Margarine Remelters Heat Exchangers
A world leading company of the food and chemical industry contacted SACOME to solve the corrosion problem in an existing heat exchanger intended for the remelting of margarine for its further reprocessing.
Several difficulties were involved in this application, not only the choice of the most suitable material but also an accurate interpretation of the thermal performance of margarine, a semi-solid product that must change into liquid state to be reprocessed.
Other geometries could be used, as scraped surface heat exchangers, but their higher initial and operational costs, or the mechanical problems of the seals, make the tubular heat exchanger to be an attractive solution to bear in mind.
With the report and analysis from the UPCT (Technical University of Cartagena) an optimised thermal design from the required exchange area viewpoint was proposed, ensuring a correct performance of the tubular heat exchanger.
Based on our more than 40 references with margarine, the engineers from our Technical Department checked different configurations of our corrugated tube heat exchangers until proposing the one most suited to the client´s specifications.
Margarine is a water-in-oil emulsion in which the water phase is finely spread in the form of droplets in the continuous animal or vegetable fat phase. This product is produced in different stages, as preparation of the water and fat phase, emulsion preparation, pasteurization stage, chilling-crystallization and packing or filling.
In the case that margarine hasn’t got the required consistency and/or texture, then the product must be diverted to the balance tank for further reprocessing. In order to be returned and to be able to be reprocessed, the vegetable or the animal margarine, that has a semi-solid consistency, must be remelted in order to get the liquid phase and to be easily pumped and reprocessed.
The existing heat exchanger, manufactured in a standard austenitic stainless steel as 316L, was facing a corrosion process so we decided to ask for a sample to the client to analyse it and recommend a suitable material.
Thanks to our close relation with the UPCT University (Polytechnic University of de Cartagena), SACOME can draw conclusion about the origin of corrosion for avoiding it in future designs.
The experts of the UPCT did different analysis to the sample with signs of corrosion provided by our client, as chemical analysis by spectrography, macro and micrograph, concluding that the sample presented localised (pitting type) corrosion due to the combination of high percentage of chlorides (from the high content of salt of more than 1%) and high process temperatures.
The technicians from the UPCT analysed some comparative figures about the response from several stainless steels (both austenitic and austenitic ferritic type), not only against pitting corrosion, but also against crevice corrosion, stress corrosion cracking or intergranular corrosion.
On the basis of these figures, but also taking into account the commercial stainless steels available in the industry, the engineers from SACOME chose the most suitable material quality, among one of the duplex one proposed.
In margarine remelters, corrosion problems must be avoided with a correct selection of materials.
The fat blend in margarine consists of a mixture of single oils, emulsifiers, lecithin, flavors and other minor ingredients dissolved in the blend, as colorants or anti-oxidants, while the water-phase can have variable contents of salt.
This such varying composition and the phase changes involved in the heating of margarine, made it necessary to do a rheological analysis of the product, in order to be able to do an accurate thermal design of the heat exchanger.
That is why we asked also the client for a product sample, thanks to which we could get a full analysis of the thermal properties at different temperatures in the laboratories of the UPCT.
The modelling of the melting & crystallization process, the latent heat and the heat capacity, are essential features for the subsequent thermal design of the heat exchanger.
Tubular Heat Exchangers Design
Flanged tubesheet design
Process Flowrate (Kg/h)
Initial Temperature (°C)
Final Temperature (°C)
Thermal Duty (Kcal/h)
Pressure Drop (bar)
Floor Space (mm)