A method and device for rapid combustion and decarbonization of coal gangue

Abstract

The present invention relates to the resource recovery and disposal of bulk industrial solid waste (gangue). It provides a method and apparatus for rapid combustion and decarbonization of gangue, aiming to address deflagration problems caused by the rapid release of volatile matter during gangue combustion, as well as poor decarbonization due to incomplete combustion of fixed carbon in the gangue. The main approach involves preparing the raw materials into pellets, drying and preheating them in a belt dryer, and then subjecting them to a pyrolysis unit for low-temperature dry distillation to separate some of the volatile gases and produce pyrolyzed gangue particles. These pellets then pass through an intermediate hopper and enter a tunnel kiln in a belt sintering machine for self-calcination. Following this, they undergo a decarbonization and combustion treatment to produce decarbonized and burned gangue particles, known as water-retaining ceramsite. To produce high-strength ceramsite or gravel, the decarbonized and burned gangue particles undergo deep combustion and decarbonization in a rotary kiln, followed by high-temperature surface vitrification.

Description

Technical Field

[0001] The present invention relates to the field of resource disposal of bulk industrial solid waste (coal gangue), and provides a method and device for rapid combustion and decarbonization of coal gangue. Background Art

[0002] Coal gangue is solid waste discharged during coal mining and washing. It is characterized by low calorific value (less than 1500KCal / Kg), high ash content (greater than 70%), low carbon content (about 10%), and low volatile matter (about 10%). It cannot be used as boiler fuel. Gangue accounts for an average of approximately 20% of coal production. If stored in open-air piles or improperly landfilled, it can spontaneously combust, releasing toxic gases that can pollute local air for decades or even centuries, making it difficult to extinguish. Gangue emitted from coal mines and coal washing plants has a calorific value of approximately 500 to 1500 kcal / kg. This low calorific value makes it unsuitable for use as fuel in gangue power plants, nor as a building material for graded roads or concrete. Only a small amount can be used as a raw material for sintered bricks. Environmentally friendly landfilling remains the primary disposal method in these areas, but closed gangue landfills require long-term internal temperature monitoring and heat dissipation measures, resulting in high maintenance costs. Some coal mines resort to underground backfilling (or grouting), which is very costly, and the amount of gangue that can be backfilled (or grouted) underground accounts for a small proportion of the total gangue production.

[0003] If gangue (500-1500 kcal / kg) is used directly as a raw material for sintered bricks, expanded clay, and gravel in conventional kilns such as tunnel kilns, rotary kilns, and sintering machines, its high calorific value (optimal calorific value for internal combustion is 300-400 kcal / kg) and its volatile matter content exceeding 5% in most regions make it difficult to control the internal temperature of the kiln. This can lead to problems such as production lines failing to reach full capacity, unstable product quality (low pass rates), and lumps and kiln blockage. This excessive calorific value of raw materials (500-1500 kcal / kg) has long been a challenge for kiln operators. Currently, a more practical and feasible approach is to add clay, shale, or fly ash to the gangue to reduce its calorific value to 300-400 kcal / kg before combustion. This, in turn, reduces the amount of gangue that can be disposed of exponentially, increasing the unit cost of handling and incineration of gangue in kilns. Although there are mature technologies for super internal combustion brick-making tunnel kilns that can achieve stable temperature control when burning 500-1000Kcal / Kg of bricks, the market demand for sintered bricks has also decreased significantly with the shrinking construction market. In the main coal-producing areas, the amount of coal gangue that can be disposed of by super internal combustion brick-making tunnel kilns is relatively small.

[0004] Under the super internal combustion conditions where the high calorific value of the raw materials entering the kiln is greater than 500Kcal / Kg, when the temperature of the coal gangue particles in conventional kilns such as tunnel kilns, rotary kilns, and sintering machines is raised to about 500℃, the volatile gases inside the coal gangue particles are rapidly separated and exploded, causing the temperature in the kiln to rise rapidly from 500℃ to above 1000℃. Before the fixed carbon inside the coal gangue particles has time to burn, a liquid phase appears on the surface of the coal gangue particles, isolating oxygen from contact with the fixed carbon inside, resulting in the fixed carbon inside the coal gangue particles not being fully burned and the coal gangue decarbonization effect being poor. Specifically, there are a large number of "black hearts" inside the coal gangue particles. Such coal gangue particles with a large number of "black hearts" will still spontaneously combust when stored and cannot be directly used as building materials. This is the main reason why the existing rotary kiln technology has a low disposal capacity when disposing of super internal combustion coal gangue.

[0005] For gangue with a volatile matter content exceeding 5% and a calorific value exceeding 500 KCal / kg, the gangue easily agglomerates during the static combustion phase after ignition on the grate, blocking gas passages. This not only prolongs the combustion time in the high-temperature zone, but also prevents sufficient decarbonization and can cause kiln blockages. This is the main reason why sintering machines cannot operate normally when handling highly combustible gangue. Existing technologies address this problem by heating the gangue to decompose the volatile gases or by extracting the high-temperature flue gas generated by the combustion of the volatile gases out of the kiln during the rapid combustion phase to prevent the burning gangue from rapidly heating up. However, this method of heating the gangue to decompose the volatile gases makes it extremely difficult to ignite the remaining gangue, requiring the use of auxiliary fuels such as natural gas to burn out the fixed carbon in the gangue. This increases the cost of gangue disposal, and as the benefits outweigh the costs, there have been no successful engineering applications to date. The method of extracting the high-temperature flue gas generated by the combustion of volatile gases out of the kiln during the rapid combustion stage of volatile gases can solve the problem of rapid heating and kiln clogging of coal gangue after ignition. However, it will cause the temperature of the fixed carbon combustion area to drop rapidly after the combustion of volatile gases. The slow combustion rate of coal gangue will cause a decrease in kiln output. This is the main reason why the existing tunnel kiln sintering technology cannot improve the single-line disposal capacity when disposing of super-internal combustion coal gangue.

[0006] The elemental sulfur, organic sulfur, and pyrite in gangue are oxidized into sulfur dioxide after combustion at temperatures exceeding 300°C. When gangue products are burned in conventional tunnel kilns, rotary kilns, or sintering machines, the sulfur dioxide produced during the combustion process can only be desulfurized with lime. The higher the sulfur content of the gangue, the higher the cost of flue gas desulfurization. To reduce the cost of desulfurization after gangue combustion, some companies mix limestone with the gangue in a certain proportion before burning it. While this method can achieve some desulfurization, it also results in excessive lime content in the final residue, affecting its quality. Much like the slag emitted by circulating fluidized bed boilers, it is difficult to further utilize. In particular, when using the residue from gangue combustion for ditch filling or producing water-retaining ceramsite for desert landscaping, it must be completely free of lime (calcium oxide), as this will make the surrounding water alkaline and prevent plant growth.

[0007] When conventional tunnel kilns, rotary kilns, and sintering machines are used to fire gangue products, especially under super internal combustion conditions (high calorific value above 500Kcal / Kg), the kiln temperature is often controlled by increasing the cold air flow. This results in the oxygen content in the final flue gas being close to 20%, which is much higher than the oxygen content in the flue gas emitted by power station boilers (generally around 5%). This causes the kiln to emit several times more flue gas than power station boilers, and the kiln's flue gas losses also increase exponentially. In addition, the flue gas temperature ultimately sent to the waste heat boiler is only around 500°C, which reduces the actual heat that can be recovered by the waste heat boiler by several times. The waste heat boiler can only be configured for medium temperature and medium pressure at its highest, and the efficiency of power generation through the steam turbine is relatively low.

[0008] In the existing technology of producing ceramsite using a belt sintering machine, the gas discharged from the ignition section and the combustion section (also called the self-calcining section) is pressurized by a fan and then passed into the sintering machine to preheat the ceramsite. The low-temperature gas discharged from the preheating section of the sintering machine is then passed through a fan as a heat source for drying and dehydrating the ceramsite. Finally, the low-temperature gas below 100°C is sent to a desulfurization tower for treatment after passing through an induced draft fan and a dust collector, and then discharged into the air. This will increase the amount of flue gas discharged through the chimney, and the exhaust loss caused by the low-temperature gas at 100°C is even greater. There are two other problems with this method during large-scale industrial production: First, some SO2 has been generated in the gas discharged from the ignition section and the combustion section (also called the self-roasting section). When it is pressurized by the fan and sent to the preheating section and the drying and dehydration section, the gas inlet of the preheating section and the drying and dehydration section will be at positive pressure due to various reasons such as changes in the material layer resistance. A small amount of irritating gas will overflow and pollute the production environment in the workshop; second, some volatile gases are precipitated in the temperature zone of about 400°C in the preheating section and the ignition section, but they cannot ignite and burn, and can only be discharged into the atmosphere together with the low-temperature gas, resulting in some chemical energy of the coal gangue not being fully utilized.

[0009] Therefore, major coal-producing regions require kilns capable of rapidly burning 500-1500 kcal / kg of gangue. After decarbonization, the gangue can be used as local building materials or for ditch filling and land reclamation, eliminating the spontaneous combustion of the gangue and polluting the atmosphere. To reduce gangue disposal costs, technologies with low flue gas desulfurization costs, high waste heat recovery rates, and good economic benefits are also needed. Summary of the Invention

[0010] The present invention aims to solve the following technical problems:

[0011] 1. No other ingredients are needed to directly burn the gangue into ceramsite or gravel;

[0012] 2. Solve the problem of coal gangue easily becoming compacted during combustion;

[0013] 3. Solve the problem of deflagration caused by the rapid precipitation of volatile matter during the combustion of coal gangue, and the problem of poor decarbonization effect caused by incomplete combustion of fixed carbon in coal gangue.

[0014] In order to achieve the above-mentioned purpose, the present invention adopts the following technical means:

[0015] The present invention provides a method for rapidly burning and decarbonizing coal gangue, comprising the following steps:

[0016] Step 1: crushing, screening, grinding and transporting the gangue to obtain gangue particles of 6 to 20 mm and fine powder of 100 to 200 mesh, and the fine powder of 100 to 200 mesh is then processed into gangue particles of 6 to 20 mm by a granulator;

[0017] Step 2: The 6-20 mm coal gangue particles obtained in step 1 are fed into a belt dryer for drying to obtain dried coal gangue particles;

[0018] Step 3: The dried gangue particles obtained in step 2 are fed into a belt dryer for preheating to obtain preheated gangue particles;

[0019] Step 4: The preheated gangue particles obtained in step 3 enter a pyrolysis device for low-temperature dry distillation to separate part of the volatile gas to obtain pyrolyzed gangue particles. The volatile content of the pyrolyzed gangue particles is 4% to 6%.

[0020] Step 5: The pyrolyzed gangue particles obtained in step 4 are fed into the tunnel kiln of the belt sintering machine through the intermediate silo 2 for self-roasting treatment to obtain self-roasted gangue particles;

[0021] Step 6: The self-calcined gangue particles obtained in step 5 are subjected to decarbonization and combustion treatment in a belt sintering machine tunnel kiln to obtain decarbonized and burned gangue particles, namely, water-retaining ceramsite;

[0022] Step 7: When producing high-strength ceramsite or gravel for building materials, the decarbonized gangue particles need to be subjected to deep combustion and decarbonization in a rotary kiln and supplemented with fuel for surface high-temperature vitrification treatment to obtain gangue particles with a compressive strength greater than 6.5 MPa, i.e., high-strength ceramsite or gravel;

[0023] In step 8, the decarbonized and burned gangue particles obtained in step 6 are fed into a cooler (vertical cooler or grate cooler) for forced cooling to obtain cooled water-retaining ceramsite. The gangue particles obtained in step 7 are fed into a cooler (vertical cooler or grate cooler) for forced cooling to obtain cooled high-strength ceramsite and gravel, and hot air at 500-850°C is obtained at the same time.

[0024] In the above method, the steps of step 1 include:

[0025] Step 1.1, crushing the coal gangue to obtain massive coal gangue;

[0026] Step 1.2, screening the massive gangue obtained in step 1.1 to obtain gangue particles of 6 to 20 mm and gangue below 6 mm;

[0027] Step 1.3, grinding the coal gangue less than 6 mm obtained in step 1.2 to obtain a fine powder of 100 to 200 mesh;

[0028] Step 1.4, granulating the 100-200 mesh fine powder obtained in step 1.3 to obtain 6-20 mm coal gangue particles;

[0029] Step 1.5: The 6-20 mm coal gangue particles obtained in step 1.2 and the 6-20 mm coal gangue particles obtained in step 1.4 are transported and sent to the hopper on the upper part of the belt dryer via a belt conveyor.

[0030] In the above method, step 2 includes:

[0031] Step 2.1, the gangue particles in the silo are evenly distributed on the grate plate of the belt dryer through the distribution device;

[0032] Step 2.2, using 150-200° C. flue gas discharged from a waste heat boiler flue gas outlet to dry the gangue particles to obtain dried gangue particles;

[0033] Step 2.3: The low-temperature flue gas of 70-100°C discharged after drying is sent to the flue gas treatment system through the boiler induced draft fan to meet emission standards.

[0034] In the above method, the steps of step 3 include:

[0035] Step 3.1: The high-temperature blower sends room-temperature air into the cooler (vertical cooler or grate cooler), and the temperature rises to 500-850°C when passing through the material layer;

[0036] Step 3.2: To control the hot air temperature at the high-temperature blower inlet within the range of 500-600°C, a steam superheater covering part of the heat exchange area of ​​the waste heat boiler is arranged between the cooler and the high-temperature blower.

[0037] Step 3.3: The hot air temperature is controlled by adjusting the steam flow rate of the steam superheater. The high-temperature blower sends hot air at 500-600°C to the lower part of the grate in the preheating zone of the belt dryer.

[0038] Step 3.4: After passing through the material layer, the hot air at 500-600°C is cooled to 250-300°C. The hot air at 250-300°C enters the air heater in the middle section of the waste heat boiler from the hot air duct at the top of the belt dryer preheating zone.

[0039] Step 3.5: The hot air is heated to 550-600°C in the air heater, and then enters the ignition zone (self-calcination section) and the upper part of the decarbonization combustion zone of the belt sintering machine tunnel kiln through the hot air duct to supply combustion-supporting hot air for the combustion of fixed carbon. The ignition zone is the self-calcination section.

[0040] In the above method, step 4 includes:

[0041] Step 4.1: The preheated gangue in the preheating zone enters the intermediate silo 1 under the action of gravity to prevent air from entering the pyrolysis device. The preheated gangue in the intermediate silo 1 enters the pyrolysis device of the rotary kiln structure through the drop pipe under the action of gravity;

[0042] Step 4.2: Using the 650-800°C flue gas from the ignition zone (also called the self-calcining section) and the lower part of the grate in the decarbonization combustion zone of the belt sintering machine tunnel kiln as an external heat source, the gangue particles are rapidly heated to 400-500°C in the sealed container of the pyrolysis device;

[0043] In step 4.3, the gangue particles are partially separated from the volatile gases in a sealed container, resulting in pyrolyzed gangue particles and volatile gases. The rotary kiln speed is controlled to adjust the residual volatile content in the pyrolyzed gangue particles to approximately 4% to 6%. The rotary kiln rotates at a relatively slow speed, typically 1 rpm. This speed adjustment is intended to control the heating time of the gangue particles within the rotary kiln container. The faster the speed, the shorter the retention time of the gangue particles within the container, and the less volatiles are released from the gangue particles.

[0044] Step 4.4: The volatile gas separated in the closed container of the pyrolysis device first enters an indirect water-cooled gas cooling device to cool down and separate the coal tar. The remaining volatile gas is sent to the burner above the ignition zone and the rotary kiln inlet through the gas booster fan and the gas pipeline through the gas valve group to be burned as auxiliary fuel.

[0045] In the above method, step 5 includes:

[0046] The pyrolyzed gangue particles in step 5.1 and step 4.3 enter the intermediate silo 2 under the action of gravity, and are then evenly distributed on the grate plate of the ignition zone (also called the self-baking section) of the tunnel kiln of the belt sintering machine through the distribution device;

[0047] The hot air of 250-300°C in step 5.2 and step 3.4 is reheated to 550-600°C hot air by the high-temperature flue gas of 650-800°C on the flue gas side of the waste heat boiler;

[0048] Step 5.3: Hot air at 550-600°C enters the belt sintering machine tunnel kiln from the upper portion of the ignition zone (also called the self-calcining section) and passes through the material layer from top to bottom, causing the gangue particles to self-calculate, thereby obtaining self-calcined gangue particles.

[0049] Step 5.4: The flue gas temperature coming out from the lower part of the grate plate in the firing zone of the belt sintering machine tunnel kiln will reach 650-800°C. Part of the flue gas at 650-800°C directly enters the desulfurization device in the furnace through the flue gas duct, and the other part of the flue gas at 650-800°C passes through the evaporative heat exchanger with a partial heat exchange area of ​​the waste heat boiler to reduce the flue gas temperature to 500-600°C and enters the high-temperature induced draft fan for pressurization. The pressurized flue gas at 500-600°C then enters the rotary kiln to provide oxygen for the combustion of the auxiliary fuel.

[0050] In the above method, step 6 includes the following steps:

[0051] The hot air of 250-300°C in step 6.1 and step 3.4 is reheated to 550-600°C hot air by the high-temperature flue gas of 650-800°C on the flue gas side of the waste heat boiler;

[0052] Step 6.2: Hot air at 550-600° C. enters the belt sintering machine tunnel kiln from the upper portion of the decarbonization and combustion zone and passes through the material layer from top to bottom, decarbonizing and burning the gangue particles to obtain decarbonized and burned gangue particles.

[0053] Step 6.3: The temperature of the flue gas coming out from the lower part of the grate plate in the firing zone of the belt sintering machine tunnel kiln will reach 650-800°C. Part of the flue gas at 650-800°C directly enters the desulfurization device in the furnace through the flue gas duct. Another part of the flue gas at 650-800°C passes through the evaporative heat exchanger with a partial heat exchange area of ​​the waste heat boiler to reduce the flue gas temperature to 500-600°C and enters the high-temperature induced draft fan for pressurization. The pressurized flue gas at 500-600°C then enters the rotary kiln to provide oxygen for the combustion of the auxiliary fuel. Another part of the flue gas at 500-600°C is pressurized by the high-pressure fan and enters the bottom of the desulfurization device in the furnace to blow up the limestone powder and put it in a suspended state.

[0054] In the above method, the steps of step 7 include:

[0055] Step 7.1: When high-strength ceramsite or gravel for building materials is to be produced, the coal gangue particles after decarbonization and combustion are dropped into the rotary kiln by gravity;

[0056] Step 7.2: Add auxiliary fuel at the rotary kiln outlet and continue high-temperature combustion until the fixed carbon in the gangue is substantially burned out, thereby obtaining decarbonized gangue particles.

[0057] Step 7.3: The flue gas at 950-1150°C discharged from the flue gas outlet of the rotary kiln enters the desulfurization device in the furnace through the high-temperature flue gas pipeline, is cooled to 150-200°C by the waste heat boiler, and then enters the belt dryer to dry the coal gangue particles;

[0058] The flue gas at 650-800° C. entering the furnace desulfurization device in step 7.4 and step 6.3 and the flue gas at 950-1150° C. entering the furnace desulfurization device in step 7.3 are mixed with the suspended limestone powder in the furnace desulfurization device to generate lime under high temperature conditions;

[0059] Step 7.5: The high-temperature flue gas in the furnace desulfurization device undergoes a chemical reaction with lime to undergo desulfurization and then enters the high-temperature separator. The desulfurized flue gas enters the waste heat boiler for heat exchange to generate high-temperature and high-pressure steam. The solid powder at the bottom of the high-temperature separator is returned to the furnace desulfurization device for circulation through the reflux pipe and the reflux control valve.

[0060] In the above method, step 8 includes:

[0061] Step 8.1: The decarbonized and burned water-retaining ceramsite obtained in step 6 is dropped into a cooler by gravity, and the high-strength ceramsite and gravel obtained in step 7 are dropped into a cooler by gravity;

[0062] Step 8.2: The blower sends room temperature air into the lower part of the cooler from bottom to top through the material layer to forcefully cool the product, which is water-retaining ceramsite, high-strength ceramsite or gravel;

[0063] Step 8.3: The cooled products (water-retaining ceramsite or high-strength ceramsite, gravel) are sent to the silo for storage via a belt conveyor;

[0064] Step 8.4: Normal temperature air passes through the material layer from bottom to top in the cooler (vertical cooler or grate cooler) and is heated to 500-850°C hot air.

[0065] The present invention also provides a device for rapidly burning and decarbonizing coal gangue, comprising:

[0066] Raw material preparation system: including crusher, screening machine, grinding machine, granulator, and silo. It is used to crush the gangue by the crusher and screen it. The 6-20mm gangue particles obtained are fed into the silo. The 100-200 mesh fine powder obtained after screening is fed into the granulator after passing through the grinding machine to produce 6-20mm gangue particles.

[0067] Kiln firing system: includes a belt dryer, a belt sintering machine tunnel kiln, a rotary kiln, and a cooler. The belt sintering machine tunnel kiln includes a ignition zone and a decarbonization combustion zone. The gangue particles are fed into the belt dryer for drying and then into the belt dryer preheating zone for preheating. The preheated gangue particles are then fed into the pyrolysis device through the intermediate silo 1 for low-temperature dry distillation. They are then fed into the ignition zone, decarbonization combustion zone, and rotary kiln of the belt sintering machine tunnel kiln through the intermediate silo 2 for ignition and decarbonization combustion, and finally forced cooling in the cooler.

[0068] Pyrolysis device: used to separate volatile gases from coal gangue particles, including a pyrolysis device body with heat-resistant steel as a container, a volatile gas cooling device, a volatile gas pressurizing blower, a gas valve group and a gas burner;

[0069] In-furnace desulfurization device: connected to the flue gas duct at the outlet of the belt sintering machine tunnel kiln and the flue gas duct at the outlet of the rotary kiln;

[0070] Waste heat boiler: connected to the flue gas duct at the outlet of the desulfurization device in the furnace, including air heater, waste heat boiler evaporator, superheater, economizer and other heat exchange components, as well as riser and downcomer, header, soot blower, ash hopper, ash discharge valve and other boiler accessories;

[0071] The flue gas and air system is connected to the belt sintering machine tunnel kiln, rotary kiln, in-furnace desulfurization device, and waste heat boiler. It includes: a blower installed at the front end of the fired product cooler; a high-temperature blower between the cooler hot air outlet and the hot air inlet of the belt dryer preheating zone; a high-temperature induced draft fan between the belt sintering machine tunnel kiln flue gas outlet and the rotary kiln; a waste heat boiler; and a boiler induced draft fan at the belt dryer flue gas outlet. A high-pressure blower installed between the belt sintering machine tunnel kiln outlet and the in-furnace desulfurization device suspends the limestone powder inside the in-furnace desulfurization device.

[0072] Flue gas treatment system: includes desulfurization and denitrification dust collector connected to the boiler induced draft fan.

[0073] Because the present invention adopts the above technical means, it has the following beneficial effects:

[0074] (1) The present invention directly burns 500-1500Kcal / Kg of coal gangue without adding other raw materials such as clay and shale to turn it into building materials or use it for ditch filling, desert control, and soil improvement. The coal gangue after combustion and decarbonization will no longer pollute the atmospheric environment due to spontaneous combustion in nature, which completely solves the problems of solid waste land occupation and high maintenance costs of coal gangue environmentally friendly landfill.

[0075] (2) In the kiln system of the present invention, it only takes a few hours for the gangue particles to be dried and cooled to the finished product. The processing capacity of each production line is 1 to 5 times higher than that of conventional tunnel kilns and rotary kilns, which can achieve the goal of burning gangue in large quantities and quickly.

[0076] (3) The flue gas emission of the present invention is more than 50% less than that of the fired brick tunnel kiln, ceramsite rotary kiln and sintering machine of the same scale, which not only reduces the smoke exhaust loss, but also reduces the power consumption of the fan, and can also reduce the cost of the smoke and air system and the flue gas treatment system.

[0077] (4) The present invention fully burns all the volatile gases released from the coal gangue particles during the heating process from preheating to ignition in the high-temperature area, preventing the volatile gases released in the low-temperature area from being discharged from the kiln because they cannot reach the ignition temperature, so that the chemical energy of the coal gangue can be fully utilized.

[0078] (5) The combustion zone of volatile matter that continues to precipitate from the gangue with 4% to 6% volatile matter remaining after pyrolysis requires 500-600℃ high-temperature hot air as the medium. By increasing the amount of 500-600℃ hot air, the temperature of the volatile matter gas after combustion is controlled to not exceed 800℃. This can prevent the rapid temperature rise during the ignition stage, which causes the gangue particles to form blocks on the grate plates of the belt sintering machine tunnel kiln ignition zone (also called self-baking section) and decarbonization combustion zone, and block the kiln.

[0079] (6) Pyrolysis is completely dependent on the high temperature environment formed by the initial combustion of coal gangue. At the same time, the volatile gas separated by the pyrolysis device can be used to replace auxiliary fuels such as natural gas. By the way, a small amount of coal tar precipitated after the coal gangue is heated can be extracted, so that the economically valuable components in the solid waste can be reasonably utilized.

[0080] (7) The present invention fully utilizes the waste heat of the kiln smoke and wind system according to the principles of "cascade utilization" and "high quality and high use", and recycles the low-temperature smoke gas and low-temperature hot air of about 300°C in the system, so that the temperature of the smoke entering the waste heat boiler finally reaches 900-950°C, which greatly improves the heat exchange efficiency and can increase the steam parameters of the waste heat boiler from low temperature and low pressure to high temperature and high pressure or ultra-high temperature and ultra-high pressure, creating favorable conditions for efficiently recovering low-grade chemical energy in coal gangue, improving the power generation efficiency of steam turbines, and reducing the production cost of coal gangue disposal, which is conducive to promoting technological progress in solid waste disposal.

[0081] (8) In the smoke and air system of the present invention, all smoke ducts or kiln areas where smoke may overflow are under negative pressure, effectively preventing irritating gases from polluting the production environment in the workshop.

[0082] (9) Since the market price of limestone powder is 5 to 10 times lower than that of lime, limestone powder is selected as a desulfurizer. The limestone powder is sent into a high temperature environment of 650 to 1150 ° C to quickly decompose into lime. The sulfur dioxide in the flue gas reacts with lime to generate CaSO4 to achieve the purpose of in-furnace desulfurization. While meeting the cost of flue gas desulfurization and reducing it by several times, the residual solids after the combustion of coal gangue will not be contaminated by lime. Its composition is close to that of soil and can be used to fill ditches and create land or produce water-retaining expanded clay for desert greening.

[0083] (10) The present invention effectively solves the problem of difficulty in controlling kiln temperature caused by the explosion of volatile gases released when the temperature of gangue particles rises to about 500°C in the kiln under super internal combustion conditions (the kiln temperature suddenly rises from 500-700°C to the gangue vitrification temperature of 1000-1300°C, which will cause the fixed carbon inside the gangue particles to appear in liquid phase on the surface before they are fully burned and isolate them from oxygen, resulting in poor decarbonization effect of the gangue). The pyrolysis device controls the precipitation and recovery of volatile gases, effectively avoiding the problem of poor decarbonization effect caused by the explosion and vitrification phenomenon.

[0084] (11) The coal gangue particles with a size of 6 to 20 mm that are crushed and screened can be decarbonized and burned in the tunnel kiln of a belt sintering machine to produce solid materials that can be used to fill ditches and create land; the coal gangue with a size of less than 6 mm that is crushed and screened can be made into 6 to 20 mm ceramsite particles, which can be decarbonized and burned in the tunnel kiln of a belt sintering machine to produce water-retaining ceramsite for soil improvement and desert greening. The crushed and sieved 6-20mm coal gangue particles, after completing decarbonization and combustion in the belt sintering machine tunnel kiln and entering the rotary kiln, can produce gravel to replace concrete stones and roadbed cushion layers when the rotary kiln firing temperature is controlled within 50℃ above the gangue vitrification temperature; the crushed and sieved coal gangue below 6mm is made into 6-20mm ceramsite, after completing decarbonization and combustion in the belt sintering machine tunnel kiln and entering the rotary kiln, can produce high-strength ceramsite for lightweight concrete and water treatment and filtration when the rotary kiln firing temperature is controlled within 50℃ above the gangue vitrification temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0085] Figure 1 Schematic diagram of material flow;

[0086] Figure 2 Schematic diagram of flue gas flow direction;

[0087] Figure 3 The figure is a temperature control curve, where the pure white line corresponds to the flue gas temperature and the light-colored line corresponds to the internal temperature of the material bed. The present invention controls the temperature in the belt sintering machine tunnel kiln by pyrolysis to prevent ignition and deflagration of volatile matter in the belt sintering machine tunnel kiln. The temperature of the gangue particles during combustion in the belt sintering machine tunnel kiln is controlled to not exceed 800°C, preventing the gangue from agglomerating on the grate. When the raw material is pyrolyzed at around 600°C and the sintering temperature is raised to 1008°C, the product does not agglomerate.

[0088] Figure 4 for Figure 3 Schematic diagram of the product obtained after temperature control;

[0089] Figure 5 This is the temperature control curve when the raw material is directly heated to about 1103℃. As shown in the figure, the pure white curve suddenly rises, and the product has a lot of lumps;

[0090] Figure 6 for Figure 5 Schematic diagram of the product obtained after temperature control;

[0091] Figure 7Thermogravimetric analysis shows that the temperature range for rapid volatile precipitation (pyrolysis) in coal gangue occurs primarily between 400-500°C. Thermogravimetric analysis results indicate that during calcination of the ground sample from room temperature to 1100°C, the primary weight loss components are CO2 and H2O, with minimal other substances. The weight loss range is primarily between 300 and 600°C, where mineral dehydration and carbon oxidation are predominant, with the most rapid weight loss occurring between 400 and 500°C. Above 800°C, the sample exhibits minimal weight change, indicating minimal decomposition and oxidation reactions.

[0092] Explanation of the accompanying symbols: 1. Crusher; 2. Screening machine; 3. Pulverizer; 4. Granulator; 5. Silo; 6. Belt dryer; 7. Preheating zone; 8. Intermediate silo 1; 9. Pyrolysis device; 10. Intermediate silo 2; 11. Ignition zone; 12. Decarbonization combustion zone; 13. Rotary kiln; 14. Cooler; 15. Blower; 16. Volatile gas cooling device; 17. Volatile gas pressure blower; 18. Gas valve group; 19. Boiler induced draft fan; 20. Desulfurization dust collector; 21. In-furnace desulfurization device; 22. High-temperature separator; 23. Waste heat boiler; 24. Air heater; 25. SCR denitrification device; 26. High-pressure fan; 27. High-temperature blower; 28. High-temperature induced draft fan; 29. ​​Boiler evaporator component; 30. Boiler superheater component; 31. Boiler heat exchanger component. DETAILED DESCRIPTION

[0093] The following is a detailed description of the embodiments of the present invention. Although the present invention will be described and illustrated in conjunction with certain specific embodiments, it should be noted that the present invention is not limited to these embodiments. On the contrary, modifications or equivalent substitutions of the present invention are intended to fall within the scope of the claims of the present invention.

[0094] In addition, in order to better illustrate the present invention, numerous specific details are given in the following detailed description. It will be understood by those skilled in the art that the present invention can also be implemented without these specific details.

[0095] The object of the present invention is to overcome the above-mentioned problems by combining a tunnel kiln, a rotary kiln, and a sintering machine with a waste heat boiler that passively receives waste heat from flue gas, flue gas desulfurization technology within a circulating fluidized bed boiler, and low-temperature dry distillation (pyrolysis) technology of coal gangue, thereby providing a method specifically for rapidly burning 500 to 1500 kcal / kg of coal gangue. This method not only converts most of the energy in the coal gangue into the energy of high-temperature, high-pressure steam, but also enables a large amount of coal gangue to be rapidly decarbonized and burned into building materials or environmentally friendly solid materials for ditch filling and land reclamation. Furthermore, the present invention can achieve low-cost desulfurization of flue gas within the furnace and recycling of low-temperature flue gas and low-temperature hot air within the system. Furthermore, the present invention can achieve stable and controllable temperature during high-temperature firing under super-internal combustion conditions with a relatively low air volume, resulting in less smoke exhaust. This method turns harm into benefit, reduces costs, and increases efficiency, greatly promoting the healthy development of the resource utilization industry for bulk solid waste (coal gangue, gasified slag).

[0096] The purpose of the present invention is achieved through the following technical solutions:

[0097] A method for rapid combustion and decarbonization of coal gangue, including a raw material preparation system for coal gangue crushing, screening, grinding, and transportation, a kiln firing system for drying, preheating, igniting, decarbonizing, burning, and forced cooling of coal gangue particles, a pyrolysis device for separating volatile gases from coal gangue particles, an in-furnace desulfurization device and a waste heat boiler connected to the flue gas ducts at the outlets of a belt sintering machine tunnel kiln and a rotary kiln, and a flue gas system connected to the belt dryer, the belt sintering machine tunnel kiln, the rotary kiln, the in-furnace desulfurization device, and the waste heat boiler, and also includes a kiln flue gas treatment system connected to the boiler induced draft fan.

[0098] Kiln firing system: including belt dryer, belt sintering machine tunnel kiln, rotary kiln and cooler

[0099] The smoke and air system includes: a blower installed at the front end of the fired product cooler, a high-temperature blower between the hot air outlet of the cooler and the hot air inlet of the preheating zone of the belt dryer, a high-temperature induced draft fan between the flue gas outlet of the belt sintering machine tunnel kiln and the rotary kiln, boiler induced draft fans at the waste heat boiler and the flue gas outlet of the belt dryer, and a high-pressure fan installed between the outlet of the belt sintering machine tunnel kiln and the in-furnace desulfurization device to suspend the limestone powder inside the in-furnace desulfurization device.

[0100] Furthermore, the raw material preparation system includes processes such as gangue crushing, screening, grinding, and belt conveying. The purpose is to crush the massive gangue into particles smaller than 20 mm, which are then screened. The 6-20 mm portion above the screen is transported via a belt conveyor to a silo located above the drying zone of the belt sintering machine tunnel kiln. The gangue below the screen (less than 6 mm) is ground into a fine powder with a mesh size of 100-200. This powder is then processed through a granulator to produce 6-20 mm ceramsite, which is then transported via a belt conveyor to a silo located above the drying zone of the belt sintering machine tunnel kiln.

[0101] Furthermore, the kiln firing system consists of a belt dryer, a belt sintering tunnel kiln, a rotary kiln, and a cooler. The belt dryer is functionally divided into a drying zone and a preheating zone, while the belt sintering tunnel kiln is divided into a ignition zone (also called a self-calcining zone) and a decarbonization combustion zone based on its function and kiln temperature. 6-20 mm coal gangue particles delivered from the raw material preparation system are evenly distributed on the belt dryer's grate through a distribution device from the silo. 150-200°C flue gas discharged from the waste heat boiler's flue gas outlet, under the negative pressure of the boiler's induced draft fan, flows downward through the material layer and grate, drying the 6-20 mm coal gangue particles. All parts of the belt dryer that come into contact with the flue gas are constructed of sulfur-corrosion-resistant steel. The belt dryer and belt sintering machine tunnel kiln are powered by two electric sprockets in front and behind. The electric sprockets drive the 6-20mm coal gangue particles on the grate plate to move forward in a straight line at a set speed. Rollers are installed at the bottom of the grate plate to bear the weight of the grate plate and coal gangue. The rollers can roll back and forth on the track, which is arranged on the steel beam of the steel structure. The grate plate is made of heat-resistant steel material and is densely covered with a large number of 5mm small holes, through which hot air or flue gas can pass. After being dried and dehydrated by the belt dryer, the gangue particles enter the preheating zone of the belt dryer. The high-temperature blower blows the 500-600℃ hot air from the cooler upward from the lower part of the grate plate in the preheating zone of the belt dryer through the material layer to heat the 6-20mm gangue particles. The 6-20mm gangue particles are heated from 50-100℃ to 300-400℃ and then enter the pyrolysis device through the intermediate silo 1. The 400-500℃ gangue coming out of the pyrolysis device still has about 5% volatile matter remaining. The pyrolyzed gangue enters intermediate silo 2. A distributor distributes the pyrolyzed gangue particles evenly onto the grate of the belt sintering machine's tunnel kiln. During the pyrolysis process, the remaining volatile matter (approximately 5%) within the gangue continues to precipitate at temperatures between 500°C and 600°C. This volatile gas mixes with oxygen in the combustion zone and rapidly combusts, initiating combustion of the fixed carbon within the gangue particles. This fixed carbon is essentially consumed in the decarbonization combustion zone. The volatile gas released from the pyrolysis is then fed via a pipeline, an indirect water-cooled gas cooling device, and a gas pressure blower to the burners located above the belt sintering machine's tunnel kiln's combustion zone and at the rotary kiln inlet, where it is burned as auxiliary fuel. If only the gangue needs to be processed into water-retaining ceramsite or only decarbonization is required, the high-temperature gangue coming out of the belt sintering machine tunnel kiln directly enters the cooler (vertical cooler or grate cooler), and is cooled to below 100°C under the forced cooling conditions of the blower, and finally enters the finished product warehouse for storage and transportation via a multi-stage belt conveyor.

[0102] If the gangue needs to be processed into high-strength expanded clay or gravel for building materials, the 6-20mm gangue particles that have basically completed decarbonization in the belt sintering machine tunnel kiln fall into the rotary kiln under the action of gravity for deep combustion and decarbonization. Auxiliary fuel (liquefied natural gas, petroleum gas or coal powder) is added to the rotary kiln to continue combustion until all the fixed carbon in the gangue is burned out. The gangue then enters the cooler (vertical cooler or grate cooler) and is cooled to below 100°C under the forced cooling conditions of the blower. Finally, it is transported to the finished product warehouse via a multi-stage belt conveyor for storage.

[0103] Furthermore, in the smoke and air system of the kiln, the blower sends room temperature air into the cooler (vertical cooler or grate cooler) and the temperature will rise to 500-850℃ when passing through the material layer. In order to control the hot air at the inlet of the high-temperature blower to be in the range of 500-600℃, a steam superheater with a partial heat exchange area of ​​the waste heat boiler is arranged between the cooler and the high-temperature blower. The hot air temperature is controlled by adjusting the steam flow rate. The high-temperature blower sends the hot air of 500-600℃ to the lower part of the grate plate in the preheating zone of the belt dryer to pass through the material layer to heat the coal gangue particles; the hot air of 500-600℃ will be cooled to 250-300℃ after passing through the material layer, and the hot air of 250-300℃ enters the air heater in the middle section of the waste heat boiler from the hot air duct at the upper part of the preheating zone of the belt dryer, and is reheated to hot air of 550-600℃ by the high-temperature flue gas of 650-800℃ on the flue gas side of the waste heat boiler. The hot air of 550-600℃ enters the belt sintering machine tunnel kiln from the ignition zone (also called self-baking section) and the upper part of the decarbonization combustion zone, and passes through the material layer from top to bottom. The 6-20mm coal gangue particles continue to precipitate under high temperature conditions, and the 4%-6% volatile matter (hydrocarbons, CO, H2, etc.) remaining after pyrolysis mixes with oxygen and starts to ignite and burn rapidly, and gradually burns the fixed carbon inside the coal gangue particles. The temperature is between 650 and 750°C; a large amount of heat will be released during the combustion of volatile matter and fixed carbon. The flue gas temperature coming out from the lower part of the grate in the ignition zone (also called self-baking section) and decarbonization combustion zone (combustion temperature is 700 to 800°C) of the belt sintering machine tunnel kiln will reach 650 to 800°C (the combustion zone where the volatile matter of the coal gangue with 4% to 6% volatile matter remaining after pyrolysis continues to precipitate requires a large air volume to control the flue gas temperature not to exceed 800°C). A small amount of flue gas with a temperature of 650-800℃ enters the desulfurization device in the furnace directly through the flue gas duct. Most of the flue gas with a temperature of 650-800℃ passes through the evaporative heat exchanger with a partial heat exchange area of ​​the waste heat boiler to reduce the flue gas temperature to 500-600℃ and enters the high-temperature induced draft fan for pressurization. The pressurized flue gas with a temperature of 500-600℃ then enters the rotary kiln to provide oxygen for the combustion of auxiliary fuel. The flue gas with a temperature of 950-1150℃ discharged from the flue gas outlet of the rotary kiln enters the desulfurization device in the furnace through the high-temperature flue gas duct, and then is cooled to 150-200℃ by the waste heat boiler before entering the drying area of ​​the belt dryer to dry the coal gangue particles. The low-temperature flue gas with a temperature of 70-100℃ discharged from the drying area of ​​the belt dryer is sent to the flue gas treatment system through the boiler induced draft fan to meet emission standards. The flue gas coming out of the bottom of the belt sintering machine tunnel kiln and cooled to 500-600℃ by the evaporative heat exchanger enters the high-pressure fan. The high-pressure fan pressurizes the 500-600℃ flue gas and then enters the wind hood at the bottom of the furnace desulfurization device, blowing the limestone powder at the bottom into the furnace desulfurization device in a suspended state and mixing with the high-temperature flue gas to decompose into lime.The flue gas (or hot air) generated in the previous process is cooled or heated by a heat exchanger, so that the flue gas (or hot air) participates in the heating and combustion process of the coal gangue multiple times and circulates in the flue gas system to minimize the oxygen content in the final exhaust gas, thereby reducing the total amount of flue gas emissions generated in the coal gangue combustion process and reducing exhaust heat loss, thereby achieving the goal of energy conservation and emission reduction.

[0104] Furthermore, the waste heat boiler (from the in-furnace desulfurization device to the flue gas side outlet of the waste heat boiler) is arranged horizontally, and the 900-950°C flue gas coming out of the in-furnace desulfurization device is arranged in sequence along the flue gas flow channel with the water-cooled wall of the waste heat boiler (boiler water boiling device), evaporative heat exchanger, high-temperature superheater, low-temperature superheater and economizer. Part of the dust in the flue gas naturally settles in the ash hopper at the bottom of the heat exchanger, converting the energy of the high-temperature flue gas into the energy of high-temperature and high-pressure steam. The low-temperature flue gas of 150-200°C after heat exchange is discharged from the waste heat boiler under the negative pressure of the boiler induced draft fan.

[0105] Furthermore, the in-furnace desulfurization device comprises a desulfurizer (limestone powder) feeding system, a membrane wall of the waste heat boiler body, an air distribution plate, an air hood, a high-temperature separator, a reflux pipe, and a reflux control valve. The desulfurizer feeding system delivers 100-200 mesh limestone powder to the bottom of the in-furnace desulfurization device. A small amount of 500-600°C flue gas from a high-pressure fan enters the air distribution plate and air hood, blowing the 100-200 mesh limestone powder at the bottom of the in-furnace desulfurization device into a suspended state. High-temperature flue gas (900-1150°C) from the rotary kiln and a portion of 650-800°C flue gas from the ignition zone (also known as the self-calcining section) and the lower grate of the decarbonization combustion zone of the belt sintering machine tunnel kiln are mixed with the suspended limestone powder in the high-temperature desulfurization space formed by the membrane wall of the waste heat boiler body. The limestone decomposes into CaO in the high-temperature environment, which then reacts with SO2 in the flue gas to form CaSO4, achieving the purpose of in-furnace desulfurization. The mixed airflow enters the high-temperature separator to separate the dust and then enters the waste heat boiler. The separated dust enters the high-temperature desulfurization space composed of the membrane wall of the waste heat boiler through the reflux pipe and reflux control valve according to a certain Ca / S ratio and circulates to improve the utilization rate of limestone powder and lime.

[0106] Furthermore, the gangue pyrolysis device includes a pyrolysis device body, a volatile gas cooling device, a volatile gas pressure blower, a gas valve train, and a gas burner. Using the 650-800°C flue gas from the ignition zone (also known as the self-calcining section) and the lower grate of the decarbonization combustion zone of the belt sintering machine tunnel kiln as an external heat source, the gangue particles are rapidly heated to 400-500°C in a sealed container, allowing some volatile gases (such as hydrocarbons, CO, and H2) to be rapidly released. After pyrolysis, the gangue particles are conveyed via a screw conveyor to the combustion zone of the belt sintering machine's tunnel kiln for further decarbonization and combustion. The released volatile gases are cooled and the coal tar is separated. Then, they are fed by a gas-fired pressure blower to the belt sintering machine's tunnel kiln's ignition zone (also known as the self-calcining section), decarbonization combustion zone, and gas burners at the rotary kiln inlet. This provides fuel for igniting the fixed carbon within the gangue particles, achieving deep combustion and decarbonization, and surface heating and vitrification. The separated coal tar is used as an industrial raw material. The pyrolysis unit itself, as well as the inlet and outlet systems, must be isolated from the air to prevent the release of high-temperature volatile gases from exploding.

[0107] Preferably, the kiln flue gas treatment system has low-temperature flue gas of 150-200°C discharged from the waste heat boiler body, which passes through the material layer from top to bottom to dry the 6-20mm coal gangue particles on the grate of the belt dryer. The low-temperature flue gas of 70-100°C with a higher moisture content passes through the lower part of the grate and enters the desulfurization dust collector through the boiler induced draft fan for treatment and then meets the emission standards.

[0108] Preferably, the waste heat boiler body, belt dryer, belt sintering machine tunnel kiln, rotary kiln, furnace desulfurization device, and flue gas system are also connected to a thermal automatic control system (DCS) and a monitoring system, and are equipped with several sets of thermocouples (resistance), pressure (differential pressure) transmitters, micromanometers, flow meters, electric valves, electric regulating valves and other primary instruments and automatic valves.

[0109] The process steps include:

[0110] Step (1) The gangue is pre-treated through crushing, screening, grinding and other processes to produce 6-20 mm gangue particles, which are then conveyed to the gangue silo on the upper part of the belt dryer via a belt conveyor. The sieved gangue particles below 6 mm are ground into fine powder of 100-200 mesh, and then passed through a granulator to produce 6-20 mm ceramsite, which is then conveyed to the silo on the upper part of the belt dryer via a belt conveyor.

[0111] In step (2), 6-20 mm coal gangue particles are evenly distributed on the grate plate of the belt dryer through the distribution device. After being dried, dehydrated and preheated in the belt dryer, the coal gangue particles enter the intermediate silo 1, the pyrolysis device and the intermediate silo 2 in sequence under the action of gravity to prevent air from entering the pyrolysis device. The 400-500 ° C coal gangue particles that have been pyrolyzed and have 4%-6% volatile matter remaining from the intermediate silo 2 are evenly distributed on the grate plate of the belt sintering machine tunnel kiln through the distribution device. The belt dryer and the belt sintering machine tunnel kiln are powered by an electric sprocket, which drives the 6-20 mm coal gangue particles on the grate plate to move forward in a straight line at a set speed. The 6-20 mm coal gangue particles enter the ignition zone (also called the self-roasting section) and the decarbonization combustion zone in the belt sintering machine tunnel kiln in sequence. For projects that need to process high-strength expanded clay or gravel, the gangue particles that have basically completed decarbonization in the belt sintering machine tunnel kiln fall into the rotary kiln under the action of gravity for deep combustion and decarbonization. Auxiliary fuel (liquefied natural gas, petroleum gas or coal powder) is added to the rotary kiln to continue high-temperature combustion (about 1000-1200℃) and then enter the cooler (vertical cooler or grate cooler). The gangue particles are cooled to below 100℃ under the forced cooling conditions of the blower and then passed through a multi-stage belt conveyor into the finished product warehouse for storage and transportation.

[0112] Step (3) In step (2), gas burners or pulverized coal burners are arranged in the ignition zone (also called self-baking section) of the belt sintering machine tunnel kiln, the upper part of the decarbonization combustion zone and the feed port of the rotary kiln to provide combustion conditions for igniting volatile matter in 6-20 mm coal gangue particles (if the combustion in the ignition zone is unstable, the volatile matter separated by the pyrolysis device is used as auxiliary fuel), fixed carbon and deep combustion decarbonization.

[0113] In step (4), the flue gas at 650 to 800° C. coming out of the ignition zone (also called the self-baking section) and the lower part of the grate in the decarbonization combustion zone of the belt sintering machine tunnel kiln in step (2) is used as an external heat source for the pyrolysis of the gangue particles, and the gangue particles are heated to 400 to 500° C. in the pyrolysis device to separate part of the volatile gas to prevent the gangue particles from rapidly heating up during the ignition stage and causing the gangue particles to clumping on the ignition zone (also called the self-baking section) and the grate in the decarbonization combustion zone of the belt sintering machine tunnel kiln, thereby replacing auxiliary fuels such as natural gas to provide energy for the rotary kiln for producing gravel or high-strength ceramsite.

[0114] In step (5), the pyrolysis device in step (4) uses heat-resistant steel that can withstand a high temperature of 800°C as a container and heat conductor, adopts a rotary kiln structure with controllable speed, and uses 650-800°C flue gas from the lower part of the grate plate in the ignition zone (also called the self-roasting section) and the decarbonization combustion zone as an external heat source for the pyrolysis of the coal gangue particles. The coal gangue to be heated is isolated from the oxygen in the air or flue gas, and only heated without burning. By controlling the speed of the pyrolysis rotary kiln, the content of residual volatile matter in the coal gangue is controlled to be around 5%, which not only ensures that the coal gangue with some volatile matter separated can be ignited at a temperature of 500-600°C, but also plays a role in preventing it from hardening and blocking the gas channel after ignition, so that the fixed carbon in the coal gangue entering the decarbonization combustion zone can fully contact with oxygen and burn rapidly.

[0115] (6) The air at room temperature is sent to the cooler (vertical cooler or grate cooler) through the blower to force cool the decarbonized coal gangue particles coming out of the rotary kiln. The hot air at 500-850℃ coming out of the cooler is heat exchanged through the steam superheater with a partial heat exchange area of ​​the waste heat boiler, and then sent to the preheating area of ​​the belt dryer through the high-temperature blower to provide a heat source for heating the coal gangue particles.

[0116] (7) The hot air at 250-300°C coming out of the upper part of the preheating zone of the belt dryer in step (6) is heated to 550-600°C through the hot air duct and the convection heat exchange air heater of the waste heat boiler, and then enters the ignition zone (also called the self-roasting section) and the upper part of the decarbonization combustion zone of the belt sintering machine tunnel kiln through the hot air duct to supply combustion-supporting hot air for the ignition of the volatile matter of the coal gangue particles and the combustion of fixed carbon.

[0117] (8) The flue gas at 650-800℃ coming out of the ignition zone (also called self-baking section) and the lower part of the decarbonization combustion zone of the belt sintering machine tunnel kiln is fed into the evaporative heat exchanger with a partial heat exchange area of ​​the waste heat boiler through the high-temperature induced draft fan to reduce the flue gas temperature to 500-600℃. The flue gas is then fed into the rotary kiln through the high-temperature induced draft fan to provide oxygen for the combustion of the auxiliary fuel. The flue gas at 950-1150℃ discharged from the flue gas outlet of the rotary kiln enters the desulfurization device and high-temperature separator in the furnace through the high-temperature flue gas pipeline and finally enters the waste heat boiler. The waste heat boiler converts the heat energy of the high-temperature flue gas with the boiler water in the heat exchanger and makes the boiler water absorb heat and vaporize into saturated steam. The superheated steam obtained after the saturated steam passes through the low-temperature superheater, the desuperheater and the high-temperature superheater is discharged from the boiler outlet header to provide high-temperature and high-pressure steam to the steam-using equipment.

[0118] (9) The low-temperature flue gas of 150-200°C after heat exchange in the waste heat boiler in step (8) is sent to the drying area of ​​the belt dryer by the boiler induced draft fan to dry the coal gangue particles. The boiler induced draft fan sends the low-temperature flue gas of 70-100°C discharged from the lower part of the drying area of ​​the belt dryer to the desulfurization dust collector of the flue gas treatment system for treatment, and discharges the flue gas into the atmosphere through the chimney after the flue gas treatment meets the standards.

[0119] In summary, the present invention has the following characteristics:

[0120] 1. Combining the belt sintering machine tunnel kiln with the rotary kiln allows the gangue to be burned in different zones. The ignition and combustion stage of the volatile matter of the gangue is arranged at the front end of the belt sintering machine tunnel kiln, and the combustion stage of the fixed carbon in the gangue is arranged at the middle and rear end of the belt sintering machine tunnel kiln and the front end of the rotary kiln. This solves the problems of difficult kiln temperature control and burn-through caused by the excessively fast combustion rate of the volatile matter and the excessively slow combustion rate of the fixed carbon in the gangue particles.

[0121] 2. Arrange part of the heat exchange device of the waste heat boiler on the smoke and air duct of the kiln, and use the steam flow and bypass flue gas flow to adjust the temperature of the smoke and air duct and the high-temperature area in the kiln respectively, avoiding the use of supplementary cold air to adjust the temperature of the high-temperature area.

[0122] 3. Use low-temperature flue gas and hot air to circulate in the kiln flue and air system to reduce the kiln air supply, reduce the total amount of flue gas emissions, reduce exhaust losses, increase the flue gas temperature entering the waste heat boiler, and maximize the heat exchange efficiency and steam parameters of the waste heat boiler.

[0123] 4. Use limestone powder instead of lime as a desulfurizer. While reducing the cost of flue gas desulfurization, the residual solids after the combustion of coal gangue will not be contaminated by lime and can be used to fill ditches and create land or produce water-retaining ceramsite for desert greening.

[0124] 5. Use the low-temperature flue gas of 150-200℃ emitted by the waste heat boiler as the heat source for drying the coal gangue particles, so that the energy of the coal gangue can be reasonably utilized to the greatest extent.

[0125] 6. The high-temperature flue gas of 650-800℃ generated by the combustion of volatiles in the belt sintering machine tunnel kiln is used as the external heat source of the gangue pyrolysis device. The pyrolysis process of the gangue controls the residual volatile content in the gangue to be around 5% after pyrolysis. This does not affect the normal ignition of the gangue, and prevents the gangue on the grate plate in the decarbonization combustion zone of the belt sintering machine from becoming compacted and blocking the kiln during the subsequent combustion process. Most of the volatile gases in the gangue particles are separated as auxiliary fuel for the ignition zones of the rotary kiln and the belt sintering machine tunnel kiln, thereby reducing the consumption of auxiliary fuel during kiln operation.

[0126] 7. It is conducive to the three-dimensional arrangement of the belt dryer, belt sintering machine tunnel kiln, in-furnace flue gas desulfurization device, rotary kiln and waste heat boiler, which greatly saves the equipment floor space.

Claims

1. A method for rapid combustion and decarbonization of coal gangue, characterized in that: The following steps are involved: Step 1: Processing coal gangue to obtain coal gangue particles; Step 2: The gangue particles obtained in step 1 are fed into a belt dryer for drying to obtain dried gangue particles; Step 3: The dried gangue particles obtained in step 2 are fed into a belt dryer for preheating to obtain preheated gangue particles; Step 3.1: The high-temperature blower sends room-temperature air into the cooler, and the temperature rises to 500-850°C when passing through the material layer; Step 3.2: To control the hot air temperature at the high-temperature blower inlet within the range of 500-600°C, a steam superheater covering part of the heat exchange area of ​​the waste heat boiler is arranged between the cooler and the high-temperature blower. Step 3.3: The hot air temperature is controlled by adjusting the steam flow rate of the steam superheater. The high-temperature blower sends hot air at 500-600°C to the lower part of the grate in the preheating zone of the belt dryer. Step 3.4: After passing through the material layer, the hot air at 500-600°C is cooled to 250-300°C. The hot air at 250-300°C enters the air heater in the middle section of the waste heat boiler from the hot air duct at the top of the belt dryer preheating zone. Step 3.5: The hot air is heated to 550-600°C in the air heater and then enters the ignition zone and the upper part of the decarbonization combustion zone of the belt sintering machine tunnel kiln through the hot air duct, providing combustion-supporting hot air for the combustion of fixed carbon. The ignition zone is the self-calcining section. In step 4, the preheated gangue particles obtained in step 3 enter a pyrolysis device. The 650-800°C flue gas discharged from the lower part of the grate plate in the ignition zone and decarbonization combustion zone of the belt sintering machine tunnel kiln is used as an external heat source. The temperature is raised to 400-500°C in the pyrolysis device for low-temperature dry distillation to separate some volatile gases and obtain pyrolyzed gangue particles. The volatile matter content in the pyrolyzed gangue particles is 4%-6%. Step 5: The pyrolyzed gangue particles obtained in step 4 are fed into a belt sintering machine tunnel kiln through an intermediate silo for self-roasting treatment to obtain self-roasted gangue particles; Step 6: The self-calcined gangue particles obtained in step 5 are subjected to decarbonization and combustion treatment in a belt sintering machine tunnel kiln to obtain decarbonized and burned gangue particles, namely, water-retaining ceramsite; Step 7: When producing high-strength ceramsite or gravel for building materials, the decarbonized gangue particles need to be subjected to deep combustion and decarbonization in a rotary kiln and supplemented with fuel for surface high-temperature vitrification treatment to obtain gangue particles with a compressive strength greater than 6.5 MPa, i.e., high-strength ceramsite or gravel; In step 8, the gangue particles obtained after decarbonization and combustion in step 6 enter the cooler for forced cooling to obtain cooled water-retaining ceramsite. The gangue particles obtained in step 7 are sent to the cooler for forced cooling to obtain cooled high-strength ceramsite and gravel, and hot air at 500-850°C is obtained at the same time.

2. The method for rapid combustion and decarbonization of coal gangue according to claim 1, characterized in that: The steps in Step 1 include: Step 1.1, crushing the coal gangue to obtain massive coal gangue; Step 1.2, screening the massive gangue obtained in step 1.1 to obtain gangue particles of 6 to 20 mm and gangue below 6 mm; Step 1.3, grinding the coal gangue less than 6 mm obtained in step 1.2 to obtain a fine powder of 100 to 200 mesh; Step 1.4, granulating the 100-200 mesh fine powder obtained in step 1.3 to obtain 6-20 mm coal gangue particles; Step 1.5: The 6-20 mm coal gangue particles obtained in step 1.2 and the 6-20 mm coal gangue particles obtained in step 1.4 are transported and sent to the hopper on the upper part of the belt dryer via a belt conveyor.

3. The method for rapid combustion and decarbonization of coal gangue according to claim 1, characterized in that: The steps in Step 2 include: Step 2.1, the gangue particles in the silo are evenly distributed on the grate plate of the belt dryer through the distribution device; Step 2.2, using 150-200° C. flue gas discharged from a flue gas outlet of a waste heat boiler to dry the gangue particles to obtain dried gangue particles; Step 2.3: The low-temperature flue gas of 70-100°C discharged after drying is sent to the flue gas treatment system through the boiler induced draft fan to meet emission standards.

4. The method for rapid combustion and decarbonization of coal gangue according to claim 1, characterized in that: The steps in Step 4 include: Step 4.1: The preheated gangue in the preheating zone enters the intermediate silo 1 under the action of gravity to prevent air from entering the pyrolysis device. The preheated gangue in the intermediate silo 1 enters the pyrolysis device of the rotary kiln structure through the drop pipe under the action of gravity; Step 4.2: Using the 650-800°C flue gas from the lower part of the grate plate in the ignition zone and decarbonization combustion zone of the belt sintering machine tunnel kiln as an external heat source, the gangue particles are rapidly heated to 400-500°C in the sealed container of the pyrolysis device; Step 4.3: Separating a portion of volatile gas from the gangue particles in a sealed container to obtain pyrolyzed gangue particles and volatile gas. The heating time of the gangue particles at a high temperature of approximately 500° C. and the ratio of the volatile gas released are adjusted by controlling the rotational speed to achieve a residual volatile content of approximately 4% to 6% in the gangue particles after pyrolysis. Step 4.4: The volatile gas separated in the closed container of the pyrolysis device first enters an indirect water-cooled gas cooling device to cool down and separate the coal tar. The remaining volatile gas is sent to the burner above the ignition zone and the rotary kiln inlet through the gas booster fan and the gas pipeline through the gas valve group to be burned as auxiliary fuel.

5. The method for rapid combustion and decarbonization of coal gangue according to claim 4, characterized in that: The steps in Step 5 include: The pyrolyzed gangue particles in step 5.1 and step 4.3 enter the intermediate silo 2 under the action of gravity, and are then evenly distributed on the grate plate in the firing zone of the belt sintering machine tunnel kiln through the distribution device; The hot air of 250-300°C in step 5.2 and step 3.4 is reheated to 550-600°C hot air by the high-temperature flue gas of 650-800°C on the flue gas side of the waste heat boiler; Step 5.3: Hot air at 550-600° C. enters the belt sintering machine tunnel kiln from the upper portion of the firing zone and passes through the material layer from top to bottom, causing the gangue particles to self-roast, thereby obtaining self-roasted gangue particles. Step 5.4: The flue gas temperature coming out from the lower part of the grate plate in the firing zone of the belt sintering machine tunnel kiln will reach 650-800°C. Part of the flue gas at 650-800°C directly enters the desulfurization device in the furnace through the flue gas duct, and the other part of the flue gas at 650-800°C passes through the evaporative heat exchanger with a partial heat exchange area of ​​the waste heat boiler to reduce the flue gas temperature to 500-600°C and enters the high-temperature induced draft fan for pressurization. The pressurized flue gas at 500-600°C then enters the rotary kiln to provide oxygen for the combustion of the auxiliary fuel.

6. The method for rapid combustion and decarbonization of coal gangue according to claim 1, characterized in that: Step 6 includes the following steps: The hot air of 250-300°C in step 6.1 and step 3.4 is reheated to 550-600°C hot air by the high-temperature flue gas of 650-800°C on the flue gas side of the waste heat boiler; Step 6.2: Hot air at 550-600° C. enters the belt sintering machine tunnel kiln from the upper portion of the decarbonization and combustion zone and passes through the material layer from top to bottom, decarbonizing and burning the gangue particles to obtain decarbonized and burned gangue particles. Step 6.3: The temperature of the flue gas coming out from the lower part of the grate plate in the firing zone of the belt sintering machine tunnel kiln will reach 650-800°C. Part of the flue gas at 650-800°C directly enters the desulfurization device in the furnace through the flue gas duct. Another part of the flue gas at 650-800°C passes through the evaporative heat exchanger with a partial heat exchange area of ​​the waste heat boiler to reduce the flue gas temperature to 500-600°C and enters the high-temperature induced draft fan for pressurization. The pressurized flue gas at 500-600°C then enters the rotary kiln to provide oxygen for the combustion of the auxiliary fuel. Another part of the flue gas at 500-600°C is pressurized by the high-pressure fan and enters the bottom of the desulfurization device in the furnace to blow up the limestone powder and put it in a suspended state.

7. The method for rapid combustion and decarbonization of coal gangue according to claim 6, characterized in that: The steps in step 7 include: Step 7.1: When high-strength ceramsite or gravel for building materials is to be produced, the coal gangue particles after decarbonization and combustion are dropped into the rotary kiln by gravity; Step 7.2: Add auxiliary fuel at the rotary kiln outlet and continue high-temperature combustion until the fixed carbon in the gangue is substantially burned out, thereby obtaining decarbonized gangue particles. Step 7.3: The flue gas at 950-1150°C discharged from the flue gas outlet of the rotary kiln enters the desulfurization device in the furnace through the high-temperature flue gas pipeline, is cooled to 150-200°C by the waste heat boiler, and then enters the belt dryer to dry the coal gangue particles; The flue gas at 650-800° C. entering the furnace desulfurization device in step 7.4 and step 6.3 and the flue gas at 950-1150° C. entering the furnace desulfurization device in step 7.3 are mixed with the suspended limestone powder in the furnace desulfurization device to generate lime under high temperature conditions; Step 7.5: The high-temperature flue gas in the furnace desulfurization device undergoes a chemical reaction with lime to undergo desulfurization and then enters the high-temperature separator. The desulfurized flue gas enters the waste heat boiler for heat exchange to generate high-temperature and high-pressure steam. The solid powder at the bottom of the high-temperature separator is returned to the furnace desulfurization device for circulation through the reflux pipe and the reflux control valve.

8. The method for rapid combustion and decarbonization of coal gangue according to claim 1, characterized in that: The steps in Step 8 include: Step 8.1: The water-retaining ceramsite obtained after decarbonization and combustion in step 6 falls into a cooler by gravity, and the high-strength ceramsite and gravel obtained in step 7 fall into a cooler by gravity. Step 8.2: The blower sends room temperature air into the lower part of the cooler from bottom to top through the material layer to forcefully cool the product, which is water-retaining ceramsite, high-strength ceramsite or gravel; Step 8.3: The cooled product is sent to the silo for storage via a belt conveyor; Step 8.4: Normal temperature air passes through the material layer from bottom to top in the cooler and is heated to 500-850°C hot air.

9. A device for rapid combustion and decarbonization of coal gangue, characterized in that: include: Raw material preparation system: including crusher, screening machine, grinding machine, granulator, and silo. It is used to crush the gangue by the crusher and screen it. The 6-20mm gangue particles obtained are fed into the silo. The 100-200 mesh fine powder obtained after screening is fed into the granulator after passing through the grinding machine to produce 6-20mm gangue particles. Kiln firing system: includes belt dryer, belt sintering machine tunnel kiln, rotary kiln and cooler. The belt dryer is divided into drying zone and preheating zone according to its function. The belt sintering machine tunnel kiln is divided into ignition zone and decarbonization combustion zone according to its function and kiln temperature. The gangue particles are sent to the belt dryer for drying and then to the preheating zone for preheating. The preheated gangue particles are sent to the pyrolysis device for low-temperature dry distillation. They are then sent to the ignition zone, decarbonization combustion zone, and rotary kiln for ignition and decarbonization combustion, and finally forced to cool in the cooler. Pyrolysis device: used to separate 94%-95% of volatile gases from coal gangue particles, including the pyrolysis device body with heat-resistant steel as the container, volatile gas cooling device, volatile gas pressure blower, gas valve group and burner; In-furnace desulfurization device: connected to the flue gas duct at the outlet of the belt sintering machine tunnel kiln and the flue gas duct at the outlet of the rotary kiln; Waste heat boiler: connected to the flue gas duct at the outlet of the desulfurization device in the furnace, including boiler heat exchange components and boiler accessories. The boiler heat exchange components include air heater, evaporator, superheater, economizer, and boiler accessories include soot blower, ash hopper, ash discharge valve and ash conveying device; The flue gas and air system is connected to the cooler, belt dryer, belt sintering machine tunnel kiln, rotary kiln, furnace desulfurization device, and waste heat boiler. It includes: a blower installed at the front end of the fired product cooler, a high-temperature blower between the cooler hot air outlet and the hot air inlet of the belt dryer preheating zone, a high-temperature induced draft fan and waste heat boiler between the belt sintering machine tunnel kiln flue gas outlet and the rotary kiln, and a boiler induced draft fan at the belt dryer flue gas outlet. A high-pressure blower installed between the belt sintering machine tunnel kiln outlet and the furnace desulfurization device suspends the limestone powder inside the furnace desulfurization device. Flue gas treatment system: includes desulfurization and denitrification dust collector connected to the boiler induced draft fan.

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