Calcium Looping Hydrogen Production via CaO Sorbent
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Solution Overview
Problem
Current hydrogen production methods face challenges in achieving high purity hydrogen with efficient CO2 management and sulfur removal, often requiring excessive steam and catalysts, which increase costs and energy consumption.
Innovation Solution
The integration of a calcium looping process that uses a high reactivity mesoporous calcium oxide sorbent to simultaneously remove CO2, sulfur, and halides in a single-stage reactor, eliminating the need for a water gas shift catalyst and reducing steam requirements, while regenerating calcium oxide for continuous operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional hydrogen production methods are used with catalysts and excess steam, then hydrogen production rate is improved, but steam consumption and energy cost increase
Solution Approach 1:
The patent removes the water-gas shift catalyst from the system and extracts only the essential function of CO2 removal through calcium oxide carbonation. This eliminates the need for excess steam that would otherwise be required to drive catalytic water-gas shift reactions, while maintaining hydrogen production through direct carbonation of CO2 by CaO.
Solution Approach 2:
The patent introduces calcium oxide (CaO) as an intermediary substance that mediates the removal of CO2 through carbonation reactions. This intermediary enables the system to achieve CO2 separation and hydrogen production without relying on catalytic water-gas shift reactions that consume excessive steam, thus resolving the contradiction between productivity and energy use.
2Measurement precision
If multiple separate units are used for CO2 removal, sulfur removal, and hydrogen production, then purification precision is improved, but device complexity increases
Solution Approach 1:
The patent merges CO2 removal, sulfur removal, and hydrogen production functions into a single integrated reactor stage. Calcium oxide simultaneously performs carbonation to remove CO2 and sulfidation to remove sulfur, while the water-gas shift reaction produces hydrogen. This consolidation achieves high hydrogen purity without requiring multiple separate reactor units, thus reducing device complexity while maintaining purification precision.
Solution Approach 2:
The patent makes calcium oxide a multi-functional material that simultaneously removes CO2 through carbonation, removes sulfur through sulfidation, and enables hydrogen production through water-gas shift reaction promotion. This universal approach allows a single substance to perform multiple purification and production functions, eliminating the need for multiple specialized units and reducing overall system complexity.
3Productivity
If calcium oxide is regenerated by calcination in air, then regeneration efficiency is improved, but CO2 emissions increase
Solution Approach 1:
The patent converts the harmful CO2 emissions from traditional air calcination into a beneficial resource by capturing and utilizing CO2 from the hydrogen production process itself. The CO2 that would normally be emitted is instead fed to the calcium looping system where it is captured by CaO, and the heat from calcining CaCO3 provides the energy needed for the process. This transforms a waste product into a useful input, eliminating net CO2 emissions while maintaining regeneration efficiency.
Solution Approach 2:
The patent recovers CO2 that would otherwise be discarded during calcination by using it as a feedstock for the calcium carbonation process. The system captures CO2 from the syngas stream and uses it to regenerate CaO, creating a closed loop where CO2 emissions are minimized. This recovery approach converts a harmful emission into a valuable resource that sustains the calcium looping process.
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 enhances hydrogen yield and purity, reduces steam consumption, and integrates CO2 capture and sulfur removal, leading to a more efficient and cost-effective hydrogen production process with flexible H2:CO ratios, suitable for various applications including coal to liquid technologies.
Implementation Method 1
allowing said shifted gas to react with said CaO in said WGSR so as to remove CO2, sulfur and halides in a solid-phase calcium-containing product comprising CaCO3, CaS and CaX2
Implementation Method 2
J Abbasian et al discloses the effect of HCL on sulfidation of calcium oxide (Chemical Engineering Science, vol. 48, no. 15, pages 2689 - 2695)
Implementation Method 3
separating the solid-phase calcium-containing product from an enriched gaseous hydrogen product
Implementation Method 4
regenerating the CaO by calcining the solid-phase calcium-containing product at a condition selected from the group consisting of: in the presence of steam, in the presence of CO2, in the presence of synthesis gas, in the presence of H2 and O2, under partial vacuum, and combinations thereof
Data Source
Figure 1
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Figure 3~4
AI summary
A process for producing hydrogen, comprising the steps of: (a) gasifying a fuel into a raw synthesis gas comprising CO, hydrogen, steam and sulfur and halide contaminants in the form of H2S, COS and HX, where X is a halide; (b) passing the raw synthesis gas through a water gas shift reactor (WGSR) into which CaO and steam are injected, the CaO reacting with the shifted gas to remove CO2, sulfur and halides in a solid-phase calcium-containing product comprising CaCO3, CaS and CaX2; (c) separating the solid-phase calcium-containing product from an enriched gaseous hydrogen product; and (d) regenerating the CaO by calcining the solid-phase calcium-containing product at a condition selected from the group consisting of: in the presence of steam, in the presence of CO2, in the presence of synthesis gas, in the presence of H2 and O2, under partial vacuum, and combinations thereof. The CaO may have a surface area of at least 12.0 m2/g and a pore volume of at least 0.015 cm3/g, the CaO having a sorption capacity of at least about 70 grams of C02 per kilogram of CaO.