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 continuous biomass conversion process, comprising the steps of:
hydrothermally liquefying a biomass containing feedstock in an aqueous medium at a temperature and a pressure selected to form a biomass conversion product comprising a bio oil fraction and an aqueous fraction containing residual organics remaining after conversion of the biomass containing feedstock, wherein each fraction is separable from the other fraction;
continuously separating the bio oil fraction from the aqueous fraction containing residual organics by coalescing droplets of the bio oil fraction, wherein the separating the bio oil fraction from the aqueous fraction containing residual organics is performed at a temperature selected between about 300° C. and about 360° C. and a pressure selected between about 100 atmospheres and about 210 atmospheres; and
passing the aqueous fraction containing residual organics to a catalytic hydrothermal gasifier and catalytically hydrothermally gasifying the residual organics in the aqueous fraction over a selected catalyst at a temperature and a pressure selected to form a product gas containing at least one medium-BTU gas.
2. The process of claim 1 , wherein the biomass containing feedstock comprises algae.
3. The process of claim 1 , wherein the biomass containing feedstock comprises an aqueous slurry.
4. The process of claim 1 , wherein prior to continuously separating the bio oil fraction from the aqueous fraction containing the residual organics, further comprising removing solids from the biomass conversion product.
5. The process of claim 1 , wherein both the hydrothermally liquefying and the catalytically hydrothermally gasifying are performed at the same operating pressure.
6. The process of claim 1 , wherein the hydrothermally liquefying and the catalytically hydrothermally gasifying are sequentially performed in separate reactor stages.
7. The process of claim 1 , wherein the hydrothermally liquefying and the catalytically hydrothermally gasifying are both performed at a pressure up to about 210 atmospheres and a temperature up to about 360° C.
8. The process of claim 1 , wherein the hydrothermally liquefying and the catalytically hydrothermally gasifying are both performed at a temperature between about 300° C. and about 360° C. and a pressure between about 100 atmospheres and about 210 atmospheres.
9. The process of claim 1 , wherein the catalytically hydrothermally gasifying generates heat, the process further comprising recycling the heat and using the heat for the hydrothermally liquefying and/or the catalytically hydrothermally gasifying.
10. The process of claim 1 , wherein the catalytically hydrothermally gasifying is performed with a catalyst comprising one or more of Ru, Rh, Os, Ni, and/or Cu.
11. The process of claim 1 , further comprising combusting the product gas to generate energy for one or both of the hydrothermally liquefying and/or the catalytically hydrothermally gasifying.
12. The process of claim 1 , wherein the product gas comprises one or more of methane, hydrocarbons with a carbon number greater than that of methane, and carbon dioxide, wherein the product gas optionally comprises less than 5% hydrogen by weight.
13. The process of claim 1 , wherein the catalytically hydrothermally gasifying forms an aqueous fraction comprising minerals, dissolved ammonia, and/or dissolved carbon dioxide.
14. The process of claim 1 , further comprising upgrading the bio oil obtained from the hydrothermally liquefying to form a green crude.
15. The process of claim 1 , wherein the continuously separating the bio oil fraction from the aqueous fraction containing residual organics is performed without addition of a functional chemical separating agent.
16. The process of claim 1 , wherein the separating the bio oil fraction from the aqueous fraction comprises enlargment of droplets of the bio oil fraction.