Optimizing energy-efficiency for operational excellence

Transcription

1 Optimizing energy-efficiency for operational excellence DUBAL Power & Desalination Plants

2 Self-reliant in power generation With 1,573 reduction cells in seven potlines, producing more than one million metric tonnes of primary aluminium per annum (mtpa), the total load demand for electrical power at Dubai Aluminium ( DUBAL ) is approximately 1,900 MW. This requirement is met through a captive combined cycle power station with an installed power generation capacity of 2,350 MW at 30 C. The power generation capacity of the DUBAL Power Plant has grown substantially since the smelter s commissioning in 1979, with successive increases coinciding with and supporting successive expansions of the smelter itself. The initial installed capacity of 483 MW, which adequately met the load demand of 302 MW at start-up, has grown five-fold in the intervening years. From an initial 13 gas turbines, the DUBAL Power Plant today comprises 23 gas turbine (GT) generators (eight Frame 5; five Frame 9B; one 13DM; six Frame 9E; three 13E2) and seven steam turbine (ST) generators (two back-pressure type; five condensing type). The capacity and load evolution since 1979 is depicted in Figure 1. A total of 44 rectifier transformers (RTs) convert the electrical power from alternating current (AC) to direct current DC, as required by the potlines. The gas turbines have heat recovery steam generators (thirteen single pressure type; ten dual pressure type) to produce steam for seven steam turbines and also the Desalination Plant s evaporator units. Installed capacity, MW ,329 1,656 1,656 1,656 2,127 2,350 2, Load, MW ,096 1,295 1,407 1,623 1,787 1, Figure 1: DUBAL capacity and load evolution (MW capacity equivalent).

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4 Continuous improvement through innovation The current level of power generation at DUBAL has been reached through multiple initiatives and significant investments to save energy and maximize the use of available fuel-gas. The key developments implemented to date, listed in Table 1, are underpinned by a corporate culture of continuous improvement through innovation. Table 1: Key developments to save energy. Initiative GT Evaporator Cooling Frame 9BE Rehabilitation Outage Optimization GT Air Filtration Modification Description Evaporative cooling on GTs 15 to 23 Savings of almost US$8.5 million achieved Fuel savings of 10 mscfd recorded CO 2 emissions reduced by 200,000 tonnes per year Output increased 14.2 per cent Efficiency improved 2.6 per cent Fuel savings of 2 mscfd achieved CO 2 emissions reduced by 40,000 tonnes per year Outages optimization to reduce downtime Maintain high generation availability and efficiency Savings ~ US$5 million 2nd stage filters modification on GTs 15 to 23 GTs 20, 21, 22 are pending, planned for Increase in air filters life plus MW and efficiency improvements Frame 9E Uprates Uprate GT14 from D2 to DM Connecting Potlines 21 and 43 HV Reconfiguration GTX Project Compressed Air Enhancement Output increased 5.5 per cent Improved efficiency 3.9 per cent Achieved fuel savings of 5 mscfd Reduced CO 2 emissions by 93,777 tonnes per year Output increased, 14 per cent Improved efficiency 2.5 per cent Fuel savings of 0.6 mscfd achieved CO 2 emissions reduced by 11,633 tonnes per year Reduction in number of RTs Reduced power losses Reduced aux power consumption Replacement of old equipment Reduced distribution losses < 1 per cent Improve plant security Increased ST 1, 2, 16, 18 and 20 MW output Increase in water production Average fuel saving of 15 mscfd recorded Reduced CO 2 emissions by 300,000 tonnes per year Two compressors in Compressor House 1 capacity upgraded (10,000 m 3 /hr added) Three additional units added in compressor house PL7 (5,000 m 3 /hr added) Augmentation/debottlenecking one standby leg in compressor house (5,000 m 3 /hr) another in PL7 (2,000 m 3 /hr) Frame 9BE up-rated 3 units (3,000 m 3 /hr) Two alumina unloading compressors in PL5 & 6 All resulted in reduced production from Frame 9E costly air production to below 36,000 m 3 /hr in total Achieved fuel savings of 0.03 mscfd CO 2 emissions reduced by 1,000 tonnes per year

5 DUBAL s gas turbines are fuelled primarily by natural gas. Thanks to the cogeneration and combined cycle configuration of the DUBAL Power Plant, approximately 36.8 per cent of the power generated at DUBAL is fuel-free. Through ongoing efforts, the thermal efficiency of the DUBAL Power Plant has improved over the years and in 2011 was per cent. This remarkable improvement has resulted in increased power generation to produce hot metal, while the fuel requirement increment is proportionately less (see Figure 2). The anticipated efficiency for is 44.5 per cent. Moreover, the fitment of built-in dry low NOx burning systems in new GTs and retrofitment of existing GTs reduced DUBAL s NOx air emission rate by 60 per cent between 1990 and 2010 (see Figure 3) MW / mscfd Fuel Power Figure 2: DUBAL power generation growth (generation increase vs. total fuel consumption) g/kwh Figure 3: DUBAL Power Station NOx emission rate.

6 Unique cogeneration installation DUBAL s GTX Project, which entailed the unique construction of a GTX Cogeneration Plant, has raised the power station s installed generation capacity. It has also improved the power station s power generation efficiency: by integrating the new GTX Cogeneration Plant into the existing DUBAL Power Plant infrastructure, better fuel utilisation has been achieved as evidenced by increased efficiency of electricity generation. At the same time, the GTX Cogeneration Plant has decreased the environmental impact of the overall DUBAL Power Plant complex by reducing carbon dioxide (CO 2 ) emissions by approximately 300,000 tonnes per annum (based on pure natural gas operation; even more in the case of partial operation on distillate oil) giving a total reduction in CO 2 emissions of 646,410 tonnes per year. 1. Add-on Mode The steam generated by the GTX Cogeneration Plant s HRSG is distributed to the three combined cycle blocks and to the Desalination Plant, so as to utilize the spare capacity of the latter s steam turbines. 2. Process Steam Mode The steam generated by the GTX Cogeneration Plant s HRSG is exported to the DUBAL Desalination Plant. 3. Replacement Mode The GTX Cogeneration Plant fills-in for any of the existing HRSGs in the three combined cycle blocks during periodic maintenance procedures, thus maintaining power generation capacity. By design, DUBAL s GTX Cogeneration Plant runs in cogeneration with three combined cycle blocks, each comprising two GTs and one ST. It can be operated in one of three modes: GT availability (%) yearly average of FR9E GE fleet is 96% 5 yearly average of FR13E2 Alstom fleet is 97% FR9E FR13E2 Benchmark Figure 4: DUBAL GT Availability

7 Through multiple initiatives and significant investments, DUBAL has achieved fuel savings of 33 mscfd, reduced CO emissions 2 by 646,410 metric tonnes per year, improved the power station efficiency by above 3%, and reduced above US$30 million in operating costs.

8 Harnessing heat energy to produce water Driven by hot gases from the DUBAL Power Plant, the DUBAL Desalination Plant can produce up to 30 million gallons (136,000 m 3 ) of fresh water per day. The water produced is used for the company s on-site needs or sold to a number of external customers. For example, at the peak of the Dubai construction boom (2005 to 2009), DUBAL supplied 18 million gallons a day to construction sites (through a dedicated 17-bay water tanker filling station). The DUBAL Desalination Plant comprises six Multi-Stage Flash (MSF) evaporator units, each consisting of 19 stages and capable of producing 5 million gallons of distilled water per day. Some of the distilled water is retained for industrial uses and the balance is pumped to a blending plant where minerals are added to make it suitable for drinking. The resulting potable water is very high quality, meeting WHO, GCC and Dubai Municipality standards. Innovation is also evident at the DUBAL Desalination Plant. Since 2005, DUBAL has used chlorine dioxide (as an alternative to the traditional disinfection treatment) to improve the quality of potable water and reduce the chance of disinfection by-product (DBP) formation being the first thermal desalination plant in the world to implement the system. The DUBAL Desalination Plant contributes substantially to fuel-cost savings at DUBAL; and is unique in its capacity to supply a significant quantity of very high purity distilled water. Water-saving initiatives Conscious of water being a precious resource, DUBAL has implemented water saving devices across the plant, which have reduced domestic water use by more than 30 per cent. Improvements to DUBAL s dedicated Sewage Plant have improved the quality of treated water for irrigation, thus reducing the requirement for desalinated water for this purpose. A system has been installed at the water tanker filling station to recover spilled water and recycle it, also for irrigation purposes. Corporate focus on energy-saving Despite being self-sufficient in terms of generating its own power requirements, DUBAL strives continually to minimize the power consumption of its operations. Several energy-savings projects have been implemented across the plant over the years. For example, lighting across the complex is continuously audited with the aim of identifying and implementing energysaving options. Energy-saving bulbs have been fitted, resulting in a power consumption reduction of 12,510 kwh per year; and motion sensors have been installed in many areas, especially in unmanned substations. A plant-wide, full scale LED lighting conversion is planned for implementation as soon as practicable. Air-conditioning is a major power consumer at DUBAL, especially during the summer months. To minimize the air-conditioning load, the units thermostats are set at 24 C during working hours and 27 C during non-working hours. As a member of the Dubai Supreme Council of Energy (DSCE), DUBAL has whole-heartedly adopted the directives issued by H H Sheikh Ahmed Bin Saeed Al Maktoum (President of Dubai Civil Aviation, Chairman of Emirates Airline Group, and Chairman of DSCE) to all DSCE member companies regarding the measures which the Dubai Government is taking to minimize energy consumption in Dubai, in fulfilment of the Emirate s 2030 Energy Strategy. DUBAL s efforts in this area saved approximately 17,375,000 kwh over the first 21 months of implementing the directives (April 2011 to December 2012). The overall target is energysavings of approximately 22,000,000 kwh per year by 2013.

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10 About DUBAL DUBAL owns and operates one of the world s largest single-site primary aluminium smelters. Built on a 480-hectare site in Jebel Ali, Dubai, UAE, the complex s major facilities comprise a one million mtpa primary aluminium smelter, a 2,350 megawatt power station (at 30 C), a large carbon plant, casthouse operations, a 30 million gallon per day water desalination plant, laboratories, port and storage facilities. The Jebel Ali site has the capacity to produce more than one million metric tonnes of high quality finished aluminium products a year, in three main forms: foundry alloy for automotive applications; extrusion billet for construction, industrial and transportation purposes; and high purity aluminium for the electronics and aerospace industries. DUBAL serves more than 300 customers in at least 45 countries around the world, predominantly in the Far East, Europe, the ASEAN region, the Middle East and Mediterranean region, and North America. The company holds ISO 9001, ISO/TS 16949, ISO/IEC 27001, ISO/IEC 20000, ISO and OHSAS certification; and has twice won the Dubai Quality Award in the Production and Manufacturing sector (1996 and 2000). Among the many other prestigious awards received over the years, DUBAL has been honoured by the following accolades: Emirates Energy Awards 2007 Private Corporation Energy Award, and Education & Research Award. Emirates Energy Awards 2008 Major Energy Award (1st place), Minor Energy Award (runner-up), and Energy Engineer Award (runner-up). Power Generation and Water Solutions 2009 Transmission & Distribution Project of the Year Award. DUBAL also holds a 50 per cent share in Emirates Aluminium Company Limited ( EMAL ) at Al Taweelah, Abu Dhabi; and has invested in joint venture projects in the bauxite/ alumina sector in Brazil, Cameroon, India and Republic of Guinea. Entirely state-owned, DUBAL is one of the largest non-oil contributors to the economy of Dubai and widely regarded as the industrial flagship of the UAE. Having begun to tap metal at Jebel Ali in November 1979, the company celebrated its 30th anniversary in Glossary AC CO 2 DBP DC DUBAL DSCE GCC GT g/kwh HRSG kwh m 3 /hr alternating current carbon dioxide disinfection by-product direct current Dubai Aluminium Dubai Supreme Council of Energy Gulf Co-operation Council gas turbine grams per kilowatt-hour heat recovery steam generator kilowatt-hour cubic metres per hour mscfd MSF mt/hr mtpa MW MWh NOx PL ppm RT ST WHO million standard cubic feet per day multi-stage flash metric tonnes per hour metric tonnes per annum megawatts megawatt-hour oxides of nitrogen potline parts per million rectifier transformer steam turbine World Health Organisation

11 Technical data Electric power generation Power station installed capacity 2,350 MW at 30 C Equipment 8 Gas turbines with 4 x condensing steam turbines Equipped with Evaporative Coolers Equipped with Dry Low NOx burners (less than 20 ppm) 1 Gas turbine in combined cycle with 1 x steam turbine 13 Gas turbine in large co-generation cycle 1 Gas turbine in co-generation cycle Equipped with Evaporative Coolers Equipped with Dry Low NOx burners (less than 20 ppm) 44 Rectifier transformers converting AC to DC (including boosters x 13) 372 Distribution transformers The Evaporative Coolers enhance the plant electrical output and reduce CO 2 emissions by about 350,000 mtpa. The plant s overall thermal efficiency improved from 33.8 per cent in 1999 to 43.4 per cent in Desalination plant Fresh water production capacity 30 million gallons/day Producing two grades of water: Potable water meeting WHO quality requirement High purity distilled water Equipment 6 multi-stage flash evaporators First evaporator inaugurated on 26 February Back pressure steam turbines 36 MW each Net steam requirement 750 mt/hr Reservoir storage capacity 10 million gallons Water tanker filling station capacity 18 million gallons/day

12 For additional information, contact: Dubai Aluminium ( DUBAL ) P O Box 3627, Dubai, United Arab Emirates Tel: Fax: Updated: February 2013