Hi All, The deafening silence on this post is quite interesting. At the very least I would have thought that someone would have suggested adding steam to the reduction zone. What about a charcoal gasifier with steam addition?
Any comments on a 1.6MW/2MW thermal gasifier? Kind regards Rex -----Original Message----- From: Rex Zietsman [mailto:[email protected]] Sent: 16 December 2013 09:57 AM Subject: raising H2 concentration in downdraft gasification Hi All, We are looking at a system that will hydrotreat bio oils from pyrolysis, catalytic cracking and vegetable oil. For this we need in the region of 30kg hydrogen/ton oil. At small scale ie 1 ton oil/hour, this works out at, you guessed it, 30kg of hydrogen/hour. As this is a small amount in the overall scheme of things, we are looking at gasifying wood chips and to recover the hydrogen using pressure swing absorption. What I would like to know is whether we can increase the H2 concentration in syngas by tweaking the gasifier. Clearly we can look at the water gas shift reaction but, as the syngas has to be cooled, washed, pressurised and reheated, it is quite an additional investment for the scale we are looking at. If we could simply up the H2 content, we would go straight from washing to PSA. Residual gas would be piped to a diesel generator where CO and the like will be combusted prior to exhaust to atmosphere. For easy mental arithmetic, let us assume a 33% H2 concentration in dry syngas. 30kg/hour of H2 is 15kmol/hour or 15/0.33 = 45kmol/hour of syngas. A kmol of gas has a volume of 22.4 Nm3. So, to get 30kg/hour requires 22.4 x 45 = 1000 Nm3 syngas/hour (mental arithmetic here, go with the flow). Assuming an 80% PSA recovery this means that we need 1250Nm3/hour of syngas. Not a bad sized downdraft gasifier! Assuming 6MJ/Nm3, this is around a 2MW thermal unit. If we can get the H2 concentration up to say 40%, then the syngas requirement would be 37.5kmol/hour or 37.5/45 x 1250 = roughly 80% of 1250 or roughly 1000 Nm3 syngas/hour. This reduces the size of gasifier to 1.6MW thermal and more sensible in size. --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com _______________________________________________ Gasification mailing list to Send a Message to the list, use the email address [email protected] to UNSUBSCRIBE or Change your List Settings use the web page http://lists.bioenergylists.org/mailman/listinfo/gasification_lists.bioenergylists.org for more Gasifiers, News and Information see our web site: http://gasifiers.bioenergylists.org/
