Improved energy utilization efficiency via adding solar radiant heating mode for traditional bioreactor to dispose straw: Experimental and numerical evaluation

Effect of Phase Change Materials and Phase Change Temperature on Optimization of Design Parameters of Anaerobic Reactor Thermal Insulation Structure

Direct-absorption anaerobic reactors can maintain the fermentation process of microorganisms by utilizing solar absorption and scattering media in the biogas reactor to improve the slurry temperature. Direct-absorption heating alone can save the corresponding electric energy and ensure the normal fermentation process of the biogas slurry in the reactor, but there is still the problem of temperature fluctuation. In order to improve the stability of the fermentation process, it is proposed to optimize the design of this kind of reactor by adding paraffin phase change material. This article mainly studies the influence of paraffin phase change material added on the top and side of the reactor in the fermentation process and gives the corresponding design parameters for different climatic conditions, which lays a theoretical reference for the design process of this kind of reactor.

Enhanced and environment-friendly chemical looping gasification of crop straw using red mud as a sinter-resistant oxygen carrier

Syngas production from biomass gasification is a promising technology, which is widely used in the chemical industry. Crop straw and red mud are typical agricultural and industrial wastes, respectively, which are cheap and widespread; however, they cause serious environmental pollution due to the open burning of straw and the toxicity and alkalinity of red mud. In the present work, we converted crop straw into syngas by chemical looping gasification using red mud as a sinter-resistant oxygen carrier. The reactivity of red mud, the syngas yields, and the air pollutant emissions under different conditions were systematically investigated through a thermo-gravimetric analyzer and mass spectrometer. Compared with pure Fe₂O₃, red mud can promote the syngas yields from crop straw gasification owing to the presence of inert Al₂O₃ and SiO₂. Red mud can effectively reduce the emission of air pollutants owing to the presence of alkaline components such as CaO and Na₂O. As the Fe₂O₃/fuel mass ratio increases, the syngas yield increases and the air pollutant emissions simultaneously reduce; whereas the syngas yield and the air pollutant emissions decrease with increasing heating rate. After calcination at high temperature, the structure of red mud remains stable with slight agglomeration, and can be easily regenerated. Therefore, the promising results provide a breakthrough for efficient utilization and disposal of both crop straw and red mud.

Evaluation of methane production and energy conversion from corn stalk using furfural wastewater pretreatment for whole slurry anaerobic co-digestion

In this study, corn stalk (CS) was pretreated with furfural wastewater (FWW) for whole slurry anaerobic digestion (AD), which increased the degradability of CS components, changed the parameters in pretreatment slurry and improved the biochemical methane potential (BMP). The ultimate goal was to optimize the time and temperature for FWW pretreatment and evaluate whether FWW pretreatment is feasible from BMP and energy conversion. The results of path analysis suggested that lignocellulosic degradability (LD) was the main factor affecting methane production with the comprehensive decision of 0.7006. The highest BMP (166.34 mL/g VS) was achieved by the pretreatment at 35 °C for 6 days, which was 70.36% higher than that of control check (CK) (97.64 mL/g VS) and the optimal pretreatment condition was predicted at 40.69 °C for 6.49 days by response surface methodology (RSM). The net residual value (NRV) for the pretreatment of 35 °C and 6 days was the highest (0.6201), which was the most appropriate condition for AD in real application.

Rapid detection of carbon-nitrogen ratio for anaerobic fermentation feedstocks using near-infrared spectroscopy combined with BiPLS and GSA

Near-infrared spectroscopy (NIRS) is an efficient method for detecting the content of carbon and nitrogen in many materials, which solves the problems of the time-consuming and high-cost traditional chemical analysis method. To quickly detect the carbon-nitrogen ratio (C/N) for the anaerobic fermentation (AF) feedstock using NIRS, a genetic simulated annealing algorithm (GSA) is presented based on a genetic algorithm combined with a simulated annealing algorithm. By combining GSA with backward interval partial least squares (BiPLS), we construct a BiPLS-GSA algorithm to optimize the characteristic wavelength variables of NIRS; this algorithm significantly reduced the number of wavelength variables involved in modeling and effectively improved the detection accuracy and efficiency of the model. The determination coefficients, root mean squared error, mean relative error (MRE) and residual predictive deviation for the validation set in the BiPLS-GSA regression model were 0.9067, 7.6676, 5.5274%, and 3.5626, respectively. Meanwhile, compared to the entire spectrum model, the MRE was decreased by 16.54% in the BiPLS-GSA-based model. The research in this paper improves the adaptability of the prediction model based on optimizing sensitive wavelength variables for C/N, which provides a new way for rapid and accurate measurement of the C/N of AF feedstock.