Waste incineration technology emerged in the late 19th century, and since the 20th century, with the substantial increase in the production of municipal waste and the continuous development of incineration technology, waste incineration has become a waste treatment technology that has been vigorously developed in many countries.
Waste incinerator is the core of waste incineration technology. Early incinerators are manufactured by coal-fired power boiler manufacturers, and are not applicable to the combustion of domestic waste. With the development of waste incineration technology, waste incinerator technology has matured, the world's various types of waste incinerators to more than 200 kinds, but widely used, representative of the waste incinerator technology is mainly four categories, namely, mechanical grate incinerator technology, fluidized bed incinerator technology, rotary kiln incinerator technology and pyrolysis gasification incinerator technology.
At present, China's waste incineration plant construction is suitable for the more mature mechanical grate incinerator. Fluidized bed incinerator technology can also be used in the case of a perfect pretreatment system. Rotary kiln and pyrolysis gasification incinerator technology is less applied, can be used as a supplement to the first two technologies.
Mechanical grate incinerator is the earlier development of waste incinerator type, after a long period of development, the technology has been increasingly perfect, high operational reliability, is currently the leading products in the waste incinerator market.
Mechanical grate incinerator according to the structure of the grate and the movement of different types of different types, but the principle of combustion is more or less the same, the garbage in the grate on the laminar combustion, after drying, combustion, combustion, after the exhaust of the ash discharged from the outside. All kinds of grate will use different ways to make the garbage material layer constantly get loose and make the garbage and air fully contact, so as to achieve a better combustion effect. The combustion air is fed from the bottom of the grate. Depending on the calorific value and moisture of the waste, the air fed into the grate can be hot or cold. At present, the form of mechanical grate incinerator mainly includes downward-pushing grate furnace, reverse-pushing grate furnace, reciprocating tilting grate furnace and rolling grate furnace.
Mechanical grate incinerators have low pretreatment requirements for garbage, a wide range of applicable calorific values for garbage, and easy operation and maintenance. In addition, the single processing capacity of the mechanical furnace is large, especially suitable for large-scale waste centralized treatment.
However, the mechanical structure of the mechanical grate incinerator is more complex, the material requirements of the grate and the processing accuracy of high requirements, the cost and maintenance costs are higher.
Fluidized bed incinerator technology is also a more mature technology, it mainly relies on the high temperature fluidized bed material in the furnace chamber of high heat capacity, strong mixing and heat transfer, so that the garbage sent to the furnace chamber quickly warmed up to fire, the formation of the entire bed within the uniform combustion. Fluidized bed incinerator is the use of fluidization technology for the incineration of garbage, there are a large number of quartz sand in the furnace as a heat carrier, garbage in the furnace suspended combustion.
Fluidized bed incinerator has strict pretreatment requirements for garbage, which must be crushed into smaller particle sizes before it can be incinerated in the furnace, resulting in high energy consumption in the pretreatment process and strict odor control requirements. Fluidized bed incinerator waste and bed material in the fluidized state, serious wear and tear, maintenance is more frequent, the annual operating time is shorter than the mechanical grate furnace.
In addition, due to the current low calorific value of domestic garbage, it is difficult to burn alone, and need to be mixed with coal. The advantage of fluidized bed incinerator is that, because of the garbage after crushing, so that its combustion speed, high combustion rate, start and stop the furnace is convenient, generally discharged out of the unburned material are in 1% or so, is the lowest of several ways. In addition, the structure of the fluidized bed incinerator is simpler and the cost is lower.
The rotary kiln incinerator furnace body is a cylindrical drum using refractory bricks or water-cooled wall furnace wall. It is through the overall rotation of the furnace body, so that the garbage uniformly mixed and along the inclined angle to the tilted end of the tumbling state movement. In order to achieve complete incineration of the garbage, a second combustion chamber is generally provided. When burning the garbage, the garbage is supplied from the upper part of the rotary kiln, and the cylinder rotates slowly so that the garbage is constantly turned and moved backward, and the garbage is gradually dried, burned, and ignited, and then discharged to the slag discharge device.
Adjusting the rotary kiln's rotational speed can affect the residence time of the garbage in the kiln, and by applying strong mechanical collision to the garbage in high temperature air and excess oxygen, it can obtain slag with low content of combustible and decaying materials. The main drawbacks of this technology are the small amount of garbage treatment, the difficulty of fly ash treatment, the combustion is not easy to control, and it is less used in the current waste incineration.
Pyrolysis gasification incinerator technology was first applied in North America, this incinerator is called CAO (Controlled Air Oxidation) in Canada, meaning controlled air oxidation, there are a small number of applications in developed countries.
Pyrolysis gasification incinerator has two combustion chambers, through the control of the two combustion chamber air supply and temperature to achieve pyrolysis gasification and complete combustion. In the first combustion chamber air supply for the theoretical need for 70% -80% of the air volume, temperature control at 600-800 ° C, only part of the solid waste combustion, relying on the heat of combustion to make the rest of the solid waste decomposition of combustible gases; the second combustion chamber for the theoretical need for the amount of air supply of 130% -200%, the temperature is controlled at 1000 ° C or so, the residence time of 2 seconds, so that the combustible gases fully combustible, toxic and hazardous gas fully combustible gases, toxic and harmful gases are completely decomposed to achieve harmlessness.
Pyrolysis gasification incineration can effectively inhibit the generation of dioxin, but the disadvantage is that the scale of garbage treatment is small, the system is complex, the operation cost is high, and there is no engineering application in China.
