Exergoeconomic Evaluation and Optimization of Dual Pressure Organic Rankine Cycle (ORC) for Geothermal Heat Source Utilization

In the present study, a dual-pressure organic Rankine cycle (DORC) driven by geothermal hot water for electricity production is developed, investigated and optimized from the energy, exergy and exergoeconomic viewpoint. A parametric study is conducted to determine the effect of high-stage pressure and low-stage pressure variation on the system thermodynamic and exergoeconomic performance. The DORC is further optimized to obtain maximum exergy efficiency optimized design (EEOD case) and minimum product cost optimized design (PCOD case). The exergy efficiency and unit cost of power produced for the optimization of EEOD case and PCOD case are 33.03% and 3.059 cent/kWh, which are 0.3% and 17.4% improvement over base case, respectively. The PCOD case proved to be the best, with respect to minimum unit cost of power produced and net power output over the base case and EEOD case.

Design and analysis of dual mixed refrigerant processes for high-ethane content natural gas liquefaction

Recovery and purification of ethane has a significant impact on economic benefit improvement of the high-ethane content natural gas.However,current LNG-NGL integrated processes mainly focus on conventional natural gas,which are not applicable to natural gas with high ethane content.To fill this gap,three dual mixed refrigerant processes are proposed for simulation study of high-ethane content natural gas liquefaction.The proposed processes are optimized by a combination method of sequence optimization and genetic algorithm.Comparatively analysis is conducted to evaluate the three processes from the energetic and exergetic points of view.The results show that the power consumption of Process 3 which compressing natural gas after distillation is the lowest.For safety or other considerations,some common compositions of the mixed refrigerant may need to be removed under certain circumstances.Considering this,case studies of mixed refrigerant involving six composition combinations are carried out to investigate the effects of refrigerant selection on the process performance.

Dual metal ions/BNQDs boost PMS activation over copper tungstate photocatalyst for antibiotic removal:Intermediate,toxicity assessment and mechanism

In the metal-based peroxymonosulfate(PMS)activation process,the sluggish surface redox cycle of metal ions generally hampered the efficiency of PMS activation for pollutant removal.Herein,Codoped CuWO 4/BN quantum dots(CW/Co/BNQDs)photocatalysts were developed to realize Cu^(2+)/Cu+and Co^(2+)/Co^(3+)dual ions redox cycles for PMS activation,which would facilitate the tetracycline(TC)removal.CW/4Co/2BNQDs could degrade 94.8%TC within 30 min in PMS/Vis system,and the apparent rate constant of CW/4Co/2BNQDs was 2.7 times and 1.2 times higher than those of CW and CW/4Co,respectively.The improved TC degradation performance could be attributed to the synergetic effect between BNQDs and dual redox cycles.X-ray photoelectron spectroscopy(XPS)spectra of samples before and after the reaction demonstrated that BNQDs were beneficial for accelerating the Cu^(2+)/Cu+and Co^(2+)/Co^(3+)redox cycles in CW/4Co/2BNQDs,further boosting the activation of PMS in TC degradation.Experiments of different radical scavengers revealed that the SO_(4)^(·−)/·OH/h+/^(1)O_(2)reactive species participated in the PMS activation for the TC degradation process.The possible TC degradation pathway and intermediate toxicity were detailed investigated.In addition,CW/4Co/2BNQDs exhibited outstanding photocatalytic activity over five consecutive cycles,which illustrated that it was supposed to be a reliable PMS activator over antibiotic elimination for practical application.And this work shed new light on constructing dual redox cycles for efficient PMS activation.