Full Length ArticlePerformance of a commercial-scale biomass fast pyrolysis plant for bio-oil production
Introduction
Bioenergy, derived from biomass [1], [2], municipal organic solid waste [3], livestock manure [4], and other biological materials [5], [6], [7], has been seen increasingly as a renewable and clean energy source. Among all utilization methods in bioenergy research (such as direct combustion, thermo-chemical conversation and biological conversion technologies) fast pyrolysis—a rapid decomposition of organic materials in the absence of oxygen—has many advantages. It is a relatively simple process, rarely affected by the environmental conditions, has a high energy conversion rate, is CO2/GHG neutral without SOx emissions [8], [9]. A final product, the liquid bio-oil, produced by fast pyrolysis, has numerous advantages of being storable and transportable, as well as having the potential to generate electricity through combustion in a boiler, diesel furnace, engines and gas turbines, and to supply a number of valuable chemicals, such as food flavorings, resins, agri-chemicals, fertilizers, and emissions control agents [10], [11].
To produce bio-oil as a renewable fuel replacement and as a source of chemical commodities, a fast pyrolysis reactor has to be designed and operated to meet the requirements for high yields of liquid fuels. A wide range of reactor configurations have been operated, such as fluid bed reactor, ablative reactor, circulating fluidized bed reactor, entrained flow reactor, rotating cone reactor, transported bed reactor and vacuum moving bed reactor. The capacity of a reactor can vary greatly. For example, a fast pyrolysis fluid bed reactor with the biomass throughput 100 g h−1 was built in Aston University, UK; and Ensyn technologies had constructed a 400 dry T d−1 processing capacity reactor [12], [13]. In our previous research, a 1–5 kg h−1 bench-scale fluidized-bed reactor was constructed, which consisted of three main sections: a feeding section, a reactor section, and a product collection section. The total bio-oil, gases, and char yields were 41.5, 43.3, and 15.2%, respectively [14]. However, detail operation status and product characteristics of large scale biomass fast pyrolysis plant are urgently needed in order to promote the commercialization of biomass pyrolysis technology. Meier et al. [12] indicated that the size of the commercial-scale plant was from 5 T d−1 to 120 T d−1. Additionally, Butler et al. [13] mentioned that the size of the commercial-scale plant was from 7.2 T d−1 to 400 T d−1. To our knowledge, little research has been conducted on the detailed structure, operational principles and stability of the commercial-scale pyrolysis plants and on characteristics of bio-oil and char produced by the commercial-scale pyrolysis plant in spite of success in designing pilot-scale pyrolysis plant.
Thus, in the current work, a commercial-scale biomass fast pyrolysis plant, based on downdraft circulating fluidized bed technology with biomass throughput of 1–3 T h−1, was developed and fabricated primarily for bio-oil production.
Section snippets
Objectives
The objective of this study was to investigate performance of a commercial-scale biomass fast pyrolysis plant. In addition, the physicochemical properties of bio-oil, char and non-condensable gas samples obtained from fast pyrolysis of rice husks were obtained using multiple analytical tests to characterize the physical properties and chemical composition of the samples. This work could provide a valid reference and technical support for biomass fast pyrolysis and bio-oil potential utilization
Feedstock preparation
Rice husks, with characteristics of particle size of approximately 80 mesh (<0.177 mm), moisture content around 10%, bulk density about 340 kg m−3, were collected from Shanxi and Wuhan Provinces.
Pyrolysis system
The schematic diagram of the feeding system and the fast pyrolysis plant is shown in Fig. 1. This fast pyrolysis system with a feedstock throughput of 1–3 T h−1 was developed by Shanxi Yingjiliang Biomass Company and Shanghai Jiao Tong University, PR China and constructed in Dali county, Shanxi Province, PR
Performance of a commercial-scale biomass fast pyrolysis plant
Rice husks were used as raw material to produce bio-oil. In the feeding system, the exhaust gas from a vertical bed was used as drying gas to remove moisture from the rice husks under the temperature of 180 °C to meet the pyrolysis requirement with the exhaust gas flow rate of 18,000 m3 h−1. Because the feeding system is equipped with a feed cyclone, small foreign particles such as soil and dust are separated to avoid contamination of bio-oil. In the heat carrier system, the ceramic balls were
Conclusions
A commercial scale biomass fast pyrolysis plant with biomass throughput of 1–3 T h−1 was developed based on the downdraft circulating fluidized bed reactor concept. The pyrolysis plant consists of six parts: a feeding system, a heat carrier system, a reactor system, a cyclone system, a condensation system and a carbon separating system. The principles and operation of the plant were briefly described. The key features of the plant are: continuous operation; no need to provide external energy to
Acknowledgments
Financial support from the National Natural Science Foundation of China through contract (Grant No. 51176121) and financial support from The National Science and Technology Supporting Plan through contract (Grant No. 2011BAD22B07) are greatly acknowledged. Also, the authors would like to express sincere appreciate to the related analysts from Instrumental Analysis Centre, Shanghai Jiao Tong University for their diligence work. In addition, Professor Norman R. Scott from Cornell University, USA
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