Why Reciprocating Grates Are Recommended for Municipal Solid Waste Incinerators
A reciprocating grate is the recommended choice for municipal solid waste incinerators because it fits low calorific value, high moisture, mixed-composition waste better in 4 respects: fuel adaptability, combustion efficiency, environmental protection, and operation and maintenance. The alternating movement of moving and fixed grate bars is the basis of these properties.
Fuel adaptability
Municipal solid waste contains kitchen waste, plastics, paper and other components, with high moisture and widely varying calorific value. Through the alternating reciprocating movement of moving and fixed grate bars, a reciprocating grate actively turns and loosens the fuel bed and breaks up clumped waste, avoiding poor local ventilation. Adjusting the movement frequency controls the residence time of the waste in the furnace, and with hot primary air even low calorific value, high moisture waste can be dried and ignited fully. Stable combustion is therefore possible without strict pre-treatment.
Combustion efficiency and volume reduction
Along its length the grate is divided into a drying and ignition zone, a main combustion zone and a burnout zone, with air distributed precisely according to the combustion process. High-frequency movement in the main combustion zone strengthens the mixing of fuel and air, while slower movement in the burnout zone ensures the fuel burns out fully, so the carbon content of the ash can drop below 3% and combustion efficiency rises by 15%-20% against a conventional fixed grate. Efficient combustion recovers more heat for power generation, the waste volume reduction rate reaches over 80%, and the loss on ignition of the residue is held below 5%.
| Parameter | Value |
|---|---|
| Carbon content of ash | Below 3% |
| Combustion efficiency gain | 15%-20% |
| Waste volume reduction rate | Over 80% |
| Loss on ignition of residue | Below 5% |
| Furnace temperature | ≥850℃ |
| Flue gas residence time | ≥2 seconds |
| Grate bar replacement cycle | Over 3 years |
Environmental performance
A reciprocating grate follows the “3T+E” combustion principle, and with independent zoned air supply and staged secondary air it controls furnace temperature and oxygen concentration precisely. With a furnace temperature of ≥850℃ and flue gas residence of ≥2 seconds, dioxin formation is suppressed at the source while NOx and CO emissions are reduced. The modular design and precise combustion control also cut the use of environmental consumables and ease the load on downstream flue gas treatment.
Operating reliability
A reciprocating grate is hydraulically driven, and the drive mechanism sits outside the grate where ambient temperature is low and wear is small, so reliability is relatively high. The grate bars need no bolted connections, and the modular design allows replacement directly from above the grate, making installation and repair convenient. The replacement cycle can be extended beyond 3 years, which cuts unplanned downtime. An automated control system adjusts the feed rate, grate speed and air volume, lowering labour cost and operating energy use.
