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Патент USA US2129813

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Patented Sept. 13, 1938
Robert Roger Bottoms, Louisville, Ky., assignor
to The Girdler Corporation, Louisville, Ky., a
corporation of Delaware
No Drawing. Application February 25, 1935,
. Serial No. 8,059
7 Claims. (01. 23-421)
The present invention is a simple method of
sulphate'solution, which may be a solution from
obtaining anhydrous sodium sulphate directly
which the hydrocyanic acid has been recovered
from aqueous solutions of sodium sulphate, and
the main objects are to obtain the anhydrous
‘it salt in ?ne crystalline form, and to prevent the
caking and adhering of the salt on the walls of
in the treatment of coke oven gases or salt cake
from the manufacture of hydrochloric acid or a,
natural brine or extract, a salt of an alkali metal ’
or of magnesium which has a substantially
the vessel in which the solution is treated.
greater solubility in water than sodium sulphate.
Although the invention of the present appliAmong the preferred salts which may be uti
cation is broadly directed to the production of lized for this purpose are sodium thiocyanate,
l0 anhydrous sodium sulphate from aqueous solu- sodium, potassium or magnesium bromides or 10
tions of various concentrations and compositions, iodides, sodium or potassium thiosulphate, po
the invention Will be illustratively described in tassium or sodium formate, potassium thio
connection with the recovery of sodium sulphate _cyanate and other highly soluble salts of metals
from solutions which are produced in the re- which do not form a precipitate with sulphuric
l5 moval and recovery of hydrocyanic acid from acid, provided such salts have a greater solubility l5
coke oven gases.
in Water than sodium sulphate.
In the process of removing hydrocyanic gases
Of these com
pounds I prefer to use sodium thiosulphate or
from coke oven gases, or other gas mixtures containing the same, the gases are passed into con-
20 tact with, or into absorption relationship with,
sodium sulphide solutions.
sodium thiocyanate.
The sodium sulphate solution with such addi
tion may be evaporated and crystallized in ordi- 20
nary tubular evaporators and crystallizers With—
The hydrocyanic acid will be absorbed by the
sodium sulphide with the production of sodium
thiocyanate which may then be oxidized to pro25 duce hydrocyanic acid and sodium sulphate.
out di?iculty due to caking and encrusting of the
anhydrous sodium sulphate. The sodium sul
phate will crystallize from the boiling solution in
?ne, regular crystals which do not agg10merate_ 25
After the removal and the recovery of hydro-
- It has been found that only a small proportion
cyanic acid, the sodium sulphate will remain, and
it is necessary for the econom1cal performance of
the process that such sodium sulphate be re-
of such Mk9,“ metal or magnesium Salt is re
quj_red_ For examine, Such Sam need only be
added in amounts not exceeding 20% and not,
30 coveredso that it may be readily reconverted
mm sodium §u1ph1de' _
However’ 1r} récoverme this Sodlum sulphate
for reconversion into sodium sulphide, considerable difficulty has been experienced in evaporat-
less than 1% and preferably between about 5% 30
to 10% of the amount of sodium sulphate present.
The crystals resulting from a crystallization
of Sodium Sulphate from Solutions con-taming s0_
dium thiocyanate or other added Salts of mag_ 35
35 itfiit‘tl’ai?fplil?ft?etti tttyti?tlii‘ft?g aaaam
fltom the. mother hquor and Wished flree (if so‘
of the evaporators, which results in caking and
encrusting of such tubes with loss in efiiciency
mum thlocyana’te or other ad ed 53 ts with 2’
Small amount of ‘Hate?’
is among
the objects
of the
to Itprovide
a process
permit invention
the crystallization of anhydrous sodium sulphate while
@11131. 1S1
The process of producing anhydrous sodium
sulphate from a boiling water solution and in a
form which does not crystallize on or cling to the 45
equipment employed, said process including con
{to and
rapid breakdown of such mechanical ‘equipment,
concentrating a boiling aqueous solution conhe. Ul
alkali aaaaala may aaaa ha aaaaaaaaa
salt tends to deposit upon and stick to the tubes
taining the same, with elimination of any tend-
as new
desire to my
by Letters
ency to cause encrusting or caking on the tubes
centrating the solution by boiling to a point be
of the evaporators which may be employed for
yond which the sodium sulphate begins to be crys
this purpose, and without the need of cooling the . tallized out of solution and adding to said solution,
0 solution or of adding excessive amounts of any before or during the boiling, a compound selected 50
foreign material.
Other objects will appear during the course of
the following speci?cation.
In accomplishing these objects it has been
55 found most satisfactory to add to the Sodium
from the group consisting of sodium thiocyanate,
sodium thiosulphate, sodium formate, potassium
thiocyanate, potassium thiosulphate, potassium
formate, sodium bromide, sodium iodide, potassi
um bromide, potassium iodide, magnesium bro- 55
mide, magnesium iodide, and in an amount be
tween 1% and 20% of the sodium sulphate.
2. The process of
5. The
3. The process of producing anhydrous sodium
the boiling.
4. The process of producing anhydrous sodium
sulphate from a boiling Water solution and in a
or during the boiling.
or during the boiling.
7. The process of producing anhydrous sodium
sulphate from a boiling water solution and in a
or during the boiling.
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