Hydrogen Production Process Using Quench and Water Gas Shift
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Solution Overview
Problem
Existing processes for producing hydrogen-rich gas from solid sulphur- and halogen-containing carbonaceous feedstocks require significant amounts of steam and complex process setups, making them inefficient.
Innovation Solution
A process involving gasification of the carbonaceous feedstock in an entrained flow gasifier, followed by quenching, counter-current water contact, and catalytic water gas shift reaction with reduced steam content, simplifies the process and reduces steam requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If significant amounts of steam are added to the feed of the water shift conversion reaction to increase H2/CO ratio, then the hydrogen production is improved, but the process complexity increases due to dedicated boilers and complex process line-up
Solution Approach 1:
The patent combines the steam generation function with the existing gasification process by using the gasifier to produce both synthesis gas and steam. The gasification reaction inherently produces steam when water is used as the gasifying agent, eliminating the need for separate steam boilers and complex steam preparation systems while maintaining high hydrogen production through subsequent water-gas shift conversion.
Solution Approach 2:
The gasifier is designed to perform multiple functions simultaneously: it gasifies the carbonaceous feedstock to produce synthesis gas (CO and H2), generates the required steam for the water-gas shift reaction, and provides the thermal energy needed for the overall process. This multi-functionality reduces process complexity while maintaining productivity.
2Productivity
If steam to carbon monoxide molar ratio is increased to 2.8:1 as in prior art to achieve adequate hydrogen production, then the water gas shift reaction efficiency is improved, but the steam requirement and process complexity increase
Solution Approach 1:
The patent optimizes the steam to carbon monoxide molar ratio to a specific range (0.7:1 to 1.3:1) that achieves adequate water-gas shift conversion efficiency without requiring excessive steam. This parameter optimization allows the process to produce sufficient hydrogen while using less steam, thereby reducing the burden on steam generation equipment and simplifying the overall process.
3Temperature
If the gas mixture is cooled to below 900°C by quenching before water contact, then the temperature control for subsequent reactions is improved, but the process steps and equipment complexity increase
Solution Approach 1:
The patent performs quenching as a preliminary cooling step before the counter-current water contactor to reduce the gas temperature to below 900°C. This preliminary action prepares the gas for the subsequent water-gas shift reaction by bringing it to an appropriate temperature range, ensuring optimal reaction conditions while maintaining a streamlined process flow.
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 process efficiently produces hydrogen-rich gas with lower steam addition and simplifies the process line-up, achieving high hydrogen production with controlled steam and carbon monoxide conversion.
Implementation Method 1
gasification of the solid carbonaceous feedstock in an entrained flow gasifier
Implementation Method 2
contacting the gas mixture with a quench gas or quench liquid to reduce the temperature of the gas mixture to below 900° C.
Implementation Method 3
contacting the gas mixture obtained in step (b) with water in a counter-current contactor having a top end and a bottom end, wherein water having a temperature of between 150 and 250° C. is continuously fed to the top of the contactor and the gas mixture to the bottom end
Implementation Method 4
subjecting the gas mixture obtained in step (c) to a water gas shift reaction wherein part or all of the carbon monoxide is converted with the steam to hydrogen and carbon dioxide in the presence of a catalyst
Implementation Method 5
carbon dioxide and sulphur compounds are separated from the shifted gas mixture obtained in step (d) by contacting the shifted gas mixture with a solvent comprising dialkylethers of polyethylene glycol
Data Source
AI summary
The invention is directed to a process to prepare a hydrogen rich gas mixture from a solid sulphur- and halogen-containing carbonaceous feedstock. The process involves the following steps. Step (a): gasification of the solid carbonaceous feedstock with an oxygen-containing gas to obtain a gas mixture comprising halogen compounds, sulphur compounds, hydrogen and at least 50 vol. % carbon monoxide, on a dry basis. Step (b): contacting the gas mixture with a quench gas or quench liquid to reduce the temperature of the gas mixture to below 900° C. Step (c) contacting the gas mixture with water having a temperature of between 150 and 250° C. to obtain a gas mixture comprising between 50 and 1000 ppm halogen and having a steam to carbon monoxide molar ratio of between 0.2:1 and 0.9:1. Step (d): subjecting the gas mixture obtained in step (c) to a water gas shift reaction wherein part or all of the carbon monoxide is converted with the steam to hydrogen and carbon dioxide in the presence of a catalyst as present in one fixed bed reactor or in a series of more than one fixed bed reactors and wherein the temperature of the gas mixture as it enters the reactor or reactors is between 190 and 230° C. Step (e): carbon dioxide and sulphur compounds are separated from the shifted gas mixture obtained in step (d) by contacting the shifted gas mixture with a solvent comprising dialkyl ethers of polyethylene glycol.