PITOPS
Closed-loop PID tuning software that identifies process models from normal operating data, so column pressure, reflux, and level loops on the ASU can be retuned without step tests that risk product purity.
FocusNo step tests required
Air SeparationProcess Control Software for Air Separation: PID Tuning, APC, and Loop Monitoring
Process control software for air separation optimizes PID tuning, modular advanced process control, and control loop monitoring across cryogenic distillation columns, main heat exchangers, and compression and expansion trains. Every ASU balances purity, energy, and product demand differently, from a nitrogen-only membrane skid to a full gas-and-liquid cryogenic train with argon recovery, so it needs control strategies matched to that configuration rather than plant-wide defaults.
The approach
How It Fits Your Air Separation Unit
No rip-and-replace
An Optimization Layer
PiControl Solutions builds this software as an optimization layer that sits above an air separation unit's installed DCS or PLC hardware, whether the plant runs a cryogenic column train, a PSA/VSA skid, or a membrane system.
Underperforming loops, fixed
Finds & Retunes Loops
It finds underperforming loops on column pressure, heat exchanger delta-T, and product purity, then retunes them against real closed-loop operating data instead of disruptive bump tests.
Built to last
Keeps Models Accurate
It keeps modular MPC models accurate as ambient conditions, feed air composition, and product demand shift, so the control assets already in the plant deliver the performance they were specified for.
The challenges
Control Challenges Specific to Air Separation
Air separation control loops face conditions that generic tuning rarely handles well, because cryogenic distillation couples tightly to heat exchanger duty and product purity has almost no margin for error. PID controllers account for over 95% of all control loops in industrial plants, so tightening these loops is where ASU variability is won or lost.
Cryogenic distillation
Column–Exchanger Coupling
Cryogenic separation liquefies air and then distills nitrogen, oxygen, and argon at their boiling points, which means column pressure and reflux loops are tightly integrated with the main heat exchanger. A move on one loop shows up as a disturbance on the other within minutes.
Main heat exchanger
Warm/Cold End Delta-T Drift
Efficient plants hold warm end delta temperature (WEDT) and cold end delta temperature (CEDT) inside a narrow band. Air compressor loading and expansion turbine duty both push on that band, and loops tuned for one ambient condition drift as inlet temperature swings.
Nitrogen, oxygen, argon
Purity and Argon Recovery
Nitrogen, oxygen, and argon purity loops leave almost no room for off-spec product before a batch is downgraded or vented. Argon recovery adds a side column drawing off a small, economically valuable stream that is especially sensitive to upstream disturbances.
Pipeline and liquid inventory
Demand-Driven Throughput Swings
Gas product line demand, liquid inventory levels, and real-time electricity contracts all push the plant to modulate throughput quickly. Loops that cannot follow that pace lose product to venting or fail to protect minimum liquefier suction pressure.
Read more on air separation process control challenges.
The software
Software Matched to Air Separation Applications
Three PiControl products carry most air separation optimization work, and each targets a different stage of the control problem.
Swipe
COLUMBO
Handles closed-loop MPC model identification for a compact, modular PLC-based multivariable controller, refreshing the models behind purity, throughput, and energy optimization as feed air and demand conditions drift.
FocusCompact PLC-based MPC
APROMON
Provides continuous control loop monitoring, flagging oscillation, valve stiction, and purity-loop degradation across the ASU before they cause a downgraded batch or an unplanned vent.
FocusCatches degradation early
Compatible with every major DCS and PLC via OPC-DA and OPC-UA, these products read live data from the control assets already installed, so no new control hardware is needed. They form the air separation slice of PiControl's process control software range.
Services
Consulting and Training for Air Separation Teams
Process optimization software depends on two things in air separation: experienced engineers to apply it, and plant teams who can sustain the gains.
Step 01 · Optimization
PID Tuning Consulting
PiControl's PID tuning consulting deploys PITOPS and SUPERTUNE directly on ASU loops, typically covers every base-level column, exchanger, and compressor loop on the unit, and documents before-and-after results.
FAQ
Air Separation Process Control FAQ
To see how the same optimization layer applies in other sectors, explore process control software by industry.
Process control for air separation plants is the practice of holding cryogenic distillation columns, main heat exchangers, and compression trains at safe, on-spec operating points using PID and advanced controllers. Process control software improves it by tuning those controllers against real operating data, which cuts oscillation, protects product purity, and lets the plant run closer to its true energy and throughput constraints.
Advanced process control manipulates the setpoints of the base-level PID loops underneath it, so if those loops are poorly tuned, the APC layer inherits that error and cannot hold its targets. Base-level PID tuning and optimization is the prerequisite step on every air separation unit, and it commonly cuts oscillation amplitude while roughly doubling or tripling usable controller action before any APC work begins.
Because most air separation plants are smaller than refinery or olefins units, a compact, modular PLC-based MPC typically fits better than a large host-based MPC package, and it installs faster and at lower cost. On ASUs producing both gas and liquid product, this approach has delivered on the order of a 4 percent increase in profit; on smaller gas-only plants it has delivered 1 to 2 percent energy savings through reduced venting.
Yes. The software reads and writes through OPC, so it is compatible with every major DCS and PLC via OPC-DA and OPC-UA. It runs as an optimization layer on top of the control assets already installed on the ASU, which means no rip-and-replace and no new control hardware to justify.