Polyvalent Cation Removal from Mono Ethylene Glycol
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Solution Overview
Problem
Current methods for removing divalent cations from mono ethylene glycol (MEG) are complex, energy-intensive, and require chemical additions or preheating, which can lead to scale issues and increased costs in the regeneration process.
Innovation Solution
A method involving heating the aqueous MEG to 60-120°C to precipitate salts, followed by carbon dioxide separation in a flash separator, and subsequent distillation to produce hot dewatered MEG, which is then recirculated to maintain heat and enhance precipitation, allowing for efficient removal of polyvalent cations without chemical additions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If chemicals such as NaOH, NaHCO3, or Na2CO3 are added to increase pH and carbonate concentration to precipitate divalent cations, then the precipitation efficiency is improved, but the process complexity increases and chemical costs rise
Solution Approach 1:
The invention extracts and removes divalent cations from MEG through thermal precipitation followed by filtration, eliminating the need for chemical additives. The harmful chemicals are taken out of the process entirely, replacing them with a physical-chemical method using heat and filtration equipment.
Solution Approach 2:
The invention introduces an intermediary filtration step between precipitation and the final MEG product. The filter acts as a mediator that separates the precipitated cations from the MEG stream, enabling effective removal without requiring chemical additives or complex reclamation stages.
2Reliability
If chemicals are added to remove salts, then salt removal efficiency is improved, but sodium concentration and alkalinity increase in the MEG
Solution Approach 1:
The invention extracts divalent cations through thermal precipitation and physical filtration, completely avoiding the introduction of sodium-containing chemicals. This extraction method removes harmful salts without adding unwanted substances, maintaining low sodium concentration in the treated MEG.
3Reliability
If a reclaimer stage is included to control salt concentration, then salt level control is improved, but the process becomes more complicated and energy consumption increases
Solution Approach 1:
The invention performs preliminary precipitation of divalent cations before the main distillation process by heating rich MEG to 60-120°C. This preliminary action removes most salts in advance, preventing scale formation in the reboiler and eliminating the need for a separate reclaimer stage, thereby reducing overall energy consumption.
Solution Approach 2:
The invention converts the harmful effect of heat (which could cause scale formation in the reboiler) into a beneficial precipitation step before distillation. By deliberately heating the MEG to precipitate salts first, then filtering them out, the process prevents reboiler scaling while using the same thermal energy efficiently.
4Device complexity
If heating alone is used to precipitate polyvalent cations, then the process simplicity is improved, but the precipitation completeness is insufficient and large retention tanks are required
Solution Approach 1:
The invention maintains continuous heating of the MEG stream through the precipitation zone, ensuring complete precipitation of divalent cations. The continuous thermal action prevents the need for large retention tanks, as precipitation occurs efficiently along the flow path rather than requiring batch processing in large vessels.
5Productivity
If rich MEG is heated to high temperature in the reboiler, then water removal efficiency is improved, but scale formation from precipitated salts increases
Solution Approach 1:
The invention performs preliminary precipitation and filtration of divalent cations before the MEG enters the reboiler. By removing the scaling-prone salts in advance through thermal precipitation and filtration, the reboiler operates with cleaner feed, maintaining high water removal efficiency without scale formation on heating surfaces.
Solution Approach 2:
The invention rushes through the precipitation and filtration steps quickly and efficiently before the MEG enters the reboiler. By completing the salt removal process in a compact, rapid sequence, the process prevents scale formation without requiring the MEG to linger at high temperatures in the reboiler, thus maintaining productivity while avoiding harmful scale deposition.
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 simplifies the process, reduces energy consumption, and effectively precipitates divalent cations before they reach distillation equipment, minimizing scaling and equipment contamination, while allowing for efficient separation and storage of clean MEG.
Implementation Method 1
heating the aqueous mono ethylene glycol to 60-120°C to produce a heated mixture, causing precipitation of at least part of the salts and release of at least part of the dissolved carbon dioxide
Implementation Method 2
causing precipitation of at least part of the salts
Implementation Method 3
release of at least part of the dissolved carbon dioxide
Implementation Method 4
separation of released carbon dioxide from the heated mixture in a flash separator
Implementation Method 5
distillation of at least part of the water from the heated mixture in a reboiler, to yield hot dewatered mono ethylene glycol (lean MEG)
Implementation Method 6
a first part of the hot dewatered mono ethylene glycol which comprises particles of salts of divalent cations is led back to the aqueous mono ethylene glycol supplied in step a) to provide at least part of the heat for heating the aqueous mono ethylene glycol in step b)
Data Source
Figure 1
AI summary
The invention relates to a method and an apparatus for the removal of polyvalent cations, in particular divalent cations, from mono ethylene glycol. Mono Ethylene Glycol (MEG) is used to prevent hydrate formation in pipelines transporting gas, condensate and water. It may also contribute to pipeline corrosion control. The invention describes a method for the removal of polyvalent cations from mono ethylene glycol, comprising providing a feed of aqueous mono ethylene glycol comprising dissolved gas and salts of divalent cations (rich MEG), heating the aqueous mono ethylene glycol to a heated mixture, causing precipitation of at least part of the salts and release of at least part of the dissolved gas, in particular carbon dioxide, separation of released gas from the mono ethylene glycol, separation of at least part of the precipitated salts from the mono ethylene glycol, distillation of at least part of the water from the heated mixture, to yield hot dewatered mono ethylene glycol (lean MEG), wherein a first part of the hot dewatered mono ethylene glycol is lead back to the aqueous mono ethylene glycol feed to provide at least part of the heat for heating the aqueous mono ethylene glycol.