Sulfuric Acid Absorber Segmentation for Mist Reduction
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Solution Overview
Problem
The existing process for producing sulfuric acid by catalytic oxidation of SO2 to SO3 and subsequent absorption in concentrated sulfuric acid results in suboptimal acid concentration in the intermediate absorber, leading to increased mist formation, hydraulic flooding, and high investment costs due to oversized intermediate absorbers, which complicates the absorption process and requires additional filtration and equipment.
Innovation Solution
The process involves an intermediate absorber with a pre-absorber and a post-absorber arrangement where the unabsorbed SO3 is supplied to the post-absorber, and the sulfuric acid is split into two streams, with the first stream injected uncooled into the pre-absorber and the second stream cooled before entering the post-absorber, reducing mist formation and allowing for smaller absorber dimensions, thereby lowering investment costs and improving absorption efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional single-stage absorption is used, then the absorber dimensions become oversized to prevent hydraulic flooding, but this increases investment costs and complicates the absorption process
Solution Approach 1:
The intermediate absorber is divided into two separate absorption stages: a pre-absorber and a post-absorber. The pre-absorber handles the initial absorption of SO3 with cooler acid, while the post-absorber completes the absorption process with warmer acid. This segmentation allows each stage to operate under optimized conditions, preventing hydraulic flooding without requiring oversized dimensions, thereby reducing investment costs while maintaining process stability.
2Productivity
If acid concentration in the intermediate absorber is suboptimal, then mist formation increases, but this requires additional filtration equipment and increases investment costs
Solution Approach 1:
Different acid concentrations and temperatures are applied to different stages of the absorption process. The pre-absorber uses cooler, more concentrated acid to minimize mist formation, while the post-absorber uses warmer acid to maximize absorption efficiency. This local optimization of quality parameters ensures efficient SO3 absorption without excessive mist generation, eliminating the need for additional filtration equipment.
3Reliability
If the absorber is oversized to prevent hydraulic flooding, then investment costs increase, but this does not improve absorption efficiency
Solution Approach 1:
By segmenting the absorption process into two stages with different operating conditions, the system prevents hydraulic flooding through optimized acid flow and temperature management rather than relying on oversized equipment. The pre-absorber operates with cooler acid at controlled flow rates, while the post-absorber handles the remaining SO3 with warmer acid, achieving reliable operation with compact, cost-effective equipment dimensions.
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 design significantly reduces mist formation, prevents hydraulic flooding, and lowers investment costs by optimizing the size and operation of the absorbers, while maintaining efficient SO3 absorption and reducing the risk of corrosion and emissions.
Implementation Method 1
the SO3 containing gas is traditionally fed counter currently to concentrated sulfuric acid and absorbed in at least one of these two absorbers
Implementation Method 2
the SO2 is converted into sulfur trioxide (SO3) in a multistage converter with the aid of a solid catalyst
Implementation Method 3
catalytic oxidation of SO2 to SO3
Implementation Method 4
the purified exhaust gas is dried in a drying tower with concentrated sulfuric acid of e.g. 94 - 96 wt.-% H2SO4, i.e. quantitatively freed from water moisture
Data Source
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AI summary
A process and its relating plant for producing sulfuric acid by catalytic oxidation of SO2 to SO3 and subsequent absorption of the SO3 in concentrated sulfuric acid in an intermediate and a final absorber stage. Therein, the intermediate absorber stage features a pre-absorber and a post-absorber. These two absorbers arranged such that the not-absorbed SO3 leaving the pre-absorber is supplied to a post-absorber and such that the sulfuric acid leaving the post-absorber is split into two streams of which the first stream is recirculated back in the pre-absorber and the second stream is at least partly passed into the post-absorber. The first stream is uncooled directly injected into the pre-absorber with a temperature between 80 and 200 °C, preferably between 100 and 150°C and the second stream passes a cooling and is at least partly fed into the post-absorber with a temperature between 60 and 90 °C.