Fuelling the industry with a clean gas

Industrial carbon dioxide (CO2) serves a variety of key applications across industries. It is widely used in the food and beverage industries for carbonation of liquid drinks. It can also be used as a shielding gas in welding processes or as a refrigerant with a lower global warming potential than traditional HFCs.

There is an increasing amount of CO2 in the atmosphere, but as of today this is generally not economic to recover, so industrial gas companies need to identify a suitable CO2 emission source to give it a second life by p­urifying it to food or industrial grade for commercial use.

Manufacturers’ Monthly reached out to industrial gas-producing specialist company, Air Liquide, to talk about how CO2 emitted into the atmosphere by chemical and oil and gas industries can be captured and recycled for industrial purposes.

Frank De Pasquale is the business unit manager for CO2 and H2 for the company in Australia. He has been with Air Liquide for 15 years.

“Unlike some of our competitors, we never produce additional CO2 from burning natural gas; we recycle and purify existing CO2 emissions from others. We are proud of this commitment which is part of our Corporate Climate Objectives,” says De Pasquale.

All CO2 emissions are a mixture of CO2 and various impurities, but it is what makes up those impurities that matter when it comes to commercialising the product.

“It could be 99.99 per cent CO2 but has 20 parts per billion of benzene in it, which at parts per billion level is not very much,” said De Pasquale. “However, such a little amount of this kind of impurity means that the CO2 is not suitable for the food industry.”

And how does Air Liquide source its CO2? There are several avenues it utilises. Currently it sources feedstock CO2 from seven different industrial processes, all of which emit CO2 as they make their products – three produce ammonia, one is a power station, one is a steam boiler (both are combustion flue gas sources), while there is one that produces ethylene oxide and another is from a natural gas producer. Each feedstock source has its own set of impurities that has to be dealt with, and then the gas has to be collected so it can be made commercially viable. Take ethylene oxide as example.

“We can get CO2 from a chemical process, such as ethylene oxide production,” said De Pasquale. “When ethylene is reacted with oxygen, it makes ethylene oxide and CO2. The process then requires CO2 to be removed, which we can capture, then purify for the food industry.

“However, ammonia plants are definitely the best feedstock source; CO2 produced this way has the least amount of impurities in it.”

The reason for this, said De Pasquale, is that to make ammonia you need to have a reaction between hydrogen and nitrogen which results in a relatively ‘clean’ stream of CO2 containing less impurities than other emission sources.

“As you go from ammonia to ethylene oxide to natural gas processing to flue gas – you get different levels of purity for CO2 and different impurities that you will need to deal with,” he said.

The cost of production varies greatly because it’s based on the processes used within the different disciplines to ensure food and beverage grade quality. In most processes, there are a few steps.

“Typically, there is some level of compression – there is also, as a general rule, a degree of filtration and drying, followed by liquefaction and distillation, to purify the feedstock to the required quality,” said De Pasquale.

“The process produces CO2 in liquid form, which is approximately -22°C and 20 bar pressure. Not only does producing liquid aid in the purification process, it also allows us to transport it more economically than you would if it was in a gaseous form.”

Once it is trucked to a customer’s site, it is loaded into a bulk cryogenic tank, and the customer uses it in a gaseous or liquid form depending on the application. Vaporisation is made possible using a simple air heat exchange system.

“We use our proprietary remote telemetry systems installed on each cryogenic vessel at customer site to always deliver on-time while optimising our fleet management.”

Because CO2 is sourced from existing industrial and energy production plants’ exhausts, production and distribution of this molecule can be challenging and depends on actual production rates and overhauls of these sources.

“We also produce dry ice in all the states of Australia, using dedicated automated equipment. Liquid CO2 is vaporised and compressed into blocks and pellets of various sizes. Blocks can then be sliced into standard or custom width for use in airline catering for instance,” De Pasquale said.

Dry ice is the solid form of CO2 which we all know from the smoke effects in theatres or in fancy cocktails. CO2 is not liquid at atmospheric pressure and directly changes from solid to gas form (sublimation) at -78.5°C. This property is the primary reason why it is used in cold chain transportation or industrial cleaning: it leaves no residue or liquid to clean or evacuate. And because it is recycled CO2, it is not emitting any additional CO2 in the atmosphere.