Pirobloc provides efficient, safe and custom solutions to heat industrial fryers and other tecnologies used to process food. Some of the most frequent are:
In continuous industrial fryers, heating by means of a thermal oil system, consisting of a thermal fluid boiler and a heat exchanger, is the best technological alternative.
These industrial fryers can be used for crisps, nuts, industrial confectionery, fish, vegetables, corn or other products like nuggets, croquettes and pies.
For almost all of them, vegetable oil usually requires temperatures in the region of 175°C. There are different alternatives for heating vegetable oil at this temperature. Thus, these types of machines may use electric heating coils directly submerged in vegetable oil, gas burners directly coupled to a combustion chamber, submerged heating coils or, the preferred option, a thermal oil boiler associated with an external heat exchanger of thermal oil – vegetable oil.
The thermal oil boiler heats the fluid by the combustion of gas. This thermal oil is circulated by a centrifugal pump to a tubular heat exchanger of thermal oil – vegetable oil. Finally a vegetable oil pump, also centrifugal, sends the hot vegetable oil inside the fryer.
This thermal fluid heating system is simple but offers numerous important advantages over other heating systems. One of these advantages is the conservation of vegetable oil.
Vegetable oil is likely to degrade rapidly as a result of the high temperature. The higher the film temperature of the vegetable oil, the earlier it will oxidise and break down. When heating with electric coils or direct burners, the vegetable oil reaches very high temperatures, exceeding 500°C, and deteriorates rapidly. With a thermal oil-vegetable oil heat exchanger, the temperature of the former is of the order of 230°C; thus ensuring a stable and accurately controlled temperature of about 175°C. This value is entirely selectable depending on the product, with precisions of ± 1°C. In other words, the film temperature of the vegetable will be as low as possible as the hot spot will not exceed 230°C.
Also, using an external heat exchanger makes periodic cleaning of the equipment easier, as the tube bundle is completely external and easier to clean. The fact that the heat exchange takes place outside the fryer is a great advantage, since the oil carries traces of product as fine particles that tend to be deposited on its base. If electric heating elements or heating coils are positioned in the lower part of the fryer, the product particles are deposited on the surface where they become charred and accelerate the oil degradation process.
In terms of efficiency, a thermal fluid boiler is also the most economical alternative. Some products, such as crisps, require a high thermal power for processing, since 80% of its content is water. To achieve suitable frying quality, the water has to be evaporated which requires a significant quantity of energy. The overall efficiency of thermal oil heating is around 90%, since the only energy loss is in the flue stack. This energy is recoverable using heat recovery systems, such as an economiser which pre-heats the combustion air.
Pirobloc has extensive experience in the design and installation of thermal fluid solutions to provide efficient and sustainable heat for the continuous fryers used in processed food products.
The following diagram shows the operation of these fryers with a heating system using a thermal oil boiler and an external heat exchanger.