Direct CaO Use in Fluidized-Bed Boiler Desulphurization
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Solution Overview
Problem
Current methods for desulfurization of flue gases in fluidized-bed boilers using calcium carbonate are inefficient due to thermal stress, particle sintering, and ineffective use of calcium oxide, leading to increased energy consumption and CO2 emissions, with a significant portion of calcium oxide not participating in desulfurization and ending up in waste ash.
Innovation Solution
Producing calcium oxide with site-specific granulometry in advance, optimizing its preparation and introduction into the boiler to enhance absorption efficiency and minimize residual calcium oxide in ash, while utilizing the waste materials for higher-value derivatives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If calcium carbonate is introduced into the combustion chamber for desulphurization, then sulphur dioxide can be neutralized, but thermal stress causes particle sintering reducing reactivity and absorption capacity
Solution Approach 1:
The patent applies preliminary action by pre-calculating and pre-positioning the optimal amount and distribution of calcium carbonate sorbent in the combustion chamber before the desulphurization process begins. This ensures maximum reactivity and absorption capacity from the start, preventing sintering-related losses by having the exact required quantity already in place.
Solution Approach 2:
The patent changes the parameter of sorbent quantity and distribution dynamically. It optimizes the concentration of calcium carbonate particles in different zones of the combustion chamber, adjusting the physical-chemical parameters to maintain high reactivity while achieving effective desulphurization, thereby counteracting the sintering effect.
2Quantity of substance
If calcium carbonate undergoes thermal stress at high temperatures, then calcium oxide is produced for sulphur binding, but particle sintering reduces mechanical strength and increases elutriation
Solution Approach 1:
The patent applies local quality by creating zones with different concentrations and characteristics of calcium carbonate and calcium oxide particles within the combustion chamber. Certain regions are optimized for CaCO3 decomposition while others are optimized for CaO-SO2 reaction, maintaining particle strength in decomposition zones and maximizing reactivity in reaction zones.
Solution Approach 2:
The patent optimizes physical-chemical parameters including temperature distribution, particle size distribution, and residence time in different chamber zones. By controlling these parameters locally, it prevents excessive sintering that would reduce mechanical strength while ensuring sufficient CaO production for desulphurization.
3Productivity
If strict granulometric curves are specified for calcium carbonate preparation, then desulphurization efficiency is optimized, but processing wastes are created that are difficult to utilize
Solution Approach 1:
The patent optimizes the granulometric parameters of calcium carbonate sorbent to achieve the best balance between desulphurization efficiency and waste minimization. By adjusting particle size distribution parameters within optimal ranges rather than enforcing strict curves, it maintains high productivity while reducing processing wastes that would otherwise be difficult to utilize.
4Reliability
If calcium oxide particles are produced in the boiler, then sulphur dioxide can be absorbed, but thermal energy is consumed that could be used for steam generation
Solution Approach 1:
The patent applies preliminary action by pre-calculating the exact amount of calcium oxide needed for desulphurization and pre-positioning calcium carbonate in optimal locations. This prevents excessive CaO production and associated thermal energy consumption, ensuring that thermal energy is used efficiently for both desulphurization and steam generation.
Solution Approach 2:
The patent optimizes the chemical and physical parameters of the sorbent system to maximize sulphur absorption capacity per unit of thermal energy consumed. By adjusting parameters such as sorbent concentration, particle size, and distribution, it achieves high reliability in SO2 absorption while minimizing the thermal energy required for CaO formation and maintenance.
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 method significantly increases specific absorption capacity of SO2, reduces sorbent consumption, minimizes ash production, and optimizes thermal efficiency by ensuring all calcium oxide is available for reaction, thereby reducing CO2 emissions and improving energy management.
Implementation Method 1
CaCO3 is subjected to a temperature of approx. 850°C, and dissociates into calcium oxide (CaO) and carbon dioxide (CO2)
Implementation Method 2
The calcium oxide (CaO), obtained as described above, binds to the sulphur dioxide (SO2) that is present in the boiler flue gases, to produce the solid compound called calcium sulphate (CaSO4)
Implementation Method 3
The thermal stress causes sintering of the particles, leading to a reduction of the specific surface of the material, limiting its reactivity
Data Source
AI summary
Method for removing SO2 in the flue gases of a fluidized-bed boiler in which CaO rather than CaCO3 is used directly in the boiler. Said method permits optimization of energy and emissions to atmosphere as well as molar absorption of SO2 more than doubled compared with that observed when using CaCO3 in the boiler.