Buffered Polyprotic Acid Absorption for Sulfur Dioxide Recovery
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Solution Overview
Problem
Conventional methods for removing sulfur dioxide from effluent gases are inefficient, particularly in reducing sulfur dioxide emissions from coal-fired power plants, due to high water vapor content and low sulfur dioxide concentrations, leading to energy and capital expenditure issues, and existing solvents have low absorption capacity and are prone to degradation.
Innovation Solution
A process utilizing a buffered aqueous absorption solution comprising polyprotic carboxylic acid salts, integrated with a sulfur dioxide stripper and heat pump system, to selectively absorb and regenerate sulfur dioxide, controlling sulfate salt concentrations through partial crystallization, and using oxidation inhibitors to prevent degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional absorption or adsorption techniques using aqueous base streams are used to remove sulfur dioxide, then sulfur dioxide removal efficiency is improved (over 95% removal), but capital investment, operating costs, and energy consumption increase due to equipment requirements and base consumption
Solution Approach 1:
The invention changes the chemical parameters of the absorption medium by using buffered aqueous solutions of polyprotic carboxylic acids (pKa 3-10) instead of conventional strong bases. This parameter change allows for effective sulfur dioxide absorption while reducing energy requirements for solvent regeneration and eliminating the need for continuous base consumption, directly resolving the contradiction between removal efficiency and energy consumption
Solution Approach 2:
The invention implements a regenerative absorption cycle where the buffered polyprotic carboxylic acid solution absorbs sulfur dioxide and is then regenerated through heating to release concentrated sulfur dioxide gas. The regenerated absorption solution is recycled back to the absorber, eliminating continuous base consumption and reducing waste disposal costs while maintaining high removal efficiency, addressing both energy loss and operational cost issues
2Quantity of substance
If effluent gases with low sulfur dioxide concentration and high water vapor content are fed to a sulfuric acid plant, then sulfur dioxide recovery is attempted, but water balance and energy balance problems arise when sulfur dioxide concentration is less than 4-5 percent by volume
Solution Approach 1:
The invention extracts sulfur dioxide from dilute effluent gases through selective absorption in buffered polyprotic carboxylic acid solutions, concentrating it to levels suitable for sulfuric acid plant feed (4-5% or higher). This extraction process separates sulfur dioxide from the high water vapor content, solving the water balance problems that would otherwise complicate direct feeding to sulfuric acid plants
Solution Approach 2:
The buffered polyprotic carboxylic acid solution acts as an intermediary medium between the dilute effluent gas and the sulfuric acid plant. It selectively absorbs sulfur dioxide while rejecting water vapor, then releases concentrated sulfur dioxide upon heating. This intermediary process simplifies the water balance control requirements by pre-concentrating sulfur dioxide before plant feed, eliminating the need for complex water management systems
3Quantity of substance
If existing solvents are used for sulfur dioxide absorption, then absorption capacity is limited, but solvent degradation occurs and requires frequent replacement
Solution Approach 1:
The invention uses composite buffered aqueous solutions combining polyprotic carboxylic acids with specific buffers to achieve both high sulfur dioxide absorption capacity and enhanced solvent stability. The buffering system prevents degradation reactions while the polyprotic acid structure provides multiple absorption sites, simultaneously improving absorption capacity and reliability
Solution Approach 2:
The invention optimizes the pKa parameters of the carboxylic acid (selected between 3-10) and controls solution pH through buffering to maximize both absorption capacity and stability. These parameter optimizations ensure the solvent maintains high performance over extended operation periods without degradation, resolving the contradiction between absorption capacity and solvent reliability
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 process achieves efficient sulfur dioxide recovery with reduced energy requirements and controlled sulfate levels, producing a sulfur dioxide-enriched gas while minimizing equipment size and operational costs.
Implementation Method 1
The sulfur dioxide dissolves in water forming sulfurous acid (H2SO3) that in turn reacts with the base to form a salt
Implementation Method 2
The sulfur dioxide dissolves in water forming sulfurous acid (H2SO3) that in turn reacts with the base to form a salt
Implementation Method 3
The sulfur dioxide-enriched absorption solution is heated to desorb the sulfur dioxide and thereby produce a regenerated sulfur dioxide absorption solution and a sulfur dioxide-enriched gas
Implementation Method 4
utilizing an integrated sulfur dioxide stripper and heat pump system
Implementation Method 5
controlling sulfate salt concentrations through partial crystallization
Data Source
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AI summary
This invention relates to processes for the selective removal of contaminants from effluent gases. More particularly, some embodiments of the present invention relate to selective removal and recovery of sulfur dioxide from effluent gases in a sulfur dioxide absorption/desorption process that utilizes a buffered aqueous absorption solution comprising certain weak inorganic or organic acids or salts thereof, preferably certain polyprotic carboxylic acids or salts thereof, to selectively absorb sulfur dioxide from the effluent gas. Oxidation inhibitors may be used. The absorbed sulfur dioxide is subsequently stripped to regenerate the absorption solution and produce a gas enriched in sulfur dioxide content. The regeneration of the absorption solution may include an integrated sulfur dioxide stripper and heat pump system to provide improved energy efficiency. Other embodiments of the present invention relate to a process for simultaneous removal of sulfur dioxide and nitrogen oxides (NOx) from effluent gases and recovery of sulfur dioxide. The process utilizes a buffered aqueous absorption solution further including a metal chelate to absorb sulfur dioxide and NOx from the gas and subsequently reducing the absorbed NOx to form nitrogen. Still further, the present invention provides a process to control sulfate salt contaminant concentration in the absorption solution by partial crystallization and removal of the sulfate salt crystals.