Hydrogen Production Startup Sequence
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Solution Overview
Problem
The existing hydrogen production facilities with catalytic steam-hydrocarbon reformers and pressure swing adsorption units face challenges in quickly and efficiently starting up after maintenance, leading to increased consumption of feedstock and fuel during the startup phase.
Innovation Solution
A process that involves concurrent startup of the catalytic steam-hydrocarbon reformer and pressure swing adsorption unit, utilizing a specific sequence of purging and pressure adjustments with N2 and H2 to minimize fuel consumption and reduce startup time, including purging adsorption beds with N2 to remove oxygen and then with H2 to achieve the required hydrogen concentration and pressure for efficient operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the reformer and PSA unit are started up sequentially (reformer first, then PSA), then the startup procedure is simpler and safer, but the total startup time is longer and more fuel is consumed during the idle period
Solution Approach 1:
The PSA unit is started up in advance before the reformer begins producing hydrogen. The adsorption beds are prepared, purged with nitrogen, and placed in standby mode during which they perform adsorption cycles with inert gas or recycled streams. This preliminary preparation allows the PSA to be ready for immediate hydrogen purification when the reformer reaches operating conditions, eliminating the idle waiting period and reducing fuel consumption during startup.
2Use of energy by moving object
If the reformer and PSA unit are started up concurrently, then fuel consumption and startup time are reduced, but the coordination and control complexity increases
Solution Approach 1:
The control system continuously monitors the reformer's temperature, pressure, and hydrogen production rate, and uses this feedback to coordinate the PSA startup sequence. When the reformer reaches specific temperature thresholds or hydrogen concentration levels, the control system automatically triggers corresponding PSA operations such as switching from nitrogen purge to hydrogen feed, or transitioning from idle cycles to production cycles. This feedback-based coordination manages the complexity of concurrent operation while achieving fuel savings.
3Loss of time
If the PSA unit is purged with hydrogen before the reformer is ready, then the startup time is reduced, but the risk of introducing oxygen-hydrogen mixtures increases
Solution Approach 1:
Nitrogen is used as an intermediary gas during the transition phase. The PSA beds are first purged and prepared with nitrogen, which displaces oxygen from the system. Only after the reformer is ready and hydrogen is being produced does the system switch from nitrogen to hydrogen feed to the PSA units. This intermediary nitrogen purge eliminates oxygen-hydrogen mixture formation while minimizing the time delay, as the nitrogen preparation can occur in parallel with reformer startup.
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 significantly reduces the time and fuel consumption during startup, allowing the facility to reach operational hydrogen purity specifications faster and maintain efficient production.
Implementation Method 1
a pressure swing adsorption unit production state wherein the pressure swing adsorption unit separates a pressure swing adsorption unit feed gas formed from at least a portion of the reformate withdrawn from the plurality of catalyst-containing reformer tubes of the catalytic steam-hydrocarbon reformer undergoing the catalytic steam-hydrocarbon reformer production state to produce the H2-containing product and the by-product gas
Implementation Method 2
purging the plurality of adsorption beds with N2 to provide a N2 concentration in each of the plurality of adsorption beds greater than 96 volume % N2
Implementation Method 3
subsequently purging the plurality of adsorption beds with H2 to provide a H2 concentration in each of the plurality of adsorption beds greater than 85 volume % H2
Implementation Method 4
a fuel is combusted with an oxidant gas in the reformer furnace external to the plurality of catalyst-containing tubes
Implementation Method 5
a reformer feed gas mixture is introduced into the plurality of catalyst-containing reformer tubes, the reformer feed gas mixture is reacted in a reforming reaction under reaction conditions effective to form a reformate comprising H2, CO, CH4, and H2O
Data Source
AI summary
Process for the production of a H2-containing product in a hydrogen production facility comprising a catalytic steam-hydrocarbon reformer and a pressure swing adsorption unit. The process comprises a catalytic steam-hydrocarbon reformer shutdown mode, a pressure swing adsorption unit shutdown mode, a pressure swing adsorption unit maintenance state, a pressure swing adsorption unit startup mode, and a catalytic steam-hydrocarbon reformer startup mode. The pressure swing adsorption unit startup mode comprises purging the adsorption beds with N2, then purging the adsorption beds with H2, and then adjusting the pressure of the H2 in the adsorption beds to within defined target pressure ranges.