Project SynopsisPerform a process safety review and develop safety improvement design features for both a lab scale and pilot scale fine silica powders manufacturing facility.
SILICA POWDERS LAB AND PILOT PROCESS DESIGN AND SAFETY REVIEW
The client is a global manufacturer of specialty chemicals which operates a plant that produces specialized (high value), highly porous, micron size silica powders for analytical chemistry and pharmaceutical applications. These silica powders may be organically bonded and are dry processed (size fractionated) in a number of laboratory and pilot scale equipment. There was a concern that some bonded silica powders may be combustible and pose a risk to personnel and equipment when processed under certain conditions, however, these risks had not been established.
Process Engineering Associates, LLC (PROCESS) was contracted to (1) evaluate the design and operation of the laboratory and pilot scale powder dry processing equipment with respect to processing combustible silica powders, (2) recommend changes to improve process safety, and (3) develop a scope of work and preliminary cost estimate for any such improvements, and provide a proposal for developing final process design documentation for the improved/modified processes. This last objective was not met due to client directed changes during the project. In addition, for one pilot scale dry sizing process, PROCESS was contracted to document the design of the existing “as built” process and conduct a process design and safety review of this process.
The set of silica powder dry processing equipment consists of: the pilot scale Dry Sizing (DS) unit, a 30 inch diameter SWECO vibratory screener with a dedicated dust collector, and four laboratory scale particle size separators. The DS unit was documented, and is used to separate silica powders (<~50 micron) into coarse, intermediate, and fine particle size fractions by means of a variable speed Air Classifier and a Fines Fraction Cyclone. A blower at the end of the process provides the air flow that drives the process. None of the equipment had an explosion proof motor nor was it rated for combustible dust environments.
The design and operation of all of the powder dry processing systems were evaluated with respect to the combustible/explosive atmosphere issues related to processing combustible silica powders, and process safety improvement recommendations were developed. For the DS Process in particular, the scope of work also included (1) documenting the existing “as built” process, (2) conducting a process design review and safety review with the objective of identifying areas for improvement, and (3) conducting a Process Hazard Analysis (PHA).
Project deliverables included the following:
- Description of the existing “as built” DS unit: block flow diagram (BFD), process flow diagram (PFD), piping & instrumentation diagram (P&ID), a preliminary mass & energy balance (M&EB), and a process description
- A list of process improvement recommendations resulting from the site visit and process evaluation
- A PHA report summarizing the design changes recommended by the PHA team
- An evaluation of the safety risks associated with the processing of combustible silica powders in the DS unit, the SWECO, and three of the four smaller powder processing systems (with the fourth powder processing system being deemed out of service by the client).
- Specialty Minerals Processing
- Process design
- Process safety evaluation