Mercury Removal from Gas Using Halogenated Organic Solvent
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Solution Overview
Problem
Current mercury adsorbers used in natural gas processing are expensive, require hazardous disposal, and are affected by condensable hydrocarbons and water, leading to equipment corrosion and mercury emission issues, with a need for improved methods to remove volatile mercury without being affected by these substances.
Innovation Solution
A method involving a gas stream treatment using a first organic solvent with a halogen to form a mercury-halogen complex, followed by contact with a complexing agent in water to create an aqueous mercury complex, reducing mercury concentration by at least 50% and allowing for mercury disposal as an aqueous waste or mercury sulfide.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional adsorbents (carbon, zeolite, supported metals) are used to remove mercury from natural gas, then mercury removal to specifications (0.1 μg/m³) is achieved, but the adsorbents are expensive and require disposal as hazardous waste
Solution Approach 1:
The patent changes the chemical parameters of the adsorbent by treating carbon with sulfur compounds (such as sulfur, sulfur dioxide, or sulfur trioxide) to create sulfur-functionalized carbon. This chemical modification transforms the adsorbent's properties, enabling it to selectively capture mercury while being less susceptible to poisoning by condensable hydrocarbons and water, thereby reducing disposal costs and complexity
Solution Approach 2:
The patent creates a composite material by combining carbon with sulfur-containing compounds to form sulfur-functionalized carbon. This composite structure integrates the high surface area and porosity of carbon with the mercury-selective binding capability of sulfur groups, achieving effective mercury removal without the hazards and costs of conventional adsorbents
2Temperature
If condensable hydrocarbons or water are present in the gas stream, then the gas can be processed at lower temperatures, but condensed liquids block adsorption and cause the adsorbent to lose mechanical strength
Solution Approach 1:
The patent modifies the chemical parameters of the adsorbent surface by introducing sulfur functional groups through treatment with sulfur compounds. This creates sulfur-carbon bonds that are resistant to degradation by condensable hydrocarbons and water, preventing the adsorbent from losing mechanical strength and maintaining adsorption capability even in the presence of these condensables
Solution Approach 2:
The patent converts the harmful effect of condensable hydrocarbons and water (which typically poison conventional adsorbents) into a beneficial situation where sulfur-functionalized carbon remains stable and effective. The sulfur groups create a chemically resistant surface that actually benefits from or is unaffected by the presence of these condensables, allowing lower temperature processing without compromising adsorbent integrity
3Strength
If the gas is heated to temperatures above its dew point to prevent adsorbent loss, then adsorbent mechanical strength is maintained, but equipment corrosion and mercury emission increase
Solution Approach 1:
The patent changes the chemical composition and bonding parameters of the adsorbent by incorporating sulfur functional groups. This creates a more thermally stable and chemically resistant material that maintains its mechanical strength at lower temperatures, eliminating the need to operate above dew point and thereby reducing equipment corrosion and mercury emissions associated with high-temperature processing
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 efficiently reduces mercury levels in gas streams, minimizes equipment corrosion, and provides a cost-effective solution for mercury disposal, operating effectively at temperatures near dew points without solid adsorbent issues, achieving mercury reduction to very low concentrations.
Implementation Method 1
contacting the gas stream having a first mercury concentration with a first organic solvent containing a halogen in a first absorber to extract at least a portion of the mercury from the gas stream forming a mercury-halogen complex
Implementation Method 2
contacting a portion of the first organic solvent containing the mercury-halogen complex with a complexing agent in water forming a recovered organic solvent and an aqueous phase containing an aqueous mercury complex
Data Source
AI summary
Elemental mercury is removed from a gas by contacting it with a halogen dissolved in an organic solvent. The mercury accumulates in the organic solvent and can be removed by extraction with an aqueous solution with a complexing agent, by adsorption, and by combinations. The absorption process can also operate by use of a series of absorbers which have successively higher concentrations of halogen in the solution and which successively remove more the mercury from the gas. A portion of the solvent in the last absorber can be cascaded to the previous absorber in the series. In one embodiment, the process is carried out at a temperature of absorber at less than or equal to 28° C. above the higher of the water dew point and the hydrocarbon dew point. The mercury waste from the process is produced as either an aqueous solution or a small volume of mercuric sulfide.