Primary Air Supply Research Articles

Effect of fuel layer mixing in waste bed combustion

A computational model was introduced to study the effect of fuel mixing in waste bed combustion in municipal solid waste incinerators. One-dimensional progress of the apparent flame zone into the bed was simulated by accommodating the heat and mass transfer, along with heterogeneous combustion and gaseous reactions in the waste bed. Mixing of the waste bed was modeled as an exchange of certain sections in the fuel layer from a cold region over a flame region. Combustion characteristics of the waste bed based on the model prediction are discussed, along with the experimental measurement results from a batch-type bed reactor. The computational model adequately described the heat transfer of the unburned fuel section over the existing flame zone. Improvement of the combustion intensity by fuel mixing was observed, as evidenced by a decrease in the required time for complete burn-out. Control of the primary air supply could further enhance the waste combustion, which is a common practice in commercial incinerators.

Flowrate quantification of the pumped-air stream from a 63 mm diameter centrifugal wheel atomiser

The air-pumping characteristic of a 63 mm diam centrifugal atomiser running dry within a cocurrent spray dryer was studied extensively using a novel experimental technique which involved the direct measurement of the wheel vacuum pressure together with the power required to pump the air. Approximately 10% of the power consumed by the atomiser was utilised in pumping the airstream. A further 25% was consumed in shearing the air around the wheel and the remaining 65% was consumed by friction and motor losses within the drive train. Typically, the wheels considered pumped between 2 l s −1 and 6.5 l s −1 of air at a maximum rotational speed of 50 000 rpm which corresponded to between 5% and 16% of the primary air supply to the dryer. A dynamic closure of the wheel/atomiser body gap was observed occurring at 30 000 rpm to 40 000 rpm which was thought to be due to an upward acting force generated by the pressure differential either side of the wheel. This significantly affected the air-pumping behaviour of the wheel.

Measurements of Oxygen Concentration of Air Within Totally Encapsulating Chemical-Protective Suits

This study measured oxygen concentrations of air within totally encapsulating chemical-protective (TECP) suits during simulated hazardous materials emergency response operations. This was done to allow assessment of the suitability of use of air within TECP suits as an emergency air supply during escapes from contaminated areas following loss of primary air supply. Samples of air were extracted through a probe installed in TECP suits while the suits were worn during simulated hazardous materials control operations. Data on oxygen concentration were obtained using direct reading equipment and through Orsat analysis of samples. Results indicate that the air within a TECP suit becomes significantly oxygen-deficient soon after the suit is closed, but generally maintains oxygen concentrations somewhat above those known to produce significant physiological effects. However, due to the further reduction of oxygen content inherent in breathing the air within TECP suits, it is anticipated that symptoms of oxygen deficiency sufficient to impair escape could be experienced in some instances. Recommendations are made for modifying current training practices to better prepare personnel working in Level A chemical-protective ensembles to cope with loss of air supply.

The study on the combustion model and combustion characteristics for stoker type incinerator

A combustion model for the incineration of municipal solid waste(MSW) in the stoker type incinerator was developed by considering the variation of physical composition of MSW. Theoretical analysis and numerical simulation for the combustion characteristics in incinerator were conducted by using the present model and the effects of compositional variation on the incineration characteristics of MSW was examined theoretically. It is found that large excess air enhances drying, but depresses volatilization. For the large value of moisture content, pyrolysis is fast but drying is slow. As the value of plastic content increases, devolatilization becomes slower. Larger amount of primary air supply to the rear side of stoker leads to increase the possibility of delaying the combustion.

Influence of combustion conditions on dioxin in an industrial-scale fluidized-bed incinerator: experimental study and statistical modelling

A series of tests has been performed in a full-scale fluidized-bed waste incinerator to study the formation of dioxins and to find the optimal operating conditions for minimizing dioxin emissions. The incineration process parameters and dioxin emissions are measured under different operating conditions. The experimental data are then subject to a statistical analysis using the simple and multiple regression analysis methods. It is found that the dioxin formation level in the plant can be approximately represented by the dioxin measurements at boiler outlet and is mainly influenced by combustion conditions. Higher flue gas O 2 level, secondary to primary air ratio and total air supply are favourable for lower dioxin formation. Lime and ammonia injections, however, appear to have only minor effects on dioxins.

Aerosol Characterization of a Smoldering Source

The aerosol emitted by a moderately large smoldering combustion source (16 cm in diameter) has been characterized in detail. The fuel is a permeable bed of cellulosic insulation (wood fibers) receiving its primary air supply by flow up from the bottom of the bed while the smolder wave propagates downward. The mass mean particle size of the aerosol is 2–3 μm; this shows no clear trend with smolder wave depth in the bed or with air flow velocity. The large average particle size is shown to imply that, compared to punk smoke, the present aerosol requires a sevenfold greater concentration to trigger an ionization detector. Coagulation of the aerosol in the plume above the source is shown to be minimal, but substantial coagulation can occur within the source. The apparent fractional conversion of gasified mass (60–75% of the fuel) to aerosol mass decreases with smolder wave depth in the bed and with decreasing air flow rate. The mass and number flow rate of the aerosol show these same trends. The decreasing ae...

Fuel economy in steam power plants

Introduction. Feed-water: Analysis?Systematic control of supplies?Softening?Scale and grease troubles?Preheating?Thermal Storage. Fuel: Sampling?Testing?Systematic control of supplies?Suitability for boiler-furnace. Air: Preheating primary and secondary air supply. Boilers and Furnaces: Types of?Setting?Hand-firing v. mechanical stoking?Losses by radiation and air-leakage?Smoke prevention. Steam: Superheating?Condensation and radiation losses. Waste Gases: Heat losses in?Sampling?Testing?Systematic control of. Draught and Regulation of Air Supplies: Natural v. artificial graught.