Controlled Atmosphere Systems
Controlled Atmosphere (CA) is a storage technique whereby the level of oxygen is reduced and CO2 is increased. Quality and the freshness of fruit and vegetables are retained under Controlled Atmosphere conditions without the use of any chemicals. Under CA conditions, many products can be stored for 2 to 4 times longer than usual.
Penn Refrigeration have been experts in controlled atmosphere environments for many years. Growers in Niagara and beyond have relied on our expertise to ensure their fruit and food storage facilities operate efficiently and maintain the correct atmospheric conditions.
Vegetables and fruit respire; they take in oxygen (O2) and give off carbon dioxide (CO2). The storage of fruit and vegetables in a gas-tight environment allows the oxygen level in the air to be lowered and the level of CO2 to increase. Long-term storage of vegetables and fruit actually involves inhibiting the ripening and ageing processes, thus retaining flavour and quality. Ripening is, in fact, postponed. This occurs as a result of modifying the gas conditions in the cool cell so that the respiration of fruit and vegetables is reduced.
Having the proper system requires N2 generators, O2 Scrubbers and CO2 absorbers.
VPSA N2 Generators
VPSA technology (Vacuum Pressure Swing Adsorption) is based on an energy-efficient, low pressure technique. A VPSA can both circulate and inject. During circulation, the residual oxygen level reduces along with the oxygen in the storage cell. Circulation is the most energy efficient mode for lowering the oxygen level in a storage area. So-called pull-down time is an indication of the time necessary for circulation to bring your storage cells to the required oxygen levels. During circulation, the VPSA reduces the oxygen concentration in the cell up to 30% quicker than when injecting.
The advantage of injection is that a cell can be kept at slight over-pressure so that ULO conditions (ultra low oxygen, <3%) are even possible in a storage area with a minor leak (ask your cool cell constructor or Van Amerongen for further advice). With the VPSA, you can switch between injecting and circulating and vice versa at any given moment.
PSA O2 Scrubbers
PSA stands for Pressure Swing Absorption and is ideal for projects that require a great deal of nitrogen which must be supplied at high pressure. This involves cool houses with many (>20) cool cells or cool houses in which oxygen removal takes place in multiple cells simultaneously. This concerns volumes greater than 85 m3 h-1. A PSA is suitable for making very pure nitrogen. We supply PSAs with a residual oxygen value of <0.1% and volumes up to 1,200 m3 h-1.
CO2 Absorbers
Fruit ‘breathes’: it uses oxygen (O2) and produces carbon dioxide (CO2). A CO2 absorber removes the carbon dioxide (also referred to as carbonic acid) that forms from your storage cells in order to prevent concentrations getting too high and causing damage to your fruit.
Determining the capacity of the CO2 adsorber
In order to determine which CO2 adsorber is suitable for your situation, the following must be considered;
- Number of cool cells;
- Cold store dimensions;
- Type & quantity of product in the cold store (how much CO2 does it produce);
- Preferred storage conditions for CO2 in the cell.