By Carl Hosier, Honeywell Process Solutions
In the manufacturing world, the word “retrofit” many times is feared to mean “lost production.” In other words, plants—or at least parts of plants—must be shut down for equipment to be upgraded. And idle machinery means less production.
Perhaps nowhere is this concept feared more than in the power-generation industry, where scheduling a forced outage means less electricity, steam or heat for the production plant. Nevertheless, equipment retrofit is largely becoming a necessary part of the job because power generation companies across the world are being tasked to meet the needs of an expanding global industrial base while keeping a cap on greenhouse gas (GHG) emissions, all with aging infrastructures. It’s easy to see how complicated the daily lives of these generators can become.
As the use of current fossil energy generation equipment is increased, so is the creation of GHG emissions. To combat this problem and address the standards set by governments to reduce GHG emissions, power companies are turning to advanced solutions and proven technology that permits GHG to be concentrated for removal later in the process. As some environmental groups oppose any process that burns fossil fuel, power producers are starting to look at clean coal and sequestration solutions for the future to reduce GHG, especially CO2.
Advancing the Process
Taking a cue from the world of advanced process control could prove to be a viable alternative for meeting government regulations on GHG emissions while increasing power, heat and steam output without a major process overhaul. Specifically, many manufacturing facilities in industries such as chemicals, refining and pulp and paper have begun integrating plant subsystems with their distributed control systems (DCS) to maximize productivity and improve overall efficiency. Applying this same concept to the world of power generation with the goal of reducing GHG emissions could well help electricity and steam generators streamline production in a way that makes sense both to their pocketbooks and their regulators.
To meet these emerging GHG regulations, power generation companies must retrofit their boilers, install new boilers or auxiliary systems to enhance production processes to drive further efficiencies. Retrofitting old boilers or installing new ones, though, can be problematic. This is because it is impractical to shut down an entire production facility when the demand for electricity continues to grow at various peak hours. By scheduling a forced outage, an entire power generation facility will bring production to a halt for its industrial customers; not an ideal scenario for the power company or the economy.
In all types of industrial power operations, a number of relatively fixed factors affect overall plant operations requiring effective optimization measures. These include boiler design, cooling water conditions, burner type, design steam conditions and environmental controls that capture and remove pollutants, and taking advantage of the latest proven technology. By optimizing the operation of a plant’s subsystems (taking into consideration these multiple parameters) an operator can improve the efficiency and utilization of his or her equipment, and also address environmental standards. This can be done with software instead of replacing or retrofitting major capital equipment.
This advanced energy efficiency software integrates functions ranging from combustion control and steam pressure control, to plant monitoring, plant performance optimization and tie-line control. The core of this approach integrates the technology with the plant’s existing DCS architecture, including field instruments, SCADA, plant historians and other advanced control functions such as simulation software and advanced process control and optimization applications. With these types of advanced energy solutions, power companies are able to centralize the control functions of their plants on modular software platforms.
Following are brief summaries of the functions that can be integrated using advanced energy solutions:
Advanced combustion control is used to improve the thermal efficiency of individual boilers and reduce emissions from industrial power generating facilities. Plant owners seek to minimize excess air and reduce NOX levels, and at the same time, maintain acceptable carbon monoxide (CO) levels. This approach also tightly coordinates control of furnace fuel-air ratio and optimizes multi-variable rate control. A combustion optimizer continuously evaluates measurement of flue gas components, observes given ranges, and calculates optimal air-fuel ratio. It is used to coordinate combustion air and fuel, including different dynamics for each channel, and maintain an effective ratio in the furnace. This improves combustion stability and reduces variations in flue gas emissions.
Using this type of approach not only saves on fuel for the same amount of generated energy, but also helps to reduce emissions to stipulated regulatory levels. Users are able to minimize heat loss in flue gas, reduce their fuel consumption and carbon dioxide footprint and reduce fouling/slagging/local hot spots.
An effective steam pressure control solution safeguards the full generation capacity of industrial power facilities. Stabilizing steam pressure and preventing boiler and turbine outages allows full use of predictions on steam consumption and ensures optimal response in transients. This guarantees continuous balance between produced and consumed steam controlling total heat input into boilers, as well as total steam flow into each header. In addition, it stabilizes steam pressure via “calm process control,” which extends asset life by minimizing wear and tear on equipment.
Performing economic load allocations for boilers (ELA-B) optimizes the utilization of steam for electricity generation and process or heating needs. This tool expands boiler house efficiency and flexibility by distributing total heat input amongst boilers and maintaining the widest effective steam production range, minimizing steam production costs. Load allocation is based on boiler cost curves, individual boiler limits, and specific operational restrictions.
Economic load allocation (ELA) controls for backpressure turbines, by coordinating total steam flow by process steam demand. It also ensures adequate space for optimization in turbine loading. Thus, users can maximize power generation efficiency while maintaining output steam flows and parameters determined by steam consumers.
Economic load allocation can also be done for condensing turbines (ELA-T). This allows precise control of the total generation set point in response to output steam demand and, as a result, minimizes steam consumption while maintaining total generated power and output steam flows and parameters.
Industrial power generators can reduce downtime and increase production through implementing plant performance monitoring tools. This improves decision-making by monitoring all key performance indicators (KPIs). Knowledge of KPIs allows plant personnel to address problems before they occur and helps ensure 100 percent availability of assets. Simultaneously, it validates potential opportunities for performance improvements.
A comprehensive monitoring solution includes a suite of thermodynamic and heat balance calculations based on ASME PTC codes. Evaluations typically include emissions; boiler mass and thermal balance; turbine mass and thermal balance; steam cycle; and boiler, turbine, condenser, cooling/tower, gas/steam air heater; and feed water heater efficiency. This can then serve as a robust operations surveillance tool for plant managers, enabling quick identification of efficiency weaknesses and supporting immediate measures to bring KPIs back on track. It can provide continuous emissions and cycle chemistry monitoring, as well as offline analysis. Likewise, the tool will enhance operations management by expediting the decision process for short-term production scheduling. Users realize additional value from process history data through computational output and automatic archiving of operational KPIs.
Tie-line control provides real-time optimization of power generation, and helps industrial operations to reduce the overall cost of power. This type of solution monitors power generation, external contractual commitments and internal consumption, and helps to predict the cumulative power supply required and consumption within a given period of time. It also optimizes the generation trajectory to meet the user’s external power quota.
Technology to help capture CO2 has advanced in the past couple of years. The latest proven technology with post combustion is with burners that concentrate the CO2 for easier removal later in the process for treatment or sequestration where feasible. While testing of these burners has been at controlled sites with small industrial boilers, the outcome has been very promising and will soon advance to testing on utility boilers.
Increased Visibility = Better Decisions
The main premise behind system integration and advanced process control is to provide plant or mill personnel the most relevant information to help them make decisions that ultimately keep the plant running safely, reliably, efficiently and within environmental constraints.
In power generation, using advanced energy control application solutions not only streamlines operations, it increases visibility for the operator across all subsystems. By giving plant operators the tools to accurately monitor the power generation process in real-time, they can quickly make informed decisions that significantly impact bottom-line performance.
Advanced energy solutions improve power generation efficiency at the boiler level and across the entire plant, so power companies no longer need to consider executing a major equipment refurbishment to reduce operating costs. The software applications, or a combination of software and proven technology hardware, provide industrial power generation facilities worldwide with a low-cost, high return alternative to major boiler retrofits to improve operational efficiency, while reducing GHG emissions to meet tomorrow’s industrial electricity needs. With the advent of “smart” devices for transmission and distribution, industrial and residential consumers, the demand cycle can be better predicted to reduce the requirements of older inefficient peaking units that no longer can be economically operated and meet the new GHG emission requirements.
Author: Carl Hosier is senior marketing leader, power generation for Honeywell Process Solutions.