Gas turbines play a huge role in power plant reliability. In most cases—whether it be simple-cycle or combined-cycle applications for gas turbines—the gas turbine is the first major piece of equipment in the process that needs to start. So, without a reliable control system or a well-maintained and cared-for control system, your primary piece of major equipment is out of the game or unavailable.
Typically, when most frames 7FA, 6FA, 5A, or any industrial frame size gas turbine owner starts the plant with the gas turbine control system, there is typically a page with start permissives, indicating the system is ready to start or not ready to start. Start permissives are conditions on the unit that need to be met before it can start.
In many cases, the rest of the equipment at the plant depends on the gas turbine control system because it is often the first thing that plant managers will start before the other equipment.
Therefore, if you receive the “not ready to start” indication, then you won’t be able to start your gas turbine—or the rest of your plant at all, especially if there are other drivers behind the gas turbine.
How the Control System Works
A control system is made up of a bunch of subsystems, pretty much like everything in a power plant. So, the control system as a whole has subsystems under it, and that can kind of be broken down and analyzed in an engineering mind state.
The primary parts of the control system are the software and logic, which are really reliable. They don’t typically break; they are just computer code that is programmed.
Typically when we see problems, malfunctions, abnormalities in logic or software, it’s because of some type of human interaction. Most control systems or any other equipment for that matter don’t fail on their own. Of course, failures without human interaction can happen, but they are rare.
The relays in the system that bring the logic from the software are typically control cards and other communication devices. These devices can fail. In these cases, when the devices can fail, the logic and software fails as well.
Why Reliability is So Important
If you don’t have a reliable gas turbine control system, then you usually can’t even get the plane off the ground, so to speak. You can’t even really gain any momentum!
Therefore, it is important to perform check out and regular inspections of your control system equipment. At TC&E we like to call these inspections “reliability assessments”. To put it simply, it involves a clean and inspect of the system.
At TC&E, our team checks the control system, cleans it out, performs some file management, and ensures that there aren’t any warning lights and that everything looks healthy and functional.
Contact our team today to learn more about our reliability assessments and what we can do to help ensure your plant’s reliability.
The palm kernel shells used to be initially dumped in the open thereby impacting the environment negatively without any economic benefit. However, over time, palm oil mills in Southeast Asia and elsewhere realized their brilliant properties as a fuel and that they can easily replace coal as an industrial fuel for generating heat and steam.
Palm kernel shells is an abundant biomass resource in Southeast Asia
Nowadays, the primary use of palm kernel shells is as a boiler fuel supplementing the fibre which is used as primary fuel. In recent years kernel shells are extensively sold as alternative fuel around the world. Besides selling shells in bulk, there are companies that produce fuel briquettes from shells which may include partial carbonisation of the material to improve the combustion characteristics.
Palm kernel shells have a high dry matter content (>80% dry matter). Therefore the shells are generally considered a good fuel for the boilers as it generates low ash amounts and the low K and Cl content will lead to less ash agglomeration. These properties are also ideal for production of biomass for export.
As a raw material for fuel briquettes, palm shells are reported to have the same calorific characteristics as coconut shells. The relatively smaller size makes it easier to carbonise for mass production, and its resulting palm shell charcoal can be pressed into a heat efficient biomass briquette.
Although the literature on using oil palm shells (and fibres) is not as extensive as EFB, common research directions of using shells, besides energy, are to use it as raw material for light-weight concrete, fillers, activated carbon, and other materials. However, none of the applications are currently done on a large-scale. Since shells are dry and suitable for thermal conversion, technologies that further improve the combustion characteristics and increase the energy density, such as torrefaction, could be relevant for oil palm shells.
Torrefaction is a pretreatment process which serves to improve the properties of biomass in relation to the thermochemical conversion technologies for more efficient energy generation. High lignin content for shells affects torrefaction characteristics positively (as the material is not easily degraded compared to EFB and fibres).
Furthermore, palm oil shells are studied as feedstock for fast pyrolysis. To what extent shells are a source of fermentable sugars is still not known, however the high lignin content in palm kernel shells indicates that shells are less suitable as raw material for fermentation.
The leading palm oil producers in the world should consider limiting the export of palm-kernel shells (PKS) to ensure supplies of the biomass material for renewable energy projects, in order to decrease dependency on fossil fuels. For example, many developers in Indonesia have expressed an interest in building palm kernel shell-fired power plants.
However, they have their concerns over supplies, as many producers prefer to sell their shells overseas currently. Many existing plants are facing problems on account of inconsistent fuel quality and increasing competition from overseas PKS buyers. PKS market is well-established in provinces like Sumatra and export volumes to Europe and North Asia as a primary fuel for biomass power plants is steadily increasing.
The creation of a biomass supply chain in palm oil producing countries may be instrumental in discouraging palm mills to sell their PKS stocks to brokers for export to foreign countries. Establishment of a biomass exchange in leading countries, like Indonesia, Malaysia and Nigeria, will also be a deciding factor in tapping the unharnessed potential of palm kernel shells as biomass resource.
A palm oil plantation yields huge amount of biomass wastes in the form of empty fruit bunches (EFB), palm oil mill effluent (POME) and palm kernel shell (PKS). In a typical palm oil mill, empty fruit bunches are available in abundance as fibrous material of purely biological origin. Energy potential of empty fruit bunches is attractive as it contains neither chemical nor mineral additives, and depending on proper handling operations at the mill, it is free from foreign elements such as gravel, nails, wood residues, waste etc.
However, EFB is saturated with water due to the biological growth combined with the steam sterilization at the mill. Since the moisture content in EFB is around 67%, pre-processing is necessary before EFB can be considered as a good fuel.
Unprocessed EFB is available as very wet whole empty fruit bunches each weighing several kilograms while processed EFB is a fibrous material with fiber length of 10-20 cm and reduced moisture content of 30-50%. Additional processing steps can reduce fiber length to around 5 cm and the material can also be processed into bales, pellets or pulverized form after drying.
There is a large potential of transforming EFB into renewable energy resource that could meet the existing energy demand of palm oil mills or other industries as well as to promote sustainability in the palm oil industry. Pre-treatment steps such as shredding/chipping and dewatering (screw pressing or drying) are necessary in order to improve the fuel property of EFB.
Pre-processing of EFB will greatly improve its handling properties and reduce the transportation cost to the end user i.e. power plant. Under such scenario, kernel shells and mesocarp fibres which are currently utilized for providing heat for mills can be relieved for other uses off-site with higher economic returns for palm oil millers.
The fuel could either be prepared by the mills before sell to the power plants, or handled by the end users based on their own requirements. Besides, centralized EFB collection and pre-processing system could be considered as a component in EFB supply chain. It is evident that the mapping of available EFB resources would be useful for EFB resource supply chain improvement. This is particular important as there are many different competitive usages. With proper mapping, assessment of better logistics and EFB resource planning can lead to better cost effectiveness for both supplier and user of the EFB.
A covered yard is necessary to store and supply a constant amount of this biomass resource to the energy sector. Storage time should however be short, e.g. 5 days, as the product; even with 45% moisture is vulnerable to natural decay through fungi or bacterial processes. This gives handling and health problems due to fungi spores, but it also contributes through a loss of dry matter trough biological degradation. Transportation of EFB is recommended in open trucks with high sides which can be capable of carrying an acceptable tonnage of this low-density biomass waste.
For EFB utilization in power stations, the supply chain is characterized by size reduction, drying and pressing into bales. This may result in significantly higher processing costs but transport costs are reduced. For use in co-firing in power plants this would be the best solution, as equipment for fuel handling in the power plant could operate with very high reliability having eliminated all problems associated with the handling of a moist, fibrous fuel in bulk.
Europe is targeting an ambitious renewable energy program aimed at 20% renewable energy in the energy mix by 2020 with biomass energy being key renewable energy resource across the continent. However, the lack of locally-available biomass resources has hampered the progress of biomass energy industry in Europe as compared with solar and wind energy industries. The European biomass industry is largely dependent on wood pellets and crop residues.
Europe is the largest producer of wood pellets, which is currently estimated at 13.5 million tons per year while its consumption is 18.8 million tons per year. The biggest wood pellet producing countries in Europe are Germany and Sweden. Europe relies on America and Canada to meet its wood pellet requirements and there is an urgent need to explore alternative biomass resources. In recent years, palm kernel shells (popularly known as PKS) from Southeast Asia has emerged has an attractive biomass resources which can replace wood pellets in biomass power plants across Europe.
What are Palm Kernel Shells
Palm kernel shells are the shell fractions left after the nut has been removed after crushing in the Palm Oil mill. Kernel shells are a fibrous material and can be easily handled in bulk directly from the product line to the end use. Large and small shell fractions are mixed with dust-like fractions and small fibres.
Moisture content in kernel shells is low compared to other biomass residues with different sources suggesting values between 11% and 13%. Palm kernel shells contain residues of Palm Oil, which accounts for its slightly higher heating value than average lignocellulosic biomass. Compared to other residues from the industry, it is a good quality biomass fuel with uniform size distribution, easy handling, easy crushing, and limited biological activity due to low moisture content.
Press fibre and shell generated by the palm oil mills are traditionally used as solid fuels for steam boilers. The steam generated is used to run turbines for electricity production. These two solid fuels alone are able to generate more than enough energy to meet the energy demands of a palm oil mill.
Advantages of Palm Kernel Shells
PKS has almost the same combustion characteristics as wood pellets, abundantly available are and are cheap. Indonesia and Malaysia are the two main producers of PKS. Indonesian oil palm plantations cover 12 million hectares in Indonesia and 5 million hectares in Malaysia, the number of PKS produced from both countries has exceeded 15 million tons per year. Infact, the quantity of PKS generated in both countries exceeds the production of wood pellets from the United States and Canada, or the two largest producers of wood pellets today.
Interestingly, United States and Canada cannot produce PKS, because they do not have oil palm plantations, but Indonesia and Malaysia can also produce wood pellets because they have large forests. The production of wood pellets in Indonesia and Malaysia is still small today, which is less than 1 million tons per year, but the production of PKS is much higher which can power biomass power plants across Europe and protect forests which are being cut down to produce wood pellets in North America and other parts of the world.
PKS as a Boiler Fuel
Although most power plants currently use pulverized coal boiler technology which reaches around 50% of the world’s electricity generation, the use of grate combustion boiler technology and fluidized bed boilers is also increasing. Pulverized coal boiler is mainly used for very large capacity plants (> 100 MW), while for ordinary medium capacity uses fluidized bed technology (between 20-100 MW) and for smaller capacity with combustor grate (<20 MW). The advantage of boiler combustion and fluidized bed technology is fuel flexibility including tolerance to particle size.
When the pulverized coal boiler requires a small particle size (1-2 cm) like sawdust so that it can be atomized on the pulverizer nozzle, the combustor grate and fluidized bed the particle size of gravel (max. 8 cm) can be accepted. Based on these conditions, palm kernel shells has a great opportunity to be used as a boiler fuel in large-scale power plants.
Use of PKS in pulverized coal boiler
There are several things that need to be considered for the use of PKS in pulverized coal boilers. The first thing that can be done is to reduce PKS particle size to a maximum of 2 cm so that it can be atomized in a pulverized system. The second thing to note is the percentage of PKS in coal, or the term cofiring. Unlike a grate and a fluidized bed combustion that can be flexible with various types of fuel, pulverized coal boilers use coal only. There are specific things that distinguish biomass and coal fuels, namely ash content and ash chemistry, both of which greatly influence the combustion characteristics in the pulverized system.
PKS has emerged as an attractive biomass commodity in Japan
Coal ash content is generally greater than biomass, and coal ash chemistry is very different from biomass ash chemistry. Biomass ash has lower inorganic content than coal, but the alkali content in biomass can change the properties of coal ash, especially aluminosilicate ash.
Biomass cofiring with coal in small portions for example 3-5% does not require modification of the pulverized coal power plant. For example, Shinci in Japan with a capacity of 2 x 1,000 MW of supercritical pulverized fuel with 3% cofiring requires 16,000 tons per year of biomass and no modification. Similarly, Korea Southeast Power (KOSEP) 5,000 MW with 5% cofiring requires 600,000 tons per year of biomass without modification.
PKS cofiring in coal-based power plants
Pulverized coal-based power plants are the predominant method of large-scale electricity production worldwide including Europe. If pulverised fuel power plants make a switch to co-firing of biomass fuels, it will make a huge impact on reducing coal usage, reducing carbon emissions and making a transition to renewable energy. Additionally, the cheapest and most effective way for big coal-based power plants to enter renewable energy sector is biomass cofiring. Palm kernel shells can be pyrolyzed to produce charcoal while coal will produce coke if it is pyrolyzed. Charcoal can be used for fuel, briquette production and activated charcoal.
Sugar industry has always occupied a prominent position in the Mauritian economy since the introduction of sugarcane around three centuries ago. Mauritius has been a world pioneer in establishing sales of bagasse-based energy to the public grid, and is currently viewed as a model for other sugarcane producing countries, especially the developing ones.
Sugar factories in Mauritius produce about 600,000 tons of sugar from around 5.8 million tons of sugarcane which is cultivated on an agricultural area of about 72,000 hectares. Of the total sugarcane production, around 35 percent is contributed by nearly 30,000 small growers. There are more than 11 sugar factories presently operating in Mauritius having crushing capacities ranging from 75 to 310 tons cane per hour.
During the sugar extraction process, about 1.8 million tons of Bagasse is produced as a by-product, or about one third of the sugarcane weight. Traditionally, 50 percent of the dry matter is harvested as cane stalk to recover the sugar with the fibrous fraction, i.e. Bagasse being burned to power the process in cogeneration plant. Most factories in Mauritius have been upgraded and now export electricity to the grid during crop season, with some using coal to extend production during the intercrop season.
Surplus electricity is generated in almost all the sugar mills. The total installed capacity within the sugar industry is 243 MW out of which 140 MW is from firm power producers. Around 1.6 – 1.8 million tons of bagasse (wet basis) is generated on an annually renewable basis and an average of around 60 kWh per ton sugarcane is generated for the grid throughout the island.
The surplus exportable electricity in Mauritian power plants has been based on a fibre content ranging from 13- 16% of sugarcane, 48% moisture content in Bagasse, process steam consumption of 350–450 kg steam per ton sugarcane and a power consumption of 27-32 kWh per ton sugarcane.
In Mauritius, the sugarcane industry is gradually increasing its competitiveness in electricity generation. It has revamped its boiler houses by installing high pressure boilers and condensing extraction steam turbine. All the power plants are privately owned, and the programme has been a landmark to show how all the stakeholders (government, corporate and small planters) can co-operate. The approach is being recommended to other sugarcane producing countries worldwide to harness the untapped renewable energy potential of biomass wastes from the sugar industry.
Biomass is being increasingly used in power plants in Japan as a source of fuel, particularly after the tragic accident at Fukushima nuclear power plant in 2011. Palm kernel shell (PKS) has emerged as a favorite choice of biomass-based power plants in the country. Most of these biomass power plants use PKS as their energy source, and only a few operate with wood pellets. Interestingly, most of the biomass power plants in Japan have been built after 2015.
Palm Kernel Shells
Palm Kernel Shell is generating very good traction as a renewable energy resource and biomass commodity in Japan. This is because PKS is the cheapest biomass fuel and is available in large quantities across Southeast Asia. PKS, a biomass waste generated by palm oil mills, can be found in plentiful quantities in Indonesia, Malaysia and Thailand.
PKS must meet the specifications before being exported to Japan. Some key specifications for PKS exports are: moisture content, calorific value and impurities or contaminants (foreign materials). All three variables must meet a certain level to achieve export quality. Japanese markets or their consumers generally require contaminants from 0.5 to 2%, while European 2% – 3%. Japan usually buys with a volume of 10,000 tonnes per shipment, so PKS suppliers must prepare a sufficient stockpile of the PKS. The location of PKS stockpile that is closest to the seaport is the ideal condition to facilitate transportation of shipment.
PKS has emerged as an attractive biomass commodity in Japan
Wood pellets are mostly produced in from wood waste such as sawdust, wood shaving, plywood waste, forestry residues and related materials. The development potential for quantity enlargement is also possible with energy plantations. Technically the properties of wood pellets are not much different from the PKS.
Wood pellet price is more expensive than PKS. Wood pellet production process is more complex than PKS, so wood pellet is categorized as finished product. The quality of wood pellet is generally viewed from its density, calorific value and ash content. Indonesia wood pellet export is not as big as PKS, it is also because of the limited producers of wood pellet itself. Japan buys wood pellets from Indonesia mostly for testing on their biomass power plants. Shipping or export by container is still common in wood pellet sector because the volume is still small. Currently, the world’s leading producer of wood pellets come from North America and Scandinavia. Even for Indonesia itself wood pellet is a new thing, so its production capacity is also not big.
For a short-term solution, exporting PKS is a profitable business. Wood pellets with raw materials from energy plantations by planting the legume types such as calliandra are medium-term solutions to meet biomass fuel needs in Japan. Torrefaction followed by densification can be a long-term orientation. Torrified pellet is superior to wood pellet because it can save transportation and facilitate handling, are hydrophobic and has higher calorific value.
Palm kernel shells are widely used in fluidized bed combustion-based power plants in Japan and South Korea. The key advantages of fluidized bed combustion (FBC) technology are higher fuel flexibility, high efficiency and relatively low combustion temperature. FBC technology, which can either be bubbling fluidized bed (BFB) or circulating fluidized bed (CFB), is suitable for plant capacities above 20 MW. Palm kernel shells (PKS) is more suitable for CFB-based power plant because its size is less than 4 cm.
With relatively low operating temperature of around 650 – 900 oC, the ash problem can be minimized. Certain biomass fuels have high ash levels and ash-forming materials that can potentially damage these generating units. In addition, the fuel cleanliness factor is also important as certain impurities, such as metals, can block the air pores on the perforated plate of FBC unit. It is to be noted that air, especially oxygen, is essential for the biomass combustion process and for keeping the fuel bed in fluidized condition.
The requirements for clean fuel must be met by the provider or seller of the biomass fuel. Usually the purchasers require an acceptable amount of impurities (contaminants) of less than 1%. Cleaning of PKS is done by sifting (screening) which may either be manual or mechanical.
In addition to PKS, biomass pellets from agricultural wastes or agro-industrial wastes, such as EFB pellets which have a high ash content and low melting point, can also be used in CFB-based power plants. More specifically, CFBs are more efficient and emit less flue gas than BFBs.
The disadvantages of CFB power plant is the high concentration of the flue gas which demands high degree of efficiency of the dust precipitator and the boiler cleaning system. In addition, the bed material is lost alongwith ash and has to be replenished regularly.
A large-scale biomass power plant in Japan
The commonly used bed materials are silica sand and dolomite. To reduce operating costs, bed material is usually reused after separation of ash. The technique is that the ash mixture is separated from a large size material with fine particles and silica sand in a water classifier. Next the fine material is returned to the bed.
Currently power plants in Japan that have an efficiency of more than 41% are only based on ultra supercritical pulverized coal. Modification of power plants can also be done to improve the efficiency, which require more investments. The existing CFB power plants are driving up the need to use more and more PKS in Japan for biomass power generation without significant plant modifications.
Privacy & Cookies Policy
Necessary cookies are absolutely essential for the website to function properly. This category only includes cookies that ensures basic functionalities and security features of the website. These cookies do not store any personal information.