Reduced-headspace digester foam discharge mechanism
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Solution Overview
Problem
Existing digesters face challenges in reducing stand-off distances due to biogas explosions, primarily because of the large headspace required for foam accumulation and managing rapid volume expansion, which compromises structural integrity and safety.
Innovation Solution
A reduced-headspace digester design incorporating a gravity-operated foam discharge device and a double overflow system, where foams and floating matter are directed into a first tank and then transferred to a second tank via a conduit, allowing for continuous discharge regardless of density, thus reducing the explosive volume and overpressure thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large headspace is provided in the digester for foam accumulation and rapid volume expansion management, then structural integrity is maintained, but stand-off distance increases due to larger explosive volume
Solution Approach 1:
The invention extracts foam and floating matter from the digester headspace by directing them to an external reservoir through overflow systems. This removes the harmful foam accumulation from the confined headspace volume, reducing the explosive volume while maintaining structural integrity through controlled foam discharge
Solution Approach 2:
The invention introduces an intermediary overflow system with tanks and conduits between the digester and the external reservoir. This intermediary system manages foam transport and discharge, allowing the digester to maintain a reduced headspace while still providing a pathway for foam accumulation and rapid volume expansion management
2Object-affected harmful factors
If the headspace volume is reduced to decrease explosive volume, then stand-off distance is reduced, but the ability to manage foam accumulation and rapid volume expansion is compromised
Solution Approach 1:
The invention extends the foam management system into another dimension by creating an external reservoir system connected through overflow conduits. This allows foam to be managed outside the vertical headspace of the digester, enabling reduced headspace while maintaining foam management capability through the three-dimensional overflow discharge path
Solution Approach 2:
The overflow systems are designed to act preliminarily by continuously discharging foam and floating matter before they can accumulate to dangerous levels in the reduced headspace. The first and second overflow systems provide preliminary foam removal, preventing rapid volume expansion issues while maintaining structural integrity
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 design effectively reduces stand-off distances and maintains structural integrity by continuously removing foams and floating matter, enhancing operational safety and digester performance while managing foaming and rapid volume expansion phenomena.
Implementation Method 1
a first mixture, containing variable proportions of digestate and foaming and/or floating matter in the first tank and having a first average density, is transferred by gravity into the first zone
Implementation Method 2
the first mixture... having a first average density, is transferred by gravity into the first zone, which contains a second mixture containing variable proportions of digestate and foaming and/or floating matter and having a second density
Data Source
AI summary
The invention concerns a digester for performing a sludge methanization treatment for the purpose of generating biogas and a digestate, the digester comprising a device (32) for discharging foaming and/or floating matter (16) from the digestate (12), comprising:a first tank (33) delimited by a first wall (100) having a first height (h1), the first tank (33) being intended to be fed with digestate (12) and with foaming and/or floating matter (16) from a volume of material (14) by overflow over the first wall (100);a second tank (34) connected to the atmosphere and sited outside the enclosure (13) of the digester, comprising:a first zone (35) delimited by a second wall (103) having a second height (h2); anda second zone (36) in communication with the reservoir (19);a conduit (37) connecting the first tank (33) via a first orifice (101) to the first zone (35) of the second tank (34) via a second orifice (102) positioned higher than or level with the first orifice (101),the first zone (35) being intended to be fed with digestate (12) and with foaming and/or floating matter (16) from the first tank (33) through the conduit (37); the second zone (36) being intended to be fed with digestate from the first zone (35) by overflow over the second wall (103);the first height (h1) and the second height (h2) being predefined such that a first mixture, containing variable proportions of digestate and foaming and/or floating matter in the first tank (33) and having a first average density (d1), is transferred by gravity into the first zone (35), which contains a second mixture containing variable proportions of digestate and foaming and/or floating matter and having a second density (d2), the transfer operating such that the product of the first average density (d1) times the first height (h1) is greater than the product of the second average density (d2) times the second height (h2) times the first height (h1).