Ammonium Thiosulfate Production via pH-Controlled Absorption
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Solution Overview
Problem
Existing methods for producing ammonium thiosulfate face inefficiencies in absorption efficiency due to indirect pH control and limited production volume, leading to high costs and environmental emissions, and require multiple absorption circuits.
Innovation Solution
A continuous process using ammonium bisulphite and diammonium sulphite as primary absorbing agents, with external ammonia to maintain a stable pH, allowing high absorption efficiency of sulfur dioxide, and a simplified system with reduced reaction towers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If indirect pH control is used by controlling the amount of sulfur dioxide or ammonia in gas streams, then the process is simpler to operate, but the absorption efficiency for SO2 is reduced
Solution Approach 1:
The patent changes the control parameter from indirect pH control (via gas stream composition) to direct pH control (via caustic soda addition). This allows precise adjustment of pH to maintain optimal absorption efficiency while keeping the system easy to operate through automated pH monitoring and chemical dosing.
Solution Approach 2:
The patent implements a feedback control system where pH is continuously monitored in the absorption solution and caustic soda is automatically dosed to maintain the desired pH range. This closed-loop control ensures both high absorption efficiency and ease of operation through automated adjustment.
2Productivity
If multiple absorption circuits are used to produce highly concentrated sulphite solution, then the absorption efficiency is improved, but the device complexity increases
Solution Approach 1:
The patent merges the functions of multiple absorption circuits into a single absorption tower where both H2S and SO2 are absorbed simultaneously in one unit. This consolidation maintains high absorption efficiency while significantly reducing device complexity by eliminating the need for separate absorption circuits and interconnecting equipment.
Solution Approach 2:
The single absorption tower is designed to perform multiple functions: absorbing H2S from the gas stream, absorbing SO2 (either from the same stream or externally), and maintaining optimal pH through caustic soda dosing. This multi-functional design replaces the need for multiple specialized circuits.
3Ease of manufacture
If the production volume of ATS is limited by the amount of NH3 in the SWSG, then the process uses only internal materials, but the productivity is reduced
Solution Approach 1:
The patent introduces caustic soda (NaOH) as an intermediary material to enable external ammonia supplementation. The caustic soda allows additional ammonia to be added to the system while maintaining pH control, thus breaking the limitation of internal ammonia availability and enabling increased ATS production volume.
Solution Approach 2:
The patent creates a dynamic system where ammonia can be flexibly supplemented from external sources based on production requirements, rather than being statically limited by internal SWSG ammonia content. The pH-controlled dosing system dynamically adjusts to accommodate variable ammonia inputs while maintaining optimal operating conditions.
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
Achieves high efficiency in converting hydrogen sulfide and ammonia into ammonium thiosulfate, reducing harmful emissions, and optimizing production volume while being cost-effective and adaptable to varying feedstock compositions.
Implementation Method 1
contacting in a second reactor the second flue gas stream of step c) with said third aqueous effluent solution to produce a fourth aqueous effluent solution comprising ammonium bisulphite and diammonium sulphite
Implementation Method 2
combusting in a furnace the first flue gas stream of step a) and a second gas stream comprising hydrogen sulfide to produce a second flue gas stream comprising SO2 with N2 and NOx
Implementation Method 3
contacting in a second reactor the second flue gas stream of step c) with said third aqueous effluent solution to produce a fourth aqueous effluent solution comprising ammonium bisulphite and diammonium sulphite
Data Source
Figure 1
AI summary
The present invention relates to a method for producing ammonium thiosulfate by contacting a gas stream comprising hydrogen sulphide and ammonia with an aqueous solution comprising ammonium bisulphite and diammonium sulphite.