In a pulp mill, the inlet temperature to the oxygen de-lignification tower must be kept constant to ensure consistent bleaching of the pulp stock for a given application of bleaching chemical—in this case, oxygen.

The temperature target is determined by the process designer, but small fluctuations in control loop setpoint are up to operator discretion. Setting the temperature up a few degrees can save bleaching chemical, while setting it down a few degrees can save steam.

The pulp mill operation manager knows exactly how much bleaching chemicals cost, but the impact of steam is not as “real.” Even if there are internal charges from the powerhouse, they are typically done monthly and do not address incremental costs. The impact of operating temporarily away from the design inlet temperature is not readily apparent.

When the plant implemented Energy Advisor, the trade-off between bleaching chemicals and steam became apparent in real time.

It turned out that changing the temperature by even 2° Celsius could impact energy costs by $60 per hour when the incremental steam is generated by firing natural gas. The savings in bleaching chemicals by increasing inlet temperature can be completely eclipsed by the cost of steam, depending upon the fuel!

Facilities with large AC motors often must use banks of capacitors to keep the plant power factor closer to unity. These capacitor banks are typically turned on and off manually— rarely is the power factor controlled automatically.

A process facility using Energy Advisor had difficulty coming up with a single equation to develop the electrical target calculation. The dynamic gain of electric use vs. production rate was constant, but the offset (which represents the base electrical use with the plant down) seemed to differ depending upon the data set selected for analysis.

The process engineer thought the bias value should always be constant. How can the base level electrical use change from day to day?

He shared his finding with the operators, who pointed him to the capacitor banks used to adjust the power factor in the plant. They should only be switched on if the plant’s big motors are running, but with all that is going on when things are shut down, sometimes the operators would neglect to switch off the capacitor banks. No wonder the base level electrical use seemed to change from day to day!

Energy Advisor now acts as a not-so-subtle reminder to those operators. When energy use is above target, they look to see if any capacitor banks can be switched off. Without that real-time insight, the extra energy consumed due to excessive power factor correction is out of sight and out of mind.

The layout of many petrochemical facilities requires the transfer of product and/or utility streams between units. Often, the impact of heat loss due to changes in ambient temperature is overlooked.

A facility in a northern climate used Energy Advisor to create the calculations for steam usage in a blending process. The process engineer discovered that ambient temperature had a surprisingly high gain factor on the resulting equation.

A bit more digging revealed that the temperature drop on the product stream could be as high as 12° Celsius.

This information provided clear justification to upgrade the pipe insulation and to understand how to prioritize this project against other cost-saving initiatives.

In Kraft pulping facility, the recovery boiler is used to process “black liquor” to recover the pulping chemicals and produce steam as a byproduct. Most pulping facilities also have a biomass boiler, and it is not unusual to operate for extended periods of time without having to fire auxiliary fuels such as natural gas or oil.

Although it is generally known that recovery boilers are more efficient than biomass boilers, the operating procedures for firing the auxiliary fuel may not reflect that knowledge.

Energy Advisor helped one facility truly understand the cost of firing natural gas on the biomass boiler instead of the recovery boiler when the process engineer found the gain factor on the recovery boiler to be twice that of the biomass boiler. Energy Advisor predicted twice as much steam from the same amount of natural gas when that gas was fired in the recovery boiler!

There are still legitimate process reasons to fire natural gas in the biomass boiler, but this facility is re-working their SOPs to favor use of natural gas in the more efficient unit, with immediate savings as a result.

Keeping a constant vacuum on a condensing unit is critical for operation within chemical processing facilities.

Losing the vacuum can mean not only the loss of condensate, but can cause a cascade effect, tripping multiple units.

One facility lowered the risk of this catastrophic event by running five vacuum pumps simultaneously. But during a maintenance window with only three pumps running, the true cost of running all five pumps (when three can do the job) could easily be determined.

Energy Advisor was used to quantify that significant savings could be had by even shutting down one pump. The new SOP is to have one spare pump online and one offline with immediate savings as a result.

The steam systems in an industrial facility can be quite complex, with multiple headers, let-down stations, boilers, and steam turbine generators used to balance generation and consumption.

And while steam vent valves often open to relieve pressure during process upsets, it’s neither desirable nor typical to have them open all the time. If a steam vent cannot be closed without the header over-pressurizing, then something is out of balance. But what?

This problem was costing a refinery in the Middle East several thousand dollars a day. As the problem occurred following a major controls upgrade, everyone blamed the controls.

But the culprits were actually mechanical failures: a failed check valve on the de-aerator receiver and a partially open let-down valve. Both failures caused steam to escape into the low pressure header, causing an imbalance. The purpose of the de-aerator check valve was to allow steam to flow only out of the header, so the impact of the failure was major.

Without the visibility provided by real-time energy monitoring, this problem went undiagnosed for several months, costing the facility many times the investment of an energy management information system.