Technical Comparison of Several Major Waste Incinerators

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Mechanical Grate Incinerator

Work Theory: the waste is stocked into the incline downward grate through the hopper (the grate is separated as drying zone, incineration zone and burnout zone). As a result of the interlaced motion between the grates, the waste is further pushed downward to pass through each zone on the grate (it works out major turnover as the waste moves from one zone to another) until exhausted and discharged out of the furnace. The incineration air enters into the grate from the bottom to mix with the waste; the high-temperature gas generates heat steam on the heating surface of the boiler and the gas is cooled. Finally the gas is discharged after processed by the gas processing apparatus.

Features: the grate is strict with material and processing precision, namely that the contact surface between the grates should be relatively smooth with rather narrow gap. Meanwhile, due to the complicated mechanical structure, high damage rate and considerable maintenance frequency, the production and maintenance costs for grate are quite high, making it difficult to promote application in China.

Fluidized Bed Incinerator 

Work Theory: the furnace is made of porous distribution plates. Before stocking the waste, a large amount of quartz sand is added into it and heated to above 600 , plus hot air above 200 blown into the bottom of the furnace, the quartz sand boils up. Both the quartz sand and waste boil up at the same time, as a result of which the waste is dried, fired and burnt quickly. Those not sufficiently burnt with a lighter weight will continue to boil and burn, while those exhausted weighted heavier will deposit to the bottom of the furnace. After water cooling, the sorting equipment will separate the coarse and fine slag to the outside plant, and a small amount of medium slag and quartz sand will be returned to the furnace to continue to use by the hoisting equipment.

Features: fluidized bed enables full incineration and better control over incineration inside the furnace. However, the gas contains a large amount of dust, plus the complex operation and higher operating costs; it is stricter with the uniformity of the size of the fuel particles and requires a high-power crusher. The quartz sand will cause great damage on the equipments and considerable maintenance frequency accordingly. 

Rotary Incinerator

Work Theory: rotary incinerator has the cooling pipes or refractory materials arranged along the furnace, and the furnace placed horizontally and slightly inclined. As the furnace rotates constantly, the waste burns to the maximum and moves towards the furnace inclination until exhausted and discharged out of the furnace.

Features: the utilization capacity is high with low content of carbon in the ash, low excess air and emissions of harmful gases. However, it is not easy to control incineration, which becomes difficult upon a low calorific value.

CAO Incinerator

Work Theory: the waste is transported to the storage pit, and enters into the biological treatment tank where it will be dehydrated under the action of microorganisms to make the natural organic matters (food waste, leaves, grass, etc.) decomposed into powder, while other solid organic synthesis e.g. plastics and rubber and inorganic matters in the waste can not. After filtering, those wastes failing to be decomposed will first enter the first incineration chamber(at the temperature of 600 ), of which the gas generated will enter the second incineration chamber and those non-flammable and non-thermolysis component in the form of ash will be discharged out of the first incineration chamber. The second chamber is controlled at the temperature of 860 for incineration and the high temperature gas will produce steam in the heating boiler, which will be exhausted into the atmosphere through the chimney after processing. Metal glass will not be oxidized or melt in the first incineration chamber and can be collected through ash separation.

Features: useful substances in the waste can be collected; but a single incinerator works out only a small amount with a long processing time. Currently, the processing capacity of a single incinerator reaches up to 150 tons on a daily basis. As the gas stays less than one second at the temperature above 850 , the level of dioxins in the gas is high and thus finds it difficult to reach the environmental standards.

Impulse Type Grate Incinerator

Work Theory: the waste enters the dry bed of the incinerator through automatic stocking unit for drying. Then it goes into the first section of the grate, where the waste will be volatilized and cracked under the high temperature. The grate will move up and down driven by the impulse aerodynamic device to throw the waste down to the next grate where the high polymer material will be cracked and other materials keep incineration. The cycle continues until the waste is exhausted and enters into ash pit to be discharged by the automatic cleaning device. Combustion air blasts from the vent on the grate to mix with the waste for incineration, and makes the waste suspended in the air. Those substances volatilized and cracked will enter into the second incineration chamber for further volatilization and combustion, and the unburned gas will flow into the third incineration chamber to be completely combusted; the high-temperature gas generates heat steam on the heating surface of the boiler and the gas is cooled before discharged.

The advantages are as below:

 (1) Capable of handling a wide range of waste including industrial waste, domestic waste, hospital waste and waste rubber tires.

 (2) A high combustion thermal efficiency that normal reaches above 80% and above 70% for even the domestic waste of high proportion of moisture 

 (3) Low operation and maintenance costs thanks to many special design and high level of automation which enables less labor force (only two personnel including the ash removal personnel for a single incinerator) and maintenance workload.

 (4) High reliability as shown by the operation of nearly 20 years that the failure rate for this incinerator is very low which can operate for more than 8,000 hours annually to reach a utilization rate of more than 95%

(5) High level of emission control thanks to advanced secondary gas re-incineration and gas treatment equipment to enable fully processing of the gas. Based on long-term test, the content of CO is 1-10PPM, 2-3PPM for HC and 35PPM for NOx in the gas emissions, fully in line with European emission standards. The gas in the second and the third combustion chambers is burnt at the temperature of 1000 with a residence time of 2 seconds or more, which can basically break down the dioxins and the dioxin content in the gas is 0.04ng / m3 that is far lower than the 0.1ng / m3 stated in Western standards.

 (6) the grate performs self-cleaning under the blowing of the compressed air. 

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    Jiangsu Jinqiu Environment Science & Technology Co., Ltd is developed based on Jingjiang Jinqiu Industry Co., Ltd.

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    The brand "Jinqiu Green" has been established in 1993.

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