ARS | Publication request: Condensation of acetol and acetic acid vapor with sprayed liquid

Submitted to: Industrial and Engineering Chemistry Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 13, 2012
Publication Date: March 13, 2012
Citation: Dickey, L.C., Boateng, A.A., Goldberg, N.M., Mullen, C.A., Mihalcik, D.J. 2012. Condensation of acetol and acetic acid vapor with sprayed liquid. Industrial and Engineering Chemistry Research. 51:5067-5072.

Interpretive Summary: Importing petroleum is not sustainable and is a major contributor to US balance of payments deficits. Replacing petroleum with a similar liquid made from abundant biomass such as wood chips, switchgrass, or corn stover has been a goal of considerable development effort in ARS and many other research agencies and companies. Heating the biomass rapidly to 500 oC in the absence of air, called fast pyrolysis, converts the biomass to a promising mixture of compounds that could be further processed to produce many of the products now made from petroleum. Quenching the hot pyrolysis vapors quickly is essential to prevent them from continuing to react and be converted to char and gaseous products. The vapors can be rapidly quenched (condensed) by contacting them with aqueous liquid droplets under conditions where the water can evaporate. This work shows that a relatively small condensing vessel equipped with a nozzle that produces fine droplets can easily condense pyrolysis vapor. Therefore this work will further the development of cost effective fast pyrolysis of biomass. Adoption of fast pyrolysis will enable farm residues such as corn stover and cobs to be converted into petroleum substitutes bringing more income to the farm and promoting energy independence for the US.

Technical Abstract: A cellulose-derived fraction of biomass pyrolysis vapor was simulated by evaporating acetol and acetic acid (AA) from flasks on a hot plate. The liquid in the flasks was infused with heated nitrogen. The vapor/nitrogen stream was superheated in a tube oven and condensed by contact with a cloud of fine liquid droplets. The sprayed liquid was recirculated through an ultrasonic nozzle and the rate of condensation and fraction of vapor condensed were determined. Vapors were condensed at various fluid flow rates to estimate rates necessary to obtain nearly complete acetol vapor condensation. The effect of non-condensible gases on the condensation rate was determined by varying the ratio of nitrogen to acetol vapor. By reusing aqueous solution containing condensed AA, its content in the aqueous solution sprayed was increased to 30 wt percent. The higher concentration didn’t reduce condensation rate significantly.