172 SECTIONAL ADDRESSES. 



Boilers are already in commission with an evaporative duty of 300,0001b. 

 per hour. For pressures of 800 lb. and over it is necessary to avoid 

 riveting and to adopt a seamless drum. With high evaporative duty 

 per square foot of heating surface, the de-aeration of the feed water 

 becomes of great importance, in order to avoid rapid corrosion of the tubes, 

 and in modern types especially, where pulverised fuel is used, the com- 

 bustion chamber is practically lined with tubes, so as to obtain as large 

 a tube surface as possible exposed to direct radiation. 



The tendency in boiler design for large power stations is unquestionably 

 towards higher evaporative capacities, larger boiler units, and higher 

 steam-pressures. 



The use of pulverised fuel appears to lend itself to these modern 

 requirements in capital stations, enabling better control to be exercised, a 

 higher thermal efficiency to be obtained, and less wear and tear of plant, 

 a better distribution of heat in the boiler, and therefore a better 

 evaporation. 



It is reported that at the Lake Shore Station, Cleveland, U.S.A., 

 boilers of 30,000 square feet heating surface and fed with pulverised fuel 

 are maintaining an average efficiency of 90.4 per cent. 



The utilisation of pulverised fuel also raises a larger question. Not 

 only is there a possibility of commercially utilising the waste from coal- 

 mines, but it would appear to bring within the ambit of possibility a 

 combination of some form of low-temperature carbonisation of the fuel, 

 so as to enable some of the valuable by-products to be recovered, coupled 

 with the production of a soft coke which can be applied in a pulverised 

 form to the boilers for steam-raising purposes. 



A practical application is now being made of the McEwen-Runge 

 low-temperature carbonisation plant to the Lakeside Power Station of 

 the Milwaukee Electric Railways and Light Company, Wisconsin, U.S.A., 

 the result of which will be awaited with interest, and if satisfactory should 

 be of great value to designers of future base-load stations. 



Suggestions have been made that gas and electricity undertakings 

 should be combined for the purpose of conserving fuel. It is significant 

 that although a large number of local authorities in Great Britain have 

 owned both gas and electricity undertakings for many years past, there 

 is no single instance of any such authority having effected a complete 

 amalgamation of its undertakings. There are a few cases where companies 

 operate gas undertakings in conjunction with electricity-supply under- 

 takings, but their total plant capacity is very small, and represents only 

 0.1 per cent, of all the generating plant installed by authorised undertakers 

 in the country. 



There can be no advantage to a gas undertaking unless the price at 

 which the gas or coke can be supplied to the power station shows a margin 

 over the costs incurred in producing the gas or coke ; nor is there an 

 advantage to the electricity undertaking unless the price paid for the coke 

 or gaseous fuel on an effective heat-value basis is at the best not greater 

 than the cost at which raw coal of equivalent heat value can be purchased. 

 The average price paid for coal by electricity undertakings between 

 1922 and 1924 was approximately 205. per ton. If we assume the average 

 calorific value as being 10,500 B.Th.U. per lb., there would be no economic 



