Blue Flame Research Articles

Kinetic nature of blue flames in the autoignition of methane

Kinetic calculations within the framework of detailed reaction mechanisms showed that the blue flames observed during autoignition of methane in an internal combustion engine are combined cool-blue flames. In the course of methane oxidation, methyl hydroperoxide CH3O2H and hydrogen peroxide H2O2 appear and accumulate almost simultaneously. The partial decomposition of these species yields a hydroxyl OH concentration peak, thereby giving rise to a local acceleration of the oxidation reaction, accompanied by luminescence. Kinetic curves for the main products were obtained and the boundaries of cool-blue flames were determined, which turned out to be in satisfactory agreement with the experimental data.

Flammability Limit and Flame Visualization of Gaseous Fuel Combustion Inside Meso-scale Combustor with Different Thermal Conductivity

This study experimentally investigated effect of thermal conductivity on the combustioncharacteristics of gaseous fuel inside a meso-scale combustor. Combustion characteristics that wereobserved in this research include flame visualization and flammability limit. Quartz glass, stainlesssteel and copper tubes with inner diameters of 3.5 mm were used as combustors. Stainless steel wiremesh was inserted inside meso-scale combustor as a flame holder. Liquid petroleum gas (LPG),which is common fuel use by Indonesian people, was used as a gaseous fuel. A stable blue flame wasestablished inside meso-scale combustor at the downstream of wire mesh for all combustor withdifferent thermal conductivity. Furthermore, flame color is blue for combustion of fuel lean orstoichiometric mixture, and blue-green for combustion of fuel rich mixture. Meso-scale combustorwith the highest thermal conductivity has the narrowest flame cross section area, especially at lowerreactant velocity. Vice versa, this combustor has the widest flammability limit, mainly at the higherreactant velocity.

The Woodstove

The Woodstove Jennifer Grotz (bio) The woodstove is banked to last the night,its slim legs, like an elegant dog’s, stand obedientlyon the tile floor while in its belly a muffled tumultroars and cries like wind keening through the hemlocks. Human nature to sleep by fire, and human natureto be sleepless by it, too. I get up to watchthe blue flames finger soft chambers in the woodwhile the coals swell with scintillating breaths. What made Rousseau once observe that dogs will notbuild fires? (And further, that in the pleasing warmthof a fire already started, they will not add wood?)What is it to be human? to forge connection, to make interpretations of fire and contain themin a little iron stove? And what is it to be fire?To burn with indifference, to consumethe skin of the arm as easily as the bark of a log. Sleepy warmth begins to fill the room in whichlife wants to live and fire wants to burn,the room which in the morningwill hold a fire changed to cooling ash. Outside, smoke escapes and for an instantmirrors nature, too, the way falling snowreveals the wind’s mind, and change of mind,before world and mind grow inscrutable again. (2004, Volume 25.1-2) [End Page 161] Jennifer Grotz Jennifer Grotz is the author of three books of poetry, including The Window Left Open (Graywolf Press 2016). She is the translator of Psalms of All My Days, from the French poet Patrice de La Tour du Pin (Carnegie Mellon University Press, 2014), and of Rochester Knockings, a novel by the Tunisian author Hubert Haddad (Open Letter, 2015). She teaches poetry and translation at the University of Rochester and also serves as the director of the Bread Loaf Translators’ Conference. Copyright © 2014 Middlebury College Publications

EXPERIMENTAL STUDIES OF BIOGAS PRODUCTION FROM FEEDSTOCK OF COW DUNG

The recent price rise and scarcity of fuels, has stimulated a trend towards the use of alternative energy sources like solar, wind, geothermal, etc. The global energy crisis has generated interest in the use of animal waste as a substitute to fossil fuel for biogas generation. Two treatments were set up consisting of: A. 6kg of cow dung in 13litres of water and B. 6kg of cow dung mixed with 0.5kg of food waste and 0.5kg of paper all in 13litres of water. The retention period was sixty days. Results obtained show that on the average treatment A generated 14.29grams (0.0119 m 3 ) and treatment B generated 15grams (0.0125m 3 ) of combustible gas per day. It was also observed that treatment B started the generation of methane on day sixteen while experiment A started on day twenty two. Ignition test conducted on the biogas generated produced luminous blue flame. Also gas analysis was carried out to know the percentage composition of each constituent in the generated biogas. It was discovered that the combustible biogas has a methane content of 60%.

Effects of Processing on the Proximate Components and Amino Acid Profile of Bauhinia Monandra (Kurz) Seed

Three (3) methods of processing were adopted to investigate the effects of processing on the nutritional value of Bauhinia monandra (Kurz) seeds. These processing methods were boiling (in water), toasting and soaking. The raw Bauhinia monandra seed sample were boiled with tap water in seed to water ratio of 1:10 w/v at the rate of 5kg:10 litres in a 15litres metal cooking pot for 10, 20, 30 and 40 minutes respectively and sundried to constant weight and milled before being taken to the laboratory for analysis. Toasting was done for 10, 20, 30 and 40 minutes respectively using a hot open pan and heated with fire from a stove burning with blue flame. The seeds were stirred constantly to prevent charring. The seeds were cooled and milled. The last processing method involved the soaking of the raw Bauhinia seed in a bowl containing seed to water ratio of 1:10 (w/v) at the rate of 5kg to 10litres which completely submerged the seeds in tap water at room temperature (30+2oC) and for 24, 48, 72 and 96 hours respectively and sun-dried to constant weight. The seed samples were then milled. The proximate composition and amino acid contents of the milled representative samples of the raw seed and three processed seed sample (boiled, roasted and soaked) were determined in the laboratory according to AOAC (1980) procedure (moisture content, ash, lipids, crude fibre (CF) and nitrogen few extract (NFE) while the nitrogen/crude protein was determined by the method of Pearsons’ (1976). the total amino acid composition was determined by the method described by Spackman et al (1958). Results obtained indicated that processing methods had significant influence on the proximate composition of Bauhinia monandra (Kurz) seeds. Bauhinia seeds processed by soaking in tap water retained more of its nutrient than seeds processed by other means. DOI: 10.5901/ajis.2013.v2n12p144

English

The effect of the geometric parameters and jet dynamics of the port array inverse diffusion flame (IDF) burner on the flame characteristics were investigated experimentally usingliquefied petroleum gas (LPG) fuel. The geometric parameters are the central air flow area, the fuel jets flow area, the number of the fuel jets and the radius of the pitch circle around which the fuel ports are arranged. The jet dynamics are the air and the fuel flow rates and their momentum flux. Three burners were used for this purpose. The analysis of the results of the IDF jet dynamics showed that two flame fronts formed in the entrainment zone of the IDF, one of them in the co-flowing jet formed by the fuel and the central air jet and the other is in the peripheral submerged jet formed by the fuel jets and the ambient air. Beyond the neck, the central air jet, the fuel jets and the two flame fronts flow as one flame torch. At high air, Reynolds number and low fuel Reynolds number, corresponding to the primary equivalence ratios near unity, the IDF produced by the burner of pitch circle radius 10 mm are short blue color sootless flames. As the air Reynolds number was gradually decreased to a low value corresponding to a primary equivalence ratio 4.5, the flame was changed to yellow diffusion flame with high soot concentrations. The results also showed that the flame characteristics were highly affected by the number of the fuel ports. The flame became more bluish and shorter as the number of the fuel ports increases to 36 ports.   Key words:  Inverse diffusion flame (IDF), diffusion flame, burner configuration.

Experimental study on the structure of opposed flow gaseous diffusion flames doped with n-decane

The destruction of n-decane is investigated with a perturbative approach by adding hundreds of ppm to the fuel stream of two gaseous counterflow diffusion flames at atmospheric pressure: a blue methane flame and an incipiently sooting ethylene flame that offer distinct reacting environments. The detailed chemical structure of the flames including the products of n-decane consumption is determined using a microprobe gas sampling technique followed by GC/MS analysis. Experimentally, principal products of n-decane destruction are C2–C9 linear alpha-olefins that are found at ever increasing concentrations with decreasing carbon number, starting with 1-nonene all the way to propene and ethylene, the most abundant products. Successive fragmentation steps of the n-decane primary products lead to the formation of C2–C5 dienes and other hydrocarbons with multiple unsaturated bonds. The consumption rate of n-decane is more abrupt in the methane flame as compared to the gentler decay observed in the ethylene flame. The addition of n-decane in the ethylene flame does not contribute to the formation of soot precursors such as aromatic compounds because the pool of C2–C4 fragments of the baseline flame, playing a key role in aromatic growth, is only marginally affected by n-decane addition. The comprehensive database of stable species of the experimental component of the study is tested by a comparison with the results of modeling the flames using two semi-detailed chemical kinetic mechanisms, Ranzi-mech and JetSurF. Shortcomings of these mechanisms are highlighted for different classes of compounds by comparison of the model results with the experimental data leaving room for future improvements in their formulation.

Effects of particle size distributions on flame propagation mechanism during octadecanol dust explosions

To reveal the effects of particle size distributions on flame propagation mechanism during octadecanol dust explosions clearly, the flame propagation through dust clouds with three different particle size distributions in an open space were recorded using an approach combined by high-speed photography and band-pass filter. From the direct light emission photographs and CH emission photographs, it has been demonstrated in the experiments that the flame front structures were changed as varying the particle size distributions. Flame propagated in the dust cloud with a smaller particle size was characterized by a regular shape and spatially continuous combustion zone structure, which was similar to the premixed gas explosions. On the contrary, when flame propagated through the dust cloud with a larger particle size, discrete blue luminous spots appeared surrounding the yellow luminous zone. Further increase in diameter resulted mostly in the appearance of blue spot flames and the disappearance of yellow luminous zone in the flame propagation process. Additionally, a simple mathematical model was developed to determine the critical particle size to illustrate the different flame propagation mechanisms in octadecanol dust explosions.

PRODUKSI BIOGAS MENGGUNAKAN CAIRAN ISI RUMEN SAPI DENGAN LIMBAH CAIR TEMPE

This study aimed to determine the effect of ratio of liquid cow contents with tempeh wastewater and fermentation time on biogas production. The research was conducted using a completely randomized design (CRD) with 7 point ratio variation cows rumen fluid contents with liquid wastewater tempe (0:100, 5:95, 10:90, 15:85, 20:80, 25:75 and 100: ) and fermentation time consisted of 12, 24, 36, 48, 60, 72, 84 and 96 hours . Each treatment was repeated twice. From the results obtained it turns out the highest content of biogas at a ratio of biogas yield of 2894,35 mg/L. Which produces biogas fermentation time the highest yield for 84 hours. Positive test the presence of mhetane in the biogas shown with the blue flame in the flame test.

Formation of Lean Premixed Surface Flame Using Porous Baffle Plate and Flame Holder

A lean premixed surface flame has many advantages including low CO(Carbon Monoxide) and NOx(Nitrogen Oxide) emission and applicability of a small combustion volume leading to compact design. These advantages make it applicable to burner for condensing boilers with high thermal efficiency. Moreover recent severe regulation of global warming gas favored a lean premixed surface flame in development of a condensing boiler burner. This study focused on emission characteristics of lean premixed flame and the effect of flow distribution on flame stability of a surface flame in a cylindrical porous metal plate burner. For conceptual design of surface flame burner, the numerical calculation of a flow pattern inside the burner was performed and the calculated data were used for design of the burner system including the baffle plate and flame holder. The results show that the surface and stable premixed flame can be generated by implementing the proper baffle plate and flame holder. The surface cylindrical flame mode is changed into green flame, yellow radiation flame, blue flame and blow off with decreasing equivalence ratio. The blue flame has a wide stability region in the stability curve and showed the lowest CO and NOx emission at low equivalence ratio. And CO decreased as the mixture ratio became leaner but NOx showed almost the same emission level. For stability of a surface cylindrical flame, it was found to be very important to select the proper distribution of holes in a baffle plate and install the flame holder to prevent blow off at the rim of the cylindrical burner. NOx was measured below 6 ppm (0% oxygen base) from equivalence ratios 0.706 to 0.769 through the proper design of baffle plate and flame holder. CO which is a very important emission index in residential gas boiler was observed below 49.1ppm under the same equivalence ratio range.

Modified Stove Burner for Biogas

The study focused on modifying a Liquefied Petroleum Gas (LPG) stove burner to suit for Biogas fuel. Further, it intends to package Biogas technology such that it will be utilized at house hold level. This is to offer an alternative fuel source to various users of LPG which is very expenses nowadays. Also, this is in response to the problem raised by the farmer’s Biogas producer that only a part of the cooking burner can burn and release heat and most of the released heat consumed by heating the surplus methane. Biogas producers used (LPG) burner however, LPG is different from Biogas composition, and when burners designed for LPG gas will be used, poor flame produced. Also, the technology’s goal is to showcase Biogas stove burner with good combustion in the atmospheric form utilizing hog waste. The technology utilized LPG cooking burner (two burners) which was modified to fit Biogas burner in atmospheric form. The modification is composed of four parts, nuzzle, air regulation parts, injector and head as similar to a LPG cooking burner, but differ in gadgets. Five trials were done to test the performance of the burner particularly on the length of the flame, color and the pressure. The modified LPG Stove Burner produced blue flame in three layers. No flu gas is coming out from the burner thus fire health and environment hazards minimize. Keywords - Biogas Technology, experimental research, Ilocos Sur, Philippines

Chemical effects of 1,2,4-trimethyl benzene addition in counterflow gaseous diffusion flames

The structure of gaseous counterflow diffusion flames perturbed with the addition of hundreds of ppm of prevaporized 1,2,4-trimethyl benzene (TMB) is studied in two distinct flame environments: a blue methane flame and an incipiently sooting ethylene flame. The two flames provide well defined temperature-time histories and chemical environments to investigate the behavior of complex fuels and complement other reacting environments lacking the coupling of kinetics and transport that is typical of flame environments. Profiles of critical pyrolysis products and of some stable soot precursors are determined from GC/MS analysis of gas samples extracted from the flames and compared with results from the OPPDIFF model using a semi-detailed chemical mechanism. Experimentally, because of the presence of aliphatic fragments, TMB reactivity is enhanced in these flames with the onset of TMB decay beginning at relatively modest temperatures, on the order of 800K. The dominant path to stable species is driven by H radical attack. It leads in sequence to xylenes, toluene (through benzyl radical) and benzene formation. This enhanced reactivity is captured reasonably well by the model in the methane flame, but not in the ethylene flame, in the presence of a richer, more complex mixture. The model does not reproduce accurately the pathway yielding C3 and some C4 species from TMB cracking. Aromatic ring opening is the bottleneck in the TMB cracking process in the methane flame but not in the ethylene one. Indene, an important soot precursor for monoaromatic fuels since the second aromatic ring formation is considered to be a bottleneck in the process, is measured in the ethylene flame in poor agreement with the model predictions. The dataset presented here and available supplemental data online may help identifying improvements to the chemical kinetic mechanism of this reference fuel.

The structure of toluene-doped counterflow gaseous diffusion flames

The structure of gaseous counterflow diffusion flames perturbed with the addition of hundreds of ppm of prevaporized toluene is studied in two distinct flame environments: a blue methane flame stabilized on the fuel side of the gas stagnation plane and an incipiently sooting ethylene flame stabilized on the oxidizer side. The goal is to provide a well-defined testbed in terms of temperature–time history, major species and part of the radical pool, for the examination of reference fuels that are critical components of practical fuel blends. Gas samples are extracted from the flame with fused silica microprobes for subsequent GC/MS analysis and thermocouples and thin filament pyrometry are used to characterize the temperature field. Profiles of critical toluene pyrolysis products and stable soot precursors are compared with computational models using two semi-detailed chemical mechanisms. Results show that in the methane flame some oxygen containing radicals like O and OH are contributing early on to the toluene destruction path. In the incipiently sooting ethylene flame, the primary attack is from H alone. This finding confirms the different challenges that such flames pose to the validation of a chemical kinetic mechanism. The onset of toluene decay in these flames begins at relatively modest temperatures, on the order of 800K. This reactivity is captured reasonably well by both chemical mechanisms in the methane flame, in the absence of reactants larger than C2, but not so in the ethylene flame, in the presence of a richer, more complex mixture. The aromatic ring opening mechanisms are not adequately modeled in either case. This discrepancy has implications for the modeling of practically relevant fuel blends with both aliphatic and aromatic compounds. The dominant species larger than toluene in the doped methane flame is ethylbenzene, which at least one of the mechanisms reproduces quite well. The largest measured species in the incipiently sooting flame is indene, whose concentration increase due to toluene addition is properly captured by one of the models. The experimental dataset reported here may help identifying future improvements to chemical kinetic mechanisms and complement other reactor datasets lacking the coupling of kinetics and transport of flame environments.

Characterization of low- and high-temperature oxidation processes under non-premixed diesel-engine-like conditions

Low- and high-temperature oxidation processes, including thermal auto-ignition under diesel-engine-like conditions (non-premixed mixtures), have been investigated. A special combustion chamber, characterized by constant volume and adiabatic conditions, has been used as an engine simulator. The investigated processes are very complex in nature, and depend significantly on the temperature and pressure. There are five characteristic regions of the process characterized by different delay times, reaction rates and number of recognizable oxidation reactions: region 1 corresponds to processes occurring at low initial pressures over a wide range of initial temperatures; region 2 corresponds to low initial temperatures over a wide range of initial pressures; region 3 corresponds to middle pressures and higher temperatures; region 4 corresponds to middle temperatures and higher pressures; and region 5 corresponds to high initial pressures and high temperatures. by analogy to a negative temperature coefficient (as discussed in the literature), a positive pressure coefficient has been introduced here. This indicates that in the selected range of pressures, the delay time of low-temperature oxidation processes is the shortest, and the rate of these reactions is the highest. Further increases in the pressure behind the positive pressure coefficient range increase the delay time and decrease the reaction rate. The positive pressure coefficient has been observed at lower temperatures (mostly corresponding to cool-flame reactions and transitions to blue flames). Generally, the ignition delay time reduces with increasing chamber temperature and pressure.

Research on the Flame Spread Characteristics of Safety Diesel Microemulsion

The paper studies the flame spread characteristics of the diesel with safety performance by schlieren technology. The flame of fire spreading of the diesel includes flash fire flame which is blue and main flame which is orange. The main flame spread forward in the reciprocating and pulsatile pattern, while the flash fire flame spread with the level discontinuous pulsatile pattern. The water content in the diesel has notable restriction effect on the speed of the flame spreading, which is decreased with the increasing of the water content. But the micro-emulsified diesel can’t effectively restrain the spread speed when water content is below 3%. The microemulsified diesel whose water content being in the range of 3%~12% could be used in engine.

Simulation of Microgravity Diffusion Flames Using Sub-Atmospheric Pressures

Ethylene/air laminar diffusion flames were studied at sub-atmospheric pressures to simulate a non-buoyant environment and at super-atmospheric pressures for comparison, at fuel flow rates of 0.48 mg/s and 1.16 mg/s. Flame properties including flame geometry, soot formation and temperature field of the flames were studied. Overall, luminous flame height decreased with decreasing pressure to the point of visible luminosity disappearance, resulting in blue flames at a near vacuum. Flame width increased with decreasing pressure until the flame was almost spherical. Soot formation was also found to decrease with decreasing pressure and existed at very negligible concentrations in a near vacuum. Subatmospheric peak soot volume fractions ranged from about 0.1 ppm to 0.93 ppm at 0.48 mg/s, whereas at 1.16 mg/s, peak soot volume fractions were substantially higher. At subatmospheric pressures, higher fuel flow rates produced flames with higher soot concentrations. Soot production was restricted to an annular region with this annular region shifting closer to the flame centerline with increasing height from the burner. At locations about halfway between the burner rim and the flame tip, soot volume fraction decreased with increasing radial distance from the flame centerline. These results are consistent for both high and low pressure flames. The annular soot formation region was also located further from the flame centerline for the higher flow rate flames because of the difference in luminous flame shape. At 0.48 mg/s, the fraction of carbon in the fuel converted into soot was between 0.1 % and 1.2 % in the sub-atmospheric pressure range, from 0.2 atm to 1 atm.

헵탄 풀화재 화염안정성에 관한 산화제 유속 및 농도 효과

풀화재에서 화염진동은 주위공기와의 밀도차에 의한 부력효과에 기인하여 주로 발생한다. 본 연구에서는 부력이 지배적인 풀화재의 불안전성에 대하여 산화제유속의 효과를 검토하기 위해 컵버너 실험을 수행하였다. 실험결과는 진동주파수가 산화제의 유속이 증가함에 따라 감소함을 보인다. 무차원 변수로 표현되는 주파수와 부력의 관계로 도시하였을 때 다양한 속도스케일을 사용할 수 있었지만, 연료와 산화제의 유속차로 정의되는 특성속도인 경우에 정지되어 있는 공기중에서의 풀화재 진동과 일치하는 관계식을 얻을 수 있었다. 이러한 사실은 부력이 지배적인 화염에서 불안전성의 원인은 전단면에서의 Kelvin-Helmholtz 불안전성이 주된 기구라는 것을 증명해준다. 산화제의 농도를 변화시켰을 경우에는 산화제의 불활성기체의 농도가 증가할수록 청염의 길이가 길어지고 컵버너 끝단으로부터 부상되는 것이 관찰된다. 또한 진동주파수는 희석율과는 특정한 관계를 보이지 않는데 이는 국부적 화염구조와 연관성을 가지기 때문으로 판단된다.

Effects of soot formation on shape of a nonpremixed laminar flame established in a shear boundary layer in microgravity

A numerical study was performed to give a quantitative description of a heavily sooting, nonpremixed laminar flame established in a shear boundary layer in microgravity. Controlling mechanisms of three dimensional flow, combustion, soot and radiation are coupled. Soot volume fraction were predicted by using three approaches, referred respectively to as the fuel, acetylene and PAH inception models. It is found that the PAH inception model, which is based on the formation of two and three-ringed aromatic species, reproduces correctly the experimental data from a laminar ethylene diffusion flame. The PAH inception model serves later to better understand flame quenching, flame stand-off distance and soot formation as a function of the dimensionless volume coefficient, defined as Cq = VF/Vox where VF is the fuel injection velocity, and Vox air stream velocity. The present experiments showed that a blue unstable flame, negligible radiative feedback, may change to a yellow stable flame, significant radiative loss with an increase of Cq; this experimental trend was numerically reproduced. The flame quenching occurs at the trailing edge due to radiative heat loss which is significantly amplified by increasing VF or decreasing Vox, favouring soot formation. Along a semi-infinite fuel zone, the ratio, df/db, where df is the flame standoff distance, and db the boundary layer thickness, converges towards a constant value of 1.2, while soot resides always within the boundary layer far away from the flame sheet.

Oxidation and combustion mechanisms of paraffin hydrocarbons: Transfer from C1-C7 to C8H18, C9H20, and C10H22

At the present time, detailed kinetic mechanisms (DKMs) for higher hydrocarbons, which include hundreds of particles and thousands of reactions, are proposed. These DKMs have a number of undoubted advantages because they aspire to description of a wide class of phenomena. However, their application, e.g., for modeling of turbulent combustion, is difficult due to their extreme inconvenience. In addition, they are limited to a certain degree and cannot be considered to be comprehensive. As an alternative to such DKMs, we construct no maximum mechanism in this work, but an optimum mechanism of high- and low-temperature oxidation and combustion of normal paraffin hydrocarbons. This mechanism, in accordance with the previously proposed algorithm, contains only general processes that govern the reaction rate and the formation of basic intermediate and final products. A such mechanism has the status of an nonempirical DKM because all parts, including elementary reactions, have kinetic substantiation. The mechanism itself has two features: (i) Reactions of so-called double addition of oxygen (first, to the alkyl radical, then to the isomerized form of the formed peroxide radical) are lacking because the first addition is considered to be sufficient; (ii) Isomeric compounds and their derivative substances as intermediate particles are not considered, because this means of oxidation is slower than through molecules and radicals of the normal structure. The application of the algorithm results in sufficiently compact mechanisms that are important for modeling chemical processes with the participation of paraffin hydrocarbons C n with large n. Previously, this was done for propane, n-butane, n-pentane, n-hexane, and n-heptane; in the present article, it was done for n-octane, n-nonane, and n-decane. The major feature of all the mechanisms is the appearance of stages, viz., cold and blue flames during low-temperature spontaneous ignition. The direct comparison of the calculation and experiment results is carried out.

Design and Testing of a Mini-Plant for Conversion of Organic Waste to Biogas

An experimental organic waste to biogas conversion mini-plant that works by anaerobic digestion has been designed, fabricated and tested. The demonstration involved the use of primarily, a biodigester and few other components. The organic waste was made into slurry and digested anaerobically for 14 days at an ambient temperature range of 28 to 32°C. The flame of biogas generated burnt with smokeless blue flame, indicating the presence of a colourless odourless gas called methane. The biodigester achieved a conversion efficiency of 64 percent. This equipment can be used to meet a good percentage of the fuel needs in Nigeria.