A Process of Utilizing Galvanizers' Waste.
Year: 1891

page_text: COMPLETE SPECIFICATION.
A Process of Utilizing Galvanizers' Waste.
I, RICHARD JONES BRICE of 10 Atherton Road Forest Gate, London Merchant,
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:-
Galvanizers' waste consists of two quite different products, one more technically
known as "sal-ammoniac skimmings" and the other as "zinc-ashes." As is well
known, the first product is secured by skimming the top of the galvanizing-bath
when it is covered with sal-ammoniac, while the second, though usually containing
a very small percentage of sal-ammoniac, is obtained by skimming the surface of
the melted zinc when the sal-ammoniac has been practically swept back or skimmed
off, or by skimming off the surface of scrap zinc while that is being melted alone.
Oxidation produces both substances, but they are quite different in their constituent
parts.
If immediately run into casks, as they are by careful galvanizers, the sal-
ammoniac skimmings may be very readily and economically treated by the process
I am about to describe; but if thrown about anyhow and anywhere they are some-
times so affected by the exposure as to need a preliminary pulverization, and
though this same process may be then employed it is not of so much benefit, as the
expense and difficulty of pulverizing are not thereby avoided. I have heretofore
discovered a method of treating the waste if it must be first pulverized; but, as
stated, the present process is especially useful in treating the carefully-preserved
waste without a preliminary pulverizing.
As the waste comes from the galvanizer the zinc, ammonia, and chloride it contains
are so united as to be of little value, and to separate these elements or some of them
and so treat them as to render them of use is the object of my process, it being
premised that to be a practical success such process must be inexpensive, and in
this respect the present far exceeds all previous methods. In practising it I proceed
as follows:-
First. I take a given quantity of the sal-ammoniac skimmings, and placing it in a
suitable vessel, preferably an iron pot, subject it to heat until it is in a state of
fusion, which usually takes place at about 500° Fahrenheit. The metallic zinc will
settle to the bottom and may be drawn off thence through an aperture in the lower
part of the vessel, suitably located, and alone or together with the metallic zinc
screened out of the ashes, as hereinafter set forth, may be run into ingots, forming a
good quality of spelter. During the fusion of the waste I have prepared a tank of
water heated to about 212° Fahrenheit, the quantity of water being about thirty
gallons for each one hundred pounds of the material.
Second. I gradually add the waste, now in a state of fusion, to the heated water,
which is preferably well stirred during the operation.
I find that by so doing the particles of waste will be and remain so disintegrated
as to readily pass through an eighty-mesh sieve and to be easily acted upon by any
subsequently-added agent much more fully than would be possible had said agent
been added during the fusion or had the water been added before fusion, and it is
in this relative arrangement of steps that the main feature of my invention
consists.
To the mass thus disintegrated I add lime, in the form of milk of lime, to
precipitate the zinc, using of quicklime a quantity about twenty per cent. in weight
of the raw skimmings under treatment, the water in which the lime is dissolved

page_text: being sufficient in quantity and temperature to reduce the temperature of the mass
to about 120° Fahrenheit, which permits and assists the precipitation, giving
practically two products, chloride of calcium in solution, and an oxychloride of zinc
as a precipitate. If the ammonia is of moment, the first is drawn off and the
ammonia recovered from it by adding a little slaked lime (about five per cent.), and
then distilling off the ammonia in the ordinary way. The precipitate is now in
condition to be used as a pigment, provided excess of moisture is driven off, which
may be done by filter pressing or by furnacing, the former being preferable as by
it more of the chloride of calcium. is also driven off, leaving the proportion thereof a
little less than it otherwise would be.
To the second (the precipitate) I add a quantity of zinc-ashes, about one
hundred per cent. in weight of the quantity of skimmings originally treated, first
screening out from the ashes the rough particles of metallic zinc.
These particles as above noted, may be, with or without the metallic zinc of the
sal-ammoniac skimmings, placed in a sweating-furnace, run into ingots and used as
spelter. The mass of the precipitate and the zinc ashes, now in a thick paste is
then dried, and on being calcined becomes much lighter in colour, and can be
pulverized also if desired. (A cyclone-pulverizer is useful for this purpose.) It
may then be ground in oil and forms an excellent paint.
If the product is to be used as a pigment, it is not always necessary to run off the
chloride-of-calcium solution, as above stated, but to the entire mass ashes which are
more or less an oxide, and absorbent may be added, varying the proportion in such
case to about two-thirds ashes to one-third sal-ammoniac skimmings, the additional
lime therein in no way injuring the product for the use named.
The product is now calcined as before mentioned.
This product is practically an oxychloride of zinc, for, as will be remembered, the
elements necessary for the formation of such product have not been removed. Its
use as a pigment is, I believe, new with myself, and either ground in oils or mixed
with colours it forms a paint of more than ordinary body and durability, having
excellent covering and drying qualities.
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 :-
1. The process of treating sal-ammoniac skimmings, which consists in fusing them
and gradually adding the fused mass to a quantity of water heated to about the
boiling point, substantially as set forth.
2. The process of treating sal-ammoniac skimmings, which consists in fusing them,
separating the metallic zinc from the remaining portion of the fused mass, substan-
tially as set forth, gradually adding said remaining portion to a quantity of water
heated to about the boiling-point, precipitating the zinc by adding milk of lime, and
separating the products by running off the solution, all substantially as set forth.
3. The process of treating sal-ammoniac skimmings, which consists in fusing them,
separating the metallic zinc from the remaining portion of the fused mass, substan-
tially as set forth, gradually adding said remaining portion to a quantity of water
heated to about the boiling-point, precipitating the zinc by adding milk of lime,
separating the products by running off the solution, and calcining the precipitate,
substantially as set forth.
4. The process of treating sal-ammoniac skimmings, which consists in fusing them,
separating the metallic zinc from the remaining portion of the fused mass, substan-
tially as set forth, gradually adding said remaining portion to a quantity of water!
heated to about the boiling point, precipitating the zinc by adding milk of lime,
adding zinc ashes, and calcining as set forth.
5. The process of treating sal-ammoniac skimmings, which consists in fusing them,
separating the metallic zinc from the remaining portion of the fused mass, substan-
tially as set forth, gradually adding said remaining portion to a quantity of water i

page_text: heated to about the boiling point, precipitating the zinc by adding milk of lime,
separating the products by running off the solution, adding zinc ashes and calcining
as set forth, thus forming a pigment substantially as described.
Dated this 9th day of September 1891.
S. S. BROMHEAD,
97, Newgate Street, London, E.C., Agent for Applicant.