Category: Blog

Turbine automation represents a significant leap forward in the operational efficiency, safety, and reliability of power generation systems. By integrating advanced control systems, turbines can operate with minimal human intervention, adapting in real-time to changing conditions to optimize performance. This article delves into the essence of turbine automation and examines the nuanced controls specific to the four principal types of turbines, shedding light on their unique requirements and the technological innovations driving their evolution.  

Turbine Automation

Turbine automation means the use of advanced control systems and computer-aided systems to monitor, control, and optimize the operation of turbines. The goal is to automate the processes that control the turbine’s speed, power output, and other critical operational parameters. Automated systems oversee critical parameters such as temperature, pressure, and flow rate, adjusting operations instantaneously to maintain optimal performance levels. This not only minimizes the need for manual intervention but also significantly improves the turbine’s efficiency and reliability.  By harnessing the power of automation, industries can ensure their turbines operate within optimal parameters, thereby reducing wear and tear and extending the lifespan of these critical assets.

Nuances of Turbine Control Systems

The intricacies of turbine control systems lie in their ability to ensure the seamless operation of turbines under varying conditions. Modern systems embody the convergence of mechanical engineering, electronics, and information technology.

Components of Control Systems

At the heart of turbine automation are several key components, including sensors, actuators, control units, and user interfaces. Sensors constantly measuring parameters such as temperature, pressure, and flow rate. Actuators respond to commands from the control unit, adjust physical components like valves and gates to modulate the turbine’s operation. The control unit, often a sophisticated piece of software running on dedicated hardware, processes sensor data to make real-time decisions. Lastly, the user interface provides a vital link between human operators and the automated system, allowing for monitoring and manual intervention when necessary. The most common deployed user interfaces provide dedicated screens known as HMIs (Human Machine Interfaces). However, modern control systems gradually have seen greater used of non-dedicated control interfaces such as laptops and smart phones that offer the benefit of instant notification to operators.

Functionality and Adaptability

The primary function of turbine control systems is to maintain the turbine’s operation within its optimal parameters, thus maximizing efficiency and longevity. This involves a delicate balance of power output and mechanical stress, requiring a high degree of adaptability. Advanced control algorithms, leveraging techniques from artificial intelligence and machine learning, enable these systems to predict and react to changes in input conditions or demand levels. This minimizes wear and tear while optimizing performance. These algorithms allow for precise control over turbine speed, power output, and other critical operational parameters. They can adapt to changing conditions, ensuring the turbine operates at peak efficiency regardless of external variables. This adaptability is crucial in environments where input conditions (such as steam pressure for steam turbines or wind speed for wind turbines) vary widely.

Integration with Plant-wide Management Systems

Turbine control systems are not isolated entities; they often integrate into broader plant management systems. This integration enables coordinated operation across different plant components, enhancing overall plant efficiency and reliability. For example, in a power generation plant, the turbine control system can synchronize with the grid management system to adjust power output in response to demand fluctuations.

Challenges in Control System Design

Designing effective turbine control systems presents a myriad of challenges. First, the system must be robust, capable of operating reliably in harsh environments or under extreme conditions. This necessitates durable materials and fault-tolerant design principles. Secondly, control systems must be precise. Even minor deviations in parameters can lead to significant efficiency losses or safety hazards. Achieving this precision requires high-quality sensors and actuators, as well as sophisticated software capable of processing complex data in real-time.

Predictive Maintenance and Fault Diagnosis

Incorporating predictive maintenance strategies, turbine control systems can forecast potential mechanical issues before they manifest, significantly reducing unplanned downtime. By analyzing trends and patterns in the data collected from sensors, the system can identify signs of wear and tear or impending failure, prompting proactive maintenance actions. Moreover, advanced diagnostic tools within these systems can pinpoint the source of a problem, facilitating quicker asset repair and reducing maintenance costs.

Evolving Technologies

Advances in technology and shifts in energy demands drive the field of turbine control systems. Emerging trends, such as renewable energy integration and the AI revolution, are shaping the development of next-generation control systems. These systems are expected to be more autonomous, energy-efficient, and capable of integrating with smart grids, marking a significant leap forward in turbine technology.

Ensuring Operational Safety

Above all, the safety of operations is paramount. Turbine control systems incorporate multiple safety features and fail-safes designed to prevent accidents. These systems continuously monitor for conditions that could lead to hazardous situations, such as overheating or excessive pressure build-up, and automatically initiate shutdown procedures if critical thresholds are exceeded.

Compliance with Standards and Regulations

Finally, turbine control systems must comply with national and international standards and regulations governing safety, emissions, and operational performance. Compliance ensures that turbines operate efficiently and adhere to environmental and safety guidelines while minimizing impact on the environment.

Understanding Controls for the Four Main Turbine Types

Each major turbine type presents unique control challenges, necessitating tailored automation solutions.

Steam Turbines

Steam turbines are widely used in power generation and industrial applications. Control systems for steam turbines focus on managing steam flow and pressure to ensure efficient energy conversion. Precise temperature controls are critical to preventing thermal stress and maintaining turbine longevity. Advanced control algorithms adjust the turbine’s operation in response to fluctuating demand and steam supply conditions, ensuring optimal performance under varying loads.

Gas Turbines

Gas turbines, integral to many power plants and aircraft, demand precise control over fuel combustion and air intake. Automation in gas turbines is centered around fuel efficiency and emission control. Real-time monitoring and control ensure the turbine operates within safe temperature and pressure limits, safeguarding against operational risks.

Wind Turbines

Wind turbine controls are designed to maximize energy capture from unpredictable wind resources. This involves adjusting blade pitch and rotor orientation to harness wind energy effectively. Sophisticated sensors and control systems continually adjust the turbine’s settings to optimize performance, contributing to the reliability and efficiency of wind power generation.

PETROTECH’S Solution to Turbine Automation

Petrotech excels in providing cutting-edge turbine automation solutions, tailored to enhance efficiency and reliability across the energy sector. Our state-of-the-art control systems are engineered to optimize the performance of turbines in oil, gas, power generation, and beyond, ensuring superior operational control and energy production optimization. With Petrotech, embrace the future of automated energy with confidence.

Steam turbines serve as integral components in the petrochemical, power generation, and refinery industries. The foundational architecture of a steam turbine comprises a rotor, precision-supported by bearings and encased within a cylindrical casing. The controlled interaction between steam and meticulously designed blades results in a tangential force and instigates the systematic rotation of the rotor. This intricate arrangement visualizes a steam turbine as a series of windmill-like structures on a single shaft.

Parts of Steam Turbine

Steam Chest and the Casing

The steam chest connects to the high-pressure steam supply line while the low-pressure steam exhaust line affixes to the casing as shown in Figure 1. The steam chest positions between the casing houses the governor valve and the overspeed trip valve. The nozzles, located inside the casing, direct the flow of steam onto the rotating buckets.

Rotor

The rotor consists of a bucket-equipped shaft and disc sections. The shaft emerges from the casing and through the bearing cases. A driven pump connects to one end of the shaft and the speed governor and overspeed trip system are located on the opposite end.

The Bearing Cases

As shown in Figure 1, the bearing cases support the rotor, along with the assembly steam chest and steam chest. The bearing cases contain journal bearings and rotating oil seals. The oil seals keep oil inside and water, dust, and steam out. The steam end bearing case also includes the rotor positioning bearing and the rotating parts of the overspeed trip system. The steam end-bearing case covers the moving parts.

Casing Sealing Glands

A seal exists between the casing and the shaft provided by the casing sealing glands. For this, the system uses spring-backed, segmented carbon rings. These rings are supplemented by adding a spring-backed labyrinth section that makes the exhaust steam work better.

Governor System

Control systems, called governor systems are built into steam turbines and can sense when the speed changes. They can change turbine speed by changing the governor valve, which controls the steam flow through the turbine. The governor also contains rotating weights that push against each other by a servo motor system. The governor determines the turbine shaft’s speed via a straight link, or a magnetic impulse from a gear. A set point compares the rotor speed and the servo motor receives the governor output signal. Changes in the input and exit steam of the turbine, as well as changes in how much power the pump needs, will dictate the turbine’s speed. When the speed changes, the governor weights move, which moves the governor valve.

Over-Speed Trip System

The governor takes control of the rotating system, swiftly sealing the trip aperture to interrupt the flow of steam to the engine upon detecting an excessive speed. This arrangement comprises of a turbine shaft collar featuring a pin or weight under spring tension, an expeditious closure valve distinct from the governor valve, and an interconnecting linkage. As the pin rotates within the turbine shaft, it generates a centrifugal force surpassing the spring’s opposition at a specific velocity.

Labyrinth Seal

A labyrinth is a structure that is meant to keep fluid from going from a high-pressure zone to a low-pressure zone by letting only a small amount of fluid leak out. Maintaining the smallest possible clearance between the labyrinth and the shaft is important.

Nozzle Ring and Curtis Stage

Assembly of the nozzle ring and reversing blade in the steam end casing is a meticulous process. The nozzle ring firmly secures to the lower section of the steam end casing through bolts.

The nozzle ring interfaces with what is called a Curtis stage. This Curtis stage provides an essential part of the turbine’s design, especially in turbines with a significant drop in steam pressure.

A Curtis stage typically consists of one or two sets of highly specialized blades that typically undergo a specialized heat-treating process to directionally align the grains. After the blades, exists a set of stationary nozzles or guide vanes. The high-pressure steam first passes through the stationary nozzles, where it expands rapidly, converting the thermal energy of the steam into kinetic energy. This high-velocity steam then strikes the moving blades, imparting momentum and thus rotating the turbine shaft.

The reversing blade system strategically lies inside the Curtis stage, housing two rows of blades. Acting as conduits, the nozzles embedded in the nozzle ring propel the steam from the steam box to the initial row of blades in the Curtis stage, held securely by the nozzle ring. Once the steam traverses the first row of blades and progresses towards the subsequent blades, the reversing blades help alter the flow direction. The entire unit stabilizes along its length by spacers, reducing vibration and ensuring a smooth-running turbine.

Sentinel Valve

This part is at the top of the exhaust end of the turbine casing and acts as a warning system. It activates when the pressure inside the turbine’s exhaust end casing becomes too high. When the pressure inside the casing rises above a certain level and exceeds the standard working pressure, the valve will release a small quantity of steam that can be seen and heard.

Auxiliary Steam Valves

Auxiliary valves improve working efficiency when there are changes in load or steam conditions. The valves are inside the steam tunnel, between the steam chest and the nozzle ring at the lower end of the turbine casing’s steam end. The tube splits into three separate sections. One section stays open all the time so that steam can keep going to a bank of nozzles in the nozzle ring. The other two sections contain auxiliary hand valves to control steam flow to two other banks of nozzles within the same nozzle ring.

Turning Gears

Large turbines come with gears that rotate to make it easier for the rotors to turn slowly while they warm up and cool down. To keep the shaft or rotor straight and balanced, this is done to ensure consistent temperature around its entire diameter.

Carbon Ring Seals

The structure is made up of pieces of a carbon ring that are held together by a spring. The anti-rotation stops fit firmly into the notches in the bottom half of the interstage casing. In addition, the carbon rings are used to successfully stop any rotation from happening.

Turbine Cylinders

Turbine cylinders have to withstand the pressure of the steam, so they need to be built solidly with thick walls. Because they are exposed to high steam temperatures, thick-walled components are not desirable. When temperature differences exist inside stiff parts, they put a lot of stress on the material. These stresses can break down materials when ­­added to the mechanical stress that comes from pressure.

Petrotech’s Steam Turbine Control Support

Petrotech’s advanced steam turbine controls for compressor and generator drive applications feature an integrated control package that provides speed and capacity control. Overspeed protection is implemented in both the software and hardware. To learn more about our line of turbomachinery controls, explore our literature library.

NOx, short for nitrogen oxides, refers to a group of reactive gases that significantly contribute to air pollution. In this article, we delve into the definition of NOx, examine emissions based on fuel types, and explore effective methods to reduce NOx levels.

How NOx Forms and its Impact

Nitrogen oxide gases, NOx, are formed by NO and NO2. It contributes to air pollution and provides a major challenge regarding environmental and human health. They are the result of the burning of fossil fuels in many industrial operations, vehicle engines, and power stations.

Nitrogen oxide (NOx) emitted from different combustion processes is not retained in the atmosphere for an extended period. They will be converted to other compounds by chemical reactions, like NO combining with water and other materials. This is one of the causes of acid rain which is an undesirable result from an environmental perspective. Acid precipitation is hazardous to all water bodies and soils, thus adversely affecting plant life and the ecosystem at large.

Adverse Effects of High NOx Emissions

High levels of nitrogen oxide (NOx) emissions result in various derivatives, such as nitrogen dioxide, nitric acid, nitrous oxide, nitrates, and nitric oxide, each contributing to a spectrum of health and environmental impacts as reported by the EPA.

1. Ground-level Ozone: NOx is the pseudo chemical formula for the Oxides of Nitrogen. The are 5 different oxides of nitrogen but the prevalent compounds in combustion are NO, NO2, and NO3. These three compounds react with heat and sunlight to produce ground-level ozone which is what we know as smog. This process leads to serious adverse effects, including damage to lung tissue, reduced lung function—especially in vulnerable populations like children, the elderly, and those with conditions such as asthma—and hazardous impacts on vegetation and crop yields.
2. Particles: Nitric acid vapor and related particles form when NOx reacts with ammonia. These small particles have the potential to penetrate deeply into sensitive parts of the lungs, resulting in various human health concerns. Effects on breathing, damage to the respiratory system, and premature death may result after exposure to these particles.
3. Global Warming: Nitrous oxide (NO2), a greenhouse gas, accumulates in the atmosphere alongside other greenhouse gases. This accumulation contributes to the Greenhouse Effect, causing a gradual rise in the Earth’s temperature. The long-term consequences include severe risks to human health, a rise in sea levels, and adverse changes to plant and animal habitats.
4. Visibility Impairment: Higher levels of NOx in the air can block the transmission of light, leading to reduced visibility in urban areas. This impairment can have significant consequences for daily life and poses challenges for transportation and public safety.
5. Toxic Chemicals: In the air, reactions of NOx with other organic chemicals result in the formation of various toxic products. These products may cause adverse biological effects, underscoring the importance of addressing and mitigating NOx emissions to safeguard public health.
6. Water Quality Deterioration: Increased nitrogen loading in water bodies adversely affects the chemical balance of nutrients in aquatic life. This acceleration of “eutrophication” leads to oxygen depletion and a reduction in fish and shellfish populations. The overall deterioration of water quality has cascading effects on aquatic ecosystems.
7. Acid Rain: NOx and sulfur dioxide in the air are major components of acids that fall to Earth as rain, fog, snow, or dry particles. Wind can carry these formations for long distances, resulting in acid rain. This phenomenon damages forests, causes deterioration of exposed substances, and renders water bodies acidic and unsuitable for life. Addressing NOx emissions is crucial to mitigate the far-reaching impact of acid rain on ecosystems.

Reviewing Emissions by Fuel Type

To understand how NOx emissions affect the environment, let’s look at different sources connected to different fuel types. Each kind of fuel contributes in its own way to the issues caused by nitrogen oxides.

• Mobile Sources – Automobiles and Other Vehicles: Approximately half of global NOx emissions stem from mobile sources, specifically automobiles and other mobile sources. The combustion engines in cars, trucks, buses, and airplanes release significant amounts of nitrogen oxides into the atmosphere. 
• Stationary Sources – Electric Power Plants: Electric power plants, particularly those utilizing boilers, account for a substantial 40% of NOx emissions from stationary sources. The combustion of various fuels in power generation contributes significantly to the overall NOx levels. 
• Anthropogenic Sources – Industrial Processes and Combustion Engines: The remaining 30% of NOx emissions result from diverse anthropogenic sources, including industrial boilers, incinerators, gas turbines, reciprocating spark ignition, and Diesel engines in stationary sources. Additionally, sectors such as iron and steel mills, cement manufacture, glass manufacture, petroleum refineries, and nitric acid manufacture contribute to this category.
• Biogenic, or Natural Sources: Beyond human activities, biogenic or natural sources play a role in NOx emissions. Lightning, forest fires, grass fires, trees, bushes, grasses, and yeasts release nitrogen oxides into the atmosphere. 

Methods to Reduce NOX

Reducing NOx emissions from combustion sources involves employing proven strategies and technologies. Here are some effective approaches:

During Combustion

The following technologies reduce NOx during the combustion process:

• Wet Low Emissions (WLE) Technology
• Dry Low Emissions (WLE) Technology
• Catalytic Combustion

Low NOx technology in gas turbines centers around Wet Low Emissions (WLE) and Dry Low Emissions (DLE). The formation of NOx in a combustion process is dependent upon flame temperature. Therefore, reducing the flame temperature significantly reduces NOx formation. WLE and DLE technologies employ similar principles to reduce flame temperature, but their physical application is entirely different.

Wet Low Emissions (WLE)

WLE is the older of the two technologies and is simply the injection of water into the gas turbine combustor. The water adds mass which absorbs heat (enthalpy) and reduces the flame temperature. WLE deploys on older gas turbines primarily because the combustor designs used for DLE cannot easily retrofitted onto the older gas turbines.

Petrotech builds and supplies water injection control systems as well as skid-mounted water injection pumping systems for gas turbine injection installations.

Dry Low Emissions (DLE)

DLE is the current best available technology for NOx gas turbine abatement. Here the original equipment manufacturers (OEMs) manufacture a specially designed combustor that uses excess air (also called lean pre-mixed combustion) rather than water to prevent the formation of NOx. The excess air absorbs heat (enthalpy) and reduces the flame temperature. The Turbine Fuel Regulation (TFR) controls for DLE also require more sophisticated algorithms than the legacy TFRs found on WLE installations. Petrotech can provide DLE TFR controls as well.

Catalytic combustion

Catalytic combustion starts with the fuel getting injected upstream of the reactor, vaporizing and mixing with the inlet air. The fuel mixture then goes through the catalytic bed, where fuel and oxygen combustion occurs on the catalyst surface regardless of the fuel-air ratio. The heat of the exothermic reaction is released. The remaining fuel is combusted downstream at low temperatures to reduce the quantity of NOx formed.

Post-formation NOx-control technology

Selective Catalytic Reduction (SCR)

Selective Catalytic Reduction (SCR) stands as a post-formation NOx-control technology utilizing a catalyst and ammonia to reduce NOx to nitrogen and water. Here’s how it works:

• An ammonia/air or ammonia/steam mixture injects into the gas turbine exhaust gas stream.
• The gas, along with the injected mixture, passes through a catalyst where NOx is reduced.

To optimize the reaction, the temperature of the exhaust gas must fall within a specific range as it passes through the catalyst bed. Typically, SCR achieves removal efficiencies greater than 80%, irrespective of the combustion process or fuel type used.

While effective, SCR has certain drawbacks. It necessitates additional space for the catalyst and reactor vessel, as well as infrastructure for ammonia storage, distribution, and injection. Compliance with Federal Accidental Release Prevention rules may require the preparation and submission of a Risk Management Plan (RMP) for ammonia storage.

Precise control of ammonia injection is critical to SCR’s success. Inadequate ammonia amounts can result in unacceptably high NOx emission rates, while excess ammonia can lead to ammonia “slip,” where undesirable ammonia is vented to the atmosphere.

Selective Non-Catalytic Reduction (SNCR)

Selective non-catalytic NOx reduction involves injecting ammonia or urea into the flue gas to reduce NOx emissions. Success depends on the injection temperature, with 60% NOx removal achievable at the optimum temperature range.

Petrotech NOx Solutions

Petrotech specializes in NOx abatement solutions for gas turbines. The company’s expertise includes water injection control systems for Wet Low Emission (WLE) and sophisticated Turbine Fuel Regulation (TFR) controls for Dry Low Emission (DLE). Petrotech provides bespoke, innovative, and cost-effective solutions for NOx control in gas turbine applications. To get started on your project, request a quote with us today.