Combined hydrothermal liquefaction and catalytic hydrothermal gasification system and process for conversion of biomass feedstocks
A combined hydrothermal liquefaction (HTL) and catalytic hydrothermal gasification (CHG) system and process are described that convert various biomass-containing sources into separable bio-oils and aqueous effluents that contain residual organics. Bio-oils may be converted to useful bio-based fuels and other chemical feedstocks. Residual organics in HTL aqueous effluents may be gasified and converted into medium-BTU product gases and directly used for process heating or to provide energy.
1. A system for conversion of a biomass, the system comprising:
a hydrothermal liquefaction (HTL) stage apparatus that hydrothermally liquefies the biomass in an aqueous medium at a temperature and pressure selected to form a crude conversion product comprising separable fractions including a bio-oil fraction defined by droplets, an aqueous fraction containing residual organics, and a solids fraction;
a solids separation stage apparatus configured to receive the crude conversion product and separate the solids fraction from the crude conversion product to form a solids-free conversion product comprising the bio-oil fraction and the aqueous fraction containing residual organics;
an enclosed separation stage apparatus configured to receive the solids-free conversion product and separate the bio-oil fraction from the aqueous fraction containing residual organics, the enclosed separation stage apparatus defining an internal geometry configured to coalesce the droplets of the bio-oil fraction, the enclosed separation stage apparatus also defining a discharge path configured for continuous separation of the droplets of the bio-oil fraction from the aqueous fraction containing residual organics; and
a catalytic hydrothermal gasification (CHG) stage apparatus operatively coupled to the enclosed separation stage apparatus and configured to receive the aqueous fraction containing residual organics from the enclosed separation stage apparatus at a selected temperature and pressure that forms a gas product containing at least one medium BTU product gas.
2. The system of claim 1 , further including an upgrade stage apparatus configured to upgrade the bio-oil fraction released from the enclosed stage separation apparatus over a hydrogenation catalyst at a temperature up to about 450° C. and a hydrogen partial pressure up to about 150 atmospheres (1.52×104 kPa) that yields a green crude.
3. The system of claim 2 further comprising at least one heat exchanger operatively coupled to the upgrade stage apparatus.
4. The system of claim 3 further comprising another heat exchanger operatively coupled to the hydrothermal liquefaction (HTL) stage apparatus.
5. The system of claim 4 wherein the heat exchangers are operably engaged to exchange thermal transfer fluid.
6. The system of claim 1 , wherein the gas product when combusted generates sufficient energy such that the sum of the energy demands for conversion of the biomass to the product gas is a net positive.
7. The system of claim 1 , further including one or more heat exchangers positioned to distribute heat to selected locations in the HTL stage apparatus and/or the CHG stage apparatus.
8. The system of claim 1 , further comprising a make up heater operably engaged between the catalytic hydrothermal gasification (CHG) stage apparatus and the enclosed separation stage apparatus.