Biomass Gasifier Tar Oxidation via Fluidized Medium
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Solution Overview
Problem
Current technologies for removing tar from synthesis gas produced by biomass gasification are inadequate in terms of cost, performance, and environmental considerations, as per a study by the National Renewable Energy Laboratory.
Innovation Solution
A biomass gasification system that includes a combustor for heating a fluidized particulate material, a gasifier to produce a tar-containing product gas, and a reactor where an oxygen-containing gas reacts with the product gas to partially oxidize the tar, utilizing a fluidized medium like calcined dolomite or limestone to optimize tar oxidation, resulting in a product gas with a higher H2/CO ratio and reduced tar content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional tar removal technologies (catalytic cracking, dry scrubbing, wet scrubbing) are used, then tar levels are reduced, but the cost, complexity, and environmental impact increase significantly
Solution Approach 1:
The invention changes the temperature parameter by maintaining high temperature (above dew point) throughout the gas cleaning process, preventing tar condensation and enabling simple cooling without tar deposition. This eliminates the need for complex scrubbing systems while effectively managing tar through temperature control alone
Solution Approach 2:
The invention extracts the harmful effect of tar by separating the cooling function from tar removal. By cooling the gas below dew point in a dedicated condenser after tar has been prevented from condensing in the main line through temperature maintenance, tar is removed as a condensed liquid in a simple separator rather than requiring complex scrubbing equipment
2Object-affected harmful factors
If high-temperature gas cleaning is used to remove tar, then tar levels are reduced, but energy consumption increases
Solution Approach 1:
The invention maintains continuous high-temperature flow of product gas through the system, using the thermal energy already present in the gas to prevent tar condensation throughout the entire gas cleaning process. This eliminates the need for additional heating energy while continuously preventing tar formation
Solution Approach 2:
The hot product gas itself serves as the heating medium to prevent tar condensation in downstream equipment. The thermal energy contained in the product gas is utilized self-sufficiently to maintain temperatures above dew point, eliminating the need for external energy input for tar prevention
3Object-affected harmful factors
If product gas is cooled below dew point for tar removal, then tar condenses and is removed, but tar deposits in pipelines and equipment causing blockages
Solution Approach 1:
The invention segments the cooling process into two distinct stages: (1) high-temperature transport phase where gas remains above dew point preventing tar condensation in pipelines, and (2) dedicated condensation phase in a separate condenser where cooling below dew point occurs. This spatial segmentation prevents tar deposits in pipelines while enabling effective tar removal
Solution Approach 2:
The invention introduces a dedicated condenser as an intermediary device between the high-temperature gas line and the tar separation system. This intermediary allows the gas to be cooled below dew point in a controlled environment where tar condensation is desirable, while protecting the main pipeline from tar deposition
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
The system effectively reduces tar levels in the product gas, achieving higher power generation efficiencies and simplified gas cleaning processes, with improved H2/CO ratio and lower emissions, making it suitable for energy conversion devices and chemical synthesis applications.
Implementation Method 1
a reactor where an oxygen-containing gas reacts with the product gas to partially oxidize the tar
Implementation Method 2
a combustor for heating a fluidized particulate material, a gasifier to heat a biomass feedstock with the heated fluidized particulate material
Data Source
AI summary
A method is provided for removing tar from a gas by contacting a first gas containing tar with a second gas containing oxygen for time period sufficient to effect oxidation of at least a portion of the tar in the first gas, thus producing an oxidized product gas that contains less tar than the first gas. The method can also include heating a fluidized particulate material in a combustor, introducing the heated fluidized particulate material from the combustor and a biomass feedstock into a gasifier, such that heat from the heated fluidized particulate material causes the gasification of at least a portion of the biomass feedstock to form a tar-containing product gas, the first gas may contain at least a portion of the tar-containing gas, and the tar-containing gas may be extracted from the gasifier prior to contacting the first gas with the second gas.