Abstracts - VGB PowerTech Journal 3/2018

Chemistry in Power Plants – Development and Prospects

Walter Hoffmann

Was everything really better in the old days? Hardly, but many things were different. What did chemistry in power plants look like in the past, how did it develop and how will the development continue? I would like to embark on these considerations together with you and start with a review of the early 1980s.[more...]

The research program for the reduction of Hg emissions at RWE Power

Knut Stahl, Peter Moser and Ferdinand Steffen

RWE’s power plants safely comply with both current and future German Hg emission limits from 2019 due to their existing flue gas treatment processes. In recent years, RWE Power has carried out extensive R&D activities in order to be able to further reduce Hg emissions in anticipation of foreseeable statutory requirements. Following a holistic approach, Hg capture by means of activated lignite (HOK®) in an entrained flow process is the focus of our R&D program. The HOK® injected into the flue gas binds both elemental Hg and oxidized Hg and is removed from the flue gas in the electrostatic precipitator together with the fly ash. Since 2014, two process variants (dry injection of HOK® and wet injection of a HOK® suspension) have been tested at the Coal Innovation Center at Niederaussem and from 2016 to 2017 at the Berrenrath power plant. It turned out that both the proven dry injection and the innovative wet injection of very finely milled HOK® are promising technologies to reduce Hg in large lig-nite-fired power plants. In 2017, therefore, construction and commissioning of a full-scale pilot plant was completed. The ongoing test program investigates how the Hg-capture is influenced by variations in the process parameters and the suspension properties. The results will go into the construction of a demonstration plant, commissioning begins end of 2018.

Sulfite control of WFGD systems reduces mercury emissions and improves treatability of waste water

Ray Gansley and Mario Crespi

WFGD installations in Europe and the United States are operating using control of oxidation air to maintain a low sulfite level in the process slurry using GE’s SulfiTrac™ continuous sulfite analyzer. Testing of these installations, including a study by EPRI, has shown significant benefits compared to the traditional forced oxidation processes. In the plants tested, mercury re-emissions are reduced by 80 to 98%, and a resulting total mercury emissions reduced by 1.0 µg/Nm3 with sulfite control compared to full oxidation. Mercury data, categorized by speciation, show that the emissions reduction is due to reduction of the re-emission phenomena that had been occurring across these WFGD’s. Oxidation blower power savings are also achieved with sulfite control. There is no measurable change in gypsum purity or increase in calcium sulfite in the gypsum product.

Effect of precipitating agents Na2S and TMT 15 on Hg re-emission at different operating parameters in wet limestone flue gas desulphurisation

Ida Masoomi, Sahar Mazdeyasna, Barbara Klein and Günter Scheffknecht

Wet flue gas desulphurisation (=FGD) is the state of the art technology in coal fired power plants for removal of sulphur dioxide (SO2) from flue gas. As a co-benefit, oxidised mercury (Hg2+) compounds can be retained in the wet limestone FGD as well. Formerly absorbed Hg2+ compounds, which are present in the absorber suspension, can be chemically reduced to elemental mercury (Hg0) which is subsequently released again into the gas phase, as so-called Hg re-emission. In order to prevent the later, different measures can be taken. One possibility is using sulfidic additives to precipitate the present mercury in the form of hardly soluble mercury sulfide (HgS) compounds. The precipitating agents investigated include sodium sulfide (Na2S) and 2,4,6-trimercaptotiazine, trisodium salt monohydrate (TMT15). The effect of different concentrations of precipitating agents on total mercury (HgT) re-emission from the slurry was studied. The impact of chloride and bromide on HgT re-emission with and without the presence of precipitating agents was also investigated.

Flue gas flow rate calculation for mass emissions reporting Part 1: The pathway from DIN 1942, to EN 12952-15, to EN-ISO 16911-1

Frans Blank, David Graham and Henrik Harnevie

Operators of combustion plant need to know the flue gas flow rate to calculate the mass release of pollutant emissions. For many standard fuels, the calculation of flue gas flow rate gives reliable results, with a defined uncertainty, using relatively simple procedures. The calculated dry flue gas volume is combined with emission concentrations that are reported on a dry basis. When concentrations are also measured on a dry basis, as is often the case for large combustion plants, this avoids the measurement of water vapour and hence an additional uncertainty. This publication is the first (VGB Research Project No. 338) of a series of three VGB Research projects on “Flue gas flow rate calculation for mass emissions reporting”. The other two will appear within a year in this journal, having the following sub-titles:

  • Part 2: Verifying flue gas flow rate calculation, by means of stack testing and data evaluation, to EN-ISO 16911:2013 (VGB Research Project No. 379).
  • Part 3: Plant performance assessment using the Large Combustion Plant and E-PRTR databases (VGB Research Project No. 400).

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Aluminium electrolysis as a power storage

Rebekka Loschen and Roman Düssel

The share of renewable energies (EE) in electricity generation in Germany is expected to reach at least 80 percent by 2050. However, the realisation of this objective will involve structural adjustments. This applies, for example, to the hitherto massively increasing share of fluctuating energy sources, which requires rapid balancing reactions in the power supply system. In addition to network expansion, European networking and the integration of electricity storage facilities, load management can also play an important role in the manufacturing industry, such as of the aluminium production

Implementing state of the art information security provisions to defend against advanced persistent threats

Benjamin Kahler and Andreas Dolp

In January 2018, the Bundesnetzagentur has released a catalogue with regulatory requirements for information security at power plants, referring §11 1b EnWG. Additionally, the Bundesnetzagentur has started a call for contributions to the stated requirements. Operators of critical infrastructures – power plants as well as gas storages – are principally needed to be secured with state of the art information security measures. Looking on recent threats for operators of power plants, the requirements for an increased information security level seem to be necessary. Especially since power production and distribution is key for our society. Our article illustrates how the requirement of operating a DIN EN ISO/IEC 27001 conform ISMS can be achieved and how it can be decided whether a security measure is state of the art. We give a conclusion, valuing the state of the art information security. The abilities of potential attackers are briefly described. It is depicted on which attackers a defence is promising and how to deal with advanced persistent threats.

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Digital twin – Analytic engine for the digital power plant

Uwe Rode

Power leaders globally are constantly seeking opportunities to improve operations, reduce unplanned outages and manage variations in market conditions, fuel costs and weather patterns toward safer environment and greater profitability. However, point solutions have taken operations efficiency only so far. What’s needed is a comprehensive answer, grounded in analytic science, that gives power companies the means to transform operations with actionable insights that drive improved business decisions. The GE Digital Twin is an organized collection of physics-based methods and advanced analytics that is used to model the present state of every asset in a Digital Power Plant. The models start by providing guidance on “design limits” of a power generation unit at the commissioning stage or inferring the design limit for an existing plant/fleet by matching the equipment to thousands of other similar equipment in the database.

The development of global energy supply as a succession of energy-related innovation processes: A qualitative model approach to assess the use of nuclear power

Dieter Herrmann

Often, the development of the world energy supply is adopted as a painful sequence of the exhaustible and polluting use of primary energy sources. Therefore the expectations in practically inexhaustible and environmentally neutral renewable energy sources are high. However, in fact, it depends on the available production, conversion, and utilization technology, which sources of energy are suitable to meet given demands and requirements. In particular, the development of the energy demand requires energy-technology innovations to use new energy sources, to use known energy sources more efficient and to replace exhaustible energy sources at an early stage by others. The historical development of the global energy supply is a se-quence of interrelated energy-technology innovation processes. This makes it also possible, to analyse the historical development of nuclear power and to derive a model on the future role of nuclear power worldwide.

The electrostatic precipitator as electrical load – Energy optimization in the electrostatic precipitator

Josef von Stackelberg

Electrostatic precipitators clean waste gases from dust and aerosols. Therefore they need electrical direct current high voltage. That voltage is produced and supplied into the electrostatic precipitator by special equipment. Depending on the process conditions, the supplied high voltage has certain characteristics, e.g. the height and the retention time, to achieve an as high as possible or required precipitation rate. In the times of heterogeneous energy production systems at the distribution grid, when former basic load power plants have to convert to a regulation mode, because wind and sun energy systems have a higher priority to supply the grids, and the energy consume is too small at the same time, the electrostatic precipitators can take over an additional duty.