Phurnacite Plant, Abercwmboi
The Phurnacite Plant Project was kindly written by Mark Williams, Cwmbach.
The Phurnacite plant in Aberdare, Wales, is a smokeless fuel briquetting facility that covers 150 acres and has been in operation since 1942. Its Phurnacite product, a carbonized ovoid briquette, is used in closed appliances like AGA cookers, Ideal Boilers and Continental stoves. Mark Williams of Cwmbach provides a comprehensive overview of the site, including its layout, equipment and history.
The aims of this project are to show the production process at the Phurnacite plan. A great deal is written and spoken (not always good) about the plant by people with little or no knowledge about the place.
When reading this project please bear in mind that it was written some time ago, when the plant still stood and smokeless fuel was in production
The Phurnacite plant is situated at the lower end of Aberdare, between Aberaman and Abercwmboi. The site covers approximately one hundred and fifty acres, made up of layer blender and reclaiming, briquetting plants, numbers 1 and Z, ovens = 7 batteries – one of which is out of use i.e. number 3, ammonia plant, welfare block – canteen, baths, medical centre, general offices, laboratory, weighbridges, workshops, various sidings.
“Phurnacite” is the trade name for a carbonised ovoid briquette with a size of about 45 x 38 x 28mm. The product is smokeless, hard and virtually dust free and is competitive with Anthracite for use in closed appliances, such as AGA cookers, Ideal Boilers, Continental type stoves, etc.
The original plant for the manufacture of Phurnacite was started up in 1942 by Powell Duffryn Ltd. and has run continuously until that date.
I hope the map and supporting photographs, will enable one to have a clearer picture of the works.
n the mining of coal, small coal has always been a problem. Even in the days of hand cut, small coal was not paid for and men were sacked for loading too much small coal in their trams. Thousands of tons were tipped in south Wales as waste. Since the war, a lot of these have been cleared but there is still a difficulty in using up small coal, especially in south Wales with its Anthracite and low volatile steam coal is the obvious way to make large coal out of small coal is to combine the smaller pieces together. This is what briquetting does. The most common binder is pitch. Pitch is a residue left when coal tar is distilled. Many other materials have been used from time to time with varying success, but for various reasons, pitch is a binder generally used. The west Wales farmers used to mix Anthracite fines with clay and a little water, puddle into a ball and dried.
The resulting briquette known as Lucm was uses as fuel. Apart from being a messy fuel to make, it was also messy to burn, due to the powdery ash of burnt clay. Other binders used include:
- Crude Oil
- Sodium Silicate
- Sulphite Lye
The disadvantages of some of these binders are high cost and lack of water proofing qualities among other things. The advantages include smokeless ness because pitch when burnt gives off a large volume of heavy fumes. Briquettes have been made without binders but are generally used locally as a domestic fuel to minimise breakage due to handling.
The classic pitch bound block briquette made in south Wales consisted of blending coals. That is steam coal with bituminous, so that the block would tend to cake as it burned and minimised crumbling.
A typical briquette would contain
- Bituminous coal – 25%
- Steam coal – 45%
- Dry Steam coal – 22%
- Pitch – 8%
Such a briquette could be stored in all weathers and climates. Both Scott and Shackleton took crown briquettes to the Antarctic. The built their stables from them and as the horses where consumed as meat, the stables were consumed as fuel. Some of the blocks were returned to the works after thirty years in the frozen waste and were proved to be as good as when they were dispatched.
Although briquetting has been known as worked commercially for over 100 years, it was not until the beginning of this century that a roll press was used giving an ovoid or “boulet” generally about the size and shape of an egg. These where intended for the domestic market and disadvantages of giving off heavy smoke in the early stages of combustion. A lot of work went into the production of smokeless fuel. Trial with smokeless binders proved negative and carbonisation seems to be the answer.
The original Phurnacite had as its objective- Cynheydre anthracite reckoned to be the finest coal in the world. Phurnacite came pretty close to when suitable coals were available, but the very high standard of Ash content, caloriphic value and smokeless ness could never be equalled.
Between the wars compensation for injuries received underground would cease if the man could be found a job, even a light one with the company. This fact coupled with the problems already stated of small coal gave rise to a project by Powell Duffryn Limited to work out a way to kill two birds with one stone, using their small coal and saving compensation payments (getting men to work for the money). One scheme of mixing pulverising coal with oil proved successful for transatlantic liners but for some unknown reasons was dropped.
A plant for the manufacture of briquettes was set up near the washery middle Duffryn. Ovoids were produced there in the early 1920’s. In the late 1930’s Powell Duffryn together with Humphries in Glasgow, embarked on a project to make smokeless fuel using a re-taught process and to expand the works. Following a complaint from France about a shipment of dry steam coal, the engineer at the time went to investigate and came across a plant using the Disticoke ovens. On return, the re-taught method was dropped and a Disticoke battery was built. Tow presses were ordered from France and when the war broke out in September 1939, the two presses were at a northern French port, when France fell in 1940, the two presses remained crated throughout the war. During this time the plant was worked using the two old presses. The plant worked on a two shift – days and afternoons. The ovens were on a 24 hour cycle, this continued until after the war. The actual buildings were designed with a view to expansion and a third press was put into use in 1951.
The estimated life of a battery was 15 years, so number 3 battery was worn-out but the demand got so great it was decided to build more batteries and another briquetting plant. Number 2 plant with two presses and number 3 battery came into operation in 1957. Number 1 battery, which came into action in 1942 was taken out in November 1957. That was 15 Years 9 months, 9 months over its life expectancy. It was entirely re-built and reopened in September 1961. Number 6 battery was opened in 1966/67 and number 7 was opened in 1970. At the same time as a new 40ton press was installed, number 3 battery closed in 1974. The battery had been out of action since that date, various reasons have stopped it being re-built for example the planning permission hadn’t been granted.
Nationalisation of the plant was in 1947, when the coal industry was nationalised. The works were in the Number 4 area as a part of the local mining complex. Then in the early 1960’s the Coal Products Division was formed. Which took in patent fuels, coking plants and by-product works. In the 1970’s this was again reorganised and National Smokeless fuels N.S.F was formed to take over the manufactured fuels industry.
The plant has reached its peak of production an will probably be run down during the coming years. This is due to the fact that as the South Wales pits have been worked out and closed, suitable coals will not be available in sufficient quantity for economic working. The pollution problems will also contribute to the eventual close down.
Methods of production
The manufacture of Phurnacite starts at the tipping blending site. The raw coals, fines, duffs etc are tipped and spread out in layers. The proportion of different coals being worked out at the laboratory.
Coals arrived form all over South Wales including the colleries listed below:
- Lady Windsor
- Tower Collery
- Merthyr Vale
Lady Windsor colliery, supplied approximately 3000 tons a week to the Phurnacite Plant. The layered coal is set into 4 separate dumps or pads. The Reclaimer, which really is a big roller with buckets inside of which is a conveyor belt, picks up the coal and feeds it onto the belts which conveys it to the bunker houses of either Number 1 or Number 2 plants. Coal is fed into the bunker house into large storage bunkers, about 200 ton capacity each.
The old method of blending coal was putting different coals into different bunkers and feeding off any proportion which is required. The diagram below shows the old method.
From the bunkers the coal is fed by means of a turntable onto a scraper conveyor belt to a bucket elevator, from where it is fed into a vertical dryer. This being a large steel tubular structure with shelves, feeding to the centre and out, with a central shaft with arms, which push the coal off the shelves.
A large furnace directs heat of approximately 600 degrees centigrade up through the dryer. The coal falling through this looses its moisture and comes out with only about 2% to 3% moisture left. This is then fed by means of conveyors and elevators, into dry bunkers.
A belt, which has a measuring system, feeds the required amount of coal into a cage mill. At the same time, pitch now in liquid form is pumped in at the required percentage (8%) to be mixed with the coal. After the grinding in the mill it is fed into a steam heated vessel called a “Pug” where it is further mixed and fed into a Worm conveyor or Screw conveyor, the amount of flow controlled by the press operator into the press where the rollers give about one and a half tons per square inch and Ovoids are formed.
Particle size of the coal at the press is very important. Generally, the finer the mixture, the denser the briquette but finer particles present a greater surface area and thus require more pitch, the most expensive constituent of the briquette. Therefore, the blend and quality and cost have to be considered. The denser Ovoids are sometimes difficult to lights and do not burn so well.
The raw Ovoids are fed onto a belt and cooled somewhat before going onto the Trammel Screens, which remove the fines and broken pieces. These are then returned at the plant to be reused. From the Trammel Screens the Ovoids are taken to the oven tops and they are fed into storage bunkers, corresponding to the ovens and batteries underneath, That is, 8 ovens in each block – 5 blocks to one battery. There are 40 Bunkers of approximately 2 tonne on each battery.
The pictures above all illustrate various stages during the method of production.
Pyrolisys – Defined as the heating of a substance in the absence of air. When the substance being heated is coal the process is more commonly called a Carbonisation process.
The production of Phurnacite from raw Oviods is achieved on a rapid carbonisation process using Disticoke batteries. These batteries are constructed on a concrete raft on piles. Pile caps and raft are built to compensate for expansion.
The brickwork is of semi-silica, these are special bricks around the charge holes and squares and first-quality fire clay.
Each battery has 40 ovens built in groups of 8. The capacity of each oven is 2.3 tons of raw Ovoids, that’s 18.4 tons per block of 8. The sole of the oven is inclined at an angle of 43 degrees. The width of each oven is 200mm. The oven doors are 3 feet 8 inches in height.
To build – Bricking time took approximately 30 weeks, then preheating another 8 weeks. Steelwork was needed for the roof over the battery and to support bunkers.
The raw Ovoids are charged into ovens from the storage/shuttle bunkers. A simplified cross-section of an oven is shown below.
Each oven chamber when charged will contain 2 and a half tons of raw fuel. (Each Chamber is operated in groups of 8 known as a “block”. A block of ovens cannot be operated as individual units, they are designated to operate as an integrated unit.) Once a block has been charged/filled it contains 20 tons of raw fuel; and is left to carbonise for four hours. After this time the charged fuel will have reached a temperature of 900 degrees centigrade and net volatile content of the raw charge will have been reduced from 11% down to 2%.
Preheated air is the distributed to heating flues where it is mixed with gas and the resultant flue gas is subsequently passed back through the recuperator where it preheats the incoming air before it is sent into the atmosphere via a waste flue stack.
Gas flow during carbonisation
The gas evolved during the carbonisation process is extracted from the batteries using an Exhauster (gas pump). The diagram below illustrates the process undergone.
The layout of a gas exhauster or gas pump
Each oven chamber when charged will contain 2 and a half tons of raw fuel. (Each Chamber being operated in groups of 8 known as a “block”. A block of ovens cannot be operated as individual units, they are designated to operate as an integrated unit.) Once a block has been charged/filled it contains 20 tons of raw fuel; and is left to carbonise for four hours. After this time the charged fuel will have reached a temperature of 900 degrees centigrade and net volatile content of the raw charge will have been reduced from 11% down to 2%.
This process of gas purification is carried on in the “By Products Plant”. The By products plant performs the following functions:
A. Removes the various chemicals from the un-purified gas so that the resultant purified gases are of the correct quality for combustion.
B. Refines the extracted chemicals to usable form – this being achieved in other by-products, those being: Tar / Liquor separation plant; Ammonia concentration plant; Naphthalene removal/extraction plant.
Completing the carbonisation process
After carbonisation is complete the blocks are discharged. This is achived using a machine known as a “Quench Car”, which is essentially a large mobile water tank. When ready, the 8 ovens doors on a block are opened thus allowing 20 tones of Phurnacite at 900 degrees centigrade to discharge into the water, contained within the Quench car. This causes considerable evolution of steam.
When a block has been discharged, the oven doors are replaced and the block is recharged with raw fuel. The process starts once again.
The Phurnacite contained within the Quench Car once cooled, is discharged onto a ramp. From there the Phurnacite is transferred to a screening plant where undersize is removed from the Phurnacite. Resultant products from the Phurnacite are: Phurnacite Ovoids, Phurnacite Nuts and Phurnacite Breeze.
The Ovoids and nuts will then be sold to the domestic market. The breeze is mainly recycled. It is also sent to brickworks in the country, and sent abroad.
The Phurnacite plant outlet
The Phurnacite plant produces on average around 12 – 13,000 tones of Phurnacite a week, that is about 624,000 tones a year.
The information below illustrates what the production figures where in 1970.
Coal carbonised per year: 1,136,000 tonnes
Phurnacite produced per year: 832,000 tonnes
Phurnacite produced per week: 16,000 tonnes
Screened Nuts per year: 43,300 tonnes
Breeze produced per year: 142,000 tonnes
The Phurnacite is dispatched all over the country by rail and road. The map on the following page shows some of the distribution depots. The various depots around the country normally receive on average, nice 21-tonne wagons, but on occasions, they will order as many as twenty-one wagons all carrying 21 tonnes each.
Some parts of the country can only take a wagon of 16 tonnes, and these wagons are abused if a coal merchant only wants to order a small amount of Phurnacite. The Phurnacite that goes to the Isle of Mull, is first dispatched by rail to Glasgow and then goes by boat to the island.
Breeze is mainly recycled and mixed with coal at the blending site, but some of the breeze is sent around the country to various brickworks. One such place is Rudgewick Brickworks in West Sussex. Breeze is also sent to Cardiff docks by road, where it is shipped abroad and to Swansea docks by rail and then on to various parts of Northern Ireland by boat. The only product, which is actually sent to a by-product plant outside, is TAR. It is sent to National Coal Board central Tar refinery at Caerphilly for processing.
Pitch being a skin irritant, working conditions were very poor in the early days and as far back to 1911 regulations required that bathing facilities should be provided for patent fuel workers. Nowadays, with adequate bath facilities and a use of proper barrier creams coupled with far better operating conditions most of the hazards have gone from the fuel worker’s jobs.
In order to eliminate pitch dust from the atmosphere at the plant, the liquid pitch was introduced in the mid 1970s. This resulted in a very poor briquette. Various things were tried to remedy this. Good results were obtained by the addition of Sulphite lye to the mixture. However, this produced an obnoxious smell, which could not be eliminated, Molasses was tried in its place with almost similar results. Their factors combined with the public’s awareness of pure air resulted in demonstrations or protests from the local people. Pollution is always a problem in any plant; it was the major issue and threatened to close the plant.
In the late 1960s, the Balfour process was brought in, to try to control pollution. The process consisted of a large retort. Ovoids were fed into the top and carbonised. They were then let out through the bottom, through a gravity system. Once in operation, the volatile matter (Gas) could be used to heat up the retort for carbonising and inert gas (NITROGEN) was used to prevent combustion of the Ovoids. The proof could be called a continuous or flow process, besides low pollution, was that the unit could be shut down easily, without any damage, which would occur when a disticoke battery is shut, due to strikes, etc. However, a serious fault kept recurring with the solesand and the fantips. Although some of the finest retort and disolation engineers were called in, they failed to overcome the problem and the system discontinued, in the early 1970’s. This whole operation cost quite a great deal of money, but only shows the extent to which the national coal board is prepared to go to overcome the pollution problem of the phurnacite plant.
A system of burning off the fumes with the use of propane gas, although very expensive, is in operation. Another mixture tried in briquetting was the addition of sulphate ammonia to the raw coal at the blending site. Although this did improve the fuel slightly, the damage it caused to the machinery dryers etc, outweighed any benefit it had, it was later tried on an expensive system of being fed the coal, just before the pug. This still resulted in corrosion and was discontinued, when the pitch was changed from being fed directly into the pug, to being fed with the coal in the cage mill. Though agreeing, that the pollution caused by the plants is bad, it must also be considered, the contribution it makes to the national clean air. Without phurnacite production of roughly 75,000 tonnes per year, a greater amount of coal would have to be burned and although spread out, the pollution is bound to be greater. The weather conditions have a considerable effect on pollution. Research over a long period of time shows that pollution is greatest in bad weather, irrespective of production figures or plant times of charging. The workmen have been accused of not using the machinery properly but this is denied, as everyone at the plant is concerned because they realise that continual complaints can close the plant and everyone will be out of work.
Another problem facing the works is the shortage of coals suitable for the phurnacite process, which originally used Aberdare dry steam coal. The blending of bituminous and low volatile coal is difficult, when coals available but without suitable coals it becomes impossible it is reported from time to time, that trees in the Duffryn woods, close to the plant are being killed off, yet the new trees in the area which were planted, when the tip was removed some years ago are thriving. Most of the trees dying off are the result of underground fires. The pollution control cabin is manned at all times and everything possible, is done to satisfy the public. Machinery, being very old, is also a problem. It is hard to keep it in running order, due to machines being run for such long periods and the scarcity of replacement parts.
With all the problems associated with the phurnacite works, profitability, or rather the lack of it, being the main consideration if the plant were to close, the loss to the national coal board would be greater than keeping it open. This is due to the fact that large quantities of coal (somewhere in the region of 7.5 million tonnes) would have to be stocked. The coast of this would also lead to the closure of the few pits remaining in south Wales. With all the men from the plant, pits, transport etc, out of work, it would mean economic disaster for the whole of south Wales.
AberdareOnline would like to thank Mark Williams of Cwmbach for kindly donating this project for publication.