Glycol Dehydration Mercury Removal Using Thermally Stable Complexing Agents
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Solution Overview
Problem
Existing adsorbents like activated carbon, zeolites, and copper sulfide are ineffective in removing mercury upstream of glycol dehydrators due to the presence of water vapor, leading to mercury distribution in the dry natural gas and other plant sections.
Innovation Solution
Incorporating a thermally stable complexing agent, such as sodium polysulfide or DODT, into the glycol solvent to selectively react with and capture mercury in the gas phase before dehydration, followed by regeneration and filtration to concentrate mercury for efficient removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If adsorbents like activated carbon, zeolites, or copper sulfide are used to remove mercury, then mercury removal to specifications is achieved, but the adsorbents become ineffective when water vapor is present upstream of glycol dehydrators
Solution Approach 1:
A complexing agent is introduced as an intermediary substance that selectively binds to mercury in the presence of water vapor. The complexing agent forms stable complexes with mercury ions, enabling effective mercury removal upstream of the glycol dehydrator where water vapor would otherwise interfere with traditional adsorbents.
Solution Approach 2:
The invention changes the chemical environment by adding a complexing agent that alters mercury's chemical form from elemental or ionic mercury to mercury-complex compounds. This parameter change in mercury's chemical state enables effective capture by the complexing agent even in the presence of water vapor, overcoming the limitation of traditional adsorbents.
2Reliability
If traditional adsorbents are placed downstream of glycol dehydration, then mercury is removed from dry natural gas, but mercury distributes outside the dry natural gas in the gas processing plant
Solution Approach 1:
The complexing agent performs preliminary mercury capture action upstream of the glycol dehydrator, removing mercury from the wet natural gas before it enters the dehydration system. This preliminary action prevents mercury from distributing to other plant sections and concentrates it in the glycol solvent for subsequent removal.
Solution Approach 2:
The complexing agent extracts mercury from the natural gas stream by forming stable complexes, separating mercury from the gas phase and concentrating it in the liquid glycol phase. This extraction process removes mercury upstream, preventing its distribution throughout the plant while maintaining effective removal from the final dry gas product.
3Productivity
If glycol solvent recirculation is used for water removal, then dehydration efficiency is improved, but mercury accumulates in the recirculated solvent
Solution Approach 1:
The complexing agent acts as an intermediary that selectively binds mercury in the recirculated glycol solvent, forming stable complexes that keep mercury in solution. This allows continuous recirculation of the glycol solvent for efficient dehydration while the complexing agent continuously captures any mercury that dissolves, preventing mercury accumulation issues.
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
The process effectively captures and concentrates mercury in the glycol solvent, enhancing mercury removal efficiency by up to 80% and reducing its distribution in the gas processing plant, improving operational reliability.
Implementation Method 1
The complexing agent selectively reacts with mercury in the wet natural gas to remove the mercury from the dry natural gas product
Implementation Method 2
The glycol absorbs water vapor from the natural gas, producing the dry natural gas product
Implementation Method 3
Rich glycol solvent containing water and other components is recycled by vaporizing water at low pressure and elevated temperatures
Data Source
AI summary
The present invention is directed to the removal of mercury in a gas dehydration process using thermally table chemical additives. In the process a complexing agent is added to a recirculated glycol solvent as part of the glycol solution feed to the dehydration liquid contactor and recirculated continuously with the glycol solvent. The complexing agent selectively reacts with mercury in the wet natural gas to remove the mercury from the dry natural gas product.