sample="quota" bates="514927939" isource="rjr" decade="1980" class="ui" date="19870429" International Conference On The Physical And Chemical Processes Occurring In A Burning Cigarette April 26-29, 1987 Graylyn Conference Center of Wake Forest University Winston-Salem, NC USA Sponsored by R. J. Reynolds Tobacco Co. INTERNATIONAL CONFERENCE ON THE PHYSICAL AND CHEMICAL PROCESSES OCCURRING IN A BURNING CIGARETTE ABSTRACTS CONFERENCE SESSION I STUDIES OF BURNING ZONE OF CIGARETTES Keynote Lecture: SOME BURNING PROBLEMS IN TOBACCO SCIENCE Richard R. Baker British American Tobacco (U.K. & Export) Limited Southampton, England The study of the science of cigarette burning processes begins with temperature measurements, since the formation of smoke products and the whole burning behaviour of the cigarette depends on burning zone temperatures and tobacco heating rate. A large number of studies have measured these parameters using a variety of techniques, including thermocouples, infra-red probes and infra-red cameras. Since the cigarette burning zone is a porous solid, the temperature distribution in two phases has to be measured: the solid and gas phases. These two phases are in near thermal equilibrium during the interpuff natural smoulder period, with the highest temperatures of around 800°C occurring in the centre of the zone. During puffing, the two phases have very different temperature distributions near the surface, although they are similar in the central regions (about 820-850ºC). Maximum solid-phase surface temperatures, up to 950°C, are observed on the burning zone periphery. Factors such as air influx and tobacco additives affect temperature and temperature gradients, and consequently such factors can have a significant effect on product formation. Gas velocities inside the cigarette burning zone can be calculated from pressure and temperature distributions, and local velocities as high as 400 cm s-1 occur during puffing. Thus residence times in the higher temperature regions of the cigarette are typically less than one millisecond. The high gas temperatures and velocities in the burning zone cause the characteristic increase in draw resistance of the cigarette when it is lit. This increase, and its subsequent variation during the smoking regime, has a direct influence on the amount of air drawn into the burning zone and subsequent combustion behavior and product formation. A series of studies has determined the regions inside the cigarette where products are released or formed. These studies have used small sampling probes inserted into the cigarette and connected directly to a mass spectrometer. The work has shown that the interior of the burning zone is oxygen deficient and hydrogen rich and can be effectively divided into two regions - an exothermic combustion zone and an endothermic pyrolysis/distillation zone. Oxygen-18 studies have shown that the oxides of carbon are formed in both zones. Semi-volatile components are, in general, released at temperatures between 300 and 600°C, although nicotine is released below 250°C. This is typically the region where aerosol phase is forming inside the cigarette. Similar probe studies have been conducted in the sidestream plume and temperature, gas concentrations and velocity profiles have been determined. Little change occurs to the sidestream temperature and oxygen distributions when a puff is taken, indicating that the natural convection stream around the burning zone is only slightly affected by the influx of air during the puff. The sidestream gases rise from the cigarette burning zone in a fairly well-defined column which centres at about 3 mm in front of the paper burn line. On the other hand, the visible sidestream smoke column originates some 0 to 4 mm behind the paper burn line, becoming visible at temperatures below about 150°C. Other processes occurring inside the cigarette such as gas diffusion and filtration of smoke particles have large effects on the final mainstream product levels. Relationships which include these mechanisms will be presented. Finally, as an indication of the complex inter-relationships of the dynamic processes occurring in the cigarette, the effect of ventilation on the various mechanisms will be presented. MEASUREMENT OF TEMPERATURE DISTRIBUTIONS OF CIGARETTE COALS BY INFRARED IMAGING RADIOMETRY Douglas D. McRae and R. W. Jenkins, Jr. Philip Morris Research Center Richmond, Virginia and J. S. Brenizer University of Virginia Charlottesville, Virginia There are a number of thermal imaging systems available commercially that will convert the image of a scene or objects as it appears in the infrared to a video signal that can be viewed on a television monitor. Since the infrared radiation emitted by an object is directly related to its temperature, one can, with reasonable care, use such an imaging system to measure temperature. This paper discusses the use of a thermal imaging system to measure the temperature distribution of a cigarette coal in real-time through the puffing cycle. The thermal camera was an Inframetrics Model 525 equipped with an 8-bit microprossor to produce an image with 256 brightness levels (grey scale) for detailed temperature measurements. A special close-up lens was used to produce a magnified image of the coal. The video equipment supporting the thermal camera included a video tape recorder to store images for later analysis, a video timer that placed the date and time on each video frame and several video monitors. In addition, a digital image processor was programmed to analyze the recorded infrared images to extract the temperature distributions. The image processor could also produce a false color image of the coal from the original black and white picture. The false color images are especially useful for observing the temperature contours. The image processing programs will be covered and discussed and preliminary results from the computer analysis will be presented. Previous studies have shown that menthol applied to tobacco unfiltered cigarettes migrates to the filter and vice versa. Furthermore, it is know that MS menthol delivery decreases with time parallel to this migration from rod to filter. Experiments designed to elucidate the mechanisms responsible for this decreased delivery showed that menthol in the filter is eluted less efficiently with increasing time due to absorption into the filter fibers. The age of the filter affected total menthol delivery but did not alter puff-by-puff delivery profiles. The age of tobacco rod had no effect on menthol delivery. In conclusion, the high volatility of menthol makes elution an important mechanism for menthol delivery and also causes rapid equilibration between rod and filter. This migration causes total menthol delivery to decrease with time due to absorption of the menthol by the filter fibers. CONFERENCE SESSION III PYROLYSIS STUDIES OF TOBACCO AND TOBACCO COMPONENTS Keynote Lecture: The Pyrolysis and Combustion of Cigarette Constituents Charles F. Cullis The City University London, England The mechanisms of the pyrolysis of polymeric materials generally are affected by various factors, including in particular the heating rate, the absence or presence of oxygen and the nature and concentration of any additives. This is especially true in the case of cellulose (an important constituent of tobacco and the predominant constituent of cigarette paper), where the precise kinetic relationships observed depend also on the physical condition of the sample and the nature and flow rate of the surrounding gaseous atmosphere. A description is therefore given of recent work on the pyrolysis and combustion of cellulose (both on its own and in contact with tobacco) under a wide range of experimental conditions designed to simulate as closely as possible those involved during the smoking of cigarettes. Special attention has been paid to the effects on the nature and distribution of the reaction products (particularly the carbon monoxide levels and tar and nicotine deliveries ) of very high linear heating rates ( up to 1200 deg s-1 and with final temperatures of up to 600-1300K), of the concentration of oxygen present and of a large number of inorganic salts and other additives. CONTRIBUTION OF FRACTIONATED TOBACCO EXTRACTS TO PYROLYTIC GAS PHASE CONSTITUENTS Harold R. Burton University of Kentucky Lexington, Kentucky There has been interest in the contribution of various tobacco constituents to the composition of cigarette smoke. A study was initiated to determine if the removal of soluble tobacco constituents by solvent extraction influenced the tar yield of 1R1 cigarettes. This study also included the extraction of 1R1 tobacco with acetone and fractionation of the extract into a non-polar, moderately polar and polar fraction. Differential thermogravimetry (DTG) of the non-fractionated and fractionated extracts revealed there were significant differences between the weight loss of these extracts. Temperature yield profiles for the gas phase constituents from these extracts were determined by pyrolysis gas chromatography (PGC) and by DTA. The fractionated extracts in various concentrations were added to blended tobacco and cigarettes were manufactured from these modified tobaccos. Data will be presented for smoke analyses, DTG and PGC. PYROLYSIS OF BULK SAMPLES OF CELLULOSE Merwin Sibulkin Brown University Providence, Rhode Island The investigation of flaming combustion of fuels can usefully be divided into studies of gas-phase diffusion flames and solid-phase pyrolysis. In this paper we examine the pyrolysis of cellulose do determine its rate of gasification and heat of gasification (which is a quasi-property connecting the gas and solid phase processes). A theoretical analysis of the propagation of a one-dimensional pyrolysis wave into a bulk sample of cellulose is described. The results of numerical solutions of the governing equations are discussed with emphasis on the effects of variations in the material properties. It is found that the char density and thermal conductivity have a strong effect on total pyrolysis rate while the specific reaction rate has a weaker effect. A new experimental set-up for studying bulk pyrolysis in an inert atmosphere is described, and some of the problems encountered are discussed. Measurements of pyrolysis rate and heat of gasification are presented for both pure cellulose and cellulose with a fire-retardant additive. The theoretical and experimental results are compared, and the role of the additive is discussed. (iii) During the evaporation period, for a given humidity, the ration of glycerol to water in a droplet remains constant and is equal to that at the maximum size. The evaporation behavior of the droplet is identical to that of a single component droplet (i.e., the square of the droplet diameter changes linearly with time). SMOKE PARTICLES PRODUCED FROM TOBACCO CELL WALL COMPONENTS Yoshiaki Ishizu, Kazuyo Kaneki, And Takeshi Sakaki Japan Tobacco Inc. Yokohama, Japan Smoke particle production from each tobacco cell wall component was investigated. Four major components of cell wall, -celulose, hemicellulose, lignin and pectin, were isolated from cured tobacco leaves. They were heated in a thermobalance in the atmospheres of air and helium, at the heating rates of 10ºC/mind and 240ºC/ min. The sizes and the weights of the produced smoke particles and the weight losses of the samples were measured simultaneously. The median curves of the smoke particle sizes from -cellulose, hemicellulose and pectin. showed similar curve patterns of the production rate. It was shown that the smoke particle sizes from them correlated to their particle concentrations. -Cellulose and lignin could produce more smoke particles than hemicellulose and pectin. Under similar conditions to a burning cigarette, in helium and at 240ºC/min, the total weights of smoke particles per 1mg of the samples were 0.32mg for -cellulose, 0.24mg for lignin, 0.03mg for hemicellulose and 0.004mg for pectin. -Cellulose, the largest component in tobacco cell wall, had the highest smoke particle producing rate. It can be concluded that cellulose contributes the most to smoke production of a burning cigarette. COAGULATION AND FILTRATION OF MAINSTREAM CIGARETTE SMOKE IN THE TOBACCO ROD OF A CIGARETTE David W. Boldridge and Bradley J. Ingebrethsen R. J. Reynolds Tobacco Company Winston-Salem, North Carolina Mainstream cigarette smoke is a highly concentrated aerosol that undergoes both coagulation and filtration as it travels through a tobacco rod. Measurements of the particle size distribution and number concentration of mainstream smoke were made during a puff for a series of tobacco rod lengths. A model was developed which predicts the changes in the cigarette smoke aerosol as it travels through a length of tobacco rod. The model is based on simple equations for filtration and coagulation of aerosols. The experimental apparatus used in this work measures the particle size distribution of a fresh, undiluted sample of mainstream smoke by ensemble light scattering. Five detectors placed at 30ºC, 60º, 90º, 120º, and 150º relative to the interrogating laser beam (Argon ion, 514 nm) measure the scattered light intensity. Ratios of these intensities (relative to the intensity at 90º) are compared to tabulations of Mie scattering values for log-normally distributed aerosols with a refractive index of 1.54-0.0i to obtain best-fit values of the geometric mean diameter and geometric standard deviation. The number density is obtained from the absolute scattering intensity and the theoretical scattering efficiency at 90º and the gravimetrically determined wet total particulate matter for each puff. The measurement is repeated every 20 ms to determine the time resolved profile during the two-second puff. Data were acquired for the second puff on tobacco rods ranging from 49 mm to 119 mm in length. Details of the experimental procedure have been presented elsewhere. (Ingebrethsen, 1986) The model uses an initial set of experimentally determined size distribution and number density parameters as input data. The only other input parameters are the physical characteristics of the tobacco rod (cross-sectional area, void volume, tobacco rod length, effective fiber diameter, etc.) and the smoke flow rate. The effective fiber diameter was determined from the relationship of pressure drop to flow rate. The evolution of the size distribution and number density is predicted by calculating the filtration and coagulation of the initial aerosol as it travels through the tobacco rod. The filtration model was constructed using single fiber filtration equations (Hinds, 1982) and the coagulation model was built around analytical expressions for Brownian coagulation in the continuum regime (Lee, 1983). Log-normal aerosol distributions were assumed throughout the model. The mean mass diameter becomes larger as the length of the tobacco rod increases, while the number density decreases dramatically. The predicted values of the mean mass diameter and the number density are in good agreement with experimentally determined values.