CFB Incinerator is another type of waste incineration boiler besides grate incinerator. Circulating fluidized bed boiler has many advantages, such as high burnout rate, low carbon content in ash, wide load adjustment range, wide fuel adaptability. However, its operating cost is relatively high. It includes waste heat power generation, desulfurization and dust removal, DCS, waste pretreatment, fuel feeding and cooling deslagging system. MSW incinerator manufacturer Taishan draws lessons from advanced CFB solid waste incineration technology in European, and introduces first MSW CFB Incinerator with a daily treatment capacity of 1000tons.
Solid recovery fuel pretreatment process
After drying and sorting, primary garbage is no longer waste in traditional sense, but solid recovery fuel. Pretreatment mainly involves drying (reducing moisture from 60% to below 30%), mechanical crushing and sorting. It reduces the garbage size, remove non-combustible materials like metal, rubble and glass, and increase the proportion of combustible materials. Pretreatment ensures more even fuel feeding, more thorough combustion, less slag and dioxin generation, and much cleaner emission. The fuel characteristics after drying and mechanical sorting are shown in table 1.
Table 1. Fuel characteristics
| No. | Item | Symbol | Unit | Value |
| 1 | Moisture (as received basis) | Mar | % | 30 |
| 2 | Ash (as received basis) | Acr | % | 21.63 |
| 3 | Carbon (as received basis) | Car | % | 27.43 |
| 4 | Hydrogen (as received basis) | Har | % | 3.76 |
| 5 | Nitrogen (as received basis) | Nar | % | 0.45 |
| 6 | Sulfur (as received basis) | Sar | % | 0.48 |
| 7 | Oxygen (as received basis) | Oar | % | 15.8 |
| 8 | LHV (as received basis) | Qnet,ar | KJ/kg | 10,465 |
Table 2. CFB Incinerator design parameter
| No. | Item | Designed value |
| 1 | Fuel treatment capacity / (ton/day) | 1000 |
| 2 | Main steam flow / (t/h) | 130 |
| 3 | Main steam temperature / (℃) | 520 |
| 4 | Main steam pressure / MPa | 7.9 |
| 5 | Boiler efficiency / % | 87 |
Process characteristics of CFB Incinerator
(1) CFB incinerator adopts high-temperature water-cooled cyclone separator and external heat exchanger to better prevent thermal expansion and superheater corrosion. It also adopts flue gas recirculation technology with low air ratio and combined soot blowing technology. Automatic multi-point feeding system can ensure higher incineration automation and more uniform feeding, and fly ash content can reach 5%.
(2) The fuel particle size of below 80mm makes incineration more sufficient. The pollutant emission concentration is lower, which meets cleaner production and promotes circular economy.
(3) After sorting, the garbage volume reduces by 40%, which makes the slag discharge smoother.
(4) Sub-high temperature and sub-high pressure steam is beneficial to efficient conversion and utilization of energy.
(5) No auxiliary fuel needs to be added, annual operation time exceeds 8000h, and incineration load ranges from 70% to 110%. The main combustion zone temperature is above 900℃, flue gas temperature is above 850℃, and residence time exceeds 2s. The clinker ignition loss is below 1.5% and the emission is better than GB 18485-2014 flue gas emission standard.
