Determining potential of subcooling to attenuate hydrodynamic instabilies for steam-water two phase flow

Hydrodynamic instabilities are regarded as important but are undesirable occurrences for the systems used in process industries, which involve steam. These instabilities affect to a great extent the life line of the safe operation of their systems by inducing thermal stresses and steam induced water hammers. On the basis of system operational analysis, it was found that condensation induced hydrodynamic instabilities were responsible for one third of the destructive events in steam driven systems and their attributes in power and process industry. Thus it becomes vital to investigate the influence of critical parameter such as sub-cooling to curb the destructive effects due to hydrodynamic instabilities on to the process equipment. Here for steam water two phase flows, the attenuation of hydrodynamic instabilities due to sub-cooling and inlet pressure has been investigated. It was found that sub-cooling has more pronounced and notable effect on the attenuation of these instabilities

Performance of oscillatory flow reactor and stir tank reactor in solvent fermentation from palm oil mill effluent

Advance in mixing technology has developed a new way of mixing fluids by introducing an oscillatory motion to replace the conventional mechanical agitation or an air bubble displacement. This new way of mixing breakthrough has been implemented in an Oscillatory Flow Reactor (OFR). This research will be focus on the performance of OFR as a bioreactor by comparing with Stir Tank Reactor (STR), which is the traditional device in fermentation. The experimental work was conducted in an OFR and a STR with a working volume of 1.5 l. Solvent production strain, Clostridium acetobutylicum NCIMB 13357 was grown in OFR and STR, using fresh Palm Oil Mill Effluent (POME) as growth medium. All of the experiments were conducted anaerobically under batch mode for 72 hours at constant temperature of 35°C. Comparisons of the growth trend and solvent fermentation performance for both devices were investigated. Total solvents (acetone, butanol and ethanol) produced in an OFR was comparable with that of STR. Total solvents production in OFR is 1.8 times higher than that of STR resulted in total 1.6 g/l of solvents. The results of this investigation showed that OFR has an excellent potential as an alternative device in fermentation processes

Penilaian model matematik bagi pertumbuhan mikroalga Characium sp. UKM1, Chlorella sp. UKM2 dan Coelastrella sp. UKM4 dalam air larut resapan sintetik

Mikroalga berpotensi sebagai agen fikoremediasi air sisa dan metabolit yang terhasil dalam biojisim mikroalga mampu diaplikasikan dalam bidang bioteknologi. Pertumbuhan mikroalga dalam air sisa menjadi petunjuk bahawa mikroalga mampu hidup dalam persekitaran ekstrim dan menjadi agen fikoremediasi air sisa. Oleh itu, model matematik yang terbaik bagi kinetik pertumbuhan mikroalga yang dikultur dalam air sisa perlu dikaji bagi menentukan model yang tepat untuk digunakan pada masa akan datang. Dalam kajian ini, penilaian model matematik yang terbaik terhadap tiga mikroalga tempatan, Characium sp. UKM1, Chlorella sp. UKM2 dan Coelastrella sp. UKM4 yang dikultur dalam air larut resapan sintetik dianalisis dengan menggunakan tiga model matematik iaitu logistik, logistik terubah suai dan Gompertz terubah suai. Selain itu, analisis statistik dijalankan bagi penentuan model terbaik dengan mengambil kira nilai regressi terubah suai (adj R2), ralat tambah kuasa dua (SSE), punca min ralat kuasa dua (RMSE), faktor bias (BF), faktor kejituan (AF) dan peratus ramalan ralat piawai (%SEP). Hasil menunjukkan model yang terbaik bagi ketiga-tiga mikroalga dalam air larut resapan sintetik adalah model Gompertz terubah suai. Ini disebabkan oleh beberapa ciri antaranya plot residual yang mendekati model matematik, nilai BF yang mendekati nilai satu, serta nilai terendah %SEP berbanding model matematik yang lain. Kesimpulannya, model Gompertz terubah suai adalah model penyesuaian yang terbaik terhadap pertumbuhan mikroalga dalam air larut resapan sintetik

ADSORPTION - DESORPTION SYSTEM FOR CO2 REMOVAL IN BIOGAS USING NATURAL ZEOLITE - BASED ADSORBENT

This study aimed to remove CO2 from air-CO2 mixture using natural zeolitebased adsorbent pellets through adsorption and to regenerate the adsorbents using air through desorption. The experiment was conducted to determine the percentage of CO2 removal and breakthrough curve characteristics by varying the flow rate of the air-CO2 mixture and the type of adsorbent pellet. The residual CO2 content of purified gas was analysed every minute and stored in the gas collector. Pure air with ambient temperature ranging from 30 to 40 °C flowed through a column for desorption of CO2 in the saturated pellet adsorbent. Results concluded that the best percentage of CO2 removal was 92.5% by using adsorbent pellet with particle size of 140 mesh, calcination temperature 400 °C for four hours and a flow rate of mixed gas at 200 ml/min. This characteristic also described the optimum CO2 desorption that is achieved at 40 °C of air temperature and flow rate of 200 ml/min for 20 minutes. The adsorption equilibrium was fitted using Langmuir isotherm with R2 correlation value of 0.9962. Modelling of adsorption kinetics to describe breakthrough curve used pseudo-order and Elovich kinetics. The results showed that the pseudo-order kinetics provided good results under operating conditions

NUMERICAL SIMULATION OF FLUID FLOW BEHAVIOUR ON SCALE UP OF OSCILLATORY BAFFLED COLUMN

The fluid dynamics of oscillatory flow in a baffled column of 145 mm diameter was investigated numerically in this work. This numerical simulation was carried out by a 2D laminar unsteady solver using CFD package Fluent® 6.3. From the simulation, data on surface velocity were collected and velocity ratio was calculated to determine the intensity of mixing which were the main operating parameters in oscillatory flow in a baffled column. The suitable operating parameters of oscillatory baffled column of 145 mm diameter were also determined in this work. It was found that the oscillation amplitude was more dominant for obtaining desirable mixing results compare to oscillation frequency

Recalcitrant organics removal using adsorption and biofilm process

Recalcitrant organics compounds is one of the harden problem faced by the wastewater treatment engineer because of these compounds are hard to treat and can passed through the conventional WWTP. Some of the recalcitrant organics, such as pentachlorophenol had found toxicgenic and carcinogenic to human and animals. The carbon adsorption was one of the common conventional methods for removing of these compounds. However, the treatment does not destroy these recalcitrant organics but just merely transferring it to another medium

Comprehensive evaluation of the integrated membrane contactor-microalgae photobioreactor system for simultaneous H2 purification and CO2 treatment from biomass fermented gases

Biohydrogen (H2) has been identified as a potential renewable energy source to substitute energy-based fossil fuel that can be produced from biomass fermentation. However, carbon dioxide (CO2) is also commonly present in the biogas mixture and must be properly treated as it could contribute to the climate change phenomenon. In this study, an integrated membrane contactor-microalgae photobioreactor system is applied to allow simultaneous H2/CO2 treatment from biomass fermented biogases. A comprehensive evaluation of the effectiveness of the integrated system was investigated by screening the essential operating parameters of the system using One Factor at a Time (OFAT) technique followed by optimization Response Surface Methodology (RSM). Serial investigations of the process parameters, the optimum condition was at a pH of 10 with gas and liquid flow rates at the respective levels of 0.1 L/min and 0.5 L/min, while the microalgae concentration was 0.6 g/L. At these optimum conditions, the H2 purity was found to have increased remarkably, from 69.4% to 83.2%. In a long-term separation performance using the optimized conditions, microalgae solution was found to be capable of sustaining its performance at a longer time with only 2% performance dropped observed within 540 min of the operational time. In conclusion, the use of microalgae in a membrane contactor system could be a promising technique for treating these fermented gases, in a move towards carbon neutrality

Kinetic Model of Thermophilic Biohydrogen Production from POME

The study of fermentation kinetic parameters are crucial to understanding the environmental factors affect on biohydrogen production. Kinetic models for hydrogen production from anaerobic digestion of palm oil mill effluent (POME) by mixed culture were developed based on published work. The models accounted for substrate limitation, substrate inhibition, hydrogen production, and endogenous decay rate. Data from previous literature were used to compare four microbial growth kinetic models for hydrogen production in an ASBR system. The estimated values of the maximum specific growth rate (μm) were found to be 0.371 h-1. In this study, the parameters of Y, kd, and B0 calculated were 2.64 gVSS/gCOD, 0.053 h-1, and 0.133 L H2/gCOD, respectively. The model fitting was found to be in good agreement with the experimental and can be utilized for the optimization and design of the process

Assessment of biohydrogen injection system through Arduino setting in photosynthetic and dark fermentation by local microalgae culture

Biohydrogen (a hydrogen gas produced by biological methods) is one of the most sustainable sources of energy for electricity generation. Hydrogen gas combustion produces only water without the release of greenhouse gases emission. Microalgae are the microorganisms that can produce biohydrogen through photosynthesis and dark fermentation. In this study, the local microalgae isolate, Chlamydomonas sp.UKM6 has been used to generate biohydrogen using both fermentation methods under anaerobic conditions. Photosynthesis fermentation was carried out using the live culture of UKM6 under continuous illumination while dark fermentation was carried out using the biomass of UKM6 with the palm oil mill effluent (POME) sludge as an inoculum. The resulting hydrogen gas is automatically injected into the fuel cell system using the newly developed Arduino Uno. Using data presented from the Arduino settings program, the biomass of UKM6 in dark fermentation produces the highest hydrogen gas and voltage at 30.89 ppm and 0.92 mV, respectively. Based on the results, it can be concluded that microalgae have the potential to generate energy through the production of biohydrogen which can be further analyzed using fuel cell technology. This system can be further improved in the future to measure energy generated directly and effectively

Effect of cellulose nanocrystals and carboxylated multiwalled carbon nanotubes on performance of polyethersulfone membrane for humic acid removal

Persistent declines in flux due to membrane fouling result in decreased treated water production, higher energy consumption, and a frequent need for chemical cleaning. Carbon nanotubes-based membranes have shown remarkable separation capabilities in water treatment processes while being relatively resistant to biofouling. Cellulose-based membranes, on the other hand, have demonstrated outstanding biocompatibility and versatile surface chemistry. In the current study, a hybrid polyethersulfone (PES) membrane was synthesized by integrating with single cellulose nanocrystals (CNC), single carboxylated multiwalled carbon nanotubes (MWCNT), and a mixture of CNC and MWCNT utilizing the phase inversion method. This combination of nanomaterials was aimed at eliciting synergistic effects to enhance the overall membrane performance. The evaluation of the hybrid membranes encompassed an analysis of membrane structure, morphology, porosity, hydrophilicity, water flux, humic acid (HA) rejection, and the flux recovery ratio (FRR). The experimental outcomes unveiled notable changes in the morphology of the polymeric membrane when CNC and MWCNT were introduced into the PES membrane structure. All hybrid membranes displayed heightened hydrophilicity compared to the original pristine PES membrane. The PES/CNC0.3/CNT0.03 membrane demonstrated exceptional performance, with a remarkable HA rejection rate and FRR of 93.05% and 92.09%, respectively. This outstanding performance can be attributed to the synergistic combination of two separation mechanisms: electrostatic repulsion and size exclusion. The inclusion of MWCNTs into the hybrid membranes significantly reduced humic acid-induced membrane fouling due to improve surface hydrophilicity and decreased membrane roughness