IMPROVEMENTS IN FURNACES
Year: 1883

page_text: PROVISIONAL SPECIFICATION left by Charles John Chubb at the Office
of the Commissioners of Patents on the 24th October 1883.
CHARLES JOHN CHUBB of Clifton in the County of Gloucester "IMPROVEMENTS
IN FURNACES"
This Invention has for its object improvements in furnaces, and more especially
such furnaces as are intended to burn small coal or slack, but it is applicable also
to furnaces in which other fuel is employed.
The invention is also applicable more especially to the furnaces of internally fired
steam boilers, but it can be applied also to other furnaces.
I construct the furnace of an internally fired steam boiler as follows:-
At the lower part of the internal flue of the boiler in which the furnace is
constructed I place an horizontal plate or partition enclosing an air passage. This
air passage passes along the fire box from the front of the furnace to the bridge.
I employ a divided bridge, and the passage delivers almost cold air into the space
within the bridge. The fuel is burned on fire bars in the usual manner, except
that by preference only a small quantity of air is admitted between the fire bars,
consequently the combustion is imperfect and a considerable quantity of carbonic
oxide and hydrocarbon gas or vapour is generated. Upon the top of the bridge I
build a perforated structure of brickwork which intercepts the gases and products
of combustion in their passage forward from the fire box and divides them into
numerous currents. The air admitted to the hollow bridge, also enters passages
formed in this brickwork, which are alternated with the other passages so that the
carbonaceous gases and the fresh air issue into a combustion chamber on the further
side of the bridge in parallel thin sheets. As the heated gases and the air are
intimately mixed the combustion in the combustion chamber is very perfect. The
heated products are afterwards in the usual manner led through tubes or flues
properly arranged as to enable them effectively to impart their heat to the water
of the boiler.
When I employ small coal or slack I arrange another plate in the fire box above
the lighted fuel on the fire bars and extending from the front of the furnace
towards the bridge but terminating before reaching the bridge.
Upon this plate the small coal with which the furnace is fed is placed. In
feeding the furnace the small coal is so placed in order that it may become heated

page_text: and caked together and give off its hydrocarbon gas before it reaches the fire bars.
When the caking has progressed sufficiently far to cause the small fuel to cohere
into lamps, it is pushed off from the end of the plate and it falls upon the fire bars
beneath and is spread over them evenly.
The feeding of the furnace and its distribution evenly upon these bars may be 5
effected either by hand or by mechanical appliances. By causing the small coal to
be caked within the furnace in the manner described, before it is placed upon the
fire bars I avoid the loss which would otherwise result from the small coal falling
through unburnt into the ash pit. The fuel upon the bars will also always be
sufficiently open to admit the air necessary for combustion to permeate amongst it. 1