Improvements in 'the' Utilization of Sewage Sludge.
Year: 1893

page_text: Date of Application, 6th Nov., 1893
Complete Specification Left, 7th Aug., 1894-Accepted, 8th Sept., 1894
PROVISIONAL SPECIFICATION.
Improvements in 'the' Utilization of Sewage Sludge.
I, THOMAS TWYNAM, of Egham Hill, Egham in the County of Surrey,
Analytical Chemist, do hereby declare the nature of this invention to be 'as
follows:-
In the treatment of liquid sewage by chemical agents, such as lime, alumina änd
iron salts, a bulky precipitate is produced & known as sewage sludge. This
material contains a large amount of organic matter mixed with the mineral matter
of the sewage & the material used as a precipitant.
A small percentage of ammonia and of phosphoric acid is always present in the
sludge, but the percentage of either of these bodies is usually too small to give the
sludge a market value, so that it is often used for filling up waste land, or is taken
out to sea, etc..
I propose to utilize this material (when roughly dried) by using it in the blast
furnace when making phosphoric pig iron. The carbonaceous & volatile matter
in the sludge serves as part of the requisite fuel, the lime & alumina going to form
a fusible slag, & the iron oxide present being reduced to metal, whilst the
phosphoric acid is all reduced, the phosphorus entering the pig iron and being
eventually recovered as a valuable manure in the form of basic slag when the
pig iron is used in the manufacture of basic steel. All the ammonia & ammonia
forming bodies in the sludge. are contained in the gases issuing from the blast
furnace, and are readily recovered therefrom together with the ammonia from the
balance of the fuel used.
The well pressed sludge should be roughly dried, either by waste heat or
otherwise in which condition it forms hard lumps very suitable for charging.
Dated this Fourth day of November 1893.
COMPLETE SPECIFICATION.
Improvements in the Utilization of Sewage Sludge.
I, THOMAS TWYNAM of Egham Hill, Egham in the County of Surrey
Analytical Chemist do hereby declare the nature of this invention and in what
manner the same is to be performed, to be particularly described and ascertained
in and by the following statement :—
In the treatment of sewage by chemical agents, such as lime, alumina and iron
salts, a bulky precipitate is produced known as sewage sludge. This material when
well pressed by mechanical means forms a hard cake containing a large amount of
organic matter mixed with the mineral matter of the sewage and a great part
of the lime etc. used as a precipitaut. A small percentage of ammonia, and of
phosphoric acid is always present in the sludge but the percentage of both these
bodies is usually too small to give the sludge a market value, so that it is often
employed for filling up waste land, or is taken out to sea etc.
I propose to utilize this material, when well pressed, and roughly dried, by using
it as part of the material charged into a blast furnace when making phosphoric
pig iron. The carbonaceous and volatile matter in the pressed sludge (generally
amounting to about 30 per cent.) serve as part of the requisite fuel, the lime and
alumina go to form a fusible slag, the iron oxide present being reduced to metal,

page_text: whilst the phosphoric acid is all reduced to phosphorus, which enters into the
pig iron, being eventually recovered as a valuable manure in the form of basic
slag, when the pig iron is used in the manufacture of basic steel. All the ammonia
& the ammonia forming bodies in the sludge are contained in the gases issuing
from the blast furnace, and are readily recovered therefrom by condensation in the
ordinary way, together with the ammonia from the balance of the fuel used. If
no ammonia condensing plant is attached to the blast furnace the pressed sludge
may be charged into the calcining kilns; with the iron ore, & afterwards charged
into the blast furnace.
When the pressed sludge from a large town is utilized in the above way, lime
and iron chlorides may be very advantageously used as sewage precipitants. The
rougher silicious matter should be separated from the sewage as far as possible
before precipitation.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what I
claim is ;-
The bereinbefore described process for utilizing pressed sewage sludge.
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