Leveraging Automation to Maximize Boiler Efficiencies

As a boiler ages, it will have reduced reliability, higher maintenance costs and lower performance. A control system upgrade can provide important benefits.

By Rich King, Rockwell Automation

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A carbon monoxide trim loop, used in conjunction with the oxygen analyzer, can also be used to correct the basic fuel/air ratio for combustion quality and incomplete combustion.  Carbon monoxide trim minimizes excess air while maintaining low stack CO emissions. It also provides additional process visibility and allows operators to respond quickly to needed changes in the fuel rate set point.

Automation Advantages
Upgrading a boiler with automated controls can help eliminate imbalances and upsets in system processes that impact plant operations and allow operators to be more responsive to changes. For example, by implementing an integrated control system connected to a high-speed communication network, manufacturers are able to extract data from control devices and quickly deliver it to high level business systems. This gives managers up-to-date information on fuel usage, peak demands and operational efficiency, allowing them to make quicker, more accurate decisions.

In addition, many plants have multiple boilers that are not the same size and don’t operate under the same load demands. By automating these multi-boiler systems and providing process information to managers, plants can better coordinate production and increase the operational efficiency and availability of the units. More specifically, the automated sequencing and load modulation capabilities of the control system allow plants to reduce fuel consumption while maintaining the same level of production.

One of the biggest benefits of a control system upgrade is the potential to significantly reduce operation and maintenance costs. With manual controls, boilers must be staffed by operators around the clock to monitor the system and respond to problems. Through the use of automated controls, pager systems can notify designated operators of triggered alarms. This allows plants to redeploy workers to perform other tasks and use their resources more efficiently. 

Automation also gives manufacturers greater flexibility in how they meet their steam requirements. Many plants need the majority of their energy for first shift, which results in a huge increase in steam requirements to run their processes. Today’s advanced automation systems include microprocessor controls that anticipate heating load demand by calculating rate of change of system temperature or pressure, plus they can provide adjustable reset points for setback. As a result, boilers no longer need to run continuously to maintain constant steam header pressure during non-peak times. This gives users greater scheduling flexibility and allows them anticipatory response to steam demand changes.

Another key advantage of boiler automation is demand-load management. One of the primary goals in operating a boiler plant is to ensure that the working steam pressure is sustainable for any load demand placed on the plant. The purpose of demand-load scheduling is to distribute the steam demand in an optimized manner and to adjust the boiler plant output to meet working requirements. This helps ensure that boilers are fired only when needed and allows the system to use the best distribution of load between the boilers, resulting in the lowest overall cost.
 

Important Upgrade Considerations
When upgrading boiler controls, it’s important not to overlook the value of effective diagnostics and alarm capabilities. The sophisticated graphical and visualization capabilities of today’s human machine interfaces typically found with burner management/flame supervision systems help increase process uptime by reducing the amount of time necessary to identify process faults and system failures. With fewer veteran boiler operators in the workforce, the detailed diagnostics and alarm messages help less experienced operators to quickly identify oversights, while providing more access to information for more effective troubleshooting. 

The addition of variable frequency drives is another technique that can help improve the performance and efficiency of the boiler process. Rather than relying on dampers and louvers to control the airflow through the fan, using variable frequency drives allows “trimming” of fan speed to exactly match field conditions. This helps reduce the air and electrical energy needed to operate the boiler and eliminates the need for fan over sizing, damper “short-stroking” or linkage requirements.

Companies can maximize their return on investment in their upgrade project by using automation technology that is scalable and compatible with other parts of their plant. For example, by implementing standard, off-the-shelf hardware that is similar to other technology already employed elsewhere in the plant, companies can minimize their maintenance, training and inventory costs and leverage the investment they may have already incurred in these areas.

In any boiler upgrade project, it can be valuable to look into the future and carefully consider all potential needs and operational requirements, including changes in regulatory standards, communication needs, and fuel usage issues. For example, with more complex solutions, it’s important to take into account the potential additional expenses associated with maintaining more sophisticated devices or instrumentation, such as ongoing testing and calibration. Therefore, companies should secure in-house or outside expertise to handle this task and factor this expense into the project’s long-term cost.

Finally, it’s important to work with an experienced boiler system consultant to review the efficiency and condition of your existing unit. This includes performing a comprehensive evaluation of your boiler room requirements, including boiler size, load characteristics, backup requirements, fuel type, control requirements and emission requirements.  

In the end, the time spent evaluating the potential savings in fuel, maintenance and boiler efficiency will be well worth the effort. Incorporating high efficiency burner technology and high-performance controls will pay off every time your boiler is fired, for the entire life of the equipment.

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