Biogas Water Wash Absorption Risers for Methane Recovery
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing biogas separation systems, particularly water wash processes, are cumbersome and costly due to the need for large, corrosion-resistant vessels and substantial physical foundations, which are inefficient in separating methane from carbon dioxide effectively.
Innovation Solution
The system employs multiple absorption risers installed below grade, with biogas and water streams interacting in a counter-current flow to enhance carbon dioxide absorption, allowing for series or parallel connections and the use of dispersion elements and packing materials to increase contact area, thereby improving methane recovery and reducing system size and material costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional water wash process uses tall vessels with water pumped into the top and biogas pumped into the bottom, then sufficient contact time is provided for carbon dioxide absorption, but the vessel height becomes substantial requiring substantial physical foundation and resulting in significant capital expenditures
Solution Approach 1:
The patent divides the single tall absorption vessel into multiple shorter absorption columns arranged vertically. Each column is a separate unit with its own inlet and outlet, allowing the biogas to flow through multiple stages of absorption. This segmentation reduces the height requirement of each individual vessel while maintaining sufficient contact time through multi-stage processing.
Solution Approach 2:
The patent transitions from a single vertical dimension (one tall vessel) to a multi-dimensional arrangement (multiple columns stacked vertically with interconnections). The biogas flows through a series of columns in sequence, utilizing both vertical stacking and horizontal arrangement to achieve the required absorption capacity without excessive height of any single vessel.
2Reliability
If vessels are constructed of stainless steel to be corrosion resistant due to hydrogen sulfide presence and carbonic acid formation, then corrosion resistance is achieved, but the material cost and capital expenditure increase substantially
Solution Approach 1:
The patent applies corrosion protection locally rather than throughout the entire vessel. A corrosion-resistant coating or lining is applied only to the interior surfaces that contact the biogas and wash water, while the exterior and non-contact portions can use less expensive materials. This localized approach provides necessary corrosion resistance where needed while reducing overall material costs.
Solution Approach 2:
The patent employs composite construction where the vessel body may be made of less expensive materials (such as carbon steel or concrete) combined with a corrosion-resistant lining or coating layer. This composite approach combines the structural strength and cost-effectiveness of cheaper materials with the corrosion protection of expensive materials only where required for contact with corrosive substances.
3Reliability
If the vessel is made large to accommodate substantial water volume for absorption, then sufficient absorption capacity is achieved, but the weight increases substantially requiring substantial physical foundation
Solution Approach 1:
The patent divides the total water volume requirement into multiple smaller units distributed across several absorption columns. Each column contains a portion of the total water volume needed for absorption, reducing the weight of water in any single vessel. The cumulative absorption capacity across all columns maintains the required performance while distributing the weight burden.
Solution Approach 2:
The patent implements a recirculation system where wash water is continuously pumped from the bottom of each column back to the top for reuse. This dynamic recirculation allows a smaller total volume of water to achieve the same absorption capacity that would require a much larger static water volume, thereby reducing the weight of water and the vessel structure.
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 configuration enhances the efficiency of methane recovery from biogas, reduces capital expenditures, and allows for easier maintenance and installation, while maintaining high purity of the methane output.
Implementation Method 1
carbon dioxide and hydrogen sulfide are many times more soluble in water than methane. As the biogas rises through the water, the carbon dioxide, hydrogen sulfide, and other water soluble trace constituents are absorbed into the water.
Data Source
AI summary
Multiple risers are provided to perform different steps in a biogas water wash process. The risers may include absorption risers, flashing risers, and stripping risers. In each riser, the inlets to provide fluids to the riser and outlets to remove fluids from the risers are provided at one end of the riser. Each riser may then be located substantially below grade such that the end with the inlets and outlets is accessible at or just above the ground level. The risers within each step of the water wash process may be connected in series, parallel, or a combination thereof. The risers may also be constructed of a polyethylene material to reduce cost and weight of the water wash system.