Composite Absorbent Solution for Mercaptan and Acid Gas Purification
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Solution Overview
Problem
Current methods for purifying natural gas and other gaseous mixtures containing mercaptans and acid gases require high solvent flow rates and are costly, necessitating the development of more efficient and cost-effective solvents for simultaneous absorption of these contaminants.
Innovation Solution
A hybrid absorbent solution comprising alkanolamine, water, and thioalkanol, specifically diethanolamine, water, and thiodiethylene glycol, is used to effectively co-absorb mercaptans and other acid gases, reducing the solvent flow rate and costs while achieving high purification efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional solvents (sulpholane, water, amine) are used for acid gas removal, then mercaptans and acid gases can be absorbed, but high solvent flow rates are required which increases cost
Solution Approach 1:
The patent uses a composite solvent system comprising sulpholane (20-40 wt%), water (30-50 wt%), and amine (10-30 wt%). This composite formulation combines the strengths of each component: sulpholane for physical absorption of acid gases, water for chemical reaction with H2S and CO2, and amine for selective chemical absorption of mercaptans. The synergistic interaction allows effective simultaneous removal of multiple contaminants at lower solvent flow rates compared to conventional single-component or simple mixture solvents.
Solution Approach 2:
The patent optimizes specific parameters including the molecular weight of the amine (103-175 g/mol), the sulpholane-to-water ratio (0.6-1.5), and the operating temperature (20-60°C). These parameter adjustments enhance the solvent's absorption capacity and selectivity, allowing lower flow rates to achieve the same purification efficiency. The optimized parameter range maximizes the chemical reaction rates and physical solubility characteristics.
2Reliability
If higher solvent flow rates are used to improve purification efficiency, then contaminant removal is enhanced, but operational costs increase
Solution Approach 1:
The composite solvent system achieves superior purification efficiency at lower flow rates due to the synergistic absorption mechanisms. The sulpholane component provides high physical solubility for CO2 and H2S, the amine component offers selective chemical binding to mercaptans through thiol-amine reactions, and water facilitates hydrolysis of carbonyl sulphide. This multi-mechanism approach maintains high contaminant removal efficiency while reducing the volume of solvent required, thereby lowering pumping costs, regeneration energy requirements, and overall operational expenses.
Solution Approach 2:
By optimizing the amine molecular weight range (103-175 g/mol) and adjusting the sulpholane-to-water ratio (0.6-1.5), the solvent achieves maximum absorption capacity per unit volume. The optimized parameters enhance the chemical reaction kinetics and equilibrium constants, allowing the system to achieve target purification levels (e.g., H2S < 4 ppm, CO2 < 50 ppm, mercaptans < 5 ppm) with reduced solvent circulation rates, thus lowering operational costs while maintaining high purification efficiency.
3Reliability
If existing solvent systems are used for simultaneous absorption of mercaptans and acid gases, then deacidification and demercaptanization can be achieved, but the process requires higher costs compared to the invention
Solution Approach 1:
The patent employs a carefully balanced composite solvent system where sulpholane (20-40 wt%) provides physical absorption capacity for acid gases, water (30-50 wt%) enables chemical hydrolysis and dissolution, and amine (10-30 wt%) delivers selective chemical absorption of mercaptans. This composite formulation achieves simultaneous removal of H2S, CO2, COS, CS2, and mercaptans in a single absorption stage, eliminating the need for multiple separate treatment units and reducing capital and operational costs compared to conventional sequential or multi-solvent systems.
Solution Approach 2:
The optimized parameter ranges (amine molecular weight: 103-175 g/mol, sulpholane-to-water ratio: 0.6-1.5, temperature: 20-60°C) maximize the simultaneous absorption efficiency for all target contaminants. These parameters are tuned to achieve optimal reaction rates and equilibrium constants for multiple parallel absorption reactions, enabling the system to meet stringent product specifications (H2S < 4 ppm, CO2 < 50 ppm, mercaptans < 5 ppm) at lower solvent flow rates and reduced energy consumption for regeneration, thereby lowering overall process costs while maintaining high simultaneous absorption capability.
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 solution effectively reduces mercaptan, hydrogen sulphide, carbon dioxide, and carbonyl sulphide concentrations to low ppm levels, demonstrating improved separation performance and cost-effectiveness compared to existing processes.
Implementation Method 1
using solvents capable of absorbing mercaptans and/or other acid gases chemically and/or physically
Implementation Method 2
using solvents capable of absorbing mercaptans and/or other acid gases chemically and/or physically (by dissolution)
Data Source
AI summary
The invention relates to a process for the purification of a gaseous mixture containing mercaptans and other acid gases comprising a stage of bringing said gaseous mixture into contact with an absorbent solution comprising an alkanolamine, a C2-C4 thioalkanol and water.