Incomplete understanding of biogas chemical hazards — Serious gas poisoning accident while unloading food waste at biogas plant

Risberg

Westerlund

et al. 2022

Preprint

Background The use of food waste as feedstock shows high production of biogas via anaerobic digestion but requires efficient heat transfer in food waste slurry at heating and cooling processes. The lack of rheological properties hampered the research on the heat-transfer process for food waste slurry. Referentially, the twisted hexagonal and elliptical rubes have been proved as the optimal enhanced geometry for heat transfer of medium viscous slurries with non-Newtonian behavior and Newtonian fluids, respectively. It remains unknown whether improvements can be achieved by using twisted geometries in combination with food waste slurry in processes including heating and cooling. Results Food waste slurry was observed to exhibit highly viscous, significant temperature-dependence, and strongly shear-thinning rheological characteristics. Experiments confirmed the heat-transfer enhancement of twisted hexagonal tubes for food waste slurry and validated the computational fluid dynamics-based simulations with an average deviation of 14.2%. Twisted hexagonal tubes were observed to be more effective at low-temperature differences and possess an enhancement factor of up to 2.75; while twisted elliptical tubes only exhibited limited heat-transfer enhancement at high Reynolds numbers. The heat-transfer enhancement achieved by twisted hexagonal tubes was attributed to the low dynamic viscosity in the boundary layer induced by the strong and continuous shear effect near the walls of the tube. Conclusions This study determined the rheological properties of food waste slurry, confirmed the heat-transfer enhancement of the twisted hexagonal tubes experimentally and numerically, and revealed the mechanism of heat-transfer enhancement based on shear rate distributions.

Section: Introductionmentioning

confidence: 99%

Heat-Transfer Performance of Twisted Tubes for Highly Viscous Food Waste Slurry from Biogas Plants

Risberg

Westerlund

et al. 2022

Preprint

“…Food waste, a type of typical organic solid waste, is produced in large quantities and can severely contaminate air, water, and soil if it is not collected, transported, and stored properly [ 1 ]. Fortunately, food waste is degradable and is used as a desirable substrate in the production of biogas via the anaerobic digestion (AD) process [ 2 – 4 ]. Mohsen et al [ 5 ] designed a laboratory-scale semi-continuous membrane-assisted anaerobic reactor to produce biogas from food waste slurry (FWS) with a total solid (TS) content of 13%.…”

Section: Introductionmentioning

confidence: 99%

Heat-transfer performance of twisted tubes for highly viscous food waste slurry from biogas plants

Risberg

Westerlund

et al. 2022

Biotechnol Biofuels

Background The use of food waste as feedstock shows high production of biogas via anaerobic digestion, but requires efficient heat transfer in food waste slurry at heating and cooling processes. The lack of rheological properties hampered the research on the heat-transfer process for food waste slurry. Referentially, the twisted hexagonal and elliptical rubes have been proved as the optimal enhanced geometry for heat transfer of medium viscous slurries with non-Newtonian behavior and Newtonian fluids, respectively. It remains unknown whether improvements can be achieved by using twisted geometries in combination with food waste slurry in processes including heating and cooling. Results Food waste slurry was observed to exhibit highly viscous, significant temperature-dependence, and strongly shear-thinning rheological characteristics. Experiments confirmed the heat-transfer enhancement of twisted hexagonal tubes for food waste slurry and validated the computational fluid dynamics-based simulations with an average deviation of 14.2%. Twisted hexagonal tubes were observed to be more effective at low-temperature differences and possess an enhancement factor of up to 2.75; while twisted elliptical tubes only exhibited limited heat-transfer enhancement at high Reynolds numbers. The heat-transfer enhancement achieved by twisted hexagonal tubes was attributed to the low dynamic viscosity in the boundary layer induced by the strong and continuous shear effect near the walls of the tube. Conclusions This study determined the rheological properties of food waste slurry, confirmed the heat-transfer enhancement of the twisted hexagonal tubes experimentally and numerically, and revealed the mechanism of heat-transfer enhancement based on shear rate distributions.

“…For example, Shinar in Israel has verified that the use of seat belts is positively correlated with the age and education level of the drivers [17]. Vehicle conditions, road conditions, environmental conditions, and more and more social and economic factors have been gradually taken into account to study the impacts of fatal traffic accidents [18][19][20]. Researchers from Japan have evaluated the traffic safety of 46 prefectures in Japan and concluded that natural binding force, such as social rules and social capital, could reduce the dangerous driving behaviors [21].…”

Section: Introductionmentioning

confidence: 99%

Critical Factors Analysis of Severe Traffic Accidents Based on Bayesian Network in China

Journal of Advanced Transportation

Yang

2020

The purpose of this study is to minimize the negative influences of the severe traffic accidents in China by profoundly analyzing the complex coupling relations among accident factors contributing to the single-vehicle and multivehicle traffic accidents with the Bayesian network (BN) crash severity model. The BN model was established by taking the critical factors identified with the improved grey correlation analysis method as node variables. The severe traffic accident data collected from accident reports published in China were used to validate this model. The model’s efficiency was validated objectively by comparing the conditional probability obtained by this model with the actual value. The result shows that the BN model can reflect the real relations among factors and can be seen as the target network for the severe traffic accidents in China. Besides, based on BN’s junction tree engine, five-factor combination sequences for the number of deaths and three-factor combination sequences for the number of injuries were ranked according to the severity degree to reveal the critical reasons and reduce the massive traffic accidents damage.