IMPROVED PROCESS FOR UNTINNING TIN-PLATE REFUSE IN HERMETICALLY CLOSED APPARATUS & AT THE SAME TIME OBTAINING AMMONIA
Year: 1884

page_text: COMEDE
I, LUDOLPH POENSGEN of Dusseldorf in the Kingdom of Prussia do hereby
declare the nature of the said Invention for "IMPROVED PROCESS FOR UNTINNING
TIN-PLATE REFUSE IN HERMETICALLY CLOSED APPARATUS & AT THE SAME
TIME OBTAINING AMMONIA" and in what manner the same is to be performed, to
be particularly described and ascertained in and by the following statement:-
The following process has for its aim the separation of the tin from tin plate
cuttings, and the utilisation of the products obtained (by this process), namely
iron, tin, tin salts, and ammonia on the manufacturing scale and separate from
each other.
The solutions made use of for dissolving are aqueous solutions of alkalies, which
for the purpose of untinning and at the same time extracting the ammonia are
replaced by saltpetre.
As the objects to be untinned are for the most part very bulky, it is advisable
and requisite to reduce the size of the same, and as moreover the solutions of
alkalies made use of are apt to absorb and take up carbonic acid from the air and
by this means become weaker, and as lastly the dissolving medium acts most
powerfully and quickly in a warm state, it is advantageous to perform the untinuing
operation in large hermetically scaled apparatuses which are capable of being heated.
The above named conditions are realised in the apparatuses forming the subject of
the accompanying Drawings.
Figs. 1 & 2. are two similar apparatuses placed side by side viewed in elevation
and cross section.
Fig. 3 is a longitudinal section through the apparatus.
Fig. 4. Plan view (bird's eye view).
Fig. 5. A section through the lower part of the apparatus.
The apparatus consists of the inner vessel a which has an opening in the bottom
to which a steam tight tube c is fixed in order to allow the volatilised ammonia
vapours to reach the reservoir C and beyond. The lye can also reach the reservoir C
should it boil over, and after cooling there flows back again. The tube c is on this
account to be made as wide as possible, and the stuffing box on the vessel C is to
be fixed very deep. The ammonia which is distilled out of C through a suitable
wide tube passes at first through a gas filter, and then into well cooled receivers
partly filled with water or acid, where it is absorbed, and after sufficient concentra-
tion is from time to time drawn off.
In the cover of the vessel a, there is a manhole which can be hermetically closed
by a suitable lid, and a support d in which the filter tube e can be introduced;
on the inner wall of the vessel a there are inclined paddles f l. The vessel a

page_text: is surrounded by the steam jacket ƒ or by a suitable heating apparatus in order to
keep the lye warm in the vessel a.
On the outside periphery of the casing a cogged or chain wheel g is fixed. The
steam casing must be screwed tightly on the flange of the vessel a, it is closed
underneath with a lid h which is provided in the middle with a stuffing box i
through which passes a tube K which is fastened outside; this tube K is provided
on the outside end likewise with concentric stuffing box 1, right through which, as
also through the stuffing box n, the pipe c extends into the reservoir C. On
the reservoir C there is, besides the stuffing box n, the safety valve V, another
support O, drawn in Fig. 3 in dotted lines, in connection with the gas filter, and the
receiver and a support p, in order to provide a steam pipe connection.
The tube K has likewise two other supports, a support 9 as a junction to the
main steam pipe, and another through which the pipe runs for the condensed
water which gathers in the casing. To the various supports conducting pipes are
fastened, the use of which will be explained by the following description of the
working of the apparatus. The apparatus is supported at both flanges by rollers ro
in order that it may be easily revolved.
The working of the apparatus is as follows:-
The thoroughly purified tin plate refuse is filled in through the manhole m
to about line, x, when the charging is done the manhole m is closed, and by
opening of the valve v steam is forced out of the main pipo z through the whole
apparatus until the air is driven out, then the alkali ye with the addition of
saltpetre is allowed to enter, and finally the support d quickly closed with false
flange and valve v³.
Now steam is let into the jacket by valve v³, in order to heat the lye which is in
the vessel, whereby condensed water gathers at the lowest point of the steam
casing and through the condensed water drain pipe which remains stationary and
reaches quite close up to the edge of the casing, flows into a suitably arranged
cistern. Then the whole apparatus is placed in a backwards and forwards or
oscillating motion by means of tooth wheeled gear, whereby the paddles f 1 partly
raise the material to be untinned throwing it now to the right now to the left.
The untinning accomplished, which is ascertained by experiment, the apparatus
is again so placed that the support d is in its highest position, the false flange taken
away, and the filter tube with closed valve screwed thereon is quickly placed
inside and screwed on steamtight. Then the support d is brought to its lowest
position and a conducting pipo is fastened on to the valve v³, which is preferably
connected with a second similar apparatus however, this latter is not actually
'necessary, but care must then be taken that the vessel in the Drawing marked w
is made of sufficient size. When two apparatuses are used, this vessel need only
be made of such a size that it can contain the lye which remains behind in the
conducting pipe. This vessel w is so arranged that the lye which remains in the
conducting pipe flows in by itself into cock h¹, which is fixed over it (s Fig. 3)—
Further there is on the upper rim a steam junction with valve v, and underneath a
pipe that can also be closed with flange screwed thereon, which opens close to the
bottom of the vessel.' The height of the last support above the bottom of the
vessel is so arranged that there is room for all the lye in the closed conducting pipe
underneath the same, so that as soon as the excess pressure in vessel w ceases, it
flows back into the latter and thereby, by closing the lower valve ³, lye can be
preserved without access of air. When one of the above mentioned connections is
made, then steam is let into the apparatus by valve v³, valve v³ can likewise be
opened and the lye forced in this manner through filter e either into the second
apparatus or in the vessel w.
When the lye is completely saturated with tin, it can be forced direct into a cistern
for further treatment. In Fig. 3 this is indicated by a dotted pipe connection. As
soon as the lye is forced out, valve v¹ is then closed, whereupon the lye which is
found in the pipes which are placed above will flow-back; then valve v³ is closed,
"disconnected, the support d turned round as far as a connection with a water pipo
-

page_text: and, water let in in order to wash the residues. This is done after disconnecting
the water pipe by an oscillating movement of the apparatus. When sufficiently
washed the water is run off in the same manner as the lye, and the operation can
be repeated as many times as necessary.
The removing of the refuse which is found in vessel a out of the same is
performed automatically, the manhole cover m being opened and a slide placed
inside the manhole opening in such a manner that the vessel can rotate without
touching the slide. When the slide is inserted, the apparatus is suitably rotated,
so that the paddles discharge themselves towards the manhole.
The materials which are caught by the paddles then fall upon the slide and in a
short time the drum is emptied.
The materials which have been untinned in this manner are now separated by
means of the patented automatic washing cylinder constructed of perforated tin
plate, or the chaplet mechanism to be described further on, from the adhering
sludge by rinsing with water. The refuse which has been so untinned and washed
does not possess all the good properties of good forging iron, notwithstanding that
of the tinning nothing remains perceptible to the eye. The refuse only obtains
these qualities in the most perfect manner when it is exposed for about 30 to 40
minutes in a chloride solution or any kind of dilute acid which dissolves tin and
iron; the use of hydrochloric acid is recommended for its cheapness. Any practical
man can easily determine the right degree of concentration of the acid and the
time requisite for the operation. At the same time it is easily perceived if the
material has been long enough treated with the first lye or not; for any still
existing ridges of the tinning will be sharply and clearly distinguishable, after its
passage through the acid, against the colour of the corroded iron.
In order to discover if the acid has operated long enough upon the refuse, it is
best to make welding trials with the refuse, from the fracture of which every
practical man will be able to test the purity of the iron, as the iron plates
manufactured into tinned ironplate being almost free from phosphorous and
generally of the best quality cannot but yield a good fracture, provided no tin is
present. The treatment of the refuse with chloride or acids can either take place
directly after the washing in the hermetically closed apparatuses which have been
described, or in the moving drums in tubs made of perforated sheet iron or in the
chaplet mechanism which will be described further on.
The reaction which takes place on treating with iron chloride or muriatic acid, is
that the tin, which adheres imperceptibly on the materials known to be already
sufficiently treated with the alkali lye, and of which it is not accurately known
whether it is chlorined as alloy of iron and tin, or if it adheres as stannate of soda
in the pores of the alloy of iron and tin, is converted and dissolves as perchloride
from which the tin is extracted according to well known methods.
It is advantageous to assist the chemical processes described, by mechanical
agitation, as in no case is the tin removed where no liquid penetrates, a condition
which occurs when two smooth pieces of tin lie close upon one another; besides
the profitableness of the process depends very much upon the greater or lesser
weight of the material which can be got into a given space without it being
pressed tightly into the space. For these reasons it is of the greatest importance
that the refuse should be broken up as small as possible before putting into the
cleansing drums, provided that it cannot pass through the holes in the lower
drums, or chaplet machine boxes.
A. threefold end is attained by this breaking up,-1st a great deal goes into a
very small space, 2nd by the rotation of the drums the pieces slide over one
another very frequently, and 3rd the adhering together of two smooth surfaces is
avoided as much as possible.
In order to free the untinning refuse from the dirt (slime) which forms during
the process, it is necessary to wash it again.
The moving chaplet machine in closed casing illustrated by Fig. 6 will serve
this end.

page_text: The residues which have passed through the first described machines are put
through the funnel F into the chaplet machine, where it is to be noticed that the
funnel F terminates for this purpose over two charging cylinders (rollers) shewn
dotted in the Drawing, and is continued under the same in a suitably broad
opening. Through this cutting, also drawn in dotted lines, the materials introduced
fall tolerably finely divided into the shovels or boxes of the ladder work. The
shovels or boxes should be made of perforated sheet iron or wire gauze, and
traverse during the washing of the products which they contain, two rows of
steam pipes D, D and finally under water pipes W, W.
The steam as well as the water pipes are provided on one side with a row of
fine nozzles, and are so arranged that the nozzles of the outer pipes correspond to
openings in the sheet iron cover, while the inner pipes have their nozzles arranged
opposite the former. Now when the shovels pass by these, the products which are
to be found on them are thrown hither and thither, any dirt falls through the
meshes of the shovels and flows away with the water through pipe A, whilst the
untinned plates remain in the shovels till they fall into the discharging funnel F,
from where they are from time to time let down into wagons or boxes placed
underneath, whilst the steam which is not condensed in the apparatus is discharged
by means of a pipe R.
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
1st. The application of apparatuses capable of being hermetically closed, and of
working without access of air, to the operation of untinning metallic refuse by
means of alkaline solutions.
2nd. In the untinning of tin plate refuse by means of alkaline solutions and
saltpetre, the recovery of the ammonia gas produced by means of suitable vessels
partially filled with water or acid, and connected with the above mentioned
apparatuses.
3rd. The application of apparatuses capable of being hermetically closed for the
purpose of untinning by means of alkaline solutions, the use of several. similar
apparatuses so arranged that they can be connected with each other by pipes and
valves, or by the taps c, and w, in such a manner as to admit of the alkaline
solution being filtered and stored without access of air.
4th. The combination of the two known chemical processes for untinning by
means of alkali solution and an oxydising substance, and the dissolving of the
tinned surface of the iron by means of acids or chlorides in order to obtain good
welding iron.
5th. In the above named processes, the use of the tin plate refuse for the
purpose of untinning in a finely divided condition, in order to admit of the process
being carried out in apparatuses as small as possible, thereby rendering the already
partially known processes more profitable.
6th. The application of a chaplet or endless band mechanism with shovels or
boxes made of perforated iron plates or wire gauze, which pass in front of pipes
arranged in rows and discharging jets of steam and of water, and thus effecting the
separation of the metallic residues remaining after the untinning in the apparatuses
mentioned in claim 1st, from the sludge formed during the process.