Treatment of Hydrothermal-Liquefaction Wastewater with Crossflow UF for Oil and Particle Removal.

Ali Sayegh,Florencia Saravia,Simon Merkert,Harald Horn,Joscha Zimmermann

doi:10.3390/membranes12030255

Abstract

This study aims to evaluate the application of ceramic ultrafiltration membranes in the crossflow mode for the separation of particles and oil in water emulsions (free oil droplets and micelles) from hydrothermal-liquefaction wastewater (HTL-WW) from the hydrothermal liquefaction of municipal sewage sludge. The experiments were carried out using one-channel TiO2 membranes with pore sizes of 30, 10 and 5 nm. The results showed that the highest stable permeability could be achieved with a membrane-pore size of 10 nm, which experienced less fouling, especially through pore blockage, in comparison to the two other pore sizes. Instead of observing an increase in the permeability, the application of a higher feed temperature as well as backwash cycles led to a clear increase in irreversible fouling due to the presence of surfactants in the HTL-WW. Among several physical and chemical cleaning methods, alkaline cleaning at pH 12 proved to be the most efficient in removing fouling and maintaining stable performance on a long-term basis. Ceramic-membrane ultrafiltration can be considered as an adequate first-stage treatment of real HTL wastewater.

Highlights

Fossil resources are the traditional sources for the production of fuels, but their availability is limited
This study aims to evaluate the application of ceramic ultrafiltration membranes in the crossflow mode for the separation of particles and oil in water emulsions from hydrothermal-liquefaction wastewater (HTL-WW) from the hydrothermal liquefaction of municipal sewage sludge
The aim of this study is to investigate the performance of ceramic ultrafiltration membranes, in crossflow mode, for the pretreatment of real Hydrothermal liquefaction (HTL)-WW

Summary

Introduction

Fossil resources are the traditional sources for the production of fuels, but their availability is limited. To find an alternative for fossil fuels, interest in biofuel production is rising. Hydrothermal liquefaction (HTL) of biomass is one of the emerging technologies which valorizes different wet biological feedstocks for the production of biocrude as a blended stock of liquid transportation fuel [1]. Typical HTL process parameters range between temperatures of 250–450 ◦C and pressures of 100–300 bar. Water remains either in its liquid state or a relatively dense supercritical state under these pressure and temperature conditions. The advantage of HTL over other liquefaction processes is that the energy-intensive drying step is excluded [2]

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Conclusion