Wet Torrefaction of Poultry Litter in a Pilot Unit: A Numerical Assessment of the Process Parameters

Rafail Isemin,Oleg Milovanov,Mathieu Brulé,Alexander Mikhalev,Fouzi Tabet,Dmitry Klimov,Frederic Marias,Sergey Kuzmin,Natalia Muratova

doi:10.3390/pr9101835

Abstract

A numerical model for the wet torrefaction of poultry litter in a pilot unit was developed in this study. The model accounted for the following process steps: preheating biomass in a feed hopper, feeding biomass into the reactor, fluidized-bed generation using superheated steam, and the supply of additional heat by the electric heating of the reactor walls. Following a “black box” approach, a major assumption of the model is that the behavior of the fluidized-bed reactor is similar to a completely stirred tank reactor (CSTR). Under this assumption, the properties of the particles and gases do not depend on their location inside the reactor. During wet torrefaction, poultry-litter biomass was heated to a predetermined temperature and decomposed, generating biochar along with a gas phase (torgas), whose amounts depended on the content of inert ash in the biomass particles. Variable optimization in the model was performed using MATLAB software. The model successfully estimated the optimal duration required for the completion of wet torrefaction under various conditions: temperature, batch weight, reactor dimensions, etc. The model was validated using experimental data obtained from a series of wet torrefaction experiments performed in a fluidized bed, and provided reliable estimations of the duration of the process depending on material properties, reactor size and feedstock characteristics.

Highlights

The problems triggered by global warming and the accumulation of waste from human–economic activities have encouraged the search for alternative sources for the production of heat and electricity, sorbents, energy-storage devices and other products with high added value
The model relied on the following assumptions: (1) the properties of the particles and the gas held did not depend on their location inside the reactor, (2) the temperature was homogenous in the entire surface of the reactor walls in contact with biomass, (3) the biomass was converted only into a solid fraction and a gaseous fraction, so that the production of soluble and volatile organic compounds, which were present in the condensate after steam cooling, was neglected, and (4) the amount of superheated steam required from the process could be estimated from the total amount of condensate collected after the experiment
The model accounts for feedstock properties, reactor size, temperature and the amount of

Summary

Introduction

The problems triggered by global warming and the accumulation of waste from human–economic activities have encouraged the search for alternative sources for the production of heat and electricity, sorbents, energy-storage devices and other products with high added value. One such promising source is biomass waste, of which approximately. Common poultry-litter treatments include composting, anaerobic digestion and direct combustion. These all have their drawbacks [3,4], and alternatives solutions are needed [5]. The thermochemical conversion pathway, generating biochar, was used in this work. Biochar can be used for soil improvement [6], as a sorbent for CO2 capture [7], as a sorbent for wastewater treatment from organic pollutants [8] and heavy metals [9]

Methods

Results

Conclusion