To investigate the release and transformation of fuel potassium during biomass gasification, paulownia wood is used in a fixed-bed reactor system during 500âˆ’900 Â°C. Chemical fractionation analysis are performed to study the existing form of fuel potassium. The influences of particle size and gasification temperature are discussed. The results show that release ratio of potassium increases with the gasification temperature. When the temperature is higher than 700 Â°C, the content of water-soluble and NH4Ac-soluble K decreases, and part of other occurrence modes of K turn into the insoluble K gradually. The release ratio of potassium with three different particle sizes reaches 26.65%, 32.53% and 40.56% respectively at 900 Â°C. Increase of particle size inhibits the potassium release and induces the formation of NH4Ac-soluble K. For centimeter-sized samples, potassium content at central is higher than that of surface at 700 Â°C, which is related to the formation of NH4Ac-soluble potassium. The content of potassium at different positions decreases significantly above 700 Â°C.
In this study, a computational fluid dynamics (CFD) model was developed to study the flow and heat transfer characteristics of a 320 MW oxy-fired boiler with dry and wet flue gas recirculation (FGR). The results show that there exist significant differences in the composition and physical properties of flue gas between the air- and oxy-combustion modes and these differences may lead to remarkable differences in the flow, temperature and heat transfer distributions of boiler. Specifically, since the specific heat of CO2 and H2O are higher than that of N2, the flue gas heat capacity of the oxy-combustion case with wet FGR is significantly higher than the air-combustion case leading to lower furnace temperature and heat absorption of furnace wall. Moreover, since the density of CO2 is higher than N2, the overall flow velocity in oxy-fired boiler is lower than that of air-fired boiler, which subsequently affects the boiler flow and temperature distributions in the furnace. The differences in the flow and heat transfer distributions between oxy-fired and air-fired boilers should be taken into consideration when designing new oxy-fuel combustion systems or retrofitting existing air combustion systems to minimize costly modifications to the boilerâ€™s heating surfaces.
Carnot Batteries are a promising approach to store electrical energy in a thermal way. Besides the loading and unloading thermodynamic processes, the heat storage is a field of mayor interest in research. This paper presents an innovative modular storage setup that is easily scalable and contains an immiscible liquid phase to separate the hot and cold side of a sensible water storage. The separation of hot and cold side thus reduces the heat losses and improves the efficiency of the whole storage concept. A pilot plant to study the idea experimentally is in construction.
Hydrogen production could be used to consume excessive renewable energy. Many energy management systems (EMSs) were proposed to link hydrogen production with renewable farms. The majority of the studies, however, are not based on the real-life systems and do not fully utilize the potential of demand response from P2X components. In this paper, we propose an EMS architecture based on the GreenLab Skive industrial cluster that can operate the system with default, economic (minimize operational costs) and sustainable (produce green hydrogen) schedules. EMS utilizes the flexibility from electrolyzer, hydrogen tank, battery and hydrogen consuming plants (HCPs) to provide an optimal dispatch in the economic and sustainable schedule; operating the system in either of them results in operational costs reductions in comparison with default schedule. The hydrogen produced with the sustainable schedule is green and such operation could serve as a backbone of the future sustainable energy system.