Supercritical CO2 Decoking of Hydrocarbon Processing Coils
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Solution Overview
Problem
Current methods for removing coke and carbonaceous deposits from hydrocarbon processing equipment, such as steam-air decoke and spalling, are inefficient, environmentally harmful, or require extensive downtime, and struggle with non-combustible materials and metal damage.
Innovation Solution
A method involving the sorption of a pressurized gas, primarily carbon dioxide, into coke deposits to weaken and facilitate their removal through depressurization, which can be repeated as necessary, and optionally followed by mechanical cleaning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If steam-air decoke (SAD) is used to remove coke deposits, then coke removal effectiveness is improved, but processing time increases to 36-48 hours and metal damage occurs
Solution Approach 1:
The patent changes the chemical parameters of the cleaning medium from oxidative (steam-air) to solvating (supercritical CO2). By adjusting pressure and temperature parameters to achieve supercritical state, the cleaning process is accelerated from 36-48 hours to a significantly shorter duration while maintaining effectiveness through enhanced mass transfer properties of the supercritical fluid
Solution Approach 2:
The patent replaces the thermal-mechanical SAD process (heating, oxidation, cooling cycles) with a pressure-controlled supercritical fluid extraction system. This substitution eliminates the need for repeated thermal cycling and oxidation reactions, reducing processing time and avoiding thermal damage to metal surfaces
2Reliability
If steam-air decoke (SAD) is used to remove coke deposits, then coke removal effectiveness is improved, but harmful emissions are generated
Solution Approach 1:
The patent uses carbon dioxide as an inert supercritical fluid medium instead of combustible steam-air mixtures. The CO2 system operates without combustion, eliminating harmful emissions of CO, CO2 from burning, and H2. The inert nature of CO2 prevents oxidative damage to equipment while effectively solvating and removing coke deposits
Solution Approach 2:
The patent converts the typically harmful CO2 emissions from industrial processes into a beneficial cleaning agent. By utilizing CO2 in its supercritical state, the system achieves effective coke removal without combustion, transforming a greenhouse gas concern into an environmentally friendly cleaning solution that leaves no harmful emissions
3Loss of time
If spalling is used to remove coke deposits, then processing time is reduced, but coke removal completeness decreases and tubing damage may occur
Solution Approach 1:
The patent replaces the mechanical thermal shock method of spalling with a chemical-solvating supercritical CO2 process. Instead of relying on thermal expansion and contraction to fracture coke, the supercritical fluid penetrates and dissolves coke deposits, achieving complete removal without the need for aggressive thermal cycling that can damage tubing
Solution Approach 2:
The patent utilizes pressure and temperature parameter changes to achieve supercritical state of CO2, which enables deep penetration into and complete dissolution of coke deposits. This parameter-controlled approach ensures complete coke removal while avoiding the mechanical stress and potential tubing damage associated with traditional spalling methods
4Reliability
If abrasive cleaning methods are used to remove coke deposits, then removal effectiveness is improved, but metal surface damage increases
Solution Approach 1:
The patent replaces all abrasive mechanical cleaning methods (studded pigs, SandJet, high-velocity gas streams) with a non-mechanical supercritical CO2 extraction process. The supercritical fluid removes coke through solvation and diffusion mechanisms, completely eliminating mechanical abrasion that damages metal surfaces, grooves walls, and reduces tube thickness
Solution Approach 2:
The supercritical CO2 system performs self-cleaning by penetrating into and dissolving coke deposits from the inside out. The CO2 fluid automatically reaches all surfaces including complex geometries and deposits, removing coke without requiring contact with abrasive elements that would damage the metal substrate
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
Effectively reduces coke hardness and mass on equipment surfaces, allowing for efficient removal with minimal environmental impact and reduced downtime, preserving metal integrity and preventing further coke formation.
Implementation Method 1
exposing the equipment to a pressurized stream of gas, allowing sorption of gas into the coke
Implementation Method 2
allowing sorption of gas into the coke
Data Source
AI summary
The present invention concerns a method of weakening and removal of coke or carbonaceous material which deposits as a result of thermal cracking of hydrocarbons on the inner walls of coils, piping, tubing, and in general, hydrocarbon processing equipment.