Kerawalapitiya combined cycle Power Plant

The Sunday Financial Times of 02nd, 09th and 16th instant carried some interesting correspondence contributed by two parties, Mr. D. Wimalasena (DW) and Mr. Manjula Perera (MP), on the proposed 300 MW Kerawalapitiya Power Plant (KPP), particularly with rference to it operating on Heavy Fuel Oil (HFO). Since there has been some misinformation given by one party (DW), I thought of writing this note lest the readers would accept the reservations made by this writer, and also because of public interest. The main contention of DW is that HFO is not suitable for operating combined cycle gas turbine (CCGT) power plants and that its use has not been recommended by any manufacturer.

Though MP has asserted that he, in fact, was personally involved in operating a HFO fired 1000 MW CCGT plant in China, DW has dismissed that claim saying that there has been some credibility issues in accepting MP’s claim. DW has, in his second letter too, posed the same reservation that a CCGT plant cannot be operated with HFO and that the operator will have to switch over to auto diesel incurring heavy expenditure causing a burden on the consumer.

According to the EIA Report of the proposed KPP, “the power generating block of the proposed CCPP consists of S209E configuration of General Electric (GE) of USA”. The description of this particular model gas turbines given in the GE’s website says that this configuration comprises two GE gas turbines model MS9001E, two steam generators and a single steam turbine. What the website says about the performance and fuel requirements of this gas turbine is as follows.

“The MS9001E gas turbine is GE’s 50 Hz workhorse. With more than 390 units, it has accumulated over 14 million fired hours of utility and industrial service, many in arduous climates ranging from desert heat and tropical humidity to arctic cold. Originally introduced in 1978 at 105 MW, the 9E has incorporated numerous component improvements. The latest model boasts an output of 126 MW and is capable of achieving more than 52 percent efficiency in combined cycle.

With its flexible fuel handling capabilities, the 9E accommodates a wide range of fuels, including natural gas, light and heavy distillate oil, naphtha, crude oil and residual oil. Designed for dual-fuel operation, it is able to switch from one fuel to another while running under load.”

(www.ge-energy.com/prod_serv/products/gas_turbines_cc/en/midrange/ms9001e.htm)

The above description of the GE Gas Turbines due for installation at Kerawalapitiya as given in their website answers two queries raised by DW; that the model 9E GT could be operated on HFO and that this model was introduced first nearly 30 years ago. So, the CCGT installed at Shenzhen is not a “ghost” but a real machine, and there is nothing strange about it.

When DW says that “the first ever 9GT power plant was commissioned only in October 2005”, he has got it mixed up with the GE H System CCPP which was installed at Baglan Bay at Port Talbot in Wales. It was commissioned in 2005 and commercial operations commenced in early 2006. It is the most advanced GT ever built with the state-of-the-art technology achieving an efficiency of 60% when operated with natural gas.

The proposed KPP is expected to run on imported HFO with 1.5% sulphur, as the locally refined heavy oil has higher sulphur content – typically 3.0-3.5%. However, even with this low-sulphur oil, the emission of sulphur dioxide exceeds the maximum permissible amount given in Sri Lanka Draft Standard for Power Plants. The lifetime of turbine blades when operated with HFO will be reduced due to the bombardment of particulates at high speed under very high pressure and high temperature and resulting in its erosion. However, if the manufacturer recommends the use of HFO, it means that the blades are specially treated to withstand erosion by particulates present in the gas, and this undoubtedly will be at an extra capital cost. Also, it will necessitate frequent maintenance which will escalate the operational and maintenance cost.

Sri Lanka has had the bad experience of acquiring a GT plant designed for one type of fuel and operating it with another. This was the Fiat GT acquired some years back on an emergency basis. Generally, GT or CC power plants are not available off the shelf and they need to be ordered months or years ahead. According to media reports, Sri Lanka purchased this plant because that was the only plant available at that time disregarding the fact that it was meant to operate with Natural Gas. What happened to it after operating it with auto diesel oil is now history.

The fact remains that the most suitable fuel for GT operation is natural gas (NG). This is the cleanest fossil fuel available with no sulphur to emit sulphur dioxide or ash to emit particulates.

The emissions of both carbon dioxide and oxides of nitrogen are much less than those emitted by oil-fired CCGTs. Hence, today the preferred fuel world over for firing CCGTs is NG. The Shenzhen Power Plant which MP referred to operated initially with HFO as that was the fuel available 20 years ago at that site. Also, at that time there was no concern about the impact on the environment and only economics were of importance. Recently, China commissioned its first LNG terminal near Shenzhen to deliver NG brought from Australia. With the availability of NG, China is now planning to switch fuel from HFO to NG in the Shenzhen plant for which China is seeking funding from developed country parties in exchange for carbon dioxide saved in the process, under the Clean Development Mechanism of the Kyoto Protocol.

There have been media reports recently of authorities considering import of LNG to Sri Lanka to operate GT power plants. This should be given the highest priority enabling switching of existing GT power plants as well as proposed plants to NG operation.

There is now technology available to build off-shore terminals at one tenth the cost of conventional terminals. The high cost of the latter and the low demand has been the barrier for importing LNG in the past. With the increase in demand, both in the power sector and in other sectors such as transport and industry, and the availability of low-cost off-shore terminals there is a case for inviting proposals for the building of the necessary infrastructure and negotiate with suppliers to obtain the best terms on a long term basis for Sri Lanka to have the benefit of this clean source of fuel.