Sequential Mixing System for Crude Oil Desalting
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Solution Overview
Problem
Desalting heavy crude oil in refineries is challenging due to its high viscosity and density, leading to stable emulsions that are difficult to break, resulting in inefficient salt removal and increased corrosion risks.
Innovation Solution
A sequential mixing process involving a mixing valve that creates small water droplets to capture salt, followed by a coalescer mixer that increases droplet size for easier separation, aided by an electric field to enhance coalescence, optimizing shear rates and mixing energy to improve desalting efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single mix valve is used to mix crude oil and water, then the mixing process is simple, but the emulsion becomes stable and difficult to break, reducing desalting efficiency
Solution Approach 1:
The single mixing valve is divided into two sequential mixing valves. The first mixing valve creates initial emulsion with salt transfer, while the second mixing valve further breaks down the emulsion to improve separation. This segmentation resolves the contradiction by maintaining simple valve-based mixing while achieving better desalting efficiency through staged mixing processes.
Solution Approach 2:
The first mixing valve performs preliminary mixing and salt transfer before the crude oil enters the desalter. This preliminary action prepares the emulsion for more effective separation in the desalter, resolving the contradiction by pre-conditioning the mixture to improve overall desalting efficiency without complicating the main separation process.
2Reliability
If high shear mixing is applied to break emulsions, then salt removal improves, but water droplets become too small and remain entrained with crude oil
Solution Approach 1:
The mixing process is segmented into two stages with different shear rates. The first stage uses high shear to break emulsions and transfer salt, while the second stage uses lower shear to allow water droplets to coalesce into larger sizes for better separation. This resolves the contradiction by applying different mixing intensities at different stages.
Solution Approach 2:
The sequential mixing valves are positioned to create periodic mixing zones along the flow path. The first valve creates high shear conditions, then the flow proceeds to the second valve with different mixing characteristics. This periodic variation in mixing intensity allows both salt removal and water droplet coalescence to occur effectively.
3Ease of operation
If heavy crude oil is processed in a traditional desalter, then the process is straightforward, but high viscosity and density create stable emulsions that are difficult to separate
Solution Approach 1:
The desalting process is segmented into two sequential mixing stages followed by separation. The first mixing valve handles initial emulsion formation and salt transfer, while the second mixing valve addresses the stable emulsion characteristics of heavy crude. This segmentation maintains operational simplicity while improving desalting efficiency for heavy crude oils.
Solution Approach 2:
The sequential mixing system changes the mixing parameters (shear rate, mixing intensity) between the two valves to specifically address the high viscosity and density characteristics of heavy crude oil. This allows the process to remain simple while adapting to the challenging properties of heavy crude through parameter optimization.
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 effectively increases desalting efficiency by breaking stable emulsions and reducing water carryover, thereby minimizing salt carryover and corrosion risks while improving energy utilization in refineries.
Implementation Method 1
The mixing of the oil phase and the water phase is carried out using a single mix valve which creates the water and oil emulsion. The pressure drop across the mix valve determines the size of the water droplets in the emulsion.
Implementation Method 2
Within the desalter settling vessel, water droplets undergo coalescence under the influence of electrical and gravitational fields.
Implementation Method 3
Within the desalter settling vessel, water droplets undergo coalescence under the influence of electrical and gravitational fields. large water droplets settle down to the bottom of the desalter tank
Implementation Method 4
Within the desalter settling vessel, water droplets undergo coalescence under the influence of electrical and gravitational fields.
Data Source
AI summary
A system for desalting crude oil includes delivering a stream of salty crude oil and wash water into a mixing valve, mixing the stream of salty crude oil and wash water through the mixing valve to create a mixed stream of desalted crude oil and salty wash water, delivering the mixed stream of desalted crude oil and salty wash water to a static mixer, and mixing the mixed stream of crude oil and wash water in the static mixer. Within the static mixer, the mixed stream is mixed in a coalescing regime to coalesce smaller droplets of water into larger droplets of water. The mixed stream is subjected to an electric field to cause additional coalescence before being directed to a desalter where the salty wash water is separated from the desalted crude oil.