Buyer’s guide: Saxlund’s push floor storage and discharge system.
What is your technology?
Saxlund’s push floor storage and discharge system for rectangular flat bottom bunkers and silos, both closed and open to air, is designed specifically for handling non-free flowing bulk solid materials. The equipment is especially important where compaction of material is a problem.
How does it work?
The technology incorporates a series of hydraulically operated parallel ladders or frames, fitted as a grid in the silo floor. These move backwards and forwards with a reciprocating motion, pushing or pulling the material towards the discharge point.
‘First in, first out’ design principles ensure that material is constantly taken from the bottom of the silo to provide reliable discharge and accurate metering on demand.
The shearing action of the ladders helps to agitate and break up material as it moves downstream, and the depth is monitored by level sensors to ensure an optimal feed rate. Gate bars and levelling screws can be incorporated for smoothed discharge if required.
Where would it ideally be used?
The technology is essential for the storage and discharge of any non-free flowing, heavy, wet and difficult to handle bulk materials, especially where they are likely to compact, sweat and degrade.
It is widely used as a stockpile reclaimer and typical materials include: biomass, woodchips and pellets, solid recovered fuel and refuse-derived fuel, tyre chips, sludge cake, processed sewage pellets, plus meat and bonemeal.
Core sectors include the cement industry, alternative energy sector, particle board industries and sludge cake handling.
How is it different?
Push floor technology has been pioneered and developed by Saxlund International for more than 60 years and is supported by numerous patents.
Design knowledge, understanding of the characteristics and composition of each material, coupled with discharge systems and flexible controls, ensures high availability and continuous service, with better lifetime costs than any similar system.
Where has it been used?
Saxlund push floor solutions are deployed in hundreds of sites across northern Europe. Of the 20 or so renewable energy power stations currently under construction in the UK, more than half incorporate push floor silos for fuel storage and discharge.
Slough Heat & Power, owned and operated by SSE Enterprise and one of the UK’s largest dedicated biomass-fired combined heat and power plants, now uses a second push floor fuel handling solution to feed the boiler, including a 720cu m fuel reception area with live storage.
Bouygues Energies & Services, which is responsible for the engineering and construction of the UK’s largest energy-from-waste gasification plant currently underway at Hoddesdon in Hertfordshire, has also selected push floor fuel storage and discharge bunkers for the new facility.
As a bespoke solution, the cost is dependent on individual project requirements and material storage volumes.
What about maintenance?
Saxlund push floors are typically designed to match plant requirements with continuous availability. In a typical biomass power plant, they are engineered to provide a minimum 8,000 hours of operation between shutdown inspections.
Key maintenance areas are installed externally to minimise disruption and overhauls can be carried out with a full silo.
- Ensures oldest material is always used first
- Minimises opportunity for stored material to degrade or lose calorific value
- Overcomes the issues of compaction, sweating and self-combustion – typical of materials with a high moisture content
- Minimises the opportunity for material to block, build-up and bridge the discharge point
- Ensures uninterrupted operation and zero downtime for other plant processes
- Low power consumption and low maintenance costs