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7
ADVISING ENGINEER'S REPORT.
REFUSE DESTRUCTORS.
I have carefully considered the information which I have been able to obtain from the
destructors visited with a view to reporting upon the engineering points in their construction
and maintenance, and more particularly with regard to the utilization of the steam which can be
generated from the waste heat in the process of combustion, and I am of opinion that with a
destructor combined with water-tube boilers, so arranged as to obtain the greatest efficiency, a
considerable amount of power may be obtained from the burning of refuse.
The heating capacity of refuse varies largely in different districts, but I think that of
Kingston may be considered an average class of refuse, and fairly suitable for steam raising.
In my opinion, however, the facilities for generating electricity in any quantity from refuse
has been largely exaggerated, and probably the best use to which the power can be turned is in
the direction of driving machinery for working crushing and mixing mills, and generating
electricity for lighting the destructor house and any adjoining buildings, and where the Sewage
Works adjoin the destructor house the power can be used to advantage in driving the sewage
pumps.
It is evident that a destructor with the necessary storage for and ultimate disposal of the
clinkers and the necessary outbuildings will require an area of about one acre, and after making
a careful survey it appears that it is not possible to obtain this amount of ground in the
immediate neighbourhood of the Electricity and Sewage Works.
Again I think it is exceedingly inadvisable to place a destructor, with the large amount of
dust which must necessarily arise, both from the refuse in its raw state and from the clinker
and fine ash in its burnt state, in proximity to the Electricity Works, where a number of high
speed engines are installed, as in course of time the bearings, both of the engines and of the
electrical machines, must suffer greatly from the wear and tear caused by fine particles of grit,
and this notwithstanding that the greatest care is exercised.
If the destructor were placed at some considerable distance, say at the extreme end of Down
Hall Meadows, sufficient power might be generated to operate the pumps and machinery at the
Sewage Works by means of direct current motors, connected by cables to a small installation of
direct current dynamos placed in an engine house adjoining the destructor; although there
would again be the objection of placing these engines in proximity to the destructor.
On the other hand it would not be practicable to convey steam for such a distance as from
the destructor in this position to the Sewage Works. The loss by condensation and radiation
would be too great.
At Cambridge the plant has been working from two to three years, and the engines do not
appear to have suffered from their close proximity to the destructor. These pumping engines
are slow speed engines, and every precaution has been taken to exclude dust from the engine
house. The Parsons Steam Turbine which drives the lighting Dynamo runs at 3000 revolutions
per minute, but the bearings of this class of engine are of a special enclosed type, and the engine
has been working such a short time that it is not possible to judge whether even these bearings
are in any way affected.
I have come therefore to the conclusion that it would not be advisable to place the destructor
upon any portion of Down Hall Meadows, the many drawbacks considerably outbalancing the
few advantages ; and it would therefore be necessary to select another site.
Of the various types, that most suited in my opinion to the wants of this district is a similar
destructor to that installed at Cambridge, namely, a Manlove-Alliott, fitted with patent charging
trucks and cooling chambers.
The dust, which is collected in covered four wheel tip wagons, is discharged direct into the
charging trucks, each of which is divided into several compartments, each compartment holding
one charge of refuse. These compartments are fitted with moveable bottoms, to allow of the
refuse being shot into the furnace, when each compartment in turn is placed over the furnace
opening.
With these arrangements there is an utter absence of smell, dust and litter at the spot where
the furnaces are charged.
The objection which was made to these trucks owing to the breaking of the endless chains
is one merely of mechanical design and would be quite obviated by the use of a better and
heavier class of chain.
The cooling chamber is a most advantageous feature of this destructor, as it does away with
the necessity of pouring cold water on the hot clinker, and causing clouds of steam and dust to
rise, and it seems to me that in such a district as ours too much care cannot be exercised in
preventing smell and dust even at the cost of a few pence extra per ton for destroying the refuse.