Two-Step Thermochemical Process for Adding Value to Used Railroad Wood Ties and Reducing Environmental Impacts

Abstract

A two-step thermochemical process combining a thermal desorption at 250–300 °C and a pyrolysis at 500 °C of used creosote-treated wooden railroad ties was carried out to recover preservative and produce a high quality bio-oil and biochar. Under optimal temperature between 280 and 300 °C, high preservative removal efficiency (70–74%) was achieved with a high proportion of polycyclic aromatic hydrocarbons (PAHs, 80–82%) and a large portion of the original wood mass (67–70%) was retained. This thermally treated biomass had higher heating value (HHV; 19.9–20 MJ/kg) than the starting material. The physical properties of the preservative, such as viscosity and density, and its toxic threshold against a common decay basidiomycete fungus were similar to those of commercially available P2-creosote. Pyrolysis of the thermally treated ties produced bio-oils with lower water content and total acid numbers, and a higher amount of lignin-derived compounds than that of untreated ties. Biochars derived from the thermally treated ties contained higher carbon content and lower amount of PAHs than biochars from untreated ties.

Rail road tie preservative recovery and conversion to hydrocarbon fuels: a conceptual process design and economics

“…Over the years, various investigators have explored pyrolysis as an approach to valorize used railroad ties . We We reported recently on a two‐step thermochemical process that includes the extraction and recovery of preservatives followed by conversion of the thermally treated ties through pyrolysis . This approach recovers a high yield of preservatives with a high level of purity and permits the production of high quality bio‐oil with low amounts of water and acidic compounds and high lignin‐derived bio‐oil.…”

“…This approach recovers a high yield of preservatives with a high level of purity and permits the production of high quality bio‐oil with low amounts of water and acidic compounds and high lignin‐derived bio‐oil. The threshold of toxicity for the recovered preservatives is similar to that of a conventional creosote sample . The aim of this study is consequently to evaluate the economic improvement potential of the reported two‐step pyrolysis to upgrade used railroad ties by extracting preservative value and, in so doing, to improve feedstock quality prior to thermochemical conversion by pyrolysis.…”

“…8 Over the years, various investigators have explored pyrolysis as an approach to valorize used railroad ties. 2,9,10 We We reported recently on a two-step thermochemical process that includes the extraction and recovery of pre-size, internal rate of return, and feedstock cost have the most impact on the MFSP. © 2018 Society of Chemical Industry and John Wiley & Sons, Ltd Keywords: railroad ties; creosote; thermal desorption; pyrolysis; techno-economic analysis servatives followed by conversion of the thermally treated ties through pyrolysis.…”

“…© 2018 Society of Chemical Industry and John Wiley & Sons, Ltd Keywords: railroad ties; creosote; thermal desorption; pyrolysis; techno-economic analysis servatives followed by conversion of the thermally treated ties through pyrolysis. 8,10,11 This approach recovers a high yield of preservatives with a high level of purity and permits the production of high quality bio-oil with low amounts of water and acidic compounds and high ligninderived bio-oil. The threshold of toxicity for the recovered preservatives is similar to that of a conventional creosote sample.…”

“…The threshold of toxicity for the recovered preservatives is similar to that of a conventional creosote sample. 10 The aim of this study is consequently to evaluate the economic improvement potential of the reported twostep pyrolysis to upgrade used railroad ties by extracting preservative value and, in so doing, to improve feedstock quality prior to thermochemical conversion by pyrolysis.…”