Stepped grate firing system 850 to 10000 kW
The stepped grate firing system is particularly suited to the combustion of wood fuels with a high water content of up to 60% and an ash content of 10%. These conditions allow the flexible use of inexpensive, undried fuels such as forest wood chips, green cuttings, bark, wood from landscaping, short-rotation woody crops and mature timber. The wood-burning system Pyroflex SRT with stepped grate firing system is designed for continuous operation of up to 8000 hours per year.
Designed for continuous operation
Fuels:
Wood from landscaping
Bark
Green cuttings
Mature timber
Short-rotation woody crops
Special fuels
The Pyroflex SRT is particularly suited to the combustion of wood fuels with a high water and ash content. These conditions allow the flexible use of inexpensive, undried fuels.
Flue gas recirculation “over” and “under” the grate
The flue gas is drawn into the exhaust line and reintroduced to the combustion chambers “over” or “under” the grate with a fan. This decreases the flame temperature and reduces nitrous oxides. The efficiency of the system is increased as a result since a lower residual oxygen content remains in the flue gas, even in the case of dry fuels.
For the flue gas recirculation “under” the grate, the recirculated flue gas is mixed with the primary air in mixing chambers and then reintroduced under the grate. The flue gas recirculation “under” the grate also results in more complete combustion and prevents slag formation on the grate.
Minimal life cycle costs
We place the utmost importance on durability and a long lifespan for our systems. This is achieved by using robust system components. Solid steel construction and the use of high-quality refractory material guarantee reliable system availability for many years. Minimal power consumption in all load states of the system is ensured by frequency-controlled screws, grate drives and flue gas recirculation.
Equipment and accessories
Measurements in the primary air and recirculation air
The flow rates of the primary and recirculation air are measured, and the required air quantities are calculated in advance. This achieves optimal combustion results and emissions values in all load stages, including with difficult fuels. The grate of the Pyroflex SRT is divided into up to four independent primary air zones. This allows the required air quantities to be adapted to the fuel.
Use of high-quality O2 probes
The secondary air flow rate is regulated based on the detected oxygen level. High-quality O2 probes make it possible to maintain a continuously low residual oxygen level in the flue gas (approx. 4–5% O2 (damp) – depending on the fuel). This allows the highest levels of efficiency to be achieved even in modulating partial load operation.
Automatic ash removal
Several variants are available for removing ash from the combustion chamber as well as the cyclone and electrostatic filter, depending on the fuel and ash content. The ashes can be discharged jointly or separately. They are deposited into containers of up to 800 l or in settling pits of 5.5 to 12 m2. They can also be filled into big bags.
The following variants are available:
- With trough chain conveyor
- With screws
- Laterally from the combustion chamber
- Directly under the combustion chamber
- 3-pass boiler (6.0 bar – higher pressure ratings on request)
- Safety heat exchanger (integrated into boiler)
- Stepped grate, hydraulically driven (divided into up to four zones, depending on type) with injection of the primary air
- Injection of secondary air
- Injection of flue gas recirculation “above the grate”
- Hydraulic infeed / direct infeed with water-cooled infeed neck or infeed screw
- Automatic combustion chamber ash removal
- Firebox doors
- Injection of flue gas recirculation “under the grate”
- Pneumatic boiler tube dedusting
Profit from these benefits:
- Fully automatic wood-burning system with stepped grate 850 to 10000 kW
- Fuel water content: 6 to 60%, ash content (share of foreign matter) up to 10%
- Stepped grate technology with up to four independent primary air and grate zones and hydraulically driven grates
- The use of frequency-controlled screws, grate drives and fans for the flue gas, secondary air and recirculation ensures minimal power consumption in all load ranges of the system
- Low flow speeds over the fire bed prevent turbulence, ensuring low-emission combustion in all load states
- The generously dimensioned firebox geometry guarantees reduced stress on components and the refractory lining. This makes the firing system suitable for continuous operation of up to 8000 hours
Optional accessories
- Pneumatic boiler tube dedusting (significantly extends the time between cleanings)
- Automatic ignition system (automatic ignition for fuels with a water content of up to 35%)
- Remote maintenance and visualisation systems (full system access from a PC, tablet or mobile phone)
- Raising of the flue gas temperature (to avoid condensation in the flue gas path and in downstream components)
- Nitrogen oxide reduction system (for reducing of NOx emissions with the SNCR method)
- Continuous emissions measurement
- LUVO (preheating of the primary air for wet fuels)
- A firebox camera for monitoring the firebox is an optimal addition to a visualisation system
Example installation
Process steam for industry
Firing system: Pyroflex SRT
Output: 10000 kW
Fuel: Wood from landscaping M55, A10
- Fuel storage in reserve bin with crane feeding
- Daily supply bin with moving floor discharge
- Fuel transport: Tray chain conveyor and hydraulic infeed
- Firing system: Pyroflex SRT
- Ash removal from the combustion chamber into pit via trough chain conveyor
- Coarse dust separation: Multicyclone separator
- Removal of fine dust from the flue gas by electrostatic filter
- Gas-fired boiler for covering peak loads