CA2226654A1 - Air tight pellet fueled heating stove apparatus with high efficiency and method of utilizing biomass pellets by employing anaerobic heating for pyrolysis, combustion, and incandescent charcoal oxidation for gasification - Google Patents

Description

Page 1 of 2 Air Tight Biomass Pellet Fueled ~-I~ating Stove Apparatus with High Efficiency and Method of utilizing ,~iomass Pellets by ernployirig anaero~ie heating for pyrol~sis, c4mbustioxt, and incandescent charcoal oxidation for gasification. .
ABSTRACT:
The present invention is directed to an air tight pel-let fueled gasifier.
space heating stone designed to operate at a substantially reduced air to fuel ratio as compared to existing design technology. The combustion of volatile biomass pellet fuel gases is carried on in a close coupled retort cumbustor within the pellet stove, ,who's combustion air is regulated by an oxygen seilsor'so: as to substantially. increase the over all steady state efficiency level by cor~tralling the combustion arr~level to pellet fuel quantity ratio's and rate of burn within the cumbustor zone of the pelie~ stove.
The initial 2~naerobic heating: for pyrol~sis can take place in an oxygen starved charriber below, adj a~~ent to, irt: close proxirinity to or remotely from the retort combustion chamber where the biomass pellet fuel gases are tlxen optimally m,ixeri within a specific range of oxygen relative to the quantity-of pellet fuel present, Tlie biamass gases from the negative pressurized pyrolysis chamber acre drawn through. , the retort combustion chamber zone, where combustion of the gales takes place;
completelyoxidizing the organics. The amount of combustion air to the retort burner is regulated rby an Uxygen sensor in propprtion to the amount of pellet fuel being combusted. The Oxygen sensor employs a :feed back loop to the main controls of the appliance, which control the fan rnotan ~p~ed supplyixtg- he induced combustion air being drawn thror~:gl~ the combustion'zune. The oxygen sezlsor measures oxygen concentrations between lean (any oxygen in the exhaust stream not being utilized to combust pellets) to rich oxygen (when there is not enoughyxygen for the amount of fuel present in the combustion zone). The Oxygen sensor balances the level of air to fuel so as o maihtain ~ op#im~n rate of burn; which in fotri effects the efiiciertcy level of the combustion rirocess. Thc; Oxygen sensor having an output of ~--OmVolt when there is oxygen and ~800m~1alt vahen there is no oxygen sends back a signal to the stove controls.
The pellet stove gasifif;rs electronic controls esselttially senses a square wave from the sensor and balances the; binary states by trirriming or increasing the combustion air into the combustion gone.
T'he-feedba~ck loop sensor through the e~ectroriic controls of the stove;
toggle the binary states (okygen present for optimum corif bustion) during the' combustion process so as to achieve optimal quantities of ,combustiGin air in proportion to the amount of biomass Page 2 of 2 pellet i;uel present at any given time. As a result; high steady state efficiency is achieved ~d mai~ta~~nea.
An. improved initial pyrolysis/gasificat~on zone within the stove employ's a unique grate , desigp: and i:uricti~n. The pellet stove employ's a primary grate which supports the pellets during iztitia pyrol~sis of the biomass-~eliet fuel and may employ a secondary grate below the first grate. Each fuel supporting grate is comprised' of several three sided metal rtes having a specifiie distance between each of them; arranged in parallel;
which area b~tvc~een adj scent supports, being the opening toy the ash pan below is dependent on the size and diameter of the biomass pellet;rfuel being introduced into the initial grate zone.
Since the pellet stove employs an six tight design through the use of gasltets and .other measures throughout; no combustion air enters through the ash pan area door opening and up through the grate which rests beloWthe vertical or Horizontal retort combustion zone arid whick supports 'the pellet fuel duril~g initial combustion.
Air ~s introduced well enough above arid away fiom the initial g~sification fuel bed zone so as to induce by negative pressure thd gases and flames away from fuel hed area of the grate, therehy substantially decreasing ~e temperature id the .grate area as compared to where the b:iomass gases are: substantially combusted in the retort burner.
This permits for the use of high' ash pellets fuels contai~ng inorganic elements within the pellet fuel , without xhe usual associated probleriis mound in other types of pellet stove burn pot designs .
The pyrolysis zone is somewhat void of combustion air and the main elements found ~~e pellet fuelstend not to' fuse clue to a decrease in the temperature viTithin the this area. All inorganic elements melt at varying teanperatures; macro and micro inorganic elements vvluch may be present within 'the biornass. geliet fuels during initial pyrolysis tend not to i:nse and form clinkers or h~tl slag deposits.
The grate may be physically disturbed by means of a device employed to create a vibration through the grates physical st~uctu~re. This perliiits for the substantially carbonized liiomass pellets to fall thrvh the first grate and onto the second grate below;
where the same: device may be empldy~d. Since there is no combustion air praceedirtg up fiom the bp~ttom of the gfate and passing through: the fuel bed, thin design is employed to promote the: passage of the inorganic elements and anp char which may be present into .
me ash pall below he grate area.

Claims