The "Heenan" Destructor.

Progress, Volume III, Issue 6, 1 April 1908, Page 192

The "Heenan" Destructor.

In the October number of Progress last year I gave a short description of the Wellington destructor plant, and also a few facts concerning refuse destructor installations in general. The purpose of this article is to supplement the first one and to give details of design, working, cost of working, and probable values of by-products, of the Wellington destructor. Briefly, a destructor of the present day is composed of two groups of apparatus : — The first, and more important part, includes {a) the cells, in which the refuse is burnt ; (b) the combustion chamber,

(u) 'exhaust steam feed heater ; (v) ventilating duct connected to fan ; {w an oven T for extracting solder from tin cans. While the first group represents the essentialfpart of the destructor, the second comprises the plant for dealing with the by-products to the fullest extent, and also several other refinements which make up a complete money-saving modern destructor. It is hardly necessary to add that the Wellington plant has everything to effect the greatest saving to the city, and make hygienic the conditions under which the men work. The*method of working the destructor can be followed by reference to the illustrations. The refuse is delivered into the building by means of an inclined road to an elevated covered

that 'the cill hampered the firemen, and in some cases they have been removed. In stoking a destructor the good fireman selects the refuse to obtain fires as uniform as possible, i.e., he is careful not to place, say, a mass of cabbage leaves in one cell, a mass of paper in the next, and ashes in the third. The results of care in this direction are uniform temperature in the combustion chamber and uniform periods between the clinkering of each cell, and consequent ease of handling the plant. By means of divided ashpits, continuous grates, and a properly controlled supply of hot-air blast, the moisture in theyrefuse is quickly expelled, and rapid combustion ensues. With refuse such

To more clearly understand what takes place in a destructor furnace it is necessary to touch, upon the chemistry of the subject. According to Mr. H Norman Leask, A.M.1. C.E., an Javerage analysis of superior refuse m Britain would be as follows :—: — Carbon 3G.8% Sulphur 0.19% Hydrogen 0.29% Oxygen 7.3% Nitrogen 0.29% Ash 41.7% Moisture 12.12%, with a calorific value of 4500, while ordinary British refuse would have a calorific value of 3000 B.Th.U. The whole success of a destructor Jscheme as a steam-raising project depends upon the accuracy with which the average composition of the refuse can be judged — not such an easy matter with a fuel like refuse, varying greatly in composition with every cartload, every shower of rain, and with each season of the year. Given the composition, the engineer must modify the design of the fan, boiler, air heater, and furnace to obtain the best results, and as it is usually impossible to obtain useful analysis of the refuse to be dealt with, the reader will understand the great value of wide experience in dealing with the question. Having estimated the amount of carbon and hydrogen in a given quantity of the garbage, it remains

In the second case there is very little harm done if the flue'gases show no trace of CO, with 5 /& to 8% of oxygen. Much more oxygen than this will soon affect the temperature of the combustion chamber, causing a considerable drop in temperature, in spite of the good appearance of the fires. For the purposes of this article we"will assume the very best conditions possible in the furnace, and that the analysis of the gases in the combustion chamber is : — CO2 19-8% by volume. CO 0.00% „ 0 0.00% „ N .... , 80.20% „ The above percentage of CO2 has never been obtained in practice, and were it obtained, the temperature in the furnace would be such (4000° F) as to melt the firebricks, and to fuse the flue dust into a solid mass, which would defy all attempts at removal from the combustion chamber. The flue dust will fuse at a much lower temperature than that probable with our analysis — in fact, it has been found that it is inadvisable to allow the temperature of the combustion chamber to rise above 2700° F. With an undulating arch, such as is used in the

The evaporation was 2.63 lbs. of water per ib. of refuse, from and at 212° P. In Wellington, where the refuse is of less calorific value than that obtained in the above case, the evaporation will probably be about 1J lbs. of water from and at 212° P. Let us see now what this means :—: — The present coal-fired boilers work with an evaporation of 8 lbs. of water per Ib. of coal, therefore, for every 5£ tons of refuse burnt in the destructor, enough steam will be raised to save 1 ton of coal, i.e., if the quantity of refuse brought to the destructor every day bs about 50 tons, it will be seen that, if all the power available from the plant be used, the price of 3420 tons of coal will be saved per annum, without reckoning the money saved by using the clinker for concrete material, instead of buying shingle. Shingle costs, say, 8s per yard delivered at Oriental Bay tramway terminus; crushed clinker would cost about Is 4d per yard delivered from the destructor to the same place. Clinker deli vered at Newtown would cost, say, about 2s 6d per yard, and shingle, at the very lowest price, say 6s 6d per yard. These figures are approximate only, but serve to show the great saving the use of properly crushed and screened clinker can effect.

neer, of Wellington. The foundations for the chimney comprise 42 ferro-concrete piles supporting a bed of reinforced concrete 6 feet thick. The method of reinforcing is by vertical bars in lengths of about 30 feet, with a substantial overlap. These are bound together by rings of round steel bars, at intervals of 18 inches, The thickness of the concrete varies from 12 inches at the bottom to 6 inches at the top. The deflection from the vertical when the chimney was oscillating in a heavy wind was found by the author to be only half an inch. The contractor for building the chimney was Mr. John Moffatt. In conclusion, I wish to express my indebtedness to Messrs. Morton and Hastwell for figures concerning the present destructor and the pumping plant, to Mr. Leask for particulars with regard to calorific values and analyses of refuse, and to Messrs. Heenan and Froude, Limited, for the photographs and diagrams. No_more telling figures than the following can be given" in support of Messrs. Heenan and Froude's claim that their back feed hand-fired destructor is the cleanest, cheapest, and most economical on the market.

DESTRUCTOR CONTRACTS ENTERED INTO BY HEENAN AND FROUDE, LTD., DURING 1907. New York (U.S.A.) . . Back 60 tons Vancouver (8.C.) . . . . „ 50 „ Victoria (8.C.) . . . . „ 50 „ Wimbledon .. .. „ 112 „ Cheltenham .. .. „ 60 „ Buxton . . . . „ 45 „ Redditch .. .. „ 45 „ Bury St. Edmunds „ 30 „ St. Albans . . . . Front 90 „ Paignton . . . . „ 30 „ Total tons .. .. 572

DESTRUCTOR CONTRACTS ENTERED INTO BY ALL OTHER MAKERS DUBfNG 1907. Exmouth . . . . Front 20 tons Hampton . . . . „ 20 „ Gainsborough . . . . „ 25 „ Sowerby Bridge . . . . „ 30 „ l/oughborough . . . . Top 15 „ Ilford .. .. .. „ 90 „ Total Tons . . . . 200