Duke Energy's Edwardsport IGCC

The increase in gasification capacity in the last few years has been remarkable. Since the Gasification Technologies Council (GTC) last update to its worldwide database of gasification plants in 2010 the number of operating gasifiers has increased from 505 in 192 projects to 618 in 234 projects. In addition another 202 gasifiers are under construction and over 500 in planning. The thermal output capacity of all gasifiers operating and under construction has risen from 82 GWt to 168 GWt with a further 84 GWt in planning. In contrast to previous issues of the database the "in planning" number has been modified by a project realisation probability so as to keep the projections for the next few years at a realistic level. The bulk of this expansion is in the Chinese coal-to-chemicals industry, which is growing at a similar rate to most other sectors in that country.

IGCC developments

While the number of planned IGCC-based power projects has dropped dramatically from the 2008-2010 database projections, solid progress has been made with the start-up of Duke Energy’s Edwardsport 618 MW power station. The plant entered commercial service in June 2013. The most important issue to be watched at this plant is how the lessons learned from the 1990s generation of IGCC units have been implemented to improve availability – both in terms of time-to-maturity and long-term performance. Duke is expecting a 15 month bedding-in period after the commercial operation date during which a 75% availability is anticipated. This is planned to increase to 85% thereafter.

The other US IGCC plant under construction is that of Mississippi Power in Kemper County. This lignite-fired plant will produce 524 MW, net of the power requirements for 65% carbon capture. Parts of the plant have already been started up, while remaining piping and instrumentation work continues. Both Siemens SGT6-5000F combustion turbines have been fired on natural gas. Nonetheless it is anticipated that there will be some slippage on the originally scheduled commercial operation date of May 2014.

"Both Edwardsport and Kemper have been plagued by cost overruns. Much of this has been attributed to construction costs."

Both Edwardsport and Kemper have been plagued by cost overruns. Much of this has been attributed to construction costs. However when one sees the number of planned projects of all sorts based on the availability of cheap shale gas in the United States (ethylene plants, ammonia fertiliser and methanol plants, NGCC power plants and a GTL project), then one has to be concerned about the cost and availability of construction crews for all this work. (Until very recently there were two GTL projects planned but Shell’s Gulf Coast facility in Louisiana has been cancelled, principally because of cost escalation worries.)

Permitting and financing remain the keys to two other IGCC projects in the United States – the Texas Clean Energy Project (TCEP) and Hydrogen Energy California (HECA), both of which plan to generate power alongside fertiliser and both of which will use CO2 for enhanced oil recovery (EOR).

The flexibility of the HECA concept of switching between power production and fertiliser production to accommodate the daily power demand cycle was described in last year’s report. There was considerable discussion during the breaks about the possibilities of enhancing this concept to meet rapid demand changes originating from the large-scale use of intermittent power sources such as wind and solar energy. EPRI has been working on such a concept for the last year, including looking at using the new generation of rapid response combustion turbines. EPRI’s report has now been published (Design options for enhancing IGCC flexible operations, performance and economics, EPRI, Palo Alto, CA, December 2013, Report #3002001052), and demonstrates the potential for an IGCC to exploit the ramp rates of these newer machines. The Buggenum IGCC plant had already shown how station ramp rates can be enhanced over syngas production ramp rates by the temporary use of natural gas to boost the CT output. It was surprising how little natural gas is required to allow the syngas production to catch up with rapid response turbines – even using existing technology. With some improvements, particularly in controls, the natural gas ‘spike’ can be reduced even further.

Developments in China

The rapid development of a gasification-based coal-to-chemicals industry in China…has had its effect not only on the demand for gasification technology, but also on the supply side, with more home-grown technologies in China.

The rapid development of a gasification-based coal-to-chemicals industry in China was referred to earlier. This has had its effect not only on the demand for gasification technology, but also on the supply side, with more home-grown technologies in China. Reports on the East China University of Science and Technology (ECUST) gasifiers have become a regular feature of the conference. Two new projects with two gasifiers each were taken into service during the year. One of these, for Shanghai Coking and Chemical Corporation, was ECUST’s largest gasifier yet, rated for 2200 t/d coal feed. Three 3000 t/d gasifiers are under construction for Meilong Rongxin near Ordos and are due to start-up in the coming year.

Another Chinese university that has started to license gasification technology is Tsinghua University in Beijing. Tsinghua has developed two concepts that differentiate its technology. The first is oxygen staged gasification (OSG), with the first 500 t/d gasifier to employ this concept starting up in 2006. In contrast to conventional two-stage gasifiers such as E-Gas or Mitsubishi, which add coal to the second stage to improve efficiency, the Tsinghua OSG gasifier supplies oxygen in two stages. The claimed advantages are a longer life for the feed injector, attributable to lower temperatures local to the injector, and improved carbon conversion, which is attributed to improved turbulence and mixing at the secondary oxygen injection point. Tsinghua’s second concept is to use a membrane wall in combination with a slurry feed. Although always a technical possibility, this is the first gasifier to implement such a combination. Tsinghua has put considerable effort into optimising various mechanical design details and a fail-safe natural circulation for its water wall. The result is a remarkable 16 projects awarded in the September 2012 to September 2013 period as well as two contracts to retrofit existing refractory-lined gasifiers with a membrane wall.

Despite these very competitive local offerings, Western technologies continue to do well in China also. CB&I, new owners of the former ConocoPhillips E-Gas technology, announced a 2+1 train gasification plant for the CNOOC refinery in Huizhou. SES reported on the successful start-up of their 2+1 gasifier methanol plant at Yima. This represents a significant step forward for their U-Gas fluidised bed technology, being the first time that it has been up-scaled to 1200 t/d feed at 10 bar. GE also reported on a further start-up in China.

Substitute natural gas (SNG) in Asia

For many years the Dakota gasification SNG plant was unique in manufacturing methane from coal on a large scale. Within North America, with natural gas prices at about 4 $/MMBtu, it is likely to remain so. But elsewhere in the world, where the alternative is not cheap shale gas from the pipeline, but imported LNG in the 12-15 $/MMBtu bracket, the situation is different. And thus SNG is seeing something of a revival. The first new plant to come on stream was Datang’s Keqi 4 000 000 Nm3/day plant, which started up at the end of last year.

At the conference POSCO provided a construction progress update on its own 500 000 t/a SNG plant at Gwangyang, South Korea. Commissioning is due to start in early 2014 with commercial operation scheduled for the year end.

"Reliance Industries’ Jamnagar project…is one of the world’s largest gasification projects, processing 9.8 million t/a petroleum coke from the adjacent Reliance refineries."

SNG is also part of the product slate for Reliance Industries’ Jamnagar project. This is one of the world’s largest gasification projects, processing 9.8 million t/a petroleum coke from the adjacent Reliance refineries. This is like POSCO’s facility in that it is a liquefied natural gas displacement project. As well as SNG to fuel existing refinery heaters, the products will be syngas to fire existing and new combustion turbines, hydrogen for the refinery and carbon monoxide for a new acetic acid plant. The five air separation units, with a capacity of 5250 t/d each, will be supplied by Linde and will be the largest ever built. Construction started in April 2013 and start-up is scheduled for mid-2015.

Biomass and waste gasification

Over the last few years there has been more space in the GTC programme devoted to biomass and waste gasification. AlterNRG gave an update on construction progress at the Air Products Tees Valley site, where the 50 MW waste-to-energy project, employing Westinghouse plasma gasification technology is due to go on stream in 2014, with a repeat project planned adjacent to it (see p 27). Although the largest, Tees Valley is by no means the only plant using this plasma technology. A hazardous waste gasification plant recently started up at Pune, India, a demonstration hazardous waste gasification plant is under construction in Shanghai and a plant to gasify biomass was commissioned in Wuhan earlier in 2013.

Metso reported on the start-up of the 160 MWt waste gasifier in Lahti, Finland and a 140 MWt biomass gasifier at Vaasa. The syngas from the latter is used directly to co-fire an existing coal-fired boiler and can displace between 20% and 40% of the coal used in the plant. Metso is also providing EPC services for the REPOTEC ("Güssing") gasifier at the GoBiGas project in Goteborg, Sweden. This plant, which is currently in start-up, will use biomass gasification to produce about 20 MW equivalent of bio-SNG.

Technology update

"The RTI 50 MW equivalent warm gas desulphurisation demonstration is close to completion of construction and the demonstration operation will commence early 2014."

Technology development is generally not something that can be accomplished in a twelve-month period, particularly if industrial-scale demonstration is involved. The RTI 50 MW equivalent warm gas desulphurisation demonstration is close to completion of construction and the demonstration operation will commence early 2014. In presenting the current status RTI noted that the project is "well within budget". The thermodynamic attractions of this concept been have recognised for many years. If this demonstration goes well this technology could help bring down the costs of IGGC.

Another major development project is the Aerojet Rocketdyne (formerly Pratt & Whitney Rocketdyne) Compact Gasifier together with its linear mechanical feeder. A first round of trials with the 400 t/d demonstration feeder has been completed. Necessary modifications have been made and long-term testing is due to resume shortly.

At a more fundamental level, Kevin Whitty of the University of Utah presented intermediate results of a joint project with Stanford University to use tunable diode laser-based in situ monitoring of syngas composition and temperature. The harsh conditions in a gasifier make it very difficult to measure these values directly. This technology, which has been tested on the Utah pilot gasifier could be a way to overcome that difficulty. It was striking how the system provides a direct reading of gas composition without the typical 2 minute delay observable with conventional analytical equipment. This could make a contribution to the ‘rapid response IGCC’ discussed above.

This report by Chris Higman is based on the Gasification Technologies Conference 2013, Colorado Springs, USA, held on 13-16 October 2013.

The annual Gasification Technologies Conference is organised jointly by the Gasification Technologies Council (GTC) and the Electric Power Research Institute (EPRI).