Fischer-Tropsch Outer Wax Loop Temperature Control
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Solution Overview
Problem
The Fischer-Tropsch synthesis process faces challenges in controlling operating conditions, particularly in the outer wax separation loop, leading to catalyst deactivation and increased catalyst costs due to high water partial pressure, which affects hydrocarbon production efficiency.
Innovation Solution
The process involves controlling the water to hydrogen partial pressure ratio in the external wax separation loop by reducing the temperature in the degassing phase, maintaining it below a certain threshold to prevent catalyst degradation and maintain hydrocarbon production stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the temperature in the outer wax separation loop is not controlled, then the process operation is simple, but the catalyst deactivates due to high water partial pressure
Solution Approach 1:
The patent applies parameter changes by controlling the temperature in the outer wax separation loop to maintain the PH2O:PH2 ratio below a critical threshold. By adjusting the temperature parameter, the system prevents catalyst deactivation while managing the complexity of the separation process.
Solution Approach 2:
The patent implements feedback control by monitoring the PH2O:PH2 ratio and adjusting the temperature in the outer loop accordingly. This feedback mechanism ensures catalyst stability by maintaining operating conditions within safe thresholds, resolving the contradiction between reliability and operational simplicity.
2Duration of action of stationary object
If the PH2O:PH2 ratio is not controlled, then the process operation is simple, but the catalyst deactivates and requires frequent top-ups
Solution Approach 1:
The patent changes the operating parameters by controlling the PH2O:PH2 ratio through temperature adjustment in the outer loop. This extends catalyst life by preventing deactivation conditions, while the control mechanism remains integrated into the existing process framework.
Solution Approach 2:
The system achieves self-service by using the outer wax separation loop's temperature control to automatically regulate the PH2O:PH2 ratio. This self-regulating mechanism protects the catalyst without requiring external intervention or complex additional control systems.
3Productivity
If the temperature in the degassing phase is not reduced, then the process is easier to operate, but the hydrocarbon production becomes unstable
Solution Approach 1:
The patent applies parameter changes by reducing the temperature in the degassing phase to stabilize hydrocarbon production. This temperature adjustment ensures consistent product output while the control strategy is embedded in the process design, maintaining ease of operation.
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 stabilizes catalyst performance, reduces catalyst top-ups, and improves process economy by maintaining constant hydrocarbon production and extending catalyst life.
Implementation Method 1
separation in a degassing means of the fraction withdrawn during step a) into a gas phase and a suspension containing the liquid and the solid
Implementation Method 2
controlling the water to hydrogen partial pressure ratio in the external wax separation loop by reducing the temperature in the degassing phase
Data Source
AI summary
The present invention relates to a method for synthesising hydrocarbons from a feedstock including synthesis gas, in which a solid catalyst including cobalt is used in a three-phase reaction section operated such that said catalyst is kept in suspension in a liquid phase by circulating a gas phase from the bottom toward the top of said reaction section, said method including an outer wax-separation loop, characterised in that: 1) the theoretical ratio of PH2O : PH2 in the outer wax-separation loop is determined by the following calculation: theoretical PH2O : PH2 = Cv/(R1 - Rft x Cv), wherein Cv = (COinput - COdegas) / COinput 2, R1 = H2 input / COinput and Rft = (H2 input - H2 degas) / (COinput - COdegas); 2) if the theoretical ratio of P H2O : P H2 determined in step 1) has a value no lower than R threshold, the temperature in the degassing means of the outer wax-separation loop is reduced; 3) repeating steps 1) and 2) until the theoretical ratio of PH2O : PH2 has a value that is strictly lower than Rthreshold, wherein Rthreshold is comprised between 0.1 and 1.1. 3