Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – For cleaning a specific substrate or removing a specific...
Reexamination Certificate
1998-09-01
2001-03-20
Gupta, Yogendra (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
For cleaning a specific substrate or removing a specific...
C510S219000, C510S223000, C510S225000, C510S231000, C510S233000, C510S234000, C510S477000, C510S480000, C510S510000, C510S534000, C510S252000, C510S272000, C510S531000, C134S010000, C134S022130, C134S022170, C134S022180
Reexamination Certificate
active
06204231
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a water-containing alkaline cleaning formulation containing potash lye for equipment used in the food industry.
The invention also relates to a process for cleaning equipment used in the food industry with an alkaline cleaning formulation which is regenerated by membrane filtration, the permeate being recycled.
It is known that equipment used in the food-processing industry, for example tanks, pipelines, bottling plants and the like, can be cleaned with alkaline cleaning solutions. These cleaning solutions or liquors essentially consist of a 2% soda lye containing added cleaning enhancers, for example defoamers and emulsifiers. In principle, potash lye could be used instead of soda lye because it produces the same cleaning result. However, soda lye is used for reasons of cost. Only where low outside temperatures prevail is potash lye added in small quantities to the soda lye in order to lower the crystallization point of the cleaning concentrate. However, the potash lye always makes up considerably less than 20% by weight of the hydroxide total.
The alkaline cleaning solutions often contain an addition of ethylenediamine tetraacetic acid (EDTA) in the form of its disodium salt because EDTA—as the only complexing agent in aqueous alkaline cleaning solutions—is capable of dissolving mineral soils, such as calcium and magnesium salts, for example in the form of limescale, milk scale, beer scale and the like.
In recent years, an integrated cleaning and disinfecting technique known as cleaning in place (CIP) has been successfully applied. The corresponding fully automatic cleaning systems clean all storage tanks and pipelines automatically after each production cycle. The cleaning formulation and cleaning process according to the invention are particularly suitable for use in the CIP process.
2. Discussion of Related Art
It is known that wastewater pollution by spent cleaning solutions can be reduced and the economy of the cleaning process improved by regenerating the spent cleaning solution in membrane filtration units. To this end, part of the cleaning solution is transferred from a collecting tank to a buffer tank and pump-circulated from there through a membrane system in which it undergoes crossflow filtration. One such regenerating process is known from WO 95/27681 A1. The permeate consisting of water and soda lye is returned to the collecting tank for the cleaning solution. The organic soils collect in the buffer tank of the membrane filtration unit and are periodically removed for disposal as waste. Since, in cases where EDTA-containing cleaning solutions are used, any introduction of EDTA into the wastewater should be avoided on account of the poor biodegradability of this compound and its ability to remobilize heavy metals in the environment, Israeli patent application IL 109 249 proposes recovering the EDTA from the concentrates collecting in the buffer tank by acidic precipitation. However, the addition of EDTA to the cleaning solutions affects the performance of the nanofiltration unit which is reflected in distinctly reduced flow. In addition, in the case of cleaning equipment for the dairy industry and in the case of EDTA-free cleaning solutions, it is known that the concentrate can be freed from the alkaline constituents by diafiltration and subsequently used as an animal feed or animal feed supplement. Diafiltration is necessary to reduce the sodium content of the concentrate which is too high for its use as an animal feed. Unfortunately, the large volume of wastewater accumulating in the diafiltration process and the high cost of diafiltration are disadvantages.
The problem addressed by the present invention was to provide an alkaline cleaning formulation and a process for cleaning equipment used in the food industry of the type mentioned at the beginning which would enable cleaning to be carried out far more economically than in the prior art.
DESCRIPTION OF THE INVENTION
In the case of the water-containing alkaline cleaning formulation, the solution to this problem as provided by the invention is characterized in that the cleaning formulation contains only potash lye or a mixture of potash lye and another alkali, more particularly soda lye, containing at least 20% by weight of potash lye, expressed as hydroxide and based on the total amount of hydroxide present in the cleaning formulation, as its hydroxide component.
In the case of the cleaning process according to the invention, the solution to the problem stated above as provided by the invention is characterized in that it is carried out with a cleaning solution of which the hydroxide component consists solely of potash lye or of a mixture of potash lye and another alkali, more particularly soda lye, containing at least 20% by weight of potash lye, expressed as hydroxide and based on the total amount of hydroxide present in the cleaning solution.
It has surprisingly been found that the partial or complete replacement of sodium hydroxide by potassium hydroxide increases the performance of the membrane unit by at least 10 to 50%. Performance in this case is based on the permeate flows achieved. Investment costs and the energy consumption of the membrane filtration unit can thus be reduced. Higher concentrations of the soil load removed are possible so that the volume of the soil load is reduced and the yield of regenerated solution is increased.
Another advantage was discovered. In contrast to the prior art where the concentrate obtained is a mass which is fairly solid at room temperature and which leads to problems during discharge from the buffer tank and during subsequent processing, the concentrate obtained where the cleaning formulation according to the invention is used and in the practical application of the process according to the invention is a mass containing the soils which is liquid at room temperature and even at a temperature of 0° C. On the one hand, this simplifies the waste logistics; on the other hand, greater concentration can be achieved, providing for a higher nutrient content where the concentrate is used as an animal feed and for a higher energy content where it is used as a fuel.
The advantages mentioned above were achieved with a minimum of only 20% by weight of potash lye, expressed as hydroxide and based on the total amount of hydroxide present in the cleaning formulation. The disadvantage of the higher cost of using potash lye instead of soda lye is negligible because the potash lye is largely regenerated.
In the nanofiltration of EDTA-containing cleaning solutions, the performance of the membrane filtration unit is likewise increased by replacement of the sodium salts by potassium salts. Disadvantages arising during filtration through the use of EDTA can thus be compensated or even overcompensated simply by using potash lye and EDTA in the form of the free acid or its potassium salt. The disodium salt of EDTA may also be used providing this does not increase the sodium ion content of the formulation beyond certain limits. If all alkali metal ions are counted as alkali metal hydroxide, the potash lye content of the cleaning formulation, based on the total amount of hydroxide present therein, should not fall below 20% by weight. Generally speaking, the performance of the filtration unit increases with the ratio of potassium to sodium ions in the cleaning formulation, i.e. sodium-free cleaning solutions produce the highest throughflow rates in l/m
2
h.
The cleaning formulation preferably contains a mixture of potash lye and another alkali, preferably soda lye, containing at least 50% by weight of potash lye, expressed as hydroxide and based on the total amount of hydroxide present in the cleaning formulation.
The advantage of the EDTA-free cleaning formulation containing at least 50% by weight of potash lye lies in the possibility of directly using the soils filtered off without any aftertreatment as an animal feed, for example as a pig feed, because a high potassium salt content can be tolerated more rea
Krack Ralf
Patten Anja
Rossner Dietmar
Boyer Charles
Grandmaison Real J.
Gupta Yogendra
Henkel Kommandigesellschaft auf Aktien
Jaeschke Wayne C.
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