Description
Operating above the solvent boiling point under BPR-controlled pressure is one of the most exploited advantages of flow chemistry: reactions in ethanol at 150°C, water at 200°C, or DCM at 100°C become routine when the system pressure is elevated to 5–15 bar above the solvent vapour pressure. The BPR maintains this pressure at the reactor outlet, while a back-pressure-rated pump delivers the reagent stream at a delivery pressure higher than the setpoint — the net flow through the BPR is determined by the difference between the pump delivery pressure and the BPR setpoint.
BPR designs used in flow chemistry include: spring-loaded disc valves (simple, reliable, but fixed setpoint per spring), pneumatically actuated dome-loaded BPRs (variable setpoint 0–350 bar set by nitrogen reference pressure — the most versatile and widely used), and electronically actuated needle valve BPRs (motor-driven valve with setpoint programmed digitally — enables pressure ramping and programming within the flow chemistry control software). For gas–liquid flow systems (e.g., H₂/organic in hydrogenation), the BPR must handle two-phase flow without sticking or cavitation — specialised gas–liquid BPR designs use enlarged orifice areas and corrosion-resistant seats to ensure reliable operation. Wetted materials are specified for process chemistry compatibility: PEEK, PTFE, and Hastelloy C-276 for acidic, basic, or halogenated streams.
Key Features
- True mass flow control — independent of upstream pressure variation
- Integrated leak test and auto-close valve on overpressure
- Multi-gas programmable — single unit covers H₂, N₂, CO₂, CO, and more
- Fast response (<0.5 s) for dynamic flow profiling in reaction optimisation
- Corrosive gas wetted materials for HCl, Cl₂, HF, and SO₂ service
- Electropolished internals for semiconductor and pharma purity requirements
- Coriolis designs for highest accuracy at pilot and production scale
- Fully integrated with flow chemistry control platforms via digital bus
Technical Specifications
| BPR Types | Spring-loaded disc, dome-loaded (N₂ reference), electronic needle valve |
| Pressure Range | 0.5 bar to 350 bar (design dependent) |
| Setpoint Accuracy | ±0.05 bar (dome-loaded); ±0.1 bar (spring-loaded) |
| Flow Rate Range | 0.1 mL/min to 5 L/min (lab–pilot scale) |
| Wetted Materials | PEEK, PTFE, Hastelloy C-276, SS 316L, gold-plated seats |
| Process Media | Single-phase liquid, gas–liquid (two-phase), supercritical CO₂ |
| Temperature Range | −20°C to +200°C (standard); up to +300°C (high-T designs) |
| Control Interface | Manual (dome), analogue 4–20 mA (electronic), digital Modbus |
| Certifications | CE/PED compliant; ATEX variants available |
| Special Types | Two-phase gas–liquid BPR; scCO₂-rated BPR; high-T BPR |
Industrial Applications
- H₂ delivery for continuous catalytic hydrogenation in tubular or loop reactors
- O₂ / air metering for aerobic oxidation reactions
- CO delivery for carbonylation and hydroformylation synthesis routes
- CO₂ metering for continuous supercritical CO₂ reactions or carboxylation
- HCl gas metering for continuous hydrochlorination reactions
- Ozone metering for ozonolysis continuous flow sequences
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