Gasification of poultry litter in a lab-scale bubbling fluidised bed reactor: Impact of process parameters on gasifier performance and special focus on tar evolution

Giannis Katsaros,Daya Shankar Pandey,Alen Horvat,Guadalupe Aranda Almansa,Lydia E Fryda,James J Leahy,Savvas A Tassou

doi:10.1016/j.wasman.2019.09.014

Abstract

Poultry litter (PL) gasification was experimentally investigated using a lab-scale bubbling fluidised bed reactor. Characterisation of the gasification process was performed in terms of yields and compositions of both gas and tar, lower calorific value (LCV) of the product gas, cold gas efficiency (CGE) and carbon conversion efficiency (CCE). Experiments were carried out at different temperatures (700–750 °C) and equivalence ratios (ERs). The effect of gasifier temperature at a constant ER of 0.21 shows that an increase in temperature improved the gasification process performance whilst the total tar content decreased, implying that higher temperature enhances the conversion of biomass to product gas. The total gas yield increased from 0.93 to 1.24 N2-free m3/kgfeedstock-daf, LCV increased from 3.38 MJ/m3 to 4.2 MJ/m3, while the tar content was reduced by 24% (5.6–4.25 gtar/kgfeedstock-daf). The detailed analyses of tar compositions reveal that styrene and xylenes were the most abundant compounds in the secondary tar group. Moreover, naphthalene and 1, 2-methyl naphthalene were the dominant compounds found in tertiary polycyclic aromatic hydrocarbons (PAH) and alkyl tertiary groups, respectively. Furthermore, at the highest tested temperature of 750 °C and ER of 0.25, bed agglomeration took place causing the shutdown of the gasifier. The defluidisation of the bed occurred due to the high ash content of PL comprising of low melting temperature alkali compounds. The results obtained from this study showed the performance and potential challenges associated with gasifying PL in a fluidised bed reactor for the combined heat and power production at farm level.

Highlights

The production of poultry meat is expanding throughout the world, imposing significant challenges related to the efficient management of associated litter generation
The effect of temperature on the gasification behaviour of Poultry litter (PL) was experimentally studied in a lab-scale fluidised bed reactor
The lower calorific value (LCV) of 4.2 MJ/ m3 is low, if the presence of tar in the gas stream is taken into account represented as naphthalene, the value rises to 5.8 MJ/ Nm3, a fact that is useful if the product gas is destined directly for combustion without prior cleaning

Summary

Introduction

The production of poultry meat is expanding throughout the world, imposing significant challenges related to the efficient management of associated litter generation. ⇑ Corresponding authors at: RCUK Centre for Sustainable Energy Use in Food basis approximately 80 million birds, mostly chickens were slaughtered in the UK alone (Rumsey, 2018). A recent study estimated that the amount of PL produced falls between 1.75 and 5.7 kg of litter/bird over a 42 days production cycle (Dalólio et al, 2017). In the UK, the total amount of PL generated annually ranges between 140,000 and 456,000 tonnes, while its LCV on an as received basis ranges between 8.75 GJ/tonne and 14.27 GJ/tonne (Lynch et al, 2013). The estimated potential energy from PL varies between 1.22 PJ and 6.5 PJ. Considering its energy potential, PL can be utilised as a renewable feedstock for bioenergy production

Methods

Results

Conclusion