World first: Turow 11, a lignite plant that meets BREF standards31 October 2016
Under a revised contract PGE’s new Turow 11 plant in Poland will be the first lignite fuelled plant to be equipped with a package of measures that will bring its emissions down to levels associated with “best available techniques”, as set out in the new BREF reference documents, currently being finalised. The BREF levels, which will underpin permitting of fossil fuelled power plants in Europe, are around half of the limits specified by the Industrial Emissions Directive, or less, and also include new requirements to limit mercury emissions.
PGE’s 496.1 MW (gross) Turow 11 plant in Poland will be “the first lignite-fuelled power plant in the world meeting the new BREF emissions standards” says MHPSE (Mitsubishi Hitachi Power Systems Europe), which is lead contractor, supplying the boiler, flue gas cleaning equipment, piping, turbine/generator and I&C, and which is also responsible for bringing the new unit on line. Budimex of Poland and Tecnicas Reunidas of Spain, working in consortium with MHPSE, are responsible for construction/erection, cooling tower (natural draft), general electrical engineering, steel structures, ductwork and some balance-of-plant.
The MHPSE scope includes a Powerise flue gas heat exchange system for prewarming of combustion air. The Powerise system, which is being provided by Bilfinger subsidiary Babcock Borsig Steinmüller under a 9 million euro subcontract, employs corrosion-free flue gas coolers, enabling heat exchange to continue below the acid dew point, contributing to high plant efficiency.
The Turow 11 power plant, employing local lignite as its fuel, is to be built on the existing Turow power plant site, which has six units, totalling 1500 MW of installed capacity, in operation.
The original order for Turow 11 was placed in July 2014 and the notice to proceed issued in December 2014. It was MHPSE’s second large power plant order in Poland, following that for ENEA’s Kozienice 11 hard coal fired plant, placed in 2012.
In June 2015, PGE (Polska Grupa Energetyczna, which is 58% state treasury owned) issued a change notification requiring Turow 11’s emissions performance to be improved in line with new EU-wide BREF standards.
A revised contract, incorporating a “BREF package” (including, for example, installation of SCR and mercury removal technology) was placed in November 2015 and a revised notice to proceed issued. Updated basic engineering documents reflecting BREF emissions levels were issued in March 2016. Overall, incorporation of the BREF package is estimated to have added about nine months to the project schedule, with commercial operation now slated for April 2020.
The new BREF (BAT reference document) emissions levels, which are designed to reflect those achievable with “best available techniques” (BAT), are estimated to be around 50% lower, or even less, for key pollutants, relative to the emissions limits set out in the EU Industrial Emissions Directive, itself representing a considerable tightening of limits compared with the previous LCPD regime. The new BREF levels will become the reference for setting permit conditions in Europe (binding, but with scope for derogation in certain circumstances), while the binding emissions limits set out in the IED, will act as a kind of safety net. As well as being more stringent, the new BREF requirements also consider new classes of pollutant, notably mercury, HCl, HF and ammonia.
In the case of Turow 11, the new BREF emissions levels (relative to IED) can be summarised as follows, as well as the measures incorporated in the revised plant design to achieve them:
- SO2, 150 mg/Nm3 down to 75 mg/Nm3 (dry@6%O2) Flue gas desulphurisation system modifications: increase of liquid-to- gas ratio, change in pump size, change of absorber pump and emergency drain tank size.
- NOx, 200 mg/Nm3 down to 85 mg/Nm3 (dry@6%O2) Addition of SCR (selective catalytic reduction) system, using ammonium chloride as the reagent, with NH4Cl storage, preparation and direct injection (via Delta Wing), plus plate type TRAC (TRiple Action Catalyst). The SCR has 2 plus 2 layer arrangement. NOx level at SCR outlet is 85 mg/Nm3. The triple actions of the MHPS TRAC catalyst are: high de NOx performance; high mercury oxidation (see below); and low SO2 to SO3 conversion.
- Particulates, 10 mg/Nm3 down to 5 mg/ Nm3 (dry@6%O2) Additional field added to ESP to reduce FGD inlet concentration. Flue gas desulphurisation system provides final reduction to 5 mg/Nm3.
- HCl, HF and NH3 (new requirement), 3 mg/Nm3 for HCl and NH3, 2 mg/Nm3 for NH3 (dry@6%O2) Achieved as a co-benefit of good SO2 removal.
- Mercury (also a new requirement), 4μg/Nm3 (dry@6%O2) SCR with TRAC and ammonium chloride injection in combination with ORP (Oxidation Reduction Potential) control technology to avoid reduction of already captured ionic Hg to elemental Hg and therefore to limit re-emission within the flue gas desulphurisation system; upgrade of FGD waste water system to accommodate increased mercury discharge from FGD; injection of activated carbon upstream of ESP as back-up; injection of additives such as TMT15 as further back-up.
The basic principle of the mercury removal concept is that halogen injection (via NH4Cl) oxidises Hg across the SCR, with subsequent removal in the wet FGD system. As well as avoiding re-emission of Hg in the flue gas desulphurisation system, the ORP control system also improves gypsum quality, prevents formation of Se6+ (which is difficult to remove via conventional waste water treatment technologies) and prevents MnOx scale.
The ammonium injection system, Hg removal concept and ORP control technology to be deployed at Turow were successfully demonstrated at the Miller 1 plant in the USA in 2011.
The TRAC catalyst maintains a high level of mercury (Hg(0)) oxidation (which is good for Hg capture), even with lignite fuel, which is characterised by high water levels, high flue gas temperatures and low Cl levels, all of which are negative factors for mercury oxidation.
Overall, says Bernd Vollmer, head of process engineering and design AQCS, MHPSE, the new BREF requirements are “challenging but manageable”.
Looking to the possibility of backfitting the plant with carbon capture scrubbing technology in the future, this would require an input flue gas with SO2 and NOx levels lowered to around 30 mg/Nm3, and a particulates level of 5 mg/Nm3 (which is about what Turow is expected to achieve).
Future milestone dates for the Turow 11 project include the following: setting of first boiler column, Q2, 2017; boiler pressure test, by the end of 2018; first ignition test with oil, mid-2019; first firing of the boiler with coal and first steam to turbine, Q3 2019; first synchronisation, autumn 2019; and start of trial run, spring 2020.