This review deals with the state-of-the-art of waste tyre pyrolysis for the first time in literature. Pyrolysis has been addressed as an attractive thermochemical process to tackle the waste tyre disposal problem while allowing energy recovery. Pyrolysis enables the separation of carbon black from tyres and the volatile matter released (condensable and non-condensable compounds) has the potential of renewable energy recovery given the significant proportion of natural rubber present in the tyre. Given this waste-to-energy pathway, a comprehensive review has been carried out in order to show the effects of the main process conditions (heating rate, temperature, pressure, carrier gas flow rate and type, volatiles residence time and pyrolysis time) on the physicochemical properties and distributions of the resulting products (gas, liquid and solid fractions). It has also been reviewed the influence of the size and composition of the feedstock. All reported results have been framed regarding the type of reactor as well as the experimental conditions used to avoid contradictions among the large number of publications on the subject. It is shown that the occurrence of secondary reactions is very sensitive to the interaction of the aforementioned variables. Also, the main properties of the pyrolytic products are pointed out. The liquid and gaseous fractions obtained are a valuable fuel source; while the solid fraction (char) has the recovery potential of low- grade carbon black or as carbon adsorbent after applying an activation step. Special attention has been given to the liquid fraction, highlighting its properties as alternative fuel in compression ignition engines.

Waste tyre pyrolysis – A review

The editors have assembled a world-class group of contributors who address the questions the combustion diagnostic community faces. They are chemists who identify the species to be measured and the interfering substances that may be present; physicists, who push the limits of laser spectroscopy and laser devices and who conceive suitable measuremen

Applied Combustion Diagnostics

DEM/CFD-DEM Modelling of Non-spherical Particulate Systems: Theoretical Developments and Applications

A second-order accurate immersed boundary method for fully resolved simulations of particle-laden flows

Up to this point we have concerned ourselves with radiative heat transfer problems, where the necessary geometry, temperatures, and radiative properties are known, enabling us to calculate the radiative intensity and radiative heat fluxes in such enclosures. Such cases are sometimes called “direct” heat transfer problems. However, there are many important engineering applications where knowledge of one or more input parameters is desired that cause a certain radiative intensity field. For example, it may be desired to control the temperatures of heating elements in a furnace, in order to achieve a specified temperature distribution or radiative heat load on an object being heated. Or the aim may be to deduce difficult to measure parameters (such as radiative properties, temperature fields inside a furnace, etc.) based on measurements of radiative intensity or radiative flux. Such calculations are known as inverse heat transfer analyses.

Inverse Radiative Heat Transfer

Towards getting the full-scale solutions to particle-laden flows, a multidirect forcing technique and immersed boundary method are proposed in the present work. The immersed solid boundary is represented by Lagrangian points and the no-slip condition is efficiently satisfied by exerting multidirect forcing. The hydrodynamic interactions between the stationary or moving solid boundary and the Newtonian fluid are able to be accurately described. This method is simple but efficient which is validated by simulating the flows around a stationary circular disc at different Reynolds numbers and the free sedimentation of a particle. The predicted results agree well with previous experimental and numerical data. When applying this method to study particle sedimentation near a vertical wall, the rotation shifting phenomenon is observed besides the anomalous rolling and the lateral migration.

Full-scale solutions to particle-laden flows: Multidirect forcing and immersed boundary method

1 Introduction.- 1-1 Principles of Boiler Operation.- 1-2 Classification of Boilers.- 1-3 Description of Boilers.- References.- 2 General Design Considerations.- 2-1 Boiler Specifications.- 2-2 Design Steps.- References.- 3 Fuel and Combustion Calculations.- 3-1 Features of Fuel.- 3-2 Stoichiometric Calculations.- 3-3 Enthalpy Calculation of Air and Combustion Products.- 3-4 Heat Balance.- 3-5 Generation of SO2and NOx.- Nomenclature.- References.- 4 Coal Preparation Systems for Boilers.- 4-1 Coal Preparation Systems.- 4-2 Pulverizing Properties of Coal.- 4-3 Pulverizing Air System.- 4-4 Size-Reducing Machines.- 4-5 Other Components for Coal Preparation Systems.- 4-6 Design of Coal Preparation System for Pulverized Coal Boilers.- 4-7 Fuel Feeding in Fluidized Bed Boilers.- Nomenclature.- References.- 5 Design of Oil Burners.- 5-1 Design of Oil Supply System.- 5-2 Oil Atomizers.- 5-3 Air Registers.- 5-4 Design Principles of Oil Fired Boilers.- Nomenclature.- References.- 6 Boiler Furnace Design Methods.- 6-1 General Design Principles.- 6-2 Flame Emissivity.- 6-3 Heat Transfer Calculations for the PC Boiler Furnace.- 6-4 Water Wall Arrangement.- 6-5 Fouling and Thermal Efficiency Factors for Water Wall Tubes.- 6-6 Temperature Field CoefficientM.- 6-7 Furnace Emissivity.- 6-8 Distribution of Heat Load in Furnace.- Nomenclature.- References.- 7 Convective Heating Surfaces.- 7-1 Design of Superheater and Reheater.- 7-2 Temperature Control in Superheater and Reheater.- 7-3 Adjustment of Heat Absorption in Superheater and Reheater..- 7-4 Economizer.- 7-5 Air Heater.- 7-6 Arrangement of Back-Pass Heating Surfaces.- 7-7 Heat Transfer Calculations for Convective Heating Surfaces.- 7-8 Design Methods of Convection Heating Surfaces.- Nomenclature.- References.- 8 Swirl Burners.- 8-1 Design of a Swirl Burner.- 8-2 Flow Resistance in Swirl Burners.- 8-3 Examples of Swirl Burners.- 8-4 Arrangement of Multiple Swirl Burners.- 8-5 Design Procedure of Swirl Burners.- Nomenclature.- References.- 9 Design of Novel Burners.- 9-1 Types of PC Burners.- 9-2 PC Burner With Blunt Body.- 9-3 Precombustion Chamber Burner.- 9-4 Boat Burner.- 9-5 Co-Flow Jet Burner With High Differential Velocity.- 9-6 Counter-Flow Jet Burner.- 9-7 Dense and Lean Phase PC Burner.- 9-8 Down-Shot Flame Combustion Technique.- 9-9 Low NOxBurner.- Nomenclature.- References.- 10 Tangentially Fired Burners.- 10-1 General Descriptions.- 10-2 Design of Burners With Peripheral Air.- 10-3 Design of Tilting Burners.- 10-4 Burners for Bituminous Coal.- 10-5 Anthracite and Lean Coal Fired PC Burner.- 10-6 Brown Coal Fired Direct Burner.- 10-7 Multifuel Burner.- 10-8 Design Methods for Tangentially Fired Boilers.- 10-9 Example of Burner Design.- Nomenclature.- References.- 11 Fluidized Bed Boilers.- 11-1 Fluidized Bed Boiler.- 11-2 Major Features of Fluidized Bed Boilers.- 11-3 Basics of Fluidized Beds.- 11-4 Bubbling Fluidized Bed Boilers.- 11-5 Circulating Fluidized Bed Boilers.- 11-6 Distributor Plates.- 11-7 Loop Seals.- 11-8 Gas-Solid Separators.- Nomenclature.- References.- 12 Steam-Water Circulation in Boiler.- 12-1 Natural Circulation System.- 12-2 Calculations for Simple and Complex Tube Circuits.- 12-3 Two-Phase Flow Resistance.- 12-4 Height of Economizer Section in the Riser.- 12-5 Worked-Out Example.- Nomenclature.- References.- 13 Forced Circulation for Supercritical or Subcritical Boilers.- 13-1 General Description.- 13-2 Design Principle of Forced Circulation Boiler.- 13-3 Features of Forced Circulation Boilers.- 13-4 Supercritical Boilers.- 14 Corrosion and Fouling of Heat Transfer Surfaces.- 14-1 High-Temperature Corrosion of External Surfaces.- 14-2 Prevention of High-Temperature Corrosion.- 14-3 Low-Temperature Corrosion on External Surfaces.- 14-4 Corrosion and Scaling of Internal Surfaces.- 14-5 Fouling and Slagging.- 14-6 Calculation of Soot and Ash Deposition.- 14-7 Prediction of Slagging Potential.- 14-8 Design Measure for Reduction of Fouling and Slagging.- Nomenclature.- References.- 15 Erosion Prevention in Boilers.- 15-1 Theory of Erosion of Heating Surfaces.- 15-2 Worked-Out Example.- 15-3 Factors Influencing Tube Erosion.- 15-4 Analyses of Erosion of Tube Banks in Cross-Flow.- 15-5 Permissible Gas Velocity for Safe Operation.- 15-6 Erosion Protection for the Economizer, Reheater, and Superheater.- 15-7 Erosion in Tubular Air Heaters.- 15-8 Erosion in Fluidized Bed Boilers.- Nomenclature.- References.- 16 Pressure Drop in Gas and Air Ducts.- 16-1 Draft Systems.- 16-2 Pressure Drop in Air and Gas Duct Systems.- 16-3 Pressure Drop Across Heating Surfaces.- 16-4 Pressure Drop in Natural Draft Gas Path.- 16-5 Pressure Drop Through Air Ducts.- 16-6 Selection of Fans.- 16-7 Pressure Drop Through Water or Steam Tubes.- Nomenclature.- References.- 17 Mechanical Design of Pressure Parts.- 17-1 Selection of Materials.- 17-2 Important Mechanical Properties of Various Materials.- 17-3 Fundamental Metallurgical Concepts to Improve Steel Properties.- 17-4 Design Methods.- 17-5 Thickness (Scantling) Calculations.- Nomenclature.- References.- 18 Tables of Design Data.- Table 18-1 Specific heat of air, flue gas and ash at atmospheric pressure.- Table 18-2 Some physical properties of iron, metal, and selected steels.- Table 18-3 Linear thermal expansion of steel.- Table 18-4 Specific heat capacity of steel.- Table 18-5 Electrical resistivity of steel.- Table 18-6 Thermal conductivity of steel.- Table 18-7 Density, heat capacity, and heat conductivity for metals.- Table 18-8 Thermal properties of the saturated water and steam (arranged by temperature).- Table 18-9 Thermal properties of the saturated water and steam (arranged by pressure).- Table 18-10 Thermal properties of unsaturated water and superheated steam at different pressures.- Table 18-11 Conversion factors.

Boilers and burners : design and theory

A tomography system is presented that uses wavelength-scanned direct absorption of two transitions of a target species (NH3 in the demonstration experiment) to determine the distributions of gas concentration and temperature. The absorption measurements are performed simultaneously from four platforms that each rotate a beam from a single laser through an 11° arc, acquiring a data set from all four laser platforms in 100 ms to enable observation of dynamic flow events. The laser is wavelength scanned through two absorption transitions with different internal energy producing two sets of equations with species mole fraction and temperature as independent variables. The mole fraction and temperature distributions are reconstructed using the algebraic reconstruction technique (ART) for this set of incomplete projections. A numerical simulation is used to evaluate the measurement accuracy for measurements of an NH3 mixture escaping from an open pipe. This phantom distribution is then realized in the laboratory and the measurement strategy is demonstrated using a tunable diode laser absorption spectroscopy (TDLAS) measurement using a single laser near 1.5 µm to scan adjacent transitions in NH3. The reconstruction of NH3 concentration and gas temperature is compared with independently determined values to illustrate the fidelity of the tomographically reconstructed distributions for the NH3 mole fraction assuming a fixed temperature and for unknown mole fraction and temperature. Potential extensions of this research in the future include evaluation of other reconstruction algorithms and investigation of the dynamic distribution of various gases for combustion diagnostics.

https://iopscience.iop.org/article/10.1088/0957-0233/21/4/045301/pdf

Two-dimensional tomography for gas concentration and temperature distributions based on tunable diode laser absorption spectroscopy

Reconstruction of soot temperature and volume fraction profiles of an asymmetric flame using stereoscopic tomography

NOx emissions from power plants pose terrible threat to the surrounding environment. The aim of this work is to achieve low NOx emissions form a coal-fired utility boiler by using combustion optimization. Support vector regression (SVR) was proposed in the first stage to model the relation between NOx emissions and operational parameters of the utility boiler. The grid search method, by comparing with GA, was preferably chosen as the approach for the selection of SVR's parameters. A mass of NOx emissions data from the utility boiler was employed to build the SVR model. The predicted NOx emissions from SVR model were in good agreement with the measured. In the second stage, two variants of ant colony optimization (ACO) as well as genetic algorithm (GA) and particle swarm optimization (PSO) were employed to find the optimum operating parameters to reduce the NOx emissions. The results show that the hybrid algorithm by combining SVR and optimization algorithms with the exception of PSO can effectively reduce NOx emissions of the coal-fired utility boiler below the legislation requirement of China. Comparison among various algorithms shows the performance of the well-designed ACO outperforms those of classical GA and PSO in terms of the quality of solution and the convergence rate.

Kefa Cen

Papers

Full-scale solutions to particle-laden flows: Multidirect forcing and immersed boundary method

Boilers and burners : design and theory

Two-dimensional tomography for gas concentration and temperature distributions based on tunable diode laser absorption spectroscopy

Reconstruction of soot temperature and volume fraction profiles of an asymmetric flame using stereoscopic tomography

A comparative study of optimization algorithms for low NOx combustion modification at a coal-fired utility boiler