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Assuring flawless hygiene of membrane filtration systems is a complex science. This is a summary of the important aspects that allow to convert costy necessities into sustainable investments.
- Separation of raw materials into molecular components
- Filtration means contamination
- Contamination has a negative impact on the performance
No membrane process is possible without cleaning and cleaning constitutes a key technology in membrane separation.
In recent years, through specific and innovative cleaning processes, Halag has invested a lot in the development of modern methods for maintaining the value of membrane systems.
Membrane systems seem to be simply constructed. In reality, however, they are extremely efficient systems that are capable of separating mixtures at the molecular level at very high throughputs.
Halag addresses the development of solutions for all of these 4 technologies and has compiled detailed knowledge not only about their application, but also about the problems that result from using these processes.
What matters to us the most is to work out the best possible cleaning strategy for the concrete customer application,
i.e. for the user-specific membranes and separation processes in operation.
- Filtration means the accumulation of molecules on and within the membrane
- Flow technology influences the structure of the fouling layer
- Reversible fouling = concentration polarisation
- Irreversible fouling = protein gel
Why are other measures valid for the cleaning strategy of hygienically clean and optimally functioning membrane systems than is the case for conventional CIP cleaning?
During the filtration, molecules accumulate on and within the membrane. On the surface of the membrane a boundary layer forms that is only a few micrometres thick. This boundary layer is of vital importance for the performance of the membrane, because primarily it has an effect on the mass flow through the membrane.
Besides this known surface contamination, molecules also accumulate in the pores of the membrane, which also have a decisive effect on the filtration process. The deposits in the pores are primarily responsible for an altered retention capacity of the membrane, because they change the loading and surface properties of the membrane. This in turn changes the filtration properties of the membrane and thus the possible result of the whole filtration plant. Fouling is a natural and unavoidable phenomenon of filtration.
Practically all membranes, in all applications, are subject to fouling. We differentiate between reversible and irreversible fouling, based on the principle of how firmly the molecules adhere.
- After a certain time, convection and back diffusion come into equilibrium.
- The wall concentration (Cwall) is much higher than the concentration in the core stream (Cbulk) !
As the filtration continues, more and more molecules are transported to the membrane. There the larger molecules are retained. They build up a second layer on the membrane. The dynamic build-up of this layer is called concentration polarisation. Concentration polarisation has an effect on the performance and retention of the filtration.
This effect can be recognised by a drop in the permeate throughput in the first minutes of the filtration process.
In spite of its very low thickness of only a few micrometres, the influence of the fouling layer on the filtration is enormous. The performance of the plant, i.e. the throughput of permeate, is very severely reduced, because the fouling layer acts as an additional filtration layer. This additional layer increases the retention of other molecules, which can have an undesirable effect.
Fouling cannot be avoided, but through appropriate cleaning strategies, suitable membrane selection and well-aligned operating conditions, it can be minimized.
- Water as carrier
- Enormous surfaces
- Plant-related concentration determination = liquor ratio
- Quantity per surface unit
- Cleaning of the surface and the membrane pores
- Sensitivity of the membrane material
- No visual assessment possible
- Moistening requirement promotes bacterial growth
- Only the filtration performance gives an indication of the cleaning Performance
Sustainable maintenance of membranes involves the removal of the irreversible layer through the targeted application of cleaning chemicals. However, there are restrictive limitations when applying chemical cleaning agents in membrane systems.
Dr. Herbert Sinner, former head of tenside chemistry at Henkel in Germany, recognised already at the end of the nineteen-fifties that there are in total four factors that significantly affect the cleaning result.
The so-called Sinner Circle that was developed by him indicates that the factors time, temperature, mechanics and chemistry are in close interdependence.
- In order to lower the cost-relevant factors of time (production stoppage) and temperature (energy costs),
we need to pay attention to the factor chemistry, since the mechanics factor is only variable to a slight extent.
- This is not just a matter of purely increasing the quantity or concentration of the cleaning chemicals,
but above all it is a question of selecting one or a combination of more cleaning chemicals that are tailored to the contamination profile.
Thus chemical cleaning is thus the most important measure for removing residues that result as undesired substances from the filtration, in other words the elimination of the irreversible fouling.
The variety of cleaning chemicals available offer a kit of almost inexhaustible possibilities for removing fouling, but it is important – as in every good recipe – to know the mode of action of all ingredients and not to ignore any possible interactions. By definition, a membrane is considered to be restored to its original condition, if the molecules being filtered are no longer detectable on or in the membrane.
However, the components and ingredients in the water can drastically alter the efficacy of the cleaning components.
Due to the fact that the channels and pores in the membrane are only a few nanometres in diameter, the minerals in the water (water hardeners) or micro-organisms can block these and thus prevent access to the contaminating molecules that are to be removed by the cleaning chemicals dissolved in water.
- Benefit from the positive synergies of different ingredients
- Increase cleaning power by combining
- Interactions can produce undesirable effects
With regard to the chemistry itself, due to the highly complex and always variable composition of the residues, there is no universal cleaning agent that would be capable of removing all types of residues. Most cleaners are used in the form of formulated mixtures. But if these are be successfully utilised, the following must be separately considered in the membrane maintenance:
The fact that no residues can be detected in the flushing water is no indication that the system and membrane are clean. Here there is a large and significant difference to CIP: even the smallest amounts of residues on or in the membrane alter their separation characteristics and thus their process technological advantages.
Successful membrane maintenance involves restoring the original condition of the membrane with regard to its separation characteristics. Over time, formulated cleaning agents can even damage the membranes, or make them more susceptible to contamination, since they have not been designed for the individual system concept and varying contamination profiles.
Tailor-made cleaner composition
- Basic material e.g. Bulk sodium hydroxide
- Supplementing with additives
- “As much as necessary, but not more”
Your added value
- Tailor-made ingredients and concentrations
- Reduction of packaging through bulk transport
For this reason, experience has shown that instead of propagating a ready-made formulated cleaner as a universal cleaner, only those cleaning components will be employed that are suitable for removing the undesired residues at the customer’s site. Efficient additives and components that support cleaning, as well as components that nurture the membranes,
can be made up at any time and in a wide variety of concentrations in order to achieve an optimal result.
- Knowledge of what, how often and when
- Interaction of procedure and ingredients
- Optimisation of costs without compromising the hygiene requirements
- On the basis of local conditions
- Process technology & hygiene know-how
- Validated in the laboratory and pilot plant
- Use of additives
Besides the obvious necessity of responding to the wide variety of contamination profiles with individual chemical components in variable concentration, the cost factor for transportation of formulated cleaners should not be neglected.
Chemicals and water are used in alternating sequences. At the same time the sequence of application is vitally important. As a process-oriented manufacturer of cleaning chemicals, Halag’s know-how lies in the knowledge of what, how often and when.
The classic cleaning cycle, similar to a washing program in a household washing machine, cannot lead to the desired result, because the cleaning procedure has already been set.
Due to the particularities and special requirements that have previously been described for cleaning membrane systems, a flexible method of operation is necessary.
Since there is hardly a membrane system that resembles another with regard to volume, membrane geometry and material, and the requirements are different regarding cleaning in each plant and dependent on the application, it is crucial to first carry out an exact review and specify a cleaning strategy appropriate for the requirements.
Laboratory membrane System
Halag has created a special concept for membrane maintenance under the abbreviation AMCTM.
The Additive Membrane CareTM concept includes:
- Laboratory and pilot membrane systems developed in-house for practical simulations of customer conditions and for developing sustainable cleaning concepts.
- Testing possible of all membranes available on the world market.
- Application and chemical technology testing of the interrelations between the dairy product, filtration and cleaning.
- Experimental set-ups with a variable sequence of cleaning agents, their concentration, temperature and residence time.
Defined contaminations of the membranes are carried out, and when developing cleaning profiles, we compare the mode of action of formulated cleaners on a daily basis with the application of the additive concept.
Here we discover a continually increasing number of cases where the procedure with formulated cleaners does not achieve the desired result. If the components are added one after another and in varying concentrations, significantly better results can be obtained.
Halag has a wide range of additives at its disposal and is continuously extending this on the basis of concrete new requirements. Halag’s customers receive the most suitable additives for their applications and membrane systems for optimal application of the additives, together with the associated instructions for use.
The process technological know-how of Halag Chemie allows us to carry out the selection of suitable sensors, which reflect exactly the actual situation for the particular process and appropriate for the plant design. It is only on the basis of the knowledge of the continuously changing local situation, that the optimal recipe and mixture of additives with acid and alkali can be determined for the specific situation.
- AMC is a novel technology, making membrane cleaning extremely accurate, easy and economic.
Based on a software with stored contamination and cleaning profiles in the form of experimental models, the addition of additives is determined on-site with AMC. The additives are fed directly to the systems by controlled metering pumps, where they are added directly into the on-going cleaning programs. When retrofitting existing plants to AMC,
the existing PLC program requires very few modifications. The sequences remain the same. Only the recipe has to be changed within a sequence. AMC is the logical and consistent further development and an improvement over existing solutions.
In addition to optimal cleaning, and thus nurture of the membranes, AMC offers another benefit, namely in the process of continuous evaluation of the membrane performance, a dynamic picture of the processes can be additionally presented. This offers new insights and opens up potential for further optimisation.
In conclusion, through the gaining of relevant information during filtration, AMC makes sustainable cleaning and care of membrane systems possible. This is based on using individual sensors and computational models. Thus we are following the trend of using sensors embedded in industrial systems as direct access to technical information.
If this is correctly implemented, the risks of poor or incorrect cleaning are reduced.
Cleaning strategies on the basis of individual situations
- AMC provides the right combination and quantities of chemicals.
- AMC reacts to the specific time-varying conditions.
- AMC allows the best-possible utilisation of the chemicals.
- AMC reduces risk of permanent fouling.
- AMC ensures the lowest possible exposure of the membrane to chemicals.
- AMC reduces transport costs of chemicals.
- AMC ensures lower environmental pollution.
We utilise digitalisation in order to better support our customers.
The company is located in Aadorf in Eastern Switzerland. Here motivated development and consulting teams solve cleaning and hygiene problems. Research and development, state of-the-art production facilities and individual customer solutions have made Halag a leading company in the sector of industrial Hygiene.
- 1970 Founded byHeinrich A. Leimbacher
- 1993 Integration in the agricultural group fenaco
- 2010 Relocation in the new building compliant with the Minergie standard
- > 60 Employees in production, development, administration and sales
- ISO 9001 and ISO 14001 certified
- Market leader in the Swiss foodstuffs and drink producing and processing industries as well as processing in
agricultural and livestock farming
- Modern research and analytical laboratory and production
- Branch experts in consulting and sales and marketing
Our product range offers highly specific cleaning agents and disinfectants for food and beverage and other industrial sectors. In addition, private label products are developed and manufactured.
To see our complete product rage in German, French or Italian, sorted by application, please click here: range of products.
The difference lies in the service. Supplying cleaning agents and disinfectants to order – many can do that. Profit from our personal consultancy, and also from the four service modules around personnel and industrial hygiene, safety, monitoring and applications engineering. Invest in sustainability, cut costs and save resources.
Personnel and Industrial Hygiene
Halag Chemie AG maintains a laboratory with a wide development methodology. Delivery service in the shortest time is guaranteed. Our advisors are gladly available for you by telephone or on location at any time.
Halag Chemie AG
Tel. +41 58 433 68 68