Ammonia Dosing Control for Desulfurization With Low Ammonia Slip
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Solution Overview
Problem
Existing ammonia-based desulfurization processes face challenges such as ammonia slip and aerosol formation, and there is a need for an automatic ammonia-adding system with stable and reliable operation, high automation, and simple process control to achieve efficient sulfur oxide removal.
Innovation Solution
An automatic ammonia-adding system that calculates a theoretical ammonia amount based on gas flow and SO2 concentration, applies correction coefficients, and uses multipoint ammonia addition with feedback control to maintain desired SO2 levels, utilizing a Distributed Control System (DCS) for precise ammonia flow rate adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If ammonia-based desulfurization process is used, then environmental friendliness and economy are improved, but ammonia slip and aerosol formation occur
Solution Approach 1:
The absorption tower is divided into multiple sections (oxidation section, crystallization section, cooling absorption section, main absorption section, and dehydration-demisting section), with ammonia added at multiple points throughout the process. This segmentation allows for controlled ammonia distribution and reaction stages, reducing ammonia slip and aerosol formation while maintaining desulfurization efficiency
Solution Approach 2:
Ammonia is added in advance at multiple points before the final gas discharge, allowing sufficient time for the ammonia to react completely with sulfur dioxide and for ammonium sulfate crystals to form and settle. This preliminary action prevents ammonia from reaching the outlet unreacted, eliminating ammonia slip
2Device complexity
If manual ammonia addition control is used, then system simplicity is maintained, but automation degree and control precision are insufficient
Solution Approach 1:
The system incorporates automatic control with feedback mechanisms that monitor desulfurization process parameters and adjust ammonia addition rates accordingly. This feedback control enables precise ammonia dosing while maintaining process simplicity through automated decision-making algorithms
Solution Approach 2:
The control system automatically calculates the required ammonia quantity based on real-time gas flow and sulfur dioxide concentration data, then self-adjusts the ammonia injection rates without manual intervention. This self-service capability achieves high automation while keeping the operational interface simple
3Ease of operation
If ammonia addition amount is not precisely controlled, then operation simplicity is maintained, but ammonia slip increases
Solution Approach 1:
Manual mechanical ammonia addition control is replaced with an automated electronic control system that uses sensors, controllers, and actuators to precisely regulate ammonia flow. This substitution maintains ease of operation through automatic adjustment while achieving precise control to prevent ammonia slip
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
The system effectively reduces ammonia slip and aerosol formation, achieving SO2 concentrations below 35 mg/Nm3, total dust below 5 mg/Nm3, and ammonia recovery above 99%, while minimizing investment and operational costs.
Implementation Method 1
ammonia-based desulfurization process
Implementation Method 2
the added ammonia desulfurizer is converted into a useful ammonium sulfate fertilizer
Implementation Method 3
an oxidation section, a crystallization section
Implementation Method 4
a crystallization section
Data Source
Figure 1
Figure 2
AI summary
The present invention discloses an automatic ammonia-adding system for an ammonia-based desulfurization device, using multi-stage control, automatically calculating a theoretical amount of ammonia based on gas amounts provided by an inlet continuous emission monitoring system (CEMS) and an outlet CEMS of the ammonia-based desulfurization device or associated gas amounts, a SO2 concentration provided by the inlet CEMS, and a predetermined SO2 concentration of the outlet CEMS; calculating a corrected theoretical amount of ammonia using half of the ratio of the actual amount of added ammonia to the actual amount of removed sulfur dioxide as a correction coefficient for the theoretical amount of ammonia; adding an ammonia absorbent equivalent to the corrected theoretical amount of ammonia ±10% to the ammonia-based desulfurization device through an ammonia metering means and an ammonia control valve; and then automatically controlling the actual ammonia flow rate based on the actual SO2 concentration and change trend provided by the outlet CEMS as a feedback, thereby achieving automatic ammonia addition. The automatic ammonia-adding system of the present invention can achieve automatic ammonia addition to ensure that clean flue gas meets ultralow emission requirements, and is characterized by stable and reliable system operation, a high automation degree and a simple process.