MAN Energy Solutions has commissioned a series of gas turbine packages in China all featuring its MGT 6000 machine. The developments are a confirmatory signal of the significant growth in demand for combined heat and power projects in industrial and commercial settings across Asia and in China in particular. Marked by a shift towards cleaner sources of energy generation and a related move to phase out coal fired capacity, demand has focused on relatively small sub-10 MW combined heat and power (CHP) applications in industrial and commercial settings.
Typically, such distributed generation installations are combined with a local demand for process steam and hot water for smaller industrial processes or district heating. With short erection times, low maintenance costs, low emissions and the benefits of fuel flexibility and a variable output, smaller gas turbines offer a host of advantages in these kinds of applications.
Looking to exploit a growing market, MAN ES decided to develop a new design in the 6-7 MW power range. Dr. Sven-Hendrik Wiers, Vice President of Gas Turbines at MAN Energy Solutions, explains the design philosophy behind the machine, which became the MGT 6000: “We designed it specifically for CHP because the smaller distributed power market is rapidly growing in Asia and elsewhere. We believe that the trend is more towards distributed energy and CHP, especially for industrial parks or data centres, for example.”
He continues: “This machine has been designed especially for these kinds of applications and it has a relatively high exhaust temperature of 505°C which is perfectly in line with CHP. We have also taken care to produce a robust design. The turbine inlet temperature is still moderate. It is not at the edge of technology in order to guarantee a robust design and to keep availability high.”
Modern robust design
Work on developing the completely new family of low-emission gas turbine power trains concluded in 2013. Both single and twin shaft configurations were designed for power generation and mechanical drive applications, respectively.
MAN developed the gas turbine series in-house. According to the company, it is one of the world´s most modern industrial gas turbines in its power class and combines the advantages of heavy duty machines with elements of aeroderivative gas turbines.
However, rather than designing for the highest possible firing temperatures requiring high specification materials, instead MAN ES chose to improve performance by reducing flow losses and applying advanced blade cooling.
“Our approach was to design a highly efficient gas turbine and this has been done by applying jet engine technology. By using advanced cooling and sealing technologies we were able to achieve performance targets at moderate turbine inlet temperatures and without requiring fancy materials and coatings” explained Wiers.
Tested at MAN’s gas turbine test centre in Oberhausen, the first engine was delivered to the launch customer in 2013. To date, the commissioned fleet of the MGT 6000 has achieved some 130 000 operational hours.
A flexible option for CHP
The single shaft machine is available in a range of outputs from 6 MWe up to 7.8 MWe and a gross efficiency of up to 33.2%.
Within the cast casings, which are split at the compressor section, the machine features an 11-stage compressor and a three stage axial flow turbine. It operates at a nominal pressure ratio of 15:1. The inlet guide vanes and three downstream rows of stator vanes are adjustable. This allows optimization of aerodynamic behaviour and enhances the stability margin during part load operations. By varying part-load airflow it is possible to maintain high exhaust gas temperatures even at part-load, ensuring efficiency in CHP applications. The shaft output of the single-shaft machine is at the cold compressor end and includes a reduction gearbox.
In the MGT 6000, stator vanes and rotor blades of the first two stages are internally cooled.
Six Advanced Can Combustion (ACC) chambers are distributed around the circumference of the machine. Each burner features a radial swirler and two separate gas injectors. These are operated in different modes depending on load and help control emissions.
“You’re able to run this at absolutely state-of-the-art emissions levels. We achieve this just through tuning the combustion characteristics, the design of the premix combustion chamber for example. It’s a very robust design but we are also able to achieve low emissions,” says Wiers.
The dry low NOx combustion system allows NOx emissions of below 10 ppm to be maintained over a wide range of outputs.
The MGT 6000 also has a degree of fuel flexibility. “We can go up to 15% hydrogen but also flare gas, biogas, a huge variety of fuels, but especially hydrogen which I think will be the future,” notes Wiers.
AM simplifies complex designs
Despite its largely conventional design approach and focus on proven reliability of components, the MGT 6000 does make use of cutting edge manufacturing techniques. The last stage compressor vanes are produced using additive manufacturing (AM), for example. Furthermore, rather than single vanes being produced individually, a cluster of 12 are manufactured simultaneously. By using AM techniques, MAN ES has managed to reduce the number of components in this complete stage of stator vanes from 144 parts to just 12.
Wiers explained the reasoning behind the decision to use AM. “We are able to combine a lot of components and reduce the number of parts. Another benefit is that we can even improve the efficiency of the compressor by reducing flow losses and we simplify production and complexity.
“AM allows you to apply new cooling technology and reduce cooling air requirements. By doing that our losses could be reduced and that means an efficiency improvement. By printing designs which you couldn’t manufacture before, you can increase the cooling efficiency and therefore increase the efficiency of the whole engine.”
He continued: “And of course the printing of prototypes means that they are much faster into testing, allowing new designs to enter service more quickly. We are also looking at AM for other turbine components like liners and combustion nozzles and so on, but our first component materials selection was based on limiting operational risk.”
Indeed, the robust design of the MGT 6000 allows MAN ES to offer extended service intervals as standard. “We designed for a 40 000 operating hour major service interval. This is unique and for us, it’s important to provide high availability. That robustness of the core machine and package is key,” says Wiers
Building a market in China
MAN ES’ first success in China with the MGT 6000 came in late 2014 with an order from the Shanghai Aerospace Energy Corporation. Under the terms of the deal, four of the gas turbines were procured for the Anting/Shanghai power station for Volkswagen China/Shanghai Motors. This project was put into operation in January 2016 and executed together with Shanghai Aerospace Energy Co Ltd, which took the EPC responsibility and supplied boilers, air intake and exhaust systems as well as generators. In this power station, four boilers generate steam for the automobile production lines and hot water. In total, the plant generates approximately 26 MWe, as well as production of heat.
Following on from this project, the latest developments using the MGT 6000 include another one with Shanghai Aerospace Energy Co Ltd acting as EPC. Including a MGT 6000 and a MAN THM series gas turbine integrated into a CHP process application, collectively the two machines deliver around 17 MWe and 35 MWth to an industrial park in Changsha, the provincial capital of Hunan Province in south central China. The gas turbine packages are replacing a coal fired plant that is now decommissioned, resulting in a significant emissions reduction for the city.
Two additional MGT 6000 gas turbines are being used in paper production facilities at a cogeneration plant optimized for natural gas operation in an industrial zone of Dongguan City in Guangdong Province to the east of Hunan. In addition to about 6 MWe, it will also provide 13 MWth.
A fourth MAN MGT 6000 package was deployed in Lianyungang in the Jiangsu Province of northeastern China for a major synthetic fibre manufacturing company.
The installed system is equipped with an ATU (Analytics Telemetry Unit), which will allow the manufacturer to monitor the machine’s operation in order to evaluate the system operation and on-going performance and, therefore allow plant optimization.
MAN ES offers a range of long term service arrangements via the company’s PrimeServ maintenance division, including online monitoring and predictive maintenance packages, as well as full operations and maintenance.
Wiers explains the importance of data in maintaining optimum performance. “Our engineers require online access to our in-service machines to go from preventive to predictive maintenance. We’re able to look at the data and we have algorithms in place to calculate how we can really extend the service intervals, which brings an important benefit to our customers.”
Each packaged engine comes with a control system equipped with a remote data transmission interface. This allows the transmission of data for analysis, diagnostics and maintenance support if required and also enables remote monitoring for the operator.
Fit for China
In each of the latest examples the MGT 6000 single-shaft version has been deployed. “We are working together with local EPC partners in China. We supply the packaged engine. The core machine is built in Oberhausen in Germany, the packaging is done in our workshop in Changzhou in China,” says Wiers.
Delivered as pre-mounted units on a steel base frame, the packaged engine comes complete with all the required auxiliary systems, air inlet and exhaust modules, engine and driven equipment controls, fire detection and suppression as well as the sound enclosure. Such pre-assembled packages help to minimize erection and engine installation work at site.
As Wiers explained: “It’s a single lift unit. Everything is pre-tested; installation time is quite short and straightforward for power generation or CHP applications. You can standardise the whole path. This is the approach, to really minimize the erection and the commissioning time and the time needed for maintenance. We’re able to do a turbine exchange within 48 hours. The main focus for us is customer satisfaction and you get customer satisfaction when you have high availability.”
Aimed at industries such as food or paper production, high availability is a must. “Industries like these don’t necessarily care what kind of machine they have. They just want to have heat and power with high availability,” said Weirs.
To support availability MAN ES has a local office. “We have our service workshops in Shanghai and Changzhou where we have the spare parts and our educated staff. We also have an academy in Shanghai where we offer customer training. Our approach is to really give the customer all the knowledge they need to smoothly operate their plant.”
Powering up small-scale CHP
China is rapidly building LNG terminal capacity and successfully bringing it on line so there is no shortage of gas and there is a substantial pipeline of potential projects in this power range as the country looks to improve urban air quality and meet ambitious carbon emissions goals.
The same is true elsewhere in Asia where a strong demand for power and heat is being paralleled with ramping LNG import capacity. Malaysia, Bangladesh and Indonesia, for example, are notably strong markets for small-scale CHP developments.
Wiers concludes: “Energy production will be more decentralized and I believe that the most efficient technology to produce distributed power and heat in many applications is the use of gas turbines in CHP. We are pretty confident because if you look at the numbers it’s a competitive engine and we do see huge market potential; this was the driver for us to design it.”