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The application and development of waste incineration technology abroad have a history of several decades. The more mature types of incinerators include pulse-jet grate incinerators, mechanical grate incinerators, fluidized bed incinerators, rotary incinerators, and CAO incinerators. A brief introduction to these types of incinerators is provided below. Working principle of mechanical grate incinerators: Waste enters through a feed hopper and moves onto an inclined grate that slopes downward; this grate is divided into a drying zone, a combustion zone, and a burnout zone. Due to the interlocking movement of the grates, the waste is pushed downward, passing through each of these zones in sequence (as the waste moves from one zone to another, it undergoes a kind of reversal), until it is completely burned out and discharged from the furnace. The combustion air enters from below the grate and mixes with the waste ； High-temperature flue gas generates hot steam by passing through the heating surfaces of the boiler; at the same time, the flue gas is cooled as well. Finally, the flue gas is discharged after being treated by a flue gas treatment device. Features: High requirements are placed on the material quality and processing precision of the grates; the contact surfaces between the grates must be very smooth, and the gaps between them must be quite small. Additionally, the mechanical structure is complex, the failure rate is high, and maintenance requirements are substantial. The high cost and maintenance expenses of grate furnaces pose significant challenges to their adoption and widespread use in China. Fluidized bed incinerator Working principle: The furnace is composed of porous distribution plates; a large amount of quartz sand is added to the furnace chamber, heated to above 600°C, and hot air at over 200°C is blown in from the bottom of the furnace to cause the hot sand to boil. Then, waste is added to the furnace. The trash boils together with the hot sand, and it is quickly dried, ignited, and burned. Unburned waste is less dense and continues to boil and burn, while burned waste is denser and falls to the bottom of the furnace. After being cooled by water, coarse and fine slag are sent outside the plant using sorting equipment; a small amount of medium-density slag and quartz sand is sent back into the furnace via lifting equipment for further use. Features: Fluidized bed combustion is thorough, and combustion control within the furnace is good; however, there is a high amount of dust in the flue gases, the operation is complex, operating costs are high, there are strict requirements regarding the uniformity of fuel particle size, a high-power crushing device is needed, quartz sand causes severe wear on the equipment, and maintenance requirements are high. Working principle of the rotary incinerator: A rotary incinerator uses cooling water pipes or refractory materials arranged along the furnace body, with the furnace body placed horizontally and at a slight angle. Through the continuous operation of the furnace body, the waste inside is burned completely, while moving in the direction of the furnace’s inclination until it is fully burned out and removed from the furnace. Features: high equipment utilization, low carbon content in ash, low excess air volume, and low emissions of harmful gases. However, combustion is difficult to control, and it is hard to burn when the calorific value of the waste is low. Working principle of the CAO incinerator: Waste is brought to a storage pit and then enters a biochemical treatment tank, where it loses water under the action of microorganisms; as a result, natural organic materials such as kitchen waste, leaves, and grass are broken down into a powdery form. Other solids, including synthetic organic materials like plastics and rubbers, as well as the inorganic substances present in the waste, cannot be broken down into powder. After screening, the waste that cannot be pulverized enters the incinerator first, going into the first combustion chamber (at a temperature of 600°C). The combustible gases generated then proceed to the second combustion chamber, while the non-combustible and non-pyrolyzable components are discharged in the form of ash in the first combustion chamber. The combustion takes place at a temperature of 860°C in the second chamber, with the high-temperature flue gases heating the boiler to produce steam. The treated flue gas is discharged into the atmosphere through a chimney; the metal glass does not oxidize or melt in the first combustion chamber, and can be separated and recovered from the ash. Feature: Useful substances in recyclable waste ； However, each incinerator has a low processing capacity and requires a long processing time; at present, the maximum daily processing capacity of a single furnace is 150 tons. Since the flue gas stays at temperatures above 850°C for no more than 1 second, the dioxin content in the flue gas is high, making it difficult to meet environmental standards. Pulse-jet grate incinerator Working principle: Waste is fed into the dryer bed of the incinerator via an automatic feeding unit for drying, and then sent to the first-grade grate. There, it undergoes high-temperature volatilization and pyrolysis. The grate is moved by pulse aerodynamic devices, which push the waste onto the next grade of grate; at this point, the polymer substances are broken down while other substances burn. This process continues until everything is completely burned out and ends up in the ash pit, from where it is removed by an automatic ash removal system. The combustion air is injected through the pores in the grate and mixes with the waste to burn, simultaneously keeping the waste suspended in the air. The volatilized and cracked substances enter the second combustion chamber, where they undergo further cracking and combustion; the unburned smoke then enters the third combustion chamber for complete combustion ； High-temperature flue gas heats steam by passing through the boiler’s heating surfaces, while the flue gas is discharged after being cooled. Its advantages are: (1) It can handle a wide range of waste types, including industrial waste, household waste, medical waste, and used rubber tires. (2) High heat release efficiency: The normal heat release efficiency is over 80%, and even for household waste with a high moisture content, the heat release efficiency remains above 70%. (3) Low operation and maintenance costs: Thanks to various special designs and a high level of automation, fewer operators are required (only two people are needed per boiler, including those responsible for removing ash and slag), and the amount of maintenance work is also reduced. (4) High reliability: Nearly 20 years of operation have shown that this incinerator has a very low failure rate; it can operate for over 8,000 hours per year, with an average utilization rate of over 95%. (5) High emission control levels: Thanks to the use of secondary flue gas reburning and advanced flue gas treatment equipment, the flue gas is thoroughly treated. After extensive testing, the CO level in the flue gas emissions is 1–10 PPM, the HC level is 2–3 PPM, and the NOx level is 35 PPM, all of which meet the emission standards of Europe and the United States. When the flue gas burns in the second and third combustion chambers, the temperature reaches 1000°C and the residence time is over 2 seconds, which enables the complete decomposition of dioxins; the dioxin content in the flue gas is 0.04 ng/m3, far below the European and American standards of 0.1 ng/m3. (6) The furnace grate has a self-cleaning function under the purge of compressed air.