THE COLLIERY GUARDIAN

AND

JOURNAL OF THE COAL AND IRON TRADES.
______________________________________

Vol. CVIII.

______________________________________________________________________________________

The By=Product Coking Industry and its Relation to the
Manufacture of Iron and Steel.*

By G. STANLEY COOPER, B.Sc. (Lond.).

The standard of efficiency which has been reached in
connection with iron and steel works at the present time
is a result of the more economical application of exist-
ing resources rather than of anything entirely new.
Perhaps the most striking development has been in con-
nection with the fuel side of the industry, and it is to
this question that the present paper is devoted. The
author proposes to confine himself to the development
which involves the production and use of coke oven gas
for metallurgical purposes.- At the present time com-
paratively few waste heat ovens are built. The regener-
ative oven has the advantage that the surplus energy
contained in the coal is produced in the form of a com-
bustible gas, which can be used anywhere and at any
time without appreciable deterioration. It can be used
for a variety of purposes, such as town lighting, steam
raising, development of power by means of gas engines,
and also a fuel for open hearth furnaces. Until com-
paratively recent times very little attention was paid to
the surplus coke oven gas, and although it was gener-
ally assumed that 50 per cent, of the total quantity of
gas evolved from the coal was available over and above
that required for heating the ovens, yet very little of
this 50 per cent, was actually used. When it came to
be realised that coke oven gas could be used as a fuel
for open hearth and other furnaces, more attention was
paid to the question of gas production in by-product
coke ovens, and consequently better efficiency was
obtained from the ovens, at any rate so far as gas yield
was concerned. In some cases the whole of the surplus
coke oven gas was diverted for use in the iron works,
and efforts were made to increase the amount of avail-
able gas.

In this connection the regenerative type of oven was
developed, and many improvements brought about. At
the Allerdale Coal Company’s Colliery a battery -of 50
Koppers’ regenerative ovens was set to work in 1911,
and the following figures, kindly supplied by Mr. F. D.
Harper, the manager of the plant, serve to show what
results may be expected using this type of oven. The
coal used is compressed before carbonisation, and
usually contains about 10 to 12 per cent, of added
moisture ‘—Coal carbonised per oven per annum (wet),
2,574 tons; coke produced, 1,704 tons; coke yield on dry
coal, 73-25 per cent.; gas yield per ton of coal,
10,600 cu. ft.; surplus gas per ton of coal, 6,996 cu. ft.;
weight of wet.coal (10 per cent. H20) per oven charge,
9-5 tons; time of carbonisation per charge, 29 hours.

After
extraction of
benzol.

2'4
2'8
0'2
4'8
..	31'5

..	55'2

3'1

.. 560 B.Th.U.

.. 511 B.Th.U.

increase the

Gas analysis.

C02...............................
CnHm..............................
o2 ................................
co_____:...............................

ch4 .................................

h2 ................................

n2 ................................
Calorific value (before extraction) .

Ditto (after extraction) ......

The natural consequence of the efforts to
surplus gas yield was the provision of other means for
supplying the heat necessary to carbonise the coal in the
coke ovens, and thereby to allow the whole of the gas
produced from the coal to be available for extraneous
purposes. An exactly similar position, but one looked
at from another point of view, had arisen in connection
with the gas industry. It has been realised that
chamber carbonisation had many advantages to offer
as a means of gas production for town purposes. In
such case, as the gas is the principal object, coke being
only a secondary consideration, it was important to have
the maximum possible quantity of available gas per ton

* From a paper submitted for discussion at the autumn
meeting of the Iron and Steel Institute, now abandoned.

FRIDAY, SEPTEMBER 25, 1914.

of coal. With this in view, chamber carbonisation was
adopted, and in order that the whole of the gas produced
might be available for towh consumption, producer gas
was resorted to for heating the chambers. As producer
gas has a calorific value of only about one-fourth to
one-fifth of that of coal gas, various re-arrangements
were necessary in order to allow of the production of a
sufficiently high temperature, and eventually it was
found that by preheating the producer gas, and supply-
ing it with preheated air in the usual way, suitable
temperatures could be obtained with economical con-
sumption of the producer gas. Working on these lines,
a battery of 18 ovens was erected at the city gas works
of Vienna. The ovens were heated by means of pro-
ducer gas generated in Kerpely producers. This experi-
mental plant was a complete success from the first, and
numerous other installations have since been erected,
working exactly on this principle.

The main points of difference between the several
systems of coke ovens now in use may be summarised
as follows :—(1) The arrangement of the heating flues;
(2) the facilities for inspecting all the working parts of
the ovens; (3) the method of regulating and controlling
the heating of the ovens; (4) the preheating of the air
required for combustion. The essential features of a
good coke oven may be generally stated thus. The
heating of the ovens must be easy to regulate and con-
trol. The temperature should be the same throughout
the whole length of the oven wall, in order to produce
a homogeneous coke. All working parts of the oven
should be easily accessible for inspection and regula-
tion, and without discomfort to the workmen. The
amount of gas required for the heating of the ovens
should be reduced to the minimum, and the largest
possible amount of surplus energy should be produced
without decreasing the output of by-products. The
ovens should be simple in design, and great care should
be bestowed upon the foundations. It is particularly
necessary to study the nature of the foundations, and to
take precautions against the possible effects of the heat
of the oven structure on the subsoil.

The Koppers’ regenerative coke oven is then
described. This, it may be recalled, is of the vertical
flued type, and possesses many special features, more
particularly as regards the arrangements of the heat-
ing flues and regenerators, and the facilities for inspec-
tion. The distinguishing feature of the oven lies in the
employment of separate regenerative chambers for each
oven, so that every oven is entirely independent of its
neighbour. This construction permits of the air for
combustion and the chimney draught being separately
regulated. Two of the principal features of this type of
oven are the sliding bricks, and the openings in the top
of the ovens which give access to them. The openings
serve not only to provide means for regulating the
dampers, but more particularly to give access to the
gas nozzles.

The author deals next with the Koppers’ regenerative
gas oven. In gas works the principal object is the pro-
duction of the greatest possible amount of illuminating
gas, and the coke obtained is regarded more or less as a
by-product. By making slight alterations in design and
practice the regenerator coke oven has been adapted for
use as a gas oven, and as such is capable of producing
a high yield of illuminating gas of good and even
quality. At the same time the coke obtained does not
deteriorate in quality, and is far superior to ordinary
retort coke. The important point is to secure that the
whole of the gas evolved from the charge should be
available for illuminating purposes, arid hence some
other means has to be found for heating the ovens. This
can best be done by installing a central producer gas

No. 2804.

plant quite apart from the chamber ovens. The pro-
ducer gas is preheated before combustion, just as the air
is preheated in the case of the regenerator coke oven,
and the design of the oven is altered to accommodate
these new features. In the main, however, especially
as regards the arrangement of the heating flues, it
remains unaltered.

It was found necessary to ensure the thorough
cleansing of the producer gas from dust and tar before
it was allowed to enter the heating flues, otherwise the
tar is deposited in the valves, which eventually become
clogged up, whilst the dust is carried forward into the
heating flues, and damage is caused there by fusion of
the dust and slagging of the flue bricks. The gas is
first cooled in order to remove tar, and is then thoroughly
washed with water by means of centrifugal sprays, and
the whole of the dust being thereby removed.

The Koppers’ Combination Oven Operated on Blast-
furnace Gas.

From the two foregoing types of ovens what is known
as the Koppers’ combination oven was developed. As
its name implies, this is an oven which can act either
as an ordinary regenerative coke oven, or as a regenera-
tive gas oven. In the former case it is heated by means
of a portion of the gas evolved from the coal carbonised,
whilst in the latter case it is heated by some other gas,
such as producer or blastfurnace gas. The arrangement
of the oven is such that it can be operated at will either
as a coke oven or as a gas oven. Blastfurnace gas
resembles almost exactly producer gas as far as its pro-
duction and calorific value are concerned, and therefore
what had been done with producer gas it was naturally
expected could also be done with blastfurnace gas. This
idea of employing blastfurnace gas, as far as the writer
is aware, was first mooted at the annual meeting of the
Iron and Steel Institute, held in London in May 1899,
in a paper read by Mr. Enrique Disdier (Bilbao), on
“The Use of Blastfurnace and Coke Oven Gases.’’ This
paper contains the following paragraph:—“ Thiril
method : There is another new course open for consider-
ation. In this, the coke ovens are heated by the blast-
furnace gases, and the oven gases are used for driving
gas engines.”

At a later date Mr. Adolph Wirtz, of the Friedrich
Wilhelmshutte, Millheim-Ruhr, Germany, suggested’the
employment of blastfurnace gas for heating coke ovens
at his works. Th* suggestion was carried into effect,
with important resulting economies, for the Friedrich
Wilhelmshutte no longer depended only on the surplus
gas produced in their ordinary type of regenerator coke
ovens, but by the employment of blastfurnace gas for
heating purposes they were able to command a much
larger surplus, and at the same time, in the event of
there being any shortage of blastfurnace gas, due to the
stoppage of the furnaces, the ovens were not rendered
idle, but could immediately be transformed into ordi-
nary regenerative coke ovens, the only difference being
that the quantity of surplus coke oven gas was reduced
by about 50 per cent. As each oven is an entirely
independent unit, the amount of coke oven gas avail-
able could be regulated between very wide limits, either
according to the demand for coke oven gas in the iron
works or the amount of blastfurnace gas available from
the furnaces. The system also possesses a still further
advantage. By the utilisation of the blastfurnace gas,
the time of carbonisation was actually reduced, thereby
allowing of an increased output from the ovens. The
plant of the Friedrich Wilhelmshutte consists of 80
Koppers’ combination ovens arranged in a single battery.
For the purpose of comparison drawings are produced
showing cross sections through (A) the Koppers’ regen-
erative coke oven, (B) the Koppers’ gas oven, (C) the
Koppers’ combination oven (fig. 1).

Coke Oven “ A.”—In this type of oven a portion of
the gas evolved from the coal is used for heating the
ovens, about 40 to 50 per cent, of the total quantity
evolved being required. After passing through the by-
product plant, the required portion of the gas is returned