Fischer-Tropsch Off-Gas Conversion for Hydrocarbon Production
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Solution Overview
Problem
The existing processes for preparing paraffin products from carbonaceous feedstocks face inefficiencies due to the buildup of CO2 and CH4 in Fischer-Tropsch reactors, leading to reduced hydrocarbon production and imbalanced H2/CO ratios, especially when recirculating off-gas, which can result in unstable catalyst performance and reduced catalyst lifespan.
Innovation Solution
A process involving partial oxidation of carbonaceous feedstocks, followed by a Fischer-Tropsch reaction, and subsequent conversion of off-gas using catalysts comprising iron, copper, zinc, and nickel, with controlled steam/off-gas ratios to stabilize catalyst performance and optimize hydrocarbon production, including steps for hydrogenation and reforming to manage CO levels and enhance H2/CO ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If all off-gas is recirculated to the Fischer-Tropsch reactor, then the utilization of off-gas is maximized, but CO2, CH4 and inerts build up reducing hydrocarbon production
Solution Approach 1:
The patent extracts CO and H2 from the off-gas through steam reforming and water-gas shift reactions, separating the useful components (CO and H2) from the harmful components (CO2, CH4, and inerts). This allows the useful gases to be recycled while preventing the buildup of harmful substances in the Fischer-Tropsch reactor.
Solution Approach 2:
The patent introduces steam reforming and water-gas shift reactions as intermediary processes between the Fischer-Tropsch reactor and off-gas recirculation. These intermediary reactions convert the off-gas composition into a more suitable form for recycling, transforming CO2 and H2O into additional CO and H2 while removing harmful components.
2Productivity
If off-gas is fed back to gasifiers, then off-gas utilization is improved, but the H2/CO ratio becomes imbalanced for Fischer-Tropsch reaction
Solution Approach 1:
The patent changes the chemical composition parameters of the off-gas through controlled steam reforming and water-gas shift reactions. By adjusting the steam-to-off-gas ratio and reaction conditions, the process optimizes the H2/CO ratio of the recycled gas to match the requirements of the Fischer-Tropsch reaction, transforming the off-gas from an unsuitable composition to a suitable one for hydrocarbon synthesis.
3Loss of energy
If off-gas is used for power generation, then energy recovery is achieved, but not all off-gas is consumed and utilization efficiency is reduced
Solution Approach 1:
The patent converts the previously harmful or wasted off-gas stream into a beneficial resource by extracting and recycling CO and H2 back to the Fischer-Tropsch reactor. This transforms the off-gas from a waste product that required disposal or low-value combustion into a valuable feedstock that enhances hydrocarbon production and overall process efficiency.
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 stable catalyst performance, increased catalyst lifespan, and optimized hydrocarbon production by effectively managing CO levels and H2/CO ratios, allowing for efficient conversion and utilization of off-gas, particularly when dealing with high CO content off-gas from Fischer-Tropsch reactions.
Implementation Method 1
steps for hydrogenation and reforming to manage CO levels and enhance H2/CO ratios
Implementation Method 2
conversion of off-gas using catalysts comprising iron, copper, zinc, and nickel
Implementation Method 3
performing a Fischer-Tropsch reaction using the mixture as obtained in step (a) and recovering an off-gas from the Fischer-Tropsch reaction
Implementation Method 4
partial oxidation of the carbonaceous feedstock to obtain a mixture comprising hydrogen and carbon monoxide
Data Source
AI summary
The invention relates to a process for preparing a paraffin product from a carbonaceous feedstock comprising (a) partial oxidation of the carbonaceous feedstock to obtain a mixture comprising hydrogen and carbon monoxide, (b) performing a Fischer-Tropsch reaction using the mixture as obtained in step (a) and recovering an off-gas from the Fischer-Tropsch reaction and a paraffin product, (c) subjecting at least a part of the off-gas from the Fischer-Tropsch reaction to conversion using a catalyst comprising iron, or a catalyst comprising iron and chromium, followed by a hydrogenation step (d) using a steam/off-gas mol ratio in the range of between 0.5 and 1.5 and a catalyst comprising copper and zinc, followed by a conversion step (e) using a nickel based catalyst, and (f) preparing a hydrogen comprising gas from at least a part of the off-gas from the Fischer-Tropsch reaction.