Process control systems and methods for use with filters and filtration processes

What is this patent about?

’397 is related to the field of biopharmaceutical downstream processing, specifically the integration and control of tangential flow filtration (TFF) within a continuous or connected purification train. In protein production, unit operations like chromatography and viral filtration typically run at constant flow rates, whereas ultrafiltration naturally experiences a decline in permeate flux as the product concentrates. This mismatch traditionally requires large intermediate pool tanks to decouple the steps, which increases the facility footprint and risks product degradation during hold times.

The underlying idea behind ’397 is to synchronize the variable hydraulic performance of a filtration unit with the steady-state requirements of upstream purification steps through active feedback control. By monitoring the permeate flow rate in real-time, the system can dynamically adjust either the upstream supply or the filtration parameters—such as feed crossflow and transmembrane pressure—to maintain a balanced mass flow. This insight allows for the replacement of massive storage vessels with small surge tanks, enabling a truly connected process where fluid moves seamlessly from purification to final formulation.

The claims of ’397 focus on a process control system and method that links upstream processing units to a downstream TFF loop via a feedback loop based on permeate flow sensing. The independent claims cover four specific control architectures: (i) modulating upstream flow to match filtration flux, (ii) adjusting the TFF feed pump to force the permeate flux to match a constant upstream flow, (iii) a tiered approach that switches from pump control to upstream flow control at a limit, and (iv) a hybrid mode that allows tank volume to fluctuate once a pump threshold is reached.

In practice, the invention overcomes the concentration polarization effect, where a boundary layer of protein builds up on the membrane and slows down filtration. Instead of allowing this to stall the process, the control system uses a Constant Flow Strategy by ramping up the feed pump’s crossflow rate as the protein concentration rises. This increases the mass transfer coefficient, effectively 'pushing' the permeate through at a steady rate that matches the output of the preceding chromatography columns, thereby keeping the retentate tank level stable.

This approach differs from prior solutions by eliminating the need for discrete batch processing and the associated large-scale infrastructure. Traditional systems treat ultrafiltration as a standalone end-step, but this invention treats it as a dynamic component of a connected downstream process. By utilizing the stagnant film model to predict and counteract flux decline, the system achieves high-concentration formulation without the flow disparities that previously made continuous bioprocessing difficult to implement at scale.