Biomass Hydrogasification Process Thermal Efficiency
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Solution Overview
Problem
The existing methods for thermochemical conversion of biomass into synthetic fuels face inefficiencies due to temperature mismatches between gasification and methanation reactions, leading to thermal inefficiencies and high hydrogen consumption in hydrogasification processes.
Innovation Solution
The method involves fast pyrolysis of biomass in the absence of oxygen, followed by catalytic conversion of pyrolysis gas to hydrocarbons using hydrogen and steam, with internal self-sustaining hydrogen generation through steam reaction, and cyclic catalytic processes for efficient methane production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If oxygen or steam gasification is used to produce syngas, then nitrogen content is minimized, but temperature mismatch between gasification and methanation reactions reduces thermal efficiency
Solution Approach 1:
The patent combines the gasification and methanation reactions into a single hydrogasification step that occurs at a uniform temperature of 700-900°C. This eliminates the temperature mismatch between separate gasification (high temperature) and methanation (low temperature) processes, thereby improving thermal efficiency while maintaining low nitrogen content through the use of hydrogen-rich atmosphere.
Solution Approach 2:
The patent changes the operating temperature parameter from the conventional two-stage process (1300-1500°C for gasification, 300-400°C for methanation) to a single intermediate temperature range of 700-900°C. This parameter change enables both gasification and methanation to occur simultaneously at the same temperature, eliminating thermal inefficiency while producing syngas with minimal nitrogen.
2Object-generated harmful factors
If high temperature gasification (1300-1500°C) is used to eliminate tar constituents, then tar is completely removed, but all product methane must be generated by downstream methanation at much lower temperature, resulting in heat loss
Solution Approach 1:
The patent merges the tar removal and methane production functions into a single hydrogasification step occurring at 700-900°C. This eliminates the need for high-temperature gasification followed by low-temperature methanation, thereby preventing the heat loss that occurs when methane is generated downstream at much lower temperatures.
Solution Approach 2:
The patent changes the gasification temperature from conventional high temperature (1300-1500°C) to an intermediate temperature (700-900°C) that is sufficient for both tar removal and in-situ methane production. This parameter change allows the process to avoid the thermal inefficiency of generating all methane through downstream methanation while still eliminating tar constituents.
3Quantity of substance
If steam gasification is used to produce syngas, then syngas is generated, but the highly endothermic nature of the reaction requires direct or indirect heating by partial oxidation, reducing overall efficiency
Solution Approach 1:
The patent combines the endothermic steam gasification reaction with the exothermic methanation reaction in a single hydrogasification step. The exothermic heat released by methanation provides the necessary heat for the endothermic gasification, eliminating the need for external heating by partial oxidation and improving overall energy efficiency.
Solution Approach 2:
The hydrogasification process is self-sustaining because the exothermic methanation reaction provides the heat required for the endothermic gasification reaction. This self-service mechanism eliminates the need for external energy input through partial oxidation, making the process more efficient while maintaining high syngas production.
4Quantity of substance
If hydrogasification is used to convert biomass into methane, then synthetic fuel is produced, but large amounts of hydrogen are consumed, presenting an economic barrier
Solution Approach 1:
The hydrogasification process generates its own hydrogen in-situ through the steam gasification of biomass. The biomass itself serves as the hydrogen source, eliminating or reducing the need for external hydrogen supply and removing the economic barrier associated with large hydrogen consumption.
Solution Approach 2:
The patent changes the process from conventional hydrogasification that requires external hydrogen supply to a self-sustaining process where hydrogen is generated in-situ through steam gasification of biomass. This parameter change transforms hydrogen from an external input to an internally generated resource, reducing costs.
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 approach enhances thermal efficiency and reduces hydrogen consumption by achieving self-sustaining hydrogen generation and higher methane yields, while minimizing char production and tar constituents.
Implementation Method 1
subjecting the feedstock to fast pyrolysis with rapid pyrolytic heating in the substantial absence of oxygen in order to generate fractions of pyrolysis gas and char
Implementation Method 2
catalytically converting at least a portion of the pyrolysis gas to the product hydrocarbon and carbon dioxide in the presence of hydrogen and steam
Implementation Method 3
catalytically converting at least a portion of the pyrolysis gas to the product hydrocarbon and carbon dioxide in the presence of hydrogen and steam
Implementation Method 4
generating at least a portion of the hydrogen by reaction between steam and a portion of the pyrolysis gas or the hydrocarbon
Implementation Method 5
an endothermic steam reforming step starting from a higher temperature and ending at a lower temperature
Implementation Method 6
an exothermic methanation step starting from about the lower temperature
Data Source
AI summary
The present invention provides a system and method for producing hydrocarbons from biomass. The method is particularly useful for producing substitute natural gas from forestry residues. Certain disclosed embodiments convert a biomass feedstock into a product hydrocarbon by fast pyrolysis. The resulting pyrolysis gas is converted to the product hydrocarbon and carbon dioxide in the presence of hydrogen and steam while simultaneously generating the required hydrogen by reaction with steam under prescribed conditions for self-sufficiency of hydrogen. Methane is a preferred hydrocarbon product. A system also is disclosed for cycling the catalyst between steam reforming, methanation and regeneration zones.