Fischer-Tropsch Hydrocarbon Discharge Control for Stable Fractionator Feed
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Solution Overview
Problem
In Fischer-Tropsch synthesis reaction systems, temporary fluctuations in reaction temperature and slurry liquid surface height lead to unstable flow rates and ratios of light and heavy hydrocarbon oils, making it difficult to maintain constant composition of feedstock fractions for upgrading processes.
Innovation Solution
The process involves setting predetermined discharge flow rates for light and heavy hydrocarbon oils based on estimated production rates, which are calculated using the reaction temperature and chain growth probability, to stabilize the supply to the fractionator, thereby balancing the flow rates and maintaining constant composition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If gas-liquid separation is conducted at high temperature to maintain fluidity of wax fraction, then the fluidity of heavy hydrocarbon oil is improved, but the gas phase contains more light hydrocarbons and the composition stability deteriorates
Solution Approach 1:
The patent separates the gas-liquid separation process into two distinct stages: a first gas-liquid separation at high temperature to maintain wax fluidity, and a second gas-liquid separation at low temperature to recover light hydrocarbons. This segmentation allows each stage to optimize for its specific function without compromising the other.
Solution Approach 2:
The patent introduces an intermediate cooling step between the first and second gas-liquid separations. This intermediate stage acts as a mediator that transitions the system from high-temperature separation to low-temperature separation, enabling efficient light hydrocarbon recovery while maintaining process stability.
2Productivity
If reaction temperature fluctuates temporarily during FT synthesis, then the production rate changes, but the discharge flow rate control becomes difficult and composition stability deteriorates
Solution Approach 1:
The patent implements a feedback control system that continuously monitors the reaction temperature and adjusts the discharge flow rates accordingly. The control unit calculates the appropriate discharge flow rates based on the actual reaction temperature and chain growth probability, ensuring stable composition despite temperature fluctuations.
Solution Approach 2:
The patent dynamically adjusts discharge flow rate parameters based on changing reaction conditions. By modifying the discharge flow rate parameter in response to temperature fluctuations and chain growth probability changes, the system maintains composition stability while adapting to varying productivity levels.
3Productivity
If slurry liquid surface height fluctuates, then the separation efficiency changes, but the discharge flow rate stability and composition consistency deteriorate
Solution Approach 1:
The control unit continuously monitors slurry liquid surface height and uses this feedback to adjust the discharge flow rates. By incorporating liquid surface height information into the control algorithm, the system compensates for fluctuations and maintains consistent discharge flow rates and composition.
4Ease of manufacture
If light and heavy hydrocarbon oils are mixed and fractionally distilled, then the feedstock for upgrading is produced, but the ratio fluctuation makes it difficult to maintain constant composition
Solution Approach 1:
The control unit uses feedback from the reaction temperature and chain growth probability to adjust the discharge flow rates of both light and heavy hydrocarbon oils. This coordinated feedback control ensures that the mixed oil fed to the fractionator has a stable ratio and composition, enabling consistent feedstock quality for upgrading processes.
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 effectively suppresses fluctuations in the ratio and flow rates of hydrocarbon oils supplied to the fractionator, ensuring a stable operation and consistent feedstock quality for subsequent upgrading steps.
Implementation Method 1
a synthesis step of synthesizing hydrocarbons from continuously supplied hydrogen gas and carbon monoxide gas by a Fischer-Tropsch synthesis reaction in presence of a catalyst
Implementation Method 2
a gas-liquid separation step of separating a light hydrocarbon oil from the light hydrocarbons by cooling the light hydrocarbons
Implementation Method 3
a step of separating a heavy hydrocarbon oil from the slurry by filtration
Implementation Method 4
a fractional distillation step of fractionally distilling the mixed oil of the light hydrocarbon oil and the heavy hydrocarbon oil into at least a wax fraction and a fraction that is lighter than the wax fraction
Data Source
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Figure 2
AI summary
In a process for producing hydrocarbons according to the present invention, estimated production rates for a light hydrocarbon oil and a heavy hydrocarbon oil are respectively determined based on a set reaction temperature used when the hydrocarbons are synthesized by a Fischer-Tropsch synthesis reaction, and the discharge flow rates of the light hydrocarbon oil and the heavy hydrocarbon oil from temporary storage buffer tanks (91, 92) during supply to a fractionator (40) are respectively controlled so as to be equal to the respective estimated production rates.