Dear Mr. Shah, your explanation on the issue of gasification temperature was highly enlightening. Thanks. I realise, that as a biologist, I should restrict myself to biogas, an area of research, in which I am getting very encouraging results. Yours A.D.Karve
On Mon, Sep 12, 2011 at 11:26 PM, Shah, Naresh <[email protected]> wrote: > What you are describing are two different processes. > > When you heat biomass in absence of oxygen, you are in a purely pyrolysis > zone and all the gases produced – CO, CO2, H2, H2O, CH4, C2H6, etc. are > results of breaking of bonds in the biomass. As the temperature increases, > there is more energy available to break more bonds and you get more gas. A > closed vessel pyrolysis will produce large amount of char as it is very > difficult to break C-C bonds. > > > > When you blow oxidant (air) in the reactor, it can react with the biomass. > This reaction has two effects: (1) Since oxidation is exothermic reaction, > temperature of the charge increases, and (2) oxidant (air) also chemically > reacts reaction with biomass and it is quite effective in breaking C-C > bonds to produce additional CO and CO2 gases at high enough temperatures > (>700 C) CO2 can also react with biomass to produce additional CO. This is > the main reason for increasing the temperature of gasification. Low > temperature gasification, even with the use of catalysts, cannot overcome > this thermodynamic limitation. > > > > To minimize nitrogen dilution in the product gas stream, the easiest > solution is to feed oxygen instead of air. This solution can be a big > challenge and impractical in small scale gasifiers. To control the process > temperature of a closed vessel and to supply heat from outside, one can use > either externally heated pyrolyzer like coke oven or externally/internally > heated fluidized bed reactors. > > > > Use of catalysts in chemical reactions is only to reduce activation energy > barriers. > > > > -Naresh Shah > > > > > > > > _______________________________________________ > 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/ > > -- *** Dr. A.D. Karve Trustee & Founder President, Appropriate Rural Technology Institute (ARTI) _______________________________________________ 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/
