enters the cyclone dust collector after a section of zoom flue. The high-temperature flue gas after the cyclone dust collector directly enters the wind box and mixes with the hot secondary air of the pulverized coal boiler. The design of the insulated furnace effectively ensures the self-sustaining incineration of low-calorific value materials, and the calorific value of the material itself can reach a minimum of 1200kcal / kg; the furnace outlet is equipped with a separator to avoid the influence of a large amount of fly ash on the heat exchange of the tail heating surface, reduce the pressure of tail cleaning, reduce maintenance, and ensure long-term stable operation of the equipment. A slag cooling system is set at the bottom of the furnace, and the high-temperature slag is cooled to about 100℃ by a roller slag cooler.

[0025] See also Figure 2 This is a process flow chart of the pebble coal waste heat utilization system of the coal-fired unit coupled with the adiabatic furnace of the present invention; the system mainly includes: an adiabatic furnace body 7, a pebble coal crushing unit, a soot blowing unit, an air supply unit, an ash unit, a compressed air unit, a diesel ignition unit and a high-temperature flue gas mixing unit, etc.

[0026] The pebble coal crushing unit includes: a pebble coal yard 1 for storing raw pebble coal, a crushed pebble coal temporary storage yard 2 for temporarily storing crushed pebble coal, a bucket elevator 4 for lifting pebble coal to a furnace silo 5, and a feeding screw conveyor 3 for conveying crushed pebble coal to the bucket elevator 4.

[0027] The air supply unit includes: primary air 8 for providing the air required for the initial combustion of the adiabatic furnace, and secondary air 9 for further supporting the combustion and being managed and distributed through the secondary air box 19.

[0028] The ash unit includes: a furnace front silo 5 for storing pebble coal to be fed into the adiabatic furnace, a coal feeder 6 for feeding the pebble coal into the adiabatic furnace, a multi-tube liquid cylinder slag cooler 15 for cooling the slag, an ash silo 16 for storing the cooled ash, and a dry slag tank truck 17 for loading the ash for transportation.

[0029] The soot blowing unit includes: a cyclone separator 18 for separating particulate matter in the flue gas generated by combustion, and a secondary air box 19 connected to the cyclone separator 18 .

[0030] The compressed air unit comprises: a sealing fan 11 for providing sealing air required by the system.

[0031] The diesel ignition unit includes: a light diesel oil storage tank 14 for storing light diesel oil for ignition, a delivery station 13 for delivering light diesel oil, and an ignition burner 10 for ignition and auxiliary combustion connected to the insulated furnace body 7. The insulated furnace body 7 carries out combustion of stone coal and heat utilization.

[0032] The high-temperature flue gas mixing includes: an air mixing section 20 for mixing the high-temperature flue gas and air.

[0033] The pebble coal is crushed and temporarily stored in the pebble coal temporary storage yard 2 from the pebble coal material yard 1, and then sent to the furnace silo 5 through the feeding screw conveyor 3 and the bucket elevator 4. The pebble coal in the furnace silo 5 is sent to the insulated furnace body 7 by the coal feeder 6 for combustion. During the combustion process, the primary air 8 and the secondary air 9 provide the necessary air support, and the ignition burner 10 is responsible for ignition. The ash produced by the combustion is cooled by the multi-tube liquid cylinder slag cooler 15, stored in the ash silo 16, and finally transported away by the dry slag tanker 17. The cyclone separator 18 separates the particulate matter in the flue gas, and the mixing section 20 mixes the high-temperature flue gas and air. The secondary air box 19 manages and distributes the secondary air 9. The sealed fan 11 provides the system sealing air, and the light diesel tank 14 stores the ignition diesel. The circulating ash discharge pipeline 12 and the conveying station 13 are responsible for processing and managing the transportation of circulating ash and materials.

[0034] ① Pebble coal crushing unit: In order to ensure that the pebble coal can maintain self-stable combustion, the pebble coal needs to be broken into samples with a maximum particle size of no more than 3mm, and then it can maintain self-stable combustion after passing through the under-bed ignition system. The pebble coal crushing unit adopts coal gangue hammer crusher (two-stage screenless crusher), and the processing capacity of a single crushing system is about 100t / h.

[0035] ② Sootblowing unit: shock wave cleaning is used to remove ash deposits on the hot surface, thereby ensuring normal, stable and efficient operation of the boiler.

[0036] ③ Air supply unit: The existing hot primary air 8 margin is limited, and both the cold primary air 8 and the sealed air need to be equipped with booster fans to meet the use requirements. Therefore, this system considers adding a blower for primary and secondary air, and variable frequency regulation. In order to meet the needs of abnormal shutdown of the fan, the sealed air is introduced into the air supply unit as the exhaust needs during abnormal shutdown. The air volume is set according to the requirements of the system and the variable frequency speed control is adopted, and the induced draft fan blades are selected from heat-resistant, anti-corrosion and anti-wear materials.

[0037] ④ Ash and slag unit: The residue mainly comes from the incinerator slag. The drum slag cooler is used, and the slag cooler needs to be equipped with a cooling water circulation unit connected to the boiler 0m closed water system. The slag produced at the bottom of the adiabatic furnace passes through the multi-tube liquid cylinder slag cooler 15 and is sent to the pneumatic conveying unit through the silo pump, and finally stored in the ash and slag silo 16. The slag of the incinerator is discharged by the ash and slag through the multi-tube liquid cylinder slag cooler 15, and then transported to the temporary storage site in the factory by manual or dry slag tanker 17. After being mixed with ash by the owner, it can be used as a bed material for resource utilization. The design of the tube liquid cylinder slag cooler 15 should take into account the emergency slag discharge needs under accident conditions. The tube liquid cylinder slag cooler 15 is designed according to 1 use and 1 standby, and is designed according to the maximum slag discharge volume of 15t / h.

[0038] ⑤ Compressed air unit: The compressed air unit provides air source for the system process and consists of an air compressor, a dryer, a filter and an air storage tank.

[0039] ⑥ The thermal insulation system combined with stone coal only needs to include the induced draft fan unit and the ash unit, without the need for a waste heat boiler, and an insulating air distribution plate is used at the bottom of the thermal insulation furnace.

[0040] ⑦ Diesel ignition unit: The auxiliary fuel in this unit is diesel, which is ignited and burned by the ignition burner 10 before being sent into the insulated furnace body 7. The ignition burner 10 has an automatic adjustment function, which can automatically adjust the size of the flame. The combustion-supporting system includes a diesel gun, an automatic ignition device, a flame detection device, a fuel and atomizing medium control valve group, an operation control cabinet, etc. The ignition burner 10 requires a compact structure, stable combustion, a large adjustment ratio, low noise, good flame spread, complete combustion, and easy combustion control. The ignition burner 10 uses an electric ignition method: Under the premise that all safety conditions are met, the valve is opened, and the ignition transformer generates a high voltage and ignites it. The flame detector installed inside the ignition burner 10 will detect the flame and feed back to the control system to confirm whether the ignition burner 10 will continue to operate in the future.

[0041] ⑧ High-temperature flue gas mixing unit: The high-temperature flue gas at the outlet of the adiabatic furnace body 7 is led back to the gap between the hot secondary air duct of unit 2 and the economizer ash hopper, and then divided into two paths, and sent to the hot secondary air ducts on the left and right sides through the secondary air duct inlet 21. The flow rate of the flue before mixing is designed to be 10m / s, and 350mm heat-resistant materials are laid. The design flow rate of the flue in the mixing section 20 is designed to be 5m / s, and the material of the flue after mixing is Q355B.

[0042] ⑨System installation location: The low calorific value material incineration system is arranged in the open space at the induced draft fan on the north side of the existing No. 2 furnace, with a length×width×height of approximately 15m×8m×15m respectively.

[0043] The method for using the pebble coal waste heat utilization system of the coal-fired unit coupled with the adiabatic furnace disclosed in the present invention comprises: 1) The pebble coal is finely crushed by the pebble coal crushing unit; 2) The crushed stone coal is sent to the adiabatic furnace body 7 for combustion; in this process, the air supply unit uses an additional air blower to realize the common use of primary air 8 and secondary air 9, and adjusts the air volume through frequency conversion according to actual working conditions to ensure sufficient and stable oxygen supply required for the combustion process; the soot blowing unit adopts shock wave soot cleaning technology to remove the soot accumulated on the hot surface; 3) The ash produced by combustion is processed by the ash unit; the ash is cooled by the multi-tube liquid cylinder cooler 15, and the cooled ash is sent to the pneumatic conveying unit through the silo pump and finally stored in the ash silo 16, thus realizing the effective treatment and resource utilization of the ash; 4) The compressed air unit provides a stable air source for the entire system; it consists of an air compressor, a dryer, a filter and an air storage tank, ensuring the normal operation and stable operation of each component; 5) The diesel ignition unit is used as an auxiliary fuel, which is ignited and burned by the ignition burner 10 before being sent into the insulated furnace body 7; the ignition burner 10 has an automatic adjustment function, which adjusts the flame size according to needs, ensuring the stable combustion of the stone coal and the normal operation of the system; 6) The high-temperature flue gas mixing unit leads the high-temperature flue gas from the outlet of the adiabatic furnace to the gap between the hot secondary air duct of the unit and the economizer ash hopper, and divides it into two paths and sends it to the hot secondary air ducts on the left and right sides; it not only realizes the effective utilization of high-temperature flue gas, but also improves the thermal efficiency of the system.

[0044] The method for using the pebble coal waste heat utilization system of the coal-fired unit coupled with the adiabatic furnace disclosed in the present invention involves the coordinated operation of multiple systems. The pebble coal crushing unit provides a stable fuel supply, the air supply unit and the soot blowing unit ensure the stability and safety of the combustion process, the ash slag unit realizes the effective treatment and resource utilization of ash slag, the compressed air unit provides a stable air source support, the diesel ignition unit ensures the stability and controllability of combustion, and the high-temperature flue gas mixing unit realizes the effective utilization of high-temperature flue gas. The whole system can realize efficient and environmentally friendly pebble coal waste heat utilization.

[0045] Example Taking the discharge and disposal of pebble coal of a 2×320MW unit in a certain plant as an example, the boiler pulverizing system adopts a cold primary air positive pressure direct blowing pulverizing system, and each unit is equipped with five HP863 medium-speed coal mills designed and produced by Shanghai Heavy Machinery Factory. The coal mill is arranged in front of the furnace, with 4 mills in operation and 1 mill in standby (BMCR working condition), and a centrifugal separator is used. Since the grindability coefficient HGI of the designed coal type is 77 (the HGI of the verified coal quality is 62), there is a large difference between the operating coal type and the designed coal type, resulting in a large amount of pebble coal produced by the coal mill, and the amount of pebble coal produced per year is about 10,000 tons. The produced pebble coal has high sulfur content, high hardness, low calorific value, and is not easy to handle. At present, due to the weak development of the construction industry and the decline in demand for raw materials, the sales of pebble coal are not smooth. In order to properly place the pebble coal, the company has set up a special pebble coal stacking area in the raw coal bin. At present, there are about 10,000 tons of pebble coal, covering an area of ​​about 4,000 square meters.

[0046] Table 1 Statistical results of stone coal quality parameters from 2022 to April 2024

[0047] In 2023-2024, the calorific value of pebble coal will be between 1500-1951 kcal / kg, and the sulfur content on an air-dried basis will be between 6.6% and 7.1%. Based on the recent coal quality, which is mainly a mixture of bituminous coal and anthracite, with an anthracite content of about 20%-30%, it is estimated that the proportion of pebble coal with a calorific value of 1500-1951 kcal / kg will be about 80% in the next three years. The parameters of this transformation of pebble coal are designed according to 1700 kcal / kg and the sulfur content of pebble coal on an air-dried basis is about 6.8%.

[0048] The design capacity of the adiabatic furnace should take into account factors such as the amount of pebble coal produced, its impact on the oxygen content of the secondary air, the impact of the secondary air temperature increase, and the impact of flue gas mixing on the combustion effect of the pulverized coal furnace and the secondary air.

[0049] 1) Pebble coal production factor: According to the current pebble coal production of Xuzhou Huaxin Company, the monthly pebble coal production of the whole plant is about 900t. Considering that the operating hours of Unit 2 are about 6,500 hours, the adiabatic furnace is considered to be no less than 95% of the annual operating hours of Unit 2. The designed pebble coal output should not be less than 1.75t / h.

[0050] 2) The influence of the ratio of stone coal flue gas volume to hot secondary air volume Referring to the relevant analysis results of the hot secondary air on the combustion effect of the four-corner tangential boiler, when the proportion of the pebble coal flue gas volume to the hot secondary air volume is controlled within 5%, the impact on the secondary air can be ignored. In the subsequent design process, the flue layout should be combined to carry out numerical simulation between the adiabatic furnace outlet and the pulverized coal furnace, and analyze and evaluate the impact of pebble coal mixing on the hot secondary air temperature and boiler combustion.

[0051] Table 2 Thermal calculation table of adiabatic furnace

[0052] 3) Influence of stone coal flue gas volume and hot secondary air oxygen content The oxygen content of stone coal flue gas is about 8%. After stone coal flue gas is mixed with hot secondary air, the hot secondary air temperature can be increased, and the oxygen content of flue gas will decrease. Referring to the flue gas recirculation transformation case, if the oxygen content of flue gas decreases within about 0.5% after mixing, the impact on boiler combustion is small.

[0053] Combining the above considerations, taking into account the impact of the flue gas generated by pebble coal on the secondary air of the pulverized coal furnace and the design scale of the adiabatic furnace, the recommended design capacity of the pebble coal adiabatic furnace is 5t / h.

[0054] The technical objectives of the waste heat treatment of pebble coal in coal-fired units coupled with adiabatic furnaces are as follows: 1) The maximum annual disposal capacity of pebble coal shall not be less than 30,000t / h (the average calorific value of pebble coal is 1,700kcal / kg and the air-dry basis sulfur content is 6.6%).

[0055] 2) Under the rated load of Unit 2, the adiabatic furnace operates at the designed 5t / h, and the hot secondary air temperature is raised by no less than 5℃.

[0056] 3) The availability rate of the insulation furnace shall not be less than 90%.

[0057] The adiabatic furnace processing system of pebble coal mainly includes the adiabatic furnace body, the air supply unit, the pebble coal storage and breaking system (gangue hammer breaking device (two-stage screenless crusher) (satisfying the particle size of the pebble coal after breaking <8mm)), the feeding system, the slag discharge system, the mixing flue (including the conveying flue) and the electrical control system.

[0058] Table 3 Coal quality design parameters

[0059] See also Figure 3 It is a structural schematic diagram of the low calorific value self-sustaining incineration fluidized bed incinerator of the present invention; it can be seen from the figure that the furnace front silo 5 is connected to the insulated furnace body 7 through the gate valve 22, realizing the controllable input of materials. The cyclone separator 18 is directly connected to the bottom of the insulated furnace body 7 to ensure that the flue gas generated by the incineration can smoothly enter the separation stage. The secondary air duct access port 21 is directly connected to the insulated furnace body 7 to provide the necessary supplementary air for the incineration process. The furnace front silo 5 is used as the starting part of the incinerator to store and supply the low calorific value materials to be processed. It ensures that the materials can enter the incineration system stably and continuously. The insulated furnace body 7 is the core component of the incinerator, where the materials are efficiently incinerated. The insulation design effectively maintains the high temperature in the furnace, improves the thermal efficiency, and ensures the stability and efficiency of the incineration process. The cyclone separator 18 is connected to the bottom of the insulated furnace body 7, which is responsible for separating the solid particles in the flue gas generated during the incineration process. This step is crucial to prevent particulate matter from being directly discharged into the atmosphere, and also helps to improve the efficiency of subsequent flue gas treatment. The secondary air duct access port 21 is connected to the insulated furnace body 7 for introducing secondary air to supplement air. The addition of secondary air helps to achieve more complete combustion, improve combustion efficiency, and reduce unburned materials. The gate valve 22 is located between the furnace front silo and the insulated furnace body as a switch for material flow. The gate valve can accurately control the entry timing and flow rate of materials to ensure the flexibility and controllability of the incineration process. The low calorific value material incineration system is arranged in the open space at the induced draft fan on the north side of the existing No. 2 furnace, with a length × width × height of approximately 15m*8m*15m respectively. The high-temperature flue gas at the outlet of the insulated boiler is led back to the gap between the hot secondary air duct of Unit 2 and the economizer ash hopper, and then divided into two routes and sent to the hot secondary air ducts on the left and right sides. The flow rate of the flue before mixing is designed to be 10m / s, and 350mm heat-resistant materials are laid. The design flow rate of the flue in the mixing section is designed to be 5m / s, and the material of the flue after mixing is Q355B.

[0060] After the adiabatic furnace transformation was implemented, taking the hot secondary air temperature increase of a certain unit as an example, the high-temperature flue gas from the adiabatic furnace can be connected to the hot secondary air efficiency improvement transformation. The secondary air temperature is expected to increase by 5~10℃. According to the comprehensive estimation of the effects of hot secondary air temperature increase on coal powder ignition, burnout and low-load stable combustion, the comprehensive coal consumption decreased by about 0.80g / kwh, the benefit of reducing the cold source loss on the turbine side was 0.58g / kW.h, the comprehensive coal consumption decreased by about 1.38g / kwh, the annual coal saving of Unit 2 was 2310t, and the two units could save about 2.65 million yuan per year.

[0061] According to the fuel characteristics of pebble coal and the smoke and wind characteristics of coal-fired boilers, this method develops a pebble coal combustion system for coal-fired units coupled with adiabatic furnaces. The adiabatic furnace maintains stable combustion by itself, generates high-temperature flue gas that mixes with the coal-fired units, increases the hot secondary air temperature, and improves the flexibility of the coal-fired units while achieving pebble coal solid waste disposal. A calculation method for an effective and reliable direct method for pebble coal disposal is proposed, which has a good demonstration and guiding significance for the emission and disposal of pebble coal in coal-fired units.

[0062] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A pebble coal waste heat utilization system of a coal-fired unit coupled with an adiabatic furnace, characterized in that: include: an insulated furnace body (7), a stone coal crushing unit, an air supply unit and a diesel ignition unit connected to a feed end of the insulated furnace body (7), a soot blowing unit and a high-temperature flue gas mixing unit connected to a flue gas outlet end of the insulated furnace body (7), an ash unit connected to a slag outlet of the insulated furnace body (7), and a compressed air unit respectively connected to the insulated furnace body (7), the soot blowing unit and the air supply unit.

2. The pebble coal waste heat utilization system of a coal-fired unit coupled with an adiabatic furnace according to claim 1 is characterized in that: The pebble coal crushing unit comprises: a pebble coal material yard (1), a crushed pebble coal temporary storage yard (2), a feeding screw conveyor (3) and a bucket elevator (4) which are connected in sequence.

3. The pebble coal waste heat utilization system of a coal-fired unit coupled with an adiabatic furnace according to claim 1, characterized in that: The air supply unit comprises: primary air (8) for providing the adiabatic furnace with air required for primary combustion, and secondary air (9) delivered by a high-temperature flue gas mixing unit.

4. The pebble coal waste heat utilization system of a coal-fired unit coupled with an adiabatic furnace according to claim 1, characterized in that: The diesel ignition unit comprises: a light diesel storage tank (14), a delivery station (13), and an ignition burner (10) which are connected in sequence.

5. The pebble coal waste heat utilization system of a coal-fired unit coupled with an adiabatic furnace according to claim 1, characterized in that: The soot blowing unit comprises: a cyclone separator (18) connected to the smoke outlet end of the insulated furnace body (7), and a secondary air blower box (19) connected to the outlet end of the cyclone separator (18) via a high-temperature mixing flue.

6. The pebble coal waste heat utilization system of a coal-fired unit coupled with an adiabatic furnace according to claim 5, characterized in that: The high-temperature flue gas mixing unit comprises: an air mixing section (20) connected between a cyclone separator (18) and a secondary air box (19).

7. The stone coal waste heat utilization system of a coal-fired unit coupled with an adiabatic furnace according to claim 1, characterized in that: The ash unit comprises: a furnace front silo (5) connected to the stone coal crushing unit, and a coal feeder (6) connected to the furnace front silo (5).

8. The pebble coal waste heat utilization system of a coal-fired unit coupled with an adiabatic furnace according to claim 7, characterized in that: The ash slag unit further comprises: a multi-tube liquid cylinder slag cooler (15), an ash slag bin (16) and a dry slag tanker (17) which are sequentially connected to the slag outlet end of the heat-insulating furnace body (7).

9. The pebble coal waste heat utilization system of a coal-fired unit coupled with an adiabatic furnace according to claim 1, characterized in that: The compressed air unit comprises: a sealed fan (11) connected to the insulated furnace body (7), the soot blowing unit and the air supply unit respectively.

10. The method for using the pebble coal waste heat utilization system of a coal-fired unit coupled with an adiabatic furnace according to any one of claims 1 to 9, characterized in that: The following steps are involved: 1) Ensure that the insulated furnace body (7), the stone coal crushing unit, the air supply unit, the diesel ignition unit, the soot blowing unit, the high-temperature flue gas mixing unit, the ash unit and the compressed air unit are all in good working condition; start the compressed air unit to provide the necessary compressed air for the entire system; 2) The pebble coal generated by the coal-fired unit is sent to the pebble coal crushing unit for crushing, and the crushed pebble coal is sent to the feed end of the adiabatic furnace body (7) through appropriate conveying equipment; 3) adjusting the air volume and wind speed of the air supply unit to provide necessary combustion air for the adiabatic furnace body (7); using the diesel ignition unit to ignite the stone coal in the adiabatic furnace body (7); 4) When high-temperature flue gas is generated in the insulated furnace body (7), the insulated furnace body (7) starts the soot blowing unit to perform a soot blowing operation in the insulated furnace body (7); the high-temperature flue gas enters the high-temperature flue gas mixing unit through the flue gas outlet end, and the ash generated after the combustion is completed enters the ash unit through the slag discharge port of the insulated furnace body (7) for treatment.

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