Calcium Magnesium Acetate Research Articles

Improvement of acetate production from lactose by growing Clostridium thermolacticum in mixed batch culture.

The objective of this study was to increase the acetate production by Clostridium thermolacticum growing on lactose, available as a renewable resource in the milk and whey permeate from the cheese industry. Experiments for increased acetate productivity by thermophilic anaerobes grown on lactose were carried out in batch cultures. Lactose at concentration of 30 mmol l(-1) (10 g l(-1)) was completely degraded by Cl. thermolacticum and growth rate was maximal. High concentrations of by-products, ethanol, lactate, hydrogen and carbon dioxide were generated. By using an efficient hydrogenotroph, Methanothermobacter thermoautotrophicus, in a defined thermophilic anaerobic consortium (58 degrees C) with Cl. thermolacticum and the acetogenic Moorella thermoautotrophica, the hydrogen partial pressure was dramatically lowered. As a consequence, by-products concentrations were significantly reduced and acetate production was increased. Through efficient in situ hydrogen scavenging in the consortium, the metabolic pattern was modified in favour of acetate production, at the expense of reduced by-products like ethanol. The use of this thermophilic anaerobic consortium opens new opportunities for the efficient valorization of lactose, the main waste from the cheese industry, and production of calcium-magnesium acetate, an environmentally friendly road de-icer.

Simultaneous reduction of NO x and SO 2 emissions from coal combustion by calcium magnesium acetate

The potential of calcium magnesium acetate (CMA) as a medium for the simultaneous control of NO x and SO x emissions has been investigated using a pulverized coal combustion rig operating at 80 kW. A US and a UK coal of significantly different sulphur contents were used as primary fuel and CMA was injected in solution form into the combustion gases by horizontally opposed twin-fluid atomisers at temperatures of 1100–1200 °C. SO 2 reductions typically greater than 80 and 70% were found for initial SO 2 levels of 1000 and 1500 ppm, respectively, at Ca/S ratios greater than 2.5. There did not appear to be significant limitation on sulphation by pore blockage using CMA due to the open structure formed during calcination and there is clear potential for zero SO 2 emissions at higher Ca/S ratios. The Ca content of the CMA in the form of CaO, via a droplet drying/particle calcination process, absorbs SO 2 by sulphation processes by penetration into the open pore structure of these particles. The effect of primary zone stoichiometry ( λ 1=1.05, 1.15 and 1.4) on NO x reduction was investigated for a range of CMA feed rates up to a coal equivalent of 24% of the total thermal input. NO x reductions of 80, 50 and 30% were achieved at a primary zone stoichiometry of λ 1=1.05, 1.15 and 1.4, respectively, for a reburn zone residence time of 0.8 s. At lower equivalent reburn fuel fractions, coal gave greater NO x reductions than CMA but similar levels were achieved above Rff=18%. The mechanism for NO x reduction involves the organic fraction of CMA which pyrolyses into hydrocarbon fragments (CH i ), but to a lesser degree than coal, which may then react with NO x in a manner similar to a conventional ‘reburn’ mechanism where NO x is partly converted to N 2 depending on the availability of oxygen.

Calcined calcium magnesium acetate as a superior SO2 sorbent: I. Thermal decomposition

AbstractThe reactivity of the calcination product of calcium magnesium acetate (CMA) as a possible dry desulfurization agent was evaluated. The first step in the dry desulfurization reaction—the thermal decomposition of CMA—was investigated by determining the decomposition reaction in three steps: 1. the evaporation of water starting at 65°C, 2. the conversion of CMA into CaCO3 and MgO starting at 275°C, and 3. the decomposition of CaCO3 to CaO starting at 580°C. The pseudo‐first‐order kinetic equation was observed for the CMA decomposition to CaCO3 + MgO, with an activation energy of 165.5 kJ/mol. The decomposition of CaCO3 to CaO also obeyed the pseudo‐first‐order kinetics, with an activation energy of 200 kJ/mol. As discussed in Part II of this series, the calcination product from CMA is quite reactive due mainly to the large porosity and internal surface area generated on the removal of the acetate group during the decomposition reaction. Furthermore, as will be shown in Parts II and III, the sulfation capacity of the calcined CMA is much greater than that of conventional sorbents because its sulfation rate does not level off until complete conversion and its MgO content is also sulfated at temperatures lower than about 900°C.

Ca‐Mg acetate as dry SO2 sorbent: III. Sulfation of MgO+CaO

AbstractThe separate sulfation rate of MgO contained in calcined calcium magnesium acetate (CMA) by SO2 and O2 was measured, as well as the simultaneous sulfation of MgO and CaO in the temperature range where the sulfates of both oxides are stable. In the temperature range below 830°C in which MgO sulfation is thermodynamically possible the reaction produced CaSO4·3MgSO4, rather than MgSO4. The formation of the CaSO4·3MgSO4 phase at a reasonable rate during the sulfation of calcined CMA has a significant implication in that it allows the utilization of MgO for SO2 removal, whereas the sulfation of MgO from conventional sources is so slow that it is of no practical interest. Thus, the calcined CMA can remove SO2 at lower temperatures than conventional SO2 absorbent and at a greater capacity and rate, which presents a substantial competitive advantage of this material.

Ca‐Mg acetate as dry SO2 sorbent: II. Sulfation of CaO in calcination product

AbstractThe sulfation rate of CaO contained in calcined calcium magnesium acetate CMA by SO2 and O2 was measured. Although calcined CMA contains CaO and MgO, only CaO reacts with SO2 above 950°C. The reaction occurs at a much greater rate than with other conventional desulfurization agents like calcined limestone, dolomite, or Ca(OH)2, the last of which yields one of the most reactive forms of CaO. The remarkable enhancement of sulfation rate of CaO in calcined CMA is due to its much larger pore size and porosity than those of other agents. Another consequence of this structure of calcined CMA is that the sulfation reaction proceeds to completion without the rate leveling off, unlike in the sulfation of most oxides.

A New Process for Producing Ca/Mg Acetate Deicer with Ca/Mg Waste and Acetic Acid Produced by Wet Oxidation of Organic Waste

Abstract A new process for producing calcium magnesium acetate (CMA) deicer with acetic acid, produced by wet oxidation of organic wastes, and Ca/Mg wastes is proposed. Four kinds of representative organic waste were used as low-cost raw materials, for production of acetic acid, which was then converted to CMA by mixing with a Ca/Mg source such as oyster shells and industrial Mg wastes. The conversion efficiencies to acetic acid and from acetic acid to CMA achieved 14–16% and higher than 99%, respectively.

Ecotoxicological Evaluation of Three Deicers (NaCl, NaFo, CMA)—Effect on Terrestrial Organisms

The use of chemical deicers such as sodium chloride (NaCl) has increased significantly during the past three decades. Deicers induce metal corrosion and alter the physicochemical properties of soils and water. Environmental damage caused by the use of NaCl has prompted government agencies to find alternative deicers. This article presents a comparative ecotoxicological study of three deicers on soil organisms. Sodium formiate (NaFo) and calcium-magnesium acetate (CMA) are the most interesting commercially available deicers based upon their characteristics and potential toxicity. Organisms used in this study were four species of macrophytes (cress (Lepidium sativum), barley (Ordeum vulgare), red fescue grass (Festuca rubra), Kentucky bluegrass (Poa pratensis)) and an invertebrate (Eisenia fetida). Using standardized and modified methods, the relative toxicity of deicers was CMA<NaFo≅NaCl. The results demonstrate that these chemicals could have similar impacts in terrestrial environments since similar quantities of NaFo and greater amounts of CMA are necessary to achieve the same efficiency as NaCl. The toxicity of the tested substances was lower in natural composted soil than in artificial substrate (silica or OECD soil), indicating decreased environmental bioavailability. The response of the organisms changed according to endpoint, species, and soil characteristics (artificial substrate as compared to natural organic soil). The most sensitive endpoint measured was macrophyte growth with Kentucky bluegrass being the most sensitive species.

Laboratory study on the high-temperature capture of HCl gas by dry-injection of calcium-based sorbents

This is a laboratory study on the reduction of combustion-generated hydrochloric acid (HCl) emissions by in-furnace dry-injection of calcium-based sorbents. HCl is a hazardous gaseous pollutant emitted in significant quantities by municipal and hazardous waste incinerators, coal-fired power plants, and other industrial furnaces. Experiments were conducted in a laboratory furnace at gas temperatures of 600–1000°C. HCl gas diluted with N 2, and sorbent powders fluidized in a stream of air were introduced into the furnace concurrently. Chlorination of the sorbents occurred in the hot zone of the furnace at gas residence times ≈1 s. The sorbents chosen for these experiments were calcium formate (CF), calcium magnesium acetate (CMA), calcium propionate (CP), calcium oxide (CX), and calcium carbonate (CC). Upon release of organic volatiles, sorbents calcine to CaO at ≈700°C, and react with the HCl according to the reaction CaO+2HCl⇌CaCl 2+H 2O. At the lowest temperature case examined herein, 600°C, direct reaction of HCl with CaCO 3 may also be expected. The effectiveness of the sorbents to capture HCl was interpreted using the “pore tree” mathematical model for heterogeneous diffusion reactions. Results show that the thin-walled, highly porous cenospheres formed from the pyrolysis and calcination of CF, CMA, and CP exhibited high relative calcium utilization at the upper temperatures of this study. Relative utilizations under these conditions reached 80%. The less costly low-porosity sorbents, calcium carbonate and calcium oxide also performed well. Calcium carbonate reached a relative utilization of 54% in the mid-temperature range, while the calcium oxide reached an 80% relative utilization at the lowest temperature examined. The data matched theoretical predictions of sorbent utilization using the mathematical model, with activation energy and pre-exponential factors for the calcination reaction of 17,000 K and 300,000 ( g gas / cm 2/ s/ atm gas ), respectively. Thus, the kinetics of the calcination reaction were found to be much faster (≈500 times) than those of the sulfation reaction examined previously in this laboratory.

A Laboratory Investigation on Combined In-Furnace Sorbent Injection and Hot Flue-Gas Filtration to Simultaneously Capture SO2, NOx, HCl, and Particulate Emissions

The effectiveness of a novel integrated technique for removing pollutants generated during the combustion of fuels in furnaces is investigated in this experimental and theoretical study. Sorbents, containing calcium/magnesium and organic components, are wet- or dry-sprayed into the postcombustion zone of a furnace. The organic components of the sorbents pyrolyze and reduce NOx under oxygen-lean conditions. The calcium based residues calcine and react with sulfur- and/or chlorine-bearing gases (such as SO2, H2S, HCl, Cl2, etc.), forming stable salts of calcium (CaSO4, CaCl2, etc.). The partially reacted sorbent particles are then collected in the high-temperature ceramic honeycomb filter/reactor, where they continue to react for a prolonged period of time, until the filter is regenerated (cleaned). Using this technique, both the likelihood and the duration of contact between the solid sorbent particles and the gaseous pollutants increases, since reaction takes place both upstream of the filter and inside the filter itself. Hence, the sorbent utilization increases drastically. High filtration efficiency wall-flow honeycomb ceramic monoliths retain particulates, including partially burned carbon (such as soot, char, tar, etc.), ash, and spent sorbent. Complete combustion of carbon may occur inside the high-temperature filter. Periodic aerodynamic regeneration (backpulsing) of the filters removes the collected minerals (ash and spent sorbent). Using this technique, most of the major combustion-generated pollutants can be removed from the effluent with certain efficiencies. In this laboratory study, powders of calcium formate (CF), calcium propionate (CP), calcium(magnesium) acetate (CMA), calcium carbonate (CC), and calcium oxide (CX) sorbents were sprayed in an electrically heated, laminar flow drop-tube furnace where toxic gases of SO2, NO, and HCl were also introduced. Gas temperatures were in the range of 1023−1423 K (750−1150 °C) and gas residence times ≈1 s. A honeycomb ceramic filter, placed at the exit of the furnace, was externally heated to 873−1173 K (600−900 °C). Concentration reductions of the pollutants were measured both with and without the presence of the filter. The “pore tree” mathematical model that describes heterogeneous reaction and transport in porous media was modified to (a) account for simultaneous reaction of calcium with SO2 and HCl, and (b) account for time-dependent reaction in an accumulating bed of sorbent in the filter. Experimental results showed that (i) the sorbent can react with both HCl and SO2 and result in high removal efficiencies for both pollutants, (ii) the filter greatly enhances the SO2 removal and captures particulates, and (iii) the sorbents that contain organics reduce NOx at oxygen-lean conditions. For instance, SO2 removal by CF or CMA, which was 40% without the filter, improved to 80% with the filter (kept at 1173 K), at a Ca/S of 1.5. CMA also reduced NOx by 70%. As NOx reduction mostly depends on fast gas-phase reactions, it was only mildly enhanced at the presence of the filter. Sorbent utilizations, however, were drastically increased in the longer residence time allowed by the presence of the filter. The model's predictions of the experimental data for SO2/HCl concentration reduction and calcium utilizations with and without the filter were fairly successful in most cases, especially at high temperatures.

Extractive Crystallization for the Production of Calcium Acetate and Magnesium Acetate from Carbonate Sources

Extractive crystallization was employed for the preparation of deicing compositions of calcium acetate (CA) and magnesium acetate (MA) at room temperature. The design system comprises an aqueous phase as the source of calcium or magnesium ions and an organic phase as the source of acetate ions. The process was designed with the consideration that acetic acid is used in an organic phase as extracted from a fermentation broth. The conditions under which the extractive crystallization method resulted in the formation of single crystals or aggregates of calcium acetate and magnesium acetate were studied. Furthermore, the effect of acetic acid concentration in the organic and aqueous phases on the characteristics of the obtained crystals was investigated. Overall, the extractive crystallization process proved to be feasible at least in the laboratory and resulted in the production of well-formed, nonporous, large single crystals and clusters of either calcium acetate acetic acid hydrate [Ca(CH3COO)2·CH3COOH·H2O] or magnesium acetate tetrahydrate [Mg(CH3COO)2·4H2O, α], depending on the type of salt (CaCO3 or MgCO3) used in each case.

Investigation of the Conditions for the Production of Calcium Magnesium Acetate (CMA) Road Deicer in an Extractive Crystallization Process

Calcium magnesium acetate (CMA) is considered as the best road deicer to replace the environmentally unacceptable NaCl and CaCl2. However, the high cost of CMA prohibits its widespread use. The present study is dealing with the investigation of a crystallization method for the production of deicing CMA crystals of desired physical properties and the elucidation of the conditions under which such a product can be formed. Extractive crystallization is promising for the low cost production of CMA crystals considering that acetic acid is produced by a biochemical method and removed from the fermentation broth in situ by organic extractant systems. In this method, this organic phase, which contains the acetate ions is contacted with an aqueous phase which is the source of calcium and magnesium ions. The extractive crystallization process resulted in the production of well-formed, large, and non-spherical crystals of calcium acetate (CA), magnesium acetate (MA), and calcium magnesium acetate double salt (CMADS). The crystal size was affected by the concentration of acetic acid in both the organic and aqueous phases, whereas the crystal type and hydration level were determined primarily by the acetic acid concentration in the aqueous phase. The molar ratio of the precursor salts (CaCO3/MgCO3) in the reaction mixture was found to be the major factor for determining the habit and Ca/Mg content of crystals. Crystallization of CMADS was favored at high concentrations of acetic acid in the aqueous phase and at higher temperatures as shown from supplementary evaporation-to-dryness experiments.

00/02288 Investigation of desulfurization and sulfur analysis method in hydropyrolysis of coal

Calcium magnesium acetate (CMA) shows potential as a reductant for simultaneous NOx and SOx removal from coal-fired combustion plant. The performance of urea co-injection with CMA on NO reduction in an ‘advanced reburn’ (AR) configuration has been investigated with a view to optimization of the process in a pulverized coal-fired furnace operating at 80 kW. The impact on SO2 reduction has also been investigated. Urea/CMA solution was sprayed into the reburn zone of the furnace using twin-fluid atomizers over a range of reductant/NO stoichiometric ratios (NSR). The influence on NO reductions of primary zone stoichiometry (λ1) was investigated for a range of CMA reburn feed rates (Rff) and reburn zone stoichiometry (λ2). In addition, the effect of temperature on the SNCR performance of urea was investigated. Optimum process conditions were categorized either by maximizing NO and SO2 reductions (Modes A and B, respectively) or maximizing reductant utilization efficiencies (Modes C and D). NO control was best performed at λ1=1.05, but SO2 reductions were greatest at more fuel-lean primary zone conditions (λ1=1.15). Highest NO reductions of 85% under AR-rich conditions were achieved under Mode A, but were only slightly higher compared with reductions of 79% under Mode B, where SO2 reductions were optimized at 85%. N-utilization was also at an acceptable level of 25% compared to the maximum utilization efficiency which was obtained at NSR=1.5 of 30% for the same conditions of stoichiometry operating in Mode C. Operation at this lower level of reburn (9.6%) could significantly reduce the consumption of CMA with some impact on NO reduction (73%). SO2 removal performance would be compromised severely with reductions lowered from 75% at Mode A to 35% at Mode C. Optimizing Ca utilization (Mode D) resulted in poor NO and SO2 reductions, at 61 and 22%, respectively, and can be discounted as a viable option. The technique offers flexibility of operation depending on the emission control requirements.

The effect of CMA deicers on concrete properties

The paper presents the results of an investigation of the effects of concentrated calcium–magnesium acetate (CMA) solutions on concrete. Concrete specimens were manufactured following guidelines for structures exposed to freeze–thaw cycles and deicers (water–cement ratio, w/c=0.45 and air-entraining admixture) employing two cements obtained by blending a Portland clinker with 20% of ground limestone, or 40% blast furnace slag. Following 28 days of curing, the specimens were immersed for 8 months at 20°C in two concentrated (25%) CMA solutions prepared using (a) a commercial CMA-based deicing chemical or (b) pure calcium and magnesium acetates blended to obtain the same Ca/Mg molar ratio (0.43) as the deicer. Continuous exposure to both CMA solutions led to a significant decrease in load capacity, mass loss and marked visual deterioration. The aggression was particularly strong in the case of the deicer solution, and was mitigated by the use of the slag cement.

00/01675 Calcination of calcium acetate and calcium magnesium acetate: effect of the reacting atmosphere

00/01675 Calcination of calcium acetate and calcium magnesium acetate: effect of the reacting atmosphere

Stability and oxidative stabilisation of sulphided calcareous sorbents from entrained flow gasifiers

The stability of different sulphided materials (pure CaS particles, sulphided calcium hydroxide, sulphided limestone, sulphided dolomite and sulphided calcium magnesium acetate) when exposed to a moistened stream of air at ambient conditions has been studied. For all the analysed sorbents, the release of H 2S during exposure to a moistened stream of air is a function of the calcium sulphide content of the sorbent. The ratio between the amount of released sulphur and the amount of sulphur stabilised as sulphate or elemental sulphur is also a function of the initial calcium sulphide content of the sorbent. Additionally, the performance of air oxidation at different temperatures (800–980°C) for stabilisation of the sulphided sorbents has been analysed. The final apparent conversion achieved during air oxidation of the sulphided sorbents, including particles of sulphided calcium acetate, in the temperature range 800–980°C shows an inverse dependence with the (calcium sulphide content)/(specific surface area) ratio of the sorbents. The total amount of SO 2 released during air oxidation at high temperature is a function of the initial calcium sulphide content of the samples. Conversion degrees up to 100% have been obtained. For all sorbents, the conditions for complete stabilisation and negligible SO 2 release during oxidation were established. The differences found in final oxidation conversions and stability of the oxidised sorbents for increasing oxidation temperatures can be explained in terms of the oxidation mechanisms for low (<890°C) and high temperatures.

The Bridge of Mandolin County

The Bridge of Mandolin County is a case designed to teach the general chemistry principles of molar mass, ions and aqueous reactions, solubility rules, and inorganic nomenclature. Through the instructor-facilitated class discussion, students consider the options before the Mandolin Town Council regarding deicing the newly constructed bridge connecting Mandolin with a large nearby city. The students must decipher contradictory claims made on behalf of sodium chloride, the traditional deicer, and calcium magnesium acetate, a new environmentally friendly deicer, to arrive at the most cost-effective and environmentally appropriate deicing product. As they work through the analysis they raise questions that can be addressed in a laboratory setting. Four optional role-playing experiments are included, which can be used by the students to gather information helpful to resolution of the case. The case is intended to be used over two class periods, with a laboratory period in between, though suggestions for other ...

Carbon additions increase nitrogen availability in northern hardwood forest soils

The effects of acetate additions to northern hardwood forest soils on microbial biomass carbon (C) and nitrogen (N) content, soil inorganic N levels, respirable C and potential net N mineralization and nitrification were evaluated. The experiment was relevant to a potential watershed-scale calcium (Ca) addition that aims to replace Ca depleted by long-term exposure to acid rain. One option for this addition is to use calcium-magnesium (Mg) acetate, a compound that is inexpensive and much more readily soluble than the Ca carbonate that is generally used for large-scale liming. Field plots were treated with sodium (NA) acetate, Na bicarbonate or water (control) and were sampled (forest floor – Oe and Oa combined) 2, 10 and 58 days following application. It was expected that the addition of C would lead to an increase in biomass C and N and a decrease in inorganic N. Instead, we observed no effect on biomass C, a decline in biomass N and an increase in N availability. One possible explanation for our surprising results is that the C addition stimulated microbial activity but not growth. A second, and more likely, explanation for our results is that the C addition did stimulate microbial growth and activity, but there was no increase in microbial biomass due to predation of the new biomass by soil fauna. The results confirm the emerging realization that the effects of increases in the flow of C to soils, either by deliberate addition or from changes in atmospheric CO2, are more complex than would be expected from a simple C : N ratio analysis. Evaluations of large-scale manipulations of forest soils to ameliorate effects of atmospheric deposition or to dispose of wastes should consider microbial and faunal dynamics in considerable detail.

99/02029 Trace metal partitioning when firing pulverized coal and coal-water slurry fuel: Nodelman, I. G. et al. Prepr. Extract Abstr. ACS Natl. Meet., Am. Chem. Soc., Div. Environ. Chem., 1998, 38, (2), 169–172

Major environmental issues are now coming to the forefront in all parts of the globe with increased public awareness of the human health effects and the possible effects on our global environment. Modern control technologies, when implemented, have significantly reduced air pollution emissions that are a result of coal combustion during this century. However, the emissions have not been completely eliminated. On this basis, a study was conducted to determine the efficacy of carboxylic calcium and magnesium salts (e.g., calcium magnesium acetate or CMA, CaMg2 (CH3CO2)6) for the simultaneous removal of SO2 and NOx in oxygen-lean atmospheres. Experiments were performed in a high-temperature furnace that stimulated the post-flame environment of a coal-fired boiler by providing similar temperatures and partial pressures of SO2, NOx, CO2, and O2. When injected into a hot environment, the salts calcined and formed highly porous ‘popcorn’-like cenospheres. Residual MgO and/or CaCO3 and CaO reacted heterogeneously with SO2, and oxygen to form MgSO4 and/or CaSO4. The organic components — which can be manufactured from wastes such as sewage sludge — reduced NOx to N2 efficiently in a moderately fuel rich atmosphere. Dry-injected CMA particles at a CaS ratio of 2, residence time of 1 s and bulk equivalence ratio of 1.3 removed over 90% of SO2 and NOx at gas temperatures ≥950°C. When the furnace isothermal zone was ≤950°C, CaO was essentially inert in the furnace quenching zone, while MgO continued to sorb SO2 as the gas temperature cooled at a rate of — 130°C/s. Hence, the removal of SO2 by CMA could continue for nearly the entire residence time of emissions in the exhaust stream of a power plant. The composition of the calcined salts was used to interpret the results of a cenosphere sulfation model. The sulfation kinetics of Ca-containing calcined residues were found to be bounded by those of pure CaO and pure CaCO3. The high solubility of the carboxylic acid salts makes them excellent candidates for wet injection. Fine mists of CMA sprayed in the furnace at temperatures between 850 and 1050°C, removed 90% of SO2 at a CaS molar ratio of 1, about half of the amount used in the dry injection experiments to achieve a similar SO2 reduction. The NOx reduction chemistry was not affected by water when CMA was sprayed at a CaS ratio of 1, i.e., the same reduction efficiency was achieved as with dry injection (25–30%). Thus, while a substantial degree of success has been achieved in controlling SO2 and NOx emissions, unfortunately, the emissions that are currently unable to be controlled include vapor and particulate emissions within the respirable range. The respirable particulates encompass heavy metals, polyaromatic hydrocarbons, and volatile organics and have the ability to penetrate into the lungs. The vapor phase emissions comprise mercury, arsenic, and selenium. Most of the mercury vapor emissions are unable to be controlled by the current technologies of the electrostatic precipitator or the baghouse. Some of the potential emissions are known to be carcinogens. Therefore, new or improved current technologies for emission control are being developed in hopes of reducing the potential effects. Because previous interest for control technology was directed toward the control of acid rain precursors (sulfur dioxide and nitrogen oxides emissions), and laboratory studies revealed that the injection of calcium magnesium acetate (CMA) into the combustion chamber significantly reduces both levels of emissions, the effect of this sorbent on mercury vapor capture was investigated suing CMA ash after combustion with the gases (SO2 and NOx). Also, the effect of calcium magnesium carbonate (dolomite, CMC), currently being injected into industrial furnaces, was investigated utilizing the same combustion conditions as CMA. In addition, CMA when calcined forms cenospheres which possess thin porous walls with blowholes that enable mercury vapor and respirable particulates to penetrate into the interior of the particle. Thus, these CMA-ash cenospheres have higher porosity and surface area that provides more area for capture and reactions to occur than CMC ash. Experiments for mercury capture have demonstrated that CMA ash combusted with the gases SO2NOx provided the greatest removal (40%); CMC at the same conditions exhibited only 4% removal. Furthermore, in separate experiments using a model particulate (FeSO4), CMA ash was able to capture more of these model air particulates than the CMC ash after combustion suggesting an even further role of CMA in particulate toxin capture. Analysis of ‘spent’ CMA or CMA ‘ash’ from the laboratory furnace, which was combusted with SO2NOx revealed substantial amounts of elemental sulfur, while no elemental sulfur was present on CMA ash which was combusted in the furnace without SO2NOx. These results suggest that CMA pyrolysis serves to reduce SO2 to elemental sulfur and indicating that HgS(s) formation is feasible, thus suggesting the scavenger value of CMA in capturing mercury vapor.

99/02031 Use of coal combustion byproducts in infrastructure projects - a total benefit option: Militaru, C. and Humphrey, H. J. Proc., Annu. Meet. Air Waste Manage. Assoc., 1996, 89, ra11401, 1–12

Major environmental issues are now coming to the forefront in all parts of the globe with increased public awareness of the human health effects and the possible effects on our global environment. Modern control technologies, when implemented, have significantly reduced air pollution emissions that are a result of coal combustion during this century. However, the emissions have not been completely eliminated. On this basis, a study was conducted to determine the efficacy of carboxylic calcium and magnesium salts (e.g., calcium magnesium acetate or CMA, CaMg2 (CH3CO2)6) for the simultaneous removal of SO2 and NOx in oxygen-lean atmospheres. Experiments were performed in a high-temperature furnace that stimulated the post-flame environment of a coal-fired boiler by providing similar temperatures and partial pressures of SO2, NOx, CO2, and O2. When injected into a hot environment, the salts calcined and formed highly porous ‘popcorn’-like cenospheres. Residual MgO and/or CaCO3 and CaO reacted heterogeneously with SO2, and oxygen to form MgSO4 and/or CaSO4. The organic components — which can be manufactured from wastes such as sewage sludge — reduced NOx to N2 efficiently in a moderately fuel rich atmosphere. Dry-injected CMA particles at a CaS ratio of 2, residence time of 1 s and bulk equivalence ratio of 1.3 removed over 90% of SO2 and NOx at gas temperatures ≥950°C. When the furnace isothermal zone was ≤950°C, CaO was essentially inert in the furnace quenching zone, while MgO continued to sorb SO2 as the gas temperature cooled at a rate of — 130°C/s. Hence, the removal of SO2 by CMA could continue for nearly the entire residence time of emissions in the exhaust stream of a power plant. The composition of the calcined salts was used to interpret the results of a cenosphere sulfation model. The sulfation kinetics of Ca-containing calcined residues were found to be bounded by those of pure CaO and pure CaCO3. The high solubility of the carboxylic acid salts makes them excellent candidates for wet injection. Fine mists of CMA sprayed in the furnace at temperatures between 850 and 1050°C, removed 90% of SO2 at a CaS molar ratio of 1, about half of the amount used in the dry injection experiments to achieve a similar SO2 reduction. The NOx reduction chemistry was not affected by water when CMA was sprayed at a CaS ratio of 1, i.e., the same reduction efficiency was achieved as with dry injection (25–30%). Thus, while a substantial degree of success has been achieved in controlling SO2 and NOx emissions, unfortunately, the emissions that are currently unable to be controlled include vapor and particulate emissions within the respirable range. The respirable particulates encompass heavy metals, polyaromatic hydrocarbons, and volatile organics and have the ability to penetrate into the lungs. The vapor phase emissions comprise mercury, arsenic, and selenium. Most of the mercury vapor emissions are unable to be controlled by the current technologies of the electrostatic precipitator or the baghouse. Some of the potential emissions are known to be carcinogens. Therefore, new or improved current technologies for emission control are being developed in hopes of reducing the potential effects. Because previous interest for control technology was directed toward the control of acid rain precursors (sulfur dioxide and nitrogen oxides emissions), and laboratory studies revealed that the injection of calcium magnesium acetate (CMA) into the combustion chamber significantly reduces both levels of emissions, the effect of this sorbent on mercury vapor capture was investigated suing CMA ash after combustion with the gases (SO2 and NOx). Also, the effect of calcium magnesium carbonate (dolomite, CMC), currently being injected into industrial furnaces, was investigated utilizing the same combustion conditions as CMA. In addition, CMA when calcined forms cenospheres which possess thin porous walls with blowholes that enable mercury vapor and respirable particulates to penetrate into the interior of the particle. Thus, these CMA-ash cenospheres have higher porosity and surface area that provides more area for capture and reactions to occur than CMC ash. Experiments for mercury capture have demonstrated that CMA ash combusted with the gases SO2NOx provided the greatest removal (40%); CMC at the same conditions exhibited only 4% removal. Furthermore, in separate experiments using a model particulate (FeSO4), CMA ash was able to capture more of these model air particulates than the CMC ash after combustion suggesting an even further role of CMA in particulate toxin capture. Analysis of ‘spent’ CMA or CMA ‘ash’ from the laboratory furnace, which was combusted with SO2NOx revealed substantial amounts of elemental sulfur, while no elemental sulfur was present on CMA ash which was combusted in the furnace without SO2NOx. These results suggest that CMA pyrolysis serves to reduce SO2 to elemental sulfur and indicating that HgS(s) formation is feasible, thus suggesting the scavenger value of CMA in capturing mercury vapor.

99/02032 Commercial nuclear reactor loose part monitor setpoints: Persio, J. V. Progress in Nuclear Energy, 1999, 34, (3), 203–211

Major environmental issues are now coming to the forefront in all parts of the globe with increased public awareness of the human health effects and the possible effects on our global environment. Modern control technologies, when implemented, have significantly reduced air pollution emissions that are a result of coal combustion during this century. However, the emissions have not been completely eliminated. On this basis, a study was conducted to determine the efficacy of carboxylic calcium and magnesium salts (e.g., calcium magnesium acetate or CMA, CaMg2 (CH3CO2)6) for the simultaneous removal of SO2 and NOx in oxygen-lean atmospheres. Experiments were performed in a high-temperature furnace that stimulated the post-flame environment of a coal-fired boiler by providing similar temperatures and partial pressures of SO2, NOx, CO2, and O2. When injected into a hot environment, the salts calcined and formed highly porous ‘popcorn’-like cenospheres. Residual MgO and/or CaCO3 and CaO reacted heterogeneously with SO2, and oxygen to form MgSO4 and/or CaSO4. The organic components — which can be manufactured from wastes such as sewage sludge — reduced NOx to N2 efficiently in a moderately fuel rich atmosphere. Dry-injected CMA particles at a CaS ratio of 2, residence time of 1 s and bulk equivalence ratio of 1.3 removed over 90% of SO2 and NOx at gas temperatures ≥950°C. When the furnace isothermal zone was ≤950°C, CaO was essentially inert in the furnace quenching zone, while MgO continued to sorb SO2 as the gas temperature cooled at a rate of — 130°C/s. Hence, the removal of SO2 by CMA could continue for nearly the entire residence time of emissions in the exhaust stream of a power plant. The composition of the calcined salts was used to interpret the results of a cenosphere sulfation model. The sulfation kinetics of Ca-containing calcined residues were found to be bounded by those of pure CaO and pure CaCO3. The high solubility of the carboxylic acid salts makes them excellent candidates for wet injection. Fine mists of CMA sprayed in the furnace at temperatures between 850 and 1050°C, removed 90% of SO2 at a CaS molar ratio of 1, about half of the amount used in the dry injection experiments to achieve a similar SO2 reduction. The NOx reduction chemistry was not affected by water when CMA was sprayed at a CaS ratio of 1, i.e., the same reduction efficiency was achieved as with dry injection (25–30%). Thus, while a substantial degree of success has been achieved in controlling SO2 and NOx emissions, unfortunately, the emissions that are currently unable to be controlled include vapor and particulate emissions within the respirable range. The respirable particulates encompass heavy metals, polyaromatic hydrocarbons, and volatile organics and have the ability to penetrate into the lungs. The vapor phase emissions comprise mercury, arsenic, and selenium. Most of the mercury vapor emissions are unable to be controlled by the current technologies of the electrostatic precipitator or the baghouse. Some of the potential emissions are known to be carcinogens. Therefore, new or improved current technologies for emission control are being developed in hopes of reducing the potential effects. Because previous interest for control technology was directed toward the control of acid rain precursors (sulfur dioxide and nitrogen oxides emissions), and laboratory studies revealed that the injection of calcium magnesium acetate (CMA) into the combustion chamber significantly reduces both levels of emissions, the effect of this sorbent on mercury vapor capture was investigated suing CMA ash after combustion with the gases (SO2 and NOx). Also, the effect of calcium magnesium carbonate (dolomite, CMC), currently being injected into industrial furnaces, was investigated utilizing the same combustion conditions as CMA. In addition, CMA when calcined forms cenospheres which possess thin porous walls with blowholes that enable mercury vapor and respirable particulates to penetrate into the interior of the particle. Thus, these CMA-ash cenospheres have higher porosity and surface area that provides more area for capture and reactions to occur than CMC ash. Experiments for mercury capture have demonstrated that CMA ash combusted with the gases SO2NOx provided the greatest removal (40%); CMC at the same conditions exhibited only 4% removal. Furthermore, in separate experiments using a model particulate (FeSO4), CMA ash was able to capture more of these model air particulates than the CMC ash after combustion suggesting an even further role of CMA in particulate toxin capture. Analysis of ‘spent’ CMA or CMA ‘ash’ from the laboratory furnace, which was combusted with SO2NOx revealed substantial amounts of elemental sulfur, while no elemental sulfur was present on CMA ash which was combusted in the furnace without SO2NOx. These results suggest that CMA pyrolysis serves to reduce SO2 to elemental sulfur and indicating that HgS(s) formation is feasible, thus suggesting the scavenger value of CMA in capturing mercury vapor.