PCC and oxy-combustion hold greatest promise in carbon capture

A slipstream from AEP’s Mountaineer plant has been fitted with Alstom’s chilled ammonia CO2 capture technology Source: Alstom

Alstom has conducted an extensive review of the possible technologies for carbon capture and Philippe Paelinck, Director CO2 Business Development at Alstom Power, explains why the company sees post-combustion capture (PCC) and oxy-combustion as having the greatest economic viability.

The Global CCS Institute (GCCSI) has published its annual review on the ‘state of play’ of carbon capture and storage (CCS) activities and projects across the globe. The report’s key findings indicate governments and industry remain in the early stages of implementing large-scale international programmes that would shorten the time frame for the commercial deployment of CCS. The focus of these programmes remains on the demonstration phase for developing and improving capture and for proving the safe and secure long-term storage of carbon dioxide. The report believes that this demonstration phase is likely to last for at least a decade.

According to the report, governments worldwide have to-date committed support to 25 large-scale projects. Encouragingly, the amount of government funding allocated to individual projects also increased in 2010. In total, governments have made commitments valued at $40 billion in support of CCS demonstration projects, with close to $12 billion of that allocated to specific large-scale demonstration projects. By the end of last year 234 CCS projects were active or planned across a range of technologies, project types and industrial sectors, i.e. power generation, steel, iron, cement. The total represents a net increase of 21 projects from 2009, and includes 77 large-scale integrated projects.

One technology provider particularly active in CCS for the power sector is France’s Alstom Power. The company has significantly invested in developing carbon capture technologies and is currently working with partners on several pilot and demonstration projects including E.ON’s Karlshamn in Sweden; Vattenfall’s Schwarze Pumpe facility (oxy-combustion); Total’s Lacq project in France; and American Electric Power’s Mountaineer plant in the USA. In the last two projects, the CO2 is not only captured but stored. An update on the Mountaineer project can be found in the boxed text on page 94.

Here, PEi talks to Philippe Paelinck, Director CO2 Business Development at Alstom Power, about his company’s CCS technologies and activities, and finds out why Alstom sees post-combustion capture and oxy-combustion as having the greatest economic viability.à‚ 

PEi: If a Europe-based utility wanted to build a new 1500 MW coal fired power plant incorporating carbon capture technology, which technology would be the most cost-effective option?

Philippe Paelinck of Alstom Power

Paelinck: For producing power, integrated gasification combined-cycle (IGCC) is not the right answer. This technology has a very high capex, about twice that of a conventional coal plant, and that’s without carbon dioxide capture. Moreover, it is not as flexible, available or efficient as a state-of-the-art pulverized coal (PC) plant. So IGCC is already a shaky and expensive proposal, and that’s before any CO2 capture consideration. We would therefore discard this option upfront. If the utility’s plan is to go full capture from commissioning day, say in 2015, our recommendation today would be to go for an oxy-combustion plant. Our cost estimations show that this option is likely to be the most cost-competitive starting 2015.

The technology is also technically robust. Cryogenic air separation is a fully proven and industrially mature technology, available at very large-scale from several industrial gas companies. As demonstrated in our industrial pilot units, the boiler design and operation is pretty straightforward, and we have seen no major technology hurdles.

The boiler can also be made so that it will operate both on air and oxygen, minimizing the investment risks. All downstream CO2 gas processing unit equipment parts are commercially available. Even if such a large CO2 compression train has never been built to date, we feel we have the tools and resources to design, construct and operate it successfully.

If its plan, however, is a progressive ramp-up of the capture capacity, then post-combustion is certainly a better approach. This is clear from the choices already being made by utilities when responding to EU CCS calls: post-combustion is largely favoured as a partial capture solution on a bigger plant. This reduces the financial risk. One could easily imagine the progressive deployment of up to five 300 MWe post-combustion capture trains on the back of the 1500 MW coal fired power station, progressively abating the CO2 emissions as legislation and incentives will arise.

While slightly more expensive than oxy-combustion in 2015, our cost study has outlined the stronger than expected learning curve for post-combustion. Indeed the capture component of post-combustion CCS is less mature than oxy-combustion and has therefore more potential for fast progress in the early initial years.

PEi: What would be your recommendation be if the utility wanted to retrofit carbon capture technology to a 20-year-old coal fired power plant?

Paelinck: Pre-combustion cannot be retrofitted to an existing plant. This technology applies to new build only. Both oxy-combustion and post-combustion can be considered for retrofit, but there is a key advantage of the latter: if the space is available you can build your capture system while continuing to operate your plant. For oxy-combustion, on the other hand, you need to stop your boiler to make it airtight and oxy-compatible. This would give a key financial advantage to post-combustion in most cases. For post-combustion, a partial capture solution can also be considered.

We do, however, have experience in oxy-retrofit from the Lacq pilot, where Total has asked us to revamp a 50-year-old existing 30 MW fuel oil boiler to oxy-combustion. Technically, this presented no problem and the unit was commissioned early 2010 and has been operating well since then.

For a retrofit, each case can be different and economic studies must be performed to assess the best option. Again, stopping a power plant for six months to retrofit the boiler is an expensive option. But one could also think of building a new oxy-boiler on the side of the existing one: this reduces the shutdown time considerably and allows for the use of the same power block. This is the option chosen by Vattenfall for their Jàƒ¤nschwalde project. So, there is no generic answer: each case will see a different solution.

 

Chilled ammonia is seen by Alstom as its most robust and energy efficient post-combustion CO2 capture technology

PEi: How do the economics of post-combustion capture technology compare between developed countries and the developing world?

Paelinck: There are several key differences highlighted in our study, where we are comparing CCS cases in Europe, North America and Southeast Asia (SEA). Factors like cooling temperature, coal quality, debt and equity cost and EPC costs are the main drivers of those differences.

The strong influence of cooling temperature was a surprise to us. In our study we have assumed a 13 à‚°C direct cooling temperature in Europe versus 28 à‚°C in SEA. We found, for instance, that this parameter was more penalizing to oxy-combustion than to advanced amines post-combustion.

Globally, however, those parameters often act in balancing directions and we have seen no striking differences between regions, other than an expected lower cost for developed countries because of the lower overall EPC costs.

PEi: Alstom offers two post-combustion capture technologies ” chilled ammonia and advanced amines. Why the two-pronged attack? When would one process be favoured over the other?

Paelinck: We believe that securing an excellent post-combustion solution is a must for our business. Post-combustion is the most readily retrofittable solution and also the current sole option to abate CO2 on the back of a combined-cycle gas turbine (CCGT) power plant.

The technology is also adaptable to many industrial processes. We have therefore based our R&D roadmap both on the already industrially proven amine-based technology but also on a novel, breakthrough technology based on chilled ammonia.

This strategy was aimed at giving us certainty in securing a credible solution, while also advancing on a promising pathway with an alternative technology. Today, our pilot results show that each technology will find its natural market niche.

While the chilled ammonia process is more robust and more energy efficient, its capex is also higher than for the advanced amines solutions, and the technology also has stronger sensitivity to cooling conditions. Large-scale validation will be needed to determine the optimum operating boundaries for each technology.

 

Alstom expects oxy-combustion to be the most cost-competitive CO2 capture option from 2015

PEi: China’s CCS capability and expertise appear to be growing rapidly. Do you see this as a threat to Europe’s CCS leadership role?

Paelinck: China is indeed showing a strong interest in developing indigenous CCS technology. They are progressively catching up with Europe or North America in terms of industrial pilot experience, and could very well be the first to demonstrate CCS at large-scale, with the start-up of the GreenGen project.

China is by far the biggest coal power market, and in the next five years we expect about 60 per cent of new power plant orders to be in Asia, while half of that growth will be based on coal.

If Europe and the US do not move immediately to create market perspectives for decarbonized coal solutions, coal expertise, including CCS technology, will be completely transferred to Asia in the next two to three years. That movement has already started and it’s accelerating with the current continued political indecision faced by the industry. Within five years there will then likely be no choice but to import coal know-how, technology and EPC capability from Asia.

PEi: One criticism of carbon capture, in particular pre- and post-combustion, relates to their plant efficiency penalty, commonly seen as 10 per cent. How much can this loss be reduced and in what time frame?

Paelinck: First of all, let’s be clear on the efficiency penalty expressed as pure percentage and the loss expressed as percentage points. The 10 per cent mentioned above are net percentage points, i.e. a power plant with a 40 per cent efficiency, with the addition of CCS would see its performance reduced to 30 per cent efficiency; this could also be accounted as a 25 per cent loss. This is indeed the starting base for capture systems today. We believe that the first commercial units in 2015 will be already below 8 points of efficiency loss, and the learning curve will bring us to 6 points by 2030. Beyond that point, breakthrough technologies like Chemical Looping Combustion will be needed, knowing that the thermodynamic limit is probably in the vicinity of 4 points of efficiency loss.

PEi: Pilot and demo projects are now demonstrating the effectiveness of capturing carbon dioxide, so how important is it now for the focus to shift towards demonstrating the whole process chain?

Paelinck: Alstom and its partners have already demonstrated the full capture and storage chain. Both our pilots with AEP in West Virginia and with Total in Lacq are capturing and storing CO2 at a rate close to 100 000 tons/year each (907 000 tonnes/year). There are many other examples demonstrating the full value chain. The challenge is no longer to show that this is possible, but to scale the technology to full commercial size and start to deploy it commercially. That process is entirely dependent on the policymakers, the industry has already done most of its part.

PEi: Alstom has said it can bring commercial-scale CCS to the market by 2015. Will power utilities be ready to embrace it, given uncertainty in climate change policy and the need for stronger regulatory frameworks?

Paelinck: The power utility industry will deploy the technology when there is a market reason to do it. Today there is no market, and despite large funds made available for large-scale demonstration in both the US and Europe, the projects are not taking off. When there is no market, even a 50 per cent funding is not enough. Would you buy a car at half price if there was no road to drive it on?

US Mountaineer project: Positive results

Results look promising from the first phase of the demonstration project at AEP’s Mountaineer plant in New Haven, WV, USA, which is described as the world’s first facility to both capture and store CO2 from a coal fired power plant.

In 2009, a slipsteam (20 MWe portion) of the AEP’s 1300 MW Mountaineer plant’s exhaust flue gas was retrofitted with Alstom’s patented chilled ammonia CO2 capture technology. Its results achieved include:

  • Capture rates from 75 per cent (design value) to as high as 90 per cent;
  • CO2 purity of greater than 99 per cent;
  • Energy penalties within a few per cent of predictions from the process simulation model;
  • CO2 injection levels of approximately 7000 tons/month (the equivalent of taking 17 000 cars off the road);
  • Robust steady-state operation during all modes of power plant operation, including load changes; and
  • Availability of the CCS system greater than 90 per cent.

The first phase of the CCS project began capturing CO2 in September 2009, and started storing it in October 2009. The plant will continue to operate until the end of June this year, with a focus on maximizing CO2 injection.

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