Note: Descriptions are shown in the official language in which they were submitted.
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6530-387
Canndian Patent 1 173 778 and its corresponding United States
Patent 4,425,191 deal with the utilization of intumescent chemical sealants
Eor preventing the escape of gases Erom such industrial devices as coke
ovens. Canadian Patent 1 173 778 describes the problem solved in the
following language;
"It is well known especially from Environmental Reports and
the news media that the sealing oE ovens which produce noxious fumes,
smoke, dust, etc., is a diEEicult art. Only recently the coke industry
in the major steel producing area oE the United States has been threatened
with a complete shutdown because oE its inability to comply with the new
Environmental Regulations of the Environmental Protection Agency of the
United States of America and the Department of Environmental ~esources of
the Commonwealth of Pennsylvania.
'An example of a coke oven which presently has sealing problems
is a coke oven with a so-called Koppers Door. The coke oven with the
Koppers Door utilizes an S-shaped seal for sealing the door against the
jamb of the oven. Because of irregularities in the jamb and seal, gases
from within the coke oven readily leak past the jamb. In cases where the
seal has been damaged by loading and unloading of coal and coke, gouges
occur therein, which greatly increase the flow of noxious gases and fumes
from the coke oven to the surrounding air. This leakage from damaged ovens
is especially undesirable since the degree of pollution caused thereby
is many fold than of an oven in preferred condition. However, during long
use coke ovens are damaged by the constant loading and unloading and seal
cleaning, therefore, a larger and larger percentage of the ovens leak at
ever increasing rates.
"Another door widely used in the coke industry is the Wilputte Door.
The Wilputte Door has a diaphragm seal and a jamb with an adjustable screw
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~or makLng contact more readily between the jamb and the door. The Wllputte
Door also suffers ~rom the same sort of problems that the Koppers Door does.
great need is also felt ~or an improved sealing arrangement therein.
"Recent tests have shown that many of these doors in present
operation in their present configurations do not permit operation within the
guidelines set by the Department of Enviromnental Resources and the
Environmental Protection Agency. The fact of the lack of capability of
meeting these requirements is well known and has threatened to shut down
the steel industry for lack oE coke. ThereEore, a great need is felt
for an improved door sealing arrangement which would permit operation
within the guidelines oE the Environmental Protection Agency of the
Department of Environmental Resources.
"There are a great number of other applications where leakage
from ovens and other heated chambers can be cured by use of my invention
such as soaking pits used for the soaking of iron ingots during the
manufacture of iron and steel, furnaces and other examples which are too
numerous to mention herein."
The prepared sealant used in Canadian 1 173 778 is sodium
silicate which at elevated temperatures intumesces. It is indicated that
the preferred sodium silicate is applied at a viscosity between 400 and
950 centipoise.
One of the problems encountered in using sodium silicates of
the type described above is that in cold weather they thicken or freeze,
whereby they become incapable of being easily applied as a coke oven
door sealant.
The present invention overcomes this difficulty by providing a
sodium silicate composition having improved properties which makes it
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usable as a cGke oven cloor sealant at low tempera~.lres.
Thus this invention provides a sealant composition for
coke, oven doors and the like whi~h comprise a sodium silicate
composi-tion containing:
Ingrelients ~_~y_weiqht
Soft Water 2 - 4%
Sodium Hydroxide 3 - 6%
Sodium Borate 1 - 4'~
X 4 - 8%
Sodium Silicate 80 ~ 90%
wherein X is a freezing point depressant chosen from the group
con~isting of alkali metal formates, stable inoryanic phosphates,
water-soluble hydroxy carboxylic acids, mannitol and methanol.
A preferred composition of the invention is a sodium
silicate-containing material having the formula:
Soft Water 3%
Sodium Borate 2%
Sodium Hydroxide 5%
Sodium Formate 5%
Sodium Silicate 85%.
A number of different sodium salts and known pour point
depressants were evaluated. Some of these materials proved satis-
factory while others were not. These results are presented below
using various inqredients in the formula below:
Soft Water 2 - 4%
Sodium Hydroxide 3 - 6%
Sodium Borate 1 - 4%
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66~30-387
X 4 -- 8%
Soclium Silica-te 80 - gor~.
In the following test the various compositions were
evaluatecl by uslng a technique that broaclly reproduces the
procedure used when these compositis~ns are used as coke oven door
sealants. The procedure used for a coke oven door involves
removiny the remaining sealant from the hot door edge areas after
opening, application of fresh sealant as a sprayed-on foam to the
~ cleanecl edge areas, followec1 by door closing. Thus the spray has
to give a goocl stable foam on a hot surface; the spray is obtalned
using a conventional compressed-air system. The test technique
used to evaluate these compositions was to apply them by spraying
to a steel panel (8" x 14" x ~") at a temperature of about 135C.
In addition to observing the foam properties, ease of removal on
cooling was also checked.
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TABI.E I
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Freeze Viscosity
X Stability Point C (mPa-s) Spr~ sults
Sodium chloride Stable -22 155 Good foam
Sodium formate Stable -18 135 Good foam
Sodium bromide Stable -17 153 Good ~oam
Urea Stable -12 120 Good foam
Sodium acetate Unstable
Sodium Benzoate Unstable
Sodium carbonateUnstable
Sodium sulphate Unstable
Tetrasodium
phosphate Unstable
Trisodium
phosphate Stable -12 llO Fair foam
Acetic acid Unstable
Citric acid Stable -5 170
Formic acid Unstable
Mannitol Stable -5 8~
Methanol Stable -7 55
Ethylene glycol Unstable
Propylene glycol Unstable
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In the above Eormulas :it should be noted that sodium brom:Lde
and urea are not preEerred since they tend to present problems of toxic
e:Efects. Also sodium chlor:ide should not be used in a preferred practice
of the invention due to its possible deteriorating e:Efects on coke oven
Eire bricks.
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