Exhaust air purification and heat recovery in food drying
Energy-efficient exhaust air filtration systems made in Germany
Production plants for food drying are confronted with the complex question of an efficient exhaust air purification with simultaneous waste heat utilization.
The food drying process is one of the oldest food preservation processes in the world. It is suitable for a wide range of products – from vegetables and fruit to spices or tea. Water is removed from the product through a constant high heat effect until the water content is between 18% and 25%, depending on the product.
Although food drying is a gentle process in terms of the aroma, texture and shelf life of the respective products, it is also a gentle process in terms of the product’s aroma, texture and shelf life. However, it is also a process with high energy consumption and a high exhaust air load.
Energy-efficient exhaust air treatment with KMA ULTRAVENT®
But how can efficient exhaust air purification be implemented in individual cases? Conventional exhaust air purification processes such as thermal or catalytic post-combustion achieve high separation values, but due to the high consumption of fossil fuels, these processes are very energy-intensive and thus have a negative impact on the carbon footprint and operating costs.
KMA Umwelttechnik offers an energy- and cost-efficient alternative with its ULTRAVENT® exhaust air purification system. Based on the innovative KMA electrostatic precipitator, the KMA ULTRAVENT® achieves a separation efficiency of up to 99 %. This process uses electrostatic charging to separate the finest grease and liquid droplets from aerosols as well as the smallest solids from the exhaust air stream – and does so with low energy consumption.
Modular design for comprehensive odor separation
In addition to the separation of aerosols and particles, an efficient exhaust air purification system in drying plants must also offer an efficient solution to separate odors reliably.
Thanks to the modular design, KMA exhaust air filtration systems can be seamlessly integrated into existing production plants. In order to also comprehensively treat the constant odor load, KMA combines its powerful electrostatic precipitator modules with the KMA UV light module or the KMA activated carbon filter. These modules efficiently and comprehensively remove up to 90 % of odorous aerosols, vapors and VOCs from the exhaust air stream. KMA exhaust air purification systems easily meet the legal requirements for clean air quality according to the national and regional legal regulations.
Efficient heat recovery to reduce CO2 emissions
For a high quality drying result, products must be dried gently and under constant heat. For this reason, not only are impurities such as aerosols, VOCs and other particles bundled in the exhaust air stream, but also valuable thermal energy, which is usually released to the outside world untreated.
This is not only cost-intensive and less energy-efficient, but also has a negative impact on the company’s life cycle assessment (LCA). This is where KMA comes in with its innovative heat recovery system. The purified exhaust air stream passes through the upstream filtration module into the heat recovery system, consisting of a heat exchanger and, if required, additional thermal heat pump. Heat exchangers and thermal heat pumps extract valuable thermal energy from the exhaust air and in order to make it usable for continuous use. In this way, KMA achieves enormous heat recovery rates, which result in the systems paying for themselves within a very short time period.
The recovered energy can then be fed back into the production process or used for other applications, such as heating the return water of the heating system.
Once the exhaust air stream has been comprehensively cleaned, it can either be transferred to the outside world in air extraction mode or returned to the production halls in energy-saving circulating air mode.
Powerful solution for numerous processes
The KMA exhaust air purification system is suitable for the following drying processes, among others
- Freeze-drying (e.g. instant coffee)
- Drum drying (e.g. instant mashed potatoes)
- Air drying (e.g. stockfish, dried vegetables)
- Drying of dough (e.g. sourdough starter)
- Condensation drying (hardener) (e.g. berries)
- Drying of animal feeds
Selected references from the food industry
Advantages of the KMA ULTRAVENT ® exhaust air purification system:
- High energy efficiency through reduced pressure loss of the filter medium
- Automatic filter cleaning system (CIP): time-efficient and hygienic cleaning for increased plant utilization
- Automatic discharge of the separated impurities
- Optional combination with systems for odour separation and heat recovery
- Meets the current national and regional environmental regulations (BImSchG, TA Luft)
- Durable stainless steel construction: hygienic with low wear – no need to replace filter elements
- High-performance filtration as an efficient alternative to thermal oxidation
KMA ULTRAVENT® – modular und flexible
KMA ULTRAVENT® is a modular exhaust air purification system consisting of the following filter modules:
The KMA ULTRAVENT® demister cells consist of stable 50 mm thick stainless steel wire meshes, which are fixed on the inlet and outlet side by an expanded metal mesh. The special rolling of the wire enables high separation efficiency of aerosols, droplets and mists. The cells are cleaned by the automatic washing system. An exchange of the demister cells is not necessary.
ULTRAVENT® electrostatic precipitator cells allow for a high degree of separation of smoke, dust and fine mist. The filter cells are characterized by their robust construction: Stainless steel frames and support rods, insulators in oil-resistant ceramic design and a filter design that has also been optimized for the separation of liquid and viscous substances make the electrostatic precipitator an extremely economical and durable filter medium.
Unsuitable filter media can quickly become blocked by the greasy deposits and thus lead to high follow-up and replacement costs. KMA electrostatic precipitators, on the other hand, can absorb large quantities of grease on their metal collectors. The exhaust air can flow through the filter unhindered.
The recovery of process heat can be carried out in parallel with the purification of exhaust air using a suitable heat recovery system. At low exhaust air temperatures, heat recovery can be optimized by a combination of KMA heat exchanger and KMA Ambitherm® high-efficiency heat pump. The heat recovered from the exhaust air is available for example for subsequent processes or for heating the building. Since the heat exchanger is installed directly next to the filter zone, it can be automatically cleaned regularly together with the filter module.
With the help of the KMA UV light module, many intensely smelling VOC molecules can be oxidized and separated. The result is a significant improvement of the odor situation, in many cases odors are completely eliminated. The KMA UV light module, like the KMA activated carbon filter, requires a comprehensive pre-separation of solid particles by the KMA electrostatic precipitator. After the UV-oxidation stage, either a reaction line or catalyst carbon is required to break down the ozone.
Activated coke is highly effective in absorbing many odors and vapors. Therefore it is used in food production as a universal agent for odour elimination. The odorous substances and air molecules accumulate on the surface of the activated coke and are thus removed from the exhaust air. For economical operation, a good pre-treatment of the exhaust air is always necessary, since impurities by particles or aerosols must be separated before the exhaust air enters the activated carbon filter.
For a reliable separation of odorous aerosols, vapors or gases, KMA uses the KMA exhaust gas scrubber based on the absorption principle. By using a suitable scrubbing liquid, these contaminants are bound and separated from the exhaust air stream. By using the upstream electrostatic precipitator, the KMA exhaust gas scrubber achieves a high separation efficiency at low water consumption.
KMA exhaust air filter systems can be equipped with an automatic filter cleaning system (CIP – cleaning in place). It is suitable for the cleaning of demisters, electrostatic filters, UV light and heat exchangers.
The automatic cleaning system convinces with its movable nozzle block, which is moved back and forth over the filter modules during the washing process, and is therefore unrivalled in terms of comfort and washing results. It enables regular, fully automatic and individually programmable cleaning of the filter cells. Thus, the automatic filter cleaning system minimizes the maintenance effort. The intelligent control of the cleaning process simultaneously reduces the consumption of washing water and detergent.