Methanol Gas Scrubbing Water Removal
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The Rectisol process for purifying raw synthesis gas using methanol absorption faces challenges due to high water content, leading to increased operating costs and capital expenditures, as well as larger system component dimensions, due to the need for additional refrigerants, steam, electrical energy, and cooling water.
Innovation Solution
A method that involves cooling the raw synthesis gas below the freezing point to separate the liquid methanol-water phase, reducing the water content in methanol circuits, and using a combination of pressure reduction and thermal separation to regenerate methanol, thereby minimizing water reintroduction into the absorption process and optimizing methanol reuse.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If methanol is added to raw synthesis gas to prevent ice formation, then ice formation is prevented, but water content in methanol circuits increases leading to higher operating costs
Solution Approach 1:
The process separates the methanol circulation system into distinct segments: an absorption section where acid gases are removed, a water separation section where water is removed from methanol, and a recycling section where purified methanol is reused. This segmentation allows water to be removed from the methanol stream before it re-enters the absorption process, preventing the water accumulation that would otherwise increase operating costs.
Solution Approach 2:
Water separation is performed as a preliminary action before the methanol is recycled back to the absorption section. By removing water from the methanol stream in advance (in the water separation section), the system prevents water from entering the absorption process, thereby avoiding the need for additional refrigerants, steam, and cooling water that would increase operating costs.
2Reliability
If water is present in the absorption column, then ice formation is prevented, but methanol demand and operating fluid requirements increase
Solution Approach 1:
The water separation section extracts water from the methanol stream using a water-gas shift converter and condensation process. By removing water from the methanol circulation system, the system reduces the total flow rates in methanol circuits, thereby decreasing the demand for methanol and operating fluids such as refrigerants, steam, and cooling water.
Solution Approach 2:
The system changes the parameter of water content in the methanol stream by using a water-gas shift converter to convert water-containing gases and then condensing the water. This parameter change (reducing water content) allows the methanol to be recycled with lower water content, reducing the overall fluid requirements and operating complexity.
3Reliability
If water content in methanol circuits is high, then ice formation is prevented, but total flow rates and steam flow rates increase requiring larger plant components
Solution Approach 1:
Water is removed from the methanol stream as a preliminary action before recycling to the absorption section. This preliminary water removal reduces the total flow rates in the methanol circuits, which in turn reduces the steam flow rates required in the hot regeneration section, allowing for smaller plant components.
Solution Approach 2:
The water content parameter in the methanol stream is changed through the water-gas shift converter and condensation process. By reducing the water content parameter, the system decreases total flow rates and steam requirements, thereby reducing the volume and dimensions of stationary plant components.
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 water content in methanol cycles, lowers operating costs, and allows for smaller system components, enhancing the efficiency and cost-effectiveness of the purification process by preventing water from entering the absorption area and minimizing the loss of valuable gases.
Implementation Method 1
separating the acid gases from the gaseous phase obtained according to step (d) by physical absorption in methanol at elevated pressure
Implementation Method 2
Cooling the methanol-added raw synthesis gas stream below the freezing point of water; Separating a liquid phase from the cooled raw synthesis gas stream
Implementation Method 3
the liquid phase obtained according to step (d) is subjected to stripping, whereby gases dissolved in the liquid phase are at least partially desorbed from the liquid phase
Implementation Method 4
the regeneration of the methanol stream laden with acid gases according to step (f) is carried out at least partially by separating water from methanol by a thermal separation process
Data Source
Figure 1
Figure 2
AI summary
The invention relates to a gas scrubbing process and a system for purifying raw synthesis gas by physical absorption in methanol. A raw synthesis gas stream, containing hydrogen and carbon monoxide as desired components and water and sour gases as undesired components, is mixed with methanol and subsequently cooled below the freezing point of water. According to the invention, a liquid phase containing methanol and water is separated from the cooled raw synthesis gas stream. Sour gases are separated from the remaining gaseous phase by physical absorption in methanol at elevated pressure. By separating the water from the raw synthesis gas stream before the absorption of the sour gases, it is prevented that large quantities of water enter the methanol cycles of the gas scrubbing process. This results in savings in operating resources, and certain system components can be dimensioned smaller than usual.