754

THE COLLIERY GUARDIAN.

October 20, 1916.

alteration's in the boiler and in the ratio of grate area to
heating surface are needed.

For reasons “of economy, it is always advisable to try
and keep the flue gas temperature down to a moderate
level; and the simplest way of doing -this is by either
increasing the active heating surface of the boiler, and
thereby improving the heat absorption capacity, or else
by arranging so that, with a given heating surface, the
zone of greatest activity is exposed, as fully as possible,
to direct radiation from the grate area. Whilst the
former method is not always practicable when a grate
intended for burning coal is in question, the second can
frequently be carried out by a suitable regulation of the
draught, so as to expose as many of the rows of water
tubes as possible to the direct radiation from the grate.
By this means the transmission of heat in these tubes
is augmented, and the combustion temperature in the
firebox is lowered, with the result that the temperatures
of the superheater and the flue gases are reduced.

The removal of the cover from the bottom row of
tubes was contemplated, but regarded as undesirable,
because of the necessity of compelling the producer gas,
formed in the shaft and at the front end of the grate,
to travel over the glowing fuel, and thereby become
ignited instead of passing away partially unconsumed.
Trials are to be made with a view to accomplishing the
same result by means of a long ignition arch over the
front portion of the grate : a measure which would
enable gassy coals to be used in place of coke, when
necessary, without entailing any modification of the
grate; and eight boilers at the Essen power house are
now being rebuilt on these lines, with the Steinmuller
swinging baffle shown in fig. 2. This baffle consists of
a number of water cooled members, arranged like a
series of grate bars, so as to admit secondary air at the
rear end of the grate, and allow of the complete com-
bustion of the gases there. It is also expected that the
higher temperature at this end of the grate will prevent
the formation of the large masses of clinker hitherto
met with.

LETTERS TO THE EDITORS.

The Editors are not responsible either for the statements
made, or the opinions expressed by correspondents.

All communications must be authenticated by the name and
address of the sender, whether for publication or not.
No notice can be taken of anonymous communications.

As replies to questions are only given by way of published
answers to correspondents, and not by letter, stamped
addressed envelopes are not required to be sent.

MINING SURVEYORS’ EXAMINATIONS.

Sirs,—With further reference to the recent corre-
spondence on the above subject, and more particularly
to the improvement in the status of mining surveyors
in general, I was very disappointed to notice that this
correspondence, which appeared at one time to create
a certain amount of interest, has now been lost sight of
during the last few weeks.

I am sure, as some of your correspondents have
pointed out previously, that the formation of an insti-
tute for mining surveyors would not only improve the
status of surveyors, but would be the means of
exchanging various views and experiences gathered in
the coal fields of the United Kingdom.

Although the formation of a sub-division of the
Surveyors’ Institution of London for mine surveyors is
a step in the right direction, the distinction (after pass-
ing the intermediate and the final examinations) does
not improve the official standing of the surveyor.

What is required is a union or institution which will
not only promote interest in mine surveying as a
separate branch of mining work, but incidentally make
it worth while.

From the tone expressed in your correspondents’
previous letters on the subject, it only requires a little
stimulus to bring this institution into being, as all
mining surveyors who are anxious to improve their lot
(and I know there must be many) will be only too glad
to take advantage of such an institution formed for their
especial benefit.

Is it not possible to circularise mining surveyors,
pointing out the benefits to be derived from an institu-
tion of this character? Personally, I am quite pre-
pared to help in such an undertaking.

I shall be pleased to see further correspondence and
suggestions relative to the above subject.

Qualified 1913.

Partnership Dissolved.—The London Gazette announces
dissolution of the partnership of W. B. Shadrack and T.
Mileham, trading as Shadrack and Mileham, coal merchants
and carmen, 27, Dock-road, Silvertown.

Conference Arrangements.—No fewer than 3,000 represen-
tatives of the mining industry of Great Britain have been
invited to meet the Prime Minister at a conference at the
Central Hall, Westminster, on Wednesday, 25th inst. These
representatives will include employers as well as miners and
other workers from every pit in South Wales, North Wales,
Staffordshire, Leicestershire, Derbyshire, Yorkshire, Lanca-
shire, Northumberland and Durham, and the Scottish areas.
The Prime Minister’s speech, it is understood, will embody
certain important and exceptional proposals, already dis-
cussed by the leaders among employers and miners with Lord
Milner, and now presented to Mr. Runciman, President of
the Board of Trade. It is stated that the conference may
consider and decide on the following for the period of the
war :—Suspension or variation of the eight hours day; fixed
wages and prices by voluntary arrangement or Government
arbitration; an “ arrest ” of coal prices and a limitation of
profits in the national interest; local arrangements to reduce
absenteeism and for stereotyped holidays; increase of women
labour at the pithead and further employment of boys.

CURRENT SCIENCE

Wick Cover for Safety Lamps.

Dobbelstein (Gliickauf), referring to the loss of benzine
in safety lamps, by evaporation, when the lamps have to
stand, for some time in the lamp room after being got
ready for a shift, recommends the •wick cover illustrated
in the drawling, in which fig. 1 is a vertical section, fig. 2
showing the cover closed, and fig. 3 the cover open. The
cover consists of a leather-lined hemispherical cap a,
which fits closely round the end of the wick duct b. This
cap depresses a plunger c, making contact with a spring
d, which is compressed in closing the lamp. On the
igniter being operated, the pin e on the latter slides away
from the nose /, and releases the spring d. When the
lamp is recharged for the next shift, the wick cover is

O

O

O

< O

Fig. 1.	Fig. 2.	Fig. 3.

forced down again into position by finger pressure. This
simple device can be attached to any existing lamp
without much trouble or expense, and without affecting
the lamp fittings or the lighting power. It also obviates
the commonly experienced inconvenience that when
lamps have been standing for some time after filling, the
vapours of benzine collect inside the glass and gauze and
produce a slight explosion at the first attempt to light the
lamp, the flame being extinguished and a sooty deposit
formed on the glass and gauze.

Determination of Benzol in Coke Oven Gas.

The results of an investigation of a method proposed
by the United States Bureau of Mines (Laboratory of
Gras Investigation) are given by Mr. Louis C. Whiten
in the Journal of Industrial and Engineering Chemistry,
The apparatus consists of a bulb about Gin. long, with
a slight constriction in the centre. The upper portion
of the bulb contains glass wool mixed with phosphorus
pentoxide to extract all the moisture from the gas. Con-
nected with this bulb is a mercury manometer and an
entry and exit tube with a ground glass three-way cock.
The air is first evacuated by means of a vacuum pump;
the gas to be tested is sucked in, and the three-way cock
turned when the gas is under barometric pressure. The
entire bulb is then placed in liquid air or in a mixture
of CO2 snow mixed to a consistency of slush with alcohol
or acetone. It is allow'ed to remain there 10 minutes at
about — 78degs. Cent. The benzol freezes out at this
temperature, and the CO2, O2, CO, H2, CH4, N2, and
C2H4 are evacuated by means of 'the vacuum pump, the
cock turned off, and the apparatus raised to room
temperature. The partial pressure of the benzol vapour
is registered on the manometer, and this result divided
by the barometric pressure x 100 indicates the per cent,
of benzol.

Several difficulties had to be overcome in order to fit
the method for commercial work. With this object, the
mercury manometer was connected by means of a short,
heavy piece of rubber tubing, and was placed at a 10
to 1 slant, i.e., 10 on the hypotenuse to 1 of altitude.
This was placed on a firm gauge stand, and levelled
with spirit levels both ways. The gauge then gave a
reading 10 times the actual pressure. Thus it was pos-
sible to determine the pressure within 0’1 mm., which
was sufficiently accurate. The bulb was laid horizon-
tally in a trough with a notch at the end, through which
the stem of the apparatus could pass. In this position
it could be more easily surrounded with carbon dioxide
slush without danger of breakage of the bulb, and with
greater economy in respect to the slush. This trough
was 8 in. long, 24 in. deep, and 2| in. wide, with a
hinged cover and double walls, with the air evacuated.
It was found difficult to make this vacuum chamber
absolutely tight, so a pet-cock was soldered on, and
frequently the vacuum was attained again by means
of the pump. This trough saved considerable cost in
CO2 and alcohol, preventing the former from being
melted by the heat in the room to a considerable extent,
and enabling one to collect all of the alcohol after the
determination by allowing the CO2 to vaporise off. The
P2O5, which soon ceased to be active in respect to water
vapour, necessitated cutting the tube leading from this
bulb and connecting the two pieces by means of rubber
tubing. In this way fresh P2O5 and glass wool could
be easily inserted.

The following results were obtained with the apparatus
on coke oven gas:—

Gas A (duplicates). GasB (duplicates).

^741’0 ...741’0

Bar. pressure, mm....... 742’0 ...742’0 ...

Partial pressure benzol

vapours ................. 5’4	... 5*2 ...

Per cent, benzol in gas... 0’729... 0’702 ..

1’8 ...

0’243...

1’9

0’256

The author says, further, that benzol scrubber
efficiency does not call for absolute benzol determina-
tions, comparative results before and after scrubber
being sufficient. Therefore, it is not necessary to have
the manometer as carefully levelled as otherwise.
Efficiency of scrubbers with the above results averaged
would be determined thus :—

^100 — X 100 = 651 per cent.

The extreme results on the above tests would indicate
66-7 and 63’7 per cent, efficiencies.

AND TECHNOLOGY.

The use of this method in determining absolute benzol,
toluol, and solvent naphtha gives lower results than are
obtained by absorption methods, the average being 24
per cent, less than the amount obtained in actual prac-
tice. Benzol has a sufficiently low vapour pressure at
— 78degs. Cent, to ensure that it is completely con-
densed; about toluol there appears to be some doubt;
and about solvent naphtha there appears to be little
known, as its composition varies in different plants.

With an actual recovery during the period of one
month of 2-20 gals, per net ton of coal carbonised of
benzol + toluol + solvent naphtha, the average of
many results determined by this apparatus indicated an
amount equal to 1’70 gals, per ton coal, or 22-7 per cent,
low. The recovered hydrocarbons in practice consisted
of : 90 per cent, benzol, 67’5 per cent.; crude toluol, 19-3
per cent.; solvent naphtha, 13-2 per cent.

Recovery of Nitrogen at Coke Ovens.

A suggestion is put forward by a writer in the Gas
World for increasing the total yield of ammonia from
coke ovens by heating the ovens with producer gas made
from coke breeze, inferior fuel, and the like. This class
of material, under proper conditions, will yield as much
as 40 to 50 lb. of sulphate of ammonia per ton of coal,
and a good producer gas of calorific value of 120 to 140
British thermal units per cu. ft. An enormous quan-
tity of inferior material is necessarily brought to bank
at all collieries, and there are very few coke oven plants
which in normal times do not waste as much coke breeze
as would meet the whole of their requirements in the
producer gas department. It should not be difficult to
adapt the existing coke oven by-product recovery plant
to deal with the producer gas as well. Assuming that
the calorific value of the coke oven gas used for heating
the ovens is 500 British thermal units per cu. ft., and
that of the producer gas 125 British thermal units per
cu. ft., the volume of the producer gas required to
replace the coke oven gas will be about four times the
latter. Taking a plant carbonising, say, 500 tons of coal
per day in regenerative ovens, yielding 10,000 cu. ft. per
ton and 50 per cent, surplus gas, we get as the volume
of gas required for heating the ovens 2,500,000 cu. ft. of
a calorific value of 500 British thermal units per cu. ft.
Replacing this by producer gas of 125 British thermal
units, assuming an exact calorific equivalent, we should
require 10,000,000 cu. ft. of producer gas. If the gas
were made from coke breeze, belt pickings, etc., under
the usual recovery conditions, we should have a gas
yield of approximately 100,000 cu. ft. per ton (with a
good class of producer coal this -would be 140,000 cu. ft.),
which means that we should require 100 tons of the
inferior material per day for gasification in the gas pro-
ducer plant. The better the material used, the larger
the yield of by-products. If a yield of 40 lb. of sulphate
per ton of gasified material were obtained, the average
for the whole plant would be considerably increased.

This scheme, in its entirety, could not, of course, be
adopted on any coke oven plant without some modifica-
tion of existing arrangements. The exhausters, for
example, would probably need to be enlarged to deal
with the additional volume of gas, and coolers, also,
would need to be enlarged. At the same time, there is
no reason why the scheme should not be incorporated
to a less extent—say, to gasify 10 tons of breeze, etc.,
per 24 hours. The producer gas could be led into the
coke oven gas at some suitable point between the ovens
and by-product plant. On the basis outlined above, we
have, without producer gas, 5,000,000 cu. ft. of coke
oven gas of calorific value 500 British thermal units per
cu. ft. Gasifying the 10 tons of inferior material would
add only 1,000,000 cu. ft. of producer gas of a calorific
value of 125 British thermal units. After mixing, we
should have 6,000,000 cu. ft. of gas of an average calorific
value of 438 British thermal units, approximately. All
existing gas firing arrangements could be used with such
a gas, and a slight increase of gas pressure at the ovens
would be the only alteration necessary to maintain the
heat of the ovens. The existing exhausters, by-product
plant, etc., would easily deal with the additional 20 per
cent, of gas. One small gas producer would deal with
the 10 tons of material, and would require little atten-
tion. From the ammonia point of view, from the coke
oven gas we should obtain, say, 30 lb. of sulphate per
ton of coal, or 15,0001b. per day in all. From the pro-
ducer plant 400 lb. would be a moderate estimate of the
yield, so that the average would be brought up to nearly
31 lb. per ton, which would make a considerable differ-
ence at the year’s end. The value of the producer gas
alone for fuel purposes would more than pay for the
cost of working the producer.

Effect of Storage on Gas Coal.

Prof. A. H. White, of the gas experiment station of
the University of Michigan, has reported (says Gas
World) on the results of experiments, extending over
five years, on the effects of storage on the gas making
qualities of coal. Pittsburg and Fairmont gas coals
were tested, the coals being piled 7 to 9 ft. deep in
bins with separate compartments, and left untouched
until the time came for the individual compartments to
be tested. The temperature of the coal in the pile
was measured during the first few months, and no
spontaneous heating was detected. The coals were
exposed freely to all the effects of the rather damp
climate of Southern Michigan, where the winters are
severe. The main body of the coals suffered little
physical change during the five years, but the top 6 in.
crumbled considerably. Chemical analysis failed to
reveal any material change even in the top layer, nor
was there any material change in the absolute weight of
the coal. The retort tests were made in one retort of
a bench of six in regular use, this retort holding about
4001b. of coal, and being connected to the condensing