Ethanol Production Heat Exchangers – The Weak Link in Ethanol Production?

Author / Editor: KARIN ÖHGREN GREDEGÅRD / Dominik Stephan

An innovative twist was added to Inbicon’s second generation ethanol production, helping create a revolutionary new process, which will be licensed worldwide. Many Indian companies may opt to benefit from this new and useful technology.

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“Alfa Laval’s expertise was key in finding the right solution to our cooling needs and their spiral heat exchangers are extremely reliable. Everything runs without any problems since the start.”Carsten Skjodt, Project Manager, Inbicon
“Alfa Laval’s expertise was key in finding the right solution to our cooling needs and their spiral heat exchangers are extremely reliable. Everything runs without any problems since the start.”Carsten Skjodt, Project Manager, Inbicon
(Picture: Inbicon)

Born out of a collaboration between Elsam and DONG Energy, Inbicon has a long history of innovation in sustainability. Their aims are far-reaching: to solve the global energy problem by converting crop residues into genuinely clean and profitable renewable fuels. At their award-winning biomass refinery in Kalundborg, Denmark, they have designed a patented technology for production of clean fuel, ‘the new ethanol.’

This innovative process uses soft biomass residues to produce three revenue-generating products, ethanol, biofuel for use in power plants and molasses-based animal feeds, reducing costs and CO2 emission in the process. With the partnership and expertise of Alfa Laval, Inbicon has created, redesigned and tested a process that has potential to revolutionise ethanol production worldwide.

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Heat Exchangers – The Weak Link in Bio–Refineries?

However, there was a weak link in the process that Alfa Laval was able to fix. Heat exchangers at the heart of the process became clogged by the viscous and fibrous media – which caused expensive unscheduled downtime.

Ethanol Production with Reduction of Carbon Emissions

Inbicon’s challenge was to develop a profit-generating process for clean biofuel production made from soft biomass residues. The problem they faced was – the existing process was inefficient and costly. One major sticking point was the highly fibrous raw materials, which quickly clogged the normal heat transfer equipment.

In the process, straw is first ground and treated with steam to liquefy the hemicelluloses and make the cellulose accessible for enzymes. The hemicellulose sugars are separated from the cellulose fibres and enzymes are added to start pre-hydrolysis. During pre-hydrolysis, the long cellulose fibres are cut into shorter sugar polymers. After prehydrolysis, the slurry is cooled down for subsequent fermentation. After fermentation, ethanol is distilled and lignin that is present in the residue is separated, dried and used as a solid fuel.

Self–Cleaning Spiral Heat Exchangers for Bio–Refinery

Two spiral heat exchangers in parallel are positioned right after pre-hydrolysis, where slurry is cooled down before being fed to fermentation. These spirals are specially designed for the slurry they are handling.

The one-channel design of the spiral heat exchanger makes it self-cleaning, cutting maintenance time and costs, energy consumption and heat loss. They also eliminated unscheduled downtime due to equipment blockages. This is particularly important in a development unit – since process conditions may vary much more than in a commercial plant.

Carsten Skjodt, Project Manager, Inbicon, was particularly happy about the self-cleaning properties of Alfa Laval’s heat exchangers. He said, “The self-cleaning spiral design eliminates blockages. Without that process, it would be very difficult to cool the product efficiently.”

Self–Sufficiency for Steam and Electricity

The biomass refinery at Kalundborg produces enough thermal and electrical energy to supply 100 per cent of its own requirement of steam and electricity.

* The author is Marketing Manager Biofuels & Sugar at Alfa Laval Lund AB.

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