Flue Gas Desulfurization Products Research Articles

Flue Gas Desulfurization Products Use on Agricultural Land Use Systems

The Flue gas desulfurization (FGD) process is a set of technology that is used to remove the sulphur dioxide (SO2) present in the flue gas, which is exhausted from the thermal power plant during electricity generation. In FGD equipment, high calcium-containing sorbent materials are sprayed, which will react with the SO2 present in the flue gas and result in the formation of calcium sulphite and FGD gypsum etc. these formed waste materials are known as FGD products. The FGD products can be used in agricultural land for the amelioration of the soil acidity, salinity and alkalinity, it improves the soil’s physical property, reduce the runoff rate etc. Now a day around two per cent of generated FGD products is used in the agricultural field. As some of the FGD products may contain heavy metals, their direct use in the agriculture field may cause environmental hazards. To avoid environmental pollution before its direct use the chemical properties of the product have to be thoroughly checked. So by the use of these materials in the agricultural field, we can effectively convert waste material into useful products.

Integrated photoelectrochemical (PEC)-forward osmosis (FO) system for hydrogen production and fertigation application

This study proposes an integrated system that combines a photoelectrochemical (PEC) system and forward osmosis (FO) system in tandem operation to address water, energy, and food (WEF) scarcity. The system utilizes a combination of ammonium sulfite and ammonium sulfate solution to represent wet flue gas desulfurization products from the ammonia scrubbing process commonly used in oil and gas producing countries. Under simulated sunlight, the sulfurous solution in the PEC system is oxidized at a reduced titania nanotube array (TNA) working electrode to produce hydrogen, a clean energy source (Energy). The oxidized sulfurous solution entering the draw solution (DS) compartment of the FO unit was then diluted when the FO system operates against simulated brackish water as the feed solution (FS, Water). The DS effluent is recirculated to ensure continuous operation of both PEC and FO systems. At a certain point in time, the DS effluent is also used as a cultivation solution for basil plants, the growth is visually more favorable compared to those supplied with tap water (Food). A concentrated DS (0.8:0.2 ratio of (NH4)2SO3:(NH4)2SO4) showed excellent water desalination performance. It had a high water flux of 17 LMH with 11.8 % water recovery, highest salt rejection (98.6 % for Na+ and 98.3 for Cl−), and lowest reverse solute flux (RSF) (3.5 g‧m−2‧h−1 for SO42−, 5.25 g‧m−2‧h−1 for SO32−, 3.1 g‧m−2‧h−1 for NH4+) against 5 g‧L−1 NaCl FS for 5 h, with a cathodic current density of 0.15 A‧cm−2. Overall, this study demonstrates the successful implementation of a bench-scale integrated system that produces tangible outcomes for water, energy, and food.

Early age hydration behavior of portland cement-based binders incorporating fly ash contaminated with flue gas desulfurization products

Fly ash co-mingled with flue gas desulfurization (FGD) products are currently discarded as off-specification materials based on their high SO3 content. However, previous studies have shown that performance of these fly ashes varies significantly based on FGD product type and as such they may be viable for use in low-CO2 concrete as supplementary cementitious materials (SCMs). In this study, fly ashes with three different types of FGD products including calcium sulfite hemihydrate, calcium sulfate (with some unreacted lime), and sodium sulfate (with some unreacted sodium carbonate) were evaluated. The early age hydration behavior in blended cementitious systems at 20% cement replacement level was studied using Vicat setting time tests, isothermal calorimetry, in-situ quantitative X-ray diffraction, and pore solution analysis. The cause of the setting time retardation and flash setting observed in fly ashes with calcium sulfite hemihydrate and sodium carbonate, respectively, were identified and suitable beneficiation options were suggested for the valorized use of these materials in low-CO2 concrete.

Evaluation and beneficiation of high sulfur and high alkali fly ashes for use as supplementary cementitious materials in concrete

Coal-fuel power plants with semi-dry or dry flue gas desulfurization (FGD) systems produce high sulfur and/or high alkali fly ashes due to comingling of fly ash with FGD products. Such fly ashes do not meet the SO3 content limit (5.0% max.) of ASTM C618 or are unable to mitigate the alkali-silica reaction. The mineralogy of the sulfur present in these ashes can vary significantly (e.g., CaSO4, CaSO3, Na2SO4) based on the FGD technology used and this affects the performance of these fly ashes in concrete. Thus, the single SO3% limit of ASTM C618 is unable to capture the complexity and performance of fly ash, and this results in elimination of potentially viable pozzolans for concrete. This study performs a systematic investigation of the effect of SO3 type and content in fly ash on various performance parameters of cement-fly ash pastes and mortars, including workability (flow and flow retention), pore fluid pH, setting time, strength development, and potential for deleterious expansion. To better quantify and understand these effects, the study considers both real and doped fly ashes (i.e., a blend of specification-compliant fly ash with target sulfur compounds). The poor performance observed in the case of setting time and pore fluid pH was successfully mitigated using chemical admixtures.

Mercury emissions from polish pulverized coalfired boiler

The current paper presents the research results carried out at one of Polish power plants at a pulverized hard coal-fired 225 MW unit. The research was carried out at full load of the boiler (100% MCR) and focused on analysis of mercury content in the input fuel and limestone sorbent for wet flue gas desulfurization (FGD) system, as well as investigation of mercury content in the combustion products, i.e. fly ash, slag, FGD product (gypsum) and FGD effluents (waste). Within the framework of the present study the concentration of mercury vapor in the exhaust gas was also investigated. The analysis was performed using Lumex RA-915+ spectrometer with an attachment (RP-91C). The measurements were carried out at three locations, i.e. before the electrostatic precipitator (ESP), downstream the ESP, and downstream the wet FGD plant. Design of the measurement system allowed to determine both forms of mercury in the flue gas (Hg 0 and Hg 2+ ) at all measurement locations.Based on the measurement results the balance of mercury for a pulverized coal (PC) boiler was calculated and the amount of mercury was assessed both in the input solids (fuel and sorbent), as well as the gaseous and solids products (flue gas, slag, ash, gypsum and FGD waste).

Surface coal mine land reclamation using a dry flue gas desulfurization product: Short-term and long-term water responses

Abandoned coal-mined lands are a worldwide concern due to their potential negative environmental impacts, including erosion and development of acid mine drainage. A field study investigated the use of a dry flue gas desulfurization product for reclamation of abandoned coal mined land in USA. Treatments included flue gas desulfurization product at a rate of 280Mgha−1 (FGD), FGD at the same rate plus 112Mgha−1 yard waste compost (FGD/C), and conventional reclamation that included 20cm of re-soil material plus 157Mgha−1 of agricultural limestone (SOIL). A grass-legume sward was planted after treatment applications. Chemical properties of surface runoff and tile water (collected from a depth of 1.2m below the ground surface) were measured over both short-term (1–4yr) and long-term (14–20yr) periods following reclamation. The pH of surface runoff water was increased from approximately 3, and then sustained at 7 or higher by all treatments for up to 20yr, and the pH of tile flow water was also increased and sustained above 5 for 20yr. Compared with SOIL, concentrations of Ca, S and B in surface runoff and tile flow water were generally increased by the treatments with FGD product in both short- and long-term measurements and concentrations of the trace elements were generally not statistically increased in surface runoff and tile flow water over the 20-yr period. However, concentrations of As, Ba, Cr and Hg were occasionally elevated. These results suggest the use of FGD product for remediating acidic surface coal mined sites can provide effective, long-term reclamation.

Enzyme activities in soil treated with sulfite- or sulfate-based flue gas desulfurization products

A study was conducted to examine the impact of synthetic calcium sulfite (CaSO3 · 0.5H2O) and calcium sulfate (CaSO4 · 2H2O, i.e., gypsum) from flue gas desulfurization (FGD) on soil enzyme activities, used as soil quality indicators, following land application. We used application rates of 0, 1.12 Mg ha−1 of FGD-CaSO3 (CaS-1.12T), 3.36 Mg ha−1 of FGD-CaSO3 (CaS-3.36T), and 1.12 Mg ha−1 of FGD-gypsum (Gyp-1.12T). The field experiments were conducted on a silt loam soil with 1.6 % total C and a pH of 6.5. No crop was grown during the experiment. The concentration of water soluble SO4 2−-S and the associated electrical conductivity (EC) significantly increased during the first 2 weeks following gypsum application but decreased later on (2–4 weeks) due to leaching. There was no significant difference between the Gyp-1.12T and CaS-1.12T treatment after approximately 2 weeks indicating all of the sulfite in the CaS-1.12T treatment was completely oxidized to sulfate. In contrast, the sulfite treated with highest application rate (CaS-3.36T) was not completely oxidized within the 12-week experimental period. Application of FGD-CaSO3 and FGD-CaSO4 did not negatively affect C and N mineralization because β-glucosidase and β-d-glucosaminidase activities did not show any negative change compared with the control. Arylsulfatase activity of the CaS-1.12T treatment markedly declined compared with Gyp-1.12T and control, but then increased after 2 weeks. The arylsulfatase activity reduction, however, persisted for the duration of the experiment in the CaS-3.36T treatment. These activity changes were similar to the observed oxidation pattern of sulfite to sulfate, which indicated that arylsulfatase activity could be used as an indicator for the extent of sulfite oxidation in soil.

English

Coal combustion byproducts (CCBs) disposed of in unlined landfills can affect the quality of adjacent water resources. In previous studies, CCBs have been found to leach toxic heavy metals such as arsenic, mercury, and lead into groundwater. CCBs include fly ash, bottom ash, and flue-gas desulfurization product (FGD gypsum). Within a landfill, CCBs may be present at different densities associated with depth, compacted primarily from the weight of above materials. This investigation focused on determination of the unsaturated and saturated hydraulic properties of fly ash and bottom ash as a function of density and thus a function of depth within a landfill. Ash samples from a power plant in northern New Mexico were collected for laboratory analysis. Compressibility curves were developed in order to determine what densities may be experienced at a range of pressures. Saturated hydraulic conductivity was determined using falling head tests for multiple densities of each material. Moisture characteristic curves were developed from hanging column tests, pressure plate tests, dew point potentiometer measurements, and relative humidity measurements. The moisture characteristic curves were also measured at a range of densities for each material. Results indicated that the fly ash saturated hydraulic conductivity varied as a function of density for the materials tested and the density could be reasonably predicted using an equation presented. Fly ash unsaturated properties also show trends with variations in density with the variability decreasing as density increases. Fly ash in a landfill can have estimated density, unsaturated and saturated hydraulic properties as a function of depth using the methods in this paper. Bottom ash showed similar trends in compressibility with less variability with respect to the fly ash. The unsaturated and saturated hydraulic properties show some trends, though with high amounts of variability. The density of bottom ash materials in a landfill may be reasonably estimated using methods proposed in this study while unsaturated and saturated hydraulic properties have greater uncertainty.

Minesoil Response to Reclamation by Using a Flue Gas Desulfurization Product

Mine lands are an environmental concern worldwide because of their potential strong negative impact on water and soil quality. A field study was conducted to assess the use of a dry flue gas desulfurization (FGD) product for reclamation of an abandoned surface coal mine in Ohio. The FGD product was an atmospheric fluidized bed combustion residue and was applied to the graded mine site at 280 Mg ha-1, both alone and in combination with 112 Mg ha-1 yard waste compost, and was compared with conventional reclamation with 20 cm of borrow soil plus 157 Mg ha-1 of agricultural limestone. A grass-legume sward was planted, and soil physical and chemical properties and β-glucosidase activity were measured over both short- (1–4 yr) and long-term (15–17 yr) periods following reclamation. Soil pH at 0- to 20-cm depth increased from 3.1 to approximately neutral and was sustained at this level for 15 yr. Compared with the conventional reclamation, extractable Ca, S, B, and Zn concentrations at 0- to 20-cm depth were generally increased by the treatments with FGD product, while other extractable trace metals measured were generally not increased in short- or long-term measurements. Seventeen years after reclamation, β-glucosidase activity had increased in all three treatments at 0- to 5- and 5- to 10-cm depths compared with an adjacent untreated area. Furthermore, β-glucosidase activity more than doubled in the treatments with FGD product compared with the conventional soil treatment at 0- to 5-cm depth. These results suggest that the use of high lime FGD products for reclamation of acid coal mine lands can provide effective long-term reclamation.

An electrochemical membrane reactor for a recycled FGD process

In the current process of removing sulfur dioxide, the high cost and treatment of fuel-gas desulfurization products are still the two bottlenecks that need to be resolved. This paper presents a novel method that can regenerate the adsorbent and obtain resources and energy recovery from FGD (Flue gas desulfurization) products by using an electrochemical membrane reactor. The effects of the operating parameters, such as the current, the initial concentration of the three chambers, the flow rate, and the power supply mode on the regeneration and current efficiency were analyzed, and the optimal operating condition of the lab-scale electrochemical membrane reactor was obtained. Under this optimal condition, the current efficiency of H2SO4 production and NaOH regeneration were about 85% or above and as high as 90% correspondingly. In addition, the process cost from the consumption of energy is estimated to be 0.81$/kg sulfur; therefore, the profit from the electrolytic products is higher than the price of the electricity. Notably, the method is appealing both because it can expediently regenerate the adsorbent with no secondary pollution and because it is economically attractive.

Surface coal mine land reclamation using a dry flue gas desulfurization product: Long-term biological response

Abandoned surface coal mined lands are a worldwide environmental concern due to their low productivity and potential negative impact on water and soil quality. A field study was conducted to investigate the use of a dry flue gas desulfurization (FGD) product, i.e. a fluidized bed combustion (FBC) product, for reclamation of an abandoned surface coal mined land in Ohio, USA. The FGD product was applied to the mine site at a rate of 280Mgha−1 alone or with 112Mgha−1 yard waste compost, and these treatments were compared to a conventional reclamation treatment that included 20cm of resoil material plus 45Mgha−1 of agricultural limestone. A grass-legume sward was planted, and plant biomass yields and elements in plant tissues were determined as long as 16years after treatments. Bacterial populations and diversity and microbial biomass C in the reclaimed surface coal mined land were analyzed in the 16th year after treatments. Compared with the conventional soil treatment, plant biomass on plots treated with FGD product was lower in the first and third years, not different in the 14th year, and higher in the 16th year after application. Magnesium, S, Mo and B concentrations in plant tissues were increased by the treatments with FGD product in the first three years but not in the 14th year after application, and the heavy metals measured were not significantly increased. Bacterial populations and diversity and microbial biomass C in the reclaimed coal mine plots were significantly increased compared to adjacent untreated area and were generally similar among reclamation treatments. These results suggest that use of FGD product, used alone or in combination with compost, for reclamation of acidic surface coal mined lands can provide effective, long-term remediation.

Mineralogical Associations of Mercury in FGD Products

The natural mode of retention of mercury (Hg) in flue gas desulfurization (FGD) gypsum used in wallboard manufacturing has been investigated using a series of phase-targeted reagents. The sequence ...

Use of Industrial By-products to Sorb and Retain Phosphorus

The potential of six industrial by-products for use as phosphorus-sorbing materials (PSMs) in solutions was evaluated. These included two different acid mine drainage treatment residuals (AMDR1 and AMDR2), water treatment residual (WTR), fly ash, bauxite mining residual, and flue gas desulfurization product (FGD). Characterization of the by-products and their mechanisms for sorption and retention of inorganic phosphorus (P) from solution identified those PSMs that sorbed primarily by an iron and aluminum (Fe/Al) mechanism, those that sorbed primarily by a calcium and magnesium (Ca/Mg) mechanism, and those that sorbed by both mechanisms. Degree of P sorption and associated mechanisms were strongly influenced by the pH, buffer capacity, ionic strength, and common ion effects.

Laboratory Investigation of Hg Release from Flue Gas Desulfurization Products

Flue gas desulfurization (FGD) is a process applied to remove acid deposition precursors from the coal combustion air stream. This process also removes mercury (Hg) resulting in accumulation of this element in FGD produced solids. This project investigated Hg release from FGD materials to the air and water. Hg concentrations in the synthetic leaching precipitation procedure extracts, designed to simulate rainwater pH conditions, were in general <10 ng L(-1). Unlike coal fly ash, which has been found to adsorb Hg from the air, FGD materials were found to release Hg to the air over time with the addition of water a dominant environmental factor promoting release. The chemistry of the atmosphere to which the FGD materials were exposed (i.e., air Hg concentration and presence of oxidants), as well as that of the material (i.e., salts removed), was found to influence the magnitude of emissions. Although this work showed a component of the Hg captured by the FGD process could be released to the air under laboratory conditions, the potential for release under disposal and beneficial use conditions needs to be determined.

Mercury speciation in gypsums produced from flue gas desulfurization by temperature programmed decomposition

Temperature programmed decomposition was used to identify mercury (Hg) species in gypsum samples produced from flue gas desulfurization in two Spanish power stations (A and B). As stricter emission control/reduction policies, particularly those focusing on Hg, are being implemented, wet flue gas desulfurization (FGD) technologies used for the removal of SO 2 can result in the co-removal of highly-soluble oxidized Hg. The amount of Hg retained in FGD products may increase in the future if these units are optimized for co-capture. For this reason, it is important to identify the mercury species in FGD products not only to determine the potential risk when the wastes are finally disposed of, but also to understand the behaviour of mercury during combustion and therefore to improve the technologies for mercury removal. Different mercury species were identified in the gypsum samples. In power station A, HgS were the most probable Hg species, whereas in power station B the main compound was Hg halogenated compounds.

Flue Gas Desulfurization Products as Sulfur Sources for Corn

Nitrogen deficiency in the soil often limits corn (Zea mays L.) production. Recently, S deficiency in several crops, including corn, has been observed. Little information is available, however, related to the interactive effects of N and S fertilization on corn growth and yield using modern corn hybrids. Field experiments were conducted from 2002 to 2005 to test corn response to seven rates (0–233 kg ha−1) of N and two rates (0 and 33 kg ha−1) of S applied to a silt loam soil at Wooster, OH. The S was applied as flue gas desulfurization (FGD) products and was primarily in the form of gypsum. Corn grain yields were significantly (P ≤ 0.05) increased by N fertilizer addition from 2003 to 2005. Sulfur addition also significantly increased the average yield of corn in 2002 and 2003. An N × S interaction for corn yield was observed in 2005. Sulfur application at 33 kg ha−1 significantly (P ≤ 0.05) increased corn yield at the intermediate N rate of 133 kg ha−1, and showed a general tendency to increase yield at lower N rates in 2004 and 2005. Nitrogen and S concentrations in corn grain were increased by application of 200 kg N ha−1, and S concentration was increased by S application in 2005. These results suggest that application of S fertilizer, with N, can promote the uptake of N by corn in S‐responsive soils. This will decrease the amount of N required for high‐yield corn production and reduce production costs and degradation of water quality associated with oversupply of N.

Oxidation of FGD-CaSO 3 and effect on soil chemical properties when applied to the soil surface

Use of high-sulfur coal for power generation in the United States requires the removal of sulfur dioxide (SO 2) produced during burning in order to meet clean air regulations. If SO 2 is removed from the flue gas using a wet scrubber without forced air oxidation, much of the S product created will be sulfite ( SO 3 2 - ). Plants take up S in the form of sulfate ( SO 4 2 - ). Sulfite may cause damage to plant roots, especially in acid soils. For agricultural uses, it is thought that SO 3 2 - in flue gas desulfurization (FGD) products must first oxidize to SO 4 2 - in soils before crops are planted. However, there is little information about the oxidation of SO 3 2 - in FGD product to SO 4 2 - under field conditions. An FGD-CaSO 3 was applied at rates of 0, 1.12, and 3.36 Mg ha −1 to the surface of an agricultural soil (Wooster silt loam, Oxyaquic Fragiudalf). The SO 4 2 - in the surface soil (0–10 cm) was analyzed on days 3, 7, 17, 45, and 61. The distribution of SO 4 2 - and Ca in the 0–90 cm soil layer was also determined on day 61. Results indicated that SO 3 2 - in the FGD-CaSO 3 rapidly oxidized to SO 4 2 - on the field surface during the first week and much of the SO 4 2 - and Ca moved downward into the 0–50 cm soil layer during the experimental period of two months. It is safe to grow plants in soil treated with FGD-CaSO 3 if the application is made at least three days to several weeks before planting.

Mercury in gypsum produced from flue gas desulfurization

Wet flue gas desulfurization (FGD) technologies used to remove sulfur dioxide (SO 2) from combustion gases can be effective in capturing oxidized mercury (Hg). Depending on the FGD process, a large portion of this Hg may be incorporated into the FGD slurry and its solid byproducts including synthetic gypsum, a material commonly used in the manufacturing of wallboard. The potential for atmospheric and groundwater releases of Hg arises during the manufacturing processes, during the preparation and use of the manufactured products, and eventually upon disposal of the wallboard or other products. In this paper, the fate and mobility of Hg in FGD products and process streams were investigated. Experimental approaches, including leaching studies and size separation techniques, were used to investigate products including FGD-outlet slurry and wallboard production line samples. Results of the experiments reported here indicate that, in a number of cases, Hg mobility is limited. Further, the agent responsible for the immobilization appears to be not the finer particles of gypsum itself but an iron-rich phase, such as iron coated clay minerals or iron oxide/hydroxide particles, probably introduced with the limestone used to form the SO 2-capture reagent.

06/01136 Mineralogical and engineering characteristics of dry flue gas desulfurization products: Bigham, J. M. et al. Fuel, 2005, 84, (14–15), 1839–1848

06/01136 Mineralogical and engineering characteristics of dry flue gas desulfurization products: Bigham, J. M. et al. Fuel, 2005, 84, (14–15), 1839–1848

Mineralogical and engineering characteristics of dry flue gas desulfurization products

Fifty-nine coal combustion products were collected from coal-fired power plants using various dry flue gas desulfurization (FGD) processes to remove SO 2. X-ray diffraction analyses revealed duct injection and spray dryer processes created products that primarily contained Ca(OH) 2 (portlandite) and CaSO 3·0.5H 2O (hannebachite). Most samples from the lime injection multistage burners process contained significant amounts of CaO (lime), CaSO 4 (anhydrite), and CaCO 3 (calcite). Bed ashes from the fluidized bed process were often dominated by CaSO 4 but also contained CaCO 3, CaO (lime), and MgO (periclase). Cyclone ashes were similar in composition to the bed ashes but contained more unspent sorbent and CaSO 4 and less MgO. Fly ash in all samples ranged from 10 to 79 wt%. Samples usually exhibited two distinct swelling episodes. One occurred immediately after water was applied due to hydration reactions, especially the conversion of CaO to Ca(OH) 2 and CaSO 4 to CaSO 4·2H 2O (gypsum). The second began between 10 and 50 d later and involved formation of the mineral ettringite (Ca 6[Al (OH) 6](SO 4) 3·26H 2O). The final pH after 112 d ranged from 10.0 to 12.1. If samples are incubated under ‘closed’ (i.e. incomplete recarbonation with atmospheric CO 2) and alkaline weathering conditions, gypsum and portlandite are initially formed followed by the conversion of the gypsum to ettringite. Closed, alkaline conditions typically can occur when FGD products are placed in confined settings such as a road embankment or buried as a discrete layer as occurs in some surface mine reclamation projects.