The world’s first pilot plant for the capture of carbon dioxide in a coal-fired station has commenced operations at the eastern German power plant Schwarze Pumpe. From 2020, the lignite power producer wants to use his Oxyfuel technology in a large scale commercial power plant. 10/2008

When the weather is good the lignite-fired power station Schwarze Pumpe in Lusatia, eastern Germany, can be seen from a long way off. The two gigantic cooling towers of the large power station with a capacity of 1,600 MW throw out thick white clouds of steam into the clear blue sky. These clouds contain large amounts of the greenhouse gas carbon dioxide: The power station puffs out 12 million tons of CO2 a year into the air. The company Vattenfall Europe AG (VE), which owns the power plant, produces a total of 70 million tons of CO2 per year. CO2 is the last remaining pollutant which is still produced in significant quantities by the eastern German lignite power stations built by VE towards the end of the 1990s. Until now there has been no market-ready technology capable of separating and also safely disposing of the CO2. VE and its Swedish mother company, Vattenfall AB, expect that a long timeframe will be required to solve this problem: By 2050 they want the power produced by their power plants to be completely CO2 neutral.


To achieve this they are relying heavily on a pilot unit which VE has built in the last two years at a cost of €70 million right beside the power station Schwarze Pumpe. According to the company this is the first pilot plant in the world for a coal-fired power station with CO2 capture. It has a thermal capacity of 30 MW and works with Oxyfuel technology. In this process lignite is not burnt using the air from the surrounding environment as has typically been the case until now, but rather using a mixture of pure oxygen and recycled flue gases. Following various stages of purification the flue gases are converted into a highly concentrated CO2 which can be liquefied, transported and stored in underground reservoirs.

 


99 percent of CO2 will be captured


The opening of the plant has obviously been successful. ‘Last Thursday at 4.50 pm our engineers have for the first time managed to capture carbon dioxide in this plant,’ reported VE chairman Tuomo Hatakka at the official commissioning of the plant on September 9. ‘This first test run has already been very successful.’ Hubertus Altmann, head of the engineering department, calculates that a 99% rate of capture has been achieved. Altmann announces, ‘Of course this is the yardstick for measuring our future performance.’


In the coming months, Hatakka wants to bring the whole chain of carbon capture and storage (CCS) into operation. It is planned to transport the 60,000 to 100,000 tons of CO2 captured from Schwarze Pumpe by tanker truck to a gas storage depot 350 km away in the Altmark region and to store it there. VE plans to bring the joint storage program with Gaz de France there into operation in March 2009. There is also a further joint agreement with Linde in which the CO2 will be used as an engineering gas. ‘The pilot plant has been set up for a CO2 purity of 99.7%,’ says Reinhardt Hassa, chairman of VE Mining and Generation. ‘This meets the quality requirements for engineering applications.’ In the industry, CO2 is utilized as a fertilizer, a cooling agent, for cleaning purposes and as dry ice. It is also used in fire extinguishers. If required, the pilot plant still has a chimney through which exhaust gases can be released into the atmosphere in the traditional manner. VE have put the cost of the five year research trial of the pilot plant at €20 to 30 million.


In addition, between 2012 and 2015, the company intends to build a demonstration power plant using CO2 capture with a capacity of 300 to 500 MW, at the Jänschwalde power station costing up to €1 billion Euro. The plans there are to use Oxyfuel technology in one boiler. In a second boiler so-called post-combustion technology will be used. While Oxyfuel works well in new power plants and achieves a high degree of capture, post-combustion makes it possible to upgrade existing power plants with carbon capture. Hassa predicts that the first power stations to be equipped with this technology will be able to achieve a capture rate of 85 to 90%. However, he believes that this may be improved upon later.


Furthermore, the Vattenfall Group is planning two additional post-combustion projects in Denmark and Norway: By 2013 the Danish bituminous coal-fired power station Nordjyllandsvaerket will be upgraded with this technology which will provide it with a capacity of 300 MW. In northern Jutland Vattenfall is also investigating possibilities for CO2 storage. In the Norwegian refinery Mongstad, Vattenfall is also participating in a research project in which two different post-combustion technologies are being tested.


With Oxyfuel technology VE anticipates being able to reduce the CO2 emissions which occur during power production from over 900 to way below 100 grams per kilowatt hour. The downside of this progress is the high use of energy leading to a 10% loss in electricity efficiency for a lignite-fired power station. The investment costs will also increase dramatically. Altmann however assumes that by 2020 the loss of efficiency will be counteracted through the use of efficiency increasing measures such as lignite pre-drying and higher steam temperatures and pressures. By then VE will be ready to use Oxyfuel in a large scale commercial power station. Altmann also sees possibilities for the reduction of the amount of energy used in the Oxyfuel process, ‘We will again be able to achieve efficiency rates of significantly more than 40% with the types of power plants which will come after the demonstration units.’

 

 

A question of economic viability


There is still a question mark beside the economic viability of Oxyfuel. The chairman of Vattenfall AB, Lars G Josefsson, estimates the CO2 costs at the Jänschwalde demonstration unit will be from €80 to 90 per ton. Because this is completely uneconomic, Vattenfall needs public funding. In a commercial power station which VE has planned for 2020, the CO2 costs are expected to be reduced to €30 to 35 per ton. As far as the effect of CCS technology on power prices is concerned, Josefsson has made differing statements, ‘If CCS technology is economic, that is competitive, then the CCS costs will be lower than the market price of emissions certificates. This means that CCS will not lead to an increase in power prices. If CCS becomes too expensive, then we won’t use CCS.’ Later he admitted that the price of emissions certificates could also increase to enable the introduction of CCS, ‘but in 10 years there will be new technologies, and of course we’ll be smarter with CCS technology. It will be a race.’


This race could also lead to the white steam clouds over Schwarze Pumpe containing less CO2 in the future. ‘If the technology exists, and if it is economic and can be financed at market rates,’ says Hassa, ‘then the day will come when power plants with sufficient remaining operating life will be upgraded.’




The Oxyfuel process


Instead of being combusted with air, the coal is fired in an environment of pure oxygen and recirculated flue gas. A share of 75% of the carbon dioxide produced is then fed back into the boiler during the power plant operations. In the subsequent treatment steps the dust and sulphur compounds are removed from the flue gas stream as in conventional power plant operations. Finally, the remaining steam is condensed out, so that the flue gas, with approximately 98% CO2 concentration, remains. The CO2 is then liquefied on site or compressed so that it is suitable for transportation purposes, and transported by tanker truck or via a pipeline.