Identification of ground spilled oil of buried pipeline based on laser absorption spectroscopy: Numerical investigation and experimental verification.

The ground diffusion characteristics of buried oil pipeline after leakage and the laser optical transmission mechanism of surface oil film are the basis of spectral detection technology. Based on the computational fluid dynamics to solve the diffusion equation of multiphase flow in porous media, the leakage law of oil under different soil porosity is analyzed in two dimensions: surface diffusion diameter and oil film thickness. TracePro optical simulation is used to study the absorption and reflection patterns of laser at the oil-gas interface, and validation experiments are carried out based on the tunable diode laser absorption spectroscopy method. The results show that oil is easily accumulated on the ground surface with larger soil porosity and in the depressions of the ground surface. When the oil film thickness is greater than 2 mm, the laser cannot transmit the oil layer and the received light intensity is only provided by the mirror reflection at the oil-gas interface. The mechanism of laser detection of oil leaks is the spectral absorption of volatile alkane gases in the upper layer of the oil film by a laser of a specific wavelength.

Roles of free radicals in NO oxidation by Fenton system and the enhancement on NO oxidation and H2O2 utilization efficiency.

Low H2O2 utilization efficiency is the main problem when Fenton system was used to oxidize NO in flue gas. To understand the behaviour of the free radicals during NO oxidation process in Fenton system is crucial to solving this problem. The oxidation capacity of [Formula: see text] and [Formula: see text] on NO in Fenton system was compared and the useless consumption path of [Formula: see text] and [Formula: see text] that caused the low utilization efficiency of H2O2 were studied. A method to enhance the oxidation ability and H2O2 utilization efficiency by adding reducing additives in Fenton system was proposed. The results showed that both of [Formula: see text] and [Formula: see text] were active substances that oxidize NO. However, the oxidation ability of [Formula: see text] radicals was stronger. The vast majority of [Formula: see text] and [Formula: see text] was consumed by rapid reaction [Formula: see text] , which was the primary reason for the low utilization efficiency of H2O2 in Fenton system. Hydroxylamine hydrochloride and ascorbic acid could accelerate the conversion of Fe3+ to Fe2+, thereby increase the generation rate of ·OH and decrease the generation rate of [Formula: see text]. As a result, the oxidation ability and H2O2 utilization efficiency were enhanced.

Free radical behaviours during methylene blue degradation in the Fe2+/H2O2 system.

Behaviours of the free radicals during the methylene blue (MB) oxidation process in the Fe2+/H2O2 system were studied to reveal the reason for the low utilization efficiency of H2O2. The roles of O2-∙ , ∙OH and HO2∙ radicals were proven to be different in the MB oxidation process. The results showed that O2-∙ radicals had a strong ability to oxidize MB; however, they were not the main active substances for MB degradation due to the low concentration in the traditional Fe2+/H2O2 system. HO2∙ radicals could not oxidize MB. ∙OH radicals were the main active substances for MB oxidation. In the short initial stage, the utilization efficiency of H2O2 was high, because the generation rate of ∙OH was much higher than that of HO2∙ . More ∙OH radicals were involved in the MB oxidation reaction. In the long deceleration stage (after the short initial stage), a large amount of H2O2 was consumed, but the amount of oxidized MB was very small. Most of the ∙OH radicals were consumed via the rapid useless reaction between ∙OH and HO2∙ in this stage, resulting in the serious useless consumption of H2O2. It is a feasible method to improve the utilization efficiency of H2O2 by adding suitable additives into the Fe2+/H2O2 system to weaken the useless reaction between ∙OH and HO2∙ .

Optical Properties of Oilfield Wastewater and its Application in Measuring Oil Content.

Optical properties of oilfield wastewater play an important role in the on-line measurement of oil content. As an important parameter of optical properties, absorption coefficient is usually obtained by indirectly modeling transmittance spectra. In this work, transmittance spectra of oilfield wastewater in the wavelength range of 190-900 nm at normal incidence were measured by TU-1900 double beam ultraviolet visible spectrophotometer. The absorption coefficient of oilfield wastewater was obtained by a double thickness method, and the relationship between the oil content in oilfield wastewater and its absorption coefficient was studied. The results show that the transmittance spectra of oilfield wastewater decrease with the increase of oil content. The oil content of oilfield wastewater is found to correlate negatively with its transmittance. The oil content of oilfield wastewater and its absorption coefficient have a good fitting effect at 234 nm, and the fitting error of three order polynomial fitting is minimal, with a range of 0.02-5.39%, and the fitting accuracy is 0.9940.

Optimization of NO oxidation by H2O2 thermal decomposition at moderate temperatures.

H2O2 was adopted to oxidize NO in simulated flue gas at 100-500°C. The effects of the H2O2 evaporation conditions, gas temperature, initial NO concentration, H2O2 concentration, and H2O2:NO molar ratio on the oxidation efficiency of NO were investigated. The reason for the narrow NO oxidation temperature range near 500°C was determined. The NO oxidation products were analyzed. The removal of NOx using NaOH solution at a moderate oxidation ratio was studied. It was proven that rapid evaporation of the H2O2 solution was critical to increase the NO oxidation efficiency and broaden the oxidation temperature range. the NO oxidation efficiency was above 50% at 300-500°C by contacting the outlet of the syringe needle and the stainless-steel gas pipe together to spread H2O2 solution into a thin film on the surface of the stainless-steel gas pipe, which greatly accelerated the evaporation of H2O2. The NO oxidation efficiency and the NO oxidation rate increased with increasing initial NO concentration. This method was more effective for the oxidation of NO at high concentrations. H2O2 solution with a concentration higher than 15% was more efficient in oxidizing NO. High temperatures decreased the influence of the H2O2 concentration on the NO oxidation efficiency. The oxidation efficiency of NO increased with an increase in the H2O2:NO molar ratio, but the ratio of H2O2 to oxidized NO decreased. Over 80% of the NO oxidation product was NO2, which indicated that the oxidation ratio of NO did not need to be very high. An 86.7% NO removal efficiency was obtained at an oxidation ratio of only 53.8% when combined with alkali absorption.

[Optical Constants Determination of Zinc Selenide by Inversing Transmittance Spectrogram Transmittance Spectra Measurement and Thermal Radiative Physical Parameters Inversion of Diesel Fuel].

A novel inversion method of optical constants of diesel fuel that is one of semitransparent liquid was developed based on spectral transmittance radio inversion calculation of optical cell with glass-liquid fuel-glass configuration, which was validated by measured the optical constants of water. The measurements of transmittance spectrogram of optical cell filled with diesel fuel in the infrared wavelength 2 - 15 µm at normal incidence were investigated by Bruke V70 FTIR spectrometer. The optical constants and thermal radiative physcial parameters of diesel fuel were achieved. The results show that, (1) The optical constants of water determined by the new method (IDTM) have good agreement with previously data sets. (2) The optical constants calculation precision of the IDTM is similar with MCDTM, which is higher than SODTM and SDTM. (3) The transmittance capability of diesel fuel in the infrared wavelength 2 - 15 µm are weak, and there exist five absorption peaks, which are respectively 2.4, 3.4, 6.2, 7.3 and 13.8 µm. (4) The spectral selectivity of optical constants and thermal radiative physcial parameters of diesel fuel are stronger, whose values are urgently varied with different wavelenths.