A pilot plant installed at the Duisburg, Germany, site of ThyssenKrupp Steel Europe is converting process gases generated during coke production into marketable materials such as fertilizers and chemical propellants. As an added bonus, it also reduces carbon dioxide emissions. The company believes that the plant is the first of its kind anywhere in the world.
The technology involved is the latest development in a collaborative project by the Schwelgern coke plant (KBS) plant engineering company, Duisburg, ThyssenKrupp Industrial Solutions, and Berlin Technical University (TU Berlin).
“There are coke plants all over the world. With this newly developed process we want to give operators the chance to put their process gases to good use and increase the productivity of their plants,” says Holger Thielert from ThyssenKrupp Industrial Solutions. “For this we have developed and patented a process that converts coke oven gases into valuable materials in an eco-friendly way. We can market this process worldwide and also retrofit it in existing plants,” he adds.
The new process starts with the production of coke, which alongside iron ore is the most important charge material for producing pig iron in a blast furnace.
“For this, coal is ‘baked’ at high temperatures in the coke plant. The hot gases generated by this process contain a number of substances. The pilot plant uses a complex process to scrub the coke oven gas. Adding carbon dioxide produces ammonium bicarbonate,” explains Thielert.
The end products can be put to a range of uses such as nitrogen fertilizers, propellants and foaming agents for plastics or porous ceramics; they can also be used in the food industry.
Following successful tests in the laboratory, two researchers from TU Berlin were tasked with building the pilot plant in Duisburg.
“The key tests can only be carried out under real conditions,” notes Sebastian Riethof, a scientist from the university. As part of ThyssenKrupp Steel Europe’s integrated iron and steel mill in Duisburg, the Schwelgern coke plant offers ideal conditions for the test phase. “If everything goes to plan here at the coke plant, the new process can also be used on an industrial scale.”
Initial results have been promising. The scientists are able to utilize 95% of the ammonia contained in the coke oven gas. Every hour the process produces 15 kg of solid materials from 15m3 of coke oven gas and 2m3 of carbon dioxide. With this level of efficiency, the chemical products can be manufactured at competitive costs, says Riethof.
If the tests continue successfully, this would be a real breakthrough in productivity and resource efficiency. “Here in Duisburg, almost all process gases are already being recycled efficiently,” says KBS managing director Peter Liszio. “If we can now manage on a long-term basis not only to produce marketable products from the coke oven gases for other sectors but also to reduce the carbon dioxide emissions from the mill, it would be real value added with great environmental benefits.” Continued positive progress could see this idea and plant type being used worldwide in the future, he believes.
Schwelgern coke plant produces 2.6 m t/y of fuel for the blast furnaces in Duisburg. It is the most modern of its kind in Europe, boasts the world’s biggest ovens, and currently employs around 300 people.
ThyssenKrupp also is focused on reducing plant emissions in two other ways. First involves start-up of the world’s first automated sinter test facility.
During sintering, fine grains of iron ore are mixed with other materials, heated intensely and baked into lumps by fusing the grain edges. The lump shape of the so-called sinter cake is necessary for producing pig iron in the blast furnace. For daily mass production of sinter, the test facility will make it possible within a few hours to predict exactly the optimum mix of charge materials. This will help not only to maintain quality in the final product, but also give better data on the emissions created by the raw materials themselves.
Linked to this is the second emissions focus — precise dust analysis during the entire test process. This will allow lower-dust raw materials to be identified, helping determine the optimum charge mix for each batch.
In addition, the company is constructing a modern fabric filter that it says will capture almost 99.99% of the dust generated by sinter production. The filter is scheduled to start operation in spring 2017.
Seán Ottewell is Chemical Processing's Editor at Large. You can email him at firstname.lastname@example.org.