Silica removal from Mokai, New Zealand, geothermal brine by treatment with lime and a cationic precipitant

Preliminary experiments using two chemicals (CaO, a quicklime, and a cationic nitrogen-bearing precipitant, EC-004) to remove silica from geothermal brine were undertaken at the Mokai geothermal plant, New Zealand. The brine was mixed with the reagent (CaO or EC-004). The reaction was studied from the start of the experiment (NRT, 0 min, no retaining time) and after 15 min (15RT) at 90 °C. The concentration of silica in the brine was initially 954 mg/l, and decreased linearly with increasing reagent concentration. When CaO is added, the silica concentration at 15RT was 200 mg/l lower than at NRT and became almost zero on addition of 1.5 g/l. In contrast, when EC-004 is added, the total silica concentration nearly reaches the solubility of amorphous silica at 90 °C. In order to prevent silica scaling in Mokai brines cooled to 90 °C, the CaO and EC-004 added should be individually adjusted to 0.5 g/l and 80 mg/l, respectively.     

Methane production from antibiotic bearing swine wastewater using carbon-based materials as electrons' conduits during anaerobic digestion

The impact of granular-activated carbon (GAC), graphite felt (GF), and activated carbon cloth (ACC), and two veterinary antibiotics, oxytetracycline (OTC) and enrofloxacin (ERX), was evaluated during the production of methane from the anaerobic digestion of swine effluent. The results showed that GAC (10 g/L) increased 3.0-fold the methane production and 1.4-fold the organic matter removal efficiency, with respect to the control in the presence of OTC (10 mg/L). With ERX, GAC also increases the production of methane with respect to ACC and GF. Adsorption experiments reveal the affinity of antibiotics to carbon materials; nonetheless, even though GAC adsorbed lesser antibiotics, which would mean that antibiotic toxicity remained, the production of methane with GAC was higher. The microbial electron-accepting capacity of GAC (0.57 mmol/g) indicates that electrons from organic matter's oxidation are driven to the material and, subsequently, may act as an electron donor for methanogens to promote methane production. Finally, ERX showed the capacity to act as a redox mediator to reduce Fe(III) up to 1.6-fold higher than the control; nonetheless, it was not reflected in improving the production of methane.     

Influence of operating variables on the aqueous-phase reforming of glycerol over a Ni/Al coprecipitated catalyst

A systematic study focused on the aqueous-phase reforming of glycerol has been carried out in order to analyze the influence of several operating variables (system pressure, reaction temperature, glycerol content in feed, liquid feeding rate and catalyst weight/glycerol flow rate ratio) on the gas and liquid products. A continuous flow bench scale installation and a Ni/Al coprecipitated catalyst were employed. The system pressure was varied from 28 to 40 absolute bar, the reaction temperature was analyzed from 495 to 510 K, the glycerol content in the feed was studied from 2 to 10 wt%, the liquid feeding rate was changed from 0.5 to 3.0 mL/min and the catalyst weight/glycerol flow rate ratio varied from 10 to 40 g catalyst min/g glycerol. The main gas products obtained were H₂, CO₂ and CH₄, while the main liquid products were 1,2-propanediol, ethylene glycol, acetol and ethanol. A W/m_glycerol ratio of 40 g catalyst min/g glycerol, 34 bar, 500 K, 5 wt% glycerol and 1 mL/min, resulted in a high yield to H₂ (6.8%), the highest yield to alkanes (10.7%), the highest 1,2-propanediol yield (0.20 g/g glycerol) and the highest ethylene glycol yield (0.11 g/g glycerol). The highest acetol yield (0.06 g/g glycerol) was obtained at 34 bar, 500 K, 5 wt% glycerol, 20 g catalyst min/g glycerol and 3 mL/min.     

Particle image velocimetry experimental and computational investigation of a blood pump

Blood pumps have been adopted to treat heart failure over the past decades.A novel blood pump adopting the ro-tor with splitter blades and tandem cascade stator was developed recently.A particle image velocimetry (PIV) experiment was carried out to verify the design of the blood pump based on computational fluid dynamics (CFD) and further analyze the flow properties in the rotor and stator.The original sized pump model with an acrylic housing and an experiment loop were constructed to perform the optical measurement.The PIV testing was car-ried out at the rotational speed of 6952±50 r/min with the flow rate of 3.1 l/min and at 8186±50 r/min with 3.5 l/min,respectively.The velocity and the Reynolds shear stress distributions were investigated by PIV and CFD,and the comparisons between them will be helpful for the future blood pump design.     

Petroleum contaminated ground-water: Remediation using activated carbon

Ground-water contamination resulting from the leakage of crude oil and refined petroleum products during extraction and processing operations is a serious and a growing environmental problem in Nigeria. Consequently, a study of the use of activated carbon (AC) in the clean up was undertaken with the aim of reducing the water contamination to a more acceptable level. In the experiments described, crude-oil contamination of ground water was simulated under laboratory conditions using ground-water samples collected from existing hand-dug wells at Eagle Island, Port Harcourt, Nigeria. Different masses of the absorbent (i.e., activated carbon) were then added to the samples of ground water. The so treated water samples were left to equilibrate for 7 days, after which the total petroleum hydrocarbon (TPH) contents of the samples were measured. Adsorption isotherms were derived for the two forms of activated carbon used, namely granular activated-carbon (GAC) and powdered activated-carbon (PAC). Results of the TPH analyses showed that activated carbon is an excellent means for the stripping-off of the contaminant: there were decreases in contaminant concentration from an initial concentration of 9304.70 mg/l to average final concentrations of 361.00 and 12.37 mg/l, that is, 96% and 99.9% resulting from the same amounts of GAC and PAC applications respectively. The results of this study revealed that the powdered form of AC would be very effective in the remediation of petroleum-hydrocarbon contaminated ground water and its use is therefore recommended.     

过滤体对柴油机排气微粒粒径分布的影响

建立了柴油机排气微粒测量装置,对泡沫陶瓷与壁流式蜂窝陶瓷两种过滤体前后的柴油机排敢中的微粒分布进行了测量,发现壁流式蜂窝陶瓷对不同大小的微粒都有较高的过滤效率,而泡沫陶瓷过滤体对微粒的过滤效率与流速、微粒大小及泡沫孔参数有密切关系。     

Performance,emission and combustion characteristics of CI engine fuelled with diesel and hydrogen

Hydrogen (H₂) is being considered as a primary automotive fuel and as a replacement for conventional fuels. Some of the desirable properties, like high flame velocity, high calorific value motivate us to use hydrogen fuel as a dual fuel mode in diesel engine. In this experiment, hydrogen was inducted in the inlet manifold with intake air. The experiments were conducted on a four stroke, single cylinder, water cooled, direct injection (DI), diesel engine at a speed of 1500 r/min. Hydrogen was stored in a high pressure cylinder and supplied to the inlet manifold through a water-and-air-based flame arrestor. A pressure regulator was used to reduce the cylinder pressure from 140 bar to 2 bar. The hydrogen was inducted with a volume flow rate of 4l pm, 6l pm and 8l pm, respectively by a digital volume flow meter. The engine performance, emission and combustion parameters were analyzed at various flow rates of hydrogen and compared with diesel fuel operation. The brake thermal efficiency (BTE) was increased and brake specific fuel consumption (BSFC) decreased for the hydrogen flow rate of 8l pm as compared to the diesel and lower volume flow rates of hydrogen. The hydrocarbon (HC) and carbon monoxide (CO) were decreased and the oxides of nitrogen (NO_x) increased for higher volume flow rates of hydrogen compared to diesel and lower volume flow rates of hydrogen. The heat release rate and cylinder pressure was increased for higher volume flow rates of hydrogen compared to diesel and lower volume flow rates of hydrogen.     

Steam gasification of biochars derived from pruned apple branch with various pyrolysis temperatures

In this study, the gas production behavior from the steam gasification of the biochar derived from the pruned apple brunch was investigated using a fixed-bed reactor. The optimal biochar obtained at the pyrolysis temperature of 550 °C was gasified under different operating conditions for the hydrogen rich gas production. The experimental results indicated that high reaction temperature and high water flow rate were both beneficial to the hydrogen gas yield, but excess steam had a negative impact contrarily. Besides, the small size particles (0.5–1.0 mm) showed better performance in the hydrogen gas production at the low water flow rates (0.05–0.20 g/min); while the large size particles (1.0–2.8 mm) showed better performance at the high water flow rates (0.25–0.30 g/min). The suitable operating conditions for the gasification of the biochar were determined as the reaction temperature of 850 °C, water flow rate of 0.25 g/min, and particle size of 1.0–2.8 mm.     

Parametric study on the pyrolysis of manure and wood shavings

In this work, a response surface methodology (RSM) was used to study the effects of temperature (A), feed rate (B) and gas flow rate (C) on the liquid yield, char yield and pH of the biocrude oil. Box-Behnken design was chosen and a total number of 15 experimental runs including 3 center runs were generated for the pyrolysis of a mixture of 50 wt.% layer manure and 50 wt.% loblolly pine wood shavings in a 50 mm bubbling fluidized bed reactor. The operational variables were as follows: temperature (400-550 °C), nitrogen gas flow rate (12-24 L/min), and feed rate (160-480 g/h). A second-order regression models were used to predict the responses. The analysis of variance (ANOVA) was performed with Minitab 16 software and the significant effect of the factors and their interaction effects were tested at 95% confidence interval. The biocrude yield was significantly influenced by temperature, feed rate and gas flow rate. Temperature was the only significant factor that influenced the char yield. Maximum biocrude yield (51.1 wt.%) was achieved at 475 °C with a feed rate of 480 g/h and a gas rate of 12 L/min. The lowest char yield (22.6 wt.%) was achieved at 550 °C, 320 g/h and 12 L/min and the biocrude had the highest pH (4.85) at 475 °C, 160 g/h and 24 L/min. The predictive models proposed agreed with the experimental values.     

Experimental study of several types of ground heat exchanger using a steel pile foundation

An experimental study of several types of ground heat exchangers (GHEs) installed in a steel pile foundation, including double-tube, U-tube, and multi-tube GHEs, was carried out at Saga University. Water flows through the heat exchangers and exchanges heat to or from the ground. The performance of GHEs was investigated under actual operation in the cooling mode with flow rates of 2, 4, and 8 l/min. Temperatures of the ground and GHE tube wall were measured to find the temperature distributions according to the depth of the ground and depth of the GHE tube wall. The temperatures of the inlet and outlet of circulated water were also measured to calculate the heat exchange rate. The double-tube had the highest heat exchange rate, followed by the multi-tube and U-tube GHEs. For example, the average heat exchange rate of GHEs over 24 h of continuous operation with a flow rate of 4 l/min was 49.6 W/m for the double-tube, 34.8 W/m for the multi-tube, and 30.4 W/m for the U-tube. An increasing flow rate increased the heat exchange rate of the GHEs. The heat exchange rates increased significantly for flow rate increases from 2 to 4 l/min, but only slightly changed from 4 to 8 l/min.     

Biohydrogen production with utilisation of magnetite nanoparticles embedded in granular activated carbon from coconut shell

This study aims to utilize magnetite nanoparticles (MNP) embedded in granular activated carbon (GAC) originating from coconut shells as microbial support carriers in thermophilic biohydrogen production. MNP can facilitate intracellular electron transportation while providing essential nutrition for microbial growth. Response Surface Methodology (RSM) with a Central Composite Design was used to investigate the simultaneous effect of three variables; Ni:Fe (0.25–0.80), MNP:GAC (0.01–0.03) and type of GAC (GAC-O or GAC-C) on the hydrogen productivity rate (HPR). Biohydrogen content in the biogas to range from 22.25 to 64.71%. The quadratic model was well fitted (R-squared>0.80) with a confidence level higher than 90%. The optimum magnetite GAC was GAC-O as the preferred GAC at Ni:Fe (0.53) and MNP:GAC (0.02), with HPR of 20.33 ± 0.32 ml H₂/L.h. Magnetite GAC exhibited a better biohydrogen productivity rate by 63.99% compared to non-magnetite GAC. The developed magnetite GAC shown a high potential to improve biohydrogen production.     

Effects of biomass,COD and bicarbonate concentrations on fermentative hydrogen production from POME by granulated sludge in a batch culture

Effects of three selected variables viz. biomass concentration, initial chemical oxygen demand (COD) concentration and initial bicarbonate alkalinity (BA) on biological hydrogen production from palm oil mill effluent (POME) using the granulated sludge in batch culture were investigated. The experimental results were analyzed and modeled using a central composite design (CCD) of response surface methodology (RSM). In order to carry out a comprehensive analysis of the biohydrogen production process, indicative parameters namely hydrogen yield (Y_H), specific hydrogen production rate (SHPR), and COD removal efficiency were studied as the process responses. Maximum hydrogen yield (124.5 mmol H₂/g COD_removed) and specific hydrogen production rate (55.42 mmol H₂/g VSS.d) were achieved at COD_in 3000 and 6500 mg/l, MLVSS 4000 and 2000 mg/l, and initial BA 1100 mg CaCO₃/l, respectively.     

Production of hydrogen by Enterobacter aerogenes in an immobilized cell reactor

The production of hydrogen from glucose by using Enterobacter aerogenes ATCC 13048 (E. aerogenes) in an immobilized cell reactor (ICR) was investigated. The effect of several factors, such as the glucose concentration, feed flow rate, and fermentation time were examined. The highest amount of hydrogen (9.44 mmol H₂/g glucose) was obtained at a glucose concentration of 8 g/L, flow rate of 0.5 mL/min, retention time of 24 h and at a temperature of 30 °C. Meanwhile, the highest amount of carbon dioxide (1.68 mmol CO₂/g glucose) was obtained at a glucose concentration of 10 g/L, flow rate of 0.7 mL/min, hydraulic retention time of 24 h and at a temperature of 30 °C. The hydrogen and carbon dioxide production were affected by glucose concentration, hydraulic retention time (HRT) and fermentation time. This study showed that the ICR was a very efficient method for the production of hydrogen and carbon dioxide gases.     

改性西瓜皮生物炭对废水中Pb2+的吸附研究

以西瓜皮为原料制备生物炭（WM）吸附水中的Zn²⁺,再将吸附后的生物炭进行二次热解,制得WM-Zn并用于吸附水中的Pb²⁺。研究表明,WM-Zn对Pb²⁺ 的吸附容量（163.84 mg/g）高于WM的吸附容量（87.64 mg/g）。利用X射线光电子能谱（XPS）、傅里叶变换红外光谱（FTIR）、元素分析（EA）、X射线衍射（XRD）、吸附比表面测试法（BET）和Zeta电位对生物炭进行了表征,发现WM-Zn表面孔结构的扩大和官能团的增多均有助于Pb²⁺ 的去除,WM-Zn对Pb²⁺ 的吸附可归结为官能团络合、静电吸附、物理吸附和沉淀作用。此外,WM吸附Zn²⁺ 和WM-Zn吸附Pb²⁺ 均符合Langmuir等温吸附模型和拟二级动力学模型,表明吸附过程是以单分子层吸附为主的化学吸附。在吸附-解吸循环实验中,WM-Zn在第6次循环中吸附量可达到87.36 mg/g,表明WM-Zn吸附具有良好的可重复性。     

Method for the control of NOx emissions in long-range space travel

The wheat straw, an inedible biomass that can be continuously produced in a space vehicle has been used to produce activated carbon for effective control of NOx emissions from the incineration of wastes. The optimal carbonization temperature of wheat straw was found to be around 600 degrees C when a burnoff of 67% was observed. The BET surface area of the activated carbon produced from the wheat straw reached as high as 300 m2/g. The presence of oxygen in flue gas is essential for effective adsorption of NO by activated carbon. On the contrary, water vapor inhibits the adsorption efficiency of NO. Consequently, water vapor in flue gas should be removed by drying agents before adsorption to ensure high NO adsorption efficiency. All of the NO in the flue gas was removed for more than 2 h by the activated carbons when 10% oxygen was present and the ratio of carbon weight to the flue gas flow rate (W/F) was 30 g min/L, with a contact time of 10.2 s. All of NO was reduced to N2 by the activated carbon at 450 degrees C with a W/F ratio of 15 g min/L and a contact time of 5.1 s. Reduction of the adsorbed NO also regenerated the activated carbon, and the regenerated activated carbon exhibited an improved NO adsorption efficiency. However, the reduction of the adsorbed NO resulted in a loss of carbon which was determined to be about 0.99% of the activated carbon per cycle of regeneration. The sufficiency of the amount of wheat straw in providing the activated carbon based on a six-person crew, such as the mission planned for Mars, has been determined. This novel approach for the control of NOx emissions is sustainable in a closed system such as the case in space travel. It is simple to operate and is functional under microgravity environment.     

A computational design of a magnetic field applied to control magnetic adsorbent used in liquid/gas adsorption processes

Recently in our research studies, ferroferric oxide magnetic micro particles were used as seeds combined with chitosan and activated carbon respectively in a nutrition recovery process for post hemodialysis (HD) and in a mixed-gas adsorbate analysis. Initially, these magnetic adsorbents used in the experiments were all sealed inside a cylinder vessel by molecular sieve filters. However, this design led to a very slow liquid or gas flow rate during adsorption. To increase the flow rate, a novel design applying a nonlinear gradient magnetic field in the reverse direction of liquid or gas flow was proposed in this paper. The objective of the design was to retain the magnetic adsorbent inside the vessel maintaining a high flow rate. The magnetic field inside an infinite solenoid coil was derived using Ampere Circuit Law and the Langevin equation. An equation, showing the relationship between the ampere-turns of the magnetic field and their positions, was outlined in this paper. We finally proved that this equation is suitable for the practical design of a magnetic field with finite length. Thus, this mathematic model could help the development of adsorption device utilizing magnetic particles.     

催化型柴油颗粒捕集器再生性能的试验研究

为探究催化型柴油机颗粒捕集器(catalytic diesel particulate filter,CDPF)的再生性能,自制了CDPF颗粒加载装置,通过模拟气试验平台研究了炭载量、再生温度及气体流量对CDPF再生性能的影响,并对其再生效率、再生效能比、最高温度及最高温度梯度性能指标进行评价。试验结果表明:CDPF再生过程主要有两个阶段,第一个阶段主要发生在250~400℃之间,为低温长时间再生阶段;第二个阶段主要发生在500~600℃之间,为高温短时间再生阶段。当再生温度为350℃、气体流量为200mL/min时,3.2g/L、5.0g/L和7.0g/L 3种炭载量下的最高温度梯度均达到最小,分别为2 737.5℃/m、4 387.5℃/m和3 837.5℃/m。其再生效率在再生温度为250℃时均约为6.0%,而在550℃时均达到85.6%。当炭载量为5.0g/L,再生温度为500℃和550℃,气体流量为300mL/min时,最高温度、最高温度梯度及再生效率均达到最大,再生效能比随气体流量的增大从4.6×10-5 J-1下降到1.8×10-5 J-1。     

Effect of microwave irradiation pretreatment of cow dung compost on bio-hydrogen process from corn stalk by dark fermentation

The bio-hydrogen production potential from corn stalk was significantly affected by microwave irradiation pretreatment of cow dung compost in batch tests. The maximum hydrogen yield of 144.3 ml/g-corn stalk and hydrogen production rate of 3.6 ml/g-corn stalk h⁻¹ were observed using the pretreated compost by microwave radiation of 1.5 min at fixed Na₂CO₃ dosage of 800 mg/l, Fe dosage of 400 mg/l, substrate concentration of 20 g/l, which increased about 99.6% and 85.2% compared with that of the control. The effects of microwave irradiation on microbial characteristics were further discussed by Atomic Force Microscope (AFM), determination of protein content and PCR-DGGE. The four dominant hydrogen-producing strains had been isolated and confirmed to be Bacillus amyloliquefaciens, Bacillus licheniformis, Bacillus subtilis and Enterococcus faecium, respectively. The diversity and symbiosis relations of the mixed bacteria were also observed in fermentation hydrogen production process.