Flue Gas Cleaning Using Organic Absorbent for HCl Recovery
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Solution Overview
Problem
Existing methods for cleaning flue gas from chlorine-comprising materials are inefficient, producing non-reusable waste streams and requiring toxic products, and fail to meet current environmental standards due to the use of large water-based systems and neutralized solutions with high salt concentrations.
Innovation Solution
A method involving a sequence of absorption, adsorption, and further absorption steps using an absorbent that flows counter to the flue gas through packed columns with at least 90% water, followed by activated carbon filters, which effectively removes chlorine and other pollutants, resulting in a purified flue gas and a high-concentration hydrochloric acid solution suitable for reuse.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If water-based absorption systems are used to remove chlorine from flue gas, then the removal efficiency is improved, but the resulting neutralized solutions have high salt concentrations that make them non-reusable and difficult to dispose of
Solution Approach 1:
The patent changes the chemical parameters of the absorption system by replacing traditional water-based or alkaline absorbents with organic solvents having specific properties (boiling point 60-120°C, selective solubility for HCl). This parameter change enables the absorbent to be regenerated through distillation, transforming the waste stream into a reusable medium while maintaining high chlorine removal efficiency.
Solution Approach 2:
The patent implements a recovery system where the organic absorbent, after absorbing HCl from flue gas, is subjected to distillation to recover and regenerate the solvent. The recovered absorbent is then reused in the absorption process, while the concentrated HCl byproduct can be utilized or disposed of more efficiently. This closes the material loop and eliminates the need for continuous disposal of salt-containing waste solutions.
2Reliability
If large water-based absorption columns are used to meet environmental standards, then the purification effectiveness is improved, but the device complexity and space requirements increase
Solution Approach 1:
The patent changes the physical and chemical parameters of the absorbent to achieve higher purification effectiveness in a more compact system. The organic solvent's selective solubility for HCl and appropriate boiling point enable efficient absorption at lower temperatures and smaller column dimensions compared to water-based systems, while maintaining or exceeding purification effectiveness.
Solution Approach 2:
The patent implements a continuous operation system where the organic absorbent circulates between the absorption column and distillation unit. The absorbent continuously absorbs HCl from incoming flue gas, is then regenerated through distillation, and returns to the absorption column. This continuous cycle eliminates downtime for absorbent replacement or disposal, maintaining constant purification effectiveness while reducing overall system complexity compared to batch processes.
3Productivity
If traditional absorption methods are used to clean flue gas, then chlorine removal is achieved, but toxic products are required and waste streams are obtained that cannot be reused
Solution Approach 1:
The patent replaces expensive, toxic, and environmentally harmful absorbents (such as strong acids, bases, or halogenated compounds) with a simpler, less hazardous organic solvent that can be easily regenerated. The solvent's moderate boiling point and selective solubility allow for energy-efficient recovery, effectively making it a sustainable, reusable material rather than a single-use toxic chemical.
Solution Approach 2:
The patent converts the harmful HCl pollutant in flue gas into a useful concentrated HCl byproduct through selective absorption. The organic solvent acts as a transfer medium, capturing HCl from the gas stream and delivering it in concentrated form to the distillation unit, where it can be recovered as a marketable product or more easily managed waste stream, rather than dispersing it in large volumes of water-based neutralized solutions.
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 method achieves efficient removal of chlorine and other pollutants, reducing flue gas emissions to meet stringent environmental standards without using toxic products, and produces a valuable hydrochloric acid byproduct, simplifying the separation and reuse of polluted water.
Implementation Method 1
cooling and absorbing pollutants in a quench; absorbing pollutants in one or more packed columns
Implementation Method 2
adsorbing pollutants on one or more activated carbon filters
Data Source
Figure 1
Figure 2~3
AI summary
The invention relates to a method for cleaning flue gas originating from the combustion of chlorine-comprising material, in which at least the following cleaning steps are applied to the flue gas: - cooling and absorbing pollutants in a quench; - absorbing pollutants in one or more packed columns; - adsorbing pollutants on one or more activated carbon filters; - absorbing pollutants in one or more absorption columns; and - expelling cleaned flue gas thus obtained, characterized in, that an absorbent flows through the packed columns in the opposite direction of flow to the flue gas and consists of at least 90 wt% water upon entering one or more absorption columns. The invention also relates to a device for cleaning flue gas, and also relates to cleaned flue gas per se.