“WACKER’s great strength is closed material loops. We use byproducts as starting materials for making other products. This reduces our consumption of energy and other resources.”
There’s tension in the air. “This isn’t the best place to be if you wear a pacemaker,” points out Dr. Klaus Blum as we enter the hall on the Burghausen site. The chemist climbs the steel ladder up to the electrolysis plant. It is hot up here, and a steady hum pervades the hall. “The anodes and cathodes carry currents of between 5,000 and 15,000 amperes,” explains Dr. Blum, who also manages the integrated production system. In the two banks of 168 series-connected cells, the current splits the rock salt brine that is pumped up here into chloride and sodium ions at temperatures of 90°C. In the membrane process, chlorine gas is liberated at the anodes and hydrogen and caustic soda at the cathodes. The depleted brine then returns to the salt-dissolving station.
Electrolysis of salt is one of the starting points in WACKER’s highly complex integrated production system. “Our task is to produce as many products as possible with just a few raw materials, while also keeping waste to a minimum and using energy as efficiently as possible,” says Dr. Blum, outlining the purpose of a strategically operated, highly diverse integrated material and energy system.
Sustainability through Logical Necessity
Right from the start, Dr. Klaus Blum had been impressed by WACKER’s corporate culture based on its founders’ philosophy of sustainability. The Burghausen site had been chosen very deliberately, motivated by the fact that the chemical industry necessarily involves energy-intensive processes. An inexpensive energy source was on hand here in the form of hydropower from the Alz river. Even in the early 1930s, the company’s decision makers had turned their attention to WACKER’s “waste products,” looking for ways to reuse lime byproduct for the production of carbide.
“The integrated production system based on salt, silicon and ethylene is sustainable by logical necessity,” says Dr. Guido Kallinger, explaining the principle. The head of base chemicals at WACKER in Burghausen, together with Dr. Blum, controls the interlinked production chains as part of a four-strong planning team reporting to Site Management. “If we don’t utilize the byproducts of individual chemical processes, such as waste gases, wastewater, solid waste, and, in particular, waste heat, the result is not only environmental pollution but also a loss of value.” Integrated production processes, on the other hand, involve many production chains that, though independent of one another, intermesh like cogs, driving the entire integrated production system like a gear box. “The big advantage is that materials and energy are used efficiently. Byproducts are recycled time and again and either reused within the integrated system or sent for external use,” notes Dr. Guido Kallinger.
One Plant – One Loop
“In the chlorine-HCl system, the toxic chlorinated intermediate products are converted into nontoxic byproducts, such as hyperpure silicon, silicones or pyrogenic silica. Via our integrated system, we can reclaim hydrogen chloride and also recover some of the expended energy as steam for heating purposes,” says Dr. Klaus Blum, explaining the chain of recycling and reuse. Thanks to this closed cycle, which encompasses the different plants located close together at Burghausen, WACKER not only reduces its emissions but also the frequency of potentially hazardous road and rail journeys.
The planners regard the chlorine-HCl cycle as part of a comprehensive integrated system at WACKER’s Burghausen and Nünchritz sites. It also includes the ethylene system, in which ethylene is transformed into organic base chemicals, from which polymer dispersions and dispersible polymer powders are subsequently produced, with applications, for example, in the construction and automotive industries. In the silicon system, over 3,000 silicone products, pyrogenic silica and polysilicon are produced from silicon, methanol and common salt. “If this overarching integrated production system subsequently produces, for example, silicones for wind turbines or solar cells for photovoltaics, the overall result of the process chain actually shows a net energy gain, despite the fact that highly energy-intensive intermediates are used,” calculates Dr. Blum.
Highly Motivated for Challenging Tasks
It is the task of the integrated-system planners always to think in such holistic terms: “We must keep our own production and process conditions in mind just as much as our sales markets and the seasonal fluctuations seen, for example, in the construction industry,” adds Dr. Blum, describing the challenge. The manager holds regular meetings with process staff, and can rely on their unstinting support. “In general, the supervisors, plant and department managers, integrated production system and departmental planners meet once a month to compare their work results, clear up any open questions and work out practicable solutions. They are highly motivated,” says Dr. Blum.
Just a few steps away from the membrane electrolysis facility, Dr. Kallinger operates the HCl synthesis plant. Yellow pipelines carry the electrolytically generated hydrogen and chlorine gases from the cell hall, across the site, directly to the steel-clad reactors. A dazzling flame can be seen through a sight glass. “We generate hydrogen chloride gas in a controlled chlorine-hydrogen reaction at about 2,000°C, and produce concentrated hydrochloric acid,” says Dr. Kallinger, summing up the fierce reaction. The hydrogen chloride and the energy liberated in its synthesis are then used as required to produce further intermediates. “We can minimize material and energy losses because everything takes place in such interlinked processes. This superhighway maximizes the efficiency of our integrated chemical system.”
Like all the units in the integrated system, HCl synthesis is monitored round the clock and operated remotely from the neighboring control center. Here, WACKER employees observe each individual process via twelve monitors. If anything goes critical, they can act immediately and even shut down the respective plant with emergency off switches if necessary. There’s no question that, alongside efficiency, safety takes absolute top priority in the integrated production system. A glossy poster hangs on the wall. “On January 8, 2012, we clocked up 6,500 days without reportable accidents in HCl synthesis - almost 18 years, explains Dr. Blum. “And that’s the way it should stay, since production safety is the major strength of a sustainable, integrated production system.”
Potential for Saving Resources
97% of the hydrogen chloride used in the production loops in Burghausen and Nünchritz is recycled. |
742,000 t of CO2-equivalent emissions were avoided in 2012. Due to the high reutilization rate, less fresh hydrogen chloride needs to be generated and, consequently, there are savings in the transportation of raw materials and energy consumption. |
44% of the heat generated comes from the expansion of the cross-plant, integrated heat utilization system. |
