Lab-scale Investigation Research Articles

A Lab-scale Investigation of the Mars Kieffer Model

The Kieffer model is a widely accepted explanation for seasonal modification of the Martian surface by CO2 ice sublimation and the formation of a “zoo” of intriguing surface features. However, the lack of in situ observations and empirical laboratory measurements of Martian winter conditions hampers model validation and refinement. We present the first experiments to investigate all three main stages of the Kieffer model within a single experiment: (i) CO2 condensation on a thick layer of Mars regolith simulant; (ii) sublimation of CO2 ice and plume, spot, and halo formation; and (iii) the resultant formation of surface features. We find that the full Kieffer model is supported on the laboratory scale as (i) CO2 diffuses into the regolith pore spaces and forms a thin overlying conformal layer of translucent ice. When a buried heater is activated, (ii) a plume and dark spot develop as dust is ejected with pressurized gas, and the falling dust creates a bright halo. During plume activity, (iii) thermal stress cracks form in a network similar in morphology to certain types of spiders, dendritic troughs, furrows, and patterned ground in the Martian high south polar latitudes. These cracks appear to form owing to sublimation of CO2 within the substrate, instead of surface scouring. We discuss the potential for this process to be an alternative formation mechanism for “cracked” spider-like morphologies on Mars. Leveraging our laboratory observations, we also provide guidance for future laboratory or in situ investigations of the three stages of the Kieffer model.

Time-dependent damage characteristics of shale induced by fluid–shale interaction: a lab-scale investigation

The shale’s multi-scale mechanical behaviors were investigated to understand the time-dependent damage characteristics induced by shale–fluid interaction. The test results indicate that, as fluid–shale interaction proceeds, the mechanical strength of shale has undergone a weakened to an enhanced process as interaction proceeds, and the size distribution of fragments tends to be more uniform, leading to a positive correlation between the mechanical strength and fractal dimension. Within 2 weeks of fluid–shale interaction show a decreasing trend for the fractal dimension of fragments in post-failure and cause less than 2 mm for the dominant size of fragments. The dominant size increases to greater than 30 mm when the fluid–shale interaction is over 2 weeks. Finally, the correlation dimension associated with ring counts of acoustic emission (AE) at each loading stage is determined in terms of the G-P algorithm to predict the damage degree of shale.

Lab scale investigation on biocoagulant performance to remove organic from tempe liquid waste treatment

Lab scale investigation on biocoagulant performance to remove organic from tempe liquid waste treatment

Novel strategy for efficient energy recovery and pollutant control from sewage sludge and food waste treatment

Considering the high organic matter contents and pollutants in sewage sludge (SS) and food waste (FW), seeking green and effective technology for energy recovery and pollutant control is a big challenge. In this study, we proposed a integrated technology combing SS mass separation by hydrothermal pretreatment, methane production from co-digestion of hydrothermally treated sewage sludge (HSS) centrate and FW, and biochar production from co-pyrolysis of HSS cake and digestate with heavy metal immobilization for synergistic utilization of SS and FW. The results showed that the co-digestion of HSS centrate with FW reduced the NH4+-N concentration and promoted volatile fatty acids conversion, leading to a more robust anaerobic system for better methane generation. Among the co-pyrolysis of HSS cake and digestate, digestate addition improved biochar quality with heavy metals immobilization and toxicity reduction. Following the lab-scale investigation, the pilot-scale verification was successfully performed (except the co-digestion process). The mass and energy balance revealed that the produced methane could supply the whole energy consumption of the integrated system with 26.2 t biochar generation for treating 300 t SS and 120 t FW. This study presents a new strategy and technology validation for synergistic treatment of SS and FW with resource recovery and pollutants control.

Improving cross-axis wind turbine performance: A Lab-scale investigation of rotor size and blades number

Horizontal and vertical-axis wind turbines have long been used to generate electricity in open areas by utilizing horizontal wind flow. Under certain conditions, for example in multi-storey building areas, wind flows not only from horizontal but also vertical directions. Therefore, this research aims to develop a new turbine model known as a cross-axis to capture wind flow from horizontal and vertical directions around multi-storey buildings. Design, production, testing, and performance analysis are carried out in this project. The model is designed with a rotor diameter of 700 mm which has 5 vertical blades and 10 horizontal blades with a total height of 600 mm which is divided into two configurations, upper and lower. Performance analysis was carried out using a wind tunnel in a conditioned laboratory both in loaded and unloaded conditions. The output power of the wind turbine is measured using an electric dynamometer. The no-load test was applied to determine the time required to move from non-rotating to constant rotation at different speeds and horizontal blade angles. Meanwhile, the load test is used to determine the power coefficient at various speeds, horizontal blade pitch angles, and loads. The research results show that the time required to move from a non-rotating speed to a constant speed is influenced by the wind speed and the blade pitch angle. The power coefficient was also observed to be influenced by wind speed, blade pitch angle, and load. Furthermore, the shortest time to reach a constant rotation speed is around 20 seconds at a wind speed of 7.6 m/s and a blade pitch angle of 25°. The maximum power coefficient of the wind turbine was obtained at 5.2% at a wind speed of 7.6 m/s, blade pitch angle of 25°, and tip speed ratio of 0.5.

Experimental Study on Wave Transmission Coefficient of Double Cylindrical Floating Breakwater in a Wave Basin

Floating breakwater is a better alternative than the conventional method. It is an effective coastal engineering unit used to protect coastal regions such as harbours and marinas from erosive waves. It has many other applications such as offshore renewable energy generation, infrastructure preservation, temporary structure, and provides a controlled environment for aquaculture activities. The floating breakwater such as the double cylindrical floating breakwater (DCFB) is claimed to have effective wave attenuation characteristics. A lab scale investigation was done by placing the DCFB in a controlled wave basin in with wave generator to generate wave and wave gauge to quantify the wave transmission coefficient. The wave transmission coefficient represents the effectiveness of the breakwater system in attenuating incoming waves, where an effective breakwater system will result in a low transmission coefficient value. In this study, the DCFB’s effectiveness in terms of wave transmission coefficient was investigated with two different configurations where the spacing between the cylinders of the DCFB units are 0.2 m and 0.6 m respectively. Results show that the configuration of DCFB units with 0.5 m cylinder spacing are more effective in absorbing incoming wave height resulting in lower transmission coefficient. Furthermore, some prospective areas had been identified for future enhancement.

Lab Scale Investigation of Gaseous Emissions, Performance and Stability of an Aviation Turbo-Engine While Running on Biodiesel Based Sustainable Aviation Fuel

The research experimentally examines the viability of biodiesel obtained from pork fat (BP) as a sustainable aviation fuel (SAF) when mixed with kerosene (Ke)—Jet-A aviation fuel + 5% Aeroshell 500 oil. Various blends of biodiesel and kerosene (10, 20, and 30% vol. of BP added in Ke) were subjected to testing in an aviation micro turbo-engine under different operational states: idle, cruise, and maximum power. During the tests, monitoring of engine parameters such as burning temperature, fuel consumption, and thrust force was conducted. The study also encompassed the calculation of crucial performance indicators like burning efficiency, thermal efficiency, and specific consumption for all fuel blends under maximum power conditions. Combustion temperatures ahead of the turbines rise with an increase in biodiesel concentration, particularly in the idle regime, without compromising engine integrity. However, for regimes 2 and 3, the temperature in front of the turbine decreases with rising biodiesel concentration, accompanied by an increase in fuel flow rate. This phenomenon is reflected in the elevated specific consumption. Notably, for regime 3, there is a noticeable rise in specific consumption, starting from S = 0.0264 kg/Nh when the turbo-engine operates solely with Ke, to S = 0.0266 kg/Nh for Ke + 10% BP, S = 0.0269 kg/Nh for Ke + 20% BP, and S = 0.0275 kg/Nh for Ke + 30% BP. Physical–chemical properties of the blends, encompassing density, viscosity, flash point, and calorific power, were determined. Furthermore, elemental analysis and FTIR were used for chemical composition determination. The amount of CO2 produced during the stoichiometric combustion reaction with air showed variations. Initially, when using only Ke, it amounted to 3.12 kg per kilogram of fuel. Upon adding 10% BP, this value decreased to 3.09 kg, further reducing to 3.05 kg with 20% BP. The lowest value was observed with 30% BP, reaching 3.04 kg. Experimental assessments were performed on the Jet Cat P80® micro-turbo-engine, covering aspects such as starting procedures, sudden acceleration, sudden deceleration, and emissions of pollutants (NOx, CO, and SO2) during several engine operational phases. The outcomes reveal that the examined fuel blends exhibited stable engine performance across all tested conditions. This indicates that these blends hold promise as sustainable aviation fuels for micro turbo-engines, presenting benefits in terms of diminished pollution and a more ecologically sound raw material base for fuel production.

Gold recovery from electronic wastes using a solvent extraction/selective back-extraction strategy

ABSTRACT The present lab-scale investigation describes a simple and efficient approach to the selective solvent extraction and recovery of gold, and copper as a by-product, from Waste Printed Circuit Boards (WPCBs) of different brands of used computers. The process comprised of three steps; leaching of scraps in aqua regia, solvent extraction process under optimized conditions, and ultimately selective back-extraction. The analysis of leach solution by inductively coupled plasma revealed, in addition to gold (0.14 wt%), copper (40.0 wt%), tin (11.9 wt%), and Ni (2.3 wt%) were the other main metals in the WPCBs. A solvent extraction procedure using trioctylamine, as extractant, dissolved in kerosene was employed for the extraction of gold as its anionic chloride-complexes from the leach liquor. The parameters affecting this process including hydrochloric acid concentration, equilibrium time, extractant concentration, initial gold concentration in the sample solution, and the aqueous/organic volume ratio were optimized by means of the statistical technique response surface methodology (RSM). Under the optimized extraction conditions, 99.6% of gold and 23.4% of copper were transferred into the organic phase, while the extracted percentage of other metal ions were negligible. Selective back-extraction by the solution 0.1 M NaOH resulted in the selective precipitation of copper, while the raffinate contained just gold ions.

Lab-Scale Investigation of the Integrated Backup/Storage System for Wind Turbines Using Alkaline Electrolyzer

The depletion of fossil fuel sources has encouraged the authorities to use renewable resources such as wind energy to generate electricity. A backup/storage system can improve the performance of wind turbines, due to fluctuations in power demand. The novelty of this study is to utilize a hybrid system for a wind farm, using the excess electricity generated by the wind turbines to produce hydrogen in an alkaline electrolyzer (AEL). The hydrogen storage tank stores the produced hydrogen and provides hydrogen to the proton-exchange membrane fuel cell (PEMFC) to generate electricity once the power demand is higher than the electricity generated by the wind turbines. The goal of this study is to use the wind profile of a region in Iran, namely the Cohen region, to analyze the performance of the suggested integrated system on a micro scale. The output results of this study can be used as a case study for construction in the future, based on the exact specification of NTK300 wind turbines. The results indicate that, with the minimum power supply of 30 kW from the wind turbines on a lab scale, the generated power by the PEMFC will be 1008 W, while the maximum generated hydrogen will be 304 mL/h.

Biochar synthesis from mineral and ash-rich waste biomass, part 2: characterization of biochar and co-pyrolysis mechanism for carbon sequestration

The increase in mineral and ash-rich waste biomass (MWB) generation in emerging economies poses critical environmental problems and bottlenecks the solid waste and wastewater treatment systems. Transforming these MWB such as sewage sludge from wastewater treatment (SSW) to biochar can be a sustainable method for their disposal and resource recovery. However, such biochar has limited applicability due to the relatively low organic content and possibly contaminated nature of SSW. This may be offset through combined pyrolysis with other MWB, which can also support municipal solid waste management. Studies on this MWB co-pyrolysis are lacking and have not yet seen successful long-term implementation. This work is the second part of authors’ research encompassing an analytical and lab-scale investigation of biochar production from MWB through pyrolysis for the case of Chennai city, India. Here, the physicochemical properties of biochar derived from lab-scale co-pyrolysis of SSW with other MWB such as anaerobic digestate from waste to energy plants of food, kitchen or market waste fermentation, and banana peduncles (BP) collected from vegetable markets and their thermolysis mechanism are comprehensively investigated for purpose of carbon sequestration. Also, a novel preliminary investigation of the effect of sample weight (scaling effect) on the analytical pyrolysis of biomass (BP as model substrate) is undertaken to elucidate its impact on the heat of pyrolysis and carbon distribution in resultant biochar. The maximum carbon sequestration potential of the derived biochar types is 0.22 kg CO2 kg−1 biomass. The co-pyrolysis of MWB is exothermic and governed by the synergetic effects of the components in blends with emission profiles following the order CO2 > CH4 > CO > NH3. Co-pyrolysis reduced the heavy metal enrichment in SSW biochar. The derived biochars can be an immediate source of N, P and S in nutrient-deficient acidic soils. The biochar has only up to 4-ring polyaromatic compounds and a residence time longer than 1 h at 500 °C is necessary to improve carbonization. The heat released during analytical pyrolysis of the model biomass and distribution of carbon in the resultant biochar are significantly influenced by scaling effects, drawing attention to the need for a more detailed scaling investigation of biomass pyrolysis.

New insight into fracturing characterization of shale under cyclic soft stimulation: A lab-scale investigation

The cyclic soft stimulation (CSS) is a new method of reservoir reforming for which the mechanism of fracturing crack propagation is ambiguous with regard to the alternating fluid pressure. This study aims to provide a comprehensive understanding of the fracturing mechanical characterizations of CSS under different magnitudes and amplitudes of the alternating fluid pressure. Acoustic emission (AE) is recorded to investigate the damage evolution under CSS based on the b value analysis of AE. Experimental results reveal the difference of pressure in a crack under different cyclic fluid pressure conditions. The AE results show that the maximum radiated energy under CSS tends to be reduced with the increase in the amplitude and magnitude of the alternating fluid pressure. The finishing crucial touch is that the crack extending criterion under CSS is proposed, which combines the injection parameters, the rock properties and in-situ stress. According to the crack extending criterion, the fluctuation fluid pressure causes the reduction of a critical crack extending pressure, and the CSS causes the crack to initiate and propagate under low fluid pressure. Under a higher-value magnitude of alternating fluid pressure, the cyclic times of CSS is less for the crack initiation. In supplement to the crack extending criterion, a distinct relationship between the radiated energy and the cyclic fluid pressure also is established based on the energy dissipation criterion. These new findings provide an insight into the determination of crack extending criterion under CSS for efficiently implementing shale fracturing.

Comparative study for Pb2+ adsorption from simulated wastewater of battery manufacture on activated carbon prepared from rice husk with different activation agents

This study contains a lab-scale investigation into the feasibility of applying an adsorption technique to treat wastewater polluted with lead metal simulated to that exhaust from a battery manufactory. Rice husks have been prepared for use in three forms; natural rice husks without any activation, activated carbon of rice husks pretreated with Sulfuric acid H2SO4, and the other pretreated with Potassium hydroxide KOH. Activated carbon using KOH provided the best condition for the removal of lead than carbon activated using H2SO4 and natural rice husks. The BET surface area and surface morphology by FESEM analysis were characterized. The values of surface area were (20, 561, 722) m2/g for natural rice husk, activated carbon pretreated with sulfuric acid, and potassium hydroxide respectively. The adsorption process was studied using Pb2+ at temperatures of (25-40)o C and for a concentration range of (20-100) mg/l. The maximum removal ratios of lead Pb2+ for natural rice husks and sulfuric acid or hydroxide potassium activation after 1h were 51.21%, 92.3%, and 97.25%, respectively. The maximum adsorption capacity of lead Pb2+ onto natural rice husks, rice husks pretreated with H2SO4 or KOH, and into activated carbons was (37, 86.2 and 94.6) mg/g respectively, at a concentration of 100 ppm and at 25oC. The equilibrium adsorption curves were obtained for Pb2+ and the data was fairly well fitted with Freundlich-isotherm with a confidence level of 0.99. The kinetic of adsorption was studied by using two kinetic models, pseudo first order and pseudo second order. The results showed the rapid increase in the rate of adsorption at the initial until equilibrium achieved. Pseudo second order model was represented the data very well with confidence level 0.99.

Enhanced removal of ammonium from water using sulfonated reed waste biochar-A lab-scale investigation

The removal of excessive ammonium from water is vital for preventing eutrophication of surface water and ensuring drinking water safety. Several studies have explored the use of biochar for removing ammonium from water. However, the efficacy of pristine biochar is generally weak, and various biochar modification approaches have been proposed to enhance adsorption capacity. In this study, biochar obtained from giant reed stalks (300, 500, 700 °C) was modified by sulfonation, and the ammonium adsorption capabilities of both giant reed biochars (RBCs) and sulfonated reed biochars (SRBCs) were assessed. The ammonium adsorption rates of SRBCs were much faster than RBCs, with equilibrium times of ∼2 h and ∼8 h for SRBCs and RBCs, respectively. The Langmuir maximum adsorption capacities of SRBCs were 4.20–5.19 mg N/g for SRBCs, significantly greater than RBCs (1.09–1.92 mg N/g). Physical-chemical characterization methods confirmed the increased levels of carboxylic and sulfonic groups on sulfonated biochar. The reaction of ammonium with these O-containing functional groups was the primary mechanism for the enhancement of ammonium adsorption by SRBCs. To conclude, sulfonation significantly improved the adsorption performance of biochar, suggesting its potential application for ammonium mitigation in water.

Experimental investigation to mitigate aeolian erosion via biocementation employed with a novel ureolytic soil isolate

• A novel soil strain of Pseudogracilibacillus family isolated for biocementation. • Soil properties of Thar desert soil tested on various levels of MICP treatment. • Wind erosion traits of Thar desert soil tested on various levels of MICP treatment. Aeolian ecosystems suffer severe land degradation due to wind erosion. This study presents the erosion mitigation via bio-cementation technique for the soil collected from Jaisalmer region of the Thar Desert of India. Most of the previous studies considered conventional microbe Sporosarcina pasteurii for aeolian erosion mitigation. Alternatively, as the soils containing vegetation are rich in microbial diversity, this study presents isolation and characterisation of a novel urease-positive microbial strain from a soil slope, which is later utilised for the aeolian-erosion mitigation. The desert sand was subjected to biocementation treatment using the isolated microbe and various molar concentrations (M) of cementation solution, ranging from 0.25 M to 1 M. The engineering properties of the biocemented sand such as coefficient of permeability (k), unconfined compressive strength (UCS), and erodibility was investigated. The soil erosion test was conducted in a lab-scale wind tunnel to investigate parameters such as soil mass loss and threshold detachment velocity. The investigation revealed a decrease of one order in the magnitude of the permeability coefficient with 1 M biocementation treatment. A high UCS value of around 1 MPa was observed with a low calcium carbonate content of 1.3% precipitated with 0.5 M cementation solution treatment. The erosion resistance is observed to be maximum with 1 M cementation solution treatment withstanding the maximum wind velocity above 55 km/h. With lab-scale investigation, this study confirms drastic improvement in soil erodibility resistance with biocementation using the isolated microbe and encourages field trial for protecting the desert ecosystem from severe erosion.

Visualizing highly selective electrochemical CO2 reduction on a molecularly dispersed catalyst

Electrochemical CO2 reduction driven by renewable electricity provides a promising strategy for the ambient synthesis of CO. While great efforts were being devoted to developing highly efficient catalysts for electrochemical CO2 reduction reactions (CO2RRs), electrode improvement is another important direction for the real-world application of CO2 conversion. Toward a better understanding on the mechanism of the highly selective CO2RR catalyst on the electrode, an in-situ, high-resolution, and high-speed microscale visualization techniques are applied to observe the generation and detachment of the CO2RR products (CO and H2) on the electrode coated with molecularly dispersed electrocatalyst of methoxy group functionalized nickel phthalocyanine (NiPc-OMe MDE). The catalyst exhibits superb selectivity towards CO formation with Faradic efficiency above 98% from −0.56 V to −0.77 V vs. RHE and approaches 100% at −0.65 V vs. RHE. The CO and H2 bubbles are observed in CO2 and Ar atmosphere, which provide direct evidence for the high selectivity of NiPc-OMe MDE. Additionally, the number of reaction regions and their gas production rate increase as the applied cathodic potential increases. The in-situ optical visualization method employed in the electrochemical test system contributes to better electrode design of the CO2 electrolyzer to accelerate the transition from lab-scale investigation to industrialization.

Photocatalytic water splitting for solving energy crisis: Myth, Fact or Busted?

• Practicality of photocatalytic water splitting is assessed from various aspects. • Employments of unrealistic labscale investigation are pointed out. • Intrinsic limitations of photocatalytic water splitting are summarized. • Energy and economy analysis of photocatalytic water splitting are performed. • H 2 energy generation from photocatalytic water splitting is not industrially viable. Reaping hydrogen energy by utilising eternal sunlight offers a good fit to the theme of popularly-hype sustainable and carbon-free energy future. Contrary to that belief, this review unveils the impracticality of photocatalytic water splitting (solar energy for H 2 energy) to fuel global advancement. Despite some success with idealized laboratory-scale studies, the past research works also mutually evinced an extreme low solar-to-hydrogen efficiency (STH < 1.0%). Hitherto, multifarious endeavours, such as advanced reactor design, facilities to eliminate diffusional restrictions, advanced photocatalyst design and an inclusion of sacrificial reagents, are incapable to raise STH efficiency to the practical threshold of STH > 10%. Regardless of the epitome and modifications of photocatalysts, the intrinsic limitation of charges recombination remains a sturdy obstacle, leading to an appreciable energy losses and low STH. For consequential solar-driven H 2 production, the bandgap energy of photocatalyst employed must stay below 2.36 eV. Meanwhile, most photocatalysts are capped by the theoretical maximum STH of 18%, even with the assumption of 100% quantum yield of corresponding spectrum. Nonetheless, the theoretical maximum STH is unattainable at this juncture due to the inevitable solar energy dissipation associated to the scattering effects of reactor and water. From economy standpoint, H 2 production via photocatalytic water splitting is pricey at 10.36 $/kg with exorbitant upfront costs, which is far beyond the practicable price range of 2 – 4 $/kg. In conclusion, we assert that the H 2 production from solar-driven photocatalytic water splitting is an industrially impractical pathway for solar energy harnessing, despite technically-feasible.

Characterization of Nutrients and Pilot Biofertilizer Production from Food Waste and Dairy Manure Digestates

HighlightsN, P, Ca, and Mg were mainly localized to fine digestate solids (0.45 µm to 1 mm).50% to 60% of NH4+-N was found in digestate solids between 0.45 and 75 µm.K and Na were mainly transferred to the ultrafiltration permeate (&amp;lt;0.45 µm).Mixing of coarse and fine solids can optimize nutrient and salt ratios in products.Abstract. Food waste and dairy manure digestates from commercial digesters were characterized in the lab for particle and nutrient distributions before pilot-scale processing (vibratory screen, ultrafiltration, sun drying) to produce solid and liquid biofertilizer products. Experimental results showed that the elemental compositions of the two digestates were different but shared similarities. The coarse solids of both digestates had lower concentrations of nutrients than the liquid fractions, which contained most of the K and Na. The dairy manure digestate had a higher amount of fine solids between 0.4 and 75 µm than the food waste digestate, but the majority of TKN was contained in the fine solids of both digestates. An optimization analysis concluded that optimal combinations of digestate fractions included over 70% coarse solids to obtain desired nutrient and salt ratios. The solid and liquid fertilizer products derived from the pilot-scale processing were similar to those expected from the lab-scale investigation. Keywords: Biofertilizer formulation, Digestate, Nutrient distribution, Pilot-scale processing, Ultrafiltration, Value-added products.

Lab Scale Investigation of the Hybrid Cogeneration of Wind Power and Fuel Cell and Study of Technical Analysis

One of the recent familiar renewable energy sources is wind. Often, at peak times, it is not possible to use the power of the wind. Thus, it is essential to have backup power or a storage system. In the present work, we presented a hybrid system for a wind farm so that reliable power can be provided. This hybrid system includes four major parts: electrolyzer, wind turbine, fuel cell, and hydrogen storage. The system mechanism works as follows: the excess electricity generated wind turbines in demand periods is conducted to an oxygen and hydrogen generator system. Specific tanks are used for comprising and storing oxygen and hydrogen. For electricity production at peak times, it is required to introduce hydrogen to a fuel cell unit (in cases that wind power-generated electricity is less than demand). We also investigated the electricity generation by PEM fuel cell and hydrogen generation rate by alkaline electrolysis. The power generated by the fuel cell was 1008 MW and the maximum hydrogen generated by the system per hour average was 304ml. We conducted a case study for the proposed system in the Kouhin area following constructing the prototype.

Kinetic Characterization of Tar Reforming on Commercial Ni-Catalyst Pellets Used for In Situ Syngas Cleaning in Biomass Gasification: Experiments and Simulations under Process Conditions.

Filtering-catalytic candles, filled with an annular packed-bed of commercial Ni-catalyst pellets (∼600 g), were successfully tested for in situ syngas cleaning in a fluidized-bed biomass steam gasifier [Fuel Process. Technol.2019, 191, 44−53, DOI: 10.1016/j.fuproc.2019.03.018]. Those tests enabled the macroscopic evaluation of gasification and gas cleaning as a whole, requiring a more specific assessment of the catalyst performance inside the filter candle. To this end, steam reforming tests of tar key compounds (naphthalene and toluene; thiophene in traces to observe sulfur deactivation) were performed with a laboratory-scale packed-bed reactor containing the same catalyst pellets (<7 g). A lumped kinetics was derived, referred to a pseudocomponent representing tars. This was then validated by simulation of the annular catalytic packed bed inside the filter candle, obtaining numerical results in fair agreement with gasifier outputs. As a result, the lab-scale investigation with a small amount of catalyst provides reliable predictions of tar catalytic reforming in industrial-scale filtering-catalytic candles.

Ammonia removal from wastewater by air stripping and recovery struvite and calcium sulphate precipitations from anesthetic gases manufacturing wastewater

Anesthetic gas plant wastewater (AGPW) contains high concentrations of ammonia (NH3-N) and sulphate ions, which is known to results in severe environmental pollution in aquatic ecosystems without treatment. In the first stage of this study, a lab-scale investigation was done to improve removal of ammonia from AGPW by air stripping and struvite (or MAP: magnesium ammonium phosphate) precipitation processes, separately. The main operating parameters such as pH, air flow rate (L/min) and operating time were optimized for air stripping. The theoretical amount of removed ammonia via the air stripping process was calculated. The NH3-N removal efficiency reached 94 % at pH 12. On the other hand, the optimum ratio of [Mg2+]: [NH4+]: [PO43−] was determined to be 1:1.1:1.8 for the struvite precipitation. The concentration of NH3-N was reduced from 10,600 to 1680 mg/L at pH 8.0 and the corresponding removal efficiency was 84 % at optimum ration of MAP. The solution remained after the struvite precipitation was reacted with Ca(OH)2 at pH values in the range 10–13 for removal of sulphate in the second stage. The removal efficiencies at the optimum conditions were 98 % for sulphate, 31 % for COD and 20 % for TOC. Air stripping process and struvite precipitation could be considered an effective technology for removal and recovery of ammonia or ammonium ion (NH4+-N) from the AGPW. Surface analyses of the precipitated samples were characterized by SEM and XRD.