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Siemens to Engineer Selective Waste-Gas Recirculation for Posco Sinter Plants

07/29/2009 - Siemens VAI Metals Technologies will provide Posco with selective waste-gas recirculation systems for two of the five sinter plants at the company's Pohang Works.

Posco, Korea, has placed an order with Siemens VAI Metals Technologies for the provision of engineering and supervisory services for the installation, operation and maintenance of a selective waste-gas recirculation system for each of two sinter plants located at the company's Pohang Works. The contract value is a single-digit million-euro figure.
 
The systems will help the company recycle the sinter plant’s hot offgas containing dust and other pollutants, allowing it to achieve lower specific waste-gas volumes and emission levels, in addition to a lower specific coke consumption.
 
Posco operates five sinter plants at its Pohang Works, two of which will be retrofitted under the new contract with a selective waste-gas recirculation system.
 
One of the new systems will recycle a total of 300,000 Nm3/hour of offgas (representing about 15–20% of the total offgas quantity) to the sinter strand from Sinter Plant No. 3, which has a sintering surface area of slightly more than 500 m2 and is capable of producing six million tonnes of sinter per year.
 
The second new system will be installed for Sinter Plant No. 4, which has a sintering surface area of 436 m2 and produces roughly five million tonnes of sinter per year. The surface area of this strand will be extended to nearly 520 m2 through an elongation of the sinter-strand length to enable an annual sinter output of approximately 6.7 million tonnes. This second system will be used to recycle approximately 300,000 Nm3/hour of offgas (or 15–20% of the total offgas quantity) to the sinter strand.
 
Installation of the selective waste-gas recirculation systems will enable the plant to achieve a higher sinter capacity without increasing the total offgas quantity. To meet municipal environmental regulations, offgas from the sintering process is subsequently treated in an ESP (electrostatic precipitator), DE-SOx plant, DE-NOx plant and bag-filter station.
 
Contrary to other waste-gas recirculation systems where a portion of the total sinter offgas is extracted for recycling to the sinter strand, with the Siemens VAI solution only the offgas from selected wind boxes is recycled to the sinter strand. The system provides a high degree of operational flexibility in that operators can freely select wind boxes for recirculation purposes with, for example, the highest concentrations of CO gas or the highest emission levels. When hot/CO-rich offgas from the sinter strand is selected, the coke consumption required for the ignition of the sinter raw mix can be reduced by up to 10% with a corresponding decrease in CO2 emissions. With the recycling of offgas from wind boxes with especially high concentrations of emissions, an increased quantity of dusts and pollutants can be entrapped or chemically bound or neutralized in the sinter bed. This reduces the overall specific load of pollutants contained in the offgas which must be treated prior to being released to the environment. Additionally, the specific quantity of sinter waste-gas is reduced, which not only lowers electrical energy consumption for the induced draft fans, but which also considerably lowers the CAPEX (capital expenditures) and OPEX (operational expenditures) for the downstream gas-treatment facilities.
 
Start-up of the new waste-gas recirculation systems is scheduled for the first quarter of 2010.
 
With a crude steel output of nearly 35 million tonnes in 2008, Posco (Pohang Iron and Steel Co. Ltd.) is the fourth-largest steel manufacturer in the world. At its production sites in Korea and elsewhere in Asia, the company produces a wide range of carbon, stainless and electrical-steel grades which are sold as coils, sheets, plates and wire rod that are used for a multitude of industrial applications.
 
The Siemens Industry Sector (Erlangen, Germany) is a leading international supplier of production, transportation, building and lighting technologies. The Sector comprises six Divisions: Building Technologies, Drive Technologies, Industry Automation, Industry Solutions, Mobility and Osram. With around 222,000 employees worldwide Siemens Industry posted in fiscal year 2008 a profit of EUR3.86 billion with revenues totaling EUR38 billion
 
With the business activities of Siemens VAI Metal Technologies (Linz, Austria), Siemens Water Technologies (Warrendale, Pa.), and Industrial Technologies (Erlangen, Germany), the Siemens Industry Solutions Division (Erlangen, Germany) is one of the world's leading solution and service providers for industrial and infrastructure facilities. Using its own products, systems and process technologies, Industry Solutions develops and builds plants for end customers, commissions them and provides support during their entire life cycle. With around 31,000 employees worldwide Siemens Industry Solutions achieved an order intake of EUR 8.415 billon in fiscal year 2008.