Series-Connected Bulk Methanators for SNG Production
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Solution Overview
Problem
Current SNG production processes face limitations in capacity due to the need for parallel reactors and ancillary equipment, especially in large-scale plants, as they require higher product gas recycle and impose constraints on vessel size and layout.
Innovation Solution
The process involves feeding a synthesis gas in parallel to multiple bulk methanators, with all methanated gas streams from previous reactors used to dilute feed gas to subsequent reactors, and a portion recirculated to the first reactor, allowing for higher capacities without the need for parallel reactors and ancillary equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a single bulk methanator is used with high product gas recycle to control temperature, then temperature control is improved, but device complexity and equipment size increase
Solution Approach 1:
The bulk methanation process is divided into multiple series-connected reactors (first bulk methanator, second bulk methanator, and subsequent bulk methanators) instead of using a single large reactor with high recycle. This segmentation allows each reactor to operate at lower individual temperatures with reduced recycle requirements, while achieving the same overall conversion and temperature control through the series arrangement.
2Productivity
If parallel reactors are used to increase capacity, then productivity is improved, but device complexity and layout constraints increase
Solution Approach 1:
Instead of increasing capacity through parallel reactors (horizontal dimension), the invention uses series-connected bulk methanators with optimized gas distribution (vertical/process dimension). The feed gas is distributed to multiple bulk methanators in parallel, but the key innovation is using methanated gas streams from previous reactors to dilute feed gas to subsequent reactors, creating a series-like effect that increases capacity without the complexity of full parallelization.
3Speed
If high product gas recycle is used to control reaction rate, then reaction rate control is improved, but power consumption increases
Solution Approach 1:
Instead of using high recycle ratios to control reaction rate, the invention uses partial action by distributing feed gas to multiple bulk methanators and using methanated gas streams from previous reactors for dilution. This partial dilution approach achieves reaction rate control with significantly lower recycle requirements, reducing the energy consumption of recycle compressors while maintaining proper reaction kinetics.
4Productivity
If vessel size is increased to handle larger capacities, then productivity is improved, but manufacturing and transportation constraints increase
Solution Approach 1:
The invention divides the bulk methanation function across multiple smaller reactors instead of using one or two very large vessels. This segmentation into series-connected bulk methanators creates vessels of manageable size that can be manufactured and transported more easily, while the series arrangement and gas distribution system maintain the required overall capacity and conversion efficiency.
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 reduces recycle gas flow and power consumption, simplifies plant layout, and enables smaller equipment sizes, achieving higher capacities and more efficient operation.
Implementation Method 1
each bulk methanator containing a methanation catalyst such that the feed gas is at least partially methanated to form a methanated gas stream
Implementation Method 2
The methanation of the syngas involves the following, highly exothermic reactions: CO + 3H2 → CH4 + H2O ΔH = minus 206 kJ/mol; CO2 + 4H2 → CH4 + 2H2O ΔH = minus 165 kJ/mol
Implementation Method 3
the feed gas to the second and each of the one or more subsequent bulk methanators is diluted with a methanated gas stream recovered from the previous bulk methanator
Implementation Method 4
a portion of the methanated gas stream recovered from the second or one or more subsequent bulk methanators is recirculated in a recirculation loop to the first bulk methanator
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
A process is described for producing a substitute natural gas comprising the steps of: feeding a feed gas comprising hydrogen, carbon monoxide and/or carbon dioxide in parallel to a first bulk methanator, a second bulk methanator and one or more subsequent bulk methanators, each bulk methanator containing a methanation catalyst such that the feed gas is at least partially methanated to form a methanated gas stream, wherein the first, second and at least one subsequent methanators are connected in series so that the feed gas to the second and each of the one or more subsequent bulk methanators is diluted with a methanated gas stream recovered from the previous bulk methanator, wherein all of the methanated gas stream recovered from the first bulk methanator is used to dilute the feed gas to the second bulk methanator, a portion of the methanated gas stream recovered from the second or one or more subsequent bulk methanators is recirculated in a recirculation loop to the first bulk methanator and used to dilute the feed gas fed to said first bulk methanator, and wherein at least one bulk methanator is located outside the recirculation loop.