Reducing Steam Consumption & Flaring Through Advanced Process Control (APC)

In the oil, gas, and petrochemical industries, excessive steam consumption and unnecessary flaring are often accepted as the unavoidable "cost of doing business." However, in an era of tightening environmental regulations and fluctuating energy costs, these losses represent a massive opportunity for reducing steam consumption in petrochemical plants and minimizing flaring events in oil and gas operations.

From a process control engineer's perspective, high energy bills and frequent flaring events are rarely caused by process design limitations. Instead, they are usually symptoms of poorly tuned control loops, valve mechanical issues, and a lack of adequate advanced process control strategies.

At PiControl Solutions, we don't believe in installing expensive "black box" software on top of an unstable process. Our philosophy is simple: First stabilize the Base Layer, then optimize using APC for maximum process energy efficiency.

Here is how specific advanced process control techniques directly impact the reduction of energy waste and emissions.

1. Process Stabilization & The Hidden Killer: Valve Stiction

Why do operators keep process parameters far away from constraints? Because they fear instability.

When a control valve suffers from stiction/friction that prevents smooth movement, the reflux or temperature control loop enters limit-cycle oscillation. Facing these oscillations and fearing off-spec product, operators typically increase reflux "just to be safe", which temporarily improves separation but raises reboiler steam duty. However, because the stiction persists, the operator leaves reflux elevated and does not return it to the optimal setpoint. The result: the column runs at permanently higher reflux and steam consumption than necessary. This is a classic example of how valve stiction drives hidden energy waste: the mechanical fault (stiction) is never visible on a sensor, but its consequence: operator over-control is visible in unnecessarily high energy bills.

But what causes the oscillation? Often, it is not the tuning, but the control valve itself.

A significant percentage of industrial control valves suffer from Stiction (Static Friction). The valve gets stuck, pressure builds up, the valve suddenly jumps (slip-stick), and the controller overcompensates. This creates a permanent "Limit Cycle": a critical factor in valve stiction process control and energy waste.

The Solution: Before we even touch APC, we use PITOPS to perform valve stiction diagnostics, and optimize PID loops based on identified valve stiction. By identifying process dynamics (Deadtime, Gain, Time Constant) and mathematically proving valve stiction, we can either mechanically fix the valve problem, or tune it more precisely based on the amount of valve stiction. This represents the foundation of process stabilization and efficient process control optimization.

The Payoff: When you eliminate oscillation and reduce the standard deviation of a process variable, you earn the "license" to move the setpoint closer to the optimal limit. Reducing the "safety cushion" on a steam header by just 2 PSI can save thousands in fuel costs, which is a direct path to industrial energy savings.

2. Feedforward Control: Reacting Before the Flare Pops

One of the main causes of flaring is sudden process disturbances that feedback (PID) controllers are too slow to catch. This is where feedforward control strategies, and how feedforward APC prevents flaring, in petrochemical plants becomes critical.

Imagine a scenario where a sudden change in feed composition or flow enters a column. By the time the temperature controller at the bottom of the column notices the change and reacts, the disturbance has already traveled through the system, pressure has spiked, and gas has been sent to the flare for safety.

By implementing Feedforward APC models, the system detects the change at the inlet (the disturbance variable) and proactively adjusts the steam valve before the disturbance impacts key parameters. This feedforward control approach is essential for reducing energy consumption.

Real-world application: In a cooling water system failure, a sudden loss of condenser cooling would cause rapid pressure rise and flaring. An APC feedforward control model detects the drop in cooling water flow rate or temperature at the inlet and immediately reduces heat input (steam), preventing pressure spike and subsequent safety shutdown. This rapid detection and correction is essential because a PID controller alone cannot react fast enough to prevent the column from overshooting setpoint.

3. Decoupling Interactions to Stop the "Control Fight"

In complex units, control loops often fight against each other. A change in reflux affects temperature, which affects pressure, which in turn affects level. These interactions lead to cyclic behavior and energy waste.

We utilize Decoupling APC strategies that allow for the independent control of key variables. When interactions are mathematically compensated for using decoupling control loops, the process can run at the point of maximum efficiency (lowest Specific Energy Consumption) without the loops "chasing" each other. This is the essence of constraint control for energy efficiency and APC for distillation column energy optimization.

4. Constraint Control: Riding the "Flooding" Limit

This is the core of APC value and constraint control APC implementation. The goal is to "drive" the plant right at the edge of its mechanical and process constraints.

In Distillation, the ultimate constraint is often column flooding. Operators will typically run the column at 80% capacity to stay safe. An APC controller monitors the differential pressure (dP) across the trays: the leading indicator of flooding. It can push the throughput up to 95-98% of the flood limit, automatically backing off if the dP rises too high. This maximizes throughput per ton of steam used: a direct application of constraint control for maximizing distillation throughput with minimal steam usage.

Similarly, in Compressor Systems, APC optimization for compressors can manipulate speed or IGVs (Inlet Guide Vanes) to maintain suction pressure exactly at the limit before the recirculation (anti-surge) valve opens. Every minute that a recycle valve is closed is money saved, exemplifying reducing recycle and flaring using APC.

5. Combustion Control: The O₂ Trim Advantage

For the power house and boilers, efficiency comes down to the fuel-to-air ratio and combustion control optimization.

Too little air: You risk incomplete combustion and safety hazards.

Too much air: You are wasting fuel to heat up nitrogen and oxygen that is just going out the stack.

Advanced Cross-Limiting combustion control combined with O₂ Trim ensures the boiler operates with the absolute minimum "Excess Air" required for complete combustion. This represents combustion control with O₂ trim for boiler efficiency and is the key to boiler efficiency improvement with O₂ trim. The APC dynamically adjusts the air damper based on the O₂ analyzer in the stack, ensuring you aren't paying to heat the sky. The benefits of cross-limiting combustion control include superior efficiency and reduced emissions, contributing to how APC reduces emissions in refineries.

Conclusion: An Investment That Pays for Itself

Reducing steam consumption by just 3-5% and eliminating routine flaring can yield savings ranging from hundreds of thousands to millions of dollars annually, depending on the plant size. Energy savings through process stabilization is not theoretical, it's quantifiable.

At PiControl Solutions, our approach is based on transparent models, robust PID tuning, and practical engineering know-how. You don't always need to reconstruct the entire plant to become energy efficient. Often, the intelligence in the control room (DCS/PLC) is what makes the difference. Our case studies of APC applications in compressors, distillation, and boilers demonstrate consistent results across diverse operations.

If you want to analyze your steam systems or flaring issues using advanced process control techniques for reducing steam consumption and flaring, contact us. Sometimes, the solution is just a few parameters away.