Based on our results, we believe that ingestion of the recommended dose of sodium bicarbonate one-half teaspoon would result in only small amounts of sudden gas release, probably not enough to be an important factor in causing spontaneous gastric rupture. On the other hand, we measured the amount of sodium bicarbonate that people actually select to take for indigestion, and all exceeded the recommended dose.
Some people selected doses of bicarbonate that would result in several hundred milliliters of gas release within 3 min; it seems likely that such injudicious ingestion of sodium bicarbonate, if taken when the stomach was distended with air, food, and liquid, could be an important factor in spontaneous gastric rupture.
Abstract Ingestion of sodium bicarbonate has been implicated as one of the proximate causes of spontaneous gastric rupture.
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Email Required, but never shown. Featured on Meta. Now live: A fully responsive profile. Version labels for answers. Related 4. Hot Network Questions. Question feed. Chemistry Stack Exchange works best with JavaScript enabled. The removal of acid pollutants from flue gases is required in several industrial combustion processes. Hydrogen chloride HCl and sulfur dioxide SO 2 are formed in waste incineration and in a number of industrial processes involving combustion steelmaking, cement production, glassmaking ceramics manufacturing , whenever the fuel feed contains respectively chlorine or sulfur.
Among the different dry, semidry, and wet techniques available for acid gas removal from flue gas, 6 dry sorbent injection DSI has seized an increasing market share in recent years. The usual choice for the DSI sorbent in industrial practice is between calcium-based and sodium-based materials. Sodium-based sorbents, mainly represented by sodium bicarbonate IUPAC name: sodium hydrogen carbonate, NaHCO 3 , are valued for their high reactivity toward acid pollutants and the possibility to recycle their reaction residues.
Therefore, the acid pollutants in the flue gas can react with the sorbent both during the entrained flow in the flue gas pipe after the injection point, and on the cake formed on the bags of the fabric filter.
High Resolution Image. Despite the commercial success of sodium bicarbonate injection as a simple and effective acid gas removal solution, open issues remain concerning the reaction process. While NaHCO 3 -based treatment systems always guarantee a high efficiency in the control of acid gas emissions, operational experience across European waste-to-energy plants shows that the same acid gas removal performance is obtained with NaHCO 3 feed rates ranging from 1.
In particular, scarce information is available on the limits of the operating temperature range in which NaHCO 3 -based DSI is effective. This is a relevant issue in industrial applications, since specific design constraints e. Limited attention to date was dedicated in the literature to investigate the heterogeneous reaction process of sodium bicarbonate with acid gases, at least compared to the vast literature on acid gas removal with calcium-based sorbents at low, medium, and high temperature.
Bares et al. With respect to reactivity with HCl, a pioneering study by Mocek et al. They found a positive effect of temperature on the reactivity of activated Na 2 CO 3 , while particle size and concentration of the gaseous reactant had minimal influence on the sorption process.
Duo et al. Experimental runs were carried out in a tubular fixed bed reactor, with the aim of simulating the conditions of a cake of sorbent on the bags of a fabric filter. The goal of the study was to clarify the temperature dependence of the reactivity of activated sodium carbonate in the range of interest, overcoming the fragmented and in part contradictory evidence present in literature.
The results obtained from the laboratory-scale system allowed the investigation of the role of thermal activation and sintering on the reactivity and overall sorbent conversion in HCl and SO 2 heterogeneous reactions with thermally activated sodium carbonate. Experimental Section. A specific surface area of 0. Commercial sodium carbonate reagent grade, VWR , surface area 0.
The reaction between sodium bicarbonate and the acid gases was investigated in a laboratory-scale fixed bed reactor, sketched in Figure 2. Full details on the experimental apparatus are reported elsewhere.
The reactor was positioned in a heating chamber with forced convection, and the reactor temperature was monitored by a type K thermocouple. At the beginning of an experimental run, a purge flow of pure nitrogen was sent to the fixed bed.
The acid gas was then sent to the fixed bed, modifying the position of the bypass valve in Figure 1. The acid gas flowed on the sample until a complete breakthrough was observed 90 min or longer of reaction time, depending on the run.
The FTIR spectra were recorded at a resolution of 4 cm —1. Each spectrum was obtained as average of 16 consecutive scans. This resulted in a time resolution of 3. The concentration of HCl and SO 2 in the outlet gas as a function of time was followed by monitoring the time evolution of the integrated absorbance on characteristic wavenumber ranges.
The selected ranges were — cm —1 for HCl and — cm —1 for SO 2. The profiles of CO 2 and H 2 O generated during the reaction were also followed, by considering respectively the intervals — cm —1 and — cm —1.
Each fixed bed run was repeated three times and the average of measurements is reported. The thermogravimetric TG analysis was carried out on samples of about 20 mg, positioned on a platinum pan. Temperature equilibrium was achieved within 5 min after the start of the jump. The crystalline species present in the samples before and after reaction were determined using X-ray powder diffraction XRD. The step size was 0. The morphological features of the samples were visualized via scanning electron microscopy Ultra 55 Plus, Zeiss, Germany.
Prior to imaging, the samples, placed on a conductive carbon tape, were sputter-coated by gold and palladium for 90 s under Ar plasma to improve their conductivity.
Results and Discussion. The first step of the study consisted in the analysis of the thermal activation process. The thermal activation of sodium bicarbonate, i.
The most important outcome of thermal activation is its effect on sorbent morphology. As shown in the micrographs reported in Figure 4 , sodium bicarbonate panel a is a nonporous solid. During the decomposition reaction, the release of ca. As already noticed by Hartman et al. Figure 4 also reports the XRD patterns of the samples.
Regardless of the activation temperature in this case, the temperature of the isothermal TG run , the chemical species originated from the decomposition of sodium bicarbonate is sodium carbonate. The only noticeable difference between the samples activated at different temperatures, which underwent the same storage conditions in the time between their preparation and the XRD analysis, is a higher intensity of the peaks associated with the hydrated form of sodium carbonate for the samples obtained at a lower activation temperature.
This is again indicative of the higher surface area and, hence, of a higher adsorption capacity of sodium carbonate activated at lower temperature. To highlight the role of thermal activation in enhancing the reactivity of the sodium-based sorbent toward acid gases, a dedicated fixed bed experimental run in ramp of temperature was carried out.
Thermal activation appears crucial in triggering fast desulfurization of the gas stream. Thus, the onset of significant SO 2 sorption coincides with the onset of thermal activation.
The promoting effect of the thermal activation is related to the increase of the porosity and surface area of the sorbent caused by the release of H 2 O and CO 2 , and not to the chemical nature of the product of activation, Na 2 CO 3. The reactivity of activated sodium carbonate toward HCl and SO 2 was tested in isothermal sorption runs.
All the runs were carried out heating the sorbent to the desired reaction temperature in pure nitrogen and providing an additional activation time of 40 min before starting the reaction. The duration of this stabilization time was chosen to facilitate the thermal decomposition of NaHCO 3 to Na 2 CO 3 , while avoiding the exposure of the sample to prereaction sintering for an unrealistically high time.
Figure 7 a shows the breakthrough curves obtained for HCl for runs carried out at different temperatures with a gaseous mixture having an inlet HCl concentration of ppm. Figure 7 b shows the corresponding results obtained with a gas mixture having an inlet SO 2 concentration of ppm.
These concentration values were selected as representative of the HCl and SO 2 content in flue gas generated by municipal or hazardous waste incinerators. In light of the considerations of section 3.
Figure 7 c reports the calculated sorbent conversion after 3 h. It is well-known that in this range there are no thermodynamic limitations to acid gas abatement: from a thermodynamic point of view, reactions R2 and R3 should produce the almost complete removal of HCl and SO 2. The low conversions calculated at the higher temperatures might suggest that physical adsorption is actually taking place instead of chemical reaction. The investigation of the reaction via FTIR spectrometry allows clarifying this aspect by collecting spectra of the gaseous species leaving the reactor.
With reference to the reaction with SO 2 , Figure 8 a shows that CO 2 released by reaction is detected at all the temperatures tested, in an amount that is closely related to the solid conversion shown in Figure 7 c, confirming the occurrence of reaction R3. In addition, the composition of the solid samples after the reaction with SO 2 , probed by XRD, also confirms the occurrence of reaction R3.
Thus, only a weak scattering from Na 2 CO 3 is present in this case. Therefore, both the analyses of evolved gas species and resulting solid phases clarify that the sorption of acid gases is a chemical process across the entire range of temperatures tested. However, this is certainly not the case in the experiments of Figure 7 b, which were carried out with nitrogen as carrier gas, thus not allowing reaction R4 to occur. The presence of oxygen is clearly shown to slow down the overall reaction rate of SO 2.
This is likely due to the additional diffusional resistance in the transport of SO 2 to the reaction interface provided by the formation of Na 2 SO 4. As such, it tends to form a rather compact barrier layer, impervious to diffusion. Figure 9 b shows the effect of a different particle size of sorbent on SO 2 removal.
Similarly, Figure 9 c shows the effect on SO 2 removal of a higher SO 2 inlet concentration ppm. Clearly enough, breakthrough takes place earlier than for a SO 2 inlet concentration of ppm, since the amount of sorbent in the bed was unchanged, but the final sorbent conversion and its dependence on temperature are not affected by this variation. Excluding effects of particle size and concentration of gaseous species, the declining reactivity of activated Na 2 CO 3 with reaction temperature has to be ascribed to morphological changes in the sorbent.
Figure 4 in section 3. The loss of available surface area for reaction has an evident effect on the acid gas removal performance. The decrease of surface area and, thus, of the reactivity of the sorbent might be also accentuated by the nature of the reaction product formed by acid gas sorption, hence explaining the different behavior of SO 2 and HCl.
The present results evidenced that the temperature range at which sodium bicarbonate injection is highly effective is narrow, comprised between the lower limit of thermal decomposition to sodium carbonate and an upper limit deriving from the sintering of the newly formed sodium carbonate.
Operating far from the optimal temperature implies an increasing need of excess sorbent. Considering the results of Figure 7 c on the final sorbent conversion at different temperatures, it can be estimated that the removal of 1 kg of HCl would require 2. Pursuing the maximum utilization of the sorbent is a key aspect in the optimization of flue gas cleaning operation.
Feeding excess sodium bicarbonate to the DSI system not only results in a higher reactant cost per unit of acid gas removed, but also causes an increase in the generation of process residues, the disposal of which is a significant environmental drawback of dry acid gas removal systems.
In most cases, a further constraint to the operating temperature of DSI systems is given by mercury Hg removal, which is typically performed by means of activated carbon, injected in DSI together with the acid gas sorbent.
Thermal decomposition is necessary to form the porous structure in activated sodium carbonate that promotes sorbent reactivity. Yet, significant sintering of nascent sodium carbonate is detected even at temperatures markedly lower than the Tammann temperature of the material. Sintering reduces the sorption capacity of activated Na 2 CO 3 toward acid pollutants.
From the viewpoint of process optimization, this information is useful for the identification of optimal operating conditions in flue gas treatment systems. From the viewpoint of sorbent optimization, the inherent limitations of natural sodium bicarbonate that emerged in this study suggest the potential for synthetic approaches. Sorbent modification methods aimed at improving the resistance of activated Na 2 CO 3 to sintering could be envisaged to harness the benefits of improved kinetics at higher temperatures, while avoiding the insurgence of adverse morphological changes.
Author Information. The authors declare no competing financial interest. Estimating source strengths of HCl and SO 2 emissions in the flue gas from waste incineration. Moreover, since only This simple method is easily applicable and the estimated results could provide scientific basis for the appropriate design and operation of the APC systems as well as corrosion control of heat recovery systems.
Characterisation of acid pollutant emissions in ceramic tile manufacture. Google Scholar There is no corresponding record for this reference. Hydrogen chloride emissions from combustion of raw and torrefied biomass.
Fuel , , 37 — 46 , DOI: Elsevier Ltd. Elevated emissions of hydrogen chloride HCl from combustion of biomass in utility boilers is a major issue as it can cause corrosion and, in combination with the high alkali content often encountered in these fuels, it can also deposit molten alkali chloride salts on the boiler's water tubes.
Such deposition can impede heat transfer and cause further corrosion. It monitored the HCl emissions from torrefaction of biomass and, subsequently, the comparative HCl emissions from combustion of both raw and torrefied biomass. Results showed that during torrefaction most of the chlorine of biomass was released in the gas phase, predominately as HCl.
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