In the last two decades the community has long discussed the possibility to apply an Organic Rankine Cycle (ORC) in Cement Market. Despite physics tell all of us that organic fluids properties are definitely winning against water in presence of low temperature sources (like those typically available downstream clinker coolers and pre-heating towers), for years the cement sector has been driven by steam turbines. In the past this trend was partially justified by a general lack of commercial competitiveness of ORC in terms of CAPEX. The rest probably by a lack of significant references of ORC in handling streams of gas from clinker coolers and pre-heaters. The renewed attention of cement producers in plant efficiency, mainly due to the recent changes in electricity market, has put in great evidence the need of higher performances of WHR in term of power generation and reduced OPEX. In this new contest, last year CTP Team signed in Turkey the first contract for a WHR project based on ORC in a 10.000 TPD line, with the potential to generate 7 MW of electricity recovering the wasted gas from clinker cooler. The power unit provides approximately 12% of the total plant electricity consumption, saving something like 36 million of KWh per year. The ORC technology has been preferred to steam for higher power generation, lower OPEX of the system (roughly a quarter of OPEX prospected by the operation of an equivalent system with steam/water) and the total absence of water required by the cycle. In short, better ROI, valuable reduction of operative costs, no environmental impact, increased capacity to compete in a flat market.
How it works?
Organic ranking cycle adopts a high molecular mass organic fluid with lower boiling point, higher vapor pressure, higher molecular mass and higher mass flow compared to water. Together, these features enable higher turbine efficiencies than those offered by a conventional steam system. The system proposed by CTP works with two heat transfer stages. The first stage transfers heat from the waste gases from kiln pre-heater hot gasses and clinker cooler quench air to thermal oil. The second stage transfers heat from thermal oil to the organic fluid. There are many operational advantages in using thermal oil as intermediate loop: Thermal oil is always in liquid phase, very stable at high temperature and with lubricant intrinsic characteristics. It presents no issues of corrosion; erosion and it is extremely durable (only a minor replenishment of less than 1 % of the initial charge is yearly required).
The heat from the thermal oil is used to pre-heat and vaporized the organic fluid. The fluid is then expanded though the turbine, which is connected to an electric generator. The exhaust vapour flows through the regenerator, where it heats the organic liquid and is then condensed in the air-cooled condenser, releasing the condensing heat to ambient air. The organic working fluid is then pumped into the regenerator and evaporator, thus completing the closedcycle operation.
The WHR system with ORC technology is completely waterfree: This is very important where water consumption is an issue, the ORC solution is designed to best fit with such characteristics.
Maintenance activities and costs are minimized compared to steam turbine thanks to several characteristics of the ORC technology, like organic fluid dry expansion in the turbine (no erosion of blades) and non-aggressive and non-corrosive properties of organic fluid and thermal oil.
The equipment are supplied with an high level of automation and designed to follow the plant main process automatically, without any impact in the production of clinker.
CTP designs WHR with the aim to reduce OPEX. The system requires minimum level of supervision both in normal operating conditions and during shutdown procedure. Where steam-based heat recovery plants normally need teams of dedicated operators to follow daily boilers chemistry and turbine operation, ORCs are remotely monitored and controlled and require minimal yearly maintenance activities, allowing the cement plant technicians to focus on cement production process.
The system can work down to 10% of the designed thermal load and the electrical efficiency remains high down to 50% of the thermal load. In case of multiple kilns or variable heat source load, ORC can maximize the energy produced per year. Finally our customers can always count on a system availability higher than 98%.
CTP Team highlights:
CTP Team is an Italian company with 50 years of experience, leader in engineering and manufacturing of products for cement in the fields of environmental systems and heat recovery. With innovative products for Filtration, Gas Cleaning, Heat Exchangers and Waste Heat Recovery, CTP can design and install customized installations to fulfil Client’s constraints and expectations.
