Page:1902 Encyclopædia Britannica - Volume 27 - CHI-ELD.pdf/468

 426

DESTRUCTORS be kept open as short a time as possible in order to prevent the general arrangement the destructor differs considerably frem admission of cold air into the furnace at the back end, since this those previously described. The grates are placed side by side leads to the lowering of the temperature of the cells and main without separation except by dead plates, but, in order to flue, and also to paper and other light refuse being carried into localize the forced draught, the ash-pit is divided into parts the flues and chimney. The flues of each furnace are provided corresponding with the different grate areas. Each ash-pit is with dampers, which are closed during the process of clinkering closed air-tight by a cast-iron plate, and is provided with an airin order to keep up the heat. The cells are each 5 feet wide and tight door for removing the fine ash. Two patent Meldrum 11 feet deep, the rearmost portion consisting of a firebrick dry- steam-jet blowers are provided for each furnace, supplying any ing hearth, and the front of rocking grate bars upon which the required pressure of blast up to 6 inches’ water column, though combustion takes place. The crown of each cell is formed of a that usually employed does not exceed inches. The furnaces reverberatory firebrick arch having openings for the emission of are designed for hand-feeding from the front, but hopper-feeding the products of combustion. The flap dampers which are fitted can be applied if desirable. The products of combustion either to these openings are operated by horizontal spindles passing pass away from the back of each fire-grate into a common flue through the brickwork to the front of the cell, where they are leading to boilers and the chimney-shaft, or are conveyed sideprovided with levers or handles ; thus each cell can be worked ways over the various grates and a common fire-bridge to the independently of the others. With the view of increasing the boilers or chimney. The heat in the gases, after passing the steam-raising capabilities of the furnace, forced draught is some- boilers, is still further utilized to heat the air supplied to the times applied and a tubular boiler is placed close to the cells. furnaces, the gases being passed through an air heater or conThe amount of refuse consumed varies from 5 tons to 8 tons per tinuous regenerator consisting of a number of cast-iron pipes cell per 24 hours. At Hornsey, where 12 cells of this type are in from which the air is delivered through the Meldrum “blowers” use, the cost of labour for burning the refuse is 9Jd. per ton. at a temperature of about 300° F. That a high percentage (15 The Meldrum “Simplex” destructor (Mg. 3), a modern type to 18 per cent.) of C02 is obtained in the furnaces proves a small of furnace which yields good steam-raising results, is in success- excess of free oxygen, and no doubt explains the high fuel effici0 era 0n obtained by this type of destructor. High-pressure boilers Meldrum’s Pp 0ti|- at Rochdale, and ofDarwen, e rum s. a^ ^. eac towns theHereford, production steam ency of ample capacity are provided for the accumulation during is an important consideration. Cells have also been laid periods of light load of a reserve of steam, the storage being down at Burton, Hunstanton, Blackburn, and Shipley. In obtained by utilizing the difference between the highest and Tipping platform

Steam Boiler

Beta wa

Ground line

Refuse is shove!led from opening into furnace. Fig. 3.—Meldrum’s Destructor at Darwen. lowest water-levels and the difference between the maximum and working steam-pressure. Patent locking fire-bars, to prevent lifting when clinkering, are used in the furnace and have a good life. At Rochdale the Meldrum furnaces consume from 53 to 66 lbs. of refuse per square foot of grate area per hour, as compared with 22'4 lb per square foot in a low-temperature destructor burning 6 tons per cell per 24 hours with a grate area of 25 square feet. The evaporative efficiency of the Rochdale furnaces varies from I'SQ lb to 1'87 lb of water (actual) per 1 lb of refuse burned, and an average steam - pressure of about 114 Eb per square inch is maintained. The cost of labour and supervision amounts to lOd. per ton of refuse dealt with. A Lancashire boiler (22 feet by 6 feet 6 inches) at the Sewage Outfall Works, Hereford, evaporates with refuse fuel 2980 lb of water per hour, equal to 149 indicated horse-power. About 54 lb of refuse are burnt per square foot of grate area per hour with an evaporation of 1 ’82 lb of water per pound of refuse. At Darwen a Meldrum furnace of 104'5 square feet grate area runs the present electric plant consisting of two 150 kilowatt steam dynamos (225 horsepower each), one only being in use at a time. As the dynamos run only 9J hours per day, while the refuse is burned throughout the 24 hours, there is a large surplus of heat running to waste. This it is proposed to employ for electric tramways and then the available power will be1 utilized to its full extent. The Beaman and Deas destructor (Fig. 4) has attracted much attention from public authorities, and successful installations are in operation at Warrington, Dewsbury, Leyton, Canterbury, Llandudno, Colne, Streatham, Rotherhithe, and ana eas. Wimbledon. Its essential features include a level firegrate with ordinary type bars, a high - temperature combustion chamber at the back of the cells, a closed ash-pit with forced draught, provision for the admission of a secondary

air-supply at the fire-bridge, and a firebrick hearth sloping at an angle of about 52°. From the refuse storage platform the material is fed into a hopper mouth about 18 inches square, and slides down the firebrick hearth, supported by T-irons, to the grate bars, over which it is raked and spread with

the assistance of long rods manipulated through clinkering doors placed at the sides of the cells. A secondary door in the rear of the cell facilitates the operation. The fire-bars, spaced only ^ inch apart, are of the ordinary stationary type. Vertically, under the fire-bridge, is an air-conduit, from the top of which lead air blast pipes 12 inches in diameter discharging into a hermetically closed ash-pit under the grate area. The air is supplied from fans (Schiele’s patent) at a pressure of from 1J to 2 inches of water, and is controlled by means of baffle valves worked by handles on either side of the furnace, conveniently 1 Patents No. 15,598 (1893) and 23,712 (1893); also Beaman placed for the attendant. The forced draught tends to keep the bars cool and lessen wear and tear. The fumes from the charge and Deas Sludge Furnace, patent No. 13,029 (1894).