Safety guidelines for continuous processing

This chapter gives safety guidelines for continuous chemistry experimental work in the laboratory. It also applies to continuous manufacturing of small-volume products using laboratory fume hoods. Pressure relief devices are needed on the discharge of positive displacement pumps. They are needed immediately downstream from back pressure regulators, at the inlet and outlet of plug flow reactors (PFRs), and on all pressure vessels that are not always open to an atmospheric pressure vent.

Venting should be sufficient so vessels do not pressure up when filling, with vent paths free of block valves. Vent knockout vessels should be present and appropriately sized to catch process materials in case vessels overfill and also catch bubbler liquid in case of suck back. Plugging and fouling can be minimized by using a large enough tubing size, monitored with pressure transmitters, and managed with strategically placed valves and tees. Inerting is a primary line of defense against fire.

Grounding and bonding is used when flowing from one vessel to another to prevent static charge buildup and sparking. Nonconductive liquid flowing through nonconductive tubing at high velocities should be avoided. Heat exchange rate should be sufficient for exotherm removal and chemical reaction safety, and chemical reaction safety analysis should be done, including calorimetry and thermal stability. Secondary containment should be provided, as well as sensors, to detect leaks and hazardous concentrations.

Materials of construction must be compatible with the chemistry under reaction conditions. Automated alarms, interlocks, and/or auto-shutoffs should be included based on temperatures, pressures, and fill levels. Emergency stops should be installed. Reactant accumulation or total mass accumulation; overfilling product collection vessels; undesired phase changes; backflow into feed vessels, vents, or utilities; and static electricity buildup should all be prevented.