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Many facilities buy compressed gas tanks or evaporate liquid nitrogen to supply processes with dry, high-purity nitrogen. An in-house nitrogen generator, however, provides several significant benefits.
Pharmaceutical production processes and quality-assurance laboratories commonly use high-purity nitrogen for various purposes, such as gas chromatography, sample drying, and protecting compounds from the deleterious effects of oxygen or water vapor. Many facilities buy compressed gas tanks or evaporate liquid nitrogen to supply these processes with dry, high-purity nitrogen. An in-house nitrogen generator, however, provides several significant benefits.
An in-house generator typically is designed to remove particulate matter, compressor oil, water vapor, and oxygen from laboratory air to provide highly pure nitrogen. The system employs a coalescing filter to remove trace liquids and particulate matter. A pressure-swing adsorption system that contains a pressurized-carbon molecular sieve adsorbs nitrogen, but not other gases. Users deliver the nitrogen to the production or quality-control system by removing the pressure on the molecular sieves.
Generating nitrogen in house can help increase safety in a facility. An in-house generator is designed to supply the gas at the pressure and flow rate required for the desired operation, and employees can adjust these parameters at any time by turning a knob. In contrast, a compressed-gas tank contains the gas at a high pressure. If the valve on such a tank is compromised, the gas could displace the air in the facility, thus potentially asphyxiating the employees working there. A compressed-air tank also must be replaced from time to time, and if a technician loses control of the tank while it is being moved, a serious accident could occur. Finally, employees that use liquid nitrogen to generate nitrogen gas run the risk of getting frostbite.
In-house nitrogen generation also is convenient for many facilities. Once an in-house generator has been installed, it can provide the desired gas for 24 h per day and for seven days per week without additional effort. In contrast, compressed-gas tanks and liquid-nitrogen containers require the operator to ensure that an adequate supply of the gas is available for the task at hand. Sometimes operators must change the supply at an inconvenient time. For example, compressed-gas tanks typically are stored in external facilities, and it may be inconvenient to replace them, especially in inclement weather.
Facilities also may be able to decrease their costs by using in-house nitrogen generators. These units extract the desired nitrogen from the air and, once they have been installed, do not entail any costs beyond electricity and annual maintenance. Many users report that these units pay for themselves in a year or less, and that operating costs can be reduced by 50% or more. If a site uses compressed-gas tanks to supply the nitrogen, it must consider the cost of each tank as well as other costs, including those of demurrage, the time required to install the tanks periodically, the paperwork to order tanks, and inventory control.
In addition, in-house generators can help decrease a facility’s energy requirements. An in-house generator operates on a normal 15 A circuit and consumes a small amount of power (e.g., a few hundred watts). In contrast, compressed-gas tanks and liquid-nitrogen tanks require a significant amount of energy, including the energy needed to pressurize, compress, and transport the gas to the point of use. An in-house nitrogen generator also can provide greenhouse-gas benefits because it does not need to be compressed and transported to the point of use.
Benjamin Chal, a process-development engineer at MedImmune, a manufacturer of vaccines and monoclonal antibodies, is a typical user of an in-house nitrogen generator. Chal has used various Parker Balston nitrogen-generation systems to provide the necessary gas for several years. Recently, he installed a Parker Balston DB-20 system to provide a flow rate of approximately 300 L/min of nitrogen to convert liquid formulations into dry powders (i.e., through lyophilization and spray drying) for long-term storage stability.
The DB-20 nitrogen-generation system produces a flow of nitrogen as great as 173 standard ft3/h at 99.99 % purity. The unit can achieve higher flow rates for nitrogen gas of lower purity (e.g., a flow rate of 2250 standard ft3/h can be obtained if 95% nitrogen is acceptable). The system operates at pressures as high as 80 psig. The resulting nitrogen has a dew point as low as –40 °F and includes no particles larger than 0.01 µm. An optional oxygen monitor with alarm relay outputs can be supplied to alert the user to open a backup supply or otherwise protect the sample. “The nitrogen-generator systems are very reliable; once the generator is installed, a continuous nitrogen supply of consistent purity is available within minutes from startup, and all service and maintenance can be performed on an annual basis,” reported Chal.
Compared with tanks, in-house nitrogen generators provide several significant benefits to a facility, such as increasing the safety of handling the gas. The units produce nitrogen at the precise flow rate and pressure required. In contrast, when high-pressure tanks are employed, various safety issues must be considered. In addition, an in-house generator provides significant cost savings and has a lower environmental footprint than tanks do.
Peter Froehlich is president of Peak Media, 10 Danforth Way, Franklin, MA 02038, tel. 508.528.6145, [email protected].