Low-Alkali Sorbent Composition for Coal Combustion Emission Control
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Solution Overview
Problem
Coal combustion releases significant amounts of mercury, nitrogen oxides, and sulfur oxides into the atmosphere, leading to environmental hazards and health issues, and existing technologies face challenges in effectively capturing these pollutants without compromising heating efficiency or causing furnace fouling.
Innovation Solution
The use of sorbents with low alkali content, specifically containing bromine compounds, calcium, silica, and alumina, is introduced into the coal combustion process to reduce emissions of mercury, nitrogen oxides, and sulfur oxides, while minimizing furnace fouling by controlling the levels of sodium and potassium, thereby preventing the formation of deposits on boiler surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If traditional sorbents with high alkali content are used to capture mercury and reduce emissions, then pollutant capture efficiency is improved, but furnace fouling increases due to deposit formation on boiler surfaces
Solution Approach 1:
The patent changes the chemical composition parameters of the sorbent by strictly limiting alkali metal oxides (Na2O < 1%, K2O < 1%) and chlorine content (< 0.1%), while optimizing calcium oxide (40-70%), silica (10-30%), and alumina (5-20%) content. This parameter modification allows the sorbent to capture mercury effectively without generating excessive fouling deposits in the furnace.
Solution Approach 2:
The patent uses a composite sorbent material combining multiple components: calcium-containing compounds (CaO, CaCO3, Ca(OH)2), silica compounds (SiO2, silicones), alumina compounds (Al2O3, aluminum salts), and optional halogen compounds (bromine, iodine). This composite structure provides synergistic effects for pollutant capture while controlling fouling through balanced composition.
2Object-affected harmful factors
If sorbents are added to capture nitrogen oxides and sulfur oxides, then environmental compliance is improved, but heating efficiency decreases due to furnace fouling
Solution Approach 1:
The patent modifies sorbent composition parameters to limit alkali content (Na2O + K2O < 2% total) and chlorine (< 0.1%), which are the primary contributors to fouling. By controlling these parameters while maintaining adequate calcium oxide (40-70%) for SOx capture and nitrogen oxides reduction, the sorbent achieves emission compliance without significant heating efficiency loss.
3Object-affected harmful factors
If low sulfur coal is used to reduce sulfur emissions, then environmental impact is improved, but heating value decreases leading to lower energy output
Solution Approach 1:
The patent introduces an intermediary substance (sorbent composition) that mediates between the low sulfur coal and the combustion process. The sorbent contains calcium compounds that actively capture sulfur during combustion, enabling the use of low sulfur coal (inherently lower heating value) while maintaining effective sulfur emission control through chemical intervention rather than relying solely on fuel selection.
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 effectively captures mercury and other pollutants, reducing their release into the atmosphere, minimizing furnace fouling, and enhancing the cementitious properties of the ash produced, making it suitable for use in cement and concrete products, while complying with environmental regulations and potentially qualifying for tax benefits.
Implementation Method 1
The invention provides compositions and methods for reducing the levels of mercury, nitrogen oxides, and/or sulfur oxides emitted into the atmosphere upon burning of mercury-containing fuels such as coal. In particular, the invention provides for addition of various halogen and other sorbent compositions into the coal burning system during combustion.
Implementation Method 2
The sorbents can be used to prepare a refined coal that can be burned to reduce emissions of one or more of mercury, nitrogen (as NOx), and sulfur (as SOx). The liquid sorbent contains a bromine compound
Implementation Method 3
A method of making the refined coal involves combining a sub-bituminous coal (or a lignite coal) and sorbent components.
Implementation Method 4
The invention provides compositions and methods for reducing the levels of mercury, nitrogen oxides, and/or sulfur oxides emitted into the atmosphere upon burning of mercury-containing fuels such as coal.
Data Source
AI summary
Powder components containing calcium, alumina, silica, iron, magnesium, and a halogen sorbent are used in combination during coal combustion to produce environmental benefits. Sorbents are added to the coal ahead of combustion and/or are added into the flame or downstream of the flame. The alkalinity and chlorine of the powder is minimized in order to mitigate unwanted fouling, especially when used with sub-bituminous and lignite coals.