Hydrothermal Carbonization: A Pilot-Scale Reactor Design for Bio-waste and Sludge Pre-treatment

Abstract

The purpose of the paper is to illustrate the basis of the design of a pilot-scale reactor built to convert putrescent and high-water content biowaste into a stabilized product by using the Hydrothermal Carbonization process (HTC). The hydrothermal carbonization of selected biowaste has been previously studied in a bench-scale reactor to optimize the process parameters such as the temperature, reaction time, water-to-dry matter ratio and then scaled up at a scale 30 times larger. The new pilot-scale reactor has a volume of 0.1 m3 and has been designed and certified to be operated at 300 °C and 86 bar, allowing a wide range of operating conditions. The design has been structured in two steps: process design (a) and mechanical design (b). The main results of the process design step have been: the installed heat power, the method to provide and control the heating, the minimum reaction time necessary to reach a given yield. The mechanical design focused on the scalability of the reactor, the extraction of reaction products from the reactor at the end of process and increasing of reliability and safety. The designed reactor has been then built, commissioned, and operated in such a way to validate the design criteria and hypotheses. The comparison between the experimental results and the design input dataset confirmed the correctness of the design data input but highlighted that the thermal efficiency of the pilot scale plant was low so indicating the need to enhance it for the demonstrative plant. Graphical Abstract

Hydrothermal Treatment of Biomass Feedstocks for Sustainable Production of Chemicals, Fuels, and Materials: Progress and Perspectives

“…A recent study reported an industrial-scale production of bioethanol (30 000 tons/year) from corncob (processing of 200 000 tons corncob) . Although commercial/industrial-scale production of hydrochar from biomass is not reported yet, several studies have explored hydrochar production in pilot-scale plants . However, for subsequent scale-up and application of the HTC at a commercial-scale, more studies are needed to assess the economic feasibility and degree of environmental impacts due to hydrochar production.…”

“…63,98 Hydrothermal process has been rigorously evaluated for pilot-scale operations. 572,667,668 In recent years, a few companies have implemented commercial/industrial scale hydrothermal processes (specifically bioethanol production using hydrothermally pretreated lignocellulosic biomass). 156 A recent study reported an industrial-scale production of bioethanol (30 000 tons/year) from corncob (processing of 200 000 tons corncob).…”

“…156 Although commercial/industrial-scale production of hydrochar from biomass is not reported yet, 669 several studies have explored hydrochar production in pilot-scale plants. 668 However, for subsequent scale-up and application of the HTC at a commercial-scale, more studies are needed to assess the economic feasibility and degree of environmental impacts due to hydrochar production. Prawisudha et al conducted the hydrothermal conversion of municipal solid waste into solid fuels at a commercial-scale plant (capacity to process up to one-ton solid waste per batch), and found that the properties (e.g., heating value and moisture content) of the solid fuel are close to those of the low-grade sub-bituminous coal.…”

Migration and conversion of phosphorus in hydrothermal carbonization of municipal sludge with hydrochloric acid

“…Hydrothermal carbonization (HTC) is a promising alternative residue management process that can recover nutrients from biological waste with high moisture [9][10]. As a sustainable, economical, and e cient method [11], the HTC process involves heating the biomass in water at subcritical temperatures (180-240°C) and autogenous pressure. To ensure that the pressure consistently exceeds the saturation vapor pressure of water, liquid water is used as the reaction medium.…”

Migration and Conversion of Phosphorus in Hydrothermal Carbonization of Municipal Sludge with Hydrochloric Acid

“…Municipal sludge is the main phosphorus sink during wastewater treatment, ranging from 1000 mg/kg to several weight percent [4], which is the second largest source of phosphorus after phosphate rocks. However, with the growing global population and increasing urbanization, wastewater sludge poses several challenges, including overproduction, treatment requirements, and limitations in agricultural applications [5][6][7]. The Organization for Economic Cooperation and Development predicts that the cost of dealing with the human waste currently produced will be 2% of the global Gross Domestic Product [8].…”