Agglomeration Of Coal Particles Research Articles

Particle size grouping method as a control system of efficiency flotation process on the example of coal

Agglomeration of coal particles during flotation can be analysed with the Particle Size Grouping (PSG) method. Numerous experiments were carried out to theoretically explain the effect of carbon particles agglomeration, but the result still remains incomplete. In this paper the PSG method was used to analyse agglomeration groups of carbon particles of initial size 100-400 ?m, maintaining the total particle volume. The size of particles population with definite radius and density was determined for 1 Mg coal. The influence of density and size of particles with given mixing energies and parameter ? on agglomeration was analysed. It was stated that the size of the particles had an effect on their agglomeration. In the analysed cases the dimensionless parameter of collision turbulence t* needed for particles agglomeration in particular size groups was importantly shorter for particles of initial size 300 and 400 ?m. The change of the mixing energy did not have influence on the agglomeration of coal particles. The theoretical analyses based on computer calculations were supplemented by the analyses of the coal flotation process on an aqueous model. Experiments lied in introducing a foaming agent in the form of aqueous solution of hexanol which, without changing pH of the pulp, lowered surface tension value, and consequently increased the dispersion of air in the suspension. The experimental results were presented in the form of flotation kinetics curves. Fine particles 100-200?m. turned out to be best for flotation, unlike coarse 400-500 ?m.

Obtaining of gas, liquid, and upgraded solid fuel from brown coals in supercritical water

Two new conversion methods of brown coals in water steam and supercritical water (SCW) are proposed and investigated. In the first method, water steam or SCW is supplied periodically into the array of coal particles and then is ejected from the reactor along with dissolved conversion products. The second method includes the continuous supply of water-coal suspension (WCS) into the vertically arranged reactor from above. When using the proposed methods, agglomeration of coal particles is excluded and a high degree of conversion of coal into liquid and gaseous products is provided. Due to the removal of the main mass of oxygen during conversion in the composition of CO2, the high heating value of fuels obtained from liquid substantially exceeds this characteristic of starting coal. More than half of the sulfur atoms transfer into H2S during the SCW conversion already at a temperature lower than 450°C.

Zeta potential of a subbituminous coal and its effect on particle agglomeration

The objectives of this investigation were to study the zeta potential characteristics of a Powder River Basin coal in water and to study the effects of zeta potential on the agglomeration of coal particles. The electrokinetic measurements show that the zeta potential of the coal is dependent on pH, temperature, coal concentration and contact time with water. The effects of various additives for changing the zeta potential of the coal were also evaluated. It was found that the strength of the coal agglomerates is increased when the zeta potential diminishes. Neutralizing the zeta potential enhances agglomeration. Therefore, it is important to control the zeta potential of coal to achieve optimum performance in coal-particle agglomeration.

流動層加熱における石炭粒子の凝集

流動層加熱における石炭粒子の凝集

The mechanism of combustion of coal-water slurries

The combustion of coal-water slurries has been investigated using suspended and falling droplet techniques. Measurements have eeen made of ignition delays, mass loss and temperature rise for a range of coals with differing coal particle sizes and slurry preheat temperatures. Ignition delays have been shown to be a function of water content and its initial temperature, coal type and particle size. It was observed that in the majority of cases ignition was followed by agglomeration of coal particles so that its subsequent behaviour was determined by combustion of the agglomerated particle. Char combustion rates were determined and the results have been experessed in terms of burning rate constants suitable for use in practical situations. A simple theoretical model has been developed which represents the behaviour of a coal-water slurry of a bituminous non-swelling coal to a reasonable degree. The early stages involving heat-up, ignition and burning of the volatiles of the droplet are well reproduced by the model. Ignition occurs when sufficient water has been evaporated so that a layer of coal particles become immobile on the droplet surface. The subsequent char burning stage is moderately described by the model but an exact mechanism is difficult to define because of uncertainties arising from the open structure of the char produced from agglomerated coal particles.