Experimental Study On The Material And Energy Metabolism Process Of Biogas Produced From Different Rank Coals

In order to explore the biochemical metabolism mechanism of the process of coalbased biomethane from the thermal and electrical effects,and to further enhance the understanding of the biogas production characteristics using coal as a substrate,the paper uses lignite from Baiyinhua mine(BYH)and fat coal from Malan mine(ML),coking coal from Shaqu mine(SQ),lean coal from Qidong mine(QD)as fermentation substrates for biogas production simulation experiments.Through phase detection of fermentation process liquid phase parameters(p H,COD,ammonia nitrogen),metabolic intermediate products and thermal effects released by the interaction between coal and microorganisms,and the whole process of monitoring the electrical effects generated in the microbial electrochemical system of the coal fermentation process,combined with material metabolism and Energy metabolism to reveal the biochemical metabolism mechanism of coal anaerobic fermentation process.The results show that:(1)The biomethane output of coal anaerobic fermentation gradually decreases with the increase of coal deterioration.The cumulative gas production of BYH,ML,SQ,and QD coal samples are 152.11 μmol/g,122.78 μmol/g,80.57 μmol/g and 73.14 μmol/g,respectively.The hydrolysis rate of BYH coal samples is faster and the gas production time is earlier than others.bituminous coal.(2)The specific surface area and pore volume of the four coal samples showed a trend of "first decrease and then increase" with the increase of coal rank,Low rank coal has a larger specific surface area and pore size for microorganisms to contact,so the biochemical metabolism in the system is more active.(3)The content of alkanes in the liquid product is the highest,and its content is related to the production of biomethane,and the content drops to the lowest at the end of the reaction;acid substances(myristic acid,octadecanoic acid and oleic acid)are gradually consumed,p H Gradually increase;COD content gradually decreases,ammonia nitrogen content first decreases and then increases,and increases with the degree of deterioration.(4)The phased heat release is correlated with the biomethane production.The reaction heat of BYH coal sample was32.539 J/g on the ninth day of the gas production peak,and the reaction heat peaks of the other three bituminous coals were all at the twelfth day of the gas production.It reached the maximum in days,which were 5.949 J/g,5.37 J/g and 3.429 J/g.(5)Realtime detection of voltage changes in the fermentation system and the results of cyclic voltammetry analysis indicate that the activity or number of electricity-producing bacteria in the BYH coal metabolism system is greater,and the ability of the microorganisms to carry out extracellular electron transfer is also stronger.(6)At the peak of BYH coal sample gas production,the archaeal bacteria are mainly Methanoculleus,which belong to hydrogen-trophic methanogens;while the SQ coal sample is mainly Methanothrix,which belongs to acetic acid fermentation type methanogens;BYH coal samples have Geobacter and Methanosarcina’s direct electron transfer mechanism greatly enhances the methanogenic activity of Methanosarcina.The material metabolism rate of the fermentation system is faster,and the reaction heat released by the metabolic process is also larger.The research starts from the reaction heat effect of fermentation system metabolism and microbial electron transfer effect,and further studies the biochemical metabolism mechanism of coal and microorganisms.It provides a reference for enriching the connotation of microbial production theory of coalbed methane.