Double Condensation Sulfuric Acid Process
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Solution Overview
Problem
Current sulfuric acid production processes from wet feed gases with high SO2 concentrations face challenges in achieving low acid mist emissions and high SO2 conversion efficiency without substantial air dilution, particularly in single wet condensation stages, which limits acid dew point control and increases plant size and costs.
Innovation Solution
A double condensation process involving a first catalytic conversion stage, an intermediate condensing stage, and a final wet condensing stage, where the gas is reheated and passed through a second catalytic conversion stage, allowing for acid dew point control below 240°C and achieving high SO2 conversion rates above 99.5% without significant air dilution, using solid particles as nuclei for acid mist control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If air dilution is used to reduce acid dew point to 260°C in single wet condensation plants, then acid mist emissions can be kept at about 10-20 ppmv, but the gas flow increases substantially requiring larger and more expensive plants
Solution Approach 1:
The condensation process is divided into two separate stages: a first wet condensation stage operating at higher temperature (around 260°C acid dew point) to condense most sulfuric acid vapor, followed by a second wet condensation stage operating at lower temperature (around 100°C acid dew point) to condense remaining acid vapor and control acid mist emissions. This segmentation allows each stage to operate under optimized conditions without requiring substantial air dilution.
Solution Approach 2:
The first condensation stage acts as an intermediary that removes the bulk of sulfuric acid vapor before the gas enters the second condensation stage. This intermediate removal reduces the acid vapor load on the final condenser, enabling it to operate at lower temperatures with higher efficiency in controlling acid mist emissions without needing excessive air dilution.
2Temperature
If air dilution is applied to treat strong feed gases containing 6-30 vol% SO2, then acid dew point can be controlled at 260°C, but the plant size and cost increase due to larger gas flow
Solution Approach 1:
The condensation system is segmented into two stages with different operating temperatures. The first stage handles the high acid vapor load at higher temperature, while the second stage handles the remaining vapor at lower temperature. This segmentation enables effective acid dew point control without requiring the substantial air dilution that would otherwise be needed to handle strong feed gases in a single stage.
Solution Approach 2:
The process utilizes parameter changes by operating the two condensation stages at different temperatures (first stage around 260°C acid dew point, second stage around 100°C acid dew point). This temperature parameter variation allows the system to handle strong feed gases with 6-30 vol% SO2 content without requiring excessive air dilution, thereby avoiding increased plant size and cost.
3Ease of operation
If a single wet condensation stage is used with cooling agent air, then the process is simpler, but acid mist emissions cannot be kept below 10-20 ppmv for gases containing 6-30 vol% SO2
Solution Approach 1:
The condensation process is divided into two sequential wet condensation stages. The first stage operates at higher temperature to condense the majority of sulfuric acid vapor, while the second stage operates at lower temperature to condense remaining vapor and control acid mist emissions. This segmentation achieves acid mist emissions below 10-20 ppmv for strong feed gases while maintaining relative process simplicity.
Solution Approach 2:
The two condensation stages operate continuously in sequence, with the first stage continuously removing bulk acid vapor and the second stage continuously controlling acid mist emissions. This continuous two-stage action maintains effective acid mist control below 10-20 ppmv without requiring complex intermittent operations or substantial air dilution.
4Productivity
If acid dew point is kept below 260°C without substantial air dilution, then plant size is reduced, but achieving acid mist emissions below 10-20 ppmv becomes difficult for strong feed gases
Solution Approach 1:
The condensation system is divided into two stages operating at different temperatures. The first stage operates at higher temperature (around 260°C acid dew point) to condense most acid vapor, while the second stage operates at lower temperature (around 100°C acid dew point) to control acid mist emissions. This segmentation enables acid mist emissions below 10-20 ppmv without requiring substantial air dilution, thereby maintaining reasonable gas flow and plant size.
Solution Approach 2:
The process utilizes temperature parameter changes by operating the two condensation stages at different acid dew points (first stage around 260°C, second stage around 100°C). This parameter variation allows the system to achieve low acid mist emissions below 10-20 ppmv for strong feed gases without requiring substantial air dilution, thus avoiding increased plant size while maintaining effective emission 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 process effectively reduces acid mist emissions to below 5 ppmv and achieves high sulfuric acid concentrations above 98 wt% while maintaining low acid dew points, expanding the window for acid mist control and enabling efficient treatment of wet feed gases with excess water, thus meeting stringent environmental and conversion requirements.
Implementation Method 1
passing the feed gas to a first catalytic conversion step in which SO2 is oxidized to SO3 over one or more catalyst beds
Implementation Method 2
cooling the gas from step (d) to a temperature of 0°C to 100°C above the acid dew point of said gas... in which the remaining sulfuric acid is condensed by cooling of said gas by indirect or direct heat exchange with a cooling medium
Implementation Method 3
providing in the gas, prior to conducting step (f), solid particles acting as nuclei on which the sulfuric acid vapor condenses
Implementation Method 4
cooling the gas by indirect heat exchange with a cooling medium, normally air
Data Source
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AI summary
Process of producing sulfuric acid from feed gases containing 0.1-30% SO2 comprising the steps of : (a) passing the feed gas to a first catalytic conversion step in which SO2 is oxidized to SO3 over one or more catalyst beds, (b) cooling the S03-containing gas from said first contacting step by passing said gas to an intermediate condensing stage withdrawing a gas containing unconverted SO2 and unabsorbed SO3 and withdrawing a product stream of concentrated sulfuric acid, (c) reheating said gas containing unconverted SO2 and unabsorbed SO3, (d) passing the gas from step (c) to a second catalytic conversion step, in which unconverted SO2 is oxidized to SO3 over one or more catalyst beds, (e) cooling the gas from step (d) to a temperature of 0 to 100 °C above the acid dew point of said gas, (f) passing the gas from step (e) with a molar ratio of H2O to SO3 of at least 1.05 calculated under the assumption that SO3 is not hydrated to H2SO4, and acid dew point of below about 240 °C to a final wet condensing stage, in which the remaining sulfuric acid is condensed by cooling of said gas by indirect or direct heat exchange with a cooling medium, (g) providing in the gas, prior to conducting step (f), a content of 1010 to 1013 solid particles per Nm3 per vol% SO3 calculated under the assumption that SO3 is not hydrated to H2SO4, (h) withdrawing from the final wet condensing stage of step (f) a stream of 70-98 wt% sulfuric acid.