U.S. patent application number 11/931602 was filed with the patent office on 2008-05-08 for methods for cleaning industrial equipment with pre-treatment.
This patent application is currently assigned to ECOLAB INC.. Invention is credited to Peter J. Fernholz, Brandon L. Herdt.
Application Number | 20080105279 11/931602 |
Document ID | / |
Family ID | 35207516 |
Filed Date | 2008-05-08 |
United States Patent
Application |
20080105279 |
Kind Code |
A1 |
Herdt; Brandon L. ; et
al. |
May 8, 2008 |
METHODS FOR CLEANING INDUSTRIAL EQUIPMENT WITH PRE-TREATMENT
Abstract
A method of cleaning equipment such as heat exchangers,
evaporators, tanks and other industrial equipment using
clean-in-place procedures and a pre-treatment solution prior to the
conventional CIP cleaning process. The pre-treatment step improves
the degree of softening of the soil, and thus facilitates its
removal. The pre-treatment solution can be a strong acidic
solution, a strong alkaline solution, or comprise a penetrant. A
preferred strong acidic solution is an acid peroxide solution. In
some embodiments, the pre-treatment may include no strong alkali or
acid ingredient; rather, the penetrant provides acceptable levels
of pre-treatment.
Inventors: |
Herdt; Brandon L.;
(Hastings, MN) ; Fernholz; Peter J.; (Burnsville,
MN) |
Correspondence
Address: |
ECOLAB INC.
MAIL STOP ESC-F7, 655 LONE OAK DRIVE
EAGAN
MN
55121
US
|
Assignee: |
ECOLAB INC.
St. Paul
MN
|
Family ID: |
35207516 |
Appl. No.: |
11/931602 |
Filed: |
October 31, 2007 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10928774 |
Aug 27, 2004 |
|
|
|
11931602 |
Oct 31, 2007 |
|
|
|
Current U.S.
Class: |
134/22.13 |
Current CPC
Class: |
A01J 7/022 20130101;
C11D 3/2075 20130101; C11D 3/044 20130101; C11D 3/042 20130101;
B08B 9/027 20130101; A01J 25/126 20130101; C11D 11/0041
20130101 |
Class at
Publication: |
134/022.13 |
International
Class: |
B08B 9/027 20060101
B08B009/027 |
Claims
1. A method of cleaning soils from industrial equipment using a CIP
process, the method comprising: (a) applying a pre-treatment
solution to the soil, the solution comprising at least 0.25 wt-%
active ingredients, the active ingredients including any of an
alkaline source, an acidic source, a penetrant, an oxidizer, and a
builder; (b) recirculating a first CIP solution through the
equipment after the pre-treatment solution, the CIP solution
comprising a dilute detergent; and then (c) rinsing the
equipment.
2.-22. (canceled)
Description
FIELD
[0001] The invention relates to cleaning of industrial equipment
such as evaporators, heat exchanger and other such equipment that
is conventionally cleaned using a CIP (clean-in-place) process.
BACKGROUND
[0002] In many industrial applications, such as the manufacture of
foods and beverages, hard surfaces commonly become contaminated
with carbohydrate, proteinaceous, hardness soils and other soils.
Such soils can arise from the manufacture of both liquid and solid
foodstuffs. Carbohydrate soils, such as cellulosics,
monosaccharides, disaccharides, oligosaccharides, starches, gums
and other complex materials, when dried, can form tough, hard to
remove soils, particularly when combined with other soil components
such as proteins, enzymes, fats, oils and others. The removal of
such carbohydrate soils can be a significant problem. Similarly,
other materials such as proteins, enzymes, fats and oils can also
form hard to remove soil and residues.
[0003] Clean-in-place cleaning techniques are a specific cleaning
regimen adapted for removing soils from the internal components of
tanks, lines, pumps and other process equipment used for processing
typically liquid product streams such as beverages, milk, juices,
etc. Clean-in-place cleaning involves passing cleaning solutions
through the system without dismantling any system components. The
minimum clean-in-place technique involves passing the cleaning
solution through the equipment and then resuming normal processing.
Any product contaminated by cleaner residue can be discarded. Often
clean-in-place methods involve a first rinse, the application of
the cleaning solutions, a second rinse with potable water followed
by resumed operations. The process can also include any other
contacting step in which a rinse, acidic or basic functional fluid,
solvent or other cleaning component such as hot water, cold water,
etc. can be contacted with the equipment at any step during the
process. Often the final potable water rinse is skipped in order to
prevent contamination of the equipment with bacteria following the
cleaning sanitizing step.
[0004] Clean-in-place processing requires a complete shutdown of
the equipment being cleaned, which results in lost production time.
Many times, the equipment is not thoroughly cleaned, due to the
large downtime needed. What is needed is an improved method for
cleaning this equipment, using the clean-in-place process, which
uses less time to thoroughly remove the soils.
SUMMARY OF THE DISCLOSURE
[0005] The invention relates to methods of cleaning equipment such
as heat exchangers, evaporators, tanks and other industrial
equipment using clean-in-place procedures. The method is suitable
for organic soil removal or, more particularly, for food soil
removal. Further, the method relates to cleaning processes for
removing carbohydrate and proteinaceous soils from beverage
manufacturing locations using a clean-in-place method. The method
includes using a pre-treatment or pre-treating step prior to the
conventional cleaning process.
[0006] In one aspect, the invention is directed to a method that
includes pre-treating the soiled surfaces with a strong acidic
solution. A conventional clean-in-place process follows this
pre-treatment step. A preferred strong acidic solution is an acid
peroxide solution. It has been found that a conventional
clean-in-place process using an alkaline detergent after the strong
acidic pre-treatment step provides particularly effective results.
The concentration of the active ingredients in an acidic
pre-treatment solution is at least 0.3% and usually at least
0.6%.
[0007] In another aspect, the invention is directed to a method
that includes pre-treating the soiled surfaces with a strong
alkaline solution. A conventional clean-in-place process follows
this pre-treatment step. It has been found that a conventional
clean-in-place process using an acidic detergent after the strong
alkaline pre-treatment step provides particularly effective
results.
[0008] Either of the pre-treatments, either acidic or alkaline, may
include a penetrant. The addition of a penetrant improves the
degree of softening of the soil, and thus facilitates the removal
of the soil. The concentration of acid plus peroxide in a
pre-treatment solution is at least 0.5% and usually at least 0.7%.
A concentration of about 1% is typical.
[0009] In another aspect, the invention is directed to a method
that includes pre-treating the soiled surfaces with a penetrant,
without the presence of appreciable amounts of acid or alkaline. A
conventional clean-in-place process follows this penetrant
pre-treatment step. The concentration of penetrant in the
pre-treatment solution is at least 0.25% and usually is at least
0.5%. In one particular embodiment, the penetrant pre-treatment
solution comprises approximately 0.9% of a blend of glycol ether
solvents; other levels of glycol ethers as penetrants are
suitable.
[0010] In one particular embodiment, the invention is to a method
of cleaning soils from industrial equipment using a CIP process.
The method includes applying a pre-treatment solution to the soil,
the solution comprising at least 0.25 wt-% active ingredients, with
the active ingredients including any of an alkaline source, an
acidic source, a penetrant, an oxidizer, and a builder. The method
also includes recirculating a first CIP solution through the
equipment after the pre-treatment solution, the CIP solution
comprising a dilute detergent and then rinsing the equipment. The
pre-treatment solution can have 0.25 to 1.5 wt-% acid and 0.01 to 1
wt-% oxidant, such as a peroxide. A penetrant, such as glycol
ether, may be present at 0.4 to 10 wt-%.
[0011] In another particular embodiment, the method includes
pre-treating the soil with a pre-treatment solution comprising at
least 0.5 wt-% active ingredients, the active ingredients including
any of an alkaline source, an acidic source, a penetrant, an
oxidizer, a surfactant, and a builder, removing at least a portion
of the penetrated soil with a dilute detergent solution, and
rinsing the equipment. In some embodiments, the pre-treatment
solution includes an alkaline source and the dilute detergent
includes an acid. In other embodiments, the pre-treatment solution
includes an acid source and the dilute detergent is basic.
[0012] The present invention includes using two different CIP
solutions.
[0013] Additional details regarding pre-treatment solutions and
methods of using pre-treatment solutions are provided below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a schematic diagram of an industrial process that
includes equipment to be cleaned, CIP process equipment, and
pre-treatment equipment.
DETAILED DESCRIPTION OF THE INVENTION
[0015] The present invention is directed to cleaning of industrial
equipment using a pre-treatment step in combination with
clean-in-place procedures. Use of a pre-treatment step, in
combination with conventional clean-in-place solutions and
processes, provides increased soil removal than the conventional
process alone. Additionally, use of a pre-treatment step, followed
by a water rinse, provided unexpected amounts of soil removal. Use
of a pre-treatment step allows the use of traditionally
incompatible chemistries.
[0016] As used herein, "weight percent", "wt-%", "percent by
weight", "% by weight", and variations thereof refer to the
concentration of a substance as the weight of that substance
divided by the total weight of the composition and multiplied by
100. It is understood that, as used here, "percent", "%", and the
like are intended to be synonymous with "weight percent", "wt-%",
etc.
[0017] As used herein, the term "about" refers to variation in the
numerical quantity that can occur, for example, through typical
measuring and liquid handling procedures used for making
concentrates or use solutions in the real world; through
inadvertent error in these procedures; through differences in the
manufacture, source, or purity of the ingredients used to make the
compositions or carry out the methods; and the like. The term
"about" also encompasses amounts that differ due to different
equilibrium conditions for a composition resulting from a
particular initial mixture. Whether or not modified by the term
"about", the claims include equivalents to the quantities.
[0018] It should be noted that, as used in this specification and
the appended claims, the singular forms "a," "an" and "the" include
plural referents unless the content clearly dictates otherwise.
Thus, for example, reference to a composition containing "a
compound" includes having two or more compounds. It should also be
noted that the term "or" is generally employed in its sense
including "and/or" unless the content clearly dictates
otherwise.
[0019] The method of the present invention applies to equipment
generally cleaned using clean-in-place (i.e., CIP) cleaning
procedures. Examples of such equipment include evaporators, heat
exchangers (including tube-in-tube exchangers and plate-in-frame
exchangers), heating coils (Including steam, flame or heat transfer
fluid heated) re-crystallizers, pan crystallizers, spray dryers,
drum dryers, and tanks. This method can be used in generally any
application where caked on soil or burned on soil, such as proteins
or carbohydrates, needs to be removed; applications include the
food industry (especially dairy), brewing, oil processing,
industrial agriculture and ethanol processing.
[0020] CIP processing is generally well-known. The process includes
applying a dilute solution (typically about 0.5-3%) onto the
surface to be cleaned. The solution cascades across the surface
(typically drains down), slowly removing the soil. Either new
solution is re-applied to the surface, or the same solution is
recirculated and re-applied to the surface.
[0021] A typical CIP process to remove a soil (including organic,
inorganic or a mixture of the two components) includes at least
three steps: an alkaline solution rinse, an acid solution rinse,
and then a water wash. The alkaline solution softens the soils and
removes the organic alkaline soluble soils. The subsequent acid
solution removes mineral soils left behind by the alkaline cleaning
step. The strength of the alkaline and acid solutions and the
duration of the cleaning steps are typically dependent on the
durability of the soil. The water rinse removes any residual
solution and soils, and cleans the surface prior to the equipment
being returned on-line. The present invention provides a
pre-treatment step, prior to the CIP process, which penetrates into
the soil. The penetrating materials soften the soil, act as a
catalyst, or otherwise enhance the activity of the conventional CIP
solution when it contacts the soil. Thus, the pre-treatment
facilitates the soil removal.
[0022] Referring now to FIG. 1, a schematic diagram of process
equipment is illustrated at reference numeral 10. Process 10
includes a tank 20, which is the equipment to be cleaned. A feed
line 25 supplies the various cleaning solutions to tank 20, and a
drain line 27 removes solution from tank 20. Operably connected via
appropriate pipes, valves, pumps, etc. is equipment for a CIP
process, designated as reference numeral 30. CIP process 30
includes a tank 35 for retaining the dilute CIP chemistry. Drain
line 27 from tank 20 is used to recirculate solution from tank 20
back to CIP process 30 and tank 35. Process 10 also includes
equipment for the pre-treatment process, designated as reference
numeral 40. Pre-treatment equipment 40 includes a first tank 42 and
a second tank 44. When two tanks are used, generally one tank,
e.g., tank 42, will contain an alkaline pre-treatment and the other
tank, e.g., tank 44, will contain an acidic pre-treatment. The
appropriate pipes, valves, pumps, etc. are in place for operably
connecting tanks 42, 44 with feed line 25 into tank 20. This set-up
of process 10 allows a pre-treatment to be applied to tank 20
without the use of large amounts of additional equipment, such as
piping. Additional details regarding the method of cleaning tank 20
is described below.
[0023] The Pre-Treatment Solution
[0024] As described above, the pre-treatment solution or
pre-treatment step is applied to the soil prior to the application
of conventional CIP chemistries. The chemistry of the pre-treatment
solution is selected to facilitate removal of the soils on the
surfaces to be cleaned. The pre-treatment solution pre-coats and
penetrates into the soil, softening the soil. The specific
chemistry used can be selected based on the soil to be removed. The
chemistry used can be compatible with the CIP chemistry. In some
embodiments, it is desired to have a pre-treatment that is
incompatible with the CIP chemistry; in such instances, the
pre-treatment reacts with the CIP chemistry. It has been found that
using incompatible chemistries further increases the soil-removal
effectiveness.
[0025] The pre-treatment solution comprises at least 0.25% of
active ingredients, typically at least 0.5%, preferably at least 2%
and more preferably at least 4%. By use of the term "active
ingredients" what is intended is the non-inert ingredients that
facilitate the softening, dissolving and removal of soil. These
active ingredients include any alkaline/base, acid, penetrant
(including surfactant), builder, oxidizer, catalyst and chelant or
chelating agent. In most embodiments, water is the remainder of the
solution. Typically, the solution has no more than about 15% active
ingredients, preferably no more than about 10%. For most
applications, a concentration of about 1-10% is preferred; a
concentration of about 2-5% is suitable for most applications.
[0026] Alkaline or Acidic Ingredients
[0027] The pre-treatment solution optionally and preferably
includes alkaline or acidic ingredients. Examples of suitable
alkaline sources include basic salts, amines, morpholine,
carbonates and silicates. Particularly preferred alkaline sources
include NaOH (sodium hydroxide), KOH (potassium hydroxide), TEA
(triethanol amine), DEA (diethanol amine), and MEA (monoethanol
amine), sodium metasilicate and potassium silicate.
[0028] Examples of suitable acidic sources include mineral acids
(such as phosphoric acid, nitric acid, sulfuric acid), and organic
acids (such as lactic acid, acetic acid, hydroxyacetic acid, citric
acid, glutamic acid, glutaric acid).
[0029] The amount of alkaline or acid in the pre-treatment solution
is typically at least 0.25 wt-% and no greater than 10 wt-%. Common
levels of alkaline or acid include 2 to 5 wt-% and 0.5 to 1.5
wt-%.
[0030] Penetrants
[0031] A penetrant may be present in the pre-treatment solution.
The penetrant may be combined with an alkaline or acid source in
the solution, or, the penetrant may be used without an alkaline or
acid source. Preferably, the penetrant is water soluble.
[0032] Examples of suitable penetrants include alcohols, short
chain ethoxylated alcohols and phenol (having 1-6 ethoxylate
groups). Organic solvents are also suitable penetrants. Examples of
suitable organic solvents, for use as a penetrant, include esters,
ethers, ketones, amines, and nitrated and chlorinated
hydrocarbons.
[0033] Another preferred class of penetrants is ethoxylated
alcohols. Examples of ethoxylated alcohols include alky, aryl, and
alkylaryl alkloxylates. These alkloxylates can be further modified
by capping with chlorine-, bromine-, benzyl-, methyl-, ethyl-,
propyl-, butyl- and alkyl-. A preferred level of ethoxylated
alcohols in the solution is 1 to 20 wt-%.
[0034] Another class of preferred solvents for use as penetrants is
glycol ethers, which are water soluble. Examples of glycol ethers
include dipropylene glycol methyl ether (available under the trade
designation DOWANOL DPM from Dow Chemical Co.), diethylene glycol
methyl ether (available under the trade designation DOWANOL DM from
Dow Chemical Co.), and propylene glycol methyl ether (available
under the trade designation DOWANOL PM from Dow Chemical Co.). A
preferred level of glycol ether in the solution is 0.5 to 20
wt-%.
[0035] Surfactants also are a suitable penetrant for use in the
pre-treatment solution. Examples of suitable surfactants include
nonionic, cationic, and anionic surfactants. Nonionic surfactants
are preferred. Nonionic surfactants improve soil removal and can
reduce the contact angle of the solution on the surface being
treated. Examples of suitable nonionic surfactants include alkyl-,
aryl-, and arylalkyl-, alkoxylates, alkylpolyglycosides and their
derivatives, amines and their derivatives, and amides and their
derivatives. Additional useful nonionic surfactants include those
having a polyalkylene oxide polymer as a portion of the surfactant
molecule. Such nonionic surfactants include, for example,
chlorine-, benzyl-, methyl-, ethyl-, propyl-, butyl- and other like
alkyl-capped polyoxyethylene and/or polyoxypropylene glycol ethers
of fatty alcohols; polyalkylene oxide free nonionics such as alkyl
polyglycosides; sorbitan and sucrose esters and their ethoxylates;
alkoxylated ethylene diamine; carboxylic acid esters such as
glycerol esters, polyoxyethylene esters, ethoxylated and glycol
esters of fatty acids, and the like; carboxylic amides such as
diethanolamine condensates, monoalkanolamine condensates,
polyoxyethylene fatty acid amides, and the like; and ethoxylated
amines and ether amines and other like nonionic compounds. Silicone
surfactants can also be used.
[0036] Additional suitable nonionic surfactants having a
polyalkylene oxide polymer portion include nonionic surfactants of
C6-C24 alcohol ethoxylates having 1 to about 20 ethylene oxide
groups; C6-C24 alkylphenol ethoxylates having 1 to about 100
ethylene oxide groups; C6-C24 alkylpolyglycosides having 1 to about
20 glycoside groups; C6-C24 fatty acid ester ethoxylates,
propoxylates or glycerides; and C4-C24 mono or dialkanolamides.
[0037] If a surfactant is used as a penetrant, the amount of
surfactant in the pre-treatment solution is typically at least
0.25% and no greater than 10 wt-%. Common levels of surfactant
include 0.4 to 8 wt-%, and 1 to 4 wt-%.
[0038] Overall, when an alkaline or acid source is present, the
amount of penetrant in the pre-treatment solution is typically at
least 0.2 wt-% and no greater than 2.5 wt-%. Common levels of
penetrant, when an alkaline or acid source is present, include
0.4-2 wt-%; 1-2 wt-% is preferred. The amount of penetrant, in
relation to any alkaline or acid source when present, is generally
1:1 to 1:5.
[0039] For pre-treatment solutions without an alkaline or acid
source, the amount of penetrant in the solution is at least 0.05
wt-% and no greater than 50%. Typically, the level is 0.1 to 25
wt-%. Common levels of penetrant include 0.5 to 10 wt-%, and 1 to 5
wt-%.
[0040] Oxidizers
[0041] Acidic solutions may include an oxidizing agent or an
oxidizer, such as a peroxide or peroxyacid. The resulting solution
is very effective against protein soils. Further, reaction of these
oxygen compounds with the soil, especially when combined with an
alkaline source, creates vigorous mechanical action on and within
the soil, which enhances removal of the soil beyond that caused by
the chemical action.
[0042] Suitable ingredients are oxidants such as chlorites,
bromine, bromates, bromine monochloride, iodine, iodine
monochloride, iodates, permanganates, nitrates, borates,
perborates, and gaseous oxidants such as ozone, oxygen, chlorine
dioxide, chlorine, sulfur dioxide. Peroxygen compounds, which
include peroxides and various percarboxylic acids, including
percarbonates, are suitable. Typical peroxygen compounds include
hydrogen peroxide (H.sub.2O.sub.2), peracetic acid, a persulphate,
or a percarbonate.
[0043] The amount of oxidant in the pre-treatment solution is
typically at least 0.01 wt-% and no greater than 1 wt-%. Common
levels of oxidant are 0.01 to 0.25 wt-%; 0.05 wt-% is a
particularly suitable and common level. Suitable levels of oxidant,
in relation to any acid source, are generally 2:1 to 1:2000. Common
levels are 1:2 to 1:100, more common 1:20 to 1:50. Solutions of
0.25 wt-% to 10 wt-% phosphoric acid with 50-5000 ppm (0.005 wt-%
to 0.5 wt-%) hydrogen peroxide are particularly suitable. An
example pre-treatment solution includes 0.75 wt-% phosphoric acid
and 500 ppm (0.05 wt-%) hydrogen peroxide, which is a 1:15 ratio of
oxidant:acid.
[0044] Builders
[0045] The pre-treatment solution preferably includes a builder.
Builders include chelating agents (chelators), sequestering agents
(sequestrants), detergent builders, and the like. The builder often
stabilizes the composition or solution. Examples of builders
include phosphonic acids and phosphonates, phosphates,
aminocarboxylates and their derivatives, pyrophosphates,
polyphosphates, ethylenediamene and ethylenetriamene derivatives,
hydroxyacids, and mono-, di-, and tri-carboxylates and their
corresponding acids. Other builders include aluminosilicates,
nitroloacetates and their derivatives, and mixtures thereof. Still
other builders include aminocarboxylates, including salts of
ethylenediaminetetraacetic acid (EDTA),
hydroxyethylenediaminetetraacetic acid (HEDTA), and
diethylenetriaminepentaacetic acid. Preferred builders are water
soluble.
[0046] Particularly preferred builders include EDTA (including
tetra sodium EDTA), TKPP (tripotassium polyphosphate), PAA
(polyacrylic acid) and its salts, phosphonobutane carboxylic acid,
and sodium gluconate.
[0047] The amount of builder in the pre-treatment solution, if
present, is typically at least 0.25 wt-% and no greater than 5
wt-%. Common levels of builder include 0.5 to 1.0 wt-% and 1 wt-%
to 2.5 wt-%.
[0048] Methods of Pre-Treating
[0049] The method of the present invention is directed to applying
the pre-treatment solution to the surface to be cleaned, prior to a
conventional CIP process. The resulting CIP process requires less
steps and/or less time for each step. For example, a conventional
CIP process includes five steps after an initial water rinse: a
conventional alkaline (NaOH) wash to remove soil, an interim rinse,
a conventional acid wash to remove minerals and scale, a water
rinse, and a conventional sanitizing step. This process can be
replaced with a three-step process after the initial water rinse:
an acidic pre-treatment step, a conventional alkaline wash, and a
water rinse. Alternately, the three-step process can be: an
alkaline pre-treatment step, a conventional acidic wash, and a
water rinse. By using such a process, an interim rinse is not
needed, as the reaction between the acid and base in separate steps
is desired.
[0050] By using either of the two pre-treatment processes described
immediately above, the amount of water used in the overall cleaning
process with pre-treatment is reduced by about 30% compared to the
conventional five-step process. The amount of time for the overall
process with pre-treatment is reduced by about 30% compared to the
conventional five-step process. The specific number of steps, the
water usage, or the processing time reduced will depend on the
concentration and chemistry of the pre-treatment solution.
[0051] Referring again to FIG. 1, pre-treatment solution is stored
at the equipment designated as 40. In this process 10, tank 42
holds an alkaline pre-treatment solution and tank 44 holds an
acidic pre-treatment solution that includes peroxide.
[0052] To clean 20, tank 20 and its connection lines are drained of
any product that may be present. A water rinse may be included to
remove any residual product. In one embodiment, alkaline
pre-treatment solution from tank 42 is pumped via piping and feed
line 25 into tank 20. Conventional CIP application equipment, such
as a spray head, applies the pre-treatment solution onto the
interior surface of tank 20. The pre-treatment solution cascades or
otherwise flows down the surface of tank 20, softening the soil. A
second application of pre-treatment solution may be applied,
although this is not generally needed.
[0053] After application and draining of the pre-treatment
solution, a conventional CIP process, using the detergent from
process 30 and tank 35, is performed. The CIP detergent may be
acidic or alkaline. Detergent from tank 35 is recirculated through
tank 20 via feed line 25, return line 27, and other appropriate
piping.
[0054] In another embodiment, a pre-treatment solution containing
hydrogen peroxide from tank 44 is pumped via piping and feed line
25 into tank 20. After application and draining of the peroxide
pre-treatment solution, a conventional CIP process, using an
alkaline detergent such as sodium hydroxide, from process 30 and
tank 35, is performed. The sodium hydroxide activates any residual
peroxide on the walls of tank 20.
[0055] Various generic examples of suitable pre-treatment steps are
provided below.
[0056] In one particular example, an alkaline pre-treatment
solution of 10 wt-% NaOH is sprayed onto the interior surfaces of a
holding tank and allowed to drain. After about 20 minutes, the CIP
process, having a 1% acidic solution, is initiated.
[0057] In a second particular example, an acidic pre-treatment
solution of 1 wt-% phosphoric acid is circulated onto the interior
surfaces of a plate-in-frame heat exchanger. The solution includes
0.1 wt-% H.sub.2O.sub.2. The acid, together with the peroxide,
provides an effervescence effect, providing mechanical action to
help soften and remove the soil. The peroxide is also catalytically
activated by a subsequent conventional alkaline CIP solution which
causes further effervescence and soil removal.
[0058] In a third particular example, an acidic pre-treatment
solution, having about 1.0 wt-% mineral acids and 1.0 wt-% solvent
penetrant, is circulated onto the heat exchanging surfaces of an
evaporator and drained from the surface. After about 20 minutes,
the CIP process is initiated. A conventional alkaline wash, approx.
0.5 wt-% active NaOH, is fed into the evaporator. The alkaline
reacts with any acidic residue, generating heat and mechanical
action furthering the removal of the soil.
EXAMPLES
Example 1
Test Procedure
[0059] Solid milk pellets were prepared by mixing 3 grams of dry
milk power and 3 grams of soil. The resulting mix was pressed in a
die for 30 seconds at 10,000 lb, and then more pressure was added
to again apply 10,000 lb for 30 additional seconds. The pellets
were placed in screens and immersed in the pre-treatment solutions,
described below, for 5 minutes, removed, and then drained for 5
minutes. The screen and dried pellets were placed in a beaker of
0.5 wt-% NaOH at 120.degree. F. (The test designated as "None" had
no pre-treatment step; the test designated as "None *" had no
pre-treatment step and used a 3.0% NaOH cleaning at 120.degree. F.,
rather than the 0.5% NaOH). The beakers were placed on a hot plate
set to 49.degree. C. (approx. 120.degree. F.) with large stir bars
rotating at 350 rpm. After 30 minutes, the screen and pellets were
removed from the cleaning solution and gently immersed in and
removed from deionized water five times, and then dried overnight
in a 50.degree. C. oven. The results of the testing are below.
Pre-Treatment 1
[0060] A 10 wt-% solution of active NaOH was prepared and used as a
pre-treatment. The pre-treatment had 100,000 ppm sodium hydroxide
(an alkaline cleaner).
Pre-Treatment 2
[0061] A pre-treatment solution was prepared having 1360 ppm tetra
sodium EDTA (a builder and/or chelant), 3000 ppm sodium gluconate
(a builder and/or chelant), 2400 ppm potassium silicate (an
alkaline cleaner), 7000 ppm alkyl polyglycoside (a surfactant), and
4200 ppm potassium hydroxide (an alkaline cleaner). This
Pre-Treatment 2 had 3.66% alkaline, 0.43% builder/chelant, and 0.7%
surfactant, providing 4.79% active ingredients.
Pre-Treatment 3
[0062] A pre-treatment solution was prepared having 41550 ppm
polycarboxylated alcohol ethoxylate (a surfactant), 9540 ppm octyl
amine oxide (a surfactant), 25500 ppm alkyl polyglycoside (a
surfactant), and 4150 ppm 2-ethylhexanol ethoxylate (a penetrant).
This Pre-Treatment 3 had 0.4% penetrant and 7.6% surfactant,
providing 8% active ingredients.
Pre-Treatment 4
[0063] A pre-treatment solution was prepared having 1600 pm
potassium hydroxide (an alkaline cleaner), 9465 ppm sodium
hydroxide (an alkaline cleaner), 18500 ppm polyacrylic acid (a
builder and/or chelant), and 4625 ppm phosphonobutane tricarboxylic
acid (a builder and/or chelant). This Pre-Treatment 4 had 1.10%
alkaline and 2.3% builder/chelant, providing 2.9% active
ingredients. TABLE-US-00001 screen + pellet screen + pellet wt, wt,
pellet wt pellet wt Pre-Treatment Screen wt before clean after
clean before after clean % wt loss of solution (g) (g) (g) clean
(g) (g) pellet 1 18.23 23.93 22.59 5.70 4.36 23.51% 1 18.20 23.86
22.52 5.66 4.32 23.67% 2 18.23 23.91 22.54 5.68 4.31 24.12% 2 18.02
23.34 22.08 5.32 4.06 23.68% 3 19.24 24.70 22.14 5.46 2.90 46.89% 3
18.06 23.67 21.19 5.61 3.13 44.21% 4 17.95 23.50 20.09 5.55 2.14
61.44% 4 18.22 23.90 21.69 5.68 3.47 38.91% None 19.16 24.81 23.22
5.65 4.06 28.14% None 13.47 18.76 17.22 5.29 3.75 29.11% None*
19.27 25.01 24.14 5.74 4.87 15.16% None* 18.15 23.82 23.02 5.67
4.87 14.11%
[0064] The results show both consistency within the cleaning
processes and differences when comparing the methods. The results
indicate that lower levels of NaOH are better than higher levels,
and that pre-treatment solutions 3 and 4 are superior to
pre-treatment solutions 1 and 2. This difference, however, may be
due to the test procedure used. Tests 1 and 2 were done on one hot
plate whereas tests 3 and 4 were done on a second hot plate. It is
possible that these two hot plates were not equal at maintaining
the 120.degree. F. temperature.
[0065] A drastic difference was seen between the duplicate tests
(i.e., 61% and 39% for solution 4); it is possible that one of the
pellets had a crack in it, providing a weak location for the pellet
to break. The high exposed surface area would result in an increase
rate if disintegration.
[0066] The tests were rerun on the same hotplate in an attempt to
determine if there was any inconsistency between temperature
control of the hotplates. The results are provided in the table
below, under the column designated "% wt loss of pellet with
pre-treat".
[0067] As an alternative, and comparative method, 1 gram of the
Pre-treatment solution were added to 315 grams of the 0.5% NaOH
cleaning solution. Thus, rather than applying the pre-treatment
chemistry as a separate step, the pre-treatment chemistry was added
to the cleaning solution. The results are provided in the table
below, under the column designated "% wt loss of pellet without
pre-treat". TABLE-US-00002 % wt loss of pellet % wt loss of pellet
Pre-treatment with pre-treat without pre-treat 1 22.16% 36.92% 2
23.90% 37.39% 3 41.96% 34.01% 4 50.17% 31.95%
[0068] The results indicate that eliminating the separate
pre-treatment step and adding the chemicals directly to the
cleaning solution increased the performance of the two less
effective solutions (1-10% NaOH; 2-10% KX-3108) and decreased the
performance of the two more effective solutions (3-10% Quadexx 400;
4-10% Quadexx 500). All of these results were better than if no
pre-treatment was present (which provided pellet loss of about
29%).
Example 2
Test Procedure
[0069] Soiled stainless steel test panels, having soil on one side,
were prepared by drying a mixture of mashed corn solids onto one
side of the panel in an oven at 120.degree. C. for 4 hours. The
soiled panels were then cleaned as described below.
[0070] For Test (I), with the pre-treatment step, 800 grams of
Pre-Treatment solution 5 were placed in a 1000 ml beaker. It had
been determined that approximately 1 gram of the pre-treatment
solution contacted and remained on the soiled panel. After a brief
dip in the pre-treatment, the panels were hung for 5 minutes in
ambient conditions. The dried panels were then placed in a 1000 ml
beaker which had 750 g of 40.degree. C. water with the soil side
down. After 30 minutes, the panels were gently immersed in and
removed from deionized water five times, and the panels were then
dried. The results of the testing are below.
[0071] For Test (II), the test panels were not pre-treated, but
were cleaned in 750 g of 40.degree. C. water with 1 g Pre-Treatment
5 added to the water.
[0072] For Test (III) the test panels were not pre-treated, but
were cleaned in 750 g of 40.degree. C. water.
Pre-Treatment 5
[0073] A pre-treatment solution was prepared having 400 ppm tetra
sodium EDTA (a builder and/or chelant), 4500 ppm tri potassium
polyphosphate (a builder and/or chelant), 3852 ppm potassium
hydroxide (an alkaline cleaner), 3000 ppm polyethylene phenol ether
phosphate (a surfactant), 1000 ppm sodium metasilicate (an alkaline
cleaner), 9000 ppm ethylene glycol monobutyl ether (a penetrant),
and 2400 ppm sodium xylene sulfonate (a surfactant). This
Pre-Treatment 5 had 0.5% alkaline, 0.5% builder/chelant, 0.5%
surfactant, and 0.9% penetrant, providing 2.4% active ingredients.
TABLE-US-00003 Test Method average % soil removed I 99.12% (average
of three tests) II 14.14% (average of three tests) III 14.12%
(average of two tests)
[0074] The results above show that merely adding the pre-treatment
chemistry to the wash solution, does not improve the soil removal
from the test panels. Rather, separated and step-wise application
of the pre-treatment solution and the wash solution provides
improved soil removal.
[0075] The invention has been described with reference to various
specific and preferred embodiments and techniques. However, it
should be understood that many variations and modifications may be
made while remaining within the spirit and scope of the
invention.
* * * * *