Influence of Preparation and Combustion Parameters of Coal-water Slurries on Gas Emission Chemistry

The article presents the results of experimental studies performed for the comparative analysis of factors affecting the concentration of the main gas emissions during the combustion of fuel suspensions obtained from coal enrichment waste. The factors influencing the formation of anthropogenic emissions during the flaring of coal-water fuel suspensions were investigated. Experiments were carried out with coal processing waste, both with and without additives in the form of spent mineral oil. The article shows how the concentration of sulfur dioxide, nitrogen dioxide, and hydrocarbons is affected by the parameters of preparation (particle size, solid-liquid phase ratio, additives of used engine oil) and combustion (temperature in the combustion chamber, excess air coefficient, and droplet size after spraying) of fuel suspensions.

Computational modeling of flow field in boiler before and after urea injection under different conditions

In order to achieve ultra-low NOx emissions, the effects of total excess air coefficient, air coefficient in main combustion zone, blended-coal combustion and ammonia nitrogen molar ratio on a 330 MW coal-fired boiler combustion were studied by numerical simulation. The results show that the velocity field and temperature field in the furnace have synergy, the better the synergy is, the faster the temperature rises, and the more NOx it generates. Compared before and after urea spraying, the NOx concentration decreased with the decrease of the total excess air coefficient, the optimum total excess air coefficient is about 1.15, and the denitrification rate is as high as 76.2%. The smaller the air coefficient in the main combustion zone is, the smaller the NOx concentration is. The optimum air coefficient in the main combustion zone is about 0.92, and the denitrification rate is 85%. After urea injection, the denitrification rate of high volatile coal combustion is higher than that of low volatile coal combustion, and the reasonable blending mode of coal can reduce NOx emissions. The larger the ammonia-nitrogen molar ratio is, the lower the NOx concentration is. When the ammonia-nitrogen molar ratio is greater than 2, the amount of ammonia escape at the flue outlet exceeds the standard. When the ammonia-nitrogen molar ratio is less than 1, the NOx concentration at the flue outlet is greater than that before urea injection. The optimal ammonia-nitrogen molar ratio is about 2.

Modeling of the Thermal Efficiency of a Whole Cement Clinker Calcination System and Its Application on a 5000 MT/D Production Line

This paper proposes that the scope of research should be extended to the whole clinker calcination system from its single device or specific process (i.e., its functional subunits) as conventionally conducted. Mass/heat flow and effective heat were first analyzed to obtain the thermal efficiencies of its subunits (φi); a thermal efficiency model of the whole system φQY was thus established by correlating the relationship between φi and φQY. The thermal efficiency model of the whole system showed that φi had a positive linear correlation with φQY; it was found that the thermal efficiency of the decomposition and clinker calcination unit (φDC) had the greatest weight on φQY, where a 1% increase in φDC led to a 1.73% increase in φQY—improving φDC was shown to be the most effective way to improve φQY. In this paper, the developed thermal efficiency model was applied to one 5000 MT/D production line. It was found that its φQY was only 61.70%—about 2.35% lower than a representative line; such decrease was caused by its low φDC and φP which, as disclosed by model, were derived from the low decomposition rate of calcium carbonate in preheated meal put into a calciner and the high excess air coefficient of secondary air. Controlled parameter optimization of this 5000 MT/D production line was then carried out. As a result, the φDC and φP of the production line were increased from 30.03% and 64.61% to 30.69% and 65.69%, respectively; the φQY increased from 61.70% to 62.55%; the clinker output of the production line increased from 5799 MT/D to 5968 MT/D; the heat consumption of clinker was reduced from 3286.98 kJ/kg·cl to 3252.41 kJ/kg·cl.

Effect Analysis on Combustion and Emission Characteristics of a Rotary Burner Fueled by Biomass Pellet Fuel

A biomass pellet rotary burner was chosen as the research object, in order to study the influence of excess air coefficient on the combustion phenomenon of biomass rotary burner, the finite element simulation model of a biomass rotary burner was established, and simulation results of a biomass rotary burner were verified by the experiment. The computational fluid dynamics software was applied to simulate the combustion characteristics of biomass rotary burner in a steady-state condition, and the effect of excess air coefficient on temperature field and component concentration field in biomass rotary burner was analyzed. The results show that the flue gas flow rate inside the burner gradually increases with the increase of air velocity, the area with large temperature is mainly concentrated in the middle region of the rotary burner, and the maximum combustion temperature also appeared in the middle region of the combustion chamber, and the formation area of CO decreases with the increase of excess air coefficient. CO2 is mainly concentrated in the middle region of the burner, and the CO2 generating region decreases with the increase of excess air coefficient. The experimental value of the combustion temperature of the biomass rotary burner is in good agreement with the simulation results.

Numerical investigation of lambda-value prechamber ignition in heavy duty natural gas engine

Turbulent Jet Ignition systems are mainly dedicated to the combustion of lean mixtures of natural gas in heavy duty engines. The use of such a system in combination with lean mixtures leads to an increase in its overall efficiency. The article presents simulation analyzes of the impact of the excess air coefficient occurring in prechamber on the combustion process: combustion indicators and emission indicators. Tests on a single-cylinder engine with a displacement of about 4 dm3 at medium mixture (IMEP = 1.0 MPa) were carried out using the AVL Fire software. It was found that the incineration of global lean mixtures (lambda = 2) is effective when initiating this process (in the prechamber) with a charge of a stoichiometric composition. A strong relationship was found between the thermodynamic indicators in both prechamber and main chamber and the excess air coefficient initiating combustion.