Dry low emission
The amount of NOx produced depends on the combustion temperature. When the combustion takes place at a lower temperature the NOx emissions are reduced. Gas turbines with DLE technology were developed to achieve lower emissions without using water or steam to reduce combustion temperature (Wet Low Emission (WLE) technology). WLE technology demands cleaning of large amounts of water, is heavy, takes more space and can be difficult to install offshore. A DLE combustor uses the principle of lean premixed combustion, and is similar to the SAC combustor with some exceptions. A DLE combustor takes up more space than a SAC turbine and if the turbine is changed it can not be connected directly to existing equipment without considerable changes in the positioning of the equipment. The SAC turbine has one single concentric ring where the DLE turbine has two or three rings with premixers depending on gas turbine type. DLE technology demands an advanced control system with a large number of burners. DLE results in lower NOx emissions because the process is run with less fuel and air, the temperature is lower and combustion takes place at a lower temperature.
Background for the technology
Increased focus on environmental issues led to increased research on new and better gas turbines with water and steam cooling methods in the middle of the 1970s. The best technology could in 1980 reduce NOx emissions to 42 ppm and this was later reduced to 25 ppm. In the 1990s ammonium and catalysators was tested and late in the 1980s the turbine producers started to develop "Dry Low Emission-technology" (DLE) to be able to get around the technology that demanded water or steam injection. During the next ten years the DLE technology was developed and installed in many places leading to a reduction of NOx emissions less than 25 ppm. It is difficult to achieve less than 9 ppm NOx emissions with DLE turbines. To achieve a reduction from 25 ppm to 9 ppm more than 6 percent air must pass through the premixer. Newer generations of DLE burners have an extra injection leading to better control. Additional systems like "selective catalytic reduction" (SCR) are necessary to achieve emissions lower than 2.5 ppm. Technologies using water or steam (Wet Low Emission (WLE) can achieve approximately the same level of NOx emissions (25–42 ppm) when they lower the combustion temperature.
Use of DLE-technology in the world
This is not a complete list, but examples of where and when DLE technology has been implemented or are planned to be implemented.
- In Norway
DLE turbines were introduced offshore in Norway in 1998. All gas turbines installed offshore in Norway after year 2000 which uses only gas as fuel are DLE-turbines. The Kårstø facilities were planned with DLE technology. DLE technology is used by Statoil ASA, Hammerfest LNG. The Norwegian Storting has decided that the Gina Krogh platform shall not be equipped with DLE technology due to the fact that all off Utsirahøyden will have electrical power supplies from the mainland.
- In Europe
30 April 2012 a gas turbine generator with DLE technology was opened in Waidhaus in Bavaria in Germany.
- In America
In Alberta in Canada it was in 2003 planned to use DLE technology in the power supplies.
- In Asia
DLE is planned to be used in Australia. The Malampaya field in the Republic of the Philippines was awarded in August 1998, construction of the topside was begun in June 1999 and completed on 28 March. 2001. The topside was equipped with the worlds first RB211 with DLE technology.
- "Utslipp av NOx fra petroleumsvirksomheten på Norwegian sokkel, kap. 6.1.1". Oljedirektoratet. 10 July 2013. Retrieved 2014-07-12.[permanent dead link]
- Kristin Sundsbø Alne (June 2007). "Reduction of NOx Emissions from the Gas Turbines for Skarv Idun (Master of Science in Energy and Environment)" (PDF). NTNU. Retrieved 2014-07-12.
- Meherwan P. Boyce (2012). Gas Turbine Engineering Handbook. Elsevier. ISBN 0123838428.
- "Tiltaksanalyse for NOx Utredning av mulige NOx-reduserende tiltak innenfor energianleggene på sokkelen, innenlands skipsfart og fastlandsindustrien" (PDF) (in Norwegian). SFT. Retrieved 2014-07-13. [dead link]
- Haugan, Kari; Hjertaker, Vigdis; Gaarder, Karine; Kvande, Ingvar (November 2005). "NOx-reduksjon med vann-/dampinjeksjon" (PDF) (in Norwegian). NORGES TEKNISK-NATURVITENSKAPELIGE UNIVERSITET INSTITUTT FOR PETROLEUMSTEKNOLOGI OG ANVENDT GEOFYSIKK. Archived from the original (PDF) on 14 July 2014.
- Bord Gáis. "Sustainability in the Pipeline". Boston Scientific. Archived from the original on 23 July 2014. Retrieved 2014-07-12.
- Ronald Whiddon (1 April 2014). "Application of Laser-based Diagnostics to a Prototype Gas Turbine Burner at Selected Pressures (Academic thesis for the degree of Doctor of Philosophy in Engineering)". Faculty of Engineering at Lund University. Retrieved 2014-07-13.
- "Vedtak om tildeling av vederlagsfrie kvoter for perioden 2013–2020 til Statoil ASA Hammerfest LNG" (PDF) (in Norwegian). Klima- og forurensningsdirektoratet (Klif). 15 June 2012. Retrieved 2014-07-13.
- Roald Ramsdal – Lars Taraldsen (28 January 2014). "ELEKTRIFISERING AV UTSIRAHØYDEN Statoil måtte velge mer forurensende gassturbin på Gina Krog" (in Norwegian). Teknisk Ukeblad Media AS. Retrieved 2014-07-13.
Opprinnelig ønsket Statoil å forsyne Gina Krog med kraft fra to lavutslipps gassturbiner. Disse skulle vært utstyrt med såkalt DLE-teknologi (Dry Low Emission), som blant annet reduserer utslipp av NOx, går det frem av et forslag som operatøren la frem i januar 2012. I mai i fjor godkjente imidlertid Stortinget at plattformen kan drives av en løsning som vil gi langt større utslipp av NOx og dårligere driftssikkerhet. ... Årsaken til at kraftforsyningen på plattformen ble endret til en løsning som gir større utslipp, var for å få plass til nødvendig utstyr for at plattformen skulle kunne ta i mot kraft fra land. Turbinløsningen ble omtalt som "midlertidig" av Statoil. ... "Konsekvensen av å endre base case er økte utslipp av NOx frem til elektrifisering", skriver Statoil i en konsekvensutredning fra 2012.
- "Minister Zeil officially put into operation a new machine unit at Waidhaus (Press Release)". GRTgaz Deutschland. 30 April 2012. Retrieved 2014-07-12.
On April 30, the minister for economic affairs of Bavaria, Martin Zeil, has officially put into operation a new machine unit at the MEGAL compressor station at Waidhaus. ... Its dry low emission (DLE) combustion system ensures the currently lowest possible emission values of nitrogen oxides.
- Clean Air Strategic Alliance Electricity Project Team (November 2003). "An Emissions Management Framework for the Alberta Electricity Sector Report to Stakeholders" (PDF). Clean Air Strategic Alliance, CANADA. Archived from the original (PDF) on 4 March 2016. Retrieved 2014-07-13.
- "Australia Pacific LNG Project" (PDF). AUSTRALIA PACIFIC LNG PTY LIMITED. 2010. Archived from the original (PDF) on 21 February 2014. Retrieved 2014-07-13.
- "Malampaya, Philippines (World's heaviest offshore floatover topsides installation at project award)" (PDF). kbr.com. Archived from the original (PDF) on 2015-04-30. Retrieved 2014-07-12.
World's first use of Dry Low Emission gas turbines offshore
- "Malampaya, Philippines". offshore-technology.com. n.d. Retrieved 16 July 2014.
- "ASIA/PACIFIC: Commissioning underway on Philippines' Malampaya platform". PennWell Corporation, Offshore. 1 May 2001.
The topsides feature dry low emission gas generators, a world first for the RB211 units installed offshore.
- "Malampaya Topsides Installed in the South China Sea; Largest Integrated Deck in Asia Pacific". Halliburton Company. 28 March 2001. Retrieved 16 July 2014.
Dry low emission gas generators were specified. This is a world first for RB211's installed offshore.