12/20/2011 • Food design, hygiene and monitoring • Plant construction and components

Heat recovery with pitfalls

Insufficient pre-separation of grease aerosols leads to greasy heat exchangers and considerably reduced heat recovery rates.

Food processing factories increasingly recover heat from the oily and greasy exhaust air. It is a tried and tested method required by the German Energy Savings Act EnEV for extraction systems with a capacity over 4.000 m³/h since recently. In practice, heat recovery often causes annoyance, however: In many cases, the maintenance costs are higher than the energy saving. According to Rentschler REVEN, this is due to inappropriate grease filters, which let too many aerosols pass into the exhaust air duct. Contamination accumulates in the heat recovery system within a short period and requires cleaning operations at regular intervals. Otherwise, the heat recovery rate shrinks, i.e. the heat exchanger becomes ineffective.

To remedy this problem, REVEN recommends highly efficient grease separators based on the cyclone principle. They ensure high separating rates. The separated grease does not accumulate as in traditional filters. The grease particles are ejected and drained off to a collecting channel. Cyclone separators are virtually self-cleaning and prevent contamination in the exhaust air duct and the heat recovery system.

Traditional mesh filters are no longer allowed. They are often replaced by baffle plates. However, available solutions should be compared critically. It is important that the separating efficiency was measured in accordance with VDI 2052 and that the equipment carries the correct test sign. An unambiguous marking should make reference to DIN 18869 or the US-American guideline UL1046.

Food processing companies still using old filters should replace them by modern cyclone separators. Due to standardized dimensions, this is no problem. Alternatively, a duct separator could be fitted into the exhaust air duct between the extraction point and the heat recovery system. This separator captures the remaining aerosols that are not collected by the grease filter. A duct separator is a cost-efficient solution particularly in large extraction systems and guarantees the trouble-free functioning of the heat recovery system.

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Rentschler REVEN

Ludwigstraße 16-18
74372 Sersheim

Phone: +49 (0) 70 42/ 373- 0
Fax: +49 (0) 70 42/ 373- 20