Understanding the Awesome Utility of Buffalo Extraction Systems’ Active and Linear Servo-Controlled Linear Back Pressure Regulator


Precise Pressure Control With Active Back Pressure Regulation (BPR) Using Servo-Actuated Pin Valves

How Crucial is Precise Pressure Management in Supercritical Fluid Extraction (SCFE)?

Supercritical fluid extraction (SCFE) draws out different ingredients from the raw material at different process pressures. This is because any change in pressure varies the supercritical solvent’s solubility [1].

Among the factors that position SCFE miles ahead of other extraction methods is its prized capacity to extract the required ingredients in their authentic, pure form. But then, only impeccable pressure management can enable such fantastic selectivity [2].

The point is, the importance of correct pressure control in SCFE can never be overemphasized!

For example, take the case of SCFE of Euterpe oleracea, which is commonly known as Acai Palm, Acai, or Assai Palm. At a certain process pressure, SCFE separates anthocyanin from the pulp, while extricating phenolic phytochemicals at another pressure [2].

What remains unchanged is the importance of maintaining the correct process pressure for the specific ingredient.


Buffalo Extraction Systems’ Active, Linear Servo-controlled Back Pressure Regulator (BPR)

Buffalo Extraction Systems ensures targeted extraction via Carbon dioxide (CO2) SCFE by making and using its very own active, linear servo-controlled back pressure regulator. The device is in marked contrast to the passive back pressure regulators or the manually controlled ones generally utilized in the industry.

At the crux of precise process pressure control is the ability of the servo actuator to accurately manage the position of the pin valve by utilizing feedback from the extraction pressure. Not only does this mechanism control the pressure precisely, it also leaves the CO2 flow unaffected.


Back Pressure Regulator (BPR) For Supercritical Fluid Extraction
Back Pressure Regulator (BPR) For Supercritical Fluid Extraction


What happens as a consequence is that all the critical process parameters for a flawless extraction process are held exactly at the required levels. These crucial parameters are the flowrate, the extraction pressure, and the separation pressure.

Back pressure regulators (BPRs) are located at two positions in the CO2 SCFE process:

  1. Between the extractor and the separator.
  2. Between the separators 1 and 2.

Functions that BPRs serve in the process are as follows:

  • Maintaining correct extractor pressure.
  • Holding separator pressure at the correct level.
  • Ensuring steady state conditions by leaving the CO2 flow rate unchanged.
  • Facilitate smooth pressure drop between extractors and separators.

Modulation of the pin position enables the BPR to maintain constant pressure at their upstream side [3]. By using a servo driven actuator, the response and corrections in the pin position for ensuring consistent pressure regulation are quick and precise. Correct extractor pressure control is essential for separating the ingredient in its correct form as we have seen earlier.

Unlike pressure relief valves which flip flop between on and off positions [4], Buffalo Extraction Systems’ BPRs are tuned to provide pressure control under steady state conditions. These are conditions wherein the flow rate throughout the system does not change over time [5].


Back Pressure Regulator (BPR) For Supercritical Fluid Extraction
Back Pressure Regulator (BPR) For Supercritical Fluid Extraction


However, regulating pressure is only one of the two crucial functions that BPRs serve in the CO2 SCFE process. Their second function is to facilitate a seamless drop of CO2 pressure to the separator pressure level from the supercritical one at the extractor side [6].

Pressure drop is among the most pivotal of stages in the CO2 SCFE process. This is because temperature falls rapidly and causes ice formation. The ice so formed can block the BPR [7].

Such ice formation is a result of the Joules-Thompson Principle, which states that the temperature of a gas declines when pressure on the gas falls if the pressure drop occurs without:

  • any heat transfer; or
  • the gas performing any mechanical work [8].

To counter this, all Buffalo Extraction Systems’ BPRVs and downstream system temperatures are controlled and maintained at correct separation temperatures. Such accurate control avoids freezing and, thereby, facilitates smooth gas liquid separation.


Supercritical Fluid Extraction (SCFE) System
Supercritical Fluid Extraction (SCFE) System



By reinforcing the natural advantage of the CO2 SCFE process in isolating pure ingredients, Buffalo Extraction Systems’ BPR propels your plant from the present to the future of extraction.

Buffalo Extraction Systems created its very own Active Servo-controlled Back Pressure Regulator (BPR) after an exhaustive analysis of all requirements of the Carbon dioxide (CO2) Supercritical Fluid Extraction (SCFE) process.

Get in touch with us at info@buffaloextracts.com and get to know how the BPR makes your CO2 SCFE technically superior while optimizing all deliverables.



  1. Supercritical CO2: A Green Solvent, Chemical Engineering
  2. Solvent Supercritical Fluid Technologies to Extract Bioactive Compounds from Natural Sources: A Review, Kooi-Yeong Khaw, Marie-Odile Parat, Paul Nicholas Shaw, and James Robert Falconer
  3. Supercritical Fluid Extraction – A Review, G. N. Sapkale, S. M. Patil, U. S. Surwase and P. K. Bhatbhage
  4. Definition of Back Pressure Regulator, Equilibar
  5. Steady State Flow Fluids, Engineers Edge, LLC
  6. Supercritical Extraction – Batch Pressure Control, Equilibar
  7. Back Pressure Regulator (BPR), Waters
  8. Joule-Thomson Effect, Encyclopædia Britannica