There are many complexities in the manufacturing of synthesized pharmaceutical products. Each plant is unique, differing from other plants in size, types of products manufactured, amounts and types of VOC used, and air pollution control problems encountered.
Production methods used in the manufacture of pharmaceutical products include both batch and continuous operations, although batch operations make up a majority of the processes. Emissions consist almost entirely of organic solvents including a range of volatile organic compounds (VOCs) and several Hazardous Air Pollutants (HAP) that escape from dryers, reactors, distillation systems, storage tanks, and other operations.
In a typical batch process, solid reactants and solvent are charged to a reactor where they are held (and usually heated) until the desired product is formed. The solvent is distilled off, and the crude residue may be treated several times with additional solvents to purify it. The purified material is separated from the remaining solvent by centrifuge and finally is dried to remove the last traces of solvent. Tablet coatings, aqueous or solvent based, may also be applied for taste and odor masking, physical and chemical protection, or controlled time release.
These batch processes can involve a range of varying exhaust volumes and VOC concentrations including ultra-high LEL (high concentration of VOCs), corrosive acids produced in the process off-gas and the post-combustion gases, and high air volumes and lower VOC concentrations.
The following processes in pharmaceutical operations may generate significant VOC emissions: