Catalytic Steam Reformer Recycle Loop for Turndown Steam
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Solution Overview
Problem
Hydrogen production facilities face challenges in maintaining steam production during turndown conditions, where hydrogen production rates decrease, leading to insufficient export steam due to reduced heat and steam effluent in catalytic steam reformers.
Innovation Solution
A method involving the formation of a reformer feed gas mixture from a steam-containing gas, a sulfur-depleted reformer feedstock, and a separate steam-containing recycle gas mixture, which is introduced into catalytic steam reformer tubes, with external fuel combustion to supply energy, and the subsequent recycling of steam from the boiler effluent to enhance steam production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If hydrogen production rate is decreased during turndown conditions, then hydrogen production flexibility is improved, but steam production decreases due to reduced heat and steam effluent
Solution Approach 1:
The invention introduces a feedback mechanism by recycling a portion of the reformer effluent back to the reformer inlet. This recycled stream containsæªreacted hydrocarbons and steam, which are reused as feedstock. The feedback loop ensures that even at reduced hydrogen production rates, sufficient steam is maintained in the system through continuous recycling, resolving the contradiction between production flexibility and steam availability
Solution Approach 2:
Instead of discarding the reformer effluent completely or using it only for its primary purpose (hydrogen production), the invention recovers valuable components from the effluent stream. Specifically, unreacted hydrocarbons and steam are separated and recycled back to the reformer, maximizing resource utilization and maintaining steam production levels regardless of hydrogen production rate
2Device complexity
If steam production is coupled directly to hydrogen production rate, then process simplicity is improved, but ability to meet export steam demand during turndown deteriorates
Solution Approach 1:
The invention segments the reformer effluent stream into different pathways: one portion continues to the usual downstream processing for hydrogen production, while another portion is diverted and recycled back to the reformer inlet. This segmentation allows independent control of steam production from hydrogen production, enabling the system to meet export steam demands even during turndown conditions without significantly increasing overall process complexity
3Adaptability or versatility
If reformer operates at reduced capacity during turndown, then hydrogen production adaptability is improved, but heat transfer efficiency decreases leading to potential overheating risks
Solution Approach 1:
The recycling of reformer effluent back to the reformer inlet ensures continuous introduction of steam and unreacted hydrocarbons into the reformer tubes. This continuous action maintains adequate heat transfer and prevents localized overheating or coking that could occur during turndown conditions, allowing the reformer to operate adaptively at reduced capacity while maintaining temperature control
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 method allows for efficient steam production at various hydrogen production rates, including during turndown conditions, by maintaining heat transfer and reducing energy consumption, thus ensuring steam demand is met while minimizing overheating risks in the reformer tubes.
Implementation Method 1
The reformer feed gas mixture is introduced into a catalytic steam reformer to form a reformed gas mixture
Implementation Method 2
In the catalytic steam reformer, hydrocarbon is reformed by steam over a reforming catalyst to form a reformed gas mixture
Implementation Method 3
Fuel and oxidant, typically air, is introduced through burners generating heat energy that is transferred to the reformer tubes by radiation and convection
Implementation Method 4
A large portion of the heat contained in this reformed gas mixture is recovered in a heat exchanger, referred to as a waste heat boiler to produce steam
Implementation Method 5
The separate steam-containing recycle gas mixture may be formed by cooling a first portion of the boiler effluent and compressing the cooled first portion
Data Source
Figure 1
AI summary
A method for generating hydrogen in a production facility having a catalytic steam reformer, a boiler downstream of the catalytic steam reformer, optionally having a prereformer, and optionally having a shift reactor, wherein the reformer feed gas mixture is formed using a steam-containing recycle gas mixture which was formed from boiler effluent. The boiler generates steam which may be used to form the reformer feed gas mixture, used elsewhere in the production facility, and/or used for export steam.