Countercurrent FGD Gypsum Conversion Process
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Solution Overview
Problem
Existing processes for converting FGD gypsum to ammonium sulfate and calcium carbonate face challenges due to the varying reactivity of FGD gypsum particles, resulting in low yields and impurities, and fail to achieve high purity and efficiency.
Innovation Solution
A multistage countercurrent continuous process is developed, involving multiple reactors with internal recycle of liquids, using ammonium carbonate to react with FGD gypsum, which allows for high yield and purity of ammonium sulfate and calcium carbonate production, even with less reactive gypsum particles, and includes contaminant removal processes to ensure product quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If FGD gypsum with less reactive crystalline particles (thicker and more spherical) is used as starting material, then the process must accommodate lower reactivity, but this results in lower reaction efficiency and difficulty in achieving high purity products
Solution Approach 1:
The single reactor is divided into multiple reactors arranged in series (typically 3-5 reactors). This segmentation allows the reaction process to occur in stages, with each reactor contributing to the overall conversion. The multistage approach enables better accommodation of less reactive FGD gypsum particles by providing extended reaction time and multiple opportunities for complete conversion, thereby maintaining high productivity despite varied gypsum reactivity.
Solution Approach 2:
The process employs preliminary classification and preparation of FGD gypsum particles before they enter the reaction system. This includes size classification and pre-treatment to optimize particle characteristics for the reaction process. By preparing the gypsum particles in advance, the system can better handle variations in crystalline structure and reactivity, ensuring consistent high-purity product output across different FGD gypsum sources.
2Device complexity
If conventional single-stage processes are used to convert FGD gypsum to ammonium sulfate and calcium carbonate, then the process is simpler, but the yields are low and product purity is compromised
Solution Approach 1:
The conversion process is segmented into multiple reaction stages using a series of reactors. Each reactor performs a specific function in the conversion sequence, allowing for progressive transformation of FGD gypsum to ammonium sulfate and calcium carbonate. This multistage approach significantly improves product purity and yield compared to single-stage processes, while the modular nature of the segmentation keeps operational complexity manageable.
Solution Approach 2:
The process introduces intermediate treatment stages between the reaction stages, including filtration and purification steps. These intermediary processes remove impurities and separate products at appropriate points in the reaction sequence, ensuring high purity final products. The intermediaries act as mediators that bridge the reaction stages and product separation, maintaining both high purity and reasonable process complexity.
3Adaptability or versatility
If FGD gypsum is produced at different power plants with varying crystalline structures, then more sources become accessible, but the reactivity varies making consistent high purity production difficult
Solution Approach 1:
The multistage reactor system provides consistent high-purity production across different FGD gypsum sources by dividing the conversion process into multiple controlled stages. Each reactor stage is optimized to handle variations in input material characteristics, ensuring that regardless of the power plant source or crystalline structure, the final products meet consistent purity specifications.
Solution Approach 2:
The process employs adjustable operational parameters at each reactor stage to accommodate variations in FGD gypsum characteristics from different power plants. By modifying parameters such as residence time, temperature, and reagent addition rates in each stage, the system maintains consistent product purity across diverse input materials while preserving the ability to process gypsum from various sources.
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 process achieves high yields (up to 100%) and high purity of ammonium sulfate and calcium carbonate, efficiently handling less reactive FGD gypsum particles and ensuring product quality by removing contaminants, thus overcoming previous technological limitations.
Implementation Method 1
The process of the present invention employs a chemical reaction of FGD gypsum with ammonium carbonate ((NH4)2CO3) to produce ammonium sulfate ((NH4)2SO4) and calcium carbonate (CaCO3)
Implementation Method 2
Both the ammonium sulfate and calcium carbonate products are commercially valuable materials and are produced by the present process in high purity and high yield
Data Source
AI summary
A continuous countercurrent flow process for converting FGD gypsum to ammonium sulfate and calcium carbonate including countercurrent flows with internal recycle of liquids to maximize the purity of reaction products while minimizing reaction times, and further include embodiments of the process that provide a yield of both ammonium sulfate and calcium carbonate to be 97 to 100%, and embodiments that provide for processes having a total time of reaction being 8 to 12 minutes, the invention further including processes for removing contaminants from the FGD gypsum employing an acid rinse process and/or a slurry tank reactor process.