06/15/2011 | Autor / Editor: Sabine Mühlenkamp / Jörg Kempf
Corrosive and abrasive, hot and aggressive — such are the character traits of the gas liquor to be handled in a pressurised coal gasification plant. The pumps used, though, parry the attack with their intelligent design and high-quality materials.
In the light of limited gas and oil reserves, coal is currently experiencing a renaissance as a raw material. In countries like India, China, and Indonesia, as well as in Malaysia and Australia, coal gasification in particular has been receiving lots of attention of late as a process that yields synthesis gas (syngas) for use in fuelling diverse facilities.
The main advantage of coal gasification is that even (domestic) coal of inferior quality can be converted to syngas, hence helping to reduce dependence on imported oil.
The same trend is taking hold in India, too, where Jindal Steel & Power is building a coal gasification plant to obtain synthesis gas for producing pig iron. Measuring upwards of 2000 hectares, the site has room for an air separation plant, coal pressure gasifiers, a power plant and the steel mill itself plus all the requisite infrastructure. The core components of the process are the coal gasifiers in which coal is converted to synthesis gas by means of partial oxidation with steam and oxygen. The process takes place at high pressure and temperature. Seven fixed-bed pressure gasifiers and the requisite downstream gas conditioning and desulphurisation processes are currently being installed. A total capacity of 225,000 Nm³/h of synthesis gas is being targeted for the downstream DRI (direct reduced iron) process that yields the pig iron.
The process demands peak performance on all the parts of plant and equipment, the dimensions of which are accordingly huge. Each pressure gasifier, for example, is nearly four metres in diameter. Temperatures of 1000 °C inside the reactor and as high as 500 °C on the outside surface are just the face of the challenge. “The real problem for components like the pumping systems is the combination of abrasive, aggressive and corrosive constituents in the gas liquor,” explains Thomas Wallner, a Pegnitz-based KSB project engineer who has been on the project from the very start. The fluids can contain particles of coal measuring up to 6–8 mm across and accounting for as much as ten percent by weight. “This combination,” Wallner explains, “imposes particularly stringent demands on the choice of materials and the design of the system.” Specially designed pumps were needed for...
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