Particulate matter (PM) emissions from stationary combustion sources burning coal, fuel oil, biomass, and waste, and PM from internal combustion (IC) engines burning gasoline and diesel, are a significant source of primary particles smaller than 2.5 μm (PM2.5) in urban areas. Combustion-generated particles are generally smaller than geologically produced dust and have unique chemical composition and morphology. The fundamental processes affecting formation of combustion PM and the emission characteristics of important applications are reviewed. Particles containing transition metals, ultrafine particles, and soot are emphasized because these types of particles have been studied extensively, and their emissions are controlled by the fuel composition and the oxidant-tem-perature-mixing history from the flame to the stack. There is a need for better integration of the combustion, air pollution control, atmospheric chemistry, and inhalation health research communities. Epidemiology has demonstrated t...

https://www.tandfonline.com/doi/pdf/10.1080/10473289.2000.10464197

Combustion aerosols: factors governing their size and composition and implications to human health.

A review of the technologies for coal-based power generation closest to commercial application involving carbon capture is presented. Carbon capture and storage (CCS) developments are primarily adaptations of conventional combustion systems, with additional unit operations such as bulk oxygen supply, CO2 capture by sorbents, CO2 compression, and storage. They use pulverized coal combustion in entrained flow—the dominant current technology for coal-based power, or gasification in entrained flow, although similar concepts apply to other solid–gas contacting systems such as fluidized beds. Currently, the technologies have similar generation efficiencies and are associated with efficiency penalties and electricity cost increases due to operations required for carbon capture. The R&D challenges identified for the combustion scientist and engineer, with current understanding being detailed, are those of design, optimisation and operational aspects of new combustion and gasification plant, controlling the gas quality required by CCS related units and associated emission compliance, and gas separations. Fundamental research needs include fuel reactions at pressure, and in O2/CO2 atmospheres, as few studies have been made in this area. Laboratory results interpreted and then included in CFD models of combustion operations are necessary. Also identified, but not detailed, are combustion issues in gas turbines for IGCC and IGCC-CCS. Fundamental studies should be a component of pilot-plant and demonstrations at practical scale being planned. Concepts for new designs of combustion equipment are also necessary for the next generation of technologies. The challenges involved with the design and operation of these integrated systems, while supplying electricity on demand, are considerable.

Combustion processes for carbon capture

Influence of pyrolysis conditions on the structure and gasification reactivity of biomass chars

Formation of the structure of chars during devolatilization of pulverized coal and its thermoproperties: A review

Ash formation and deposition in coal and biomass fired combustion systems: Progress and challenges in the field of ash particle sticking and rebound behavior

The porous structure of bituminous coal chars and its influence on combustion and gasification under chemically controlled conditions

A 63−90 μm size fraction of an Australian bituminous coal sample was fed into a drop tube furnace (DTF) and a pressurized drop tube furnace (PDTF) to generate chars. A gas temperature of 1573 K and system pressures of 0.1, 0.5, 1.0, and 1.5 MPa were considered. Particle size analysis, scanning electron microscopy (SEM), and image analysis were employed to analyze the chars produced in order to investigate the effect of system pressure on the resultant char structure and morphology. The char character was found to be influenced significantly by the system pressure. Results obtained indicated that the coal and char fragmentation might have occurred during devolatilization at high pressure. The char size (as characterized by the swelling ratio) was also observed to increase with system pressure. The cross-sectional characterization of the char particles indicated that at high pressure the majority of the char particles are of high porosity with thin walls or network (the group I type) rather than of medium p...

An experimental study on the effect of system pressure on char structure of an Australian bituminous coal

Chars were made from four Australian coals of varying vitrinite content at pressures of 5, 10, and 15 atm. The morphology of the chars was correlated with the petrography of the parent coal. The intrinsic reaction rates of the chars at high pressures were measured, and no systematic effect of pyrolysis pressure or maceral concentration was found. It is concluded that observed variations in conversion rates under process conditions are likely to be due to char structural properties and not a result of variation in the intrinsic reactivity of the carbon in the chars. Consequently, this paper presents a char structural submodel that is integrated into an existing char combustion model to account for the combustion behavior of char particles of different morphologies. The char morphology used in the model was predicted using the developed correlation with parent coal petrography, so that a petrographic analysis as well as the proximate and ultimate analyses is required for model input. Validation of the model shows that chars produced at high pressure with a high percentage of cenospherical types burn more rapidly under process conditions than those at low pressure, with model predictions matching measurements. It is suggested that incorporating the char structural submodel into the existing char combustion model improves its predictability.

Kathy E. Benfell

Papers

The porous structure of bituminous coal chars and its influence on combustion and gasification under chemically controlled conditions

An experimental study on the effect of system pressure on char structure of an Australian bituminous coal

Modeling char combustion: The influence of parent coal petrography and pyrolysis pressure on the structure and intrinsic reactivity of its char