Ali Ergut

Cryogenic extinguishment of liquid pool fires

Results on fire extinguishment using direct application of liquid nitrogen are presented in this article. This technique targets challenging fires, such as burning hazardous chemicals or fuels, in which cases prompt suppression or extinguishment is paramount to prevent explosions, avoid release of toxic fumes and avert environmental catastrophes. Liquid nitrogen is a rather environmentally benign extinguishing agent that does not cause property damage or groundwater contamination. Application of this cryogen onto a hot pyrolyzing/burning surface induces abrupt vaporization, spread and expansion. The pyrolyzing gases are inerted, the surface is cooled and hence its pyrolysis rate is reduced, air is separated from the fuel, and the fire extinguishes. To demonstrate this technique, experiments were conducted with pool fires of ethanol, propanol, and diesel fuel. To examine the underlying principles, analysis of the results was conducted based on simplified calculations. Sufficient quantities of the cryogen extinguished the fires nearly instantaneously. Half‐liter quantities were sufficient to extinguish 1 m2 pool fires. The method of dispensing and distributing the cryogen on the pool fires proved to be of considerable importance. The existence of wind, which disturbed the flame, was not found to prevent extinguishment.

Economics of an Integrated Approach to Control SO2, NOx, HCl, and Particulate Emissions from Power Plants

Abstract An integrated approach for the simultaneous reduction of major combustion-generated pollutants from power plants is presented along with a simplified economic analysis. With this technology, the synergistic effects of high-temperature sorbent/coal or sorbent/natural gas injection and high-temperature flue gas filtration are exploited. Calcium-based (or Na-based, etc.) sorbents are sprayed in the post-flame zone of a furnace, where they react with S- and Cl-containing gases to form stable salts of Ca (or Na, etc.). The partially reacted sorbent is then collected in a high-temperature ceramic filter, which is placed downstream of the sorbent injection point, where it further reacts for a prolonged period of time. With this technique, both the likelihood of contact and the length of time of contact between the solid sorbent particles and the gaseous pollutants increase, because reaction takes place both in the furnace upstream of the filter and inside the filter itself. Hence, the sorbent utilization increases significantly. Several pollutants, such as SO2, H2S, HCl, and particulate (soot, ash, and tar), may be partially removed from the effluent. The organic content of the sorbents (or blends) also pyrolyzes and reduces NOx. Unburned carbon in the ash may be completely oxidized in the filter. The filter is cleaned periodically with aerodynamic regeneration (back pulsing) without interrupting furnace operation. The effectiveness of this technique has been shown in laboratory-scale experiments using either rather costly carboxylic salts of Ca or low- to moderate-cost blends of limestone, lime, or sodium bicarbonate with coal fines. Injection occurred in the furnace at 1150 °C, while the filter was maintained at 600 °C. Results showed that 65 or 40% SO2 removal was obtained with calcium formate or a limestone/coal blend, respectively, at an entering calcium-to-sulfur molar ratio of 2. A sodium bicarbonate/coal blend resulted in 78% SO2 removal at a sodium-to-sulfur molar ratio of 2. HCl removal efficiencies have been shown to be higher than those for SO2. NOx reductions of 40% have been observed with a fuel (coal)-to-air equivalence ratio, π, around 2. The filter has been shown to be 97–99% efficient in removing PM2.5 particulates. Calculations herein show that this integrated sorbent/filter method is costeffective, in comparison with current technologies, on both capital cost (

EXPERIMENTAL AND NUMERICAL STUDY OF EMISSIONS FROM FUEL-RICH COMBUSTION OF PULVERIZED POLYSTYRENE

/kW) and levelized cost (

An Investigation on Thermocouple-Based Temperature Measurements in Sooting Flames

/ton pollutant removed) bases, if a limestone/coal mixture is used as the sorbent for fossil fuel plants. Capital costs for the filter/sorbent combination are estimated to be in the range of

A Low Emission Power Plant: An Integrated Technique to Remove Major Pollutants

61–

PAH formation in one-dimensional premixed fuel-rich atmospheric pressure ethylbenzene and ethyl alcohol flames

105/kW for a new plant. Because current technologies are designed for removing one pollutant at a time, both their cost and space requirements are higher than those of this integrated technique. At the minimum projected removal efficiencies for HCl/SO2/NOx of about 40%, the levelized costs are projected to be

The effect of equivalence ratio on the soot onset chemistry in one-dimensional, atmospheric-pressure, premixed ethylbenzene flames

203–

Investigation of critical equivalence ratio and chemical speciation in flames of ethylbenzene-ethanol blends

261/ton of combined pollutant SO2/HCl/NOx and particulates removed from coalfired power plants.

The effect of temperature on the soot onset chemistry in one-dimensional, atmospheric-pressure, premixed ethylbenzene flames

This is an investigation on the formation of products of incomplete combustion (PIC) of waste poly(styrene) (PS). Pulverized PS was steadily injected into an externally-heated drop-tube laboratory furnace and burned therein in fuel-rich conditions, corresponding to a bulk equivalence ratio of approximately 2.5. Iso-kinetic and iso-axial sampling with a probe was performed at five different heights along the centerline of the furnace. The goal has been to investigate the evolution of fixed product gases, unburned light volatile organic compounds (VOC) and semi-volatile organic compounds (SVOC), with emphasis to polycyclic aromatic hydrocarbons (PAH), along the reaction zone of the furnace. The magnitude of species therein and their respective trends were assessed. The centerline gas temperature was measured by suction thermometry. Moreover, the flow field and gas temperature distribution in the furnace were computed with a 3-dimensional model using the CFD code Fluent. Results showed that of the measured light VOC, acetylene exhibited the highest yields in the combustion effluent, followed by methane, ethylene and benzene. These yields were comparable to those of the most prevalent PAH species. PAH profiles varied somewhat in the sampling zone, with yields spanning the range between 13.8 mg (naphthalene) and 0.058 mg (perylene) per each gram of polystyrene burned. The results for fixed exhaust gases showed an increase in CO values with distance traveled, from 85 to 175 mg whereas CO2 stayed close to 1000 mg, per gram of PS burned. Oxygen remained somewhat steady near 85 mg/g PS burned. Copious amounts of soot were generated and collected through the probe, 0.25–0.42 g for each gram of PS burned. Computations were conducted using a detailed chemical kinetic model, allowing for the prediction of formation and depletion of major PAH and soot particles of different sizes. In this computation styrene was input as the fuel. In comparing experimental hydrocarbon species concentrations to theoretical predictions, a large number of species were found to be within a factor of 7 or less.

Emissions from the combustion of polystyrene, styrene and ethylbenzene under diverse conditions

Temperature is an important parameter in flame chemical structure calculations. However, accurate temperature measurements are challenging to obtain. This manuscript reports on temperature measurements in sooting ethyl-benzene flames. Measurements were conducted with an array of four decreasing size thermocouples. However, to minimize disturbance of the flame by the insertion of the insulated multi-thermocouple array, the four thermocouples were also inserted bare one at a time, and results were contrasted. In both cases, radiative heat transfer was accounted for by using the well-known Nichols method [1]. This method was somewhat modified, as the extrapolation to zero thermocouple bead size was done using third-order polynomials. Furthermore, as soot accumulates on the thermocouple beads, upon their insertion in sooting flames, the obtained signals were scrutinized to determine the point in their time-history that is appropriate for this analysis. The zero time extrapolation technique, as suggested by McEnally et al. [2], was used to correct for soot accumulation at the tip of the thermocouples. Other methods were also explored, where theoretical expressions were used with corrections applied for the radiative heat losses from the thermocouples either prior or after the accumulation of soot on the thermocouple bead. Results showed that higher temperatures were recorded when single bare thermocouples were inserted into the flame as compared to inserting four thermocouples together. The difference was attributed to the disturbance of the flow-and temperature-fields in the flame, especially by the ceramic sheath that holds thermocouples together, and the thermal interaction of the thermocouples when they were inserted into the flame simultaneously. Results also showed that a combination of modified Nichols’ method with McEnallys’ corrections for sooting flames is a preferred technique as it nearly eliminates assumptions. Resulting temperature values are supported by theoretical calculations with judicious assumptions on important parameters.Copyright