Biogas production of lignite and variation characteristics of cations in liquid phase system

To study the law of lignite biogas production and the variation characteristics of common cations in liquid phase system, Shengli lignite in Inner Mongolia was used as the gas production substrate, and the gas production microorganism in the water from the coalbed methane well in the Sihe mining area as fermentative flora, a 5 L anaerobic fermentation tank was used to simulate the biogas production experiment, and the concentrations of NH₄⁺, K⁺, Ca²⁺, Mg²⁺ and Na⁺ in the fermentation broth were monitored by ion chromatography. The results show that:The simulated biogas production period of Shengli bulk lignite is 33 days; It is divided into three stages:slow phase, rapid rise phase, and steady phase. The net methane production of 33 days is up to 23 μmol/g coal. The concentrations of NH₄⁺(741.5 mg/L)and K⁺ (994.5 mg/L) ions is the most obvious in the gas production system, followed by Ca²⁺(26 mg/L), Mg²⁺(10.7 mg/L), and Na⁺(72 mg/L), the results showed that five cations in the fermentation broth were all involved in the biogas production process of lignite, and were released and utilized in varying degrees. There is a certain correlation between the biogas production of lignite and the physicochemical of the fermentation broth. The gas production per unit coal is positively correlated with NH₄⁺ and K⁺, negatively correlated with Ca²⁺ and Mg²⁺. In addition, NH₄⁺ is positively correlated with K⁺ and Ca²⁺ is positively correlated with Mg²⁺. The five cations of K⁺, Ca²⁺, Mg²⁺ and Na⁺ in lignite biogas liquid phase system will be slowly released and readsorbed with the anaerobic degradation of organic components in lignite, and they can be used by microorganisms to participate in the biochemical reaction in cells.