Methanol Synthesis Stoichiometry Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Methanol synthesis processes face inefficiencies due to carbon-rich off-gases from hydrogen recovery units, which exceed fuel demand, reducing methanol production.
Innovation Solution
A process involving the generation of synthesis gas with a stoichiometry value R between 1.70 and 1.94, using an autothermal reformer and pre-reformer in series, with steam addition to promote the water-gas shift reaction, optimizing hydrogen and carbon dioxide levels in the feed gas to the methanol synthesis unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If hydrogen is recovered from purge gas and make-up gas, then hydrogen availability for synthesis increases, but carbon-rich off-gas calorific value exceeds fuel demand
Solution Approach 1:
The invention changes the compositional parameters of the synthesis gas by controlling the stoichiometric number R to be between 1.70 and 1.94 (rather than the conventional R=2.0), and by adding water or steam to the feed gas. These parameter changes alter the reaction equilibrium and product distribution, resulting in a purge gas with higher CO2 and H2 content that, after hydrogen recovery, produces an off-gas with calibrated calorific value matching the fuel demand of the process.
2Quantity of substance
If water or steam is added to feed gas, then water-gas shift reaction is promoted increasing CO2 and H2, but process complexity increases
Solution Approach 1:
The invention uses the methanol synthesis catalyst itself to perform the water-gas shift reaction, making the catalyst serve dual functions: methanol synthesis and CO conversion to CO2. The water or steam added to the feed gas utilizes the existing catalyst activity without requiring a separate shift conversion unit, thereby promoting CO2 and H2 production while avoiding additional process complexity.
3Productivity
If stoichiometric number R is adjusted to 1.70-1.94, then methanol production increases, but synthesis gas composition control becomes more difficult
Solution Approach 1:
The invention implements composition control of the synthesis gas through feedback mechanisms that monitor and adjust the stoichiometric number R to maintain it within the 1.70-1.94 range. By continuously measuring the synthesis gas composition and adjusting operational parameters (such as water/steam addition rate and feed gas mixing ratios), the system maintains optimal conditions for enhanced methanol production while managing the complexity of composition 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 approach increases methanol production by balancing hydrogen and carbon dioxide levels, reducing carbon-rich off-gases and enhancing fuel efficiency within the process.
Implementation Method 1
passing a hydrocarbon feedstock to a synthesis gas generation unit to form a synthesis gas containing hydrogen, carbon monoxide, carbon dioxide and steam
Implementation Method 2
cooling the synthesis gas in one or more stages of heat exchange and recovering a process condensate from the cooled synthesis gas
Implementation Method 3
cooling the synthesis gas in one or more stages of heat exchange and recovering a process condensate
Implementation Method 4
the addition of water or steam to a make-up gas promotes the water gas shift reaction across the methanol synthesis catalyst resulting in a higher amount of carbon dioxide and hydrogen in the methanol converter effluent
Implementation Method 5
passing a feed gas comprising the make-up gas to a methanol synthesis unit comprising one or more methanol synthesis reactors containing a copper methanol synthesis catalyst
Data Source
AI summary
A process for synthesising methanol comprising the steps of: passing a hydrocarbon feedstock to a synthesis gas generation unit to form a synthesis gas containing hydrogen, carbon monoxide, carbon dioxide and steam; cooling the synthesis gas in one or more stages of heat exchange and recovering a process condensate from the cooled synthesis gas to form a make-up gas having a stoichiometry value R in the range of 1.70 to 1.94; passing a feed gas comprising the make-up gas to a methanol synthesis unit comprising one or more methanol synthesis reactors containing a copper methanol synthesis catalyst, and; recovering a purge gas and a crude methanol product from the methanol synthesis unit, wherein a hydrogen-rich gas is recovered from the purge gas and combined with the make-up gas, and a stream of water or steam is added to the feed gas to the methanol synthesis unit.