FRIDAY 14-th MAY 1982, ADULT EDUCATION CENTRE
DOMESTIC SMOKELESS FUEL
Mr. Keay started his Talk by saying that domestic smokeless fuels have been available for many years, but some of them have faults other than smoke, which are not readily visible, or noticable. In an endeavour to produce a near perfect smokeless fuel considerable research was carried out at the N.C.B., research laboratories, just outside Cheltenham under the auspices of the N.C.B. Chief Chemist, Dr. Bronowski.
Following this laboratory work a pilot plant was constructed at Birch Coppice colliery near Nuneaton for further investigation into the manufacture of this type of fuel. This was to be known as “HOMEFIRE” with a residual ash content of about 6% and harmful volatiles removed.
The results were sufficiently encouraging for a full scale plant to be constructed at Kerseley Colliery, Coventry. A firm of consulting engineers was engaged to design and supervise site work, installation and commissioning of the complete plant although detail design of some of the equipment was the responsiblity of the N.C.B. Contracts were arranged and let by the N.C.B., but administered by the consulting engineers. The final site covered some 38 acres and the initial budget price was £7,000,000.
A description was given of the various processes required for the blending and preparation of suitable coals from selected collieries. The processing included sizing, washing to remove ash forming slag, removal of volatiles by partial combustion. The waste heat from this process is used for steam raising for the steam turbo-generators providing about 6 megawatts; also for some process work. The final phase was passing the processed coal, now known as ‘char’, through the fluidisers where it was raised to a temperature of 320/350 degC in an inert atmosphere. The fluidisers are mounted on the roof of the press hall and the char is gravity fed to the presses. Three fluidisers are provided, one to each batch of twelve presses.
There are thirty six presses arranged in three banks across the press hall, each bank comprising twelve presses in two rows of six arranged back to back, each press with its own electric motor drive.
The press consists of a barrel with a hexagonal cross section with a ram travelling in this barrel driven by a crank. The crank end of the barrel is fed into a crocodile jaw and the outer end held closed by a hydraulic clamp which releases the pressure as each briquette is discharged from the barrel into the launder, a metal chest full of steam to prevent the briquettes now at high temperature and pressure from disintegrating and catching fire. From the launder the briquettes are discharged into a quench conveyor,which is a scraper conveyor submerged in a long tank of water for final cooling. The cooled briquettes are then carried by a belt conveyor system to distribution points for onward carriage by road or rail transport.
A brief description of the electrical system was given. The total load at the onset was estimated to be 12 megawatts; of this the Electricity Board would provide 6 megawatts and the balance by the Homefire turbo generating plant. The supply from the Electricity Board was obtained from a nearby Overhead 33kv overhead line through a ring main unit to a 33hv/llkv transformer to an llkv incoming switchboard, which also received the Homefire turbogenerator supply, synchronising was carried out at the generator site. From this board an 11 kv supply was afforded to the adjacent Kearsley colliery. The site llkv system was not a ring main but duplicate feeders to each transformer point feeding into a ring main unit to a local transformer.
The whole of the installation was monitored onto a mimic diagram located in the control room manned the whole time.
The President proposed a very sincere vote of thanks to Mr. Keay for a most interesting talk on an ever topical subject.