Stepwise Oil-Water Separation in Fischer-Tropsch Process
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Solution Overview
Problem
Current oil-water separation methods in the Fischer-Tropsch process, such as gravity settling, are inefficient, occupy large areas, and require complex operation control systems, leading to high costs and low separation efficiency due to severe oil-water emulsification and limited ability to separate smaller droplets.
Innovation Solution
A stepwise oil-water separation method using oil-gas washing, incorporating a primary oil-water separator with T-shaped liquid-gas separation, followed by CPI modules and conjugate fiber modules for droplet agglomeration and separation, allowing for fast and efficient separation of oil and water based on droplet size, reducing the need for auxiliary systems and land occupation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If gravity settling separation is used for oil-water separation, then the separation process is simple, but the separation efficiency is low and the device occupies a large area
Solution Approach 1:
The separation process is divided into multiple stages: primary separation in the centrifugal separator, secondary separation in the CPI modules, and tertiary separation in the nanofiber coalescence modules. Each stage handles different droplet size ranges, progressively improving separation efficiency without requiring a single large gravity settler
Solution Approach 2:
The patent replaces the traditional gravity-based mechanical settling system with a centrifugal separation system that uses rotational force. The centrifugal separator generates centrifugal force to separate oil-water emulsion, dramatically reducing separation time from hours to minutes while maintaining process simplicity
2Device complexity
If gravity settling separation is used for oil-water separation, then the equipment structure is simple, but the device occupies a large area and costs a lot of materials
Solution Approach 1:
The patent employs a nested modular structure where multiple CPI modules are arranged in series within a compact footprint, and nanofiber coalescence modules are integrated within the separation train. This nesting approach allows multiple separation functions to be stacked vertically rather than spread horizontally, reducing land occupation while maintaining structural clarity
Solution Approach 2:
The patent transitions from horizontal spreading of separation tanks to vertical stacking of modular separation units. The centrifugal separator, CPI modules, and nanofiber modules are arranged in a vertical flow path, utilizing the vertical dimension to reduce the horizontal area occupied by the separation system
3Ease of manufacture
If separate washing device is arranged for washing and recycling, then the washing function is complete, but the operation control system is complicated and costs much
Solution Approach 1:
The patent combines the washing function and recycling function into a single integrated system. The centrifugal separator performs both separation and washing of hydrocarbon-containing water, while the CPI and nanofiber modules simultaneously achieve oil removal and water recovery. This merging eliminates the need for separate control systems for washing and recycling operations
Solution Approach 2:
The separation modules are designed to perform multiple functions: the centrifugal separator performs both oil-water separation and hydrocarbon washing, while the CPI and nanofiber modules handle both deoiling and dewatering. This multi-functionality reduces the number of dedicated systems needed and simplifies the overall control architecture
4Reliability
If long static settling separation time is used, then the separation completeness is improved, but the productivity is reduced and land occupation increases
Solution Approach 1:
The patent replaces gravity-based static settling with dynamic centrifugal separation followed by enhanced coalescence mechanisms. The centrifugal force accelerates droplet separation, while the CPI and nanofiber modules provide enhanced coalescence for smaller droplets, achieving complete separation in minutes rather than hours
Solution Approach 2:
The patent employs nanofiber coalescence modules with porous structures that provide large surface area for droplet capture and coalescence. The nanofiber matrix with controlled porosity enables efficient separation of fine emulsified droplets that would otherwise require prolonged settling, dramatically reducing separation time while maintaining completeness
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 method significantly reduces separation time, improves efficiency, and lowers investment costs by integrating dehydration and deoiling functions, achieving water content below 0.02% and oil content below 0.01% in the separated streams, while also recycling hydrocarbons and reducing the complexity of subsequent processes.
Implementation Method 1
realizing fast liquid-gas separation in the T-shaped liquid-gas separator, wherein the the low gas separated is discharged from the top of the primary oil-water separator
Implementation Method 2
undergoes fast dehydration by successive going through the first CPI oil-water fast separation module and hydrophilic droplet agglomeration module to isolate water droplets with particle size larger than 30μm
Implementation Method 3
Water-cut oil and oily water are separated through settling action of high-pressure separator
Implementation Method 4
water droplets with 3-30μm particle size are removed in in-depth dehydrator to get light oil with water content less than 0.02%
Implementation Method 5
oil sewage flows from the right-side end socket of primary oil-water separator towards left and passes through the second CPI oil-water fast separation module and oleophilic droplet agglomeration module successively for rapid oil removal, wherein oil droplets with particle size larger than 25μm are separated
Data Source
Figure 1~2
Figure 3
AI summary
This invention involves a method of stepwise oil-water separation by oil-gas washing in Fischer-Tropsch process. At first, after mixed washing and hydrocarbon composition, light oil containing about 0.5-6% synthetic water and low gas containing trace hydrocarbon enters from the left-side end socket into the primary oil-water separator, and sewage containing 0.05-0.5% oil enters into the separator from the right-side end socket; purified low gas is discharged from the top and the mixed liquid enters into in-depth dehydrator after being discharged. Discharged light oil contains about 0.05-0.5% of water; sewage on the left side is discharged after entering water drum and sewage after deoiling on the right side is discharged on the right side of clapboard and enters into in-depth oil eliminator. Discharged oil contains about 0.03-0.6% water; after in-depth deoiling and dehydration through conjugate fiber module weaved in particular form in in-depth dehydrator and oil eliminator, light oil containing less than 0.02% water and sewage containing less than 0.01% oil are discharged separately. The method of combined oil-water separation and stepwise separation provided by this invention is able to make fast and efficient oil dehydration and sewage deoiling, and to recycle oil to the maximum extent.