Improvements in the Method of Obtaining Useful Products from Bleaching Powder Dregs and Lime Mud from Paper Works.
Year: 1890

page_text: Date of Application, 28th Aug., 1890
Complete Specification Left, 28th May, 1891-Accepted, 4th July, 1891
PROVISIONAL SPECIFICATION.
Improvements in the Method of Obtaining Useful Products from
Bleaching Powder Dregs and Lime Mud from Paper Works.
I, THOMAS JAMES HUTCHINSON, F.I.C. of Arcade Chambers Manchester in
the County of Lancaster, Consulting and Analytical Chemist, do hereby declare
the nature of this invention to be as follows:-
This invention relates to the method of utilising and obtaining useful products
from the bleaching powder dregs and the lime mud produced in paper works.
According to these improvements I collect the bleaching powder dregs in
intercepting tanks from which I pump or inject it to an agitator whence it is
delivered as milk of lime to the causticising tanks where it is mixed with sodic
carbonate for the production of caustic soda. The lime mud is withdrawn from the.
causticising tanks to collecting tanks from which it is pumped or lifted to a filter
press. The expressed liquid is a weak caustic solution which is returned to the
causticising tanks, and the dry product is CaCO, or whiting which may be sold or
employed in any suitable manner.
Dated this 27th day of August. A.D 1800
WILLIAM E. HEYS,
Agent for the Applicant.
COMPLETE SPECIFICATION.
improvements in the Method of Obtaining Useful Products from
Bleaching Powder Dregs and Lime Mud from Paper Works.
I, THOMAS JAMES HUTCHINSON F.I.C. of Arcade Chambers Manchester in the
County of Lancaster, Consulting and 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 :-
This invention relates to a method of utilising and obtaining useful products from
the bleaching powder dregs and the lime mud produced in paper works.
The common practice in paper works at present is to agitate the bleaching
powder with water and allow it to settle. The dregs are then washed with water
to remove all the soluble chlorine compounds, and are finally thrown away. In
the case of the employment of lime in the production of caustic soda, the solution of
soda ash is treated with lime and the precipitate, which consists of carbonate of
lime, is washed to remove all the alkali possible. The washed carbonate of lime is
then either run into tanks to settle or into the nearest stream or river causing
serious pollution. In each case loss is likely to result from incomplete washing or
from the production of large quantities of weak solutions which cannot be effectively
used.
According to these improvements I mix the bleaching powder with the requisite
quantity of water and allow the mixture to settle. Then, instead of washing the
dregs, I run them into a receiving tank fitted with an agitator by means of which
the partial solidification of the dregs is prevented. The dregs, or milk of lime
from the agitator tank may be run to the causticising tanks where it is mixed
with carbonate of soda for the production of caustic soda solution. When however,
the dregs are produced in large quantities, or where for some reason they
cannot be utilised in the production of the caustic soda solution, they may be
separated into bleach liquor and lime by means of a filter-press and be used in any
convenient manner.

page_text: Instead of repeatedly washing the lime mud produced in the causticising tanks
in the usual manner, I run it into a tank hereinbefore described as being provided
with an agitator and a sludge pump communicating with a filter press, or with a
similarly provided tank, and force the mud or slush from time to time into the
filter press. The press liquors obtained by this treatment are conveyed into the
caustic pans, and the strength being taken, any necessary additions of lime and of
soda ash are made. The pressed lime carbonate is washed in the filter press and
it may after removal from the press, be compressed into bricks which may be dried
and burnt so as to convert the carbonate into caustic lime, which may then be used
in the manufacture of further quantities of caustic soda solution.
When the operations hereinbefore described as constituting my improvements
have been conducted with ordinary care, the whole of the chlorine in the bleaching
powder and the whole of the alkali are fully utilised, while the lime mud which is
at present a useless nuisance, is converted into a convenient and useful product, and
the pollution of streams and rivers thereby is prevented.
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 :-
The hereinbefore described process for utilising and obtaining useful products
from the bleaching powder dregs and lime mud of paper mills, substantially as set
forth.
Dated this 27th day of May A.D. 1891.
WILLIAM E. HEYS,
Agent for the Applicant.