Cylindrical Reactor Research Articles

Numerical simulation on gas production from methane hydrate sediment by depressurization in a reactor with ice formation

Natural gas hydrate as a potential backup energy has very important scientific and social values. This paper aims at analyzing the gas production characteristic of methane hydrate sediment via depressurization. The physical model of 1 L cylindrical reactor is established and numerically simulated with the hydrate calculation software TOUGH + HYDRATE_v1.5. Based on the experiments, the cases in which ice formation are set to different initial reservoir pressures (2.0 MPa, 2.5 MPa, 3.0 MPa and 4.0 MPa) for numerical simulation to see the dissociation characteristics and heat and mass transfer during hydrate dissociation. The simulation results indicate that under the same driving force, the rate of hydrate dissociation increases with the initial pressure and the cumulative volumes of gas produced of the well and the sediment is the same due to the same initial hydrate saturation. The heat and mass transfer affected by ice formation plays an important role in hydrate dissociation and the temperature distribution in the sediment. When there is ice formation inside the sediment which inhibits the heat and mass transfer inside the sediment, the driving force should be carefully selected for different initial pressures to reduce the inhibitory effect of ice formation on hydrate dissociation.

Development of hydrogen storage reactor using composite of metal hydride materials with ENG

Hydrogen is widely accepted as a promising energy carrier replacing fossil fuels. In this context hydrogen storage is one of the critical challenges in realizing hydrogen economy which relies on hydrogen as the commercial fuel. Due to very low volumetric energy density of pure hydrogen, it is highly compressed as a gas phase or liquified at extremely low temperature. However, chemically combined state in other materials has advantages in terms of storage conditions and associated safety concerns.The present study focuses on a development of a hydrogen storage applicable to special fuel cell (FC) mobilities such as forklift but not limited to. We adopts a solid-state storage method using metal hydride composite prepared by processing La0.9Ce0.1Ni5 and extended natural graphite (ENG). The isothermal hydrogen absorption/desorption behavior of the composite is measured at 20–80 °C. The results suggest that around 10 bar is sufficient to store 1.2 wt% of hydrogen. A cylindrical reactor is manufactured and experiments are carried out with the fabricated hydrogen storage material by changing operation conditions. The results of satisfaction are obtained in terms of the amount of hydrogen storage (>83 standard liter) and the absorption time (~10 min) under relatively moderate conditions of temperature (~19 °C) and pressure (~11 bar).As for scaling-up, a reactor of 2.0 kWh is designed based on the experimental results. CFD analysis is performed based on the hottest operation conditions focusing on a cooling water flow. The flow pattern and the temperature distribution of the cooling water are expected to be adequate not deviating from the stable operating conditions. CFD would be further applied to optimize the incorporated modular reactors.

Enhancement of heat- and mass-transfer processes in a metal-hydride flow-through hydrogen-purification reactor

A novel method is proposed to increase the effective thermal conductivity of a metal-hydride (MH) bed by incorporating highly conductive inclusions into it in the form of metal rods made from various materials. The volume fraction of the inclusions, which had a diameter of 0.5 mm and length of 5 mm, ranged from 0.01 to 0.1. The structure of the composite beds was modelled by a specially developed algorithm. The results of the numerical simulation revealed that the effective thermal conductivity of the composite beds increased by 1.44–2.93 times when the volume fraction of the inclusions was 0.1. To estimate the effectiveness of the proposed method, a case study of hydrogen purification from a hydrogen–nitrogen mixture was performed for the cylindrical flow-through MH reactor, with two MH bed types: without inclusions (base case) and with inclusions (volume fraction of 0.1). The alloy fraction saturated by hydrogen and the mass of absorbed hydrogen higher for an equivalent reactor size notwithstanding a 10% reduction in the alloy mass. Moreover, the hydrogen losses were comparable to those of the base case. At hydrogen breakthrough, the fraction of hydride saturated by hydrogen increased from 61.5% to 81%, and the amount of hydrogen absorbed increased by 18.7%. The described method for enhancing the heat- and mass-transfer in MH beds enables the purification of a significantly larger volume of hydrogen with an equivalent number of sorption/desorption cycles.

Enhanced use of foam fractionation in the photodegradation of perfluorooctane sulfonate (PFOS)

Photodegradation of perfluorooctane sulfonate (PFOS) by UV irradiation could remove this environmentally persistent chemical from aqueous solution, but its efficiency needs to be further optimized. This study introduced foam fractionation technique, which utilizing the surface activity of PFOS, to promote the removal efficiency of PFOS during photodegradation. Under the favorable conditions of foam fractionation (pH = 11.0; the height to diameter ratio of the reaction solution = 3:1; gas flow rate = 1.0 L/min) in a cylindrical glass reactor, PFOS photodegradation rate (20 mg/L initial concentration) was 8.76 times higher than that without foam fractionation, over a 3-hour reaction. While under neutral condition, PFOS photodegradation rate also experienced an increase of 7.43, 6.20 and 2.66 times compared to that without foam fractionation for initial concentrations of 20 mg/L, 5 mg/L and 1 mg/L, respectively. This combination of foam fractionation and photodegradation process will hopefully be used for treatment of PFOS and other per- and polyfluoroalkyl substances with surface activity and photodegradability.

Experimental study of the lower flammability limits of H2/O2/CO2 mixture

The flammability limit of fuel is an important property in determining the explosivity characteristics. In order to improve the safety in the use of hydrogen in O2/CO2 atmosphere, the lower flammability limits of oxy-hydrogen mixture were studied experimentally. The lower flammability limits of hydrogen-oxygen diluted by CO2 were measured using a 5 L cylindrical reactor. In this method, the lower flammability limit was determined by the minimum hydrogen concentration that allows flame propagation. The upward flame was used for the critical criterion of the flame propagation. The measured lower flammability limits of H2/O2/CO2 increased from 4.25% to 6.5% with the diluted gas (CO2, N2) concentration rising from 0 to 85%, while the lower flammability limits of H2/O2/N2 mixture increased from 4.25% to 4.5%. Compared with N2, the lower flammability limits of H2 were raised by the adding CO2. The main reason is that the specific heat of CO2 is higher than that of N2. Moreover, CO2 directly participates in chemical reactions and heat radiation. The theoretical calculation results show that the thermal physical endothermic accounts for more than 90% of the total heat dissipation, which is the main factor affecting the lower flammability limits of hydrogen under O2/CO2 atmosphere. The experimental results are very helpful for developing a prediction model of the LFL for H2 in O2/CO2 atmosphere and theory results improve the understanding of the effect of CO2 on the LFL.

The effect of SDS surfactant on surface reaeration coefficient: a laboratory scale approach

Surface reaeration coefficient (K2), which represents the transfer of oxygen at the air-water interface, is an important variable in aquatic ecosystems. K2 is influenced by several factors, including surfactants; furthermore, this coefficient is used in water-quality models, which requires its correct estimation. This study evaluated the effects of the surfactant Sodium Dodecyl Sulfate (SDS) on K2 in two different experimental systems. In a cylindrical reactor with a turbine-type mechanical stirrer, 15 reaeration experiments were carried out with SDS concentrations of 0.0; 0.25; 0.5; 1.0 and 1.5 mMol L-1 and stirrer rotation velocities of 25, 50 and 100 rpm. In a circular hydraulic channel, 8 reaeration experiments were carried out, in triplicate, with SDS concentrations of 0 and 1.5 mMol L-1 and agitation levels of Reynolds 4,500, 37,500; 49,200 and 54,000. In the reactor, regardless of the rotation velocity, the surfactant reduced K2 by 20%, due to a superficial film formation at the interface that made oxygen transfer difficult, due to a phenomenon known as “barrier effect”. In the channel, an approximate K2 reduction of 15% occurred at higher levels of water agitation. In the presence of surfactants, and at low levels of agitation, phenomena that increase K2 (i.e., Marangoni effect) may coexist with those that reduce K2 (i.e., barrier effect). We concluded that the presence of SDS in aquatic environments should be considered when estimating the surface reaeration coefficient, because this surfactant can contribute to uncertain K2 estimation.

Influence of the radial neutron reflector efficiency on the power of fast nuclear-burning-wave reactor

The influence of the radial neutron reflector efficiency on the power of the prospective fast reactor operating in the self-sustained nuclear-burning-wave mode has been studied by means of numerically solving the neutron multigroup diffusion equation together with the set of the fuel burnup equations in the 2D cylindrical reactor geometry. Calculations have been performed for the time evolution of the spatial-energy distributions of the neutron flux and fuel components of U–Pu cycle during the reactor campaign. It has been shown that by changing the radial reflector efficiency (thickness) it is possible to change the reactor power in a wide enough range, up to the reactor shut down without intervening in its core. A principle possibility of the power control for the reactor working in the nuclear-burning-wave mode by changing the radial reflector efficiency is discussed.

Transient plasma-enhanced remediation of nanoscale particulate matter in restaurant smoke emissions via electrostatic precipitation

It is now recognized that nanoscale particulate matter (PM) represents a substantial health hazard for our society, including PM from restaurant smoke. In this study, we explored the use of a transient pulsed plasma in conjunction with an applied DC bias to treat oil aerosols that closely resemble restaurant (i.e., charbroiler) smoke emissions. For polyaromatic olefin PAO-4 and soybean oil, we found that a three-order-of-magnitude reduction in particulates (i.e., 99.9% remediation) could be achieved with this system. Here, the plasma discharge was produced in a 4-in.-diameter cylindrical reactor with a 5–10ns high voltage (30 kV) pulse generator together with applied DC bias voltages up to 10kV. The distribution of nanoparticle sizes was measured using a scanning mobility particle sizer (SMPS) with diameter centered around 225nm. Here, the main mechanism of remediation occurs in a two-step process in which the oil nanoparticles are first ionized by the free electrons and free radicals in the plasma and then the charged particles are swept out to the sidewalls of the reactor by the applied DC potential. We believe this general approach opens up new degrees of freedom in the design of electrostatic oil aerosol pollution control devices.

Metabolic engineering of phosphite metabolism in Synechococcus elongatus PCC 7942 as an effective measure to control biological contaminants in outdoor raceway ponds

BackgroundThe use of cyanobacteria and microalgae as cell factories to produce biofuels and added-value bioproducts has received great attention during the last two decades. Important investments have been made by public and private sectors to develop this field. However, it has been a challenge to develop a viable and cost-effective platform for cultivation of cyanobacteria and microalgae under outdoor conditions. Dealing with contamination caused by bacteria, weedy algae/cyanobacteria and other organisms is a major constraint to establish effective cultivation processes.ResultsHere, we describe the implementation in the cyanobacterium Synechococcus elongatus PCC 7942 of a phosphorus selective nutrition system to control biological contamination during cultivation. The system is based on metabolic engineering of S. elongatus to metabolize phosphite, a phosphorus source not normally metabolized by most organisms, by expressing a bacterial phosphite oxidoreductase (PtxD). Engineered S. elongatus strains expressing PtxD grow at a similar rate on media supplemented with phosphite as the non-transformed control supplemented with phosphate. We show that when grown in media containing phosphite as the sole phosphorus source in glass flasks, the engineered strain was able to grow and outcompete biological contaminants even when the system was intentionally inoculated with natural competitors isolated from an irrigation canal. The PtxD/phosphite system was successfully used for outdoor cultivation of engineered S. elongatus in 100-L cylindrical reactors and 1000-L raceway ponds, under non-axenic conditions and without the need of sterilizing containers and media. Finally, we also show that the PtxD/phosphite system can be used as selectable marker for S. elongatus PCC 7942 transgenic strains selection, eliminating the need of antibiotic resistance genes.ConclusionsOur results suggest that the PtxD/phosphite system is a stable and sufficiently robust strategy to control biological contaminants without the need of sterilization or other complex aseptic procedures. Our data show that the PtxD/phosphite system can be used as selectable marker and allows production of the cyanobacterium S. elongatus PCC 7942 in non-axenic outdoor reactors at lower cost, which in principle should be applicable to other cyanobacteria and microalgae engineered to metabolize phosphite.

Smoldering fire propagation in corn grain: an experimental study

Smoldering fire exhibits low-velocity combustion rates and is a threat commonly presented in agriculture grain storages. Some physical and chemical properties of the grain, including particle size, porosity, moisture, and the environmental conditions influence the propagation of the smoldering process. Many works evaluate the conditions to develop smoldering combustion based on particulate size and granular materials. However, only a few studies focusing on smoldering propagation in cornflour and granular grains. In this work, different particle diameters (181.6 ​μm, 776.4 ​μm and 1411 ​μm) and moisture contents (0% and 15%) of corn are examined to understand the corresponding impact on the smoldering propagation. To achieve this, samples of corn were placed inside a cylindrical reactor with thermocouples distributed along the apparatus’ central axis and heated by a hot plate, then the smoldering reaction with a rising heating transfer profile was analyzed. Our results demonstrate how changing storage conditions can profoundly influence the smoldering propagation within a pile of corn.

Effect of Reactor Size in a Laterally-Heated Cylindrical Reactor

Effect of Reactor Size in a Laterally-Heated Cylindrical Reactor

Effects of electrode material and frequency on carbon monoxide formation in carbon dioxide dielectric barrier discharge

The transformation of carbon dioxide (CO2) to carbon monoxide (CO) employing atmospheric pressure dielectric barrier discharge (DBD) cold plasma is reported. This work is carried out with an objective to re-utilize CO2 in the form of CO, which is extremely useful in various industries. Under the study, neat CO2 gas stream is used to investigate effective conditions for achieving high yields of CO using coaxial cylindrical tube type double and single dielectric DBD reactors. The different central electrodes for example Pyrex and bare metal such as Aluminium (Al), Copper (Cu) and Stainless steel (SS) along with common outer Pyrex tube combinations respectively in double dielectric (DD) and single dielectric (SD) surface reactors are used separately. DBD outlet products such as CO and leftover CO2 are analyzed and estimated with online gas chromatograph-flame ionization detector after separating them with a suitable GC column followed by their conversion to methane using Ni-catalyzed methaniser. Furthermore, the investigation of CO production is made with gas residence time (CO2 flow), applied electric field and working frequency variations. Optical emission spectroscopy (OES) for mechanistic details and power measurement for quantitative analysis are carried out. The production of CO from 200 to 70,000 ppmv is observed with DD reactor respectively at 50 Hz and 19 kHz frequencies. In case of SD reactors, the CO yields obtained are higher with the utmost CO concentration ∼130,000 ppmv using Cu central electrode following as a minimum 13 % of CO2 transformation.

Hydrogen absorption performance of a novel cylindrical MH reactor with combined loop-type finned tube and cooling jacket heat exchanger

A novel cylindrical metal hydride (MH) reactor with loop-type finned tube and jacket heat exchanger was proposed in this work. This MH reactor is expected to possess high performance due to the enhanced heat transfer, compact structure and good gas tightness. A three-dimensional multi-physical model for hydrogen absorption was presented to investigate the evolutions of temperature and concentration in the MH bed, as well as the mean reaction rate of hydrogen absorption process. The effects of different fin configurations on the performance of the proposed MH reactor were also examined. It was indicated that the evolution curve of the mean reaction rate for the whole hydrogen absorption process can be divided into two stages. The reaction rate in the first stage is mainly dependent on the initial conditions (i.e., temperature and gas pressure) of MH bed, whereas the second stage is mainly influenced by the heat dissipation from MH bed to cooling fluid. For the proposed MH reactor, the total charging time for reaching 90% hydrogen saturation can be decreased by 56.8% and 81.9% as compared with that for cylindrical MH reactor with finned double U-shape tube heat exchanger and cylindrical MH reactor with finned single-tube heat exchanger, respectively. Also, it was found that the interlaced layout design of inner and outer fins can improve the uniformity of the temperature distribution inside the MH bed as compared with the parallel layout configuration. Besides, it was showed that increasing the number of fins with keeping the total fin volume constant, the absorption performance of the reactor can be improved.

Numerical simulation of ammonium perchlorate particles based on a population balance equation model in Taylor-Couette flow

Taylor-Couette flow, multiple vortex rings, is developed by rotating a co-axial rod in a cylindrical reactor. It is helpful in applying stable shear forces to suspended particles in the fluid domain. Recently, by using the Taylor-Couette flow, various experiments were performed to prepare micro-size particles at the laboratory level. However, unlike the simple concept of particle preparation by the Taylor-Couette flow, it is challenging to predict particle size distributions in the fluid domain, especially in the scale-up issue of a Taylor-Couette reactor. In this reason, computational methods are required to calculate particle growth in fluid flow. In this paper, ammonium perchlorate particles in the Taylor-Couette flow are simulated by using a population balance equation model, connected to a module of computational fluid dynamics. First of all, physical and empirical parameters for the population balance equation are determined by using experimental data in a Taylor-Couette flow reactor. Secondly, particle size distributions in a scale-up reactor are predicted by using the proposed method. Finally, validity and applicability of the suggested method are fully discussed on the basis of simulation results. As a major result, the simulation model for ammonium perchlorate particles was reliable in predicting their sizes along time. In addition, without changing the model parameters, the simulation results matched well with the experiments in the scale-up reactor. Based on the simulation results, it is expected that the suggested method can be utilized to estimate particle size distributions in various boundary and operating conditions.

Forced Aerated Poultry Compost Effects on Soil Physicochemical Properties and Lettuce Plant Growth

In previous studies, the stability and maturity of forced aerated composts were examined from the physicochemical analysis inside the reactors. The objective of this study is to check the maturity and effects of forced aerated composts after its addition to soil and plants. The composts were prepared from fresh chicken manure and sawdust in cylindrical reactors and aerated at 0.75, 0.50, and 0.25 L min−1 kg−1 organic matter (OM) for 1 month. Afterward, it was mixed with soil and coded as treatment T1 (0.75 L min−1 kg−1 OM aeration rate + soil), T2 (0.50 L min−1 kg−1 OM aeration rate + soil), T3 (0.25 L min−1 kg−1 OM aeration rate + soil), and CS (only soil), respectively. The soil properties (pH, electrical conductivity (EC), organic matter content (OM), loss of organic matter content, bulk density (BD), water holding(WH)) and plant growth (shoot length (cm), leaves’ area (cm2), fresh and dry weight (g)) were checked for 4 months. The results showed a significant increase (at P < 0.05) in soil properties in T1, T2, and T3 as compared with CS. Among treatments T1, T2, and T3, the maximum pH (7.20 ± 0.07), OM degradation (77.06%), loss of organic matter (6.32 ± 0.42%), and WH (32.17 ± 0.32%) were observed in T3. Additionally, the lowest EC (1.15 ± 0.02 mS/cm) and BD (1.06 ± 0.02%) were observed in T3. Further a significant increased difference (at P < 0.05) in shoot length (21.40 ± 1.01 cm), leaves’ area (293.20 ± 16.33 cm2), fresh weight (88.22 ± 7.30 g), and dry weight (12.10 ± 0.91 g) of the plant were observed in T3. The poultry manure compost’s aerated rate (0.25 L min−1 kg−1 OM) in T3 was observed to be more mature and stable as compared with T1 and T2.

Styrene Recovery from the Pyrolysis of Polystyrene Waste Using Bentonite and Natural Zeolite Catalyst

Polystyrene is a type of plastic that is widely used in daily life. It is applied for decoration, food packaging, and electronic packaging process. However, the use of polystyrene has become a problem for the environments because its properties are difficult to be degraded by nature. Pyrolysis method can be regarded as one of the environmentally friendly methods for recycling polystyrene waste. This research aims to investigate the effect of bentonite and natural zeolite catalyst on the pyrolysis of polystyrene. The experiment was carried out in a batch process. The pyrolysis process consists of a cylindrical reactor with electrical heater, a condenser, and a liquid product container. About 100 grams of polystyrene material was pyrolysis per batch. Catalysts used in the variation of 0%, 10%, 15%, 20%, and 25% of polystyrene. The liquid product was collected in 60 minutes and weighed. The composition of the liquid product was determined by gas chromatography. Polystyrene pyrolysis utilizes bentonite and natural zeolite as the catalyst. It produces benzene, toluene, ethylbenzene, styrene, and isopropyl benzene as the liquid product, and polystyrene residue as a solid product. Among the catalyst studied, bentonite is found to be the most efficient and increase the styrene selectivity (30.28 wt%) significantly at a reaction temperature of 400°C in comparison to the natural zeolite catalyst.

Study on methane hydrate distributions in laboratory samples by electrical resistance characteristics during hydrate formation

To determine hydrate distributions in laboratory samples, a 5.701 L cylindrical reactor was designed and fabricated to synthesize hydrate-bearing samples with the excess-water method. The influences of temperature, water content, gas content, and electrode distance on the changing rules of electrical resistance, as well as measuring electrical resistance in nine samples, were systematically studied. The results indicated that the electrical resistance was increased with decreasing temperature, reducing water content or increasing gas content in deionized water settings, resembling electrical resistance changes in brine system. These rules were further used to analyze electrical resistance characteristics in the whole process of preparing and forming hydrate-bearing samples. Fresh hydrate formation was found to govern the electrical resistance increases after the induction periods. Resistance ratio and net increase of resistance analyses showed that the hydrate distributions in the samples with small hydrate saturations suffered more heterogeneity. Hydrate distributions in the samples with small and large hydrate saturations were inferred to be mass-like and rod-like, respectively. In addition, the dissociation of a sample (Sh=19.46%) by depressurization confirmed more hydrates were dispersed near the right side of this cylindrical sample, which was in agreement with the result from electrical resistance analysis. Since hydrate distributions affected the outcomes of physical simulations, this work may offer some references to similar studies.

Experimental Study of Pyrolysis and Laser Ignition of Low-Vulnerability Propellants Based on RDX.

Low-vulnerability propellants are propellants designed to resist unintended stimuli to increase safety during transport, storage and handling. The substitution of usual nitrocellulose-based gun propellants with these new materials allows maintaining interior ballistics performances while increasing the safety. In this paper, the pyrolysis, ignition and combustion of such propellants are investigated in order to study conditions leading to a safe and reproducible ignition. Low-vulnerability propellants studied are made of different ratios of hexogen (RDX) and nitrocellulose (NC). Three compositions are studied by varying weight percentages of RDX and NC: 95-5, 90-10 and 85-15 for respective weight percentages of RDX-NC. Pyrolysis of these propellants is studied with two different experimental setups: a flash pyrolysis device linked to a gas chromatograph coupled to a mass spectrometer (Py-GC-MS) and a closed-volume reactor coupled to a mass spectrometer. Different molecules, like NO2, CO, CH3COCH3 or CH2NCH2NCH2, are obtained during the decomposition of these propellants. Laser ignition of these propellants is studied in a cylindrical closed-volume reactor using a laser diode. Several combustion characteristics, such as ignition delays, maximal overpressures and combustion rates are given for the three propellants using the pressure signals. Moreover, ignition energies are also investigated. Obtained results are compared to the few available literature data. A particular behavior is noticed for the 90-10 propellant. The experimental data collected should serve in the future to have a better understanding of the chemical reactions driving the combustion process of these low-vulnerability propellants.

Ignition of Hydrogen–Hydrocarbon (C1–C6)–Air Mixtures over the Palladium Surface at 1–2 Atm

In this paper, we report the results of studying the combustion characteristics of fuels containing a hydrogen–hydrocarbon (C1–C6, as in CH4, C2H6, C3H8, C4H10, C5H12, and C6H14) mixture with a fuel fraction of 0.6–1.2 in a mixture with air above the palladium surface at a total pressure of 1–2 atm. The propagation features of the flame front in mixed fuels are revealed, and the temperature dependences of the ignition limit over the palladium surface are determined. The observed separation of the CH and Na emission bands in time during the combustion of the 30% propane + 70% H2 + air mixture (the fuel fraction in the mixture with air is unity) was established to be caused by the occurrence of hydrodynamic instability of the flame when it touches the end of a cylindrical reactor.

Optimization of photocatalytic degradation of methylene blue dye using titanate nanotube

Titanate nanotubes were evaluated for photocatalytic depletion of methylene blue (MB) dye under UV radiation in a cylindrical reactor. Titanate has been prepared using the method of hydrothermal treatment where the precursors are TiO2 and NaOH. Transmitting electron microscopy (TEM) and x-ray diffraction (XRD) were used to characterize the prepared nanotubes. The effect of some parameters was examined. It was shown that removing the dye is effective: dye initial concentration 5 to 10 ppm, dosage of catalyst 0.25 to 0.50 g catalyst/l of the solution, and mixture pH 1.4 to 12.6. A total of 17 runs have been designed to take into account the effective ranges of the effective variables using the experimental Box–Behnken technique. Two polynomial models were tailored to the experimental outputs created by the response surface methodology, demonstrating a functional correlation between MB’s percent degradation and experimental parameters. Design Expert program V.6.0.7 was utilized to maximize the reaction rate of the experimental parameters. The optimum parameter values were initial concentration of MB 5.45 ppm, a dose of TiO2 0.50 g / l, and pH of the mixture 11.89. Under these conditions, the percentage of degradation of MB was 99.0995%.