Composition, Utilization and Economic Assessment of Torrefaction Condensates

Abstract

The aim of this study was to determine the yields and chemical compositions of condensates formed at torrefaction conditions with different kinds of feedstocks and to assess their utilization from an economic perspective. Test runs for spruce and bamboo were carried out with a slow pyrolysis test rig, and the liquids collected at 20−105, 105−240, and 240− 300°C temperature ranges were analyzed for chemical characteristics and compositions. The results were compared with those obtained earlier for a birch condensate. The mass yields and compositions of condensates differed between the feedstocks and the temperature ranges. The amount of organic compounds in the total condensates was 12−19 wt %. The main compounds were acetic acid, 1-hydroxy-2-propanone, methanol, furfural, and 2-hydroxyacetaldehyde. Total condensates formed at ≤280°C are promising to be utilized for different purposes, for example as a biopesticide. Higher temperatures are critical, because at 290°C , strong exothermic reactions occur, which decreases considerably the yield of torrefied material and produces tar containing condensates. It is possible to produce, in addition to biocoal, valuable liquids. Economic assessments were performed for three torrefaction cases without and with the recovery of condensates. The production costs of torrefied pellets can be lowered significantly, for example on the order of 5−10 € MWh −1 in medium scale pellet production, by recovering and selling the condensates to new applications.

Investigation into mean residence time and filling factor in flighted rotary torrefier

“…[2] Torrefaction is a slow heating process that is usually carried out in an inert environment and at atmospheric pressure within a narrow temperature range of 200-300 8C. [3][4][5][6] Torrefaction can increase energy density and reduce the moisture content and the hygroscopic nature of the raw biomass. This process also improves the grindability and flowability of biomass, making it more suitable to use in co-firing power plants.…”

Torrefaction of almond shells: Effects of torrefaction conditions on properties of solid and condensate products

“…Consequently, the percentage of energy derived from condensates became much higher at this point. This was one of the few studies that directly measured GCVs of condensates, which were required for an accurate economic assessment of torrefaction (Fagernas et al, 2015).…”

“…Table 3, which presents the elemental composition of the samples. This increase in C content was due to the loss of moisture and other volatile components that contained O and H during torrefaction, such as acetic acid, methanol, aldehydes, and ketones (Fagernas et al, 2015;Le Thanh et al, 2015). This is also shown in the Van Krevelen plot (Fig.…”

“…The volatiles were usually cooled to form condensates and their compositions were characterized by high performance liquid chromatography (HPLC) (Prins et al, 2006), Fourier Transform Infrared (FTIR) spectroscopy (Bridgeman et al, 2008;Nocquet et al, 2014), gas chromatography (Medic et al, 2012b;Fagernas et al, 2015), or gas chromatography-mass spectrometry (Kim et al, 2012;Ren et al, 2012;Fagernas et al, 2015;Le Thanh et al, 2015). One study calculated heating values of volatiles from their elemental compositions and from mass balances during torrefaction (Peduzzi et al, 2014).…”

Torrefaction of Agricultural Residues: Effect of Temperature and Residence Time on the Process Products Properties

“…The composition of the condensables from wheat straw torrefaction has been extensively studied in the past [23,24], but only a few studies on condensables utilization can be found in the available literature. These studies mainly concern condensables from woody biomass torrefaction and their applications as biodegradable pesticides [25], wood protection agents [26], or anaerobic digestion substrates [27]. The method of condensables utilization differs for different feedstocks as well as for different process parameters.…”