Abstract

Crude pyrolysis oils can be produced from different forest and agriculture feedstocks via fast, intermediate or slow pyrolysis processes. Although the oils have promising potential for clean energy production, their corrosivity remains as one of the critical challenges for various industrial applications. A number of studies have been done to investigate the corrosion of metallic materials in crude pyrolysis oils and some general conclusions are made. However, the available information is insufficient for the development of Standards and requirements on the safe oil transportation and storage. To fill some knowledge gaps, this study characterizes the corrosivity of a fast pyrolysis oil produced from hardwood and identifies the corrosion modes and extents of typical iron-based steels (carbon steel, low-alloyed steel and stainless steel), which are cost-effective constructional materials used for the storage and transportation of conventional fossil fuels, under simulated operating conditions of crude bio-oils. Corrosion rate measurements results indicate that carbon steel UNS K02700 experiences active corrosion, low-alloyed steel UNS K91560 suffers less severe corrosion, while stainless steel UNS S31603 shows acceptable resistance. Surface roughness from SEM images matches corrosion observations. Chromium is the dominant element in determining corrosion resistance of steels. A thin layer of Cr oxides shall form on UNS S31603 which prevents the steel from acid attack.

Introduction

Due to the depletion of fossil fuel resources and the environmental problems caused by combusting fossil fuels, renewable energy sources have been extensively explored to reduce the emission of greenhouse gases and environmental pollution. Approximate 15-20% of world total energy is provided by renewable energy including solar, biomass, hydropower, wind, ocean energy, geothermal and etc., in which biomass has gained increasing attraction due to its flexibility, availability and environment friendly nature.1-3 Canada has vast biomass resources especially the waste biomass from forestry and agriculture industries as well as municipal wastes which can be converted to bioenergy via mostly thermochemical or biochemical routes.4 Among the proposed conversion methods, fast pyrolysis is a significant thermochemical conversion technique to produce liquid biofuels. In this process, biomass feedstock is heated at a rate of 10-200 °C/s to a high temperature (in the range of 400-550 °C), and the vapors are rapidly quenched to yield bio-oils (50-85%).5 Commercial operations on the production of bio-oils using fast pyrolysis of forestry and agriculture residues have been realized with a feeding capacity up to 10 ton/h, and the produced liquid oils can be used as fuels, food additives and pharmaceuticals precursors.5,6

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