Device for on-line selective separation of organic acid from anaerobic digestion liquid

Abstract

The invention provides a device for on-line selective separation of organic acid from anaerobic digestion liquid. The device is connected with an anaerobic reactor filled with digestion liquid, and comprises a box body, a cathode and an anode arranged at two ends in the box body, and a plurality of groups of bipolar membranes and anion exchange membranes alternately stacked between the cathode and the anode, wherein the interior of the box body is divided into a plurality of compartments by the plurality of groups of bipolar membranes and anion exchange membranes, namely a cathode chamber, an anode chamber, a plurality of alkali chambers and a plurality of acid chambers, the alkali chambers and the acid chambers are arranged between the cathode chamber and the anode chamber at intervals, the alkali chambers and the anaerobic reactor are connected through pipelines to form a loop, a pipeline through which the digestive fluid in the anaerobic reactor enters the alkali chambers is provided with a micro-filter for performing micro-filtration on the digestive fluid, and a membrane contactor is embedded in each acid chamber. According to the invention, the energy consumption is greatly saved, and the stability and efficiency of anaerobic digestion are improved.

Description

technical field [0001] The invention belongs to the field of anaerobic digestion, in particular to a device for on-line selective separation of organic acids from anaerobic digestion liquid. Background technique [0002] After the implementation of garbage classification, a huge amount of biodegradable wet garbage (or called kitchen waste, perishable garbage) needs to be effectively treated and utilized as resources. The mainstream treatment method is to use anaerobic digestion technology to recover the energy in the form of methane while reducing the amount of biomass waste. However, the main problems faced by anaerobic digestion at present are: unstable methane production stage, low effective utilization rate and utilization value of methane, and inconvenient transportation and storage of methane; methanogenic archaea are extremely sensitive to changes in environmental conditions. It is very easy to cause the accumulation of organic acids, especially volatile fatty acids ...

AI Technical Summary

Problems solved by technology

However, the main problems faced by anaerobic digestion at present are: unstable methane production stage, low effective utilization rate and utilization value of methane, and inconvenient transportation and storage of methane; methanogenic archaea are extremely sensitive to changes in environmental conditions. It is very easy to cause the accumulation of organic acids, especially volatile fatty acids (Volatile Fatty Acids, VFAs), which will further inhibit the activity of methanogens. In severe cases, the reactor may fail or even need to be restarted

However, the microporous membrane separation method can only allow molecular organic acids to cross the membrane, and the pK of the above fatty acids a Both are around 4.8, the pK of lactic acid a Even as low as 3.8, so it is mostly used in batches by adding acid to the digestive juice to acidify it. Online use requires the digestive juice to maintain a very low pH (<5.5), and a too low pH will reduce microbial activity and lead to a decrease in production rate

[0006] The pH of the digestive juice that is conducive to microbial acid production is neutral or weakly acidic. Under this condition, the main form of the above-mentioned organic acids is the ionic state. Therefore, electrodialysis is an effective way to separate ionic organic acid salts, but the disadvantages are: are other inorganic ions (such as Cl - , CO 3 2- etc.) will cross the ion exchange membrane together, resulting in low product purity, and the further separation difficulty of the mixed salt solution is as follows: [Jones, R.J., Massanet-Nicolau, J., Guwy, A., Premier, G.C., Dinsdale, R.M.,Reilly,M.2015.Removal and recovery of inhibitory volatile fatty acids from mixed acid fermentations by conventional electrodialysis.Bioresource Technology,189,279-284]

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