title: Optimization of torrefaction conditions of coffee industry residues using desirability function approach.
abstract: The aim of the present study is to analyze the influence of independent process variables such as temperature, residence time, and heating rate on the torrefaction process of coffee chaff (CC) and spent coffee grounds (SCGs). Response surface methodology and a three-factor and three-level Box-Behnken design were used in order to evaluate the effects of the process variables on the weight loss (WL) and the Higher Heating Value (HHV) of the torrefied materials. Results showed that the effects of the three factors on both responses were sequenced as follows: temperature>residence time>heating rate. Data obtained from the experiments were analyzed by analysis of variance (ANOVA) and fitted to second-order polynomial models by using multiple regression analysis. Predictive models were determined, able to obtain satisfactory fittings of the experimental data, with coefficient of determination (R2) values higher than 0.95. An optimization study using Derringer's desired function methodology was also carried out and the optimal torrefaction conditions were found: temperature 271.7°C, residence time 20min, heating rate 5°C/min for CC and 256.0°C, 20min, 25°C/min for SCGs. The experimental values closely agree with the corresponding predicted values.
authors.affiliation: CRB - Biomass Research Centre, Via G. Duranti, 63, 06125 Perugia, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Buratti
authors.affiliation: CRB - Biomass Research Centre, Via G. Duranti, 63, 06125 Perugia, Italy. Electronic address: barbanera@crbnet.it.
authors.forename: M
authors.initials: M
authors.lastname: Barbanera
authors.affiliation: CRB - Biomass Research Centre, Via G. Duranti, 63, 06125 Perugia, Italy.
authors.forename: E
authors.initials: E
authors.lastname: Lascaro
authors.affiliation: CRB - Biomass Research Centre, Via G. Duranti, 63, 06125 Perugia, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Cotana
mesh_terms: D003069:Coffee; D006361:Heating; D007220:Industrial Waste; D015233:Models, Statistical; D012044:Regression Analysis; D013696:Temperature; D018505:Waste Management
chemical_list: D003069:Coffee; D007220:Industrial Waste
keywords: Coffee residue; Desirability function; Optimization; Response surface methodology; Torrefaction