1914] on Surface Combustion 58 



large industrial furnaces. Indeed, the new conditions of heating are 

 so radically different from the old, that a new experience has to be 

 built up. There are problems connected with the proper feeding and 

 distribution of gaseous mixture, with the dimensions and arrangement 

 of the combustion beds, and with the refractiveness of the furnace 

 walls, which have to be solved. Nevertheless, judging from reports 

 that reach me from time to time, substantial progress has been made 

 in the direction of gas-fired crucible furnaces for brass and aluminium 

 melting, annealing furnaces, and forging furnaces, the latter fired 

 with producer gas with regeneration of gas and air. Some large 

 annealing furnaces (for example, Fig. 8) are now running satis- 

 factorily in industrial establishments on both Mond gas and town 

 gas, and I understand that brass melting can be carried out in 50 to 

 60 lb. charges in tilting crucible furnaces with the remarkably low 

 consumption of about 1*75 cub. ft. per pound of metal melted and 

 poured. 



Surface Combustion as Applied to Steam Raising. 



I now come to an important application of the new process to the 

 raising of steam in multitubular boilers ; not that the application of 

 surface combustion is limited to boilers of the multitubular type, but 

 because our investigations have so far been principally made with 

 these. 



It is well known that the gas-firing of steam boilers has not been 

 very successful from the point of view either of thermal efficiency or 

 of rate of evaporation. In this country the gases available for steam- 

 raising purposes on a large scale are principally (1) blast furnace gas^ 

 of which there are large surpluses available in all iron-smelting areas ; 

 ( 2) the surplus gas obtainable during the manufacture of coke in by- 

 product ovens ; and (3) producer gas of various compositions, but 

 more particularly that manufactured under ammonia recovery 

 conditions. In the United States, and some other oil-producing- 

 countries, natural gas of high calorific power is also available. All 

 these gases have been found to be amenable to the system I am 

 about to describe. 



It has been estimated by a prominent British blast furnace 

 engineer that the thermal efficiency of the best type of water-tube 

 boiler, fired by blast furnace gas, does not exceed about 55 per cent., 

 whilst in the case of boilers fired by coke oven gas the average thermal 

 efficiency probably does not much exceed 65 to 70 per cent. But on 

 applying the principle of surface combustion to the gas-firing of 

 multitubular boilers we have been able to obtain results with coal gas 

 corresponding to the transmission of nearly 95 per cent of the net 

 calorific value of the gas to the water in the boiler. 



Our first experiments in Leeds were made with a single steel tube 



