THE COLLIERY GUARDIAN

AND

JOURNAL OF THE COAL AND IRON TRADES.

Vol. CXVI.

FRIDAY, JULY 12, 1918.

No. 3002.

Coke = Oven By = Products in 1917.

REPORT UNDER THE

The Fifty-fourth Annual Report of the Chief In-
spector of Alkali, Etc., Works (Mr. W. S. Curphey),
states, with reference to sulphuric acid works, that much
attention was given by manufacturers to the relative
advantages of the different types of lead chamber
plants, and also to the comparative advantages of
chamber processes and catalytic processes as adapted
to the character of acid required, the uses to which it
is to be put, and the local circumstances of particular
works.

Sulphuric Acid Chambers.

In operating the chamber process, the question of
intensive working continued prominent, and examples
of the more recent designs of plant became more
numerous. In a few cases work continued on the old
lines of large chamber space with small absorbing and
denitrating columns. In the majority of cases chamber
plants were in operation—many more or less modified
in design — with smaller chamber space associated
necessarily with more powerful “nitre” recovery
appliances. In a growing minority, chambers were at
work of dimensions more like towers than like the
older form of rectangular chamber and either empty
with external water cooling or packed with material
to provide surfaces for contact between the circulating
gases and descending liquid.

The chamber space in use varied widely in different
works. The number of cubic feet of space provided per
pound of sulphur burned per 24 hours in works using
the old style of rectangular chambers reached a maxi-
mum of 25, whilst in works using later designs of
chamber plants—of which there is a great variety in
detail and arrangement—a minimum of between six
and seven was in operation.

In plants composed of chambers with dimensions
like towers, and provided with external water-cooling
(Mills-Packard system), the chamber space provided
was 3-6 to 4-5 cu. ft., whilst in plants composed of
columns provided with packing over which acid passed
(Opl system), the available space was about cu. ft.
after allowance is made for the space occupied by the
packing material. There were also instances where
a combination of rectangular chambers and column-
like chambers was in use with an intermediate chamber
space.

As the relative chamber space diminishes, the time
for passage of the reacting gases through the plant
decreases. In one works where the Opl and the
rectangular type of chamber plant were both in opera-
tion, it was computed by the management that in the
ordinary chamber set the time available for reaction
of the gases was 144 minutes, whilst in the column
chamber set all chemical inter-action had to be effected
in 12-3 minutes. It does not necessarily follow that
advantage lies with the smallest chamber space. Many
factors come into play, and a manufacturer in coming
to a decision requires to take into consideration a
variety of points, some of more general application,
some which may apply specially to his individual case.

As the time for chemical action becomes less, the
sensitiveness of the plant increases, so that with very
limited space per unit of sulphur burned, close and
skilled supervision is essential. This is by no means a
disadvantage. There is still in many cases, instead
of a proper appreciation of the collateral advantages
which are secured by efficient control, a feeling that
low expenditure on management is one step towards
reduced cost of production. That this is an erroneous
view has been repeatedly proved in instances coming
within the inspector’s own observation.

A more thorough and more complete system of
examination of the composition of the chamber gases
at different stages of the manufacturing processes was
introduced in a few works. In these cases the com-
position of the gases before entering and after passing
the Glover tower, and also before entering the Gay-
Lussac tower, was systematically examined and re-
corded, in addition to the usual practice of testing
the acidity of the gases discharged from the plant.
By such procedure the best conditions for most effi-
cient working of the Glover tower can be controlled,
any tendency to abnormal composition of the chamber
gases can be quickly recognised and rapidly corrected,
and the best conditions for effective nitre recovery in
the absorbing towers can be assured with benefit as
regards regularity and economy of working with
maximum production.

Catalytic Methods.

A new feature also was the introduction of catalytic
methods for supplying the necessary nitrogen com-
pounds for the chamber process, instead of using
nitrate of soda and sulphuric acid in the usual
“ potting ” method. This has the advantage of giving
a continuously uniform supply of oxides of nitrogen
and avoiding the loss of sulphuric acid contained in
the nitre cake, apart from special advantages at this
time of war.

In the early part of the year there was much pres-
sure on the available plant, which increased the diffi-
culty of effecting adequate repairs, but later the posi-

ALKALI WORKS ACT.

tion was distinctly easier, and at the end of the year
the condition of plants in general was superior to
that at the end of 1916. Damage by fire in two works
resulted in new plant on more modern lines being
erected. In regard to one of these, Dr. Bailey, in
one of his district reports, remarks: —

“The results of the fire were aggravated by the
presence of nitre in the fire zone; this fact induces
one to draw attention to the inadvisability of having
any considerable quantity of nitre stored in a position
where damage from fire is at all likely to occur; nitre
bogs, moreover, should be washed to prevent careless
storage of these articles, which in dry, unwashed con-
dition are easily ignited, and when once fired burn
with almost explosive violence. Very serious fires
have been known to be due to the accidental ignition
of carelessly discarded unwashed nitre bags.”

In other works extensive renewals of plant were
made, and several entirely new installations were com-
pleted in the course of the year, whilst others were
still under construction, so that now there appears
to be considerable capacity for the manufacture of this
essential chemical.

The new development of the interposition of an
iron contact tower between burners and Glover tower
did not proceed as rapidly as was anticipated, so
that there is not yet much experience of results
achieved to refer to. In the interim, however, the
modification is being adopted in a larger number of
works.

The continued demand for large quantities of
highest strength sulphuric acid led to a further in-
crease in plants for contact processes. As formerly,
three general types of plant were in use: (1) Oxide
of iron contact material for production of “ oleum,”
with residual gases used for production of chamber
acid either in ordinary chambers or in packed towers
used as substitutes; (2) oxide of iron contact material,
followed by platinum contact material to produce
“oleum” from the residual gases; and (3) platinum
contact material for “ oleum ” production. There
was also in continued satisfactory operation a modifi-
cation of (1) in which no oleum was manufactured,
but in which, by admixture of acid from the contact
section with acid from the chamber section, sulphuric
acid of a strength intermediate between “oleum”
and “Glover” acid was made. Plants of the first
type still gave some trouble in adapting the cold, dry,
dilute gases coming from the contact section of the
plant to the conditions required for the chamber re-
actions, and, of course, the output of oleum was much
less than with the second and third types. Plants
of the third type gave the most satisfactory results
as regards output of oleum and acidity of residual
gases from the manufacture discharged into the
atmosphere.

Sulphate of Ammonia.

The number of registered works producing sulphate
and muriate of ammonia, and gas liquor, again
increased ; 742 processes were under inspection, being z
20 more than in 1916. The change from manufacture
of sulphate of ammonia to production of concentrated
liquor, noted in previous reports, continued to make
further progress. Several works ceased entirely the
manufacture of sulphate, and in many others this
process was greatly curtailed to permit of increased
output of the alternative product. The increase of
above 20 was the net result of an increase of 27 works
registered as gas liquor works, and a decrease of 7
registered as sulphate of ammonia works.

The following table shows the quantity of ammonia
recovered in the United Kingdom as a by-product
expressed in terms of sulphate: —

1917.	1916.	1915.

Gas works................ 188,478	172,269 173,675

Iron works ...	...	13,621	15,154 15,142

Shale works............. 60,560	5.7,988 58,826

Coke oven works ...	... 166,354 159,506 145,406

Producer gas and carbon-
ising works (bone and
coal) .................... 29,604	28,786	33,218

Total ........ 458,617 433,703 426,267

The ammonia products manufactured from gas
liquor were distinctly greater than in 1916. Numerous
influences were in operation to bring about an oppo-
site result. The inferior quality of coal used in many
gas works, the increased use of water gas to help up
production of gas, the larger production of gas per
ton of coal carbonised, the use of steam in vertical
retorts, the gas liquor run to waste in many works
owing to lack of the acid necessary to make sulphate,
and the extended production of concentrated liquor
with a too frequent higher working loss by this pro-
cess, all tended to decrease output, whilst the only
favourable influence, more than sufficiently powerful
to counteract these adverse factors, was the active
demand for gas, which in many works called for the
use of every unit of producing plant during the season
of maximum consumption.

In several works dissatisfaction was expressed with
the quality of salt obtained when using arsenical acid,
but this is a difficulty which has been overcome for
many years past in most works using such acid.

“ Direct Process ” of Sulphate Making in Gas Works.

The conclusion of the work in 1916 still found one
faced with the fact that the yield of sulphate in the
direct process remained low, when judged by relative
standards, even at works where every effort was made
to reduce working losses at the purifiers, storage tanks
and ammonia still to a minimum. One was led to ask,
therefore, Are we justified in expecting a recovery
figure of 28 to 30 lb. of s/a per ton of coal carbonised
in the absence of reliable data respecting the actual
production of ammonia at the retorts? Preliminary
test certainly indicated that such a recovery figure
is by no means a standard universally applicable.
Attention in 1917, therefore, was mainly directed to
the systematic collection of data relating to the yield
of ammonia from the retorts under varying seasonal
conditions. Incidentally, this involved the determina-
tion of retort bench temperatures by Fery optical
pyrometer, and a still closer control of working losses.

The attention of the management of all the works
where the direct process is in operation has frequently
been directed to the importance of keeping a close
watch on the effluent spent liquor from the still,
where serious losses are apt to occur if working con-
ditions with respect to liquor feed, liming and steam
are not strictly regulated. Experiment shows that
the ammonia still in the direct process is by no means
the secondary source of supply that was once imagined.
Attention was early directed to the probability of
effecting a saving of steam at the still by utilising
the Liebig condenser as preheater where the still
is of the continuous type. A preheater of this design
was independently adopted at one works, and has been
in use for the past six months with excellent results ;
its adoption at other works is under consideration.
Further experience of the working of the “ neutralis-
ing box ” fully justifies expectations, and at another
works, where a similar box has recently been in-
stalled, equally satisfactory results have been obtained.
Control of purifier temperatures by means of ther-
mometers inserted into the oxide on the various grids
is still practised at one works, and the advantage
of maintaining the temperature of the oxide by steam
pipes suitably placed within the purifiers has been
fully demonstrated. It is important, however, in this
connection to note that steam pipes are subject to
rapid corrosion if exposed to the action of spent oxide
or of condensed liquor, and if steam pipes are placed
within the purifier care should be taken in the selec-
tion of material, arid the pipes should further be
protected from contact with oxide and from liquor
draining from above.

Ammonia in Oxide Purification.

Further experience on the part played by ammonia
in oxide purification confirms the conclusion that a
regulated supply of ammonia is essential to efficient
purifier working in the “ direct process,” especially
during the colder months, when the boxes are working
at full load; and one is disposed to attribute much
of the irregularity of working during the colder
weather to the free absorption of ammonia by the
relatively wet oxide and its conversion into fixed salts
—thiocyanate (sulphocyanide) and sulphate. When
oxide fouls during such periods of disorganisation, it
is usually found to possess an acid reaction and to
contain marked traces of soluble ferrous salts, and the
free use of the ammonia by-pass has often enabled
a foul box to clear itself if a-suitable temperature
be maintained. It was suggested in the Report for
1916 that a better control of ammonia to the boxes
might be effected if it were possible to admit a supply
of the gas separately to each of the various layers in
amount controlled by simple qualitative test. Separate
admission of ammonia is a refinement of working
hardly possible in ordinary practice, but undoubtedly
qualitative test applied to the gases leaving the first
and second boxes is a desideratum; such test has
been in regular use at two works, and has afforded
valuable guidance to the management on several criti-
cal occasions. The gas is sampled by means of
thermometer tubes, and is allowed to impinge on a
strip of moistened litmus paper held close to the cock.
Experience shows that with the purifiers working
normally the gas leaving the first box imparts a
decided blue colour to the paper on a 20-30 secs, ex-
posure ; that leaving the second box a faint trace only
or none.

Bubbler Losses.

During the year attention was directed to a source
of loss at the bubbler, which, though small in abso-
lute amount, is by no means negligible considered in
relation to weight of coal carbonised, and in a
process where multiplied small losses may be serious
in their cumulative effect. The loss referred to is due
to the periodic removal of tarry scum from the surface
of liquor in the bubbler effluent tank. Such scum
is predominantly arsenical in works where arsenical
acid is fed into the bubbler; in other works it is pre-
dominantly tarry. In some works it is the practice
to return this acid product to the tar and liquor well;
in others it is thrown away. Neither practice is to