Gas manufacturer and supplier Air Products South Africa recently designed and implemented a new way of mixing gases, using thermocompressor technology. As part of ongoing trials, it successfully commissioned a system at ArcelorMittal South Africa’s (AMSA’s) Newcastle plant, in KwaZulu-Natal.
Air Products South Africa process engineering manager Ian Gorin says the Newcastle plant required a higher pressure gas than what was available from the blast furnace gas.
“Instead of the traditional method of using a booster compressor powered by electricity, we designed a gas thermocompressor. This system controls and modulates the gas mix ratio to give exact calorific value, as required by AMSA,” he states.
Further, Gorin explains that to compress the blast furnace gas by 25 kPa (according to the design flow rate) would have required a blower consuming 145 kW of power.
“The major benefit of the gas thermocompressor is that it uses no electrical energy, which, therefore, translates into significant cost savings for the customer.”
He points out that the entire gas thermocompressor station was designed by the Air Products South Africa projects team, at the com- pany’s main facility in Vanderbijl-park, in Gauteng, and that the team also jointly managed the installation with Air Products’ Newcastle operations team.
“The need for the station arose from an energy deficit at AMSA’s Newcastle operations,” Gorin explains.
Moreover, he notes that the plant was importing a high-calorific value methane-rich gas, while the blast furnace was flaring gas.
“The gas is combustible and usable if mixed in the correct proportion with methane-rich gas to create a mixed gas with the correct calorific value.”
The system works on the principle of using the higher pressure from the methane-rich gas as the motive gas to induce a flow of low-pressure blast furnace gas, thereby creating a mixed gas at an intermediate pressure that is higher than the blast furnace gas.
By modulating the various pressures, the thermocompressor produces the mixed gas at a set flow rate, and in the correct ratios of the gases as required by the steel mill.
Additionally, Gorin highlights that the concept would work well where there are integrated mills, such as a blast furnace, which produces low-calorific value gas, as well as a mill using higher calorific value gas.
“The concept of mixing gases using a thermocompressor, and not an electrically-powered booster fan, is exclusive to Air Products’ companies,” states Air Products South Africa on-sites GM Rob Richardson.
“We are also proud of the fact that our first gas thermocompressor station was commissioned on time, on budget and according to customer requirements.”
Moreover, Gorin adds that, while the gas-mixing concept is new to the South African market, it will also be rolled out internationally, and has important implications in terms of energy efficiency and cost savings.