Improvements relating to the Purification of Sewage and the Con- sumption of Town Refuse, and to the Utilization of Sewage and, Town Refuse for Obtaining Motive Power; and to. Apparatus- therefor.
Year: 1891

page_text: Date: of Application, 9th July, 1891-Accepted, 26th Sept., 1891
COMPLETE SPECIFICATION.
Improvements relating to the Purification of Sewage and the Con-
sumption of Town Refuse, and to the Utilization of Sewage and,
Town Refuse for Obtaining Motive Power; and to. Apparatus-
therefor.
I, EDWARD CHRISFIELD, of Spring Gardens House, Milton next Sittingbourne,..
in the County of Kont, Sanitary Engineer 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 :-
My invention relates to the treatment of sewage for the purpose of purifying
the same and converting it into steam applicable as a motive power for producing
electric lighting, propulsion of mill gearing and the like previous to its discharge
into the sea or into a river or affluent, and to the consumption of town refuse. My
invention also relates to apparatus applicable for the above named purposes.
According to my invention I purify sewage by boiling or evaporating the same
in a suitable vessel. By this method or process the liquid portion of the sewage
is evaporated and changed into steam at any desired pressure, and the solid
impurities are thrown down and collected as a harmless sediment in the bottom
of the evaporator or boiler. This sediment may be removed in any suitable
manner or as hereinafter mentioned.
An important feature of my invention consists in the employment' of town
refuse as a fuel for evaporating or boiling down the sewage. This use of town
refuse not only serves as an advantageous mode of disposing of such refuse, but
it enables the sewage to be treated according to my process in a very economical
manner.
Another important feature of my invention relates to the employment of the
sludgo or sediment separated from the liquid portion of the sewage as a fuel.
This fuel is burnt and the heat therefrom is used to assist in boiling or evaporating
the sewage. I thus provide for very advantageously disposing of the combustible
portions of the said solid portions of the sewage.
By evaporating the liquid parts of the sewage I obtain a very valuable
commodity, that is to say steam, which I propose to use for motive power purposes;
as for instance, for driving dynamo engines and so obtaining electric light at a very
small cost, or for driving other engines, pumps, pulsometers or the like: If'the
steam is not required for motive power purposes it can be condensed in a suitable
condenser and allowed to flow into the sea, or into a river or affluent adjacent to
the sewage works.
Whether the steam'is condensed directly it comes from the evaporator or is first
used as a motive power and condensed subsequently, in either case it is reduced' to
a pure liquid which may be allowed to flow into an affluent without fear of
contaminating the same.
My said invention, moreover, comprises the construction' and arrangement of
special' apparatus for carrying out' my improved method or process.
The terms sewage and town refuse above used and hereinafter also frequently
employed' are meant to be interpreted as follows-that is to say, 'by sewage I mean
the liquid or solid excremental or other matter collected in and discharged' from
town and other sewers, and by town refuse I mean the usual contents of the ashbins
of dwellings, hotels; offices, warehouses and the like, and commonly known as
"breeze" or "rough-stuff" such contents being made up mainly of ashes,” straw,
paper, rags, old-garments and the like.
According to my invention, the sewage is preferably first partially purified by
allowing the same to flow through screened coal ashes which may be obtained'
гр..

page_text: from the town refuse. By this means a considerable proportion of the solid
matter is filtered from the sewage and the partially clarified sewage is then allowed
to flow into suitable storage pits or reservoirs constructed for the purpose at the
outfall whence it is pumped as required into the boiler.or evaporator. While in
the said pits, a further considerable settlement of solid matter takes place and this
is-advantageous as it reduces the amount of work required to be done by the
evaporator. Such sludge as is collected in the ash filter and as settles in the
storago pits, may be utilised as fuel in the sludge consuming furnaces of my
evaporating apparatus in conjunction with the town-refuse, as hereinafter described.
From the settling or storage pits, the sewage is pumped as required through a con-
denser where it is utilised for the purpose of condensing the surplus steam given
off by the evaporator and is itself raised in temperature. After leaving the
condenser the sewage is still further heated by being passed through a superheater
situated in the main smoke flue of the evaporator or evaporators and thence the
sewage enters the said evaporator or evaporators at a temperature approaching the
boiling point and is therein raised to a very high temperature, the liquid portion
being thereby changed into steam and the solid matter deposited and collected as a
sediment. The steam is used as a motive power agent and then condensed, or
where the steam or a portion of it is not required for this purpose, it is condensed
in a suitable condenser and thereby changed into pure water which is allowed to
flow away into a river or affluent. The solid sediment is removed from the
evaporator at intervals and is preferably burned to assist in evaporating the sewage
and raising steam.
In the accompanying drawings I have shown how my said invention. may, be
conveniently and advantageously carried into practice.
Figure 1 is a vertical central longitudinal section of one end of my improved
double ended boiler or evaporator designed for treating sewage according, to my
invention.
Figure 2 is a balf front elevation of the said evaporator and half section on the
line XX Figure 1, the mechanical stokers hereinafter described being, removed
from the sectional view.
“Figure 3 is a partial side elevation showing the feeding floors and the driving
gear for the mechanical stokers.
Figure 4 is a plan of one end of my apparatus one half showing the mechanical
stokers; and the other half showing the arrangement of fire bars between which the
stoker arms work, and also showing the clinker pit and combustion chambers in
horizontal section.
11
Figure 5 is a vertical central section, and
Figure 6 is a horizontal section through the tubes of a condenser and circulation
tank or shell both drawn to a smaller scale, suitable for condensing: the steam given
off by the aforesaid boiler or evaporator, and for heating the sewage.
Figure 7 is a plan showing the arrangement of a group of evaporators super-
heater and condensers.
Like figures represent corresponding parts throughout the drawings.
A is a boiler or evaporator having three longitudinal flue tubes, a central one a
of the section, shown in Figure 2 and two circular side flue tubes. a' also clearly
shown in Figure 2. The shell of the evaporator is not. circular in transverse
section but is made of a shallow crown A' two curved sides A and an inwardly
curved bottom A³ the crown and the bottom being struck from the same centre
below the evaporator, and the two sides from different centres. This construction
results in the formation of two narrow valleys or.channels B, B (for the collection
of sludge) between the bottom and the sides extending the whole. length of the
evaporator. The shell is composed of boiler plating. of suitable thickness, and tho
sides and crown are suitably strengthened by means, of transverse ribs a' which
are rivetted thereto at intervals. Strengthening gusset stays a are also. provided
in the angles between the crown and the sides, and increased lateral strength is
ensured by means of internal transverse stay rods a, a series of such rods being

page_text: arranged above and another series below the flue tubes. The end plates are made
of suitable strength and are attached to the shell and to the longitudinal flue
tubes in the ordinary manner. The said end plates are provided with openings or
Boot doors to permit of examination of and removal of soot from, the internal
tubes. Expansion joints A' of any suitable or ordinary description are provided
both in the shell and in the longitudinal flue tubes to permit of variable expansion
and contraction without injury to the ovaporator. The crown A¹ of the shell is
provided with suitable seating blocks for the manhole covers, stop valves, and.
safety valves as in an ordinary steam boiler. Suitable pressure gauges and glass
sewage water gauges are also provided. The evaporator is set on suitably shaped
fire brick seating blocks C C carried by two side seating walls C, C and the
boiler is heated by external fires. Owing to the peculiar shape of the shell three
furnaces or fire places D are naturally formed, one between the seating walls C
and one on the outer side of each said walls. The crowns D' of the said furnaces
are closed in a little below the level of the top of the boiler sides. Below these.
furnaces I provide three other furnaces as hereinafter described. The evaporator
is double ended and has the same number of furnaces at each end. A mid partition
wall C is provided to prevent the gases from the furnaces at one end intermingling
with those at the other. It will also be seen that the furnaces at each end are
separate and distinct from each other and that the products of combustion from
one cannot mingle with those of the other. A number of small tubes b provided
at suitable intervals connect the sides and bottom of the boiler shell with the
central flue tube a and side flue tubes a' and form a free communication from the
furnaces to the interior of the said flue for the passage of the products of com-
bustion. Moreover other tubes connect the said tubes a¹ to the central tube a,
to serve as outlets for the gases entering the said tubes a', and from the central
fluo tube a a large vertical exit flue is provided in the centre of the evaporator
leading out through the crown of the shell to a main brick flue E which conducts
to a chimney stack. The central flue tube a is also provided with cross sewage
water tubes a and the side flue tubes a' are provided with sewage water pockets a®
in their crowns.
The flanges of the tubes b, b' and of the exit tube 62 and of the
sewage water tubes a and pockets a are all curved to the radius of the plates to
which they are intended to be attached. The furnace gases from all the furnaces
at both ends of the evaporator pass through the tubes and enter the longitudinal
flue tubes a, u¹ and from the latter through the tubes into the flue tube a where
they mix with each other surrounding the water tubes and pockets and then pass
out through the main exit fluc into the main flue E through the superheater and
thence to the chimney. The portions of the flue E which are immediately over
the crown of the evaporator are supported by cast iron girders E'. I provido a
sliding damper e at the upper end of the exit tube 6 for regulating the outlet area.
The said damper is carried by rollers c' to reduce the friction and is provided with
a rack that gears with a toothed wheel mounted on a shaft spassing out
through the sides of the flue E and having secured on its outer ends hand wheels c
whereby the damper may be actuated from either side of main flue to open and
close the flue. Fis the feed pipe for conveying the sewage to the evaporator ;
FF are stop valves for shutting off the connection when desired. G G are
sludge pipes or blow off pipes one such communicating with each channel or
valley B at each end. In some instances I feed the evaporator through the sides
instead of at the front. For this purpose I employ a closed trough F' placed by
the side of the boiler and communicating therewith by a number of inclined feed
pipes F which pass through the side furnaces as shown by dotted lines in Figure 2.
By this arrangement the sewage is heated by the furnace gases before entering the
boiler, and any deposit of sludge thereby caused to take place in the said inclined
feed tubes will flow back into the trough F' whence it can be removed at intervals
by hand. The fire bars H of the oxternal furnaces as clearly shown in plan in
Figure 4 are constructed with suitable openings H¹ to admit of the projection
therethrough of the arms of a slowly revolving mechanical stoker. This stoker

page_text: I
consists of a series of arms or wings I fixed on horizontal shafts 'I' that 'are
situated immediately below the fire bars Hand-are carried by bearings 'I' mounted
in the walls C. The said shafte I' are slowly rotated as follows that is to say, on
the end of each shaft'I', is fixed a worm wheel I see Figure 3 that gears with a
worm I fixed on a common shaft 1 carried by bearings I. With the shaft is
coupled by gear wheels 'I, I another shaft 1 which is carried by suitable 'bearings
and on which is fixed a bevel wheel I that gears with a 'bevel wheel Jon a
shaft J carried by bearings J' and traversing the front of the boiler. The said
shaft J is provided with fast and loose pulleys and is driven from any convenient
motor, the belt being thrown on the loose pulley when the automatic stoker is
required to stop. The arms I rotate very slowly and during their rotation they
gradually feed the fuel forward along the grate or fire bars H until it reaches the
farther end, where any unburnt ash or clinker is discharged over the end of the grate
and falls through a clinker pit K' and by way of a door K' into the ash pit K below
the furnaces. The arms are cooled by passing through sludge or other liquid lying
in the grooves cut to allow of their rotation in the fire brick crowns of the sludge
furnaces. Beneath each furnace D, I build another furnace D* intended for the
consumption of the sludge discharged through the blow-off pipo G. These furnaces
I propose shall be fed by hand through the sludge manholes in furnace crowns
hereinafter mentioned and through the furnace doors D' that are provided at their
front ends. The crowns of the furnaces D* are formed of fire brick slabs D built
into the seating walls C and side walls. C. In each said furnace crown is provided
a sludge man-hole D adapted to be closed by a door D as shown in Figure 1.
For opening the said doors a suitable chain D³ is provided, the said chain being
attached to the door at one end and after passing over a suitably placed guide
pulley D'
passes out to the front of the furnace. When required the door is closed
by means of a stoking iron inserted into an eyebolt D provided for that purpose.
The blow off pipe G is provided with two branches G' arranged to discharge
through their open ends G upon the slabs D, a suitable sluice valve G³ (shown
only in Figure 1) being provided in each branch to regulate the discharge or to
stop the outflow altogether when desired. It is obvious that any sludge delivered
on the slabs D can be discharged' into the furnaces D below the said slabs by
opening the doors D. Such sludge discharged into the furnaces D* will be burnt
along with other fuel fed by hand through the sludge manhole or through the
furnace doorway D'. Any vapour that may arise from the moist sludge being
discharged on the highly heated fuel or refuse in sludge consuming furnace will be
absorbed by having to pass through the hot gases of the top furnaces by way of the
clinker pits or of the combustion chambers. The object of feeding refuse or fuel
through the sludge manhole after sludge has been deposited in the furnace D* is to
cover the said sludge and prevent scalding of the attendant which might occur in
opening the furnace door D* were the sludge left uncovered. The front ends of all
furnace or fire bars are carried by suitable Tahaped moveable cast iron bridges H³,
lying on cast iron brackets built in the seating and side walls.
The back ends of bottom furnace bars are carried by suitable I shaped girders H
'the ends of said girders being built into and carried by the seating or side walls.
*The back ends of top furnace bars are carried by dwarf fire brick walls H' these
said walls forming closed back ends to mechanical stokers and sludge pits thus
preventing the escape of hot gases from the sludge or bottom furnaces. At the
internal end of each furnace is provided a combustion chamber L, the ashes and
clinker from the upper or mechanical stoker furnace being prevented from falling
into this chamber by means of a fire bridge or arch 1. built in rear of the clinker
pit K. At the rear end of each furnace D* is a hinged door K³ on which the asbes
and clinker from the upper and lower furnaces collect and which can be opened
when desired for the purpose of discharging the said clinkers and ashes into the ash
pit K. The door is held up by a chain K which is attached at one end to the door
and passes over a guide pulley K' and out at the front of the furnace the door being
held up by a suitable counter balance weight attached to the end of the chain. In

page_text: each of the upper furnaces I burn only town refuse which I feed to the fires as
follows, that is to say, in front of each furnace I provide a large hopper or bin M
capable of containing say a cubic yard or an ordinary cart load of refuse. At the
lower end of each hopper I provide a feed chamber M¹ having a mouth M³
projecting over the front end of the fire bars H. In the said feed chamber M and
opposite the mouth M' thereof I mount in suitable bearings a pair of coarse pitched
worms or screw fuel propellers N adapted for feeding the refuse and delivering the
same through the mouth M' to the fire bars H. To drive the propellers N. I fix
on the front ends of the axles N thereof worm wheels N' arranged to gear with
worms N' fixed on the driving shaft J. The said shaft J thus serves to drive both
the screw propellers and the mechanical stoker arms I.
The above construction of evaporator and furnaces enables ample furnace space
to be obtained for the burning of town refuse and the sides of the evaporator being
inclined outward they are brought well over the side fires and therefore good
contact with the flames is ensured or in other words the plates are advantageously
placed for absorbing the heat. For convenience in feeding and attending to the
evaporator, provide three floors at different levels, one O situated at a convenient
level for tipping the refuse into the bins or hoppers M, another O' at the mechanical
stoker furnace level, and a basement floor () at a convenient level for attending to
the sludge consuming furnaces. moreover prefer to continue the floors around
the sides of the evaporator or I provide corridors at each floor level between the
evaporators where two or more evaporators are placed together in the same range
so that the attendants can readily pass from one end of the evaporator to the other.
All the furnaces, combustion chambers, partition walls and other walla subject to
the action of the flames and hot gases are preferably lined with fire brick and
the evaporator seating and side walls are built on concrete or other suitable
foundations.
The steam generated in the sewage evaporator I propose to use for driving steam
engines, pumps, pulsometers and the like or utilize it for any purposes for which
steam is available. In particular it is used in the engine which drives the
mechanical stokers above described and in the steam sewage pumps required for
feeding the evaporators and it may be used for driving electric generators and so
enable the electric light to be obtained far more cheaply than is possible where coal
or like fuel is used to generate the steam required for driving the engines or in
other words I am enabled by my process and apparatus to supply a town for
example with electric light at a very small cost by means of the refuse and sewage
derived from such town. If the steam is not required for motive power purposes I
may condense it at once and then allow it to flow away in the state of pure water
into an affluent. In Figures 5 and 6 I have shown a suitable surface condenser for
this purpose the sewage being employed as the condensing medium. P is the
condenser which consists of an upper wrought iron steam chamber P, and a lower
cast iron condensation chamber the said upper and lower chambers being joined
together by a number of vertical tubes 13 the chambers being constructed and the
tubes fixed therein in any suitable manner. The condenser is carried by suitable
dwarf walla Q. The base plate of the condensation chamber P is provided with a
broad flange P which is strengthened with a number of strengthening ribs P³. To
the said flange I secure a cylindrical wrought iron tank, R which is closed at the
top by the top plate of the steam chamber P. In the floor of the tank R which
is formed by the flange P I provide sludge valleys P as indicated in the figures,
and with suitable blocks P cast thereon for the attachment of sludge ontlet
pipes P. Sewage is pumped as above described into the tank R through an inlet
pipe R' and surrounds the tubes P³ and thereby condenses tho steam which is
passing through the said tubes. The heated sewage is forced out through an outlet
pipe R. The steam is conveyed to the chamber P1 by a pipe P' and the water
Hows away from the condensation chamber through a waste pipe P. To ensure
the dispersal of the steam as it enters the chamber P 1. provide a baffle plate S
supported by suitable brackets at about mid-height in the chamber P', which

page_text: plate operates to check the inrush of steam and to spread the steam over the whole
of the tubes P³.
In Figure 8 I have shown a general plan of a battery of four evaporators with
their respective condensers and superheater. T T indicate the steam pipes leading
to the condensers and U a main steam pipe for conducting steam to engine, pump
or the like. E is the chimney stack, the condenser cold sewage supply pipe R¹
and pure condensation waste pipes P and the sludge inlet pipe P are also indicated
in this view.
For further heating the sewage previous to its entry into the evaporator I
provide a superheater V of a similar construction to the condenser hereinbefore
described the tubes being utilised for the passage of hot gases from the main flue
instead of for steam as in the condenser. The position of the superheater is
indicated in Figure 7 that is to say I place it in the main flue E in a vertical
position.at the end of the range of evaporators. The products of combustion are
conducted to the top of the tubes and thence pass downwards and out at the lower
ends of the said tubes, and from thence to the chimney stack E. The sludge
deposited in this superheater is collected in a central sludge valley V₁ and is
extracted by means of two sludge outlets V as in the manner described with
reference to the condenser. R2 is the sewage inlet pipe coming from the condensers
and VV are the sewage outlet pipes ono on each side of the superheater 'leading
to both ends of the evaporator or evaporators.
The treatment of sewage according to my improved process is as follows, the
sewage liaving been partially filtered or unloaded of a portion of its sludge or solid
matter and collected in the storage or settling tanks as before described is pumped
therefrom through the condensers and superheater into the evaporator as required
and is there heated and evaporated. The sediment left behind during the process
of evaporation gradually collects in the channels B, and when a sufficient depth
has accumulated the blow off valves are opened and the sludge is blown out on to
the crowns of the sludge consuming furnaces and thence through the sludge man-
holes on to the fires or furnace. The blow off sluice valves are then closed again
until a further accumulation has collected when the operation of blowing off is
repeated the sludge is introduced into the sludge furnaces in the manner above
explained and is there consumed along with other refuse. Moreover the sludge
that settles in the filters, storage tanks condensers inclined heating pipes and
superheater may also be burned in the sludge furnaces after being first partially
dried in any suitable manner. The steam obtained from the boiler is employed for
motive power purposes or is condensed and then allowed to flow away as a pure
water into an affluent or river as the case may be.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :---
First. The herein described method or process of purifying sewage and con-
suming town refuse consisting in burning the refuse and evaporating the sewage by
heat derived therefrom, thus transforming the liquid portion of the sewage into
steam applicable as a motive power agent for the production of electric light or for
other purposes or where the said steam is or is not required as a motive power
condeusing the same in suitable condensers by the sewage or by other available
condensing medium thus transforming the said steam into a harmless liquid, the
solid matter of the sewage being separated by and during the boiling or evaporating
process and thrown down or deposited in a suitable condition for collection and
removal, substantially as set forth.
Second. The herein described treatment of sewage prior to evaporating same,
consisting in passing the sewage through an ash filter before or after entering
storage tanks, then pumping it on its way to the evaporator through a condenser
and finally through a superheater or other heating devices as and for the purpose
specified.

page_text: Third. The employment of the sewage as a means of coudensing the surplus steam
given off by the evaporator substantially as set forth.
Fourth. The employment of sewage sludge as fuel for evaporating sewage sub-
stantially as set forth.
Fifth. An externally fired evaporator constructed with internal longitudinal flue
tubes closed at the ends and with cross smoke tubes leading to the said longitudinal
flue tubes from that portion of the shell exposed to the fires, and with one or more
outlet smoke tubes leading through the, crown of the evaporator to the main flue
the said flue tubes being constructed with or without cross sewage water tubes and
pockets substantially as set forth.
Sixth. The evaporator constructed substantially as herein described for the
purpose specified.
Seventh. The mechanical stoker comprising the feed hopper the screw propellers
for delivering the fuel to the furnaces and the revolving arms for slowly advancing
the fuel along the fire bars constructed and operated substantially as hereinabovo
described.
Eighth. The rotating mechanical stoker arms or wings in combination with the
fire bars which are constructed and arranged to receive the said arms or wings
substantially as described.
Ninth. The construction and arrangement of the furnaces so as to allow of
feeding the sludge to the lower furnaces substantially as specified.
Tenth. The surface condensers provided with a baffle plate substantially as and
for the purpose specified.
Eleventh. The apparatus constructed substantially as described with reference
to the accompanying drawings and operating as and for the purpose specified.
Dated this Oth der of Julv 1891.
EDWARD CHRISFIELD.
Haseltine, Lake & Co.,
45, Southampton Buildings, London, Agents for the Applicant.