Replacement Powder Mill for Pharmaceutical Client
Challenge from the Client
Our client’s new mill design experienced high temperatures inside the mill and was reaching its maximum set point before completion of the batch. The mill then required time to sufficiently cool to restart and finish the batch. This was an ongoing problem and retrofit solutions had been attempted by a number of other consultants prior to IPS being engaged.
Our Approach & Solution
IPS took information from the client’s prior remediation attempts and recommended a series of trials with the mill vendor to determine the temperature characteristics of the mill. IPS worked with the client to develop a series of trial protocols for tests to assess the impact of running the mill in open loop, closed loop, and starved configurations both with and without powder to determine the worst case condition.
The result of these trials indicated that heat was being generated inside the mill casing and was being stripped by the gas stream as a cooling medium, proving previous consultants’ theories to be insufficient. In open loop configuration the mill temperature reached thermally steady state within the desired operating parameters.
Following the assessment of these results IPS, in consultation with the mill vendor, proposed installing a heat exchanger on the mill gas recirculation loop. The trial results showed thermally steady state was achieved in open loop conditions with a 15°C temperature difference from the mill inlet to the mill outlet. The heat exchanger was sized to remove at least 15°C from the recirculating gas stream in each pass under closed loop conditions. This would have the effect of managing the mill in thermally similar conditions to the open loop state, but while in closed loop and nitrogen blanketed.
Further testing was carried out by the mill vendor using a trial heat exchanger which suggested that the heat exchanger was performing as expected and that cooling the air flow through the mill was having the desired effect of cooling the mill itself. IPS designed a small cooling loop using the clients existing equipment to operate the heat exchanger.
The client purchased and installed a new powder mill with a high degree of confidence that it would provide the desired outcome.