744

THE COLLIERY GUARDIAN

April 12, 1918.

the mining industry, a strong effort should be made to
secure the desired results in some such way.

The Time Margin.

A further point was the margin of time between the
average daily and weekly hours of employment, and the
ten hours per day and 54 hours per week permitted by
section 92 of the Coal Mines Act 1911. There appeared
to be a margin of II to 2 hours per day, but only a
maximum of seven hours on a six: days week. It might
be noted that this restriction did not apply to boys
between 16 and 18 years of age.

In considering the possibility of the continuation
classes being held in addition to ordinary working hours
it was found that the margin was uncomfortably small,
but it might have been possible to have classes for 1|
hours on five afternoons or evenings per week, except
for the very loose and indefinite phrase “ including
time for travelling.” This phrase reduced the margin
to an unworkable point and in effect meant that educa-
tional time must be taken out of ordinary working time.
The Eight Hours Act did not directly affect the con-
sideration, but it might be noted that one of the
principal reasons for thus shortening the hours of
labour in mines was the desire to provide more oppor-
tunity for recreation and study.

Hours of Instruction.

A point arose as to the period between 8 a.m. and
7 p.m. during which continuation classes were to be
held, and whether this was sufficiently long. If daily
instruction were given from 5.30 till 7 p.m. no
extension would be necessary, but it might be more
suitable for the scholars if these classes were held
between 6.30 and 8 or 8.30 p.m. in order to extend
the interval between leaving work and attending
school. The evening classes which were now
held in technical schools extended in cases to 9 p.m.,
and the author was not aware that even this hour put
any undue strain on the student. It was understood
that the intention was to establish schools for continu-
ation classes in every community of any size, and that
there would be few, if any, cases in which students
would have any considerable distance to travel to and
from any schools. As section 17 stood at present it
would seriously affect the mining industry. The con-
cession of one whole day’s attendance at classes per week
in place of daily instruction did not appear to meet
the special circumstances of the mining industry nor of
education, and he (the author) thought a strong effort
should be made to have the continuation classes held
after and in addition to ordinary working time. It

that had ever been contemplated. It was a measure
which if passed in its pi esent form would entail a
considerable hardship on working class people who were
rearing families.

On the suggestion of the President it was agreed to
resume consideration of the provisions of the Bill at
the next meeting of the institute.

THE BY-PRODUCT COKE OVEN IN THE
UNITED STATES.*

By W. H. Blauvelt.

The technical and engineering problems in the
manufacture of coke are to-day the problems of the
by-product oven. Except in a few special localities,
practically no beehive ovens have been built in the
United States for the last five or six years except
as renewals of old plants, and during these years the
total number of beehive ovens in existence has been
steadily falling. On the other hand, the number of
by-product ovens has increased from 4,624, in 1911,
to a total of about 7,660 in operation at the end of
1917; with 2,800 building, this makes a total of about
10,460 which will be in operation in 1918, or shortly
thereafter.

Preliminary Government estimates place the total
production of coke for 1917 at 56,600,000 tons, the
largest tonnage in the history of the industry. Of
this, 34,000,000 tons, or 60 per cent., was beehive,
and 22,600,000 tons, or 40 per cent., was by-product
coke. Some time in 1918 the production of by-product
coke should pass the beehive output, and when the
by-product ovens now building are completed the total
by-product capacity will be about 40,000,000 tons of
coke per annum, which is over 70 per cent, of the
record-breaking total coke production of 1917. The
reasons for these changes in the coking industry are
familiar to all of us, and need not be discussed here.

Improvement in Oven Design.

Since the by-product oven was introduced from
Europe, in 1892, it has been radically improved, and
from the point of view of American metallurgical
practice it is safe to say that the American ovens
are superior to those of Europe. The points of
superiority are mainly those of larger units and larger
output per unit, and the greater extent to which
labour-saving machinery has been, introduced. The

consists of a chamber about 36 ft. long, 12 ft. high,
and of a width depending upon the coal that is to
be carbonised. In American practice the average
width varies from 16-5 to 21 in. Modern ovens
generally have about 2 in. of taper toward the
discharge end to facilitate the pushing of the coke.

The ovens are usually heated by a portion of the
gas recovered from the distillation of the coal,
although sometimes producer gas is substituted. In
all the successful ovens this gas is burned in a series
of flues which control the travel of the burning gases
and distribute the heat over the entire side of the
oven. The success of any oven design depends very
largely upon its ability to distribute the heat evenly
over the entire surface which forms the wall of the
oven, and it is by no means an easy problem to
control this distribution accurately over an area of
432 sq. ft. In some ovens the flues composing the
heating system are vertical and in others horizontal.
The oven shown is the chief exponent of the latter
arrangement.

Both systems have their advocates, and the details
of both have been worked out so that they can be
relied upon to give the uniformity of heating neces-
sary for satisfactory operation. The advocates of
the horizontal flues find them more accessible for
supervision, easier to control, and easier to maintain.
The somewhat lower temperature that can be main-
tained in the upper flues under all conditions of
operation is a desirable feature for the best results.
One feature of the oven shown is the strong middle
wall between the ovens extending from the foundation
to the top, which gives the structure great stability
and permanence and acts as a heat reservoir to help
maintain uniform temperatures. This is important,
because when a new charge of cold, wet coal is dropped
in the oven there is a great demand for heat to
start the coking process quickly. These middle walls
also permit any oven to be repaired or entirely relined
with a minimum interference with adjacent ovens.

Heating the Oven.

Fig. 3 shows the flow of air and gases through the
system. From this illustration it will be noted that
one pair of dampers near the stack does all the
reversing of the air and gas. The cold air enters
the system from a fan located at a point near these
dampers, flows through one of the two main flues,
and is distributed to the regenerators by a system of
firebrick slides. The air is heated in the regenerators
to about 1,000 to 1,100 degs. Cent, before entering the

Fig. 2.



might be helpful to the mining industry if, after the
matter had been thoroughly discussed and a definite
conclusion come to, a deputation from the institute or
the council were to seek an interview with the Secretary
for Scotland and place its views before him.

DISCUSSION.

Mr. Robert McLaren (Airdrie) said this Bi'l had
aroused a good deal of feeling amongst many people in
Scotland, who regarded it as a very serious matter that
the half-time system should be introduced into that
country. Altogether it was a most curious matter that
the authorities should be seeking to introduce this half-
time principle into Scotland at a period when they were
actually abolishing it in England. From the point of
view of the parent this Bill would be an undoubted
hardship, and as an institute they ought to protest
strongly against the raising of the school age. There
were jobs about the pits that boys could do
infinitely better than many men, and one effect
of the present contemplated educational legisla-
tion for Scotland would be to close the pits
against lads until they reached 16 years of age. That
would be a serious outlook for many honest and
respectable working-class people, who had a hard enough
struggle as things were at present. Further, he was
disposed to regard it as a shame that boys were to be
compelled to remain at part-time continuation classes
until they were 18 years of age, Personally, he thought
that the school leaving age should be allowed to remain
as it was—14 years of age—and that some readjustment
of the hours of the continuation classes should be macle
so as not to interfere with the ordinary and necessary
employment of boys in essential industries such as
mining.

Mr. R. W. Dron (Glasgow) said he would remind the
members that the institute existed for the advancement
of mining education. It was not a trade society, and it
seemed to him that the Coal Masters’ Association was
perfectly capable of looking after its own interests. The
points that had been touched upon by Mr. McLaren
ought not to be dealt with by the institute but by the
coal owners of the country. The Bill aimed at increasing
the educational standard and efficiency of the mining
official and manager, and its influence would ultimately
reflect itself on future mining operations. For that
reason he thought it would be unfortunate if the
institute were to identify itself with any movement for
the obstruction of the Bill.

Mr. John McLuckie (Larkball) characterised the
Bill as one of the most one-sided pieces of legislation

increased output is largely due to the use of silica
refractory material, which permits higher heats and
shorter coking time than are employed in Europe.
The modern American oven will carbonise commer-
cially more than 20 tons of coal per day, and,
contrary to the European idea that slower operation
is necessary to conserve the plant, this rate of
operation, with only current repairs, can be main-
tained for an indefinite time. The by-product oven
is not old enough in the United States to make it
possible to state from experience how long an oven
can be operated at maximum efficiency. There are
a number of plants in different parts of the country
which were built 16 or 18 years ago, which are more
efficient to-day than in the first year of operation,
and which show costs of operation which compete well
with those of the most modern plants.

The accompanying illustrations, figs. 1 and 2, show
the earliest and latest types of American ovens, and
illustrate sufficiently well the principal changes in
the design. The first ovens had a capacity for
carbonising 4-4 tons of coal per day, as compared
with the present capacity of over 20 tons.

The early ovens were economical in heat con-
sumption because the heat in the waste gases was
utilised efficiently in raising steam for the operation
of the plant. On account of the growing demand
for oven gas for metallurgical and other uses, the
change to the regenerative type of oven has been
general. While this type of oven is not so economical
of the total heat produced by the combustion of the
gas as is the combined oven and boiler plant, it makes
available for use half again as much of the surplus gas
as did the older type of oven. Modern ovens require
for carbonisation of the coal less than 40 per cent,
of the total heat in the gas produced.

Description of Oven.

Fig. 2 illustrates one of the principal types of the
modern oven, and a few words of description may
be appropriate here. The by-product oven is essen-
tially a closed chamber, heated from the outside, and
in the coking process the volatile matter of the coal
is distilled off with careful exclusion of air. This
point distinguishes it in principle from a beehive
oven, where the heat is generated by combustion
within the oven itself, with the resulting destruction
of everything except the coke. The oven shown

* From a paper read before the American Institute of
Mining Engineers.

flue system of the oven and meeting the gas to be
consumed.

It will be noted that this gas is supplied at several
points in the flue system, and that it flows steadily
through the supply pipes, its direction in the oven
being reversed by the reversal of the current of air,
so that no attention need be given to this point by
the operator. That is, when the currents are flowing
upward through the flue system, each gas stream is
bent upward and burns in the flue above the gas
pipe, which is opposite the partition wall. When
the flow is downward, the gas streams are bent down-
ward. By means of these several supplies of gas the
heat is supplemented as needed, and all the air
supplied is consumed by the last admission of gas.
The products of combustion pass out to the other
regenerator and thence to the reversing dampers and
chimney in the same manner as in an open-hearth
furnace.

In the earlier types of ovens, when luminous gas
was used, much of the heating was done by radiation,
but in modern practice, where the benzol is removed
from the gas, the combustion is not luminous, and
the heating is done mainly by conduction. To this
end, in the system described it has been found quite
advantageous to maintain a reasonably high velocity
of the hot gases in the flues, making use of the
principle which has been developed in some types of
hot-blast furnace stoves and other furnaces, where
a high velocity of the hot gases has been shown to
be most effective in the transfer of heat to the
adjacent surfaces because it sweeps away the sluggish
layers of gas lying against the surfaces, which, if not
removed, would form efficient non-conductors of the
heat which we desire to transmit.

The total amount of heat delivered to the com-
bustion flues is usually regulated by the pressure on
the supply of air and gas, and the distribution of
the heat among the various flues is controlled by a
simple regulation of the relative amount of gas to each
flue. Each flue may be conveniently inspected
through a peephole accessible from the working
platform outside, and it is found that the convenience
of this inspection and control is an important factor
in obtaining the best heating conditions.

Operation of By-Product Ovens.

The coal is charged into the oven from a hoppered
car running on the top of the oven structure, the
fuel usually being delivered through four charging