Efﬁciency and power upgrade by an additional high pressure economizer installation at an aged 620 MWe lignite-ﬁred power plant Vladimir D. Stevanovic a, * , Tadeusz Wala b , Slawomir Muszynski c , Milos Milic d , Milorad Jovanovic d a University of Belgrade, Faculty of Mechanical Engineering, Kraljice Marije 16,11120 Belgrade, Serbia b RAFAKO SA, 33 Lakowa Str., 47400 Raciborz, Poland c Rafako Engineering Solutions, Bulevar Arsenija Carnojevica 86,11070 Novi Beograd, Serbia d Thermal Power Plants “Nikola Tesla”, 11500 Obrenovac, Serbia article info Article history: Received 22 July 2013 Received in revised form 10 December 2013 Accepted 1 January 2014 Available online 27 January 2014 Keywords: Waste heat Flue gas Economizer Boiler abstract An additional high pressure economizer was installed at Unit B1 of the 620 MWe lignite-ﬁred Power Plant “Nikola Tesla B” after 30 years of its operation. An innovative connection of the new additional economizer was applied. It is in parallel connection to the ﬁrst section of the originally built economizer and it is directly fed with the feedwater from the outlet of the feedwater pump. The analysis of Unit B1 operation with such an economizer arrangement is performed and it is supported by measured data. It is shown that more than 30 MWth of the ﬂue gas waste heat is recovered. The Unit gross efﬁciency is increased by 0.53 percentage points, which leads to 9.4 MWe of the electric power production. The parallel connection of the additional economizer also leads to the partial feedwater bypass of the high pressure heaters, which enables an increase of the plant electric power by up to 24.5 MWe. The accompanying effects are the reduction of the pressure drop in the feedwater line and the economizers, which leads to the decrease of the energy consumption for the main feedwater pump operation. The applied solution is presented together with measured and calculated energy and economic beneﬁts. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction Electricity is indispensable for modern societies. For example, many industrial machines and devices, household appliances and information technologies are powered by electricity. Its consump- tion is related to the Human Development Index, which is a com- posite measure of health, education and income or a measure for human well-being [1]. In 2011 the share of electricity in the ﬁnal energy consumption in the world was 17.7%, while this share in the economically developed part of the world represented by the OECD (the Organisation for Economic Co-operation and Development) countries is even higher 22% [2]. Hence, a lot of attention is applied to the efﬁciency of electricity ﬁnal consumption, for instance in resi- dential and industrial sectors [3]. At the same time, a substantial increase of the overall efﬁciency of energy systems can be achieved by measures on the electricity supply side, especially in countries where electricity is produced in thermal power plants by coal combustion. Coal is still the main energy source for electricity pro- duction in the world, according to [2] its share was 41.3% in 2011. Recent commercial developments of the technology of thermal po- wer plants that operate under steam Rankine cycles have risen their efﬁciency, but the majority of thermal power plants are built decades ago and their efﬁciency is still below 40% [4]. Therefore, the increase of efﬁciency of aged thermal power plants leads to the reduction in coal consumption and the increase of overall energy efﬁciency, especially in countries that are dependent on coal consumption. Examples of other important beneﬁts are the reduction of carbon- dioxide emission and increase of electricity generation economy. The utilization of waste heat of ﬂue gases at thermal power plants leads to an important increase of efﬁciency in electricity production. In Ref. [5] it is indicated that a reduction of the exit ﬂue gas temperature from 130  C to 120  C at a pulverized coal-ﬁred thermal power plant increases the net plant efﬁciency by about 0.3 percentage points. Although this is only a fraction of one percent it leads to substantial fuel conservation, especially at the large thermal power plants that operate with the electric power of several hundred megawatts or even in the range of 1 GW throughout the year. The utilization of waste heat and the cooling of * Corresponding author. Tel./fax: þ381 11 3370561. E-mail addresses: vstevanovic@mas.bg.ac.rs, estevavl@eunet.rs (V.D. Stevanovic), tadeusz.wala@rafako.com.pl (T. Wala), slawomir.muszynski@ rafako.com.pl (S. Muszynski), milosmilic@tent.rs (M. Milic), milorad.jovanovic@ tent.rs (M. Jovanovic). Contents lists available at ScienceDirect Energy journal homepage: www.elsevier.com/locate/energy 0360-5442/$ e see front matter Ó 2014 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.energy.2014.01.001 Energy 66 (2014) 907e918