Analyzing Automation

Since the time most biomass and waste-to-energy plants were built—in the U.S., in the late 1970s and ‘80s—the basic concept has remained: fuel is combusted in the facility’s boilers, and the resulting high-pressure steam drives a turbine to create electricity that powers homes, businesses or is used on-site. 

A closer look, however, will reveal technological sophistication that has allowed both aging and new plants to adapt or compete in an evolving energy landscape through increased energy efficiency and plant availability, reduced maintenance costs, improved operator effectiveness, and lower lifecycle costs.

Juha-Pekka Jalkanen, responsible for Valmet Energy’s process and marine automation business, has been in the industry long enough to witness the evolution of plant automation technologies. Jalkanen graduated from Helsinki University of Technology in Finland with a master’s degree in energy technology, environmental protection technologies and control engineering and has worked in a wide range of disciplines in the power industry. He joined the Valmet team in 2003, he says, and since then has been responsible for advance process control and reporting solutions for power generation controls, including various boiler technologies, steam and gas turbine controls and balance of plant automation. Valmet’s DNA system—a process automation and information management platform—combines all controls into a single platform and is used widely in power plants, the paper industry and on cruise ships, according to Jalkanen. “It’s impossible to think about a modern power plant without an automation system,” he says.  “In a nutshell, it’s needed to monitor, safely control and report the process.”

The automation system, or more precisely, the distributed control system (DCS) is the “brain and central nervous system of the plant and ensures reliable and predictable plant operation for maximum performance,” says Dieter Fluck, Siemens Energy vice president of global technology and engineering. “The DCS is designed to operate processes in a plant without the permanent interaction of people on-site. It collects all relevant data, and monitors and controls the plant.”

Beyond the general purposes of an automation system, one is only as good as the programs and logic programmed within it, according to Jalkanen.

Basic, Evolving and Crucial Roles
Importantly, the automation user interface should be easy to learn, Jalkanen says, as well as intuitive, and it should support efficient trouble shooting in order to quickly address reliability issues in the case of an upset or boiler trip. “For biomass plants, modern control tools allow for automatic adjustments not only for load changes, but also fuel quality changes and fuel feed upsets,” he says. “Operators need timely alarms to indicate abnormal conditions, and good trending functions to ascertain that any given process is operating within acceptable parameters.”

From an automation perspective, biomass plants operate with limited personnel, Jalkanen says, and over time, the task of the automation system has evolved from transmitting control and feedback signals between operator and field equipment to intuitive process control, advanced diagnostics, automatic optimization response and enhanced reporting functions.  “The job of training new operators and ease of use has also evolved, allowing the use of remote monitoring from tablets and cell phone platforms that support staffing requirement changes,” he says.

In today’s energy landscape, the power generation industry faces challenges, and biomass plants must adapt to remain competitive with other energy sources. “There’s even more of a need to focus on increasing power plant performance, including maximizing commercial availability of the plants,” Fluck says. “Solar or wind enforces the need to operate power plants more flexibly for adaptation to volatile market demand, and the DCS should ensure optimal operation of the plant processes.”

Due to the volatile market demands, according to Fluck, load changes have become more and more frequent. “These frequent load changes can be optimized, and changes can be engineered online with Siemens’s SPPA-T3000 control system, in order to ensure flexible adaptions to market needs during operations,” he says. “For biomass plants, the DCS has to handle strong variations and fluctuations in the fuel’s energy content. Stabilizing steam and power production, increasing efficiency and reduction of the manual interventions of the operational staff are crucial tasks to the DCS.”

The operator’s effectiveness and efficiency are crucial to the performance of the entire plant, Fluck adds. “The reliability and predictability of the entire power plant’s operation depend heavily on the operator’s ability to do the right things right.  A control system should be precisely geared to the tasks of control room operators, with a modern and intuitive user interface that provides relevant information and gives direct access to the essential functions.”

Reliability aside, the application automation is only as intelligent as the weakest control loop or logic that’s been programmed in it, Jalkanen says. “Our experience in the most challenging cogeneration environment—pulp and paper mills—has greatly influenced our concepts to control boiler load during load demand changes or fuel feed and quality disturbances. We have also found integration of steam turbine controls to the DCS very powerful in biomass combustion. For example, during severe fuel disturbances, we can manage the combination of boiler and turbine as a one functioning unit, creating a disturbance response that saves the entire power plant from a total trip.

Fluck and Jalkanen emphasize the significant automation advancements made over the past 20-plus years. “Artificial intelligence tools were available 20 years ago, however, remote work capability and industrial internet is significantly better today,” Jalkanen says.

Advancements, Trends, Challenges
Today, plants are operated with minimum personnel, and whole processes are designed from the start to be operated by single operator, or even remotely, Jalkanen says. “Powerful process stations enable more user friendly and intuitive operating interfaces and control solutions that, 10 years ago, needed separate process stations. Control technologies available now wouldn’t increase the number of process stations.” 

In the past, Fluck says, several operators in one control room were required to run a whole plant and its power plant operation. While central control rooms are a solution when there is a lack of experienced personnel or plants running below capacity to the extent that around-the-clock staffing isn’t viable, they only make sense if they are more than just multiple control desks for different plants in one single room, according to Fluck. And, operators must be able to control a whole group of different plants with heterogeneous control systems as if they were physically on-site. “The whole concept is only economically feasible if the underlying control systems don’t need to be modified or replaced, and the existing communication infrastructure can be used,” he says.

As for industry trends, the power market has been moving toward smaller power generation units, Fluck says, and for small, distributed and mostly unmanned systems like biomass and bioenergy plants, it’s crucial to ensure equipment is running smoothly and can be serviced from a central location, or even operated and monitored remotely. “The SPPA-T3000 is a very scalable DCS, not only for large-scale plants with tens of thousands of signals, but it can be scaled down to meet the needs of the different plant sizes, including smaller systems like biomass plants,” he says.

Being able to solve problems at any hour of the day is crucial for the availability of bioenergy and multifuel plants, as their energy production is twice as expensive compared to coal fired power plants, Fluck points out. “The reliability and predictability of power plant operations greatly depend on the control room operator’s ability to take the right action at the right time,” he says.

And in the modern day of cyber-attacks, risks of being affected increases each day. “This risk is dramatically higher if a system is not protected, or if protection is not updated regularly,” Fluck says. “Patch management ensures efficient online security patch installation to all the applicable components, which reduces the accidental risk of producing security gaps due to the unpatched system components. “The SPPA-T3000’s built-in redundancy minimizes the effort for future updates and upgrades, as well as for the deployment of security patches.”

Finally, many shutdowns and slow-downs are caused by people, and today’s automation technology has significantly reduced humor error. “The power plant’s output is formed by thousands of sensors and signals, motors and pumps, drives and fans,” Fluck says. “The daily responsibility of the operator is to monitor and control, readjust, and correct any issues in all of these components. Smooth periods spent working through the various required tasks can suddenly be interrupted by periods of hectic activity to counter disturbances in the plant’s operation or failures of the plant equipment. In these situations, operators need to focus on what really matters. They need less raw, unfiltered information. Information floods, unfiltered messages, alerts or inappropriate analysis reporting simply complicate the ability to adequately respond to a plant disturbance.”

At biomass and bioenergy plants, typical operator error situations relate to slow or delayed processes, such as managing bed temperature during fuel quality change, Jalkanen says. “For one project, the operators tended to push the boiler past operating limits and ended up burning bag filter elements,” he says. “We solved that with load maximization control guiding the boiler right to the edge, but not over. Many of our solutions eliminate human error by automatically reacting to severe disturbances or limiting controls to design limits—for example, when an operator wouldn’t be fast enough to react to a fuel feed disturbance, but Valmet’s load allocation solution would distribute the load request automatically to remaining fuel lines, carefully managing not to exceed maximum amounts these lines could exceed or sustain.” 

 An ideal DCS enables the operator to deal with unexpected challenges, Fluck adds. “The operator’s ability to function in an appropriate manner is supported by a control system that delivers the right information, in the right manner, at the right time.”

Author: Anna Simet
Editor, Biomass Magazine
701-738-4961
[email protected]

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Smart Bulk Handling Breakthroughs
When Martin Engineering was founded in 1944, it set out to become a global innovator in the bulk material handling industry by developing new solutions to common problems while improving safety and productivity.  A quarter of a century later, the company’s products, sales, service and training are available through 19 factory-owned facilities worldwide, with 1,000-plus employees and wholly-owned business units in dozens of countries. And, the company’s series of Foundations books is an internationally-recognized resource for safety, maintenance and operations training, with more than 20,000 print copies in circulation around the world. 

One of Martin Engineering’s latest innovations is its Martin N2 Position Indicator, which the company describes as a  “game-changer in the industry, with a positive impact on productivity, operating costs and safety.”

The device, used to measure the wear of a conveyor belt cleaner blade, wirelessly provides information to a plant operator or service technician. “Plant personnel no longer need to guess at how long the cleaner blade will last, or to physically visit the cleaner to check blade wear,” says Paul Harrison, chief technology officer at Martin Engineering. “So, for example, maintenance shutdowns for blade changes can be planned with much greater certainty. Optionally, knowing that a blade may not last until the next planned shutdown, an operator may decide to replace a blade before its useful surface is completely consumed, understanding that he would have had spillage otherwise because the blade would not have lasted until the next planned shutdown.”

Knowing when a blade requires changing means one does not have to have as many spares on hand just in case, Harrison says. “The potential for reduced carryback—because blades are tensioned and replaced at the right time—has significant cost savings attached to it. These productivity gains lead to lowered operating costs.”

Eliminating the need for blade inspection reduces the time maintenance staff need to spend near the conveyor.  “To be hurt by a conveyor, one needs to be near a conveyor," Harrison says. "The only time access is needed is during bladeretensioning or replacement.”

 In another move toward “smarter” material handling, Martin has introduced an automated pneumatic tensioning system for belt cleaners. “The N2 Twist Tensioner does everything the N2 PI does, but also maintains the tension on the blade, enhancing the game-changer benefits of the N2 PI,” Harrison says. “The benefit of automated or powered tensioning is increased data output for greater predictability, more precise and consistent tensioning, reduced wear and reduced labor for daily monitoring and periodic adjustment.”

Equipped with sensors that confirm the belt is loaded and running, the system automatically backs the blade away during stoppages or when the conveyor is running empty, minimizing unnecessary wear to both the belt and cleaner blade, Harrison adds. “The result is consistently correct blade tension with reduced power demand on startup, all managed without operator intervention.”

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