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New six-dimensional ab initio potential energy surfaces (PESs) for the N2–CO2 complex, which involve the stretching vibration of N2 and the Q3 normal mode for the ν3 asymmetric stretching vibration of CO2, were constructed using the CCSD(T)-F12/AVTZ method with midpoint bond functions. Two vibrational averaged 4D interaction potentials were obtained by integrating over the two intramolecular coordinates. It was found that both PESs possess two equivalent T-shaped global minima as well as two in-plane and one out-of-plane saddle points. Based on these PESs, rovibrational bound states and energy levels were calculated applying the radial discrete variable representation/angular finite basis representation method and the Lanczos algorithm. The splitting of the energy levels between oN2–CO2 and pN2–CO2 for the intermolecular vibrational ground state is determined to be only 0.000 09 cm−1 due to the higher barriers. The obtained band origin shift is about +0.471 74 cm−1 in the N2–CO2 infrared spectra with CO2 at the ν3 zone, which coincides with the experimental data of +0.483 74 cm−1. The frequencies of the in-plane geared-bending for N2–CO2 at the ν3 = 0 and 1 states of CO2 turn out to be 21.6152 and 21.4522 cm−1, the latter reproduces the available experimental 21.3793 cm−1 value with CO2 at the ν3 zone. The spectral parameters fitted from the rovibrational energy levels show that this dimer is a near prolate asymmetric rotor. The computed microwave transitions as well as the infrared fundamental and combination bands for the complex agree well with the observed data. [ABSTRACT FROM AUTHOR]

This work focused on the evaluation of co-combustion of sewage sludge (SS) and rice husk (RH) using thermogravimetric–Fourier transform infrared spectrometry method (TG–FTIR). The thermal behavior was assessed through the combustion characteristic, interaction, kinetics, and gaseous product characteristics. The (co-)combustion process was divided into three stages. Index D exponentially increased as RH blending ratio increased and index S also increased from 10 to 70% RH blending ratio, indicating that the combustion behavior was improved by the RH blending. The activation energy was evaluated by two model-free iso-conversional methods: Flynn–Wall–Ozawa (FWO) and Kissinger–Akahira–Sunose (KAS). The minimum value of average activation energy among blends was obtained at sample with 30% RH blending, which was 103.31 kJ/mol by FWO and 97.81 kJ/mol by KAS. Several typical gaseous products and functional groups were detected by FTIR spectrum. The results showed that CO2 was the main volatile and its yield increased with the RH blending ratio. [ABSTRACT FROM AUTHOR]

Scrap tire is a typical waste fuel, for which the combustion in the form of pellets is a feasible way. In this work, the ignition behavior, combustion process and pollutant emission of the scrap tire in pellet form are explored. The experiments were performed in the vertical heating tube furnace under different coflow conditions in CO2/O2 atmosphere. The temperature was set to 873, 973, 1073 K and the gas flow rate was set to 5, 10 and 20 L/min. The combustion images of scrap tire were recorded by the high-performance camera. The scrap tire pellet presented the characteristics of homogeneous ignition and the fly ash was captured around the scrap tire pellets. Increasing oxygen concentration and temperature shortened the ignition delay time and reduced the internal ignition temperature. The splash flame occurred during the volatile combustion under the conditions of high temperature, high oxygen concentration, and high gas flow rate. The distinct pores and cracks were found on the surface of char during the char combustion. The yields of pollutant gas increased as the gas flow rate increased from 5 to 20 L/min. With the increase of temperature, the emission of NO and SO2 was increased but NO2 emission was decreased. [ABSTRACT FROM AUTHOR]

Summary: To solve the problems of energy shortage and waste accumulation, the method of co‐combustion of sewage sludge (SS) and peanut shells (PS) was proposed. SS‐PS co‐combustion characteristics in air were investigated using artificial neural networks (ANN) and thermogravimetric analyses (TGA). The proportion of PS in the mixture was 10%‐50%. The temperature range of PS combustion (160‐560°C) is lower than that of PS combustion (170‐600°C). Activation energy was estimated from two non‐isothermal kinetic analysis methods: Kissinger‐Akahira‐Sunose (KAS) and Flynn‐Wall‐Ozawa (FWO). The kinetic mechanism of the combustion process was determined by using the master‐plots method. Multiple ANN models were established to predict TG data of SS‐PS co‐combustion. The best prediction model (ANN21) was obtained. The results showed a good overlap between the predicted and experimental TG data. The ANN model and the master‐plots method are the main innovations of this study. This study can promote the utilization and reduction of solid waste, and give guidance for the large‐scale application of SS‐PS co‐combustion. [ABSTRACT FROM AUTHOR]

Abstract This study investigated the combustion characteristics and kinetics of sewage sludge (SS), wheat straw (WS) and their blends using thermogravimetric analysis, under air condition. Combustion characteristic parameters of SS blended with 5%–50% WS was enhanced, especially revealed by an increase in comprehensive combustion index. A significant synergetic interaction was found in high temperature region through experiments. When proportion of WS was 50%, the synergetic interaction was strongest. And the catalytic effect of alkali metal oxides in WS ash on the combustion of SS residues at high temperature region had a strong effect on synergetic interaction. Metal oxides circulated in different oxide forms to transport oxygen to carbon surface, leading to catalytic effect. Activation energy was evaluated by two isoconversional method: Flynn-Wall-Ozawa and Vyazovkin method. The lowest average activation energies of the blends were obtained at 50% wheat straw blending ratio (89.29 kJ/mol by FWO and 87.48 kJ/mol by V, respectively). The thermodynamic parameters (Gibbs free energy, Entropy and Enthalpy) were also obtained. And two master plots methods were utilized to determine the appropriate fit kinetic model of combustion which can be described by Avarami-Erofeve (A2). Highlights • TG analysis of co-combustion between sewage sludge and wheat straw was studied. • Blending wheat straw improved the thermal behavior of sewage sludge combustion. • Synergetic interaction was found at high temperature in positive manner. • The minimum average activation energy was obtained by blending 50% wheat straw. [ABSTRACT FROM AUTHOR]

We constructed a new ab initio potential energy surface (PES) for CO-N 2 O which includes the intramolecular Q 3 normal coordinate for the N 2 O ν 3 antisymmetric stretching vibration. The intermolecular potential was evaluated employing the supermolecular method at the [CCSD(T)]-F12a level, with the aug-cc-pVTZ basis set plus bond functions. By integral over the intramolecular Q 3 coordinate, we obtained the vibrationally averaged PESs for the CO-N 2 O system in the ground and ν 3 excited states of N 2 O. Each PES features one nearly T-shaped global minimum and one skewed T-shaped local minimum. Based on these obtained PESs of CO-N 2 O, the radial discrete variable representation/angle finite base representation method and the Lanczos algorithm were applied for the calculations of bound states and rovibrational energy levels. The calculated ν 3 vibrational band origin shift of the N 2 O monomer in CO-N 2 O is 2.7570 cm -1 , matching well with the observed value of 2.9048 cm -1 . The computed microwave and infrared transition frequencies, as well as the rotational parameters, are consistent with the experimental observations.