Three diesel engine plants in the city of Manaus, Brazil, are being converted to allow them to run on natural gas. The projects being undertaken by Wärtsilä will allow the plant owners to optimize the operation of the plants according to the price and availability of fuels, as well as take advantage of a more environmentally sound alternative.

Brazil’s installed power generating capacity stands at just over 100 GW. This power feeds into an interconnected grid that extends over a geographical area that is almost the size of Europe. More than 80 per cent of the country’s installed capacity is generated from hydro resources.

Companhia Energética Manauara is converting its power generators in Brazil to gas as the fuel becomes available in the region.
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In 2005 Brazil began the process of increasing capacity, while reducing its dependency on hydro, with the introduction of online auctioning for new capacity. This is a transparent system that sees a number of online energy auctions every year for bids on capacity to be delivered in either three or five years hence – a timeframe that rules out the construction of large hydropower projects.

Following the initial auctions, which were for power from existing plants, subsequent auctions have been for new plants, many of which were thermal and based on heavy fuel oil. The recent auctions reintroduced gas power plants as more such fuel has become available. In addition, there are auctions for power produced by alternative energy sources, such as wind and sugar cane.

The amount of new capacity installed each year depends on the amount of capacity being auctioned but the process sees the start-up of a number of new independent power producers (IPPs) each year.

Wärtsilä sold nearly 800 MW of capacity in the 15 years between 1990 and 2005. A large portion of this was a 3 x 85 MW plant installed in Manaus between 2005 and 2006. Since then, Wärtsilä has sold close to an additional 1 GW as the spin-off of just one auction. This new capacity is scheduled to enter commercial operation in January 2010.

Need for flexibility

The auction process combined with an increasing availability of gas means fuel flexibility is important to the IPPs. IPPs want to build power projects that can run on whatever fuel is available at the time of construction but can later enjoy the economic and environmental benefits of being able to switch between gas and fuel oil when all fuels are available. Wärtsilä engines are proving to be popular in this scenario.

Although operators are able to install dual fuel engines from the start, some opt for heavy fuel oil (HFO) engines and convert them to run on gas at a later date. Wärtsilä has had success with all of its engine types – pure gas, dual fuel and HFO. The availability of fuel and application determines the technology used. For example, HFO engines are used for standby applications, since here capital cost is the driver as opposed to long-term fuel efficiency.

In January this year, Wärtsilä received contracts from three Brazilian IPPs to carry out conversions to their generating stations.

Gas conversion is timed to coincide with regular maintenance work..
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The three IPPs – Geradora de Energia do Amazonas S/A, Companhia Energética Manauara, and Rio Amazonas Energia SA (a part of Multiner S/A) – all have power plants located in Manaus city. All indicated a desire to be able to use all possible fuel alternatives in the future, for environmental as well as for redundancy reasons, and to take advantage of lowest fuel cost options. The key driver, however, has been the anticipated availability of natural gas to the region in 2010. The gas conversions will be carried out in all three power plants concurrently.

The three power plants each have five Wärtsilä 18V46 engines, giving a total power output of more than 85 MW at each plant. When the three plants were delivered in 2006, gas was not available. However, they were pre-designed to facilitate the conversions that will enable them to switch from their current baseload HFO operation to gas operation. Wärtsilä currently operates and maintains all three plants under contract, and will thus continue to ensure their optimum performance and reliability after the conversion.

From fuel oil to gas

Conversion of an HFO installation to operate on natural gas involves changing some components on the engine. The number of components changed will depend on the age of the engine. However, the main change to the engine is the addition of a new gas feed system along with the engine control and monitoring system. Plant conversion consists of modifications to gas handling systems and the control system.

Wärtsilä has three types of gas conversion technologies: gas diesel; low-pressure natural gas and duel fuel. The Manaus plants will undergo gas diesel conversions. Gas diesel is based on high-pressure natural gas injection in the diesel cycle, which means that engine modification is limited to the injection equipment and control systems.

The resulting engine is a dual fuel engine designed to operate in two fuel modes. In liquid fuel mode, light fuel oil (LFO), HFO or crude oil is used as the main fuel and the engine works as an ordinary diesel engine. In gas fuel mode, natural gas is the main fuel ignited with a small amount of liquid fuel. The engine uses the direct gas injection technique.

The Wärtsilä 18V46 engines prior to conversion have a single feed system located at the top of the engine for feeding the liquid fuels (HFO or LFO). But since the conversion, these engines need a small amount of pilot fuel, the liquid fuel feed is kept at the top of the engine and a gas feed is added. This means two injectors are needed in the cylinder head. The two fuel feeds mean that the engines can run on gas and/or liquid fuel, depending on how much gas is available.

One drawback with the gas diesel engine, however, is that they require high-pressure gas, around 350 bar. This means a compressor is needed to boost the fuel pressure from as low as 20-40 bar. The gas compressor section is expensive but the cost can be offset by the ability to switch fuels.

The gas fuel system is designed to supply the gas diesel engines with clean gas at constant pressure, temperature and pressure. The main components of the gas fuel system are a gas compressor skid, buffer tank, valve station, interconnecting piping and double wall ventilation system.

Three fairly large gas compressors will be installed at each plant – two in operation and one on standby. The gas compressors will also need all of the associated automation and electrical supply systems.

Smooth progress

The main challenge in performing the conversion will be minimizing the impact on plant operation. The conversion work will therefore be timed to coincide with regular maintenance work, that is when the engines are stopped for the 24-hour overhaul.

The installation of gas pipelines involves welding and pulling cables, and so on. One of the main challenges therefore is coordinating site activities, essentially balancing plant operation with the conversion work so that both can go smoothly.

IPP Geradora de Energia do Amazonas has embraced the potential of alternative fuels.
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The engines will be converted one at a time to keep plant downtime to a minimum. The gas systems will be built while the engines are running on HFO and then swapped over as gas becomes available.

According to the power purchase agreements, each plant is contracted to deliver 60-65 MW. This means four out of the five engines at each plant are operational, with the fifth engine kept for standby operation. This allows smoother conversion, since the conversion can be carried out on the standby engine.

With a combined value in excess of €48 million ($64 million), these combined plant conversions represent the biggest project of its kind ever undertaken by Wärtsilä Services. The size and scope of the project, together with the fact that the work is to be carried out at three separate sites, means that it is an interesting challenge.

Wärtsilä in Brazil has set up a project management organization to best organize the human and parts logistics to ensure the delivery meets the contractual terms.

Moreover, Wärtsilä maintains the same guarantee of availability in the service agreements, both before and after the gas conversion. This underlines and demonstrates the confidence in, and reliability of, the provided solution.

So far the project is progressing smoothly. The majority of the engineering has been completed and most of the heavy long-lead items have been procured. This year, civil works will be completed, equipment deliveries will begin, and the control systems will be installed.

The three projects are very similar, and all the owners have similar power supply commitments. Although there were three separate contracts, this enabled Wärtsilä to design the plants to be almost identical to each other and coordinate equipment deliveries. For example, the operating compressors will be shipped first, followed by the standby compressors.

Most of the gas compressors will leave the Wärtsilä factory by late this year in order to arrive and be installed early next year. The last compressors will leave the factory early next year and arrive in March 2010. The compressors will be factory tested before shipping and undergo pre-commissioning and commissioning at site before full system testing.

Gas pipelines are now being constructed and gas will be available in 2009/2010. This will allow pre-commissioning of the first units to start during the second quarter of 2010. The first units will be commissioned early in the year and the plants will be fully operational in October 2010.

Wärtsilä is at the forefront in the development of multi-fuel engine technology, and when the conversions are completed, the engines will be fully compliant with the flexibility requirements, allowing the fuel to be switched instantly from liquid to gas, or vice versa.

Brazilian plants on the increase

Wärtsilä set up its office in Brazil in 1990. Since then the requirements of the Brazilian power market have seen this operation expanded to cover turnkey projects and after-sales services, in addition to sales and marketing.

Despite the global financial crisis, Brazil’s economy is stable. Inflation has been kept under control during the past ten years and economic growth has continued. The economic situation combined with the diversification away from hydro and the need for flexible baseload, has seen the rapid growth of engine-based plants.

For example, in August 2008 Wärtsilä received a significant order from a Brazilian energy consortium for a power plant project called Geramar, representing two plants on the same site. The order followed three others signed earlier that year. The four orders received by Wärtsilä in 2008, together with other Wärtsilä plants already in operation in the country, will produce a combined generating capacity of about 1800 MWe. The contract took the number of power plants designed, undertaken and installed in Brazil by Wärtsilä to 21.

The Geramar 1 and 2 power plants are to be located in Miranda do Norte, a city of 15 000 inhabitants in the Brazilian state of Maranhao.

Following an energy auction held by the Agência Nacional de Energia Elétrica (National Agency of Electrical Energy) in July 2007, Geramar was contracted to provide flexible power production for 36 distribution companies as standby power for hydro generation. Since Brazil produces its own oil, domestic fuel can be used to cover the energy gap during these critical energy supply periods when there is insufficient water for hydro generation. The Geramar plants are expected to be operational for approximately 2000 hours per year between December and April, when water reservoirs are low.

The turnkey contract calls for a full engineering procurement and construction project consisting of two plants, each with 19 Wärtsilä 20V32 engines giving a total output of 331 MW. The plants will run on low-sulphur heavy fuel oil. Construction began in early November 2008, and the plants are scheduled to be fully operational before the end of 2009.

At present, Wärtsilä has installed just under 800 MW in Brazil and this will reach 1.8 GW by 1 January 2010.