What are the principles for selecting a incinerator?

I have some information for your reference! The structural type of the incinerator is related to factors such as the type, nature and combustion form of the waste. Different incineration methods have corresponding incinerators to match them. Usually, incinerators are divided into three types: municipal waste incinerators, general industrial waste incinerators and hazardous waste incinerators based on the hazards of the wastes processed to the environment and human health and the required degree of treatment. However, the classification method that better reflects the structural characteristics of the incinerator is to divide it into three types: liquid waste incinerators, gas waste incinerators and solid waste incinerators according to the form of the waste processed. There are many types of solid waste incinerators, including three main types: grate-type incinerators, hearth-type incinerators and boiling fluidized-bed incinerators. However, each type of furnace has different types depending on its specific structure, and is divided into the following types: Grate-type incinerator A furnace that places waste on the grate for incineration is called a grate-type incinerator. (a) Fixed grate incinerator Fixed grate incinerators can only be operated manually, operate intermittently, have poor working conditions, low efficiency, and incomplete incineration due to insufficient material allocation. (b) Movable grate incinerator Movable grate incinerator is the mechanical grate incinerator. The grate is the heart of the movable grate incinerator. Its performance directly affects the incineration treatment effect of garbage and can make the incineration operation automated and continuous. According to the different grate structures, it can be divided into chain type, stepped reciprocating type, multi-stage rolling incinerator, etc. Most of the small and medium-sized garbage incinerators currently manufactured in our country are chain furnaces and stepped reciprocating grate incinerators, which have poor functions. Most mechanical grates with better functions are patented grates. Hearth-type incinerator Hearth-type incinerators use a hearth to hold materials, and combustion occurs on the surface of the materials on the hearth. They are suitable for processing small or powdery solid waste and slurry waste. They are divided into two categories: fixed hearth and movable hearth. (a) Fixed hearth incinerator The simplest hearth type incinerator is a horizontal fixed hearth incinerator. The hearth and the combustion chamber form an integral body. The hearth is horizontal or slightly tilted, and the combustion chamber and the hearth are integrated. The feeding, stirring and ash removal of waste are all manual operations. The labor conditions are poor and it is an intermittent operation, so it is not suitable for the treatment of large amounts of waste. The hearth of the tilted fixed hearth incinerator is tilted, which facilitates feeding and ash removal, and allows the materials on the tilted bed to burn while sliding down, which improves the incineration conditions. Like the horizontal hearth, the combustion chamber of this type of incinerator is integrated with the hearth. The feeding and discharging operations of this type of incinerator are basically intermittent. However, if the solid waste has very little ash after incineration, and is equipped with a larger ash storage pit, or has a continuous ash extractor and continuous feeding device, the incineration operation can also be made a continuous operation. (b) Movable bed incinerator The hearth of the movable bed incinerator is movable, allowing waste to be loosened and moved on the hearth to improve incineration conditions and perform automatic feeding and ash removal operations. This type of incinerator has three types: rotary hearth, tunnel rotary hearth and rotary hearth (i.e. rotary kiln). The most commonly used is the rotary kiln incinerator. (c) Fluidized bed incinerator This is a high-efficiency incinerator developed in recent years. The hot air blown from the distribution plate at the bottom of the furnace is used to suspend the waste in a boiling state for combustion. Generally, an intermediate medium, that is, a carrier (sand) is used for fluidization, and then the waste is added to the fluidized bed to contact the high-temperature sand to transfer heat for combustion. It is classified according to the presence or absence of the fluidizing medium (carrier) and the fluidization state. 3. Multi-chamber incinerator A multi-chamber incinerator is an incinerator with multiple combustion chambers, which can divide the combustion process of waste into two steps: first, the primary combustion (or solid combustion) process of the waste in the ignition chamber, followed by the secondary combustion (or gas phase combustion) process. The secondary combustion area consists of two parts, one is the downward flue (or mixing chamber), and the other is the upward expansion chamber (or combustion chamber). There are two basic types of structures of modern multi-chamber incinerators, which are named according to their different layouts: one is that the chambers through which the gas returns flow are arranged in a "U" shape, which is called the labyrinth type; the other is that the chambers are arranged in a straight line, which is called the series type. (a) A typical labyrinth multi-chamber incinerator is shown in the left figure. It has multiple baffles inside and is compact in structure. The position of the baffles allows the combustion gas to make a 90-degree turning movement in the horizontal and vertical directions. Every time the direction of the flue gas flow changes, dust falls out of the flue gas flow. The position of the grate in the first combustion chamber is higher, and the ash pit for collecting ash is deeper. The primary air and the secondary air enter the furnace from the bottom and top of the primary combustion chamber grate respectively through the blower with a controlled air volume. The auxiliary fuel gas enters the secondary combustion chamber through the flame port, or enters a smaller mixing chamber in front of the secondary combustion chamber. The flame port is actually a hole above the crossover wall that separates the primary combustion chamber and the secondary combustion chamber. When there is a mixing chamber, the secondary combustion chamber is equipped with a separate air inlet. Both the first combustion chamber and the second combustion chamber are equipped with burners, and auxiliary fuel can be added. If the furnace temperature can be increased to a level that maintains the continuous spontaneous combustion of the waste after the waste is ignited, the first combustion chamber no longer needs to add auxiliary fuel. The second combustion chamber usually needs to continuously add auxiliary fuel. The first combustion chamber is a solid waste combustion chamber, and the second combustion chamber is a gas phase combustion chamber. From the first combustion chamber to the second combustion chamber, it needs to pass through the flame port and the mixing chamber to form a combustion zone. The waste enters the first combustion chamber, is thrown on the fixed grate, is dried, ignites and burns. During combustion, volatile matter and water evaporate and are partially oxidized through the combustion chamber. The rest flows downward through the mixing chamber and secondary air with the air flow through the flame port. Mixing, because the mixing chamber restricts the airflow area and suddenly changes the flow direction, resulting in turbulence, which promotes uniform mixing and produces gas phase reactions. The expanding gas is blocked by the curtain wall, causing the airflow to change direction. It passes through the curtain wall opening from the mixing chamber to the final combustion chamber, and the combustible components are oxidized in the coaxial multi-chamber. Fly ash and other solid particulate matter are collided with the wall and settle in the combustion chamber. Therefore, the concentration of particulate matter in the flue gas discharged from this type of incinerator is relatively low. In many cases, it can meet emission standards even without other air pollution control equipment. The characteristic of multi-chamber incinerator is that it is suitable for the incineration of solid waste with high volatile content using small amounts and multiple intermittent additions, and its applicable range is 10kg/h ~ 375kg/h. (b) Coaxial multi-chamber incinerator This type of incinerator is larger than the labyrinth multi-chamber incinerator. The combustion air enters the incinerator directly, and the moving air flow only changes in the vertical direction. Same as the retort-neck multi-chamber incinerator, the flow direction of the air flow changes and collides in this type of incinerator, so that fly ash and other solid particulate matter are mixed evenly with the flue gas in the secondary combustion chamber, and can be burned more effectively. Incinerators with a processing capacity greater than 500kg/h are usually equipped with automatic continuous feeding and ash removal equipment. The grates can be fixed or movable mechanical grates. (c) Characteristics and practicality of multi-chamber incinerators The basic characteristics of the labyrinth multi-chamber incinerator are: The layout of the combustion chamber allows the combustion airflow to turn through multiple 90° bends in both horizontal and vertical directions. The return flow of the gas allows the sharing of walls between the primary and secondary combustion stages. The aspect ratio of the mixing chamber, flame port and partition wall port is 1:1 to 2.4:1. The thickness of the fire retaining wall under the flame port is a function of the size of the mixing chamber and combustion chamber; this makes it slightly bulky when building an incinerator above 250kg/h. The basic characteristics of the series coaxial multi-chamber incinerator are: (1) The combustion gas flows directly through the incinerator, only making a few 90° turns in the vertical direction. (2) Due to operation, maintenance or other reasons, it is required to separate the spaces of each chamber from each other. This series layout is simple to install. (3) All openings and chambers can be widened to the same width as the incinerator. The length-to-width ratio of the flame port, mixing chamber and partition wall port channel section is 2:1 to 5:1. Multi-combustion chamber incinerators are limited in operation and application due to their inherent structural characteristics. (1) The ratio of the flame port and the mixing chamber determines the appropriate range of gas velocity. (2) Appropriate flame distribution must be maintained throughout the flame port and the mixing chamber, (3) The flame must enter the combustion chamber through the mixing chamber. This is the basic factor causing the difference in operating performance of the two incinerators. The combustion air requirement is the same for both types of incinerators, approximately 300% excess air. About half of the required combustion air enters the incinerator due to leaks in the charging door and other parts of the incinerator. The remaining required air is distributed as follows: 70% is secondary air entering the first combustion chamber from the grate, 10% is primary air entering under the grate, and 20% enters the mixing chamber or secondary combustion chamber. Multi-chamber incinerators are generally used to process solid waste. For flowable materials, such as sludge, liquids and gases, they can be incinerated in multi-chamber incinerators only if suitable combustion nozzles are used. Multi-chamber incinerators are usually fed intermittently, and push rod type feeding systems are conventionally used. For waste materials containing highly volatile substances, frequent small batch intermittent feeding is required. 4. Mechanical grate incinerator. The mechanical grate incinerator uses a movable grate, which can make the incineration operation continuous and automated. It is currently the most widely used incinerator in processing municipal waste. Its typical structure is shown in the figure on the right: There is a series of mechanical grates placed in the combustion chamber of the incinerator, which are usually divided into drying section, combustion section and post-combustion section according to their functions. After the garbage enters the mechanical grate incinerator through the feeding device, it is gradually introduced to the grate in the combustion chamber under the reciprocating motion of the mechanical grate. The garbage is transported by the combustion-supporting air sent from below the grate and the mechanism of grate movement. Under the combined force of pushing and rolling, the water continues to evaporate during the forward movement. Usually the garbage is completely dried and begins to ignite when it is dropped to the horizontal combustion grate. The selection principle of the combustion grate movement speed should ensure that the garbage is completely burned into ash when it reaches the end of the grate. The ash falling from the post-combustion section grate enters the ash hopper. The generated waste gas flow rises and enters the secondary combustion chamber, and is fully stirred with the combustion air introduced from above the grate. After mixing and complete combustion, the waste gas is introduced into the waste heat recovery boiler above the combustion chamber for heat exchange. There is no obvious boundary between the primary combustion chamber and the secondary combustion chamber of the mechanical grate incinerator. The residence time of the waste gas flow generated by garbage combustion in the secondary combustion chamber refers to the residence time of the flue gas from the last air nozzle or burner outlet to the heat exchange surface. 4.1 Functions that the combustion chamber and grate should have The combustion chamber and mechanical grate of the incinerator are the heart of the mechanical grate incinerator. The geometry of the combustion chamber (i.e., the air flow pattern) and the structure and performance of the grate determine the performance of the incinerator and the effect of waste incineration. In order to ensure the efficiency of waste incineration, the conditions and functions that the combustion chamber should have are: There is an appropriate grate area. If the grate area is too small, the thickness of the fire layer will increase, hindering ventilation, and causing incomplete combustion. The shape and airflow pattern of the combustion chamber must be suitable for the type of garbage and the combustion method. Provide an appropriate combustion temperature and provide enough space for drying, burning and post-combustion of the garbage in the furnace body, so that the garbage and combustible gases have sufficient residence time for complete combustion. There is an appropriate design to facilitate full contact between garbage and air, so that the burned exhaust gas can be mixed and stirred evenly. The structure and materials should be resistant to high temperatures and corrosion (such as using water walls or air-cooled brick walls), and can prevent the leakage of air or exhaust gas. It is equipped with a burner, which is placed on the left and right side walls above the grate and above the end of the grate for use when starting up or heating. In order to ensure that the garbage is fully and quickly burned, the garbage needs to have good moving and stirring functions on the grate. The functions that each section of the grate should have are listed in the table on the right. 4.2 Grate Types and Structures There are many types of mechanical grates, including chain type, stepped reciprocating type, multi-section rolling type and open-shaped grate. However, except for chain type and stepped reciprocating type, other grates are patented grates. (1) Chain grate The chain grate has a simple structure and does not stir or turn the garbage. The garbage is only disturbed when it falls from one grate to the next. It is easy to cause partial garbage to be burned through and partial garbage to be unburned. This phenomenon is particularly prominent for large incinerators. In addition, chain grates are not suitable for incineration of wastes containing a large amount of granular waste and waste plastics. Therefore, chain grates are rarely used in foreign incineration plants. However, some small and medium-sized garbage incinerators in my country still use this grate. (2) The stepped reciprocating grate is divided into fixed and movable grates. Fixed and movable grates are placed alternately. The reciprocating motion of the movable grate is driven by a hydraulic cylinder or mechanically. The frequency of the reciprocating grate can be adjusted within a wide range according to the production capacity, and the operation and control are convenient. The reciprocating motion of the stepped reciprocating grate can flip and loosen the material layer, allowing the combustion air to fully contact it, and its performance is better than the chain grate. The stepped reciprocating grate incinerator has strong adaptability to waste treatment and can be used for the incineration of garbage with high water content and solid waste mainly in the form of surface combustion and decomposition combustion, but it is not suitable for low-melting point waste such as fine particles and plastics. (3) Reverse-action incinerator (Martin furnace) The length of the grate is fixed, and the width is adjusted according to the required area of the hearth. It can be composed of several hearths combined horizontally. Each hearth contains 13 fixed and movable step grate bars. The fixed grate bars and movable grate bars are arranged in a transverse staggered manner. The hearth is an inclined bed surface with an inclination of 26. The drying, combustion and post-combustion of garbage are all carried out in this hearth. The primary air is blown from the bottom of the hearth through the air grooves of the grate from both sides of the grate. The movable grate is composed of connecting rods and cross beams and is driven by a hydraulic transmission device. Its moving speed can be adjusted to match various combustion conditions. The way of stirring garbage is as shown in (b), (c), (d) As shown, the movable grate bar moves in reverse direction, causing the garbage to slide down due to gravity, so that the garbage layer is well mixed, and finally the ash is transferred to the ash discharge trough through the ash roller. (4) The rotating barrel-type incinerator grate consists of 5 to 7 barrel-shaped rollers, arranged in an inclined manner. The rotation direction of each barrel is opposite. There is an independent primary air duct, which reaches the garbage layer from the bottom of the barrel through the air supply hole on the surface of the roller. Garbage. The garbage moves downward due to the rolling of the barrel, and can be fully mixed and mixed. The barrel is driven by electricity, and its rotation speed can be adjusted according to the nature of the garbage. This type of grate has a good cooling effect, but the air supply port of the barrel is easy to block, and the blockage can easily cause air lock. (5) Stage-repeated rocking incinerator Each grate of the stage-repeated rocking incinerator has fixed grates and movable grates arranged in a vertical staggered manner. The movable grates are composed of connecting rods and ratchets. They move repeatedly in the horizontal direction on the movable grate support. This movement method exerts shear force on the front, rear, left and right directions of the garbage layer, so that the garbage layer can be loosened and evenly mixed, and fully contacted with the air above the fire. The primary air is blown out from the bottom of the grate through the gaps on both sides of the grate. The grate on the fixed grate in the combustion area has a cutting blade device. Its function is to loosen the garbage blocks, the garbage layer and adjust the garbage residence time, so that the supplied air is evenly distributed, and the secondary air channel has a self-cleaning effect, so that the garbage is repeatedly stirred and moved. (6) Counter-motion flipping grate The structure of the Swiss W+E counter-motion flipping grate is shown in the figure (a) on the right. The grate contains fixed grate bars and movable grate bars. Each fixed grate bar and movable grate bar are arranged in a transverse staggered manner. The grate is set horizontally with no inclination angle or stage difference. The drying, combustion and post-combustion of garbage are all carried out on this grate. The primary air is divided into several pipes from the bottom of the grate, enters the grate, and is blown out from both sides of the grate. The movable grate is composed of a connecting rod crank mechanism and is driven by a hydraulic transmission device. Its movement mode is as shown in Figure (b). The movable grate bars on both sides of the fixed grate make repeated movements in opposite directions, allowing the garbage to stir during advancement and rotation. Because this type of grate is a horizontal device, the required height of the incinerator can be relatively reduced. (7) Mechanical repeated shaking incinerator. This type of grate structure includes a drying grate, a combustion grate, and a rotary kiln grate. However, the rotary kiln grate depends on the actual situation to decide whether it needs to be installed. The mechanical grate is a tilted bed, in which the fixed grate and the movable grate are arranged in a longitudinal staggered manner with staged heights. The movable grate is composed of a grate assembly and a movable bracket and is driven by a hydraulic device. .The primary air is blown out from the bottom of the grate through both sides of the flake grate in the drying zone, and from the front end and surface pores of the plate grate in the combustion zone. The advantage of the plate grate is that the air for combustion can be evenly distributed, the grate cooling effect is good, and the burning of the grate can be avoided. The movable grate in the combustion zone moves repeatedly in the front and back direction, causing the garbage to move, cut, and pass through the stage gap to achieve the effect of stirring and mixing. The garbage that passes through the combustion grate can be post-combusted through an additional rotary kiln downstream. The rotary kiln is constructed as a steel cylinder, and the interior is constructed of refractory materials. The kiln body is slightly tilted. Primary air is blown from the front of the kiln body. There is an airtight device at the kiln body outlet to isolate external gas intrusion. Rollers are installed under the drum. Electric power is used during operation. The roller is driven to rotate the barrel kiln body. There is usually a burner on the furnace wall facing the direction of the exhaust gas outlet at the end of the kiln, which can heat the garbage in the kiln. There is also usually a burner on the refractory brick walls on the left and right sides of the combustion grate. The garbage passes through the post-combustion stage, and finally the ash is discharged by gravity and rolling. (8) Staged reciprocating rocking incinerator Japanese Takuma staged reciprocating rocking grate drying, combustion and post-combustion grates are all inclined bed grates, fixed grates and movable grates are arranged vertically in a staggered manner. High-pressure and high-speed primary air is sent to the bottom of the grate from the air duct at the bottom of the furnace, and then blown out by the air nozzles on both sides of the box-shaped grate, as shown in Figure (a). The movable grate is composed of a grate bracket and a connecting rod crank mechanism, and is driven by a hydraulic transmission device. As shown in Figure (b), the movable grate of each grate moves back and forth horizontally, causing the garbage to slide down due to gravity, and the garbage is cut off, and the garbage is mixed and stirred through stage differences. The force required to move the garbage is proportional to the weight of the garbage and the friction coefficient of the grate. The larger the inclination angle of the grate, the smaller the moving force required for the garbage, and the smaller the reaction force of the garbage on the grate. (9) Reverse-folding movable grate furnace French Stein's reverse-folding movable grate has an inclined bed surface with no stage difference. The primary air is blown out from the bottom of the grate through both sides of the grate. The movable grate is divided into two parts, the front and rear, which are composed of connecting rods and movable frames respectively, and are driven by a hydraulic transmission device Drive, due to the reverse and repeated movement of the movable grate, the garbage falls due to gravity, so that the garbage layer achieves good mixing and mixing. The ash is controlled by adjusting the blades and then moved to the ash discharge trough. The mechanical design of this type of grate is very similar to the German Martin grate. (10) Seghers multi-stage grate. The Belgian Seghers grate is a stepped grate, which is a combination of fixed grate bars, sliding grate bars and flipping grate bars, and can be controlled individually. The Seghers grate is composed of the same standard components, and each component includes a rigid beam group. The lower structure is composed of cast steel supports for each grate bar and steel grate bars covered with refractory materials. Each standard grate element has six rows of grate bars, which are arranged in two sets of three different grate bars: fixed, horizontal sliding and flipping. The lower frame of the lower mechanism directly supports the fixed grate bars. The top surface of all grate bars forms a grate inclined plane with an angle of 21°, and all components are arranged in this manner. Sliding the grate bars pushes the garbage layer to move toward the end of the grate, while turning the grate bars makes the garbage puff and fill with air. The combustion air under the grate leaves the grate after passing through several cooling fins and openings and grooves at the front end of each grate piece, and blows through the top of the next grate piece. Each grate piece has a combustion air outlet opening, thereby ensuring air distribution on the entire grate surface. The structure of the combustion chamber. There are steel pillars on both sides of the furnace body, and beams are set on the sides to support the grate and furnace wall. Combustion chambers in waste incineration plants can be divided into refractory combustion chambers and water-cooled combustion chambers according to different heat absorption methods. Refractory combustion chambers are only insulated by refractory materials. , all heat is absorbed by the boiler heat transfer surface located in the convection zone. This type was only used in earlier incinerators. The water-cooled combustion chamber is integrated with the hearth, and water pipe walls are used around the combustion chamber to absorb the radiant heat generated by combustion, which is used in modern large-scale garbage incinerators. The furnace wall is a refractory brick wall that can withstand high temperatures. The maximum temperature of the combustion flame is about 1000°C or above. The outside of the refractory brick wall must have sufficient thickness of thermal insulation materials and shells to make the furnace wall airtight and avoid leakage of high-temperature gases. Most of the top of the furnace body is It is a water wall structure. Its purpose is to absorb the high-temperature radiant heat of the combustion chamber and protect the furnace wall. It can also increase the heat transfer area of the boiler and increase the steam production of the boiler. The structure of the furnace wall is divided into four types: brick wall, unshaped refractory brick wall, air-cooled brick wall, and water wall. (a) Due to the high furnace temperature of the brick wall, the incinerated materials and combustion products, such as alkaline melts, are corrosive to the furnace lining. Generally, high-aluminum refractory materials with higher alumina content, and chromium-magnesite, magnesite and aluminum-magnesite refractory materials that are resistant to alkaline corrosion are used. (b) Air-cooled brick walls and water-cooled walls add a plate heat exchanger on the outside of the brick wall, using the combustion heat source in the furnace to exchange heat with the combustion-supporting cold air before entering the furnace, which not only reduces the temperature of the furnace wall, but also recovers waste heat. By lowering the temperature of the furnace body, it avoids the attachment of slag to the furnace wall and inhibits the generation of nitrogen oxides, which is beneficial to combustion. 5. Gas-controlled incinerator The gas-controlled incinerator consists of a primary combustion chamber and a secondary combustion chamber, which are burned in two stages. During the operation, the amount of air entering the primary combustion chamber and the secondary combustion chamber is strictly controlled. The amount of combustion air introduced into the first combustion chamber is generally 70-80% of the theoretical combustion air amount. Combustion under oxygen-depleted conditions contains flammable substances. The components of the cracked gas are burned in the secondary combustion chamber. The design of the secondary combustion chamber provides sufficient residence time for the complete removal of organic matter in the cracked gas. Like the same combustion chamber, a strictly controlled amount of gas is introduced into the secondary combustion chamber. However, in the case of oxygen enrichment, 140-200% of the ideal ratio of gas is introduced to maintain complete combustion. Compared with other incineration methods, the amount of gas used to burn waste in the first combustion chamber is small and the speed is low. The low speed of the gas and the almost non-turbulent flow of the waste make the air flow carry away a small amount of particulate matter. Complete combustion is completed in the second combustion chamber, and the generated exhaust gas is clean and contains almost no particulate matter, such as smoke and soot. It usually meets the exhaust standards without using additional air purification devices, such as scrubbers or bag filters. In the first combustion chamber where the air supply volume is less than the oxygen demand for complete oxidation, its operation control is as follows: reduce the air intake volume when the temperature rises; increase the air intake volume when the temperature decreases. The second combustion chamber is designed for complete incineration, and its air supply volume is more than the ideal air supply volume. In the ideal configuration Under the condition of ratio, combustible substances will be completely burned. Excessive gas will extinguish the cracked gas, that is to say, it will reduce the temperature of the exhaust gas. Therefore, the operation control of the secondary combustion chamber is as follows: when the temperature increases, the air intake volume increases; when the temperature decreases, the air intake volume decreases. (1) Modular CAO Modular fixed-bed incinerator is first cast in the factory and then transported to the site for assembly. The incinerator consists of two cylindrical combustion chambers made of carbon steel covered with refractory bricks. It usually does not have an expensive and complicated air pollution control system, and only controls particulate pollutants. The main combustion chamber is in the shape of a staircase, with a conveyor rod installed between each step, which is pushed forward every 7 to 8 minutes to facilitate the movement of waste and ash. Each combustion chamber is equipped with at least one auxiliary burner to maintain the temperature in the furnace. In order to avoid the leakage of incomplete combustion gases, the pressure inside the furnace is slightly lower than outside the furnace. An air duct is installed at the bottom of the main combustion chamber to absorb air outside the furnace. The air supply volume in the first combustion chamber is small and the temperature is around 700°C, which can pyrolyze raw garbage and prevent excessive air volume from bringing a large number of incompletely burned suspended particles into the second combustion chamber; in the second combustion chamber, auxiliary fuel and excess combustion air are used to raise the combustion temperature to above 1000°C to completely oxidize the incompletely burned hydrocarbons. The temperature (or combustion rate) in the main combustion chamber changes cyclically, but sequential control of the movement of the feed rod and conveyor rod can reduce the temperature range. In addition, injecting water vapor into the main combustion chamber can also adjust the temperature changes and reduce the production of carbon monoxide. Due to the fluctuation of temperature, the refractory bricks in the furnace often withstand thermal shock, and the refractory materials must be repaired frequently. The air-controlled modular incinerator has better combustion conditions than the anoxic type, and can automatically and continuously feed and discharge ash. Waste heat can also be recovered to generate steam and hot water. It has become the main small waste incinerator and is generally used in general schools, institutions, hospitals, factories and small towns. It is suitable for the treatment of waste paper, municipal garbage and medical waste. It can also be used to incinerate other general solid, liquid and sludge waste, but is not very suitable for hazardous waste incineration. The advantages and disadvantages of this incinerator are shown in the table below: (2) Spiral incinerator The spiral incinerator was developed by Boeing Engineering and Construction Company in Seattle, Washington. The first combustion chamber includes the shell of the cylindrical combustion chamber, the feeding device, the discharging device, the forced ventilation system, the ash collector and the unequal pitch propeller. There is a non-equidistant spiral in the primary combustion chamber that pushes the waste to move in the primary combustion chamber. The crushed waste (90% is required to be less than 20cm) enters the combustion chamber at a certain controlled speed and is pushed into a pile by the first spiral blade of the propeller. The waste is then pushed by the spiral and rolls through the combustion chamber. When the waste is moved by the spiral, it also serves to stir the material. function, thereby maximizing the contact of the waste material with the air injected into the combustion chamber. When the material is burned and the volume is reduced, the spiral pitch that promotes the movement of the material is also reduced accordingly. The stirring effect of the waste bed combined with the accurate control of the injected air allows the first combustion chamber to operate at a uniform medium temperature, and the waste is close to gasification without complete combustion. The exhaust gas from the combustion chamber passes upward through the heat pipe and then downwards into the after-combustion chamber for complete combustion. The cyclonic airflow in the after-combustion chamber can also separate and remove most of the particles taken away from the combustion chamber. The air injected into the after-combustion chamber can control the temperature of the exhaust gas from the after-combustion chamber to a safe level below the minimum temperature for initial softening of the ash. Both the combustion chamber and the post-combustion chamber are cooled by preheated air, that is, the air injected into each device first passes through the heat exchange structure of the device before being injected, preheating the air and cooling the device at the same time. This reduces heat loss and improves operating performance. (3) Slag high-temperature gasification incinerator This type of incinerator, also known as ANDCO-TORRAX pyrolysis incinerator, is a vertical incinerator composed of a gas generator and a subsequent secondary combustion chamber, as shown in the picture on the right. The garbage falls into the gas generator by gravity and passes from top to bottom through the drying zone, pyrolysis zone and combustion/melting zone; the preheated air is blown into the bottom of the gas generator, and its temperature is about 1038°C. It burns the remaining charcoal after pyrolysis, and the heat generated melts the inert substances to pyrolyze the falling garbage. The molten slag produced at high temperature is at the bottom of the furnace (temperature reaches 1650°C), continuously flows out from the slag outlet, and falls into the water smelting tank to form black inert granular materials. The volume of the residue is about 3% of the volume of the garbage loaded into the gas generator. The pyrolysis gas temperature of the gas generator is between 427 and 538°C, and the calorific value is low, ranging from 3730 to 5595 kJ/m3. It enters the secondary combustion chamber from the tangential direction, where it is fully burned with air to produce exhaust gas with a temperature of 1205~1260°C. About 15% of the hot gas in the secondary combustion chamber is introduced into a heat exchanger equipped with refractory materials, where the primary combustion air is heated to 1038°C and then sent to the gas generator. The remaining 85% of the hot gas in the secondary combustion chamber is sent to the waste heat boiler to produce steam. The exhaust gas is generally purified by a conventional electrostatic precipitator. (4) Multi-layer furnace The structure of a multi-layer furnace is as shown in the picture on the left. The furnace body is a vertical steel cylinder lined with refractory materials. The interior is divided into many layers, each layer is a furnace. The center of the furnace body is equipped with a double-cylinder hollow central shaft with a stirring arm that rotates clockwise. The inner and outer cylinders of the stirring arm are respectively connected to the inner and outer cylinders of the central axis. The stirring arm is equipped with stirring teeth in multiple directions that match the position of the blanking port of each layer. The multi-layer bed incinerator can be divided into three areas from top to bottom: drying area, combustion area and cooling area. The upper layers of the furnace are drying areas, with an average temperature between 430°C and 540°C. The main function is to evaporate the moisture contained in the waste. The filter cake coming in from the feeding port contacts the high-temperature combustion exhaust gas and is dried. The viscosity of the initially added filter cake is relatively high, and the rake teeth stir and break it on the one hand to increase the surface and increase the drying speed. The combustion reaction mainly occurs It is generated in the middle layers of high temperature (760~980℃). Since the waste stays in the furnace for a long time, it is almost completely burned. The burned ash enters the lower cooling zone (150~300℃) to exchange heat with the incoming cold air, and is cooled to 150℃ and discharged out of the furnace. If auxiliary fuel is required, the excess air rate is 50~60% to reduce the heat taken away by the excess air. Some designs also include a secondary burner to ensure complete combustion of volatile organic vapors. (5) Rotary kiln incinerator The rotary kiln is a slightly inclined steel hollow cylinder lined with refractory bricks. The kiln body is usually very long. Most waste materials are heated by the gas generated during the combustion process and the heat transmitted by the kiln wall. Solid waste can be fed into the kiln from the front end for incineration and rotated at a constant speed to achieve the purpose of mixing the waste. .An appropriate inclination must be maintained during rotation to facilitate the sliding of solid waste. In addition, waste liquid and waste gas can be fed from the front, middle and rear sections simultaneously with combustion air. Even whole barrels of waste (such as sludge) can also be fed into the rotary kiln incinerator for combustion. However, this multi-purpose rotary kiln incinerator is more complicated in material preparation and feeding. There are two types of rotary kiln incinerators: basic type rotary kiln incinerator and rear rotary kiln incinerator. The basic type rotary kiln incinerator is shown in the figure below. The system consists of a rotary kiln and a secondary combustion chamber. When the solid waste moves to the lower part of the kiln, the organic matter in it is destroyed. Liquid and gaseous wastes and commercial fuels are used as auxiliary fuels in both the rotary kiln and the secondary combustion chamber. The post-rotary kiln incinerator is shown in the figure below. This type of rotary kiln can be used to process large volumes of solid waste with any liquid entrained. In the drying zone, water and volatile organic compounds are evaporated. The evaporated materials then bypass the rotary kiln and are sent to the secondary combustion chamber. The solid materials are ignited when passing through the combustion grate before entering the rotary kiln. Liquid and gaseous waste are sent to the rotary kiln or secondary combustion chamber. There are two directions in which gas and solid flow in the rotary kiln: the same direction and the reverse direction. The reverse type can provide better mixing and contact of gas and solid, which can increase the combustion rate and have high heat transfer efficiency. However, due to the large relative speed of gas and solid, the amount of dust taken away by the exhaust is also high. Under the same direction operation, the phased phenomena of drying, volatilization, combustion and post-combustion are very Obviously, the temperature of the exhaust gas and the temperature of the combustion residual ash tend to be close to each other at the end of the rotary kiln. However, most of the current rotary kiln incinerators are co-directional. The main reason is that the co-directional furnace design is not only suitable for the input and pre-treatment of solid waste, but also can increase the residence time of the gas. The reverse rotary kiln is more suitable for sludge with high humidity and low flammability. The rotary kiln incinerator is a multi-purpose incinerator with strong adaptability and can incinerate a variety of liquid and solid wastes. In addition to non-combustible materials with high content of heavy metals, water or inorganic compounds, combustible wastes in various states (solid, liquid, sludge, etc.) and shapes (granules, powders, blocks and barrels) can be sent to the rotary kiln for incineration. The general advantages and disadvantages of rotary kiln incinerators are analyzed in the table below. (6) Fluidized bed incinerator The combustion principle of a fluidized bed incinerator is to achieve complete combustion through the uniform heat transfer and heat storage effect of the sand medium. Since the pores provided between the media are narrow and cannot accommodate larger particles, if solid waste is processed, it must be broken into small particles first to facilitate the reaction. Combustion air is mostly sent from the bottom, and the furnace can be divided into a grid area, a bubble area, a bed surface area and a freeboard area. The upward airflow velocity controls the degree of fluidization of particles. When the airflow velocity is too high, the medium will be brought into the air pollution control system by the rising airflow. An external cyclone dust collector can be installed to capture the medium particles with large particles and return them to the furnace. Air pollution The control system usually only needs to install an electrostatic dust collector or a filter bag dust collector to remove suspended particles. Add some lime powder or other alkaline substances to the feed inlet, and the acid gas can be directly removed in the fluidized bed, which is another advantage of the fluidized bed. New incinerator (Japan) EBARA: Non-breaking fluidized bed incinerator Mitsubishi: MARTIN grate incinerator (7) Liquid jet incinerator The liquid jet incinerator is the most common liquid hazardous waste incinerator. All liquid waste liquids, mud and sludge can be destroyed with it. The first chamber usually has A combustion nozzle is used to burn the input flammable liquid and gaseous waste. Non-combustible liquid and gaseous waste often do not pass through the combustion nozzle and enter the second chamber from the rear. The figure below shows a schematic diagram of a two-stage system. A single-stage incineration system can only be used to treat combustible waste. The structure of the waste incinerator is determined by the type and nature of the waste liquid and the type of waste liquid nozzle used. Furnace types include vertical cylindrical furnaces, horizontal cylindrical furnaces, box furnaces, rotary kilns, etc. The layout of the liquid jet incinerator can be horizontal, vertical upward burning, vertical downward burning or inclined. Which layout is usually decided based on the characteristics of the waste. The liquid jet incinerator does not contain moving parts, and the maintenance requirements are the least among all types of incinerators. Process application of liquid jet incinerator Liquid incinerator can process any combustible liquid waste and sludge with a viscosity lower than 10,000 SSU. Waste with heavy metals and high moisture content, inorganic brine and inert liquid are not suitable for being sent to this type of furnace for incineration, because combustion cannot remove harmful substances in such waste. Liquid jet incinerators are extremely sensitive to changes in waste composition and flow rate. Therefore, it is necessary to use a reservoir and mixer to ensure the stability and uniformity of the material. The operating temperature range of liquid incinerators is 1000~1650C, and the residence time is 0.5~2s. The requirements for time, temperature and excess air are largely determined by the design of the mixing system, the selected combustion nozzles and the characteristics of the waste. The general rule is that at the same temperature, the time required to apply a short flame combustion nozzle is shorter than that of a long flame combustion nozzle, and the excess air required for complete combustion of waste is also less. The heat released by the combustion chamber of most conventional equipment is approximately 9.3×105 kJ/m3h, but the heat released by the vortex type incinerator is approximately 3.7×106 kJ/m3h. 要确定所需要的工艺设计参数,有必要对废物进行中间规模的试验.通常大规模的液体喷射焚烧炉设备的性能较好,因为设计小型的混合系统更为困难. (8)气体焚烧炉在实际生产中,因废物中常有废液,废气和废渣,所以在可能的情况下,常将废气与其它废物在同一炉内焚烧,而单独焚烧废气的炉子不多.有的则是将经过一次焚烧尚未彻底焚毁的烟气再次焚烧,相当于某焚烧炉的二次燃烧室.例如,多段耙床炉,回转炉等排出的气体再次焚烧就是这种情况. 气体废物焚烧炉相当于一个用气体燃料燃烧的炉子或固体废物焚烧炉的二次燃烧室,用于高温下将废气中有毒,有恶臭的组分焚毁,成为无害无臭的气体.当废气本身所含的可燃有机质较少,不能维持其所要求的燃烧温度时,则应补充辅助燃料. 第五节焚烧炉设计原则及要点1,焚烧炉设计的一般原则废物焚烧炉设计的基本原则,是使废物在炉膛内按规定的焚烧温度和足够的停留时间,达到完全燃烧.这就要求选择适宜的炉床,合理设计炉膛的形状和尺寸,增加废物与氧气接触的机会,使废物在焚烧过程中,水气易于蒸发,加速燃烧,及控制空气及燃烧气体的流速及流向,使气体得以均匀混合. (1)炉型选择在选择炉型时,首先应看所选择炉型的燃烧型态(控气式或过氧燃烧式),是否适合所处理的所有废物的性质.一般来说,过氧燃烧式焚烧炉较适合焚烧不易燃性废物或燃烧性较稳定的废物,如木屑,垃圾,纸类…等,而控气式焚烧炉较适合焚烧易燃性废物,如塑料,橡胶与高分子石化废料等;机械炉排焚烧炉适用于城市垃圾的处理,而旋转窑焚烧炉适宜处理危险废物. 此外,还必须考虑燃烧室结构及气流模式,送风方式,搅拌性能好坏,是否会产生短流或底灰易被扰动等因素. 焚烧炉中气流的走向取决于焚烧炉的类型和废物的特性.其基本的取向如下图所示.多膛式焚烧炉的取向与流化床焚烧炉一样,通常是垂直向上燃烧的,回转窑焚烧炉通常是向斜下方向燃烧,多燃烧室焚烧炉的燃烧方向一般是水平向的,而液体喷射式焚烧炉,废气焚烧炉及及其它圆柱型的焚烧炉可取任意方向,具体形式取决于待焚烧的废物形态及性质.当燃烧产物中含有盐类时,宜采用垂直向下或下斜向燃烧的设计类型,以便于从系统中清除盐分. (2)送风方式选择就单燃烧室焚烧炉而言,助燃空气的送风方式,可分为炉床上送风和炉床下送风两种,一般加入超量空气100～300%,即空气比在2.0～4.0之间. 对于两段式控气焚烧炉,在第一燃烧室内加入70～80%理论空气量,在第二燃烧室内补足空气量至理论空气量的140%至200%.因第一燃烧室中是缺氧燃烧,故增加空气流量会提高燃烧温度;但第二燃烧室中是超氧燃烧,增加空气流量则会降低燃烧温度.二次空气多由两侧喷入,以加速室内空气混合及湍流度.从理论上讲强制通风系统与吸风系统差别很小.吸风系统的优点是可以避免焚烧烟气外漏,但是由于系统中常含有焚烧产生的酸性气体,必须考虑设备的腐蚀问题. (3)炉膛尺寸的确定废物焚烧炉炉膛尺寸主要是由燃烧室允许的容积热强度和废物焚烧时在高温炉膛内所需的停留时间两个因素决定的.通常的做法是按炉膛允许热强度来决定炉膛尺寸,然后按废物焚烧所必须的停留时间加以校核. 考虑到废物焚烧时既要保证燃烧完全,还要保证废物中有害组分在炉内一定的停留时间,因此在选取容积热强度值时要比一般燃料燃烧室低一些. (b)液体废物焚烧炉液体废物焚烧炉炉膛容积一般比液体燃料的燃烧室允许热负荷热小,其值在(92～106)104 kJ/(m3.h)之间.焚烧处理含水量少,热值高的废液时可取较大的值,有资料介绍大值可达(130～170)104 kJ/(m3.h). 关于水分蒸发所需容积,经推算单位时间(1h)焚烧1t含水量为90%的废液,需要8～10.5m3炉膛容积;即使含水量少到50%的废液,也几乎要求同样的容积,最小需5m3.这个要求可用以核算炉膛尺寸. 在确定废液焚烧炉炉膛尺寸时还应考虑喷嘴的喷射角和射程,避免液滴喷到炉子耐火衬里壁上,导致炉衬损坏. (c)废气焚烧炉废气焚烧炉的炉膛基本与气体燃料燃烧室设计相同,燃烧室热负荷值一般可取(80～100)104 kJ/(m3.h),由此可根据可燃废气发热值来确定炉膛容积尺寸. 关于废物焚烧炉炉膛尺寸的大小,即允许容积热强度值的高低,与被焚烧的废物种类,热值,燃烧装置的型式及炉内燃烧工况等因素有关.如果燃烧装置的燃烧效率较高,炉内燃烧温度较高,则可取较高的允许热强度值;反之则取较低值.以上所提供的数值是对一般情况而言,较合宜的数据将根据不同的物料,炉型等因素参照生产实践而定. (4)燃烧装置与炉膛结构选择以液体燃料和气体燃料作为辅助燃料时,由于燃烧速度快,通常可将燃料喷嘴与废物设在同一个燃烧室中.合理地布置燃料喷嘴的位置及废液(废气)喷嘴的位置很重要.应使废液(废气)喷到燃料完全燃烧后的区域中去;如果一次燃烧不能完全,则应设置二次燃烧喷嘴.对于固体废物的焚烧,燃料喷嘴通常对废物起加热作用. 设计燃烧喷嘴时应注意的要点有: 第一燃烧室的燃烧喷嘴主要用于启炉点火与维持炉温,第二燃烧室的燃烧喷嘴则为维持足够温度以破坏未燃尽的污染气体. 燃烧喷嘴的位置及进气的角度必须妥善安排,以达最佳焚烧效率,火焰长度不得超过炉长,避免直接撞击炉壁,造成耐火材料破坏. 应配备点火安全监测系统,避免燃料外泄及在下次点火时发生爆炸. 废物不得堵塞燃烧喷嘴火焰喷出口,造成火焰回火或熄灭. (5)炉衬结构与材料选择炉衬材料要根据炉膛温度的高低选用能承受焚烧温度的耐火材料及隔热材料,并应考虑被焚烧废物及焚烧产物对炉衬的腐蚀性.焚烧碱性废水时,燃烧产物中的碱性熔融物对普通粘土耐火砖腐蚀性很强,因此要选用氧化铝含量较高的高铝耐火材料,或选用抗碱性腐蚀更好的铬镁质,镁质及铝镁质耐火材料.为了抵抗盐碱等介质的渗透和浸蚀,并提高材质的抗渣性,一般应选用气孔率较小的材质. 焚烧炉炉衬结构设计除材料的选用上要考虑承受高温,抵抗腐蚀之外,还要考虑炉衬支托架,锚固件及钢壳钢板材料的耐热性和耐腐蚀性,以及合理的炉衬厚度等问题.应采用整体性,严密性好的耐火材料作炉衬,如采用耐热混凝土,耐火可塑料等,以减少砖缝的窜气.另外炉墙厚度不能过大,炉壁温度设计得较高,以免酸性气体被冷凝下来腐蚀炉壁.然而炉壁温度也不应设计得过高,过高的温度会引起壳板变形,影响环境. (6)废气停留时间与炉温选择废气停留时间与炉温的确定以废物特性而定,处理危险废物或稳定性较高的含有机性氯化物的一般废物时,废气停留时间需延长,炉温应提高.若为易燃性或城市垃圾,则停留时间与炉温在设计方面,可酌量降低. 一般而言,若要使CO充分破坏,停留时间应在0.5s以上(炉温700℃以上).但任何一座焚烧炉不可能充分扰动扩散,不同程度地存在短流现象.而且未燃的碳颗粒部分仍会反应成CO.因此操作时炉温应维持1000℃,而停留时间以1s以上为宜.若炉温升高时,停留时间可以降低,相对地,炉温降低时,停留时间需要加长.应该指出,确定废气停留时间及炉温时,最重要的是应该参照有关法规而定. (7)对废物的适应性虽然焚烧处理的废物常是多种多样的,并非单一形态,但从其焚烧本质而言都是燃烧问题,有可能安排在同一焚烧炉内进行焚烧.对于区域性危险废物焚烧厂,通常要求焚烧炉对焚烧的废物有较大的适应性.旋转窑焚烧炉和流化床允许投入多种形态的废物,有较好的适应性.但是,并非所有废物都可投入同一焚烧炉内焚烧,必须考虑焚烧处理废物的相容性,通过试验确定对废物加以分类. 为便于燃烧后产物的后处理或设置废热锅炉,常将某种废物的一些组分预先分离出来,然后分别焚烧.在不会引起传热面污染的焚烧炉后再设置废热回收设备.总之焚烧炉对废物的适应性问题是个较复杂的问题,要考虑到各种因素,力求技术可靠,经济合理. (8)进料与排灰系统选择焚烧炉进料系统应尽可能保持气密性,焚烧系统大多采用负压操作,若进料系统采用开放式投料或密闭式进料中气密性不佳,冷空气渗入炉内会导致炉温下降,破坏燃烧过程的稳定性,使烟气中CO与粒状物浓度急剧上升. 排灰系统应设有灰渣室,采用自动排灰设备,否则容易造成燃烧过程中累积炉灰随气流的扰动而上扬,增加烟气中粒状物浓度. (9)金属材料腐蚀焚烧烟气中的硫氧化物(SOx)及氯化氢(HCl)等有害气体均对金属材料有腐蚀性,但在不同的废气温度环境中腐蚀程度不同. 高温腐蚀是高温酸性气体(包括SO2,SO3,H2S,HCl…等)长时间与金属材料接触所致;低温腐蚀是酸性气体在露点以下时,与烟气中的水分凝缩成浓度较高的硫酸,亚硫酸,盐酸…等液滴,与金属材料接触所造成的腐蚀. 通常,焚烧烟气的温度,在燃烧室内为800～950℃,流经各辅助设备到烟囱出口时温度降为约150～170℃.各项设备与废气温度及腐蚀区域的关系如下表所示.应考虑焚烧炉金属炉壁,耐火水泥焚烧炉的固定锚钉,排气管线及金属制烟囱等的腐蚀问题. 2,机械炉排焚烧炉2.1 炉膛几何形状及气流模式燃烧室几何形状要与炉排构造协调,在导流废气的过程中,为垃圾提供一个干燥,燃烧及完全燃烧的环境,确保废气能在高温环境中有充分的停留时间,以保证毒性物质分解,还需兼顾锅炉布局及热能回收效率. 对于低热值(低位发热量在2000～4000 kJ/kg)高水分的垃圾,适宜采用逆流式的炉床与燃烧室搭配型态,即指经预热的一次风进入炉床后,与垃圾物流的运动方向相反,燃烧气体与炉体的幅射热利于垃圾受到充分的干燥,德国Martin公司的炉体大部分即设计成此种型式. 对于高热值(低位发热量在5000kJ/kg以上)及低含水量的垃圾,适宜采用顺流式炉床与燃烧室搭配型态,此时垃圾移送方向与助燃空气流向相同,因此燃烧气体对垃圾干燥效果较差. 对于中等发热量(低位发热量在3500～6300 kJ/kg之间)的垃圾,可采用交流式的炉床与燃烧室搭配型态,使垃圾移动方向与燃烧气体流向相交.这种燃烧模式的选择有很大灵活性,若焚烧质佳的垃圾,则垃圾与气体流向的交点偏后向燃烧侧(即成顺流式);反之则偏向干燥炉床侧(即成逆流式),瑞士Von Roll公司的炉体即属此型式. 对于热值四季变化较大的垃圾,则可以采用复流式的搭配型态.在日本亦称为二回流式,燃烧室中间有辐射天井隔开,使燃烧室成为两个烟道,燃烧气体由主烟道进入气体混合室,未燃气体及混合不均的气体由副烟道进入气体混合室,燃烧气体与未燃气体在气体混合室内可再燃烧,使燃烧作用更趋于完全.丹麦Vo1und及其代理厂家日本钢管株式会社(NKK)的炉体即属于此种型式. 欧洲共同体燃烧优化准则(GCP)中规定,焚化废气在燃烧室炉床上方至少须在850℃环境中停留2s,以彻底破坏可能产生二恶英的有机物.此外在工程设计时,为避免废气流量过大对耐火衬产生磨蚀,一般均将燃烧室烟气流速限制在5m/s之下,废气通过对流区的流速不得高于7m/s.燃烧室内废气温度亦不可高于1050℃,以免飞灰因温度过高而粘着于炉壁造成软化及腐蚀,并且易于产生过量的氮氧化物. 2.2 燃烧室的构造垃圾焚化厂燃烧室中,依吸热方式的不同可分为耐火材料型燃烧室与水冷式燃烧室二种.前者燃烧室仅以耐火材料加以被覆隔热,所有热量均由设于对流区的锅炉传热面吸收,仅用于较早期的焚烧炉中.而后者中的燃烧室与炉床成为一体,空冷砖墙及水墙构造不易烧损及受熔融飞灰等损害,所容许的燃烧室负荷较一般砖墙构造高,多为近代大型垃圾焚烧炉燃烧室炉壁设计所采用.水管墙可有效的吸收热量,并降低废气温度,其主要设计准则为: 水管墙应采用薄膜墙设计,以达到良好气密性的要求. 水管墙的底部,即靠近炉床的上方部分,因暴露于极高温度的火焰中而易遭受腐蚀,须覆以耐火材料加以保护. 水管墙位置一般在炉床左右侧耐火砖墙的顶部.靠近炉床的侧壁因直接承受高温环境及熔融飞灰的冲击,不适宜采用裸管水墙或鳍片管水墙,有时在接近炉床的位置采用空冷砖墙或耐火砖墙,直至越过火焰顶端后的燃烧室侧壁再采用各型水墙. 2.3 燃烧室热负荷连续燃烧式焚烧炉燃烧室热负荷设计值约为(34～63)×104 kJ/m3h.若设计不当,对于垃圾燃烧有不良的影响,其值过大时,将导致燃烧气体在炉内停留时间太短,造成不完全燃烧,且炉体的热负荷太高,炉壁易形成熔渣,造成炉壁剥落龟裂,影响燃烧室使用寿命,同时亦影响锅炉操作的效率及稳定性;其值过小时,将使低热值垃圾无法维持适当的燃烧温度,燃烧状况不稳定.应根据垃圾处理量与低位发热量确定适宜的燃烧室热负荷,避免设计值与实际操作值误差过大. 一般而言,大型城市垃圾焚烧炉垃圾处理量为每座至少200t/d 以上,才能达到经济效益规模,其最大垃圾处理变动量宜维持在20%以下.一般城市垃圾焚烧的自燃界限为3400kJ/kg～4200kJ/kg,平均低位发热量达5000kJ/kg以上则不需辅助燃料助燃即可焚烧处理.垃圾热值随季节变化很大,设计时应按年均值考虑.此外,还应综合考虑城市垃圾中的可燃分及低位发热量逐年增加的趋势,选择适宜的设计基准和垃圾热值的变化幅度.如焚烧炉设计热值低于焚烧处理垃圾热值,则会造成焚烧厂不能满负荷运行. 2.4 助燃空气通常助燃空气分二次供给,一次空气由炉床下方送入燃烧室,二次空气由炉床上方燃烧室侧壁送入.一般而言,一次空气占助燃空气总量的60%～70%,预热至150℃左右由鼓风机送入;其余助燃空气当成二次空气.一次空气在炉床干燥段,燃烧段及后燃烧段的分配比例,一般为1 5%,75%及10%.二次空气进入炉内时,以较高的风压从炉床上方吹入燃烧火焰中,扰乱燃烧室内的气流,可使燃烧气体与空气充分接触,增加其混合效果.操作时为配合燃烧室热负荷,防止炉内温度变化剧烈,可调整预热助燃空气的温度.二次空气是否需预热须根据热平衡的条件来决定. 2.5 燃烧室所需体积燃烧室容积(V)大小,应兼顾燃烧室容积热负荷及燃烧效率两种准则,方法是同时考虑垃圾的低位发热量与燃烧室容积热负荷的比值(即Q/Qv),及燃烧烟气产生率与烟气停留时间的乘积(即G* tr), take the larger value of the two. That is: where: V - combustion chamber volume (m3); Q - low calorific value generated by garbage and auxiliary fuel per unit time (kJ/h); Qv - allowable volume heat load of the combustion chamber (kJ/m3h); G - exhaust gas volume flow rate (m3/s); tr - gas residence time (s); - combustion chamber exhaust gas generation rate (kg gas/kg garbage); - Average density of combustion gas (kg/m3); F - garbage disposal rate (kg/h). 2.6 Required grate area When determining the required grate area, the garbage processing volume and its calorific value should be considered at the same time, so that the selected grate area can meet the requirements for complete combustion of garbage. The specific method is to comprehensively consider the ratio of the low-level heat generated by the garbage per unit time to the heat load of the grate area, that is, Q/QR, and the ratio of the garbage processing volume per unit time to the mechanical combustion intensity of the grate, that is, F/Qf. The grate area is determined according to the larger of the two, which is: Where: Q —The low-level heat generated by garbage and auxiliary fuel per unit time (kJ/h); Fb — the required area of the grate (m2); QR = the heat load of the grate area (kJ/m2h); F = the amount of garbage processed per unit time (kg/h); Qf — the mechanical combustion intensity of the grate (kg/m2h). The heat load of the grate area is the heat that the unit grate area can withstand per unit time under normal operating conditions (kJ/m2h). It varies depending on factors such as the grate material and design method. Generally, it is about 1.25106~3.75106kJ/m2h. The mechanical combustion intensity of the grate is the amount of garbage that the grate per unit area can handle per unit time during normal operation (kg/m2h). A high value indicates a strong ability of the grate to handle garbage. According to Japanese research, the factors that affect the mechanical combustion intensity of the hearth include: (1) the low calorific value of the garbage and the air preheating temperature (as shown in Figure a); (2) the thermal ignition loss (as shown in Figure b); and (3) the scale of the incinerator (as shown in Figure c). 3 Due to the large changes in waste types and characteristics of rotary kiln incinerators, the existing combustion model cannot accurately predict the actual combustion conditions. The operation and design of the incinerator must be based on the manufacturer's accumulated experience in the past, and the design methods and criteria tend to be conservative. The general design and operation criteria are as follows: 3.1 Temperature The gas temperature in the dry ash rotary kiln incinerator is usually maintained between 850 and 1000°C. If the temperature is too high, the solids in the kiln are easy to melt, and the temperature is too low, the reaction rate is slow, and the combustion is not easy to complete. The slag type rotary kiln incinerator is controlled above 1200°C, and the temperature of the secondary combustion chamber gas is maintained above 1100°C, but it should not exceed 1400°C to avoid generating a large amount of nitrogen oxides. 3.2 The excess air volume of the waste liquid combustion nozzle of the rotary kiln incinerator is controlled between 10 and 20%. If the excess air volume is too low, the flame will easily produce smoke. If it is too high, the flame will easily be blown out of the nozzle, which may cause the flame to interrupt and spin. The total excess air in the rotary kiln incinerator is usually maintained between 100 and 150% to promote the contact between solid combustibles and oxygen. Some rotary kiln incinerators even inject high concentrations of oxygen. The excess air in the secondary combustion chamber is about 80%. 3.3 Gas and solid mixing in the rotary kiln incinerator. The rotation speed of the rotary kiln incinerator is the main factor that determines the mixing of gas and solid. When the rotation speed increases, the centrifugal force also increases. At the same time, the degree of stirring and throwing of solids in the kiln increases, and the contact surface and opportunities between solids and oxygen also increase. On the contrary, the contact opportunities between the solids in the lower layer and oxygen will be small, and the reaction rate and efficiency will be reduced. Although excessive rotation speed can accelerate the incineration, powdery materials and dust are easily carried by the gas, so the capacity of the exhaust treatment equipment must be increased, and the investment cost will also increase. 3.4 Residence time The volume of the secondary combustion chamber of the rotary kiln incinerator is generally designed based on the gas residence time of 2s. The residence time of solids in the rotary kiln incinerator can be estimated by the following formula: Where: - solid residence time, (min); L - length of the rotary kiln incinerator, (m); D - internal diameter of the kiln, (m); N - rotational speed per minute, (r/min); S - inclination of the kiln, (m/m). The length, rotation speed and inclination of the rotary kiln must cooperate with each other to meet the residence time requirements. Generally speaking, the longer the waste material needs to stay in the kiln, the lower the rotation speed required, and the higher the L/D ratio. The rotation speed of the kiln is usually 1 to 5 r/mi n, the L/D ratio is between 2 and 10, the inclination is about 1 to 2 degrees, the residence time is 30min to 2h, the incineration capacity volumetric heat load is (4.2~104.5) 104kJ/m3h, and the volumetric weight load is 35~60kg/m3h. 3.5 Other considerations Since liquid waste is also destroyed in the rotary kiln incinerator, the form of the liquid burning nozzles, flame characteristics, mutual position of the burning nozzles, nozzle arrangement and mutual interference must also be carefully considered. In order to prevent toxic incomplete combustion gases from escaping from the furnace, both the rotary kiln and the secondary combustion chamber operate under negative pressure (about -0.5kPa). Therefore, the rotary kiln incinerator is required to have a good air tightness to avoid affecting the incineration situation in the kiln. Installing metal or ceramic fiber sheets on the embedded rings at both ends of the kiln can reduce the air intake to less than 10%. An air curtain is formed by compressed air at the connection between the two ends of some rotary kiln incinerators. In addition to reducing air inhalation, it can also cool the metal in the connecting part. This post was last edited by WSL01218 on 2009-2-26 12:34 ]

Our factory also has incinerators for burning waste liquids; we bought them from Japan a few years ago. Japanese products are good, but after their useful life expires – which is around 4 or 5 years – the equipment starts to develop various problems. For example, the ignition detector may fail to detect a flame, preventing ignition, or leaks may start to appear in the shell of the bottom quencher. Everything that can now be produced domestically is being done so. It’s essential to thoroughly study Japanese technology and make it our own; otherwise, Japan’s attempt to make money from spare parts will succeed! This is also a manifestation of patriotism

Hello, our factory is also planning to install a incinerator. I’ve heard that those made in Japan are quite reliable. Could you share some information on them? Thank you\ud83d\ude4f