In the past, flue gases were usually not utilized, so the energy they carried was lost. The system consists of steam boilers, pipes, water tanks, and pumps and can be directly integrated into the existing flue gas cooling system. Theoretically, the system could entirely replace conventional cooling.
A feasibility study carried out at a steel mill in Turkey revealed potential savings of 44.5 kilowatt hours of electricity per ton of steel produced. That corresponds to around ten percent of the electrical energy that is normally required. If the steam were used to preheat the feed water for the steel mill's power plant, for example, the mill would save 45,000 tons of coal per year.
Electric arc furnaces melt steel scrap under arcs heated to a temperature of about 3,500 °C using high-voltage electricity. Depending on the specific furnace operation, up to one third of the energy used escapes in the flue gases. Normally these flue gases - which can be as hot as 1,800 °C - are extracted from the furnace through water-cooled pipes. Because this cooling water circulates within a closed system, it cannot be permitted to form steam. Cooling towers dissipate the excess heat.
This is where the solution developed by the experts at Siemens Metals Technologies comes in. The hot flue gas is diverted into a steam generator, where it flows around pipes filled with water. The heat from the gas turns the water into steam. A sophisticated system of nested heating surfaces ensures that heat is transferred from the flue gas as efficiently as possible.
Special recirculation pumps ensure that the steam boiler is adequately cooled. The system can handle fluctuations in flue gas temperature and volume, and it is specially designed to deal with the high levels of dust, some of which is corrosive, in the flue gas. Continuous steam production, such as that required for generating electricity, can be achieved through the installation of optional storage buffers known as "steam accumulators."
The heat from the flue gas can be recovered even more efficiently if the gas is directed through an "economizer" after it leaves the steam boiler. In the "economizer" the gas flows around a second system of pipes, where the remainder of its heat is used to preheat the feed water for the steam boiler.
The steam generation system has a modular construction and can be easily adapted to the specific requirements of each plant. This makes it especially easy to modernize existing steel mills.
Dr. Norbert Aschenbrenner | Siemens InnovationNews
Siemens helps transform the main wastewater treatment plant in Vienna into a green power plant
30.11.2015 | Siemens AG
Stanford technology makes metal wires on solar cells nearly invisible to light
26.11.2015 | Stanford University
Chemical weathering of rocks over geological time scales is an important control on the stability of the climate. This weathering is, in turn, highly dependent...
Before the fluid of the middle ear drains and sound waves penetrate for the first time, the inner ear cells of newborn rodents practice for their big debut. Researchers at Johns Hopkins report they have figured out the molecular chain of events that enables the cells to make “sounds” on their own, essentially “practicing” their ability to process sounds in the world around them.
The researchers, who describe their experiments in the Dec. 3 edition of the journal Cell, show how hair cells in the inner ear can be activated in the absence...
Planet Earth experienced a global climate shift in the late 1980s on an unprecedented scale, fuelled by anthropogenic warming and a volcanic eruption, according to new research published this week.
Scientists say that a major step change, or ‘regime shift’, in the Earth’s biophysical systems, from the upper atmosphere to the depths of the ocean and from...
The Fraunhofer Institute for Solar Energy Systems ISE has installed 70 photovoltaic modules on the outer façade of one of its lab buildings. The modules were...
Nerve cells cover their high energy demand with glucose and lactate. Scientists of the University of Zurich now provide new support for this. They show for the first time in the intact mouse brain evidence for an exchange of lactate between different brain cells. With this study they were able to confirm a 20-year old hypothesis.
In comparison to other organs, the human brain has the highest energy requirements. The supply of energy for nerve cells and the particular role of lactic acid...
01.12.2015 | Event News
30.11.2015 | Event News
25.11.2015 | Event News
01.12.2015 | Earth Sciences
01.12.2015 | Life Sciences
01.12.2015 | Earth Sciences