Energy audit experiences in foundries

Int J Energy Environ Eng (2016) 7:409–423 DOI 10.1007/s40095-014-0152-y ORIGINAL RESEARCH Energy audit experiences in foundries M. Noro • R. M. Lazzarin Received: 3 July 2014 / Accepted: 29 October 2014 / Published online: 18 November 2014  The Author(s) 2014. This article is published with open access at Springerlink.com Abstract Steel industry presents one of the highest energy demand of all the industrial sector. Foundries have a really relevant role both in economical terms and as regards the energy demand. The cost of energy represents several percentage points of the overall costs of a foundry. The electricity demand is very high, particularly for the induction melting furnaces. A large amount of thermal energy is obtained both from natural gas combustion and from the coal needed for the process of formation of cast iron in cupolas. Moreover, the plant services must be considered: one very energy consumer is compressed air production. Every factory is different from another so that the proposal of actions of energy savings or thermal recovers requires a detailed study of each plant considering the lay out and analysing the single processes with related energy needs and thermal levels. The co-operation of the University of Padua with the Centro Produttività Veneto allowed to plan a series of energy audits in some foundries located in Vicenza province. The experiences of the first facilities surveys and audits recommendations demonstrated both potential advantage of energy savings and the related difficulties, often due to the high investment costs. Anyhow the joint work of auditing between the university experts and the foundry technicians produced a better awareness on the critical points of the plant and a higher Published in the Special Issue ‘‘8th AIGE Conference (Italian Association for Energy Management)’’. M. Noro (&)
R. M. Lazzarin Department of Management and Engineering, University of Padua, Stradella S. Nicola, 3, 36100 Vicenza, Italy e-mail: R. M. Lazzarin e-mail: rationality level in the evaluation of investments for the renewable of the machinery. Here, the method of performing the energy audits is described together with the very first results in terms of proposals for energy savings evaluated technically and economically. Keywords Energy audit
Foundry
Thermal insulation
Cupolas
Induction furnace List of symbols E Energy (J, kWh) h Specific enthalpy (kJ kg-1) m Mass flow rate (kg s-1) p Pressure (MPa) P Power (kW) T Temperature (K, C) V Volumetric flow rate (m3 h-1) Subscript 1 2 A, B, C, D, E F, G Loss Steam Steam turbine Cast iron melting temperature Ceiling factory temperature States of the flue gas States of the steam Losses Steam Steam turbine Introduction Energy management and related energy savings in industry sector are well known issues as various legislative acts and standards have been adopted in recent years in Italy (Directive 2006/32/EC on energy end-use efficiency and energy services adopted in Italy by D. Lgs. n. 115/08; Directive 123 410 Int J Energy Environ Eng (2016) 7:409–423 Fig. 1 Final uses of energy in Italy during the last 15 years [1] 2012/27/CE on energy efficiency, not yet adopted in Italy). Energy audit is the main tool that 2012/27/CE Directive foresees to obtain a suitable knowledge of the energy consumption profile of a factory; the final goal is to identify energy saving opportunities and to quantify them also from the economic point of view. A set of national and international standards have been recently released in order to: Table 1 Main data on cast iron foundry in Italy [2] Personnel per factory (n.) 75 – Turnover (G€) 3.2 Net production (Mt) 1.562 Average yearly net production per factory (t year-1) 9,586 – – – regulate how an energy management system has to be implemented (UNI EN ISO 50001, substituting the previous UNI CEI EN 16001); regulate how an energy audit has to be done (UNI CEI TR 11428; UNI CEI EN 16247-1); certificate the energy manager experts (UNI CEI 11339); certificate the energy service companies (UNI CEI 11352). Notwithstanding during the last decade the use of energy in industry has been decreasing while civil uses has been increasing, it still remains one of the most important in Italy (23.6 % of the final uses in 2012) together with civil uses (36.7 %) and transports (30.2 %) (Fig. 1). In 2011, nearly one quarter of the total industry consumption has been consumed by metallurgic sector (23.9 %), followed by non-metallurgic mineral (19.2 %), chemical and petrochemical (13.3 %) and mechanics (12.2 %). During the period 1992–2011, two different phases may be identified: a quite slow increase till 2003 with a peak of 41 Mtoe (?17.9 % with respect to 1992) followed by a fast drop (increased by the financial and economic crisis during the last years) [1]. In this second period, energy consumption of industry sector has decreased by more than a quarter with respect to 2003, with the greatest decreases by non- 123 2008 2011 2012 2012 versus 2011 Foundries (n.) 163 154 152 -2 Personnel (n.) 12,250 11,140 10,895 -245 72 73 ?1 2.4 2.2 -8.0 % 1.161 1.043 -10.2 % 7,541 6,893 -9.0 % metallurgic minerals (-31.5 %) and chemical and petrochemical (-30.2 %). Metallurgic sector instead has substantially maintained quite constant its consumption (about eight Mtoe) [1]. In particular, foundry sector in Italy recorded an impressive decrease in net casting production from the beginning of the financial crisis: from 2.73 Mt in 2007 to 1.96 Mt in 2012, with -33 % for cast iron and -22 % for iron [2]. Concentrating on cast iron production, Italy is the ninth on a global scenario with 1.04 Mt in 2012 (China and India are, respectively, the first and the second cast iron producers in the world with 30.5 and 7.95 Mt in 2011). Table 1 reports the main data about Italian cast iron foundry sector for the last years. Disaggregated data concerning energy consumption and energy bill of foundries in Italy are not easy to find. One reference is the Energy Italian Foundry Association (Assofond Energia) that grouped together 81 foundries in 2013 supplying electrical energy and natural gas. In 2013, Int J Energy Environ Eng (2016) 7:409–423 electrical energy supplied to Italian foundries was 553 GWh with a mean cost of 15 c€ kWh-1 for plant connected to the medium voltage grid (typically 20 kV) (consider that meanly only 6.5 c€ is the energy quota while the great part of the cost of the kWh is due to different charges—transport, distribution and other charges like renewable energies incentives, nuclear plant decommissioning, etc.). Natural gas supplied by Assofond Energia was 13.2 MSm3 in 2013 with a mean cost of 35 c€ Sm-3 (in this case the cost of energy is about 80 %) [3]. Some studies were previously made concerning energy in the foundry sector. Some authors presented trends in activity, primary energy and carbon dioxide emissions of the Mexican iron an (...truncated)