2nd Global CemPower Conference and Exhibition 2013
4-5 June 2013, London, UK
Conference review - by Robert McCaffrey, conference convenor
Image gallery for the Global CemPower Conference 2013
See the Global CemPower Conference 2013 video on YouTube
Cempower Conference presentations 2013
The Global CemPower Conference concentrates on waste heat recovery in the cement industry, bringing together cement and lime producers with equipment producers from around the world. Delegates highly valued the varied and effective networking opportunities at the event.
The Global CemPower conference started with Joe Harder of OneStone Consulting who gave an overview of waste heat recovery (WHR) trends. Electricity price trends have risen inexorably, partly due to increasing taxes: the obvious corollary is to save money by generating power using waste heat. The savings depend on the cost of electricity, on the cost of the fuel and on the size of the WHR unit. Joe pointed out that the price of certified emissions reduction certificates under the Clean Development Mechanism has fallen nearly to zero, so that this area of support for WHR projects is now no longer present. WHR units can use waste heat from the preheater kiln and the clinker cooler, although the conference later heard about the possibility of using waste heat from raw and cement mills. Critically, the pyroprocessing system should not have to be modified, although it can be if required. Joe pointed out that there are three basic forms of WHR technology: Steam Rankine Cycle (SRC), Organic Rankine Cycle (ORC) and Kalina Cycle. He suggested that the overall energy conversion efficiency of today's WHR units is around 33-36%, but larger and more efficient plants having less potential than smaller and less efficient plants. Depending on the plant, more energy may be available from the cooler than from the preheater and 30-45kWh/t clinker is commonly achievable. Slight changes in cooler design may give rise to much higher waste gas temperatures, and higher WHR unit efficiencies. With increasing kiln inefficiencies, non-conventional WHR systems such as ORC and Kalina will offer better WHR system efficiencies. Joe pointed out that the number of new WHR systems installed each year in China peaked in 2009, with the number of new units steadily decreasing due to a reducing number of new plants, a fully-retrofitted 'fleet' of older plants and a reduction in CDM credits. The vast majority, more than 99%, of WHR units installed worldwide are Steam Rankine Cycle systems, primarily produced by Sinoma-EC, Nanjing Kesen Kenen (NKK), Conch Kawasaki, Dalian East, Citic HIC, JFE, TESPL and Tecpro. China has 739 WHR units in operation, followed by India with 26, and Japan with 24. WHR units can be supplied at between $2-7m, depending on the size of the unit, the nationality of the supplier, the type of technology (including the old end/condenser technology), the country of installation, the efficiency of the pyroprocessing line and the nature of the raw materials particularly their moisture content. Dr Harder will publish a multi-client study on WHR in the cement industry in summer 2013.
Next, Urs Herzog of Holcim Technology Ltd spoke about Holcim's experience of WHR. He pointed out that electrical energy represents around 25% of the cost of cement manufacture and is often under the control of local monopolies, often state-owned. Holcim commissioned WHR units in 1981 and in 1992, but then only started another unit in 2006 after a hiatus of 14 years. Holcim now operates 271MWe of total installed power capacity, 53MWe outside of China. Most projects are in Asia and are SRC units, while projects outside of Asia are mostly ORC units. In China payback is expected in 3-4 years, but in western countries the payback is expected in 8-12 years, which is on the edge of economic feasibility. Holcim has initiated nine WHR projects over the last five years, in Canada, Switzerland, Slovakia, Romania, Lebanon, India, Thailand, China and Vietnam. Urs pointed out that in reality, a WHR unit will never reach the efficiency of the manufacturer's boast, and would be doing well to achieve an efficiency of 20%. In 2012, Holcim commissioned the world's first ORC-WHR power plant using kiln and cooler gas streams. Another project, a 6.2MWe WHR power plant based on conventional SRC was commissioned in Vietnam in December 2012. A competent maintenance crew is required to gain the full benefit of the WHR units. Urs suggested that Chinese companies have huge experience in WHR, but that it can be difficult to transfer this expertise outside of Asia. Additionally, outside of Asia few suppliers exist with experience in manufacturing heat-exchangers for dusty and abrasive exhaust gas. Overall WHR project duration is approximately three years, two of which will be construction. Project costs for Chinese-built projects may be only 25% of those offered by Western suppliers. Urs suggested that air-condensing coolers are the future, rather than cooling towers and plumes. ATEX regulations may make ORC systems problematic in high-regulation countries. He suggested that the net power output is the critical measure of a WHR unit, as well as the ability to handle heat load fluctuations without tripping. High levels of automation are critical for success of WHR in western/high labour cost countries. To successfully complete a WHR project outside of China, the total project cost must be reduced significantly, through simpler design of layout, civics and equipment, and through standardisation and modularisation. Urs made a plea for a floor-mounted turbine and condenser instead of a classical two story building concept, for simpler gas tie-in concepts and for modularised condenser units. If energy prices flatten or decrease, the viability of WHR projects will decrease. However, he concluded that a WHR system can significantly reduce the electrical energy cost of a cement plant. He suggested that a hybrid Chinese-Western contracting regime may derive the best of both worlds. Understanding the cement industry is a must for any supplier and that heat exchanger design is more important than turbine design.
Ed Zdankiewicz then spoke on behalf of Echogen, which offers a CO2-based WHR power cycle. He pointed out that WHR may be classified as a renewable energy source, since no additional CO2 emissions are produced. Echogen's offering is basically a Rankine Cycle, but based on closed-loop super-critical CO2. No phase change is involved with CO2, so smaller and more compact heat exchangers can be used and there's no inefficient 'pinch point' in the thermodynamic cycle, as there is in steam-and organic-fluid systems. The system can be started in only 20 minutes, and the system is very compact, with no use of water and no corrosion. The CO2 used is non-flammable, non-corrosive and readily available. An 8MWe system can be supplied on two 'skids' or truck-transportable units. Echogen would install heat exchangers equipped with automated dust removal systems into the heat source stream and bring heat into a central heat engine. The Ecogen system has fully-automated PLC-based system control and since the process fluid is super critical, the turbine used can be extremely small, compared to steam-based turbines. Ed suggested that the system can run at an efficiency of 14-30%, depending on air- or water-cooling and the size of the system. Ed stated that all WHR systems are a slave to the ambient temperature of the cooling reservoir, be it air or liquid.
Li Hao of Sinoma Energy Conservation Ltd pointed out that there has been a trend towards using lower and lower temperature waste heat gases in the cement industry. According to Li Hao, customers tell Sinoma that they want to produce their own electricity since they don't have sufficient power supply or have unreliable supply, they have low coal costs and high electricity costs and because they are producing large amounts of waste heat. A high electricity price and a low coal price can give impetus to a WHR project, since the cheaper coal can be used by the cement plant to make its own cheap electricity. In the same way, a lower efficiency cooler may be economic if its exhaust air can be used to make cheap WHR electricity. Mr Hao reminded listeners that if a high chlorine gas flow is to be used, for example from the bypass, the gas flow should be cooled to below 350°C prior to passing over the heat exchangers so that the chlorine condenses from the gas and sticks to the dust, and in this way clogging of the heat exchangers can be reduced. Li Hao made the point that taking waste gases from different parts of the system will provide gas streams with different characteristics, of temperature, dust loading and chemistry, so that different WHR solutions will be required in different parts of the plant. Sinoma can provide a full service package for SRC WHR, including air quenching cooler (AQC) boilers, turbines and generators, steam turbine units, cooling units and bypass boilers. Sinoma can also provide ORC units, which can be installed after a normal Steam Rankine Cycle unit, to extract relict heat energy.
Mr Hao also gave details of a radiation heat exchanger to utilise radiated heat from the kiln, especially when the surface of the kiln is over 300°C. He reminded the audience that losses from the kiln shell can amount to 50kCal/kg clinker. A kiln shell radiation heat exchanger, around the kilns and not attached to it, can produce around 100kWh/day per 3m of kiln shell. Such a system can be dismantled and removed by crane in case kiln maintenance is required. Li Hao suggested that all sources of waste heat in the cement plant will eventually be used.
Volker Quentmeier of Elementis Consult spoke on the use of sewage sludge, pointing out that wet sludge has nearly zero net heat content, but that dried sludge has a calorific value of perhaps one third that of coal. Waste heat can be used to dry sludge, in order for it to be used as an energy source, and it also has an ash content that is useful in the cement raw meal mix. Volker pointed out that regulations are tightening on disposal options, so that the cement industry is likely to see a veritable tidal wave of sludge coming in its direction, with the possibility of charging a gate fee in addition to the benefit of its calorific content. A number of options are available for sludge drying, depending on the temperature of the waste gas stream, using either direct drying or a heat exchanger (where there is a much lower fire and explosion risk). Multi-layer driers can also be used, but these can be technically challenging to operate, so that the single-layer dryer is preferred. Volker also pointed out that solar energy can also be used for sludge drying. Is the use of sewage sludge economic for the cement industry? "Yes and no," concluded Volker, depending on the gate fee, carbon price, coal price, electricity cost, labour cost and other factors.
Luca Xodo of Exergy spoke about his company's Radial Outflow Expander (ROE) turbine for use with the Organic Rankine Cycle. The ROE turbine is different from the axial and radial inflow turbines, giving higher efficiency than competing technologies, with a scalable, simple, low vibration, and reliable configuration. The ROE turbine is well-suited to ORC, with thermal oil preferred as the heat exchange medium, with the oil return temperature easily controlled in order to accommodate upstream process conditions, by varying the degree of superheating.
Andrew Holgate from Econotherm promised to recover the irrecoverable. "It's been a tough year," started Andrew, before suggesting that WHR systems have a great future in front of them. Econotherm's heat pipe technology promises to extract more heat from more heat sources than other forms of heat exchanger and to many different forms of condensing medium. Andrew stated that Econotherm's heat pipes have multiple redundancy, independent pipe operation and that they are almost fail-safe. They operate in isothermal mode, so that there is no thermal stress from one end of the pipe to the other (Figure 14). The pipes are hollow, with a contained heat exchange evaporation/condensation phase. Given a reasonable distance between the pipes, fouling can be kept to a minimal level. Since the tube is at the same temperature along its length due to its high level of thermal conduction, there is minimal corrosion, since the gas temperature is kept above the dew point. The heat pipe unit also induces a low pressure drop in the system. Andrew reminded delegates that lime has abundant waste heat due to the process, but a reliable heat exchanger is required for the lime industry due to the dusty airflow. New manufacturing advances mean that Econotherm's heat pipes are becoming competitive with existing heat exchange technologies.
Darren Bryant of Heatcatcher spoke about his company's role in WHR, which is as a technology integrator, working with GE Energy, the UK Green Investment Bank, equity fund Equitix, and the University of Brighton. As the technology risk of WHR reduces over time, the internal rate of return is expected to fall. The main WHR system installed by Heatcatcher is the GE Energy Clean Cycle 125 ORC unit, with 45 units installed throughout Europe but mostly in Italy and the UK. The first system installed in cement and lime is a 0.5MWe ORC system being installed at Steetley Dolomite at Thristlington in the UK, capturing heat at 214°C. The system has a payback of less than five years, with no grant aid. Darren also stated that lower grade waste heat is progressively being mined by the cement industry. For kiln and also for air quench cooler (AQC) boilers, there are a number of different positions where they can be sited in the process. Darren pointed out a number of integration challenges, including heat exchanger design, stack velocity assessments and the performance of the induced draft fan. The GE Energy WHR units are containerised, with a 134kWe energy production capacity and sophisticated power modification electronics and can be relocated if required. He suggested an average payback period of around five years for kiln exhaust projects, and around four years for clinker cooler projects. With a successful grant application, the payback periods are proportionately shorter. He concluded that the technology offers a good return on investments for most cement plants producing less than 4000t/d. Heatcatcher concentrates on smaller niche waste heat recovery projects, where the total mineable energy is less than around 2MWe.
The last presentation on the first day of the conference was Min Wu of Nanjing Kesen Kenen Environment and Energy Co. (NTK), formerly known as Nanjing Triumph. The company specialises in captive power plants and WHR systems, with 180 projects and 1720MW of power capacity installed. 74% of the company's installations are in the cement industry, with 18% in the steel industry and 8% as captive power plants. As well as its many projects in China, the company has installed projects in India, Turkey, Saudi Arabia and in Madagascar (which is a combined captive power plant and WHR project with 50MW capacity). City Cement in Saudi Arabia is the company's first EPC (engineering, procurement, construction) contract in WHR. The company also operates four BOT power plants, and has references in many applications.
Second day
The first speaker on the second day was François Le Scraigne, on behalf of Cryostar, based in Alsace, France. He spoke about the Organic Rankine Cycle, circulating an organic working fluid around a circuit to convert heat into electricity. The Cryostar technology is based on a radial inflow turbine and it turns out that the technology is economically best-suited to applications above 2MW. François pointed out that there is a trade-off between efficiency and power output, and another trade-off between perfect process efficiency and affordability. Hydrocarbons, refrigerants, Kalina-cycle-esque compound fluids and super-critical fluids can all be used in the company's equipment. Customised solutions are obviously more expensive than standardised solutions, with implications for payback periods, but it is important to find the right balance between standardisation and loss of performance. The company boasts the only Kalina Cycle WHR unit working 'correctly' on a geothermal project.
Project 'Love'
François concluded with a few details of 'Project LOVE' - an EU R&D project to try to use 90-120°C heat from a raw mill and cement mill working at two cement plants in Germany owned by Cemex and Holcim, each with a gross power of 100kW, using a binary cycle sub-critical refrigerant as the working fluid and a Cryostar Eleco 200 as the turbo generator. Further research on the internet shows Project Love to be already two years through its three-year lifespan, with the project expected to conclude in October 2013. The interim conclusions1 of the project team are interesting: 'The different components of the two pilots to be installed at the cement plants have been designed: a finned tube heat and a packed column heat exchanger. Using the heat sources parameters, the optimal operating parameters of each component of the two ORC prototypes have been evaluated. Test benches for laboratory characterisation of the heat exchangers have been realised. The radial inflow turbine that will be shared between the two prototypes has been designed, manufactured and transported to the test facility. An overall economic analysis of the profitability of the plant based on the available cost and technical performance' has been performed. 'The calculations set provided profitability criteria of the ORC investment in the cement plant considered. The case studies showed in most of the cases longer payback time than those generally accepted by industrial for off-production investments. Indeed, the turbine chosen in the LOVE project had to be relatively simple, with high efficiency and with the possibility to be scaled up to 1 MW. However, because of the constraint of use, using the same equipment on two different waste heat sources, no overall optimisation is reachable. The cost of the turbine could be dramatically different, as there are other options for ORC in this scale but with lowered efficiencies. Larger scale deployment might influence the cost significantly...'
Additionally, Project Love's interim report1 states 'Several prototypes of polymeric gas-liquid heat exchanger have been manufactured and tested at laboratory scale during the reporting period. The main efforts in the reporting period are related to the minimisation of the pressure drop on the gas side. This is a key requirement before any further scale up and test in a real plant. Two prototypes have been prepared for tests in future activities. A specifically designed laboratory test bench has been constructed for this purpose.' Delegates were extremely interested to hear many more details on Project Love.
Muayad Matar then spoke about the waste heat recovery installation at Najran Cement in Saudi Arabia. Matar mentioned that Saudi Arabia is the largest oil producer in the world, meaning low electricity prices but that waste heat recovery is still an important technique for reducing CO2 emissions. He introduced the Najran plant, which has three production lines: Two are in operation and one is under construction. The Najran waste heat recovery plant, when completed on all three lines, will produce a total of 27.1MW of electrical power. Matar said that some were unsure whether or not it was a good decision for Najran to proceed with the project, which will generate net power of 25MW using a philosophy of combining all waste heat into one single system for all three lines. Water is in short supply in Saudi Arabia although Najran decided to use a Chinese-supplied Sinoma closed-circuit Steam Rankine Cycle unit, which will be commissioned in September 2013. It is the first WHR project in KSA and cost US$44.9m, and will save the company the cost of 37,500t of heavy fuel oil each year.
Sabrina Santarossa of Turboden, a group company of Mitsubishi Heavy Industries, next spoke about her company's ORC solution. Using an organic fluid allows for dry vapour expansion without liquid drops forming in the turbine, no need to superheat the fluid, and the possibility of gaining energy from lower temperature sources and from lower temperature differentials. Since there is no liquid in the turbine, there is no corrosion in the turbine. ORC systems, stated Sabrina, can also work well at partial loads. Turboden's plants are completely automated and are remotely monitored. Turboden has many references in WHR in biomass plants, as well as in municipal waste incineration. Sabrina gave brief details about a WHR system operating on an electric arc furnace, using saturated steam produced at 245°C and 27bar at 20t/h. She also mentioned the possibility of using molten salts as a heat carrier, which has been used in solar power applications and as a medium-term store of heat in other applications. Ciments du Maroc installed a WHR unit and finding that it had additional capacity, decided to install a concentrated solar power unit to boost its power output. An anonymous 7MW ORC WHR project in the cement industry in North America was also mentioned, using energy from both preheater and cooler. Sabrina concluded by stating that around Euro3000/kW of installed electrical production capacity is a good ballpark figure for the cost of Turboden's WHR solutions.
Robert Primavesi of Allgaier Process Technology next spoke about the use of low temperature waste heat for the drying of organic residues in a new 'rolling bed dryer.' Robert pointed out that the material must interact with the drying gases in a dryer, and that lifters might be used in a rotary drum dryer to achieve proper mixing. The new rolling bed dryer originated in the biomass industry, for particles larger than 8-10mm in diameter. The device, seen in Figure 24, consists of a static inclined drum with an internal paddle for mixing, with the drum perforated to allow ingress of drying air. Retention times of perhaps up to two hours are required when using low grade heat, depending on the material to be dried. Low exhaust gas temperatures of around 40-60°C are achieved and result in very homogeneous drying of the product. A maximum input temperature of around 160°C is recommended, to avoid combustion hazards when drying wood and to reduce VOC (volatile organic compound) emissions if drying plastics. The design of the dryer allows it to clean the materials, reducing their eventual ash content. The 2.5m width and 25m long largest plant provided by Allgaier has a production capacity of around 25t/hr when drying.
Mr Qixian He of Dalian East New Energy Development Company, established in 2005, spoke about his company's capabilities in WHR. Mr He claimed that his company had achieved 165 WHR power plant projects for 192 dry-process production lines in the cement industry, with a total installed WHR electrical production capacity of 1319MW. The company has also worked outside of China, including with Birla Cement in India, and has been chosen by Polysius as its preferred technology partner for WHR. The company offers a proprietary preheater bypass system WHR boiler, which has already been installed on nine plants.
At the end of the conference, a session was held to discuss issues that had been raised at the conference, including the use of drip spray condensers and other cooling options; the availability or otherwise of grants and other funding methods; the next big countries for WHR (conclusion: India, Russia, Turkey, Brazil and Saudi Arabia); trends in global coal and global electricity prices (with the EEX energy exchange in Leipzig said to be at the nexus of European energy price changes); and the possibility of using a 'daisy chain' of increasingly efficient and 'sensitive' WHR units to process and mine increasingly lower and lower grades of heat source in a cement plant. The final conclusion of the group seemed to be that, as ever, in all aspects of waste heat recovery, if the economic sums don't add up, then you can forget it.
Conference awards
At the end of the conference, a number of presentations were given to participants. In the best presentation awards - as voted for by the audience - Sabrina Santarossa was awarded third prize for her paper on Turboden's capabilities in WHR. Second-place went to Ed Zdankiewicz of Echogen Power Systems for his paper on a CO2-based power cycle. However, the prize for best presentation went to Urs Herzog of Holcim Technology Ltd for his honest appraisal of Holcim's track record in, experience of and prospects for waste heat recovery.
Delegates were strongly supportive of the suggestion to meet again in London in two years' time to exchange information on WHR developments, to come up-to-date with news, to meet old and new friends and to conduct networking and business. So, we look forward to welcoming delegates to the 3rd Global CemPower Conference and Exhibition on waste heat recovery, captive power generation and electrical energy efficiency in June 2015. See you there!
References
1 https://documents.epfl.ch/groups/l/lo/love/www/P2%20-%20Executive%20Summary%20for%20web.pdf
Delegates comments on Global CemPower 2013:
- The social evening was very nice and I liked the atmosphere
- The atmosphere and organisation was great
- Nice event with good opportunities for networking
- I enjoyed the speed-dating
- Well-organised and kept to time
- Excellent organisation of the conference, congratulations
- Very interesting new information
- Open forums, opportunities for networking and good presentations
- Great conference, thanks to organisers, go ahead!
- Good atmosphere and networking
- Well organised
Global CemPower Presentations 2013:
Experience and challenges in WHR applications; Urs Herzog, Holcim
Comprehensive WHR solution package for the cement industry; Li Hao, Sinoma Energy Conservation Ltd
Cement plant heat recovery utilising ORC and the Radial Outflow expander; Luca Xodo, Exergy-ORC
Cryostar ORC solutions for cement plant waste heat; François Le Scraigne, Cryostar SAS