Hydrothermal processing

Technology
Technology details
Name:	Hydrothermal processing
Category:	Primary processing
Feedstock:	Feedstocks with high moisture content. Food waste, Garden and park waste
Product:	Bio-crude, syngas, hydrochar

Hydrothermal processing, also known as Hydrothermal Upgrading (HTU), is a thermochemical conversion process that is used to convert biomass into valuable products or biofuel. The process is usually performed in water at 250-374°C under pressures of 4-22 MPa. The biomass is degraded into small components in water. Based on the target products, which are bio-crude, syngas or hydrochar, the process conditions (e.g., temperature, pressure and residence time) are chosen. One of the most important advantages of hydrothermal processing is that it can use biomass with high moisture content withouth the need for pre-drying. Hydrothermal processing can be divided into three separate processes, depending on the severity of the operating conditions. These include hydrothermal carbonisation (HTC), hydrothermal liquefaction (HTL), and hydrothermal gasification (HTG).

Feedstock

Origin and composition

Feedstock with high moisture content are particularly suitable for hydrothermal processing and include feedstocks such as anaerobic digestion digestate, manures, sewage sludge, DDGS, food waste, municipal wastes, and aquatic biomass such as micro- and macroalgae. Hydrothermal processing routes can typically feed slurries up to 30 wt.% solids.

Process and technologies

Process

A hydrothermal process is usually performed in water at 250-374°C under a pressure of 4-22 MPa. The process can also be carried out under self-generated pressure. The hydrothermal process is divided into two reaction conditions, namely subcritical and supercritical water conditions. These two conditions are determined by the critical point of water (i.e., 374°C and 22.1 MPa). Subcritical water is classified below the critical point at a 100-374°C temperature range and under sufficient pressure to remain liquid. Supercritical water occurs when the temperature is above 374°C and the pressure is above 22.1 MPa. The decomposition steps of biomass during the hydrothermal process can be summerized as follows: at approximately 100°C, the water-soluble portion of the biomsas disperses into water, and hydrolysis takes place above 150°C. Meanwhile, biomass polymers (i.e., cellulose and hemicellulose) disintegrate into heir monomeric chains. At approximately 300°C and 10 MPa, liquefaction occurs and bio-oil is obtained.

Technologies

• HTC occurs at temperatures between 180°C and 250°C and pressure of 2-4 MPa. This is the mildest of the three hydrothermal processing routes. The main product of HTC is solid hydrochar.

• HTL utilises subcritical water and occurs at temperatures between 250°C and 374°C and pressures up to 18 MPa. The main product of HTL is a liquid bio-crude.

• HTG or supercritical water gasification (SCWG) occurs at temperatures above 374°C and higher pressures beyond 20 MPa. The main product of HTG is a syngas.

Product

Dependent on the technology, hydrochar, bio-crude or syngas is produced. The produced gas is not the same as conventional syngas from gasification, which is comprised of hydrogen and carbon monoxide. Nevertheless, the gas is referred to as syngas but is typically high in either hydrogen or methane with carbon dioxide also present. The hydrochar can be utilised as fertilizers, adsorbents, and wastewater treatments. The intermediate biocrude can be further upgraded to liquid hydrocarbon fuels via catalytic hydrotreatment.

Technology providers

Technology comparison

Company name	Country	Technology category	Technology name	TRL	Capacity [kg/h]	Pressure [bar]	Temperature [°C]	Reactor	Gasifying agent	Feedstock: Food waste	Feedstock: Garden & park waste	Product: Char	Product: Oil	Product: Syngas
Company 1	[Country HQ location]	[Technology category (if different sub-categories are defined this has to be specified here, the available categories can be found on each technology page under the chapter Process and technologies)]	[Technology name (the "branded name" or the usual naming from company side)]	[4-9]	[numeric value]					●	●	●	●	●
Company 2	[Country HQ location]	[(if different sub-categories are defined this has to be specified here, the available categories can be found on each technology page under the chapter Process and technologies)]	[Technology name (the "branded name" or the usual naming from company side)]	[4-9]	[numeric value]					●	●	●	●	●

SCF Technologies A/S

Hydrothermal processing provider

General information
Company:	SCF Technologies A/S
Country:	Denmark
Contact:
Webpage:
Technology and process details
Technology name:	CatLiq	Technology category:	Conversion (Thermochemical processes and technologies)
TRL:	6-7	Capacity:	kg·h-1
Gasifying agent:		Pressure:	250 bar
Reactor:		Temperature:	>400 °C
		Other:
Feedstock and product details
Feedstock:	Wet biomass waste	Product:	Bio-oil