Pictures of the Future    Fall 2006

Metals for the Megacities

How can millions of tons of steel be produced for booming cities –without severely polluting the soil, water or atmosphere? Siemens offers extensive solutions, from energy-saving cast rolling facilities to software that can learn production control.

Beijing is getting all dressed up. With its eyes on the 2008 Olympic Games, China’s capital plans to move most of its steel industry, complete with smokestacks and blast furnaces, into the hinterlands (Beijing). With millions of visitors expected for the games, it’s important to ensure that guests can breathe clean air. Furthermore, heavy industry no longer fits into Shanghai’s urban concept. City planners are therefore focusing on banks, commerce and high-tech. That’s why China’s largest steel manufacturer, Bao Steel, is moving into a new industrial park in Luojing, some 40 km northwest of the city.

China’s megacities face a dilemma. Every year they use millions of tons of steel to build office towers, shopping centers, power plants, bridges, subways and residential buildings. And every year millions of people stream into the cities from rural areas, often moving into reinforced concrete apartment buildings. Clearly, the country needs to update its infrastructure. But the production of steel, aluminum, copper and cement puts considerable strain on the environment. In fact, China’s urban areas are among the most polluted regions on the planet. It is therefore crucial that this emerging industrial power build production facilities using green technology.

Siemens can help. The company is a leader in processes for sustainable steel production. In addition to producing drives, automation technology and electrical equipment, Siemens—and its Austrian subsidiary Siemens VAI—supplies the mechanical systems, process expertise, technical assistance, training and monitoring services need to build assembly and production facilities for the steel industry. "We are the only producer worldwide that offers everything from one source," says Sanjeev Sinha, Director of the Rolling and Processing division at Industrial Solutions and Services (I&S) in Erlangen. The following are examples of this concept:

Very significant energy savings can be achieved with cast rolling facilities—an area where Siemens is the world market leader. Here, a step between the liquid phase of steel production and the following rolling is eliminated. Normally, liquid raw steel is poured into bars, which are cooled and placed into intermediate storage. These "slabs" are heated again before being rolled out into bands in a roller mill. But in cast rolling facilities, extra-thin poured slabs are rolled out immediately after casting in a hot-rolling mill. These systems must be monitored and controlled in real time by sensors and process computers. The recrystallization of the steel during regulated cooling after rolling is a tricky procedure. "This decisively affects the product’s properties," says Sinha.

Dramatic Reduction in Energy Use. According to the trade journal Millennium Steel, thin slab cast rolling makes it possible to reduce energy consumption by up to 73 % compared to conventional technology. Thus far, some 30 such plants have been built worldwide. Siemens has equipped 22 cast rolling facilities with electrical equipment, especially with powerful process computers. Before it was purchased by Siemens, VAI had also built other plants, including the Baotou Iron & Steel Company plant, which opened in 2001. Thanks to basic improvements in the plant’s operational flow, its production has already been increased by 40 % to 2.8 mill. t a year. By mid-2007, another expansion of the plant’s capacity is planned, and Siemens will once again be supplying the needed drive and automation technology. Increasingly,

China is becoming a proving ground for advanced iron and steel technologies. For instance, Siemens VAI has developed Corex technology—a particularly environmentally friendly process for pig iron manufacture. Due to its economical and environmental advantages, Corex technology is gradually taking the place of traditional blast furnaces. Siemens VAI is now building the largest Corex facility to date, for Bao Steel subsidiary Baoshan in Luojing. The plant, which is designed to produce 1.5 mill. t of pig iron a year, will be "stoked up" in the fourth quarter of 2007.

In contrast to conventional blast furnaces that require special coking coal to smelt iron from ore, a Corex facility can be operated with normal coal, eliminating the need for a coking facility. Similarly, the sinter facility in which the iron ore is traditionally prepared before smelting, is no longer needed. Corex works with lump ore straight from the mine. This innovative technology is a two-step smelting reduction process. First, the iron oxide contained in the ore is reduced to "sponge iron." This interim product is then reduced further in the second step and fused into pig iron. In both cases, coal provides the energy.

Slashing Emissions. Corex technology results in major cost savings. After all, the price of coking coal has doubled to about $120 per ton due to the sharp increases in steel production in the last five years. "Even considering that the price of steam coal has also increased—albeit less sharply than coking coal—we can achieve cost reductions of up to 20 % with the Corex process," says Christian Böhm, project manager at Siemens VAI. Still more impressive is the possible reduction of pollutant emissions. Conventional blast furnaces include a cokery and a sintering facility that produce roughly 1.4 kg of sulfur dioxide per ton of pig iron. According to TÜV Rheinland, Corex cuts these emissions to a mere 40 g, and discharges of dust and nitrogen oxides are cut by more than 90 %.

In addition, compared with conventional blast furnaces, Corex cuts discharges of ammonia, phenols and sulfides in waste water. And the gas created by the Corex process can be sold commercially. At the Luojing facility, it will be used to heat the smelter and power a nearby combined cycle plant. These advantages have impressed China’s steel industry. Bao Steel wants to build a second Corex facility with a capacity of up to 1.5 mill. t of pig iron a year. And residents of Shanghai will be able to breathe easier in the future.
                                                                                                           Günter Heismann