Method and device for producing low nitrogen synthesis gas from nitrogen-containing natural gas
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Solution Overview
Problem
Current methods for producing low-nitrogen synthesis gas are energetically and economically inefficient due to the need for high reflux ratios, complex cryogenic separators, and costly regeneration gas requirements, particularly for nitrogen separation and temperature swing adsorption systems.
Innovation Solution
Utilizing low-nitrogen, water- and carbon dioxide-free natural gas as regeneration gas in temperature swing adsorption systems and integrating it with thermochemical conversion to minimize external regeneration gas needs and optimize energy use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If nitrogen is separated from synthesis feed gas using a cryogenic gas separator, then nitrogen-free synthesis gas is obtained, but high reflux ratio and numerous separation stages are required due to similar boiling points of nitrogen and carbon monoxide
Solution Approach 1:
The patent applies preliminary action by separating nitrogen from natural gas before thermochemical conversion using a cryogenic gas separator. This pre-separation prevents nitrogen from entering the synthesis gas stream, eliminating the need for complex post-conversion separation. The natural gas is cooled to cryogenic temperatures where nitrogen condenses and is removed, leaving methane-rich gas for conversion.
Solution Approach 2:
The process is segmented into distinct stages: first, cryogenic separation of nitrogen from natural gas; second, thermochemical conversion of the purified natural gas; third, optional removal of carbon dioxide and water. This segmentation allows each unit to be optimized independently, avoiding the need for complex integrated separation systems.
2Reliability
If regeneration gas is supplied from external sources to temperature swing adsorption systems, then adsorbent regeneration is achieved, but additional equipment and energy costs increase
Solution Approach 1:
The patent implements self-service by using a portion of the produced synthesis gas to serve as regeneration gas for the temperature swing adsorption systems. The synthesis gas, after being cooled, provides the necessary gas flow to regenerate the adsorbents in the TSA units, eliminating the need for external regeneration gas sources and reducing overall system complexity.
Solution Approach 2:
The process recovers and reuses synthesis gas that would otherwise be discarded or required as additional input. By directing a portion of the synthesis gas to the TSA regeneration process, the system recovers valuable gas that maintains adsorbent performance without requiring external gas supplies.
3Reliability
If water and carbon dioxide are not removed before cryogenic gas separation, then they freeze and cause blockages in the separation column
Solution Approach 1:
The patent applies preliminary action by removing water and carbon dioxide from natural gas before the cryogenic separation step. This pre-treatment prevents these components from freezing and blocking the cryogenic separator. The removal is achieved through appropriate preprocessing units that condition the gas stream before it enters the low-temperature separation column.
4Manufacturing precision
If nitrogen separation is performed downstream of thermochemical conversion, then nitrogen removal from synthesis gas is achieved, but complex equipment including cryogenic separators and hydrogen purification units are required
Solution Approach 1:
The patent applies inversion by reversing the conventional approach: instead of removing nitrogen from synthesis gas after conversion, the process removes nitrogen from natural gas before conversion. This inverted sequence simplifies the overall system by preventing nitrogen from entering the conversion process, eliminating the need for complex downstream separation equipment.
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 energy expenditure and costs by leveraging methane-rich gas for regeneration, eliminating the need for additional regeneration gases and preventing blockages, while ensuring sufficient regeneration capacity and maintaining synthesis gas quality.
Implementation Method 1
water and carbon dioxide are separated in a first temperature swing adsorption plant
Implementation Method 2
nitrogen is separated in a cryogenic gas separator
Implementation Method 3
the separation column used can be operated energy-efficiently without reflux
Implementation Method 4
subjected to a thermochemical conversion in order to obtain a synthesis raw gas comprising hydrogen, carbon monoxide
Implementation Method 5
water and carbon dioxide are separated in a second temperature swing adsorption plant
Data Source
Figure 1
AI summary
Process and apparatus for producing a low-nitrogen synthesis gas (20) from a natural gas (1) containing nitrogen and carbon dioxide, from which water and carbon dioxide are removed in a first temperature swing adsorption plant (T1) and subsequently nitrogen (7) is removed in a cryogenic gas fractionator (N), to give a low-nitrogen, water-free and carbon dioxide-free natural gas (6), which is next supplied to a thermochemical conversion (K), so as to recover a crude syngas (16) comprising hydrogen, carbon monoxide, water and carbon dioxide, from which the low-nitrogen synthesis gas (20) is obtained at least by the removal of water and carbon dioxide in a second temperature swing adsorption plant (T1). The characteristic feature here is that at least a part (8) of the low-nitrogen, water-free and carbon dioxide-free natural gas (6) prior to its thermochemical conversion (K) is used as regenerating gas (9, 10) in the regeneration of the first (T1) and/or second temperature swing adsorption plant (T2).