Note: Descriptions are shown in the official language in which they were submitted.
"` 1~L995Sal
This invention is directed to cleaning the interior of
the jacket of a glass-lined reactor, using a cleaner especially
formulated to remove scale and rust without, however, forming
hydrogen, which tends to diffuse through the reactor wall and
attack the glass lining inside the reactor.
Substantially any heating or cooling medium circulated
through the jacket of a jacketed glass-lined reactor will
gradually cause formation of rust and/or result in scale These
deposits interfere with heat transfer and require periodic
removal. For such purpose, acidic cleaners are probably the
worst, for the reason above given. Alkaline cleaners have
been used, but fail to remove hardness-type scale. Hydrosulfite
cleaners remove iron, but not hardness scale.
We largely avoid the disadvantages of prior art jacket
cleaning processes by the use of a special aqueous cleaner
comprising a chelant, a dispersant, a metal passivator, and
(optionally) an antifoaming agent.
Thus, a method is provided of cleaning the jacket of
a glass-lined reactor comprising circulating through the jacket
an aqueous cleaning solution comprising a mixture of water and
a cleaner concentrate comprising from 6.821 to 37.4775 weight
percent of a chelant, from 0.1 to 5.5 weight percent of a dis-
persant, and from 0.175 to 1.05 weight percent of a ferrous
metal passivator, and water to make lO0 weight percent.
The following example illustrates without limiting the
invention.
-2-
Si :~99~is~
Example 1
The jacket of a 1000 gallon glass-lined reactor had
become filled with scale which had reduced the water flow
and caused a reduction in heat transfer.
Due to the glass lining, acid cleaning of the reactor
jacket was impossible, because of the possibility of the
glass lining being damaged by gas pressure from the acid
reaction. In t-he past, these reactors have been
dismantled, sandblasted to remove the scale, and relined.
Such a relining requires from 14 to 16 weeks at a cost of
approximately 70~ of the original price of this reactor.
Therefore, a cleaning product that would effectively
remove scale and passivate the metal parts while at the
same time not damage the glass lining was required.
Our cleaner~concentrate~comprised: -
Wt. %
38% aqueous solution of ethylene diamine tetra
acetic acid (chelant and cleaner) 98.625
Polyglycol (antifoaming agent) .005
Sodium lignosulfonate (dispeesant) .16
Sodium polymethacrylate, 4500 mol. wt.
(dispersant) .55
Hydrazine, 35~ aqueous solution
~metal passivator) 66
100 . 000
The cleaniny procedure was as follows:
(1) Feed 5.5 gallons of cleaner with 50 gallons
of city water (Rochester, N. Y.) to the
reactor jacket.
(2) Circulate this solution at 120-150F for 4-8 hours.
~1~9SS(~
~3) Drain the reactor jacket an~i measure the specific
conductance of effluent against a standard of 305
micromhos for the city water in this example. (305
micromhos was the conductivity of the water before
the addition of the chemical.)
(4) Based on the conductivity reading, determine
whether sufficient cleaning has taken place or
whether an additional charge of chemical is
required. If the conductivi~y of the cleaning
solution has increased by at least SO~ after
recirculation, then suficient cleaning will have
taken place.
The following table shows the results of the chemical
cleaning. The first column shows the analysis of the
cleaning solution after chemical addition but before
recirculation. The second analysis is that of the
cleaning solution after 4 hours of recirculation. Note
the changes in the total dissolved solids, the hardness of
CaC03, the calcium content, and the iron content. The
total dissolved solids nearly doubled. The amount of
hardness increased by more than six times. The iron was
increased eight-fold. All these measurements show that
the scale that consisted largely of calcium and iron was
being dissolved by the cleanser.
~ ~ .
~ 9~5~
Water Analysis
Cleaner ~lu5 Cil:y ~qater
efore Circulation Af~er Circulation
Total dissolved
solids, ppm18,698 35,61û
p~I 11 . 9 12
Rardness as CaCO3 223 1,406
Specific conductance,
micromhos/cm 9,4~0 14,700
Calcium as Ca, ppm 76 546
Magnesium as Mg, ~prn 8 10
Iron a~ Fe, ppm 8.6 80
Silica as SiO2 1 1.1
--5--
9ss~
The c eaner used in the above example is available
*
commercially as Polymate 661 (a concentrate~ from the
Dearborn Chemical Division, Chemed Corporation. In a more
general sense, the following is suitableo
chelant 17.95 - 98.625 wt%
antifoaming agent O - 0005
dispersant .1 - 5.5
metal passivator .5 - 3.0
water~ to make 100~
The concentrate is suitably diluted with water in a
ratio of about 5.5 volumes of concentrate per 50 volumes
of waterO This makes the use solution. Within the range
given, more chelant is used, depending on the severity of
the scale.
Besides ethylene diamine tetra acetic acid, other well
known chelants can be used, e.g., trisodium nitrilotri-
acetate monohydrate.
Besides polyglycol, other well known antifoaminy
agents are s~itable, e.g., antifoams based on organic
esters~
Besides sodium lignosulfonate and/or sodium polymetha-
crylate, other well known dispersants are suitable, e.g.,
the nr~anophosphonates, hydroxy-ethylidene diphosphonic
acid and the like.
Besides hydrazine, other well-known metal passivators
are suitable, e.g., diethylhydroxylamine~
* Trademark
~`~ 6 -
