The most flexible combustion system in the Binder range, the three step-grate combustion chamber variations are capable of handing a huge range of fuel types and sizes.  The most commonly specified configuration is the SRF-S, an auger-fed boiler with the added advantage of being able to burn both dry and wet fuels - including freshly felled and chipped trees.  In operation, there are few biomass fuels that a Binder SRF-S step-grate system can’t handle.

Built from the same high quality material as the underfed boilers - scale-resistant cast chromium steel, the step-grate unit evenly distributes fuel as it is introduced to the combustion chamber.  The grate design effectively conveys the fuel from the charge auger to the other end of the combustion chamber, drying the fuel with radiated heat within the boiler as it progresses.  This eliminates the need to pre-dry wet fuels, either in the forest or by means of an auxiliary system elsewhere in the installation.


Cutaway of the auger-fed Binder step-grate boiler

Ash and fuel contaminants either pass through the grate screen at the end of the combustion chamber, or fall through the grate elements to be recovered by the ash scraper fitted to the boiler base.  The unit then automatically extracts all this ash and waste to a waiting container for disposal.

There are 3 SRF-S boiler systems installed around New Zealand.  Dunstan High School Hostel, Golden Bay High School and Westland High School.

Boilers based around the SRF-S combustion chamber are available from 130kW to 3MW. Above 3MW, the SRF-S is replaced by the SRF-H, a hydraulic ram-fed system.  The dry-fuel TSRF is based on the same principles as the SRF-S unit, and has been touted as the future of biomass boilers.

   

With the same heavy duty moving grate design, the TSRF is comparable to liquid fuel boilers in terms of its ease of use and automation, with automatic fuel feed, ignition, de-ashing and tube cleaning using Binder’s patented HVA fitted as standard.

The TSRF is capable of burning dry fuels up to 25% moisture, including chips, waste wood, wood pellets and other forms of dry biomass.  Boilers based around the TSRF combustion chamber are currently available from 130kW to 500kW, with larger models planned for the future.

Big brother to the SRF-S unit, the SRF-H is a hydraulic ram-fed combustion system designed for high constant loads, rough fuels and the most demanding operating environments.  Boiler systems designed around the SRF-H unit can be found in hospitals, industrial processes, sawmills and similar roles around the world.

The SRF-H is capable of burning high-ash fuels with moisture levels up to 55% and slivers up to 35cm long.  The heavy-duty feed ram is capable of smashing up larger pieces of wood as it feeds the boiler, making the SRF-H ideal for projects where waste wood is available as a feedstock.

Boilers based around the SRF-S combustion chamber are available from 200kW to 20MW.