SCIENCE AND INDUSTRY. 
light, or power—are so fully appreciated that demand will continue to 
cutpace supply until soaring prices impose the. economic limit to its 
employment. é' 
If it is admitted that coal must continue to be our main source of 
energy, it will be granted also that it has been wasted in the past; yet 
the particular improvements to be adopted are subject to acute con- 
troversy. It is apparent that great economies are practicable by super- 
s¢u.ng the multitude of small steain plants in existence by large central 
power-stations generating and distributing power electrically over 
urban areas. or such large stations, most engineers are agreed that 
the steam-turbo generator has quite outdistanced the gas-engine in size 
of units, capital, and running costs and reliability. At the same time, it 
should be noted that by combining waste-heat boilers feeding turbines 
with the gas-engine exhaust the thermal efficiency can be raised to 25 
per cent., as against 18-20 per cent. for the largest size of steam 
turbines. 
A further point of controversy relates to the practice of direct 
coal-firing of boilers. It has been frequently asserted that great 
economies are possible by first carbonizing coal, as in gas-works practice, 
recovering valuable by-products, using gas for direct heating, and pro- 
ducing steam for electricity generation from the coke residue. The most 
authoritative report on these modes of utilizing coal for the needs of a 
large power-station with 100 per cent. load-factor is that of the Nitrogen 
Products Committee. Their conclusions may be summarized thus:— 
1. Carbonization of coal—as practised in gas-works or coke-oven 
works—or, alternatively, the complete gasification of coal 
in producers (with ammonia recovery), offers no immediate 
prospect of reducing the cost of electrical energy from coal 
below that obtainable by direct-firing of boilers. 
2. The main hope of cheaper power from coal appears to reside 
in the carbonization of coal at a low temperature, but a 
successful commercial tyne of plant has not been in opera- 
tion. : ; 
3. In the present state of the art, the employment of gas-engines 
for large-scale power production is not economical; for 
moderate blocks of power, however, up to (say) 6,000 kilo- 
watts, the gas-engine can easily compete with steam-turbo 
plant of corresponding size. , 
-The above report was written in 1918. Meantime, circumstances 
lave arisen which will force reconsideration of carbonization and gasi- 
fication of coal in relation to fuel economy. 
Along with increasing demands for motor spirit and fuel-oils— 
with corresponding stiffening of prices—the yields of oils obtainable by 
modern methods of carbonization of coal have almost doubled within that 
period. We are within sight of an economical method of producing 
still larger quantities of such oils from coal, together with a respectable 
gas production.~ Besides this development, processes are emerging for 
the complete gasification of coal in a single operation to produce gas 
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