1212

THE COLLIERY GUARDIAN.

June 29, 1917.

what was likely to happen, or whether ignition pres-
sure temperature was lowered in the presence of
minute percentages of CH4. There were a consider-
able number of lamps in use under dangerous condi-
tions without any instance of any external ignition or
explosion having been produced by an acetylene safety
lamp.

Mr. Charles Bingham claimed indulgence for one
moment. He felt it incumbent on him to state that
acetylene was not a poisonous gas at all. If one turned
to almost any text-book on the subject, it would be
found that acetylene had been investigated from the
toxic point of view by some of the most eminent
authorities in Europe, including Berthelot; and he
might mention that the late Sir William Ramsay had
informed him that when he was working on that parti-
cular subject he put mice into an atmosphere of com-
mercial acetylene without any admixture of air or any
other gas, and (speaking from memory) the mice lived
for an hour and 40 minutes in the gas before they
died. As a matter of fact, acetylene gas was far less
poisonous in its nature than ordinary coal gas. With
regard to explosive properties, acetylene could not be
detonated at any temperature unless it was under
pressure of more than two atmospheres; but such a
pressure was, of course, never reached in a lamp ; and
it also required special apparatus in order to detonate
acetylene under those conditions.

The President said the discussion must now be
closed temporarily till the next meeting in Newcastle.

By-Product Coking.

The next item on the agenda, the paper on “ The
By-Product Coking Process: Its History, Develop-
ment, and Application,” by Mr. Ernest Bury, had to
be deferred owing to the inability of the author to
prepare the paper in time.

The Form and Structure of the Coal Fields of Scotland.*

In opening the discussion, the President said that
the paper covered a very wide field, and was of special
interest to Scotch members and those in the North of
England who had studied the carboniferous limestone
formation in that area. Mr. Ferguson had collected
and given the references to a great deal of informa-
tion on the subject of the pre-carboniferous floor on
which the rocks of the Scottish coal field were laid
down, but without the relative maps it was somewhat
difficult to follow the arguments, unless one was very
familiar with the geography of. the South of Scotland.
It had long been recognised that the coal seams in
the Scotch carboniferous limestone series were much
more local in their character than the coal seams in
the upper measures above the millstone grit, and that,
generally speaking, the limestone coals increased in
value from the south-western areas to the north-east.
He understood that, except in Northumberland,
where there were a few workable seams in the car-
boniferous limestone, that series of rocks was barren
in the rest of England. That seemed to indicate that
the conditions necessary for the creation of thick and
valuable coal seams were more favourable to the north
and east in the carboniferous limestone era. Dr. Dron
had pointed out, in the discussion of the paper at
Glasgow, that certain well-known positions, such as
the black metals with numerous bands of clayband
ironstone, often called Logan’s bands, and the Index
limestone, were persistent over practically the whole
explored area of Scotland, and that between those
two positions the bulk of the workable coals were
found. That was a strong point against the theory of
old ridges between each basin put forward by Mr.
Ferguson. It emphasised the desirability of further
study of the earth’s movements, which undoubtedly
were fairly active when those rocks were being laid
clown. Another important factor which must be taken
into account by anyone proposing further exploration
of this series was the vast intrusion of volcanic rock
in subsequent periods, which frequently altered and
sometimes destroyed the coals. Much information on
the subject was available from the writings of the
authors quoted by Mr. Ferguson, and nearly every
year bores were put down pushing the explorations
further into the concealed areas. The economic neces-
sities of the Clyde Valley would induce more proving
work in the carboniferous rocks of that district during
the next 10 years or so, and the more light that could
be thrown upon the probabilities the better. A most
excellent memoir on “ The Economic Geology of the
Central Coal Field of Scotland ” was published
recently, but it did not deal with either of the pro-
blems to which he had just referred. He would have
liked to inaugurate a discussion on the question of how
the coal seams were formed, but beyond saying that
he thought the facts to which Mr. Ferguson had drawn
attention were too few to prove his case in general, he
must leave it alone in the meantime. A good deal of
light would be thrown upon this vexed question if
surveyors and other underground officials would
accurately record numerous minutely-detailed sections
of the coal seams at regular intervals as the face
advanced in roads, say, 50 yds. apart, and plot their
sections to a vertical scale large enough to show the
details, including a few inches of roof and pavement.
He was certain that the Geological Survey Depart-
ment would be glad to get copies of such sections, and
in a few years a store of information would be collected
and made available to those best fitted to solve the
problem. It was the lack of opportunity for those
competent to observe and record the actual facts that
had delayed its solution. In his description of the
various areas of the Scotch coal measures, Mr.
Ferguson had omitted one small, but very interesting
outlier, viz., that to be seen on the north side of the
Sound of Mull, east of Loch Aline. There was but a
small area visible faulted down against the old gneiss
and overlaid by secondary and cretaceous strata. It
might be extended below the Sound, and possibly
under the island of Mull. He did not know to what
horizon in our coal measures this patch belonged, and
no outcrop of coal had been found, nor had any boring

* See Colliery Guardian, September 22, 1916, p. 545.

been done to prove it. Mr. Ferguson’s paper raised
many points, and suggested several subjects for
research when they had' more leisure to attend to such
matters. He invited discussion, but thought that if
they started debating the in situ or the other theory
of coal, they would be sitting all night.

Vote of Thanks to the President.

Mr. John Simpson (Monkseaton) said that before
they parted he would like to propose a vote of thanks
to the president for the able manner in which he had
presided over the meeting. Such a vote of thanks did
not really represent all that was due to him, because the
president had devoted a great amount of labour and
had given great help to the institution. He was sure
the members would accord him a very hearty vote of
thanks for his conduct in the chair that day, and also
for the great amount of attention he had given to the
interests of the institution.

Prof. Arnold Lupton having seconded, the resolu-
tion was carried by acclamation.

The President briefly returned thanks; and a vote
of thanks to the president and council of the Geological
Society for the use of their rooms, proposed by Mr.
William Williamson (Hamilton, N.B.), terminated
the proceedings.

FUEL ECONOMY.

In a paper on this subject, read before the Incor-
porated Association of Municipal Engineers . on
June 21, Mr. J. A. Robertson, borough electrical
engineer of Salford, discussed the possibility of econo-
mising fuel by centralising the production of power,
and by combining the carbonisation of coal and
by-product recovery with the generation of electricity.
With regard to the first point, the average consump-
tion of coal by electrical undertakings had been
reduced, during the last few years, from 3-9 lb. per
electrical horse-power-hour to 3-2 lb. (The average
calorific value of the coal might be taken as 12,500
British thermal units.) This figure, equal to 2-4 lb.
per horse-power-hour, represented a reduction of 52
per cent, compared with Sir George Beilby’s estimate
in 1905, and 37 per cent, compared with the average
consumption in central stations in 1907. This repre-
sented an annual saving of 1,750,000 tons of coal. A
considerable fuel saving could therefore be effected by
an immediate transference of the factory power load
from private plants to central stations.

With a consumption of 3*2 lb. per unit of fuel con-
taining 12,500 British thermal units per lb., the
thermal efficiency was only 8J per cent., but a much
higher efficiency was now possible. Several power
stations in the United States claimed an over-all effici-
ency of 17 to 18 per cent. Under a centralised system
of production operating with power stations equipped
with generators of 15,000 to 20,000 kw. capacity, com-
bined with water tube boilers of 10,000 kw. each, and
auxiliary plant designed and arranged so as to reduce
the heat losses to the absolute minimum, a continuous
thermal efficiency of 18-8 per cent, was possible. The
coal consumption on this basis would amount to 1-45 lb.
per kw.-hour sold, or 1'09 lb. per electrical horse-
power-hour. Taking the present consumption of fuel
for factory purposes as 44 lb. per horse-power-hour, the
possible saving was about 3| lb. of fuel, or nearly 75
per cent. Hence, if two-thirds of the factory load were
transferred from private power plants to central
stations operating under a national centralised scheme,
the saving in fuel to the nation would amount to about
22,000,000 tons per annum.

Reviewing the question of the possible extension of
electric heating for domestic purposes, the author
estimated that, if only 50 per cent, of the cooking and
heating for which coal was now used were performed
by electricity supplied from central stations, nearly
10,000,000 tons per annum could be saved, bringing
up the total saving to 30,000,000 tons per annum—suffi-
cient to meet the charges on the capital expended, and
also to compensate existing interests which might be
adversely affected. The benefit to the nation would be
so great as to justify the Government supporting a
centralised scheme of power production, and making
regulations to ensure its successful operation.

Linking Up.

The linking up of generating stations would permit
the capacity of existing stations to be more fully
utilised to meet the increased demand for power after
the war, and also save fuel by enabling the more effi-
cient plants to be fully utilised, shutting clown the less
efficient plants during the night, at week-ends, and
other times of light load. In the case of 26 Lanca-
shire undertakings, the Inter-connection Committee
estimated that the average fuel consumption per unit
sold could be reduced 25 per cent., representing a
saving of 110,000 tons per annum. Linking-up pro-
posals must, however, be considered with relation to
the bigger scheme of centralisation.

With regard to the suggestion that, in order to
obtain the highest economy, a universal system of coal
carbonisation should 1 be adopted, combined with
by-product recovery, it was well known that from the
point of view of thermal efficiency the carbonisation
of coal in gas works was more efficient than burning
in central power stations—65 tQ 70 per cent, as com-
pared with 8 or 9 per cent. — although some large
power stations obtained efficiencies of between 12 and
15 per cent. On the other hand, electricity was
superior to gas in the higher efficiency for industrial
purposes. From this it was deduced that if the high
thermal efficiency of carbonisation could be combined
with the efficient application of electricity, the econo-
mical utilisation of fuel would be ideal. This, how-
ever, left out the question of by-products. There was
no direct economy in carbonising coal for producing
gas to be utilised for firing boilers; and the whole
question turned on the value of the by-products pro-
duced. Before any general scheme of coal carboni-
sation was adopted, it would be necessary to ascertain

if there was a permanent and remunerative market
for these products. If cheap electricity would lead to
its universal adoption, it would be a mistake to car-
bonise coal with the sole or primary object of produc-
ing a smokeless fuel for domestic purposes.

To obtain the highest possible efficiency in power
production from carbonisation involved the employ-
ment of internal combustion engines. The high
thermal efficiency of gas engines (about 27 per cent.)
had often attracted power engineers, but their higher
capital cost, the increased labour and maintenance
charges, and lesser reliability as compared with either
steam engines or steam turbines, had proved deciding
factors against their general adoption. Even in point
of efficiency, the steam turbine in large sizes had
almost overtaken the gas engine, and it was doubtful
if the best results obtained in practice with any type
of gas producer internal combustion engine plant
equalled those with steam turbines and direct-fired
boilers. In smaller sizes (up to 1,500 horse-power) the
gas engine had still a field for employment in connec-
tion with coke oven installations, where the surplus
gas was a by-product, and where the demand for power
was relatively small in proportion to the amount of
coal to be carbonised for coke ; but for generation on
the scale required in a centralised power scheme they
might be left out of account.

Producer Gas and Coke Oven Gas.

Apart from the carbonisation of coal in gas works,
two systems might be considered — producers of the
Mond type and coke oven plants. The thermal effici-
ency of a Mond producer employed solely for the pro-
duction of gas was about 65 per cent., but if employed
with by-product recovery, the efficiency was lower
(about 57 per cent.) owing to the large amount of
steam.

Low temperature distillation of coal for producing
metallurgical coke, surplus gas of high calorific value,
and other by-products, had been advocated as a solu-
tion of the fuel economy problem. Hitherto the
industry had been confined to steel works and collieries
—where its advantage was unquestioned — but the
importance of the by-products recovered and the possi-
bility of utilising the surplus gas had drawn attention
to the possibility of combining low-temperature distil-
lation with the production of power. The amount of
surplus gas was equal to 4,000 to 5,000 cu. ft. per ton,
and the calorific value 550 British thermal units per
cu. ft. The cost of the plant, however, was very great,
and the coal consumed to produce a given amount of
heat in the form of surplus gas was about 12 to 14
times as much as would be required for direct firing.

As a means of producing power, the coke oven could
only have a limited application. The demand for
electricity in the form of light, power, and heat, was
certain to exceed enormously the demand for coke and
by-products, and while the surplus heat from coke
oven gas should be fully utilised, either in independent
power stations or in conjunction with larger power
systems, the process could not be regarded as more
than a partial solution of the fuel economy problem.

It was claimed that low-temperature carbonisation
would furnish a soft smokeless fuel suitable for
domestic purposes, and proposals had been put forward
to combine an installation for producing such fuel
with a central power station, the surplus gas being
consumed under the boilers. The author, however,
believed that such an arrangement could have only
local and temporary application, and that the burning
of fuel for domestic purposes must ultimately be super-
seded by electricity.

Gas Firing for Boilers.

Opinions differed greatly regarding the efficiency of
gas-fired boilers, some placing it as low as 75 per cent.,
while others claimed 85 or 90 per cent. Prof. Bone
had given an efficiency of 92-7 per cent, for the Bone-
court surface combustion boiler and 75'1 per cent, for
the coal-fired boiler. Assuming an efficiency of 90 per
cent, for gas firing and 80 per cent, for direct coal
firing, the combined efficiency of the gas-fired producer
with by-product recovery and the gas-fired boiler would
be 51-3 per cent. In other words, for every 100 tons of
coal consumed for direct firing, 155 tons were needed
to produce the same amount of heat from boilers fired
with producer gas, against which there were recovered
4 per cent, (by weight) of sulphate of ammonia and
4 per cent, of tar.

It would be interesting to ascertain whether the
high thermal efficiency of the surface combustion
boiler could be maintained in continuous operation,
and whether the maintenance costs’were higher or
lower than for coal-fired boilers operating under
similar conditions. One advantage of gas firing was
the cleanliness of the boiler house and the better con-
trol of the fuel supply. There should also be a slight
reduction in the labour and maintenance costs. On
the other hand, the efficiencies claimed for gas pro-
ducers were possible only with a high load factor, and
in central stations it would mostly be necessary to
supplement gas firing with coal-fired boilers for dealing
with fluctuations of load.

It was apparent, therefore, that the whole case for
gas firing from producer plant rested on the produc-
tion of by-products; and the author gave an estimate
of what might be expected from a producer gas fired
boiler installation of 20,000 kw. capacity, dealing with
a maximum demand of 15,000 kw. and operating with
a 40 per cent, station load factor. With direct firing
(boiler efficiency 80 per cent.) and generating
53,000,000 units at 21b. of coal per unit generated,
48,000 tons of coal, costing (at 15s. per ton) £36,000,
would be required. A gas producer and gas-fired
boiler with by-product recovery (boiler efficiency 90
per cent., and combined efficiency 52 per cent.) would
consume 74,000 tons of coal, to the value of £55,500.
The cost of acid, extra labour on gas plant, extra
stores, extra labour on by-product recovery (includ-
ing bagging sulphate of ammonia), and interest,
depreciation, and maintenance on cost of producer and
recovery plant (15 per cent, on £52,000), would bring
the total cost up to £78,195; but, on the other hand,