Acid Plants at M/S Factory Dalbeattie :
This largely-forgotten part of the Factory has only been restored to knowledge by the actions of Mr. Gordon Nicholson,
now a resident of Dalbeattie and the manager of the Unit 1 Acid Plant and its Waste Acid Recovery Plant. Mr. Nicholson
retained copies of working plans of the Plant and the instruction documents he prepared for the staff, so that one could
almost rebuild and operate the Plant. In addition, he recorded the operation of the Nitroglycerine production process, an
act for which various historians are grateful.
Concentrated acids were delivered by rail from the main works of M/S Factory Dumfries at DRungans, Cargenbridge, to the
Acid Plants located on the north-eastern part of the Platform Group of buildings beside the two Goods Yards. Each Acid Plant
consisted of storage tanks for nitric and sulphuric acids, processing tanks and absorbtion towers used in reprocessing, and
a producer-gas plant used to heat acid recovery stills. Acids from each Plant were piped up to 400 metres to the Nitration
Hills in each Unit and reacted with glycerine to produce Nitroglycerine. Refuse acid from the process was then returned to
the Acid Plant, the nitric acid separated and recycled and the waste sulphuric acid concentrated before return to Drungans
for further re-processing.
Uniquely, the details Mr. Nicholson retained allowed the writer to name and estimate the total staff on duty at any one
time. In an era when there was little industrial electronics and no industrial computers, control depended on the alertness
and training of the operators. When time permits, the writer will transcribe the documents as Appendices to a book.
Archaeological Evidence for the Acid Plants :
Although rather scant, there is sufficient to prove that the Acid Plant for Unit 1 was indeed located where it had been
reported to be. Pictures were taken of the support plinth for the eight Fume Absorbtion Towers that were used to concentrate
recovered Nitric and Sulphuric Acids. Beside it were the remains of large chemical stoneware rings, all unfortunately
smashed, and the star-section and concentric ring section Raschig bricks that formed absorbtion surfaces within them. To the north
east of this structure were a series of parallel walls and crosswalls that turned out to be the supports of the Refuse Acid
and Mixed Acid storage tanks. To the west of the towers plinth is the smaller plinth that supported the Denitrification
towers, where steam stripped Nitric Oxides from the Refuse Acid, producing a Dilute Oil of Vitriol (weak sulphuric acid).
Regrettably, the unusual industrial Producer Gas and Vitriol Concentration plants to the west of the smaller plinth were
completely destroyed, although the base of a burn-out chimney was also photographed.
The Unit 2 Acid Plant had been thought to be completely destroyed, but there are indications that an ancient gantry that
now supports a corrugated sheet wall was part of the Acid Plant. From its length and position, it would appear to be part
of the railside loading and unloading system. All else appears to have been completely destroyed during clearance of the
site for the lorry parking and loading areas of the Stelrad radiator factory.
Although the prevailing southwest and northwest winds would have tended to disperse the fumes from the Acid Plants, there
were circumstances when this did not occur. A temperature inversion - with misty, warm air held near the ground, little wind
and no dispersion - resulted in fumes affecting the staff in or near the Canteen. Mrs. Ena Bolton, formerly in Blending and
Packing and a Canteen worker in Unit 2, recalled this problem and confirmed the weather conditions in which it occurred.
Acid Plant Operation :
A full description and transripts of Mr. Nicholson's papers will be added once time permits. A summary of the Acid Plant
processes follows :-
- Mixed Acids (concentrated Nitric cid and concentrated Sulphuric acid) from Drungans works at Dumfries received at Goods
siding in railway tankers and unloaded into storage tanks. A smaller quantity of fuming Sulphuric acid (Oleum) was received
and unloaded to a storage tank for use in the Nitric acid recovery process.
- Acids mixed with reprocessed Nitric acid and sent to Nitration Hill.
- Refuse Acid received from Hill and stored in tanks until reprocessed.
- Mixed Refuse Acid denitrated by being sprayed down through hot steam in denitrification towers and the nitric acid
fumes escaping from the top was piped into absorbtion towers, achieving a progressively higher concentration of acid. This
recovered Nitric acid was then sent for remixing.
- In remixing, the Nitric acid was mixed with fuming sulphuric acid (Oleum), so the result was equivalent tothe mix of
concentrated Nitric cid and concentrated Sulphuric acid delivered from Drungans.
- Denitrified weak and impure sulphuric acid (Dilute Oil of Vitriol, D.O.V.) (including impurities such as glycerine) was further
treated in the Pauling Pots, heated by Producer Gas, designed to evaporate the excess water and to oxidise impurities such
as glycerine. The product was Concentrated Oil of Vitriol (C.O.V.), a fairly pure Sulphuric acid that nevertheless required
further treatment at Drungans.
- Water vapour, carbon monoxide and some sulphuric acid was driven off in the process, cleaned in a water spray
condenser and discharged from a high fume stack. This was fairly effective but could cause local air pollution in
some atmospheric conditions.
Sections and processes of the Unit 1 Acid Plant :
This summarises the details on Gordon Nicholson's plans and his description of plant processes. The Plant is at the
northeast end of the Platform Group, so the structures and processes will be given in order from southwest to northeast. :-
- Producer Gas Unit :
Consisted of a brick-walled coal store beside the platform, with a chute down to the basement of the Producer Gas furnace.
This consisted of a circular grate above an ash pit, with a mixture of compressed air and steam passed up through it. The
resulting gases were a mixture of carbon monoxide, hydrogen and nitrogen, with tar and dust as impurities. Once going, the
gases were fed into a main that led to four burners to heat the Sulphuric Acid Concentration pots.
Nothing remains of this part of the works except what may be the square base around the site of the burn-out chimney, used to
periodically remove soot and ash from the Producer Gas main.
- Sulphuric Acid Concentration Unit :
In a building next to the Producer Gas Unit. Consisted of two pots with reflux (dephlegmating) columns on top, one pot being
heated by two producer gas burners at any one time. D.O.V. acids in the pot were heated to a point at which any remaining
impurities (glycerine, traces of nitroglycerine, oils, dirt) were oxidised and destroyed. D.O.V. acid was sprayed into the
top of the column, and as it passed down the column it was enriched with sulphuric acid vapours rising from the heated pot,
part of the contents of which (now Concentrated Oil of Vitriol, C.O.V.) overflowed into a cooler, then into settling and
storage tanks within the Sulphuric Acid Concentration Unit building. The tanks of C.O.V. were periodically emptied into
rail tankers after they had been emptied of Mixed Acid, and taken to Drungans. Vapours from the top of the column entered
a water-spray condenser and were drained off.
Nothing remains of this part of the works.
- Denitration Unit :
This was in a taller building next to the Sulphuric Acid Concentration Unit but not linked to it in the process. Two tall
De-Nitrating Columns, one operating at any one time, contained lumps of white quartz. Refuse Acid from the Nitration Hills
was heated to 75 degrees Centigrade and injected at the top of the tower, meeting and being stripped of nitric oxides by
steam rising from the base of the tower. Hot Dilute Oil of Vitriol (D.O.V.) acid accumulated in the base of the tower, where
it preheated the pipes of the Refuse Acid. The D.O.V. was further cooled before storage in tanks in an adjacent building
beside and north of the Denitration Unit. D.O.V. (sometimes referred to on the plans as Waste Sulphuric Acid, W.S/A) was
then pumped to header tanks for the Sulphuric Acid Concentration Unit.
The concrete plinth of the De-Nitrating Columns still survives and some fragments of the stoneware associated with it.
- Fume Absorbtion Towers :
The eight absorbtion towers used a mix of air and steam to convert nitric and nitrous oxides into a weak acid that was
strengthened into a fairly strong Nitric Acid (N/A). Water entering the eighth tower from its top absorbed the last fumes
to produce weak acids, which were strengthened by absorbing the stronger fumes in tower seven, and so on through the other
towers until tower one, after which the acid was passed into a pot where the fumes coming out of the Denitration unit were
partially absorbed ('Bleached') to over 90% concentrated Nitric Acid. From there, the acid went to a small storage tank
before re-mixing. The vapours that left the eighth column were essentially nothing but water and air and were vented.
The Fume Absorbtion Tower plinth is the highest element still standing of the whole Acid Plant. Fragments of the towers'
lining rings and the star-shaped and concentric tiles that filled them, lie tumbled between the plinth and the bases for
the Storage Tanks.
- Storage Tanks :
These tanks were in various sizes and had various functions. The smallest ones were rectangular tanks nearest to the
plinth's northern end, containing Oleum (fuming Sulphuric Acid) that was mixed with the Nitric Acid to form a Nitric and
Sulphuric Mixed Acid (Fortified Acid, F/A) that was re-used in the Nitration Hills. The mixing tanks produced a lot of
heat, so the acid had to be cooled by a radiator in a large watertank beside them. To the south and east of these were two
large cylindrical 55-ton tanks that held the waste acid (Refuse Acid) from the Nitration Hills. Finally, the three largest
tanks - capacity of 85 tons each - were on the northeast side and held the Mixed Acids from Drungans for the Nitration Hills,
and the Fortified acid from the mixing tanks.
The writer was surprised to discover amongst undergrowth ands small trees the identifiable remains of the supports for the
following, going from the east (by the Absorbtion Towers plinth) :-
- Synthetic Refuse Acid Tank : Chimney-like brick plinth.
- Fortified Acid and Oleum Tanks : Just northwest of the Synthetic Refuse Acid Tank support there may be parts of the base
that supported this, but dumped rubble confuses the evidence.
- Refuse Acid Tanks : Bases of the two tanks and the brick retaining bund.
- Mixed Acids Tanks : The bases of the three tanks and the brick bund wall that retained any leaks, still in good condition.
The Acid Plant's remains are so slight and overgrown that at first inspection they were thought to be part of a coal
depot. Only Gordon Nicholson's plans made it possible to rescue the layout. His documents were intended for staff who at
the very least could walk round it and inspect every part, so it was not easy to resolve the significance of the Acid Plant
archaeology. All the same, the surviving remains deserve at the least to be cleared of growth and preserved as a record
of this aspect of the works.
Staffing Levels at Unit 1 Acid Plant :The instruction and shift change documents prepared by Gordon Nicholson provide sufficient information to reconstruct the
titles and numbers of staff on duty during a shift. :-
- Acid Plant Manager : Mr. Gordon R. Nicholson. Possibly only on shift during day-work (daylight) hours.
From the documents, he was in overall responsibility of Unit 1 Acid Plant but some of his documents also apply directly to
duties of Unit 2 Acid Plant staff.
- Foreman : In charge of Unit 1 Acid Plant when on duty during day-work hours.
- Chargeman (Processman) : In charge of Refuse Acid denitration, Oleum transfer and mixing and transfer
of completed Fortified Acid (recovered Nitric and diluted Oleum mixture) to main Mixed Acid tanks. In the absence of the
foreman during day-work hours, he was also available to help the Assistant Processman at the Concentration Plant and
made periodic inspections of the other parets of the Acid Plant.
- Assistant Processman : In charge of Producer Gas Plant, producing fuel gas for the Pauling Pot
vitriol (sulphuric acid) Concentration Plant. In the absence of the foreman during day-work hours he also ran the Pauling
Pots and took the concentration samples for the hourly log.
- Acid Labourer : Mainly under supervision, but sometimes in charge of Denitration, including the final
stages of acid mixing and pumping the Fortified Acid mix into the main Mixed Acid tanks.
- Producerman : In charge of stoking with coal and routine operation of the producer gas plant, that
provided fuel gas for the Pauling Pot vitriol concentrators. His skills were similar to those of a well-trained steam
locomotive fireman. It is not clear from the documents if this was a separate job to that of the Assistant Processman, but
it is probable that it was.
- There are references to a Shift Superintendent (possibly a central administrative officer) being involved in the Foreman's
absences after 3 p.m. on Saturdays. This indicates that the Foreman and Manager may have been working staggered shifts, with
the Manager available most weekdays.
During day-work hours, the shift appears to have been Manager, Foreman, Chargeman, Assistant Processman, Producerman and
Acid Labourer. At night, the shift may have been the same except that the Manager was absent and the Foreman may have been
absent. It is suspected that the Manager and Foreman lived or were billeted locally, to be available in case of crises.
Geroge Nicholson had procedures for various crises, from air attacks to loss of one or more factory services or damage to
equipment, so he took his duties very seriously.
The Acid Plant remains the most thoroughly-documented section of the M/S Factory Dalbeattie, even though its remains are
neither extensive nor as impressive as other parts of the works. It is a significant contribution to the history of a
process now out of use, but which was essential to the successful manufacture of Nitroglycerine for cordite at Dalbeattie.