Enhanced Furfural Production in Deep Eutectic Solvents Comprising Alkali Metal Halides as Additives

The addition of alkali metal halide salts to acidic deep eutectic solvents is here reported as an effective way of boosting xylan conversion into furfural. These salts promote an increase in xylose dehydration due to the cation and anion interactions with the solvent being a promising alternative to the use of harsh operational conditions. Several alkali metal halides were used as additives in the DES composed of cholinium chloride and malic acid ([Ch]Cl:Mal) in a molar ratio of 1:3, with 5 wt.% of water. These mixtures were then used as both solvent and catalyst to produce furfural directly from xylan through microwave-assisted reactions. Preliminary assays were carried out at 150 and 130 °C to gauge the effect of the different salts in furfural yields. A Response Surface Methodology was then applied to optimize the operational conditions. After an optimization of the different operating conditions, a maximum furfural yield of 89.46 ± 0.33% was achieved using 8.19% of lithium bromide in [Ch]Cl:Mal, 1:3; 5 wt.% water, at 157.3 °C and 1.74 min of reaction time. The used deep eutectic solvent and salt were recovered and reused three times, with 79.7% yield in the third cycle, and the furfural and solvent integrity confirmed.

Application Analysis of Medium Temperature Solar Refrigeration System in Civil Buildings

The lithium bromide absorption refrigeration system with medium temperature solar collector as driving heat source was built, and the refrigeration performance of the system was tested and analyzed. The medium-temperature solar collector adopts all-glass vacuum solar collector tube with heat-conducting oil as medium, and the inside of the vacuum tube is composed of heat-conducting medium flow channel on the sunny side and aluminum silicate insulation cotton on the backlight side. Through test and analysis, the medium temperature solar collector of the system can provide stable heat source, and the maximum temperature of solar heating can reach above 150°C in sunny weather and about 80°C in cloudy days. The generator driving heat of the system is stable and efficient. The driving heat of lithium bromide absorption refrigerator is higher than 200 MJ/h, and can reach 300 MJ/h in some periods. The COP of the system can be kept above 0.6 during stable operation, but when the driving temperature of the generator is higher than 80°C, the COP of the system basically does not increase with the increase of the driving temperature.

Energy efficiency of an absorption thermotransformer with two-stage absorption as part of a heat and cold supply complex based on a gas boiler house

The article proposes a scheme for using a lithium bromide absorption thermotransformer (LBATT) with two-stage absorption for deep utilization of the heat of combustion products (CPs) of gas boilers. At the same time, this solution allows heating the dictrict heating systems return water in the cold season. In the warm season, LBATT is used to cool the water of the air conditioning system or process equipment cooling. In this case, heat removal from LBAHT with two-stage absorption in the warm season is carried out using an drycooler. The analysis of the effectiveness of the use of LBATT in the cold and warm seasons is carried out. The theoretical transformation coefficient of LBATT with deep utilization of flue gases reaches 1.72. The theoretical thermal coefficient of LBATT when cooling water in the warm season reaches a value of 0.7.

Design and Analysis of a Solar Energy Driven Tri-generation Plant for power, Heating and Refrigeration

A tri-generation plant producing power, heat and refrigeration has been designed and analyzed. Using solar energy as input. The power side of the plant employs supercritical carbon dioxide (sCO2) recompression cycle. The refrigeration side includes an aqueous lithium bromide absorption system. Thermal energy has been extracted from many places in the plant for heating purposes. A detailed thermodynamics model has been developed to determine performance of the plant for many different conditions. Thermal efficiency, energy effectiveness and exergetic efficiency of the system has been calculated for different operating conditions. It turns out that the pressure ratio of the recombination cycle and effectiveness of the energy exchanger for transferring energy from the power side to the refrigeration side play important roles.

Parametric Theoretical Study of Solar Assisted Cooling System Using Lithium Bromide-Water Pair

In this paper, the effect of parameters of solar absorption system such as evaporator, absorber, condenser, generator temperatures and the mass of the solution on the evaporator cooling load and the coefficient of performance has been explained theoretically. The results show that, increasing of evaporator and condenser temperatures increase the evaporator cooling load, performance coefficient and the Ratio of Circulation while increasing the temperature of condenser and absorber decreases the evaporator cooling load, performance coefficient and the Circulation Ratio. In addition, increasing the solution mass increases the refrigeration power while the performance coefficient and the Circulation Ratio was constant at increasing the solution mass. The reached maximum cooling load was (1.932 kW) at 15 kg solution mass and 100 °C generator temperature, the maximum COP was 0.774 at (10 °C) temperature of evaporator and the peak Circulation Ratio was 0.3066 at (30 °C) temperature of absorber and (100 °C) temperature of generator.