SO3 Absorption Energy Recovery with Acid Mist Control
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Solution Overview
Problem
Existing sulfuric acid production processes face challenges in efficiently recovering energy from SO3 absorption due to excessive mist formation and corrosion issues, particularly when operating at high temperatures, which limits the proportion of dilution water that can be injected as steam into the SO3 conversion gas stream.
Innovation Solution
The process involves injecting water vapor into the sulfur oxide-bearing gas stream upstream of the absorption zone to increase the equivalent water vapor content, allowing for higher steam injection rates while controlling acid concentration and temperature differences to minimize mist formation and corrosion, thereby enhancing energy recovery and maintaining acid strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If steam injection rate is increased to enhance energy recovery, then intermediate pressure steam generation increases, but acid mist formation and corrosion worsen
Solution Approach 1:
The patent applies parameter changes by precisely controlling the steam injection rate within a specific range (0.40-1.05 moles per mole SO3) and maintaining acid concentration above the azeotrope (98.3-99.8%). By adjusting these parameters, the process achieves enhanced energy recovery through increased steam generation while preventing excessive acid mist formation that would occur at higher injection rates.
Solution Approach 2:
The patent implements feedback control by continuously monitoring acid concentration and steam injection rate, and adjusting the steam injection accordingly. The system maintains acid concentration within the optimal range by regulating steam injection based on real-time measurements, ensuring energy recovery is maximized while acid mist formation remains controlled.
2Productivity
If steam injection rate is increased to enhance energy recovery, then intermediate pressure steam generation increases, but corrosion issues worsen
Solution Approach 1:
The patent applies parameter changes by maintaining sulfuric acid concentration above the azeotrope (98.3-99.8%) and controlling steam injection rate within specific limits. These parameter adjustments ensure that the acid environment remains stable and less corrosive, allowing enhanced steam generation without proportionally increasing corrosion damage to equipment.
Solution Approach 2:
The patent applies partial action by injecting steam at rates that provide sufficient energy recovery (0.40-1.05 moles per mole SO3) but remain below the threshold that would cause excessive corrosion. This optimized partial injection achieves the necessary energy recovery while preventing the harmful effects of over-injection.
3Productivity
If acid concentration is maintained high to prevent corrosion and control mist, then energy recovery efficiency decreases, but if acid concentration is lowered to enhance energy recovery, then mist formation and corrosion increase
Solution Approach 1:
The patent applies parameter changes by identifying and maintaining acid concentration within the optimal range above the azeotrope (98.3-99.8%). This specific parameter range enables the system to achieve enhanced energy recovery through increased steam generation while simultaneously preventing excessive acid mist formation, resolving the trade-off between energy recovery and mist control.
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 enables a significant increase in intermediate pressure steam generation, up to 25% more than traditional methods, while effectively controlling acid mist and corrosion, thus optimizing energy recovery and operational efficiency.
Implementation Method 1
vapor phase reaction of SO3 and water to form H2SO4 in the vapor phase
Implementation Method 2
recovery of enhanced quantities of energy from the absorption system... the vapor phase heat of reaction of SO3 with water, the heat of condensation of H2SO4, the heat of condensation of SO3, and the liquid phase heat of reaction of SO3 and water
Implementation Method 3
circulating said absorption liquid between said absorption zone and a heat exchanger in which heat generated by reaction of sulfur trioxide and water, condensation of sulfuric acid, and/or absorption of sulfur trioxide into the absorption liquid is transferred to a heat transfer fluid
Implementation Method 4
contacting the sulfur oxide-bearing gas stream with a catalyst for conversion of sulfur dioxide to sulfur trioxide... contacting the conversion gas in a primary heat recovery absorption zone with a primary absorption liquid comprising sulfuric acid, thereby transferring sulfuric acid from the conversion gas to the primary absorption liquid
Implementation Method 5
introducing water vapor into the sulfur oxide-bearing gas upstream of the primary heat recovery absorption zone with respect to the gas flow direction in a proportion sufficient to increase the equivalent water vapor content to at least 0.40 moles per mole total equivalent sulfur oxide gas content
Data Source
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AI summary
This invention relates to the recovery of energy in the manufacture of sulfuric acid, and more particularly to enhanced recovery of energy from the absorption of wet SO3 in sulfuric acid. The invention is further directed to control of mist formation during SO3 absorption, and of the sulfuric acid mist content of the gas stream leaving the SO3 absorption step in a process wherein SO3 absorption energy is recovered from absorption acid in useful form.