Process for the Production of Cement.
Year: 1886

page_text: Process for the Production of Cement.
I, GILBERT RICHARD REDGRAVE of Sunnyside, Muswell Hill, London, in the
County of Middlesex, Civil Engineer, do hereby declare the nature of my
invention for IMPROVEMENTS IN THE TREATMENT OF SEWAGE WATER and in what
manner the same is to be performed, to be particularly described and ascertained
in and by the following statement:--
Whereas Major-General Scott, in Letters Patent granted to him on the
26th August 1871, No. 2243 described his invention for the production of manure
or cement by treating sewage water with lime and calcining the resultant sludge
in heaps or in a kiln, and further by Letters Patent, dated respectively, March 20th,
1872 No. 849, August 26th 1872, No. 2538, and December 14th 1874, No. 4305, set
forth sundry improvements in the same, I have to state that I am well acquainted
with the system of treatment employed by General Scott-The difficulties
encountered in the manufacture of cement and in the clarification of sewage
water under the above mentioned processes are as follow:-Owing to frequent
fluctuations in the amount of suspended solid matters, washed off the surface of
roads by storms, and arising from the disintegration of fecal matters in the sewers,
the composition of the resultant cement is very uncertain, and the presence of the
detritus in the sludge renders the cement inferior in quality to the best Portland
cement. Further, in consequence of the excess of lime employed for the purpose
of precipitation, the effluent water, after treatment, is nearly always strongly
alkaline, and therefore not suited for discharge into rivers or small streams.
To carry out my invention, which overcomes both these objections, I first add to
the sewage water from sixteen to twenty grains per gallon of aluminous clay,
which is a chemically inert substance, but one which has a very considerable
power of effecting and of expediting the clarification of polluted waters by means
of simple subsidence. This clay I wash, or obtain in a finely divided state,
suspended in water and I cause the sewage and the clay-water to become thoroughly
mixed, by allowing them to pass together along the sewer for some distance, as
described by General Scott, in the case of the lime or other precipitants, in Letters
Patent granted to him, under date of December 2nd 1870, No 3169,
may decrease
the quantity of clay in times of heavy rainfall, or add to the same during very dry
weather, but I regard the above quantity as about sufficient for my purpose. By
CD

page_text: bringing the clayed sewage water to rest in tank No 1 at the outfall, I obtain,
owing to the action of the particles of clay, a rapid deposition of the suspended
natters, together with the silt and detritus. I then divide the effluent water from
tank No 1 into two parts which I will call A and B, the volume of A being
approximately five or six times that of B. To the portion of the sewage water
distinguished as A I add from twenty to twenty four grains per gallon of lime,
slaked to a fine powder, and levigated in water to remove all coarse particles, and
I thoroughly mix this lime water with the clayed effluent from tank No 1, during
its passage to a second tank No 2, by any of the usual methods, preferably in a
channel fitted with alternate baffle-plates. In tank No 2, owing to the chemical
action of the lime and the formation of a precipitate the clarification is very
complete, and the effluent water from tank No 2 1 cause to pass into a third tank,
No 3, where it encounters and mingles with the remainder of the sewage water B
from tank No 1. To this latter portion of the sewage I previously add only from
six to nine grains of lime per gallon, in the manner described for the treatment of
the portion A. The result of this plan of treatment (which I have termed the
differential treatment) is that the excess of line in the effluent from tank No 2 is
expended in completing the precipitation of the under-limed portion of the sewage, B,
in tank No 3, which I make the largest of the series. Moreover, by this addition
of a small quantity of newly limed sewage water to that previously clarified
I obtain a very complete precipitation of the whole volume of the sewage water in
tank No 3. The effluent from tank No 3 has no longer a strongly alkaline
reaction, and one of the principal objections to the lime process is thus overcome.
I find also that the sludge obtained from the differential treatment in tanks, Nos. 2
and 3, consisting as it does of an intimate mixture of carbonate of lime and clay, is
admirably adapted for the preparation of high-class cements, being very free from
detritus, and thus the main obstacle to the use of the lime sludge for the manu-
facture of cement is removed. The final stages of the cement manufacture, in the
case of sewage deposits, are similar in all respects to those in the manufacture of
Portland cement by the wet process. The deposit in tank No 1 may be dug-in
wet as a manure, or it may be air-dried, or disposed of in any convenient manner.
The bulk of it is relatively small as compared with the limed sewage, but it
contains nearly all the matters injurious to the cement.
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 :-
In the treatment of sewage by the lime process, with a view to the manufacture
of cement, the separate addition of clay at some distance from the outfall tanks, in
order that it may become well mixed with the sewage water, the deposition of the
suspended matters and detritus in a subsidence tank, previous to the addition of
the lime, and the differential treatment of two unequal volumes of the clayed
sewage water, with varying quantities of lime and the subsequent remixture of the
same, in order to ensure, as far as possible, the freedom of the combined effluent
from an excess of lime, in the manner herein set forth.
Dated this 15th day of May 1886.