A TRNSYS Simulation Case Study on Utilization of Heat Pump

This paper presents a TRNSYS simulation case study on the integration of a heat pump into a hot water and cold water storage systems for the purpose of providing heating and cooling to a residential home or office building in a tropical climate. The motivation is to utilize waste heat rejected by the heat pump.The heat pump is integrated with two water storage tanks. One is the cold water tank where heat is extracted by the heat pump and the other is the hot water which stores the heat rejected by the heat pump. The cold water tank provides cooling water for air conditioning to the building. The hot water tank is used for daily usage like bathing and washing. The sizing of the two storage tanks and the balancing of the heat transfer between the two tanks are important design factors to maintain suitable temperatures in the storage tanks. The paper discusses the performance of the integrated system under different operational modes and the effects of each storage tank size on the performance.Key words: Heat pump; Heating; Cooling; TRNSYS; Simulation; Air conditionin

Viruses infecting periwinkle (Catharanthus roseus L.) in Western Saudi Arabia

Periwinkle (Catharanthus roseus L.) is an ornamental plant widely grown in the Mecca region in the Kingdom of Saudi Arabia (KSA). Different symptoms similar to those induced by viruses (mosaic, vein clearing, mottling, yellowing, flower variegation) prompted surveys in eight different regions of KSA to assess the presence of periwinkle-infecting viruses, i.e. Tomato spotted wilt virus (TSWV), Cucumber mosaic virus (CMV), Lettuce mosaic virus (LMV), Catharanthus mosaic virus (CatMV) and Catharanthus yellow mosaic virus (CYMV). Two hundred and forty leaf samples were collected from naturally infected nurseries, gardens and landscape plantings, and tested by DAS-ELISA, RT-PCR and PCR assays. Results showed that all five viruses were present in the surveyed areas, with incidence of infection reaching 58%. TSWV was the most widespread, found in 44% of samples, followed by CYMV (35%), whereas CatMV (15%), CMV (11%) and LMV (6%) were present to lesser extents. The virus incidence ranged between 43% in Rabigh to 77% in Taif. This is the first report of CYMV and CatMV in KSA, and of TSWV, LMV and CMV in periwinkle in western Saudi Arabia. The high incidence of viruses and of multiple infections in periwinkle plants endangers this crop in KSA, so a sanitation programme for eliminating virus infections is desirable

Propane Oxydehydrogenation to Propylene Over Molybdenum-based Catalysts

Catalytic oxidative dehydrogenation of propane to propylene has received great research interest in recent years. This reaction stands as a promising alternative to steam cracking and catalytic dehydrogenation, although most of the catalysts proposed need further improvements. This work presents results of the propane oxidative dehydrogenation reaction on alumina supported chromium-molybdenum oxides catalysts - CrxMo(1− x) (where x = 0 − 1). The reaction was conducted at atmospheric pressure, 300 − 420 °C and total feed flowrate of 75 cm3/min (20 cm3/min propane, 5 cm3/min oxygen and the balance helium). The catalysts are active for the reaction. Increase in Mo-ions in the catalysts decreased the reducibilities and changed the nature of the lattice oxygen as indicated by TPR and XPS results. The catalysts with lower reducibilities exhibited corresponding increase in the propylene selectivities. Alkali metals (Li, K, Cs) doped Cr gMo2 (alkali/CrMo weight ratio of 0 − 0.175), showed maxima in both propane conversion and propylene yields for the ratio ranges used. One of the catalysts (Cs/CrMo = 0.125) exhibited the best performance (propane conversion is 15.1% and selectivity to propylene is 64.5%) at 420 °C. It holds promise as a catalyst for oxidative dehydrogenation of propane. Keywords: Oxidative dehydrogenation, propane, chromium-molybdenum oxides catalysts, propylene, alkali metals promoter

Catalytic cracking of gas oils in electromagnetic fields: Reactor design and performance

The application of dielectric heat transfer in the catalytic cracking and hydrocracking of gas oils has been investigated. A three-phase spouted-bed catalytic reactor has been designed and operated using dielectric radio frequency (RF) heating. The electromagnetic power was transferred to the reactor by a 27.12 MHz RF generator acting through two capacitor plates. In this technique, heat is generated to the catalyst held in the electromagnetic field and thermal energy dissipated to the surroundings of the catalyst volume preventing carbon formation by eliminating secondary reactions. Energy transfer from the RF filed to the reaction was solely dependent on the dielectric properties of solids in the reactor, effectively the catalyst or transient carbon. Three zeolitic catalysts have been tested. These catalysts were 13X, 5A and Ammonium Y Zeolite. Two different gas oils have been used as feedstocks for the experiments. Saudi Light Vacuum Gas Oil (SALVGO) supplied by Saudi Aramco Oil and North Sea Light Gas Oil (BPLGO) supplied by BP Oil. A comparative study of the two gas oils cracked over 13X zeolitic catalyst has been presented. The analysis of the feedstocks have shown that SALVGO contains hydrocarbons in the range C11-C30 with average molecular weight of 294, while BPLGO contains hydrocarbons in the range C11-C25 with average molecular weight of 243. The analysis of cracked products have shown a production of lower olefins such as propene and butene with hydrogen sulphide from SALVGO at a conversion of 87% and aromatics such as benzene and toluene from BPLGO at a conversion of 72%. The successful use of zeolitic catalyst in producing lower olefins and aromatics with an RF dielectric reactor suggests exploring this type of reactor for objectives such as the production of reformulated gasoline, in which butene is used as feedstock for production of high-octane gasoline components such as MTBE and alkylate

Improved regulatory control of industrial gas phase ethylene polymerization reactors

Chemical Engineering Department, King Saud University.This paper investigates the application of two techniques to improve the PI control performance when implemented to stabilize the operation of gas phase polyethylene reactors around optimal operating point which is open-loop unstable. The first technique deals with improving the performance of SISO control loop through employing on-line adaptive tuning strategy. The purpose of the tuning strategy is to force the closed-loop response to fit inside desired time-domain specification envelope by automatically adapting the PI setting values. The second technique deals with improving the MIMO control performance by simple selection of proper control structure design. The objective of the proposed control design is to avoid the procedure of screening various control structure candidates. Moreover, since there are more inputs than outputs, split-range configuration is used to utilize all available manipulated variables. This configuration allow for tight control. Simulation results demonstrated the success of the proposed methods to provide better regulatory control performance when compared to what have been reported in earlier work

Transalkylation and isomerization of ortho-diethylbenzene with benzene using trifluoromethanesulphonic acid catalyst: Kinetic analysis.

The kinetics of transalkylation and isomerization of ο-diethylbenzene (ο-DEB) in the presence of benzene (B) using trifluoromethanesulphonic acid as a catalyst has been studied. On the basis of the product distribution obtained, transalkylation, disproportionation, and isomerization reactions have been considered. The main product of the reaction was ethylbenzene. These reactions are conducted in a closed liquid batch reactor with continous stirring under dry nitrogen and atmospheric pressure over the temperature range of 288-308 K. Power law type model have been tested for the main transalkylation and disproportionation reactions, while the isomerization reactions followed a first-order mechanisms. Increasing the molar ratio of B to ο-DEB resulted in decreasing the yield of ethylbenzene. The apparent activation energy of the transalkylation reaction was found to be 50 kJ/mole, while that of disproportionation reaction was 29 kJ/mole. The reproducibility of the experimental product distribution occurred with an average relative error of 5%.

Selection of optimum chromium oxide-based catalysts for propane oxidehydrogenation

Propane oxidative dehydrogenation has been studied at 350-500°C, 1.0 bar and feed flow rate of 75 cm3/min over several supported chromium oxide-based catalysts. Effects of various chromium loadings, different supports, catalyst precursors and reaction conditions were investigated in an attempt to select an optimum catalyst for the reaction. Chromium oxides of different loadings ranging from 0.1 to 20 wt.% on γ-Al2O3 were tested. At 450°C, 10 wt.% loading exhibited propane conversion of 19%. γ-Al2O3 gave the best performance when MgO, TiO2, SiO2 and γ-Al2O3 were tested as supports. As a precursor, Cr(NO3)3•9H2O exhibited the best results compared with K2Cr2O7, CaCr2O7, Na2Cr2O7, Cr2SO4•12H2O and CrO3. Effects of reaction temperatures and feed compositions were also evaluated on a 10 wt.% Cr-Al-O catalyst. The maximum selectivity to propene obtained was 61% while the yield was 18%. The 10 wt.% Cr-Al-O catalyst was characterized by X-ray diffraction patterns (XRD), temperature-programmed reduction (TPR) and X-ray photoelectron spectroscopy (XPS) which confirmed the presence of both Cr3+ and Cr6+ in the calcined catalyst and, also, the predominance of Cr3+ in the spent catalyst..