Pre-scrubber with Base Injection for High SO2 Gas Streams
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Solution Overview
Problem
Existing methods for processing gas streams with varying sulfur dioxide (SO2) content, particularly those with temporary peaks, are inefficient and unreliable, often resulting in high SO2 emissions due to the need for complex and costly caustic wash systems that are not frequently used and can malfunction after long standby periods.
Innovation Solution
A process and system that involve pre-scrubbing the gas stream with an aqueous solution containing a strong base, followed by absorption and regeneration, allowing for the recycling of the medium and optional feeding to a Sulfur Removal Unit, which is designed to handle high SO2 content streams effectively and maintain reliability even during infrequent operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a caustic wash system is used to handle high SO2 content streams, then SO2 removal capability is improved, but system complexity and cost increase significantly
Solution Approach 1:
The pre-scrubber unit is designed to perform multiple functions: it can operate with water alone for normal conditions, and can accommodate periodic injection of strong base solutions (such as caustic soda) when high SO2 content streams need to be handled. This eliminates the need for a separate dedicated caustic wash system, reducing overall system complexity while maintaining the capability to handle high SO2 emissions.
2Object-affected harmful factors
If a caustic wash system is installed for occasional use, then high SO2 content streams can be handled, but reliability decreases due to long standby periods
Solution Approach 1:
The pre-scrubber serves as a universal unit that handles both normal and high SO2 content streams. By continuously operating with water and periodically injecting strong base, it maintains readiness and reliability without long standby periods, unlike a separate dedicated caustic wash system that would sit idle most of the time.
Solution Approach 2:
The pre-scrubber is prepared in advance with water circulation and is equipped with injection points for strong base solutions. This preliminary preparation ensures that when high SO2 content streams occur, the system can immediately respond by injecting the base, maintaining reliability without requiring a separate pre-prepared caustic wash system.
3Object-affected harmful factors
If a dedicated caustic wash system is used for high SO2 streams, then SO2 removal is effective, but operational cost increases
Solution Approach 1:
The pre-scrubber unit is designed to handle both normal and high SO2 content streams using the same infrastructure. By injecting strong base periodically into the existing pre-scrubber, the system avoids the need for a separate dedicated caustic wash installation, thereby reducing capital expenditure and operational costs while maintaining effective SO2 removal capability.
4Device complexity
If regular SO2 removal process is used, then system simplicity is maintained, but capability to handle temporary high SO2 peaks is insufficient
Solution Approach 1:
The pre-scrubber operation is made dynamic by allowing switching between two modes: normal operation with water alone for low SO2 content, and enhanced operation with periodic strong base injection for high SO2 content peaks. This dynamic adaptability maintains process simplicity during normal operation while providing the capability to handle temporary high SO2 peaks when needed.
Solution Approach 2:
The chemical parameters of the pre-scrubber are changed periodically by injecting strong base solutions (such as caustic soda) into the water circulation system. This parameter change allows the pre-scrubber to handle high SO2 content streams effectively while maintaining the same physical infrastructure, thus preserving process simplicity while enhancing SO2 removal capability during peaks.
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 provides a simple, cost-efficient, and reliable method for processing gas streams with varying SO2 content, including temporary peaks, by effectively reducing SO2 emissions and maintaining system functionality even after extended standby times.
Implementation Method 1
contacting the feed gas stream with an aqueous solution comprising a strong base in the pre-scrubbing zone to form a sulfur dioxide lean treated gas stream and an aqueous solution comprising sulfite and/or bisulfite ions
Implementation Method 2
contacting at least a part of the pre-scrubbed gas stream obtained in step (i) with an aqueous lean absorbing medium in an absorption zone to absorb sulfur dioxide
Implementation Method 3
stripping, preferably steam stripping, absorbed sulfur dioxide from at least a part of the spent absorbing medium obtained in step (ii) in a regeneration zone
Data Source
AI summary
The invention is directed to a process and a system for removing sulfur dioxide from a feed gas stream. In the process the feed gas pre-scrubbed. Then SO2 is absorbed from the gas with an absorbing medium. The spent absorbing medium is regenerated. These process steps are interchanged with a caustic treatment in the pre-scrubbing zone in case of a very high SO2 content in the feed gas stream. The system comprises a pre-scrubbing unit, an absorption unit, and a regeneration unit. The system is characterized in that the pre-scrubber unit comprises an inlet for an aqueous solution comprising a strong base. These are a simple, cost-efficient and reliable process and facility for processing gas with a varying SO2 content.