The ultimate Multi-Solid Fuel Heating Appliance
The Super Demon Multi Solid Fuel Stoves
Features:
- Advanced Combustion technology, not available in any other make of appliance.
- Overall efficiency far greater than with conventional solid fuel technology.
- Boiler outputs to suit actual practical requirements. Conventional stove boiler outputs of the order of 40,000 BTU/hr are totally inadequate for most practical applications which normally require at least 55,000BTU/hr. The Super Demon gives you the following boiler capacity of 60,000 BTU/hr on wood and 75,000 BTU/hr on solid fuels. The unit may be operated at any loading from 15,000 BTU/hr to the above maxima; with lower loadings you merely burn less fuel.
- Unique Upward Flowing Airwash System to keep door glass clear and to provide pre-heated secondary air to the secondary combustion zone.
- Ease of Cleaning of heat exchanger surfaces and facility to sweep vertical flues, thereby avoiding the need for soot doors on internal chimneys.
- Boiler Design that has eliminated the problems of pyroligneous and sulphuric acid corrosion that shortens the life of conventional multi solid fuel boilers.
- Fully Multi Solid Fuel Riddling Grate with ashpan.
- Thermostatic Control of primary air supply.
- Very Rugged Cast Iron and Steel construction for Long Life.
Design Criteria
Conventional Multi Solid Fuel Appliance Design
The Boiler consists of a simple wrap around boiler with a thermostat controlling the total air supply.
Such designs are limited to practical boiler outputs of the order of 40,000 BTU/hr on solid smokeless fuels and less on wood.
It is quite obvious that the design are relatively inefficient as when operating at these outputs the flue gas temperatures are of the order of 400 to 500 deg c particularly when burning volatile fuels.
When the thermostat is closing it restricts the supply of air to the fire so that any volatile components of the fuel pass into the flue in a partially burnt state. This leads to carbon and hydrocarbon deposits known as soot and tar. Rather like controlling your car engine using the choke.
From the practical operation of these designs with volatile content fuels the deposits of soot and tar are unavoidable and in some cases constitute a considerable fire hazard.
Another disadvantage of this type of design is the production of pyroligneous and sulphuric acid during the oxygen starved part of the combustion process.
This acid attacks the boiler surfaces and leads to premature boiler failure which has been the Achilles Heel of the conventional multi fuel boiler designs. This has now been proven beyond doubt and has led to the demise of a large number of the companies manufacturing the conventional designs.
As a consequence of the above inadequacies of conventional designs we commenced a research programme in 1976 to develop an appliance to overcome the above problems.
By 1980 we were producing the first models of the Super Demon technology and over the ensuing years we have produced many thousands of boilers based upon this design.
Now in 1998 we are totally convinced of the superiority of our designs over those of the conventional type. The resistance of the boiler design to acidic corrosion has proven itself beyond doubt.
The combustion efficiency has resulted in very much reduced chimney sweeping. Tar and excessive soot are not apparent in the flue but appear to be replaced by a grey dust and fly ash.
We have had no reported cases of chimney fires with our appliances even when routine cleaning has been somewhat neglected.
The measured average efficiency of the appliance exceeds 80% based on the GCV (Gross Calorific Value).
The Super Demon Stove Boiler
This appliance differs from the conventional designs.
The secondary air supply is entirely independent of the primary air supply. The secondary air passes under the doors and through two additional control vents so that adjustments can be made to the volume of secondary air available to suit the volatile content of the various fuel types. The secondary air can never be fully shut off this ensuring an adequate supply of secondary air to burn any volatiles passing from the fuel bed into secondary combustion zone.
Upon entering the stove the secondary air is deflected vertically upward over the glass doors and the finned deepening bar. This serves to preheat the secondary air and to keep the doors glass clear.
When burning volatile fuel such as wood and coal we discovered that the volatile hydrocarbon output from the fuel bed in the initial stages of combustion was determined by the fuel bed temperature. The primary air thermostat controls the primary air supply and thence the fuel bed temperature the secondary air system supplies sufficient oxygen for the adequate secondary combustion of volatiles arising from the fuel bed. Extensive use is made of ceramic fibre materials as pyrolytic combustors in the secondary combustion zone. These combustors promote secondary ignition by virtue of their local surface temperature acting as to enhance secondary ignition.
Following the secondary combustion region we have incorporated a further heat exchanger to recover the additional heat liberated in the secondary combustion reactions. Typical final flue gas temperatures with the Super Demon lie in the region of 150 to 200 deg C. This is lower than that of a standard oil or gas boiler.
As the combustion gases rise through the stove they exchange their heat with the boiler surfaces. This is geometrically arranged so that as the gases become cooler the water becomes hotter, and where the gases are their coolest the heat exchange water is at its hottest. Such as arrangement is made in order to minimise condensation and subsequent corrosion of the boiler surfaces. To make warm up time minimal, a pipe thermostat is used to eliminate pump operation until the boiler temperature exceeds 60 deg C.
The scavenging effect of the continuously operating secondary air system also prevents concentrations of acidic gases remaining in contact with the heat exchanger surfaces.
In recent years several manufacturers have attempted to copy the airwash system, but have failed to appreciate the basic principles, as they bring their airwash intakes to run downwards over the doors rather than upwards. The downward flowing air impinges on the fire bed and means that in order to control the fire you have to turn down or off the secondary air supply, this leads to a blackening of the glass and poor combustion.
In our system the secondary air passes up the doors and does not excite combustion in the primary fire bed, so that good primary and secondary combustion can be achieved over the whole dynamic out range of the appliance.
The Super Demon stove boiler can be used either as a prime heating source or as a linked system with oil or gas boilers. This latter option we think is the best option for a future market for solid fuels. You can have all the automation or oil or gas fired boilers and yet be able to have a real fire which looks attractive and is utilising as much of the available energy from the fuel as possible to run your heating system. In this way in burning low grade cheap solid fuels at peak heating demands times like the evening period overall fuel costs savings can be made, as well as having an aesthetically pleasing fire to look at.
Chimneys
Of all the problems dealt with by our engineers, faulty chimneys are by far the most common. The following are basic considerations for the chimney construction in their case:
- The minimum internal diameter of the flue shall be not less than 7" (175mm) with chimney heights exceeding 5m. With shorter chimneys 8" (200mm) internal diameter is required.
- Avoid bends in the chimney when constructing new chimney. It is a myth that bends stop down draughts. Chimney should be a straight as possible, if bends are unavoidable then they should be made as gentle as possible.
- Old chimneys, if found to be defective should always be lined with suitable lining systems for solid fuel.
- Be very careful in the construction to avoid air leaks into the chimney, joints should be sealed, liners bedded and filled around with vermiculite lime mortar or leca/cement mixes.
