Sessional_Paper_1899 — Page 153

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Efficiency of Furnaces.

The quantity of refuse, which may be burnt per diem by any type of furnace, can only be ascer- tained by experiment, as it depends so entirely upon the calorific qualities of the refuse dealt with and the period of burning.

For instance, at Leyton where Messrs. BEAMAN AND DEAS' furnaces have been erected, it is stated that under forced draught 16 tons per cell per diem are burnt, consisting of refuse and sludge mixed in the proportions of 1 to 1.

At Whitechapel, Messrs. MANLOVE ALLIOTT & Co.'s furnaces are said to burn 10 tons per cell per diem under natural draught.

At Edinburgh, where the refuse is said to be very poor in quality, 8 tons per cell per diem are burnt by the Horsfall furnaces under forced draught. The furnaces are, however, new and better results will probably be obtained.

At Bow Road, Poplar District, where Messrs. GODDARD MASSEY AND WARNER'S furnaces are working, I learn that 6 tons per cell per diem are burnt under natural draught; it is expected that 8 tons or more will be burnt when forced draught is fitted. At Kurrachi, India, the same firm have erected a 2-cell Destructor which is reported to burn 11 tons per cell per diem under natural draught. It will thus be seen that results vary considerably, and I am of opinion that in designing furnaces for Hongkong it would be unwise in the present state of our knowledge to calculate on burning more than 6 tons per

cell per

diem.

The refuse from a Chinese city, where all cooking is done on charcoal ranges or chatties, will almost certainly have a lower calorific value than that of a European city where the refuse contains some 60% of cinder, which assists in the burning and is the chief factor in producing heat. The Hongkong refuse, however, contains a quantity of vegetable matter, rattan shavings and other com- bustible matter, and no difficulty is anticipated in successfully burning it.

It is needless to say that one type of furnace may burn more than another, or that the quantity burnt may be regulated by the hardness of clinker required. The longer the period of burning and the higher the temperature, the harder will be the clinker. In England the period of burning varies from one to two hours per charge.

Disposal or Utilization of Clinker.

There will necessarily be always a certain quantity of waste material to dispose of after the burning. Quoting from a report by Sir A. BURNIE and Dr. SHIRLEY MURPHY to the London County Council, dated May 10th, 1893, by burning in a Destructor "the matter collected is generally reduced to about one-third its original weight and to about one-fourth its original bulk. The organic and combustible matters are burnt, and the residue consists of ash and clinker free from matters which can become offensive, and which are, if the Desturctor is properly used, purified from possible sources of contagion."

The residue has been utilized in various ways as follows, and it has in certain instances been sold. At Manchester-the clinker, when ground up and mixed with lime, makes an excellent mortar which is easily disposed of, the demand being in excess of the supply.

At Hornsey" the clinker is used for mortar, concrete, hard-core for new roads, paths, for making paving slabs, etc., and a ready sale for same is found at 2s. Od. per one-horse load (at the Depôt) when the Council have any to dispose of."

At Edinburgh, the clinker is used for raising the level of low-lying ground within the curtilage of the works.

Being thoroughly burnt and therefore harmless, the clinker may safely be used for filling up hollows in waste ground, and could be disposed of in this way on the Reclamation Works so long as they are in progress, or at Kennedy Town where there are building sites several feet below the level of the roads and where I anticipate that the permission of the owners would be readily given.

It is possible that some of the residue may be sold, but as granite can be easily obtained for concrete and red earth for mortar, and both are probably better for the purpose, this possibility must not be reckoned on.

Should it become necessary to barge away the clinker-a contingency I do not anticipate-the matter collected will still have been reduced to about one-third of the original weight and the necessity will not exist for immediate removal.

Utilization of Heat.

• Although the sole object of the furnaces is the destruction of the city refuse, it is yet possible that, after such destruction, use may be made of the heat generated. The various ways in which this heat be utilized were set forth as follows in the specification submitted to the firms for tenders:--

may

(a) To cremate carcases of cattle.

(b) To cremate, or dry for manure, offal from the Slaughter Houses.

(c) To destroy mattresses and infected clothing.

(d) To supply heat for a 100-H. P. boiler.