BHS-Sonthofen Inc.

BHS Pharma Rotary Pressure Filter

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Source: BHS-Sonthofen Inc.

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Process Testing and Scale-Up for a BHS Pharma Rotary Pressure Filter as a Replacement for Two Inverting-Basket Centrifuges at a Bulk Pharmaceutical Manufacturing Facility

Abstract
In the manufacturing of this bulk active pharmaceutical ingredient (Bulk-API), the plant needed to increase production and to improve the washing efficiency of the process. The current process required two (2) inverting-basket centrifuges operating in parallel from one reactor to a downstream pelletizer. Process testing was being conducted simultaneously in the laboratory and in the field to evaluate the BHS Pharma rotary pressure filter (Ph-RPF) as an alternative to the inverting-basket centrifuges. The lab testing used a BHS pressurized pocket leaf filter with 20 cm' of filter area while the fieldwork was conducted on a BHS rotary pressure filter with a filter area of 0.12 nr.

The paper discusses test procedures, data collection, filter media selection and other process parameters. Equations are presented to scale-up the results to a full-scale production filter. Scale-up data includes process conditions, production rates and filtration, washing, drying and discharge times.

The results are then compared to the existing process to determine the cost-effectiveness of a process change to one (1) Ph-RPF from two (2) inverting-basket cen-trifuges.' The operating savings from the Ph-KPF in terms of solvent consumption, energy consumption, number of units and maintenance costs as well as the capital costs for the equipment will yield a favorable rate of return on investment and an acceptable payback.

Keywords
Rotary Pressure Filter, Centrifuges, Inverting Basket Centrifuges, Solid-Liquid Slurry, Continuous, Thin-Cake, Pressure Filtration, Cake Washing, Drying, Filter Testing, Active Pharmaceutical Ingredients, Bulk Pharmaceutical and Chemical Production.

Introduction
In the manufacturing of this Bulk-API, the plant was examining the process to determine the most cost-effective method to increase production and improve the product quality with increased washing efficiency. A study was undertaken, by plant engineering and development, to examine the use of a BHS Ph-RPF to improve the overall process operations for product quality and production rates.

BHS Rotary Pressure Filter
The Ph-RPF, shown in Figure I, is a continuous pressure filter designed for thin cake filtration with cake depths from 6 mm to 150 mm.' The slowly rotating drum (6-60 rph) is divided into segments (called cells) each with their own filter media (synthetic cloth or single or multilayer metal) and outlet for filtrate or gas. The outlets are manifolded internally to a service/control head where each stream can be directed to a specific plant piping scheme or collection tank. In this way, the mother liquor can be kept separate from the subsequent washing filtrates and drying gases. This allows for better process control as well as reuse and recovery of solvents and the gases.

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