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Corporate objective: ecological efficiency

Energy factor

Gases can be a matter of life and death – when scuba diving or in the intensive care unit, for example. Many industrial processes and medical procedures, such as inertisation, cryo-recycling or magnetic resonance imaging, would be completely impossible without gases. In others they help save energy and reduce CO2 emissions or replace toxic chemicals. In sum, gases are indispensable, also for environmental protection. And yet it takes energy to recover those very gases. At Messer we do everything in our power to ensure that this energy is used as efficiently as possible. That’s the most important activity – but certainly not the only one – by means of which Messer exercises ecological responsibility.

The lion’s share of gases used for industrial purposes originates literally out of thin air: nitrogen, oxygen and argon are recovered by air separation units. The air is pressurised with large compressors, cooled to temperatures between minus 170 and minus 196 degrees Celsius and partially liquefied. Through continuous evaporation and condensation in tower-like separation columns, the components of the air are separated from one another. The process demands a lot of electrical energy: it takes about 600 kilowatt-hours to produce one tonne of nitrogen or oxygen. A typical Air Separation Unit (ASU) consumes as much power as all of the households in a town of 40,000 residents.

Efficiency and green electricity

“Those figures alone make it clear just how important the efficiency of an ASU is with regard to its CO2 footprint – to its impact on climate change,” says Dirk Reuter, Global Energy Officer (GEO) of the Messer Group. As a renowned ASU expert, he manages the continuous optimisation of these plants all around the world. “The key question is this: How much gas can we produce per unit of energy used?” And that’s why one task of the process engineers has always been to optimise efficiency. The GEO supports them with the collective experience of the entire company. Their success is apparent in the energy factor, which is the ratio of power consumption to gas yield. In just five years, Messer has managed to reduce that factor by 16 percent for the ASUs in Europe. Along with the efficiency of the individual plants, however, the utilisation of the power grid also plays an important role when determining the environmental impact. With a fluctuating power supply, as occurs in connection with the use of renewable energies, flexible major customers are in demand. In January in El Morell, Spain, Messer commissioned a condenser which is operated primarily under conditions of electrical oversupply – and nonetheless with optimal efficiency.

Energy-efficient recovery of CO2

Carbon dioxide (CO2) is not recovered by air separation, but can be recovered from various other sources, including industrial flue gas. In vertical absorbers, the waste gas flows countercurrent to an amine-containing solvent, which binds to the CO2. The solution is subsequently heated to separate out the carbon dioxide. So energy efficiency plays a major role in this process as well. With improved solvents and an optimised process, the Canadian company HTC has managed to dramatically reduce energy consumption during the heating process. Messer subsidiary ASCO Carbon Dioxide has acquired a 21-year-license from HTC for the exclusive use of this CO2 separation process outside of North America. “This will enable us to consume about 30 per cent less energy than with conventional CO2 flue gas recovery units,” says Dr. Christoph Erdmann, who is responsible for the On-Site division at Messer Group.

Liquid or gaseous

The state of matter of the end product also affects the energy balance. Obtaining atmospheric gases in liquid form requires more than twice the energy needed for a gaseous end product, which suffices for many applications. On the other hand, a tank holds about a thousand times more product in its liquid state than in its gaseous state. “If atmospheric gases are to be transported in a tank by vehicle, then we need them to be in liquid form – otherwise the added cost incurred during just the first few kilometres travelled will already eat up everything saved during production,” explains Dirk Reuter. Provision in the gaseous state is possible via pipeline or by means of gas production on site at the customer’s premises. As a rule, piped-in gas is only available to industrial parks with significant levels of continuous demand. Messer designs, builds and operates large ASUs which are located directly at the customer’s site. They can be found, among other places, in the steel industry, which requires huge quantities of oxygen. Cryogenic generators suffice for producing slightly lower quantities of oxygen or nitrogen. Nitrogen or oxygen can also be recovered by means of non-cryogenic generators without intensive cooling. Such systems use pressure swing adsorption or semi-permeable membranes. Automotive supplier Bosch, for example, recently took delivery of its third cryogenic nitrogen generator with a capacity of 600 cubic metres per hour for its site in Hatvan, Hungary. The two existing generators work with a capacity of 900 and 500 cubic metres per hour, respectively. 

Cylinder innovation

Similarly for the transport of small quantities, energy efficiency can also be raised: if a gas cylinder is filled with 300 bars instead of the usual 200 bars of pressure, it already contains 50 per cent more gas, thereby reducing transport costs significantly. Improved steel quality accommodates these higher pressures while barely increasing the weight of the cylinder. Messer has been a pioneer in this area for about ten years now. Messer took an even greater step forward with the new MegaPack (Gases for Life 3/2013). The completely redesigned cylinder bundle is considerably lighter, contains more gas, and also provides tremendous advantages in terms of handling. Dirk Reuter sums it up this way: “We keep the overall optimum conditions in mind while using continuous efficiency optimisation and technical advancements to reduce energy consumption further and further.”

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