Flue Gas Desulfurization By-products Research Articles

Recovery of SO2and MgO from By-Products of MgO Wet Flue Gas Desulfurization

An industrial demonstration unit using natural gas as a heat source was built to calcine the by-products of MgO wet flue gas desulfurization from power plants; influencing factors on the SO2 content in calciner gas were comprehensively analyzed; and an advantageous recycling condition of MgO and SO2 from by-products was summarized. Results showed that the SO2 content in the calciner gas was increased by more than 10 times under a lower excess air coefficient, a higher feed rate, a lower crystal water in by-products, and a higher feed port position. For the tests conducted under the excess air coefficient above and below one, the effect of the furnace temperature on the SO2 content in the calciner gas was reversed. Results of activity analysis indicate that particles of MgO generated under the calcination temperature of 900-1,000°C had a high activity. In contrast, due to the slight sintering, MgO generated under the calcination temperature of 1,100°C had a low activity. To recycle SO2 as well as MgO, a temperature range of 900-927°C for TE103 is proposed. These studies will prompt the desulfurization market diversification, reduce the sulfur's dependence on imports for making sulfuric acid, be meaningful to balance the usage of the natural resource in China, and be regarded as a reference for the development of this technology for other similar developing countries.

Research on sulfur recovery from the byproducts of magnesia wet flue gas desulfurization

To recycle sulfur from byproducts of magnesia wet flue gas desulfurization, the authors conducted an experimental study and computational analysis on the factors influencing the SO2 mole fraction in the calciner gas by an industrial demonstration unit. With a sulfur content of 1.65% in coal and a generating capacity of 300 MW of power plant, the economics of the renewable magnesium oxide desulfurization technology was compared to that of limestone–gypsum desulfurization technology. The results show that the decomposition reaction of byproducts mainly occurred in the lower zone of the furnace. When the excess air coefficient was 1.05 and the magnesium sulfite content in the byproducts was 60%, the SO2 mole fraction in the calciner gas was 10.5%. Decreasing the excess air coefficient can improve the SO2 mole fraction in the calciner gas. When the moisture content in the byproducts was 15%, the SO2 mole fraction reached 9.2%. The calciner exit gas temperature should be controlled at 1253.5 K or below. Adopting oxygen-enriched combustion, the oxygen content in air should be controlled to 31%. The magnesium oxide desulfurization renewable technology was found to be more economic.

Mechanism and numerical simulation of multicomponent solute transport in sodic soils reclaimed by calcium sulfate

The mechanism for reclaiming sodic soils using calcium sulfate (CaSO4) could provide a theoretical basis for the field application of CaSO4 substitutes, including the by-products of flue gas desulfurization (BFGD), fly ash, and phosphorus gypsum. In this study, Ca2+ application experiment was conducted to analyze the dynamic changes of the cations in the reclamation of sodic soils with CaSO4. A multicomponent solute transport model (UNSATCHEM) that considers ion adsorption exchange and dynamic changes in the soil’s hydraulic conductivity was subsequently used to simulate and predict the movement of ions. The Ca2+ application experiment consisted of four treatments with four CaSO4 concentrations (0.5, 1, 1.5, and 2 g L−1). When the Ca2+ concentrations in the supplied water were 14.71, 22.06, and 29.41 mmol L−1, Ca2+ achieved penetration, and this process was faster when the Ca2+ concentration in the supplied water was higher. Ca2+ did not achieve penetration when the Ca2+ concentration was 7.35 mmol L−1. UNSATCHEM was able to simulate the transportation mechanism of Ca2+ and Na+ in the soil solution in the Ca2+ application experiment, the adsorption and exchange between the Na+ in the soil colloid and Ca2+ in the soil solution, and the precipitation and dissolution of CaSO4 with a high degree of accuracy. Sodic soil reclamation with CaSO4 was not a short-term process. Compared with applying CaSO4 only once, applying CaSO4 in batches decreased the accumulation of soil salts and promoted its dissolution.

Effect of Byproducts of Flue Gas Desulfurization on the Soluble Salts Composition and Chemical Properties of Sodic Soils

The byproducts of flue gas desulfurization (BFGD) are a useful external source of Ca2+ for the reclamation of sodic soils because they are comparatively cheap, generally available and have high gypsum content. The ion solution composition of sodic soils also plays an important role in the reclamation process. The effect of BFGD on the soluble salts composition and chemical properties of sodic soils were studied in a soil column experiment. The experiment consisted of four treatments using two different sodic soils (sodic soil I and sodic soil II) and two BFGD rates. After the application of BFGD and leaching, the soil soluble salts were transformed from sodic salts containing Na2CO3 and NaHCO3 to neutral salts containing NaCl and Na2SO4. The sodium adsorption ratio (SAR), pH and electrical conductivity (EC) decreased at all soil depths, and more significantly in the top soil depth. At a depth of 0–40 cm in both sodic soil I and sodic soil II, the SAR, EC and pH were less than 13, 4 dS m−1 and 8.5, respectively. The changes in the chemical properties of the sodic soils reflected the changes in the ion composition of soluble salts. Leaching played a key role in the reclamation process and the reclamation effect was positively associated with the amount of leaching. The soil salts did not accumulate in the top soil layer, but there was a slight increase in the middle and bottom soil depths. The results demonstrate that the reclamation of sodic soils using BFGD is promising.

When a Negative Externality Turns Positive: An Analysis of Flue-Gas Desulfurization By-Products

Energy and environmental regulations often result in the generation of unforeseen marketable by-products that can reduce costs of compliance. This research evaluates a unique case in which the marketability of by-products produces positive external benefits. Specifically, this paper focuses on flue-gas desulfurization (FGD) gypsum by-product produced by coal-fired electric plants using sulfur dioxide (SO2) scrubbing technology to comply with the emission standards set by the 1990 Clean Air Act Amendment (CAAA). Intuitively, the ability to market FGD gypsum provides incentives for electricity generating plants to operate their scrubbers more efficiently by providing gypsum revenues, and lowering gypsum disposal costs. Increased operating efficiency creates external benefits attributed to reduced SO2 emissions that would otherwise not have occurred. In order to estimate the impact of FGD gypsum marketability on SO2 emissions, a unique longitudinal database is constructed that merges electricity plants’ boiler-level SO2 emissions data from the U.S. Environmental Protection Agency (EPA) with data on scrubber operations and coal quality available from the U.S. Energy Information Administration (EIA). Boiler fixed-effect estimations suggest annual SO2 emissions decline by 3,494 tons as a result of gypsum marketing. This corresponds with a 39% average reduction in SO2 emissions at boilers marketing FGD gypsum. The total benefits associated with the reduced SO2 emissions are estimated between $147.1 billion and $350.6 billion (2011$), or between 0.9% and 2.1% of the total benefits of the U.S. CAA from 1990 to 2010.

Sodic Soil Properties and Sunflower Growth as Affected by Byproducts of Flue Gas Desulfurization

The main component of the byproducts of flue gas desulfurization (BFGD) is CaSO4, which can be used to improve sodic soils. The effects of BFGD on sodic soil properties and sunflower growth were studied in a pot experiment. The experiment consisted of eight treatments, at four BFGD rates (0, 7.5, 15 and 22.5 t ha−1) and two leaching levels (750 and 1200 m3 ha−1). The germination rate and yield of the sunflower increased, and the exchangeable sodium percentage (ESP), pH and total dissolved salts (TDS) in the soils decreased after the byproducts were applied. Excessive BFGD also affected sunflower germination and growth, and leaching improved reclamation efficiency. The physical and chemical properties of the reclaimed soils were best when the byproducts were applied at 7.5 t ha−1 and water was supplied at 1200 m3·ha−1. Under these conditions, the soil pH, ESP, and TDS decreased from 9.2, 63.5 and 0.65% to 7.8, 2.8 and 0.06%, and the germination rate and yield per sunflower reached 90% and 36.4 g, respectively. Salinity should be controlled by leaching when sodic soils are reclaimed with BFGD as sunflower growth is very sensitive to salinity during its seedling stage.

Evaluation of Amendments to Control Phosphorus Losses in Runoff from Pig Slurry Applications to Land

AbstractIf spread in excess of crop requirements, incidental phosphorus (P) losses from agriculture can lead to eutrophication of receiving waters. The use of amendments in targeted areas may help reduce the possibility of surface runoff of nutrients. The aim of this study was to identify amendments which may be effective in reducing incidental dissolved reactive phosphorus (DRP) losses in surface runoff from land applied pig slurry. For this purpose, the DRP losses under simulated conditions across the surface of intact grassland soil cores, loaded with unamended and amended slurry at a rate equivalent to 19 kg P ha−1, were determined over a 30 h period. The effectiveness of the amendments at reducing DRP in overlying water were (in decreasing order): alum (86%), flue gas desulfurization by‐product (FGD) (74%), poly‐aluminum (Al) chloride (PAC) (73%), ferric chloride (71%), fly ash (58%), and lime (54%). FGD was the most costly of all the treatments (€7.64/m3 for 74% removal). Ranked in terms of feasibility, which takes into account effectiveness, cost, and other potential impediments to use, they were: alum, ferric chloride, PAC, fly ash, lime, and FGD.

Evaluation of Changes in SO2 Emissions and Economic Indicators Following the Reclamation of Alkali Soil in China Using By-Products of Flue Gas Desulfurization

With the aim of alleviating the problems of air pollution, soil desertification, and food shortages in China, we have studied the impact of reclamation of alkali soil using the by-products of flue gas desulfurization (FGD). We have developed an evaluation model for assessing the complete economic and environmental impact of the introduction of environmental improvement technologies. The model consists of an economic model based on an input–output table for China and a soil reclamation model. In the context of the introduction of FGD equipment, we are able to calculate the associated changes in economic variables such as real GDP, average wage, labor supply, domestic electricity price, real investment other than for desulfurization equipment, investment in construction, SO2 emissions in provinces and cities, area of reclaimed alkali soil, and corn and rice production. We simulated the introduction of the wet limestone–gypsum process and/or the integrated desulfurization and water-film dust collection process. The results confirm a reduction in SO2 emissions and increases in GDP, domestic electricity price, and agricultural production following soil reclamation via the application of desulfurization by-products. In summary, our results confirm the effectiveness of these desulfurization technologies in terms of improving the economy and environment in China.

Salt-Affected Soil Amelioration with Flue Gas Desulfurization By-Products and Waste Gypsum Board in Tianjin, China

Soil salinization has progressed rapidly in northeastern and western China. In addition, air pollution is one of the most serious environmental problems. To alleviate the problems of soil salinization, food shortages, and air pollution, we have studied the amelioration of salt-affected soil using the by-products of flue gas desulfurization (FGD). Moreover, the recycling of waste gypsum produced at both new construction sites and demolition work sites has become a serious challenge in Japan. FGD gypsum in China and gypsum separated from waste gypsum board (WGB) in Japan were added to salt-affected soil as soil amendments. The effects of lignite and peat, which contains humic substances, were also investigated. With treatment, the soil's chemical parameters were restored, and agricultural production increased in all fields. Therefore, we have confirmed the effectiveness of amelioration of salt-affected soil by both FGD and WGB gypsum. Moreover, the use of lignite and peat with gypsum accelerated the effect of soil amelioration. This result suggests that the application rates of both types of gypsum could be reduced. Thus, we can propose a new salt-affected soil reclamation method using WGB, lignite, and peat in China.

Stabilization of Flue Gas Desulfurization By-Products with Fly Ash, Cement, and Sialite

Flue gas desulfurization (FGD) sludge is a by-product generated by air pollution control systems used in coal-fired power plants. The objective of this work was to stabilize FGD gypsum and FGD filter cake with Class C fly ash. The effectiveness of other additives, such as cement, cement kiln dust, and sialite was also investigated. The chemical, physical, and mineralogical properties of FGD gypsum and FGD filter cake were analyzed. Compaction, California bearing ratio (CBR), and unconfined compressive strength (UCS) tests were conducted on FGD gypsum and FGD filter cake with fly ash. The UCS tests were also conducted on FGD materials stabilized separately with cement, cement kiln dust, and sialite. This study investigated the environmental implications of these two types of FGD by-products with different additives. The test results indicated that both CBR values and UCS for FGD gypsum and filter cake increased with an increase in fly ash contents. FGD gypsum has the potential to be used in geotechnical fill and embankment directly, while FGD filter cake cannot be used directly in pavements without stabilization.

Study on the Effect of CO2on the Consumption of Desulfurizing Agent Ca(OH)2in Flue Gas Desulfurization

In view of the ambiguity concerning the effect of CO2 on the consumption of desulfurizing agent and based on our previous findings when studying flue gas desulfurization (FGD) byproduct, a specific study on the influence of CO2 has been carried out here with Ca(OH)2 being employed as a desulfurizing agent. This study is based on compositional analyses of the reaction products, and combined measurements have provided relatively precise compositions of the reaction products derived from Ca(OH)2 and flue gases. It has been found that the presence of CO2 does have an effect on the desulfurization reaction and on the consumption of desulfurizing agent when Ca(OH)2 is employed as the sorbent for SO2. Also, the formation of CaCO3 is inevitable at about 70 °C and is enhanced under conditions of high humidity. Although over 90% SO2 removal efficiency could be achieved with a relatively high Ca/S mole ratio, the effective utilization of desulfurizing agent would be low because CaCO3 is not the targeted product. Therefore, in order to improve semidry FGD technology, measures must be taken to prevent the reaction between CO2 and Ca(OH)2 so as to increase the utilization ratio of the desulfurizing agent.

Preparation of α-calcium sulfate hemihydrate from FGD gypsum in K, Mg-containing concentrated CaCl 2 solution under mild conditions

To prepare α-calcium sulfate hemihydrate (α-HH) from flue gas desulfurization (FGD) byproduct under atmospheric pressure, the dehydration of FGD gypsum in a concentrated Ca and Mg chlorides solution medium at 95 °C was investigated, and the effects of K + ions were focused on. The crystal water content variation, material phases, and morphological characteristics of the dehydration products were examined and compared. The solubilities of α-HH in the mixed salt solutions with different K + ion concentrations were also determined. It was found that with low concentration of K + ions in the mixed salt solution (i.e. 0.001–0.035 M), the dehydration rate was enhanced, while with higher K + ion concentration (i.e. 0.087–0.263 M), this process was retarded. α-HH was the dehydration product when K + ion concentration was at appropriate level, while anhydrite (AH) occurred when K + ion concentration was above 0.173 M. K + ions were assumed to behave as a capping agent to control the morphology of the α-HH, resulting in crystals of lower aspect ratio. FGD gypsum can be successfully transformed into α-HH in concentrated Ca and Mg chloride solution under mild conditions, and K + ions play an important role in the process.

Amelioration of alkali soil using flue gas desulfurization byproducts: Productivity and environmental quality

In this study, flue gas desulfurization (FGD) byproducts are used to ameliorate alkali soil. The average application rates for soils with low exchangeable sodium percentage (ESP), mid ESP, and high ESP are 20.9, 30.6, and 59.3 Mg ha −1, respectively. The experimental results obtained for 3 consecutive years reveal that the emergence ratios and yields of the crops were 1.1–7.6 times and 1.1–13.9 times those of the untreated control, respectively. The concentrations of Cr, Pb, Cd, As, and Hg in the treated soils are far below the background values stipulated by the Environmental Quality Standard for Soils (GB15618-1995). Their concentrations in the seeds of corn and alfalfa grown in the treated soils are far below the tolerance limits regulated by National Food Standards of China. The results of this research demonstrate that the amelioration of alkali soils using FGD byproducts is promising.

Distribution of Arsenic and Mercury in Lime Spray Dryer Ash

The partitioning of As and Hg in various components of lime spray dryer (LSD) ash samples from a coal-fired boiler was characterized to better understand the form and fate of these elements in flue gas desulfurization byproducts. LSD ash samples, collected from the McCracken Power Plant on the Ohio State University campus, were separated by a 140-mesh (106 μm) sieve into two fractions: a fly-ash-/unburned-carbon-enriched fraction (>106 μm) and a calcium-enriched fraction ( 106 μm were subsequently separated by density using a lithium heteropolytungstate solution. The concentrations of As and Hg were significant in all fractions. The level of As was consistently greater in the calcium-enriched fraction, while Hg was evenly distributed in all components of LSD ash. Specific surface area was an important factor controlling the distribution of Hg in the different components of LSD ash, but not for As. Comparing the LSD ash data to samples collected from t...

Remediation of Abandoned Mines Using Coal Combustion By-Products

Acid mine drainage (AMD) is a phenomenon that occurs when pyrite that is present in abandoned coal mines comes in contact with oxygen and water, which results in the formation of sulfuric acid and iron hydroxide. Grouting of an abandoned mine with alkaline materials provides a permanent reduction in acid production. This study investigates the success of coal combustion by-product (CCB)-based grout mixtures in reducing AMD. The laboratory phase included testing of grouts with different proportions of Class F fly ash, flue gas desulfurization by-product, fluidized bed combustion by-product, and quicklime, for slump, modified flow, bleed, and strength. Then the selected optimal grout mixture was injected into the Frazee mine, located in Western Maryland. Pre- and post-injection water quality data were collected to assess the long-term success of the grouting operation by analyzing mine water, surface water, and groundwater. Laboratory tests indicated that the four mechanical properties of grout mixtures, slump, modified flow, bleed, and strength, are related to the fly ash and free lime contents of the mixture. Eight years of post-injection water quality monitoring shows that there has been a significant decrease in acidity, concentrations of major ions, and trace elements in the mine water. The groundwater and surface water data suggested no adverse impacts of AMD in the pre- or post-injection period. Tests performed on the field exhumed grout cores showed that the hardened grout retained its strength and low hydraulic conductivity with no evidence of in situ weathering. Overall, the results indicated that CCB-based grouts can control the acid mine drainage. However, the mechanical properties of the grout are highly critical for the construction phase, and long-term monitoring is essential for evaluating the effectiveness of the grouting process.

Physical and Chemical Properties of a Minespoil Eight Years after Reclamation in Northeastern Ohio

The potential of using flue gas desulfurization by‐products (FGD) for the reclamation of acid minespoil was assessed in Tuscarawas County of Ohio, USA. In Treatment 1, 280 Mg ha−1 of FGD was incorporated into the graded spoil to a depth of 20 cm. In Treatment 2, 280 Mg ha−1 of FGD and 112 Mg ha−1 of yard waste compost were incorporated into the graded spoil (FGDC). In Treatment 3, 112 Mg ha−1 of limestone was incorporated into the graded spoil and was covered with 20 cm of graded borrowed topsoil (BTS). Six cores and six bulk soil samples were obtained from each treatment for the 0‐ to 10‐cm depth in summer 2002. From the 10‐ to 20‐cm depth, only bulk soil samples were obtained. Bulk and core soil samples were also collected from an unreclaimed spoil (SP) and a nearby unmined soil (UMS). Among the three reclamation treatments, BTS showed better soil quality with higher soil organic C (28.5 Mg ha−1), water‐stable aggregation (556 g kg−1), and mean weight diameter (3.2 mm) of aggregates than FGDC or FGD treatments. The FGDC had higher soil inorganic and organic C than FGD. However, saturated hydraulic conductivity (Ks), cumulative infiltration (I), infiltration rates at 5 min (i5) and 2.5 h (ic), and soil pH were similar among three treatments. Among treatments and controls, soil bulk density (ρb) was lower for FGD, FGDC, and UMS than BTS and SP; and water‐stable aggregation and mean weight diameter of the aggregates was higher for UMS and BTS than FGDC, FGD, and SP for both depths. The I and ic were similar among UMS and treatments. Reclamation improved the soil quality with higher soil pH (≈7) and inorganic and soil organic C than in the SP. With respect to FGD, the soil organic C in FGDC increased at the rate of 0.64 Mg ha−1 yr−1 for the 0‐ to 10‐cm depth. Overall, BTS was the best reclamation treatment. However, if topsoil is unavailable or transport is expensive, FGDC can be used as an effective reclamation material.

Variability of inorganic and organic constituents in lime spray dryer ash

Flue gas desulfurization (FGD) by-products, including lime spray dryer (LSD) ash, have many demonstrated uses. However, concern about the temporal variability in the chemical properties of this material has limited widespread utilization. To determine the variability in inorganic and representative model organic constituents, this study measured elemental composition, leaching properties, polycyclic aromatic hydrocarbon (PAH) concentrations, available lime index (ALI), calcium carbonate equivalent (CCE), and total neutralization potential (TNP) for a representative LSD ash. All parameters investigated showed little variability over different time periods (e.g., daily to yearly) and little variability between samples collected from different particle collection hoppers. Metal concentrations including As, Se, and Hg in LSD ash and in the leachate did not surpass limits for land application (EPA 503 Rule) or limits for the determination of hazardous waste as specified in the Resource Conservative and Recovery Act (RCRA). While a number of PAHs were detected, including naphthalene and phenanthrene, the levels were low and in the range of natural soils. The low variability in ALI, CCE, TNP, and inorganic and organic composition suggests that LSD ash is a consistent and environmentally benign material for agricultural and other engineering applications.

Producing Ammonium Sulfate from Flue Gas Desulfurization By-Products

Emission control technologies using flue gas desulfurization (FGD) have been widely adopted by utilities burning high-sulfur fuels. However, these technologies require additional equipment, greater operating expenses, and increased costs for landfill disposal of the solid by-products produced. The financial burdens would be reduced if successful high-volume commercial applications of the FGD solid by-products were developed. In this study, the technical feasibility of producing ammonium sulfate from FGD residues by allowing it to react with ammonium carbonate in an aqueous solution was preliminarily assessed. Reaction temperatures of 60, 70, and 80°C and residence times of 4 and 6 hours were tested to determine the optimal conversion condition and final product evaluations. High yields (up to 83%) of ammonium sulfate with up to 99% purity were achieved under relatively mild conditions. The optimal conversion condition was observed at 60°C and a 4-hour residence time. The results of this study indicate the technical feasibility of producing ammonium sulfate fertilizer from an FGD by-product.

Use of Flyash as Environmental and Agronomic Amendments

Coal combustion power plant flyash materials have been reported as useful soil amendments with agronomic and environmental benefits. This paper reports the efficacy of fluidized bed combustion (FBC) and flue gas desulfurization (FGD) byproducts, when amended with dairy, swine, and broiler litter manures, in reducing phosphorus (P) solubility and potential impact on water quality. At a rate of 400 g/kg, FBC reduced water soluble P by 60% for dairy and swine and 50% for broiler litter, as compared to un-treated control samples. Byproduct FGD had little effect when amended into dairy manure, but reduced water soluble P by nearly 80% when amended into swine and broiler manure at a rate of 250 g/kg. The amount of Ca added in the amendments together with pH of the mixture is the major contributing factor in soluble P reduction. Sequential extraction results showed that the flyash treatments shifted water soluble P into mainly bicarbonate extractable P. The latter is still considered available for crop uptake but less vulnerable for environmental losses. Coal combustion byproducts, when amended into manure and used properly, can provide a useful and viable option for improving nutrient management on animal farms.

04/01038 Investigation of polycyclic aromatic hydrocarbon compounds (PAHs) on flue gas desulfurization (FGD) by-product: Sun, P. and Weavers, L. K. Preprints of Symposia — American Chemical Society, Division of Fuel Chemistry, 2003, 48, (1), 432–433

04/01038 Investigation of polycyclic aromatic hydrocarbon compounds (PAHs) on flue gas desulfurization (FGD) by-product: Sun, P. and Weavers, L. K. Preprints of Symposia — American Chemical Society, Division of Fuel Chemistry, 2003, 48, (1), 432–433