Two-Stage Ebullating Bed Hydroconversion for Biomass
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Solution Overview
Problem
Current methods for converting biomass into biofuels, such as gasification and thermal processes, result in bio-oils with high oxygen content and low thermal stability, requiring further treatment and having poor selectivity, while direct hydroliquefaction processes face challenges in achieving high yield and quality biofuels.
Innovation Solution
A two-stage hydroconversion process using ebullating bed technology under high hydrogen pressure, involving a pretreatment of biomass into finely divided particles and a solvent, with specific temperature and pressure conditions in each stage to optimize hydrogenation and deoxygenation, producing high-quality biofuels with reduced oxygen content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If thermal processes (rapid pyrolysis or hydrothermal conversion) are used for biomass liquefaction, then the process is simple and fast, but the bio-oils produced have high oxygen content, low thermal stability, and poor selectivity requiring further treatment
Solution Approach 1:
The process is divided into two distinct hydroconversion stages: a first stage operating at moderate temperature (300-440°C) for initial deoxygenation and conversion, followed by a second stage at higher temperature (350-470°C) for complete conversion and quality enhancement. This segmentation allows each stage to be optimized for specific functions, achieving both high productivity and high selectivity.
Solution Approach 2:
The patent systematically changes operating parameters between stages: temperature increases from 300-440°C in stage 1 to 350-470°C in stage 2, pressure is maintained at high levels (15-25 MPa) throughout, and hydrogen/feed ratio is controlled (0.1-2 Nm³/kg). These parameter changes enable progression from initial conversion to high-quality fuel production with low oxygen content and high thermal stability.
2Productivity
If single-stage hydroconversion is used, then the process is simpler, but it cannot achieve both high conversion yield and high biofuel quality simultaneously
Solution Approach 1:
The hydroconversion process is segmented into two sequential stages, each with optimized conditions for specific objectives. Stage 1 focuses on maximizing conversion yield through moderate temperature and controlled hydrogenation, while stage 2 focuses on enhancing fuel quality through higher temperature treatment and complete deoxygenation. This segmentation resolves the contradiction by allowing both high yield and high quality to be achieved in sequence.
Solution Approach 2:
The effluent from stage 1 is continuously fed to stage 2 without interruption, maintaining high pressure and hydrogen atmosphere throughout. This continuous action ensures that partially converted intermediates are immediately subjected to further hydroconversion, preventing back-reactions and ensuring complete conversion to high-quality biofuels, thereby maintaining both high yield and quality.
3Productivity
If high temperature and pressure are applied in single stage, then conversion speed is fast, but catalyst deactivation and contamination occur
Solution Approach 1:
The process segments the severe hydroconversion conditions into two stages: stage 1 operates at moderate temperature (300-440°C) with high pressure (15-25 MPa) to protect the catalyst from rapid deactivation, while stage 2 operates at higher temperature (350-470°C) but processes a smaller, pre-treated stream. This segmentation allows fast conversion to occur in stage 2 without immediately deactivating the catalyst, as the bulk of the robust biomass has already been converted in stage 1.
Solution Approach 2:
Stage 1 performs preliminary hydroconversion and deoxygenation of the biomass under milder conditions, preparing the feed for stage 2. This preliminary action removes labile oxygen-containing compounds and protects the catalyst from severe deactivation that would occur if high temperature were applied directly to raw biomass, thereby maintaining catalyst stability while still achieving fast overall conversion.
4Device complexity
If biomass is processed without pretreatment, then the process is simpler, but conversion efficiency and hydrogenation effectiveness are reduced
Solution Approach 1:
The patent applies preliminary pretreatment to the biomass before hydroconversion, including drying to reduce moisture content and grinding to reduce particle size. These preliminary actions improve the physical properties of the biomass, enhancing its reactivity and accessibility to the catalyst in the hydroconversion stages, thereby significantly improving conversion efficiency without adding excessive complexity to the overall process.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This process achieves remarkable conversion to biofuels with low oxygen content, improving yield and quality, and allows for constant operating conditions and catalyst management, avoiding contamination and catalyst deactivation, while enabling co-processing with various feedstocks.
Implementation Method 1
a first stage of hydroconversion in the presence of hydrogen of said suspension in at least one reactor containing an ebullating bed catalyst and operating at a temperature comprised between 300° C. and 440° C., preferably comprised between 325° C. and 375° C., at a total pressure comprised between 15 and 25 MPa
Implementation Method 2
at least one reactor containing an ebullating bed catalyst and operating at a temperature comprised between 300° C. and 440° C.
Implementation Method 3
operating at a temperature comprised between 300° C. and 440° C., preferably comprised between 325° C. and 375° C., at a total pressure comprised between 15 and 25 MPa, preferably comprised between 16 and 20 MPa
Data Source
AI summary
A process for direct hydroliquefaction of biomass selected from algae, lignocellulosic biomass and/or of one or more constituents of lignocellulosic biomass selected from the group comprising cellulose, hemicellulose and/or lignin for producing fuel bases comprising two successive hydroconversion stages under high hydrogen pressure in ebullating bed reactors. Hydroconversion takes place in the presence of a supported catalyst of the type for hydroconversion of petroleum residue and a suspension composed of the biomass and a solvent, preferably a hydrogen donor solvent and preferably recycled from the process. The biomass can undergo a pretreatment of drying and/or roasting and/or grinding and/or demineralization prior to hydroliquefaction.