Design and Commissioning of a Vapor Phase Miniplant System with Laboratory Fume Hood Constraint

Exothermic reactions involving vapor reagents under pressure are common within chemical manufacturing, but scale-up of these systems usually goes through multiple stages of development (lab → miniplant and/or pilot plant → commercial).  Safe management of exotherms and undesired consequences of the chemistry such as side reactions must be well understood to allow for a robust process implementation and safe process operation.

Manufacture of some silanes involve exothermic chemistries yet kinetic limitations often force operating temperatures exceeding 300 °C, which pushes the upper boundary of conventional heat transfer fluids if used to dual purpose heat and manage the exotherm [1, 2].  To accomplish a process evaluation at miniplant scale, an OEM-supplied, resistance-heated, fluidized sand bath system was modified to accommodate a multi-tubular reactor arrangement while operating at temperatures up to 600 °C and pressures up to 150 psig.  This arrangement allowed for very high external heat transfer coefficients which supported exotherm mitigation, even in the case where the tubes operated as fixed beds.  Flow was oriented single pass to avoid extended post-reaction dwell time and extended preheat for the chemistries of interest, but this made mechanical implementation within the sand bath more challenging.  Process feedback on the bed temperature profile was accomplished with multiple axial multi-element thermocouples, each housed within a specialized thermowell.  Design considerations were placed on removing the catalyst materials following the reaction campaign while allowing for adjustable clearance in the position of the sand bath through use of a specialized lift cart.  This poster highlights the challenges associated with both designing and commissioning the system within the space constraints of a laboratory hood.

[1] Koerner, G., “Introductory Remarks on the Peculiarities of Silicone Chemistry” in Silicones Chemistry and Technology, Bayer AG, Th. Goldschmidt AG, Wacker-Chemie GmbH, and Haus der Technik, editors, CRC Press, 1991.

[2] Feldner, K., “Chemistry and Technology of Direct Synthesis” in Silicones Chemistry and Technology, Bayer AG, Th. Goldschmidt AG, Wacker-Chemie GmbH, and Haus der Technik, editors, CRC Press, 1991