Technical Route and Characteristics of Waste Incinerator

In order to recover energy in waste more efficiently and meet more stringent emission standards, countries, especially developed countries, are currently working on the development of the second generation waste incineration process for the 21st century, gasification melting integration technology, in order to minimize the emission of dioxins and heavy metals secondary pollutants, while improving boiler efficiency and power generation efficiency. Japan is the most prominent country in the research and development of the second generation waste incineration technology. Each enterprise has formulated its own second generation waste incineration technology plan and carried out related research work. The vast majority of the technical routes are gasification plus high temperature melting incineration. The following three typical technological routes are introduced.

A Moving Bed Gasifier Mode

The top-down layers of the gasifier are divided into pre-drying section (200~300℃), thermal decomposition section (300℃) and combustion melting section (more than 1500℃). The garbage is added from the upper part of the furnace and decreases with the gas rising from the lower part of the furnace. Flammable gas discharged from the upper part of the gasifier passes through the dust collector and enters the combustion furnace and burns at about 900℃. The coke formed in the thermal decomposition section decreases to the molten combustion section together with the added coke and limestone, and the high temperature combustion is carried out by the oxygen-enriched air supplied from the inlet. From the bottom of the furnace will form a molten state of slag and metal due to high temperature discharge.

B rotary kiln gasifier

After crushing, the garbage is added to the rotary kiln heated by high temperature air by spiral feeder. While accepting the stirring action formed by rotation, the heat decomposition gasification is carried out slowly in the anaerobic gas environment of about 450℃. The combustible gas discharged from the rotary kiln enters the downstream rotary melting furnace directly. The generated semi-coke and non-combustible are discharged from the lower part of the rotary kiln. After cooling by the cooler, the coarse non-combustible and fine semi-coke are separated by the separation device. After crushing the pulverizer, the semi-coke is stored in the silo, the semi-coke in the silo is pneumatically transported to the rotary melting furnace, and incinerated at high temperature at about 1300℃ together with the combustible gas discharged from the rotary kiln. The slag formed by high temperature is discharged from the bottom of the furnace.

C fluidized bed gasifier

After pretreatment, the waste is fed into the bubbling fluidized bed gasifier with a feeder, air gasification is used at 600℃, the mixture of noncombustible and sand is discharged from the bottom of the gasifier, they are separated by a separation device, and the sand is fed back into the furnace. The secondary air is fed into the free space of the fluidized bed for secondary combustion. After entering the cyclone melting furnace, the generated combustible gas is fed into the cyclone melting furnace and the air is burned at 1300℃ high temperature, and the slag is discharged after water cooling.

The main features of the above three types of second generation waste incinerators are: the combination of gasification and melting incineration technology, that is, the first gasification of garbage, gas and gasifier slag removal together in the high temperature melting furnace melt solidification treatment. It can be seen that the second generation waste incinerator can fundamentally solve the problem of secondary pollution such as dioxin and heavy metals. High temperature incineration can not only destroy the catalyst source of dioxin and dioxin contained in garbage. At the same time, most of the fly ash and slag are melted by high temperature incineration, and the vitreous body is formed after sudden water cooling. The heavy metal is solidified and the ash can be used comprehensively. In addition, the system can use gas-vapor combined cycle to greatly improve the efficiency of garbage power generation.

The second generation waste incinerator developed abroad, such as Japan, is mainly aimed at the waste with high calorific value and effective classification in China, which is not suitable for the characteristics of high moisture, low calorific value and non-effective classification of garbage in China. In addition, there are some shortcomings in the development of three types of second generation waste incinerators. Such as moving bed gasifier to form 1700~1800℃ at the bottom of the furnace high temperature zone, so it is inevitable to use coke and other auxiliary fuels. Therefore, the operation cost increases, and the moving bed operation mode will cause the gas to deviate in the rising process, which is unfavorable to the stable operation. Fluidized bed gasifier is not equipped with acid gas removal device, which will cause high temperature corrosion of waste heat boiler and directly affect power generation efficiency.