Dry Flue Gas Desulfurization By-products Research Articles

Mercury Speciation of Flue Gas Desulphurization By-Products in Coal-Fired Power Plants in China

The aim of this study was to develop and examine the morphology and distribution of mercury (Hg) in flue gas desulfurization (FGD) by-product. Mercury in the coal of coal-fired power plants is concentrated in the by-products of desulfurization process, and it is widely used as an additive in cement, building materials and other industries. Due to the different stability of various forms of mercury in the environment, subsequent use of products containing desulfurization by-product additives will continue to be released into the environment, endangering human health. Therefore, it is very necessary to study the form and distribution of mercury in the by-products of desulfurization in coal-fired power plants to provide a theoretical basis for subsequent harmless treatment. For content and morphology of mercury analysis, 1 sample of dry FGD ash and 6 samples of wet FGD gypsum were analyzed. The total 7 samples were extracted using a modification of sequential chemical extractions (SCE) method, which was employed for the partitioning Hg into four fractions: water soluble, acid soluble, H2O2 soluble, and residual. The Hg analysis was done with United States Environmental Protection Agency (USEPA) method 7471B. Comparing with the wet FGD gypsums of coal-fired boilers, the total Hg content in the dry FGD by-product was as high as 1.22 mg/kg, while the total Hg content in the FGD gypsum is 0.23 - 0.74 mg/kg, which was 2 times over the wet FGD gypsum. The concentration of water soluble Hg in the dry FGD by-product was the highest amount (0.72 mg/kg), accounting for 59.02% of the total mercury. While residual Hg content was 0.16 mg/kg, only about 13.11% of the total mercury. Mercury content in FGD gypsum was expressed in the form of ρ (residual Hg) > ρ (H2O2 soluble Hg) > ρ (water soluble Hg) > ρ (acid soluble Hg). The morphology and distribution of mercury in FGD by-products is supposed to be analyzed before utilization, and the impact of mercury on the environment should be considered.

Land Application Effects of a High-Calcium, Dry Flue Gas Desulfurization By-Product on Trace Elements in Runoff from Natural Rainfall

Due to low cost and large abundance, coal continues to be one of the major energy sources for electricity generation in the USA. The dry desulfurization of flue gases during coal combustion produces a by-product that may be potentially useful as a soil amendment. However, the influence of dry flue gas desulfurization (DFGD) by-products on trace element losses with runoff from treated fields has not been well investigated. The objective of this study was to evaluate the effects of land application of a high-Ca, DFGD by-product on trace elements lost in runoff from natural rainfall events. The by-product was applied once on May 18, 2015 at 9 Mg DFGD ha−1 to small plots of a highly weathered Ultisol under managed-grassland land use in northwest Arkansas. Runoff was collected following each runoff-producing precipitation event for 1 year. Seasonal (i.e., summer (May to August), fall (August to November), winter (November to February), and spring (February to May)) runoff, annual runoff, runoff pH, and electrical conductivity did not differ significantly between DFGD treatments. Seasonal flow-weighted mean Ni concentrations and seasonal V loads were significantly greater in runoff when amended versus the unamended control when compared during at least one 3-month season by 44.5 and 86.9% for Ni and V, respectively. Based on the results of this study, it appears that land application of a high-Ca DFGD by-product at rates ≤ 9 Mg ha−1 has minimal effects on trace elements in runoff.

Dry flue gas desulfurization by-product application effects on plant uptake and soil storage changes in a managed grassland.

Environmental regulations mandate that sulfur dioxide (SO2) be removed from the flue gases of coal-fired power plants, which results in the generation of flue gas desulfurization (FGD) by-products. These FGD by-products may be a viable soil amendment, but the large amounts of trace elements contained in FGD by-products are potentially concerning. The objective of this study was to evaluate the effects of land application of a high-Ca dry FGD (DFGD) by-product on trace elements in aboveground biomass and soil. A high-Ca DFGD by-product was applied once at a rate of 9Mgha-1 on May 18, 2015 to small plots with mixed-grass vegetation. Soil and biomass were sampled prior to application and several times thereafter. Aboveground dry matter and tissue As, Co, Cr, Hg, Se, U, and V concentrations increased (P<0.05) following application, but did not differ (P>0.05) from pre-application levels or the unamended control within 3 to 6months of application. Soil pH in the amended treatment 6months after application was greater (P<0.05) than in the unamended control. Soil Ca, S, and Na contents also increased (P<0.05), following by-product application compared to the unamended control. High-Ca DFGD by-products appear to be useful as a soil amendment, but cause at least a temporary increase in tissue concentrations of trace elements, which may be problematic for animal grazing situations.

Plant uptake of major and trace elements from soils amended with a high-calcium dry flue gas desulfurization by-product

Coal combustion by-products (CCBs) are a potentially valuable source of essential plant nutrients, but CCBs also frequently contain trace elements. The objective of this greenhouse study was to evaluate the effects of soil and application rate of a high-calcium (Ca) dry flue gas desulfurization (DFGD) by-product on Bermudagrass (Cynodon dactylon L.) growth and plant tissue and soil composition. Surface horizons of two soils with contrasting texture were mixed with a high-Ca DFGD by-product at rates of 0, 2.5, 5, 10, and 15Mgha−1. Bermudagrass was allowed to grow in the soils for 119days. Concentrations of plant nutrients and selected trace elements were determined in soil and plant tissue. Plant dry matter and tissue concentrations of Ca, Mg, B, Se, Rb, and U increased as DFGD application rate increased. Concentrations of Mehlich-3-extractable soil P, Ca, Mg, S, Na, Fe, and B and strong-acid-extractable V and Hg increased with increasing application rate. Soil pH increased with application rate and electrical conductivity was only greater than that in the control at the 15Mgha−1 application rate after 119days. The DFGD by-product used in this study can be beneficially reused as a soil amendment provided soil pH and plant tissue Se concentrations are closely monitored.

Liming Characteristics of a High-Calcium Dry Flue Gas Desulfurization By-Product and a Class-C Fly Ash

Due to coal’s availability and low cost, coal combustion continues to be the United States’ primary energy source. However, coal combustion produces large quantities of waste material. Some coal combustion by-products (CCBs) have chemical and physical characteristics that make them potentially useful as soil amendments. The objectives of this study were to characterize a relatively new, high-calcium dry flue gas desulfurization (DFGD) by-product and compare its agronomic liming potential to a Class-C fly ash (FA) and reagent-grade calcium carbonate (CaCO3). Calcium car-bonate equivalence (CCE), degree of fineness (DOF), and effective neutralizing value (ENV) for each CCB were determined using standard methods. The CCBs and CaCO3 were also incubated with an acidic (~4.5) clay sub-soil at application rates equiva-lent to 0, 0.5, 1, and 2 times the soil’s lime requirement and compared to an una-mended control. Soil pH was then measured periodically during a 40-day incubation. The ENV of 79.4% for the DFGD by-product and 57.3% for the FA were comparable to those of commercially available liming materials, but were significantly lower (P

Use of clean coal combustion by-products in highway repairs

A dry flue gas desulfurization (FGD) by-product was used to reconstruct the failed portion of a highway embankment. A wall was constructed through the failure plane to stop further slippage. To evaluate the suitability of FGD by-products in this type of project, the site of the repair was divided into three test sections. In the first section, the soil removed from the slide area was recompacted and replaced according to standard construction practices. In the second section, the embankment consisted of a field-compacted mixture of soil and FGD ash in approximately equal proportions. The third section was constructed of compacted FGD by-product. All three test sections were capped by a layer of compacted boiler ash or crushed stone to provide a temporary wearing surface. Measurements of slope movement as well as water quality and levels are being made at the site to evaluate long-term embankment performance. The completion of this experiment should lead to increased acceptance of FGD by-products in construction projects. Monetary savings will be realized in avoiding some of the disposal costs for the material, as well as in the reduced reliance on alternative engineering materials.

97/01942 Transport and plant uptake of soil-applied dry flue gas desulfurization by-products

97/01942 Transport and plant uptake of soil-applied dry flue gas desulfurization by-products

TRANSPORT AND PLANT UPTAKE OF SOIL-APPLIED DRY FLUE GAS DESULFURIZATION BY-PRODUCTS

Clean air legislation has resulted in increased production of flue gas desulfurization (FGD) by-products by coal-fired boilers. Use of FGD by-products as substitutes for agricultural limestone represents a potential beneficial use alternative to landfill disposal of these materials. To determine the efficacy and potential for environmental impact of such use, an 8-month greenhouse study was conducted in which three dry FGD by-products were mixed with Wooster silt loam at rates of 0, 3.5, 7, 14, and 28 g kg−1. Separate pots were planted with alfalfa (Medicago sativa, L) and tall fescue (Festuca arundinacea, Schreb). Following a 3-month growth period, plants were harvested monthly for a total of six harvests. Pots were leached at the beginning and end of the experiment. All three FGD by-products increased soil pH from 4.5 to approximately 7.5. Leachate concentrations of Ca, Mg, and S were increased by FGD, indicating a potential for transport of these solutes to subjacent soil. Leachate Mn and Zn concentrations were decreased by FGD amendment of alfalfa, and leachate Al was decreased with both crops. Leachate trace element concentrations were not increased by FGD with the exceptions of B and Cu. Alfalfa yield was increased by FGD, although the largest amendments suppressed yields of the first two harvests. Fescue yield was also increased by FGD amendment although the response was less than with alfalfa. Plant tissue contents of Ca, Mg, and S were increased by FGD. There were no increases in tissue concentrations of any trace elements except B and Mo. Dry FGD by-products appear to be effective substitutes for agricultural limestone with little potential for adverse environmental impacts.

96/03301 - Plant growth and soil properties responses to additions of dry flue gas desulfurization byproducts

96/03301 - Plant growth and soil properties responses to additions of dry flue gas desulfurization byproducts

Dry Flue Gas Desulfurization Byproducts as Amendments for Reclamation of Acid Mine Spoil

Dry Flue Gas Desulfurization Byproducts as Amendments for Reclamation of Acid Mine Spoil

Dry Flue Gas Desulfurization Byproducts as Amendments for Acid Agricultural Soils

Dry Flue Gas Desulfurization Byproducts as Amendments for Acid Agricultural Soils