Syngas Fermentation Conductivity Control via Ammonium Hydroxide
Solution Overview
Problem
Fermentation processes using anaerobic microorganisms face operational issues due to high conductivity and pH imbalances caused by ammonium chloride, leading to reduced ethanol productivity and detrimental effects on culture performance, especially at higher productivity levels.
Innovation Solution
A process is developed that introduces syngas into a reactor vessel with a nitrogen feed rate of 100 mg or more per gram of cells produced, using ammonium hydroxide as a nitrogen source, which reduces conductivity to 16 mS/cm or less and maintains a pH of 4.2 to 4.8, thereby enhancing ethanol production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If ammonium chloride is used as nitrogen source, then nitrogen feed is provided, but conductivity increases and pH imbalances occur leading to reduced ethanol productivity
Solution Approach 1:
The patent changes the chemical parameters of the nitrogen source from ammonium chloride to ammonium hydroxide, which fundamentally alters the conductivity and pH characteristics of the fermentation medium. This parameter change resolves the contradiction by providing nitrogen while avoiding the harmful high conductivity and pH imbalances associated with ammonium chloride
Solution Approach 2:
The patent employs ammonium hydroxide as a consumable nitrogen source that can be continuously fed to the reactor. This disposable chemical approach allows continuous operation without accumulating harmful effects, as the ammonium hydroxide is consumed in the fermentation process and does not persist to cause long-term conductivity issues
2Productivity
If concentrated medium is used to increase productivity, then ethanol production increases, but ionic strength increases causing detrimental effects on culture performance
Solution Approach 1:
The patent changes the chemical composition parameters of the medium by substituting ammonium chloride with ammonium hydroxide. This parameter change allows the medium to maintain lower ionic strength even at higher concentrations, thereby supporting both high ethanol production and healthy culture performance without the detrimental effects of excessive ionic strength
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 process achieves a space time yield (STY) of 10 g ethanol/(L·day) or more, with a CO conversion of 5 to 99% and cell density of 1.0 g/L or more, while reducing conductivity by at least 20% compared to ammonium chloride-based systems.
Implementation Method 1
The use of ammonium hydroxide is preferable due to cost and availability. However, because ammonium hydroxide is a base, it must be added as a separate medium stream. This addition of a high pH stream has the potential of causing fermentation operational issues. In addition, at higher productivity levels (>50 STY) during the use of a more concentrated medium, ionic strength of the fermentation broth increases to a level that causes detrimental effects on culture performance.
Implementation Method 2
Anaerobic microorganisms can produce ethanol from CO through fermentation of gaseous substrates. Fermentations using anaerobic microorganisms from the genus Clostridium produce ethanol and other useful products.
Data Source
AI summary
A process is provided for fermentation of syngas that is effective for reducing conductivity and providing an alcohol STY of about 10 g ethanol/(L·day). The process includes introducing the syngas into a reactor vessel and providing a nitrogen feed rate to the reactor vessel of about 100 mg or more nitrogen/gram of cells produced. Fermentation of the syngas is effective for providing a fermentation medium having an average conductivity of about 16 mS/cm or less and an STY of 10 g ethanol/(L·day) or more.