Julkaistu ruotsin johtavassa puhdastila teknologia lehdessä 2000. Julkaistu Cleanroom Technology lehdessä UK 2000. Air purification in gene laboratories by Hans Brunila, (B.Sc) Finland A novel method to remove even the tiniest particles (1 nm to 100 µm) from air has been developed in Finland. The process, called NANOBIO, is the result of several years of intensive R&D work both in Finland and in other countries. The process can substantially reduce the energy requirements for space heating and cooling, as air flows through the cleaning unit with fewer obstructions than other equivalent equipment. The air cleaning requirements in gene laboratories are very strict considering the concentrations of very small particulate matter. Controlling tiny particles of DNA is particularly difficult given their wide size range from 1 nm to 100 µm. The problem of trapping small particles is also relevant for cleaning air in hospitals and other isolation areas, such as nuclear power plants, medical industries, and for defence against biological warfare. The new process was been developed specifically to meet these very demanding air cleaning applications. Air cleaning No filtering medium is used in the new method. The airflow is forced through an air tube or duct. The length of the cleaning depends on the airflow, volume and prevailing particle concentration. Three specific effects are concentrated on the air to be cleaned: a strong negative ion impact forces the particles to flow towards a collection area; the particles receive a negative charge from the negatively-charged ions (this only applies to those particles that can be electrically charged); a positive electric field in front of the collecting area attracts particles towards the collecting surfaces. The collected concentrations of particles are removed by flushing. When the collected particles contain material that is environmentally harmful or dangerous to human health, disinfectants or neutralising ingredients may also
be applied. The new method is fully automatic. The unit can be cleaned through flushing during the air cleaning process. The frequency of the cleaning, once every 24-hours or once a week, is controlled by a timer according to prevailing circumstances. The cleaning process takes only 20-40 seconds. If dry cleaning of the unit is preferred, the air cleaning process must be switched off for 1-5 minutes. Cleaning efficiency Tests on the cleaning efficiency of the unit were carried out at the University of Kuopio, Laboratory of Air Physics and Chemistry. Figures 1 to 3 show the cleaning efficiency of a unit designed with a 1 m duct. A standard cleaning duct is 1.5 m long. The applied air volume in the tests represents an average air volume in practice. Figure 1: Typical particle size distribution during testing. Figure 2: Cleaning efficiency at 990 mm from the inlet, with a flow rate of 0.5 m/s (226,000 l/h).
Figure 3: Cleaning efficiency at 990 mm from the inlet, with a flow rate of 1.0 m/s (452,000 l/h). Reduced energy consumption The unit is a novel, high-tech product that can remove even the smallest particles from the air with great efficiency. Present air cleaning methods are not effective on particles of 1-5 nm. This has caused major difficulties for air recycling, which may now be overcome. Substantial energy is saved due to the reduced need for reheating/recooling room air. Air flows without obstruction through the unit ducts, which require no fabric filters. The energy consumption of the units themselves is only 20-160 W. Potential applications The units are manufactured in three standard sizes (see Figure 4) with voltages ranging from 20-40 kv and currents from 1-4 ma. Each model contains all the necessary electronics, voltage and current controls, cleaning interval settings and display on malfunction. Figure 4: The three unit sizes.
The cleaning unit can be connected directly into the air duct distribution net. The intake air into the room space is consequently clean. When an individual air-cleaning unit for a specific room area is installed, the volume of intake air can be reduced by up to 80-90%. Units may be placed in room areas adjacent to walls, in cupboards or other convenient areas. They only require connection to the mains and water supply when liquid flushing is applied. Sewage connection is not necessary as the consumed water can be collected into individual basins with volumes (2-4 litres). The unit also provides an economical solution as the purchase price for a standard unit is only USD 7,300. Current status The current patent protection covers 83 countries (pending). Large-scale production is planned in the spring of 2000. There has been intensive cooperation with the University of Kuopio, Laboratory of Air Physics and Chemistry for several years, and this will continue. For further information please contact Hans Brunila (Sales Engineer) Genano Ltd. Finland Tel.: +358-2-846 0100 Fax: +358-2-846 0150 E-mail: genano@genano.fi Internet: http://www.genano.fi/