LPG Concentrations Research Articles

Gold sensitized sprayed SnO2 nanostructured film for enhanced LPG sensing

We report LPG sensing of gold (Au)-sensitized SnO2 nanostructured film fabricated by an easy spray pyrolysis deposition method whose surface morphology is confirmed by field-emission scanning electron microscopy and atomic force microscopy images and structure by X-ray diffraction pattern. Energy dispersive X-ray spectrometer analysis has carried out for finding elemental composition. The SnO2 film is uniform and consists of spherical particles of ∼10nm. The highest gas response observed at 780ppm LPG concentration for pristine SnO2 is 28%, at operating temperature 623K, which is greatly improved on Au sensitization up to 57% with 60s rapid response time at 598K operating temperarture. The high gas response is due to electronic effect and catalytic spill-over effect of Au sensitization. The improved sensing mechanism has throughly been explored .

MWCNT Doped ZnO Nanocomposite Thin Film as LPG Sensing

A compound material of multi-walled carbon nanotubes (MWCNTs) coated with ZnO was synthesized at ambient conditions. The X-ray diffraction, UV–visible spectroscopy, scanning electron microscope (SEM) and transmission electron microscopy results confirmed that the existence of ZnO nanoparticles inside the MWCNTs. The gas sensing properties of the material were studied. ZnO-based composites on MWCNTs treated at room temperature shows enhanced performance as sensors, making them suitable for practical applications. Sensor structure showed a better sensing response (S ~61.57) at operating room temperature towards 1500 ppm LPG with an average sensitivity 41.95. Furthermore, the gas sensor responses increased linearly with the increment of the gas concentrations of LPG.

LPG sensing investigation of (Sn-Ti)O2 system based nanocomposite at Room Temperature

Present work reports the synthesis of pure TiO2 and (Sn-Ti)O2 nanocomposite, its characterization and performance asLiquefied Petroleum Gas (LPG) Sensor. Thick films of both the materials were prepared by using screen printing technique. After that these were investigated through SEM. SEM image of pure TiO2 shows that grains are random in shape having pores. The grains observed on the (Sn-Ti)O2 thick-film surface are spherical in shape and more porous than pure TiO2. Further at room temperature, the films were exposed to LPG in a controlled gas chamber and variations in resistance with the concentrations of LPG were observed. The maximum value of average sensitivity for pure TiO2 and (Sn-Ti)O2 thick-film were found 3.0 and 11 respectively for 2 vol.% of LPG. Sensor responses as a function of exposure and response times were also estimated and maximum sensor response for pure TiO2 and (Sn-Ti)O2 thick-film were found 207 and 1040 respectively.

Performance evaluation of LPG desulfurization by adsorption for hydrogen production

The adsorption of sulfur compounds, in commercially available LPG, has been studied using different adsorbents, namely Zeolite, ZnO and house made date pits activated carbon (DP-AC). It was found that the three adsorbents are capable of effectively removing sulfur compounds at different feed sulfur concentrations. The effects of height to diameter aspect ratio of the adsorption column, flow rate of LPG and input sulfur concentrations have been studied. A first order kinetics model has been used to describe the adsorption, and the kinetics constant was found to increase by increasing the flow rate of LPG and decrease by increasing the amount of adsorbent used. The developed model described the system fairly well, and can be used in designing and scaling-up of fixed-bed adsorption columns.

Compositional Modeling for Optimum Design of Water-Alternating CO2-LPG EOR under Complicated Wettability Conditions

The addition of LPG to the CO2stream leads to minimum miscible pressure (MMP) reduction that causes more oil swelling and interfacial tension reduction compared to CO2EOR, resulting in improved oil recovery. Numerical study based on compositional simulation has been performed to examine the injectivity efficiency and transport behavior of water-alternating CO2-LPG EOR. Based on oil, CO2, and LPG prices, optimum LPG concentration and composition were designed for different wettability conditions. Results from this study indicate how injected LPG mole fraction and butane content in LPG affect lowering of interfacial tension. Interfacial tension reduction by supplement of LPG components leads to miscible condition causing more enhanced oil recovery. The maximum enhancement of oil recovery for oil-wet reservoir is 50% which is greater than 22% for water-wet reservoir. According to the result of net present value (NPV) analysis at designated oil, CO2, propane, and butane prices, the optimal injected LPG mole fraction and composition exist for maximum NPV. At the case of maximum NPV for oil-wet reservoir, the LPG fraction is about 25% in which compositions of propane and butane are 37% and 63%, respectively. For water-wet reservoir, the LPG fraction is 20% and compositions of propane and butane are 0% and 100%.

Study of Zn‐Cu Ferrite Nanoparticles for LPG Sensing

Nanostructured zinc-copper mixed ferrite was synthesized using sol-gel method. XRD patterns of different compositions of zinc-copper ferrite, Zn(1−x)CuxFe2O4 (x = 0.0, 0.25, 0.50, 0.75), revealed single phase inverse spinel ferrite in all the samples synthesized. With increasing copper concentration, the crystallite size was found to be increased from 28 nm to 47 nm. The surface morphology of all the samples studied by the Scanning Electron Microscopy there exhibits porous structure of particles throughout the samples. The pellets of the samples are prepared for LPG sensing characteristics. The sensing is carried out at different operating temperatures (200, 225, and 250°C) with the variation of LPG concentrations (0.2, 0.4, and 0.6 vol%). The maximum sensitivity of 55.33% is observed at 250°C operating for the 0.6 vol% LPG.

Zn-doped and undoped SnO2 nanoparticles: A comparative structural, optical and LPG sensing properties study

SnO2 nanoparticles were prepared by the co-precipitation method with SnCl4·5H2O as the starting material and Zn(CH3COO)2·2H2O as the source of dopant. All the materials prepared have been found to be polycrystalline SnO2 possessing tetragonal rutile structure with crystallite sizes in the range 11–25nm. Optical analyses reveal that for the SnO2 nanoparticles, both undoped and Zn-doped, direct transition occurs with the bandgap energies in the range 3.05–3.41eV. Variation in the room temperature resistivity of the SnO2 nanoparticles as a function of dopant concentration has been explained on the basis of two competitive processes: (i) replacement of Sn4+ ion by an added Zn2+ ion, and (ii) ionic compensation of Zn2+ by the formation of oxygen vacancies. Among all the samples examined for LPG sensing, the 1at% Zn-doped sample exhibits fast and maximum response (∼87%) at 300°C for 1vol% concentration of LPG in air.

A comparative study on surface morphological investigations of ferric oxide for LPG and opto-electronic humidity sensors

In the present work nanostructured ferric oxides were synthesized via hydroxide precipitation method without using any surfactant and size selection medium. The surface morphologies and structure of samples were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The structural analysis confirmed the formation of Fe2O3 with α-phase and rhombohedral structure. Optical and thermal properties were investigated by using UV–visible absorption spectroscopy and differential scanning calorimetry (DSC) techniques. Pelletizations of materials were done using hydraulic press and these pellets were investigated with the exposition of liquefied petroleum gas. Variations in resistance of the pellet with time for different concentrations of LPG were recorded at room temperature (27°C). The maximum value of average sensitivity was found ∼5 for 5vol.% of LPG. Our results show that the LPG sensing behavior was inspired by the different kinds of surface morphologies of Fe2O3 and inferred that the spherical porous nanoparticles synthesized via hydroxide precipitation process (S-3) had best response to LPG.

Sn-doped Zinc Oxide thin films for LPG sensors

Sn doped zinc oxide (ZnO:Sn) thin films have been prepared by chemical spray pyrolysis technique using Zn(CH3COO)2 as a precursor solution and SnCl4 as a doping solution respectively. The dopant concentration (Sn/Zn at%) is varied from 0 to 1.5 at%. The structural, morphological, optical and electrical properties of the films are explored and then tested for LPG sensing. The resistivity of the Sn-doped films decreases with the Sn doping up to 0.5 at%, while at a higher doping concentration the disorder produced in the lattice causes an increase in resistivity of the films. Exposure of LPG decreases the resistance of undoped and doped films. The response of the film is measured for both ZnO and ZnO:Sn films at different operating temperature (275-400 0 C) and concentration (vol %) of LPG in air. It is observed that Sn-doped ZnO films are more sensitive to LPG than undoped ZnO film. In this work, maximum response (~88 %) is observed for 0.5 at% ZnO:Sn film for 1 vol% of LPG in air at 300 0 C. Further all the films have shown faster response and recovery times at higher operating temperatures.

Experimental Study on the Effect of Gas Composition Variation on Engine Emissions

The pollutant emissions of a four-stroke spark ignition gas engine generator operating on biogas–LPG blends of varying excess air ratios and LPG concentrations were investigated in this paper. Experiments were carried out at a constant engine speed of 1400 rpm and a constant electric power output of 3.5 kW. The experimental results showed that NOx emissions were elevated at an excess air ratio of around 1.2 as the LPG concentration was increased. CO2 emissions decreased as the excess air ratio and LPG concentration increased, due to lean-burn conditions and LPG combustion. These results demonstrated that the addition of LPG to biogas enabled the effective generation of electricity using a gas engine generator through lean-burn combustion. The adding of LPG of 0%, 5%, and 10% in volume is interchangeable. Mixing inert gas such as N2 and CO2 in the end user side to increase the gas MN, thereby increasing its antiknock tendency, furthermore, the measures such as the installation of closed-loop control engine with oxygen sensor in the exhaust and adjust air-fuel ratio accurately and adjusting engine ignition timing, to adapt the changes in gas composition to ensure that the engine working conditions are not significantly affected, to meet the requirements of natural gas interchangeability.

Experimental investigations on liquefied petroleum gas sensing of Cd(NO 3) 2·(AAm) 4·2H 2O and CdS/polyacrylamide synthesized via frontal polymerization

This paper reports an experimental investigations on comparative assessment of CdS/polyacrylamide and Cd(NO 3) 2·(AAm) 4·2H 2O thick films for LPG sensing at room temperature. For synthesis of nanoparticles of CdS in polymer matrix, we used frontal polymerization of cadmium nitrate acrylamide complex Cd(NO 3) 2 (CH 2 CHCONH 2) 4(H 2O) 2 (CdAAm). According to IR spectroscopy in the spectra of polymeric CdS/AAm, there are absorption bands corresponding to stretching vibrations of OH and NH groups. The absence of absorptions bands of the ν (C C) and δ ( CH) at 1580 and 980 cm −1 confirms the assumption of the C C bonds during polymerization. The formation of CdS nanoparticles was proved by X-ray diffractometry. The diffuse diffraction maxima and line broadening indicate that the sample contains nanoparticles. The crystallite size of the CdS/polyacrylamide was found ∼30 nm. Thick films of these metallopolymers were made by screen printing technique on alumina substrate and these were stabilized for 6 h at 80 °C. Further the films were annealed at 450 °C for 2 h. Silver contacts were made on both sides of the films for signal registration, and these films were used as gas sensing elements. Each film was put inside a gas chamber having a gas inlet and an outlet for measurements of LPG sensing characteristics. Variations in electrical resistance of the films with time for different concentrations of LPG were recorded. More variations in resistance were found for Cd(NO 3) 2·(AAm) 4·2H 2O as comparison to CdS/polyacrylamide. The maximum values of the sensitivities was 1.3 and 3.7 GΩ/min respectively, for CdS/polyacrylamide and Cd(NO 3) 2·(AAm) 4·2H 2O for 5 vol.% of LPG. The reproducibility of the sensor made of Cd(NO 3) 2·(AAm) 4·2H 2O after 1 month for 5 vol.% of LPG was found to be 97%.

Sensing of LPG with nanostructured zinc oxide thin films grown by spray pyrolysis technique

Nanostructured zinc oxide thin films were prepared by spray pyrolysis technique using Zn(NO3)2·6H2O as the precursor solution. The resulting films were investigated by X-ray diffraction and scanning electron microscopy to know crystal structure, size of crystallites and surface morphology. The films have been found to be polycrystalline zinc oxide, possessing hexagonal wurtzite crystal structure and nanocrystallite with grain size of approximately 30–35nm. The LPG sensing performance of the films has been investigated at various concentrations of LPG in air at operating temperatures varying from 225 to 400°C. At 325°C the maximum responses of 46.3% and 48.9% have been observed, respectively, for concentrations of 0.8 and 1vol% of LPG in air (1vol% of LPG in air corresponds to 50% LEL of LPG in air). The recovery time has been found to be less than the response time for all concentrations of LPG. A possible reaction mechanism of LPG sensing has been proposed.

Highly sensitive and selective LPG sensor based on α-Fe2O3 nanorods

The α-Fe2O3 nanorods were successfully synthesized without any templates by calcining the α-FeOOH precursor in air at 300°C for 2h and their LPG sensing characteristics were investigated. The α-FeOOH precursor was prepared through a simple and low cost wet chemical route at low temperature (40°C) using FeSO4·7H2O and CH3COONa as starting materials. The formation of α-FeOOH precursor and its topotactic transformation to α-Fe2O3 upon calcination was confirmed by X-ray diffraction measurement (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) analysis. The α-Fe2O3 nanorods exhibited outstanding gas sensing characteristics such as, higher gas response (∼1746–50ppm LPG at 300°C), extremely rapid response (∼3–4s), relatively slow recovery (∼8–9min), excellent repeatability, good selectivity and lower operating temperature (∼300°C). Furthermore, the α-Fe2O3 nanorods are able to detect up to 5ppm for LPG with reasonable response (∼15) at the operating temperature of 300°C and they can be reliably used to monitor the concentration of LPG over the range (5–60ppm). The experimental results clearly demonstrate the potential of using the α-Fe2O3 nanorods as sensing material in the fabrication of LPG sensors. Plausible LP G sensing mechanism of the α-Fe2O3 nanorods is also discussed.

Fabrication of organogels composed from carbon nanotubes through a supramolecular approach

A new organogelator, N,N′-bis (octadecyl)-L-(1-pyrenebutyric acid)-glutamic diamide (LPG), was designed and its interaction with pristine single-walled carbon nanotubes (SWNTs) in the gel state was investigated. It was found that LPG can form organogels with various kinds of organic solvents. Although SWNT itself is difficult to disperse into organic solvents, it can be well dispersed into LPG gel. The gelation process and the properties of the resulting nanocomposites were found to be closely related to the pyrene group in the gelator. The addition of SWNTs significantly decreased the critical gelation concentration of LPG, depressed the sol to gel transition temperature and prolonged the time required to form a gel. Rheological investigations of LPG organogels showed that the flow of nanocomposites became more resistant to the applied stress upon the incorporation of SWNTs. This happened presumably via effective dispersion of SWNTs into the LPG organogels through π–π interaction between the surface of SWNTs and the pyrene group of LPG. The textures of the nanocomposites were altered from layer structure to intertwined fibers upon the incorporation of SWNTs, which also supported the effective mixing of SWNTs into LPG organogels.

Nature of Dopants and Effects on Sensitivity of SnO2 Based Gas Sensor

In this work, a thick film SnO2 sensor was fabricated on a 1″ × 1″ alumina substrate. It consists of a gas sensitive layer (SnO2) doped with Pd and Pt; a pair of electrodes in array form underneath the gas sensing layers serves as a contact pad for sensor and a common heater element on the backside of the substrate. Alumina substrate (96%) has been used as a substrate for sensor fabrication. The fabricated sensor was tested for varying concentration of LPG and methane in a locally developed test chamber. The response of sensors to varying concentration of LPG and methane was studied at 350°C. The Pd-doped sensor was found to be more sensitive towards LPG and methane.

Sensing mechanism of Pd-doped SnO 2 sensor for LPG detection

In the present work, studies have been made to analyze the sensitivity, response, recovery time and sensing mechanism of Pd-doped thick film SnO 2 sensor for detection of LPG. To achieve this, thick film Pd-doped (0.25 and 1% by weight in available Indium doped SnO 2 thick film paste supplied by ESL, USA) along with an undoped (Indium doped) SnO 2 sensors were fabricated on a 1″ × 1″ alumina substrate. It consists of a gas sensitive layer (doped SnO 2), a pair of electrodes underneath the gas sensing layer serving as a contact pad for sensor. Also, a heater element on the backside of the substrate was printed for generating appropriate operating temperature at the substrate necessary for acquiring gas sensing properties. The sensor doped with 1% palladium showed the maximum sensitivity of 72% at 350 °C for 0.5% concentration of LPG. Possible detailed sensing mechanism of Pd-doped SnO 2 sensor for LPG detection has been proposed.

Gas sensing properties of nano SnO2 based thick films prepared by dip coating method with effect of molarity of PtCl2 solution

Synthesized nanophase SnO2 powder was used as a functional material along with optimized 15 wt% of glass, fired at 550 °C for better adhesion, to fabricate thick films using screen printing on alumina substrate. Their surface was modified by dip coating in platinum chloride solution (PtCl2) of different molarities (0.05–0.2 M). A subsequent thermal treatment to these thick films was carried out at an optimized temperature of 750 °C in air atmosphere. The films were tested for 400 ppm concentration of H2, CO and LPG. Sensors dip coated with 0.15 M solution of PtCl2 show the highest sensitivity towards the test gases which is ten times higher than undoped SnO2 sensors.XRD, EDX and SEM measurements showed that the behavior could be associated with the spatial distribution of the platinum within the tin oxide film. The sensors have fast response time of 10 s to all the three gases with a minimum detection limit of 10 ppm.

Oscillating behaviour of hazardous gas on tin oxide gas sensor: Fourier and wavelet transform analysis

The oscillating behaviour of TGS813 and TGS203S sensors in hazardous gases such as LPG and CO was studied under the oscillating conditions of rectangular wave, applied voltage 5V, and duty ratio as 30s/(30s+20s). It was shown that the oscillating behaviour was obviously different with the two type sensors. The data features were extracted by using Fourier and wavelet transform (WT). There were some very obscure differences among the amplitudes in fast Fourier transform (FFT) under different concentrations of LPG or CO. Further FFT analysis showed that it was difficult to discriminate between 800ppm LPG and 800ppm CO because of very little difference in the frequency content. By comparison, the corresponding coefficient plots in continuous wavelet transform (CWT) were investigated, and the original signal was also decomposed into coarse approximation A1 and five detailed information D5–D1. The results showed that the WT was more appropriate than FFT for the frequency–time problem.

Simulated consumer exposure to dimethyl ether and propane/butane in hairsprays

Synopsis The potential human exposures from use of dimethyl ether (DME) and 'liquefied petroleum gas'(LPG) arising from use in hairsprays have been assessed. DME and LPG concentrations were measured in the 'breathing zone' of an experimental manikin and an 'accompanying child' designed to simulate human use of hairsprays in a domestic situation and in the breathing zone of a 'stylist' and 'customer' under salon conditions. Results were expressed as the 10 min time weighted average in the air (TWA10) and as the peak concentration in the breathing zone of the 'user'. Following a 10s use of hairspray containing 50% DME or 26% LPG, TWA10 values for an adult user in a closed room (volume 21 m(3)) were on average 114 ppm and 73 ppm respectively. The child TWA10 values were 89 ppm (DME) and 80 ppm (LPG). Leaving the door open during spraying did not significantly alter these values. The peak concentrations measured in the user breathing zone were 1577 ppm of DME and 671 ppm of LPG. Simulated salon use of a hairspray gave a calculated value of 55 ppm DME and 88 ppm LPG for the stylist over an 8 h working period.

Miscible Displacements of Reservoir Oil Using Flue Gas

Published in Petroleum Transactions, AIME, Volume 213, 1958, pages 7–10. Summary Miscible phase displacement of oil from reservoirs has been emphasized in the past few years. The reason for this emphasis lies in the high oil recovery attainable by this process. Removal of capillary effects in the reservoir leads to recoveries approaching 100 per cent in the area contacted by the miscible phase. The miscible slug process is one means of obtaining a miscible displacement. Here a band or slug of LPG is injected into the reservoir prior to gas injection. The idea is to maintain the band of LPG "wedged" between the gas and oil phases and thus achieve a miscible phase displacement. A second method for achieving miscibility is through the injection of a gas which is not miscible with the reservoir fluid but which develops a zone of miscibility in the reservoir through mass transfer with the reservoir oil. This mass transfer results in either an enrichment of the lean injected gas by intermediates from the oil or an enrichment of the oil by intermediates from a rich injection gas or one that has been enriched on the surface by LPG addition. We are interested here in discussing the process in which miscibility is developed at the displacement front by the evaporation of intermediates from the oil phase into the gas phase. This process "builds up" its own slug of miscible material at the displacement front and therefore does not require the injection of LPG to obtain miscibility. Each process has its own area of applicability. Generally, the high pressure gas process is applicable only with reservoir fluids which contain a high concentration of intermediates. If the high pressure gas process is technically feasible at pressures less than 4,500 psi, it is probably more desirable economically than the slug process. The slug process has broad applicability in the shallower reservoirs and with reservoir fluids which contain a relatively low concentration of LPG and natural gasoline constituents. This paper deals with some new concepts of the high pressure gas injection process where it is proposed that flue gas can be substituted for hydrocarbon gas without sacrificing our goal of miscibility.