Precise and accurate on-line determination of dryer gas composition by monitoring inlet, in-dryer and outlet gas composition for common solvents from the high percent level down to ppm concentrations for increasing dryer operation efficiency.
Drying of active pharmaceutical ingredients (API), intermediate products and finished products is a major process employed in the pharmaceutical industry. Materials are frequently dried to remove solvents used in processing. The material is placed into one of several types of dryers including both agitator and tray dryers. The dryer is typically sealed and a vacuum applied while the temperature is elevated and dry inert gas flows through the dryer. The end point of the drying process is usually determined by a technician who manually samples the API or intermediate a number of times during the process to determine the residual solvent contents by conventional laboratory analysis.
Alternatively, some drying processes are run for a prescribed amount of time, often resulting in a longer drying time than required. On-line dryer monitoring has the potential to eliminate the inprocess sampling during drying and eliminate the inefficiency of over-drying allowing for a higher throughput through the dryers
Determining the actual drying end point can eliminate processing problems from over-drying, reduce drying and cycle times, lower energy costs and minimize product sampling with its associated hazards, time and costs. Real-time monitoring of drying to avoid over-drying may result in lower product scrap or rework of high value active pharmaceutical ingredients. Increasing the throughput by stopping the drying process when it is complete can effectively result in increased throughput and may eliminate the need to invest capital in additional drying capacity.
A process mass spectrometer can be installed to monitor the offgas of the dryer as well as the inlet gas and multiple sample points in the dryer using an optional stream switching manifold. One mass spectrometer can also be used to analyze multiple dryers.
Sample lines feed the gas to a sample conditioning system which filters out any particulates. The filtered gas goes to a stream switching manifold which sequentially sends the gas streams to the mass spectrometer. A local computer running process software controls the mass spec, the sample system and stream selection, and reports the results to a the dryer control plc or computer.