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Jessup-Bould Limited |
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Coke Oven By-Product Plants |
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Various Coke Oven Byproducts Plants
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1985 to 1999 |
Process engineering and commissioning of a range of byproduct plants and their unit operations. |
Summary of Process
Foul coke oven gas resulting from the carbonisation of coal
is cooled and cleaned in the byproducts plant to enable its use as a fuel gas.
Coke works around the world use many different
configurations and types of unit operations to clean the coke oven gas and
recover certain saleable byproducts. A typical plant will however follow the
process route described:
Coke oven gas leaving the ovens is sprayed with
"flushing liquor" to quench it from around 800 oC to 85 oC
and to flush the resulting condensed tar to the "downcomer". Here the
tar and liquor are separated from the gas and are themselves separated by
decantation. The liquor is then re-used, with excess liquor, due to
condensation of water vapour from the gas, being processed in an "ammonia
still".
Gas from the downcomer is further cooled to about 25 oC
in a "primary gas cooler", which may be either an indirect or direct
cooler. Here more tar is removed.
From the primary cooler the gas passes through an
"exhauster", which provides the motive force through the plant.
More tar is removed by the centrifugal action of the
exhauster, however a "tar fog" is still present in the gas. This is
removed by passing the gas through "electrostatic tar precipitators".
Some heat is gained in the exhauster and often a
"secondary gas cooler" is used to cool the gas to prevent naphthalene
being condensed out as a solid in the downstream "ammonia washing"
process.
The ammonia washers remove corrosive ammonia by scrubbing
the gas with a weak ammonia liquor. The ammonia is readily absorbed by this
aqueous solution. Ammonia is removed from the now "strong ammonia
liquor" by stripping with steam in an "ammonia still". After the
condensing out the steam from the still overheads, which are usually returned
as reflux to the still, the ammonia gas is disposed of by incineration,
catalytic destruction or sold as concentrated ammonia liquor.
Coke oven gas from the ammonia washers is then scrubbed with
oil to remove saleable aromatic components in the gas stream such as benzene,
toluene and xylene. The scrubbing is carried out in the "benzol
washers". Naphthalene is also removed by a similar process in a
"naphthalene washer" as this prevents deposition in the gas system.
The benzol and naphthalene are recovered by stripping with
steam in the benzol and naphthalene stills.
A proportion of the cleaned gas, around 40% is used to
"underfire" the coke ovens. The rest is usually used as a fuel gas
either on the associated steel works, or in a power generation plant.
Specific
Responsibilities
- Process Design.
- Lead Process Engineer.
- Commissioning Engineer
Achievements
- Process engineering responsibility secondments in
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Present Day Project Value Various, up to £
50,000,000 Unit Operations Coke oven gas cooling
(direct & indirect). Ammonia liquor pumping. Tar decantation &
pumping. Electrostatic tar
precipitation. Gas scrubbing (removal of
Ammonia, Benzol, Naphthalene). Stripping (of Ammonia,
Benzol, Naphthalene). Incineration &
catalytic destruction of Ammonia. Ammonium sulphate
production. Heat exchange &
condensation. Materials of Construction Carbon & stainless
steels. Duplex steels. Titanium. Hastelloy. Graphite. Documents Produced PFDs & mass balances. P&IDs. Process & instrument
data sheets. Operating manuals. Training manuals. |
Hazards Carcinogens (PAHs,
benzene). Explosive process gases. Highly flamable
byproducts. Poisonous process gases. Corrosive process
liquors. Hot surfaces and
materials. Heavy moving battery
machinery. Liaison Other engineering
disciplines. Drawing office. Sales and proposals
departments. Project management. Estimating and
procurement departments. Clients. Commissioning engineers. Suppliers. Standards etc. BS 5345 - Hazardous area
classification. Internal working
instructions. Commissioning plan. Site safe working procedures. |