How does a wet fgd work

GRP absorbers and reinforced concrete absorbers with polypropylene linings are used in addition to the proven steel absorbers with a variety of inner linings or stainless steel.

Following prototyping and test plant work, we can now refer to operation at a pilot plant under actual power station conditions. ANDRITZ delivers environmentally friendly flue gas cleaning solutions, tailored to the needs of our clients and their operating environments. Our products range from flue gas scrubbers and SCRs for power stations to complex flue gas cleaning systems for waste-to-energy and industrial plants. The global economy is in constant need of power, which is still mainly provided by coal, oil and gas — fossil fuels that are finite and harmful to the environment over their whole value chain.

Other more sustainable resources such as municipal waste or sludge have started to establish their position in the industry and are gaining more attention now due to the global effort to develop and install solutions that will minimize CO2 emissions. ANDRITZ power plant service experts work in close cooperation with customers to improve the safety, performance, stability, availability, and efficiency of power generation equipment.

Wet flue gas cleaning, limestone FGD. Silica SiO 2 is the primary component of sand, and although the grains within limestone deposits are typically very fine they still represent inert material that reduces the quality of the limestone.

Thus, for any given amount of limestone delivered to the plant, higher silica content equates to a reduction in available active content. Inert materials can also cause other difficulties, most notably regarding product separation.

Hydrocyclones or hydroclones, for short are commonly utilized in scrubbing systems to separate heavier, fully-reacted gypsum solids from lighter intermediate compounds and partially-reacted limestone see Figure 1. Orifices at the overflow and underflow discharge ports are set to provide maximum efficiency. If the inert content of the limestone changes substantially, the inerts, and the density change they impart, can influence hydroclone operation and reduce efficiency.

Inert issues may also arise from chemistry that is seemingly deceptive. Some limestone formations contain a high concentration of dolomite CaCO 3 -MgCO 3 , where a substantial portion of the calcium and magnesium carbonate exists in a molecular ratio.

These deposits may have well over 90 percent combined carbonate content. A first thought might be that this material would be great in a scrubber, but dolomite is quite un-reactive.

Thus, un-reacted dolomite can behave like inerts in the scrubber and also reduce the value of the raw product. Two other impurities that can cause difficulties are iron Fe and manganese Mn. Iron is usually found in higher concentrations than its cousin, Mn.

Both of these compounds will catalyze the oxidation of intermediate reaction products to gypsum and can cause severe scaling in scrubbers that are not forced oxidized. Iron and manganese can also negatively influence filtration systems for byproduct dewatering.

Land application uses for dry FGD by-products. Phase 2 report. A study was initiated in December to demonstrate large volume beneficial uses of flue gas desulfurization FGD by-products. A Phase 1 report provided results of an extensive characterization of chemical, physical, mineralogical and engineering properties of 58 dry FGD by-product samples. The Phase 1 report concluded that high volume beneficial reuses will depend on the economics related to their ability to substitute for existing materials for various types of applications e.

Phase 2 objectives were 1 to conduct laboratory and greenhouse studies of FGD and soil spoil mixtures for agronomic and engineering applications, 2 to initiate field studies related to high volume agronomic and engineering uses, and 3 to develop the basic methodological framework for estimation of the financial and economic costs and benefits to society of several FGD reuse options and to make some preliminary runs of economic models.

High volume beneficial reuses of dry FGD by-products have been successfully demonstrated. Adverse environmental impacts have been negligible. Also much of what we have learned from studies on dry FGD by-products is applicable to the more prevalent wet FGD by-products. The adaptation of the technologies demonstrated in this project seem to be not only limited by economic constraints, but even more so, by the need to create awareness of the market potential of using these FGD by-products.

It is expected that this data will provide the basis for fundamental scientific insights into the nature of mercury chemistry in flue gas, the catalytic effect of SCR systems on mercury speciation and the efficacy of different FGD technologies for mercury capture. This document, the tenth in a series of topical reports, describes the results and analysis of mercury sampling performed on two MW units burning bituminous coal containing 1.

The Utility flue gas desulfurization FGD Survey report, which is generated by a computerized data base management system, represents a survey of operational and planned domestic utility flue gas desulfurization FGD systems.

The primary objective of IEC is to minimize the occurrence of stack liquid discharge and avoid the discharge of large droplets, in order to prevent acid rain around the stack. Liquid discharge from the stack is the integrated outcome of two-phase processes , which are discussed in this work. In order to estimate droplets discharge the present investigation employs analytical models, empirical tests, and numerical calculations of two-phase phenomena. The two-phase phenomena are coupled and therefore cannot be investigated separately.

Sparing analysis for FGD systems. With the passage of federal clean air legislation, utilities will be evaluating the capability of various flue gas desulfurization FGD system design configurations and operating scenarios to meet sulfur dioxide SO 2 removal goals. The primary goal in reviewing these alternatives will be to optimize SO 2 removal capability in relation to power production costs. The FGD Analysis System can be used to evaluate different design configurations for new systems or to calculate the effect of changes in component reliability for existing FGD systems.

The user interactively enters FGD design data, unit SO 2 generation-level data, and FGD chemical additive-level data for the design configuration to be evaluated. The system then calculates expected SO 2 removal capability and operating cost data for operation of the design configuration over a user specified time period. This paper provides a brief description of the FGD Analysis System and presents sample results for three typical design configurations with different redundancy levels.

Wet flue gas desulphurization and new fuels. This thesis describes experimental and theoretical investigations of wet flue gas desulphurization FGD. A review of the current knowledge of the various rate determining steps in wet FDG plants is presented. The mechanism underlying the rate of dissolution of finely grained limestone particles was examined in a laboratory batch apparatus using acid titration. Three Danish limestones of different origin were tested.

A transient, mass transport controlled, mathematical model was developed to describe the dissolution process. Model predictions were found to be qualitatively in good agreement with experimental data. Empirical correlations for the dimensionless mass transfer coefficients in a pilot plant falling-film column were determined. A detailed model for a wet FGD pilot plant, based on the falling film principle, was developed. The possibility of co-firing straw and coal was investigated in a full-scale power plant.

No effects on the overall performance of the wet FGD plant were observed, though laboratory experiments with fine dust and fly ash from the full-scale experiments showed a decrease in limestone reactivity. EG EFP The objectives are 1 to evaluate the effect of SCR on mercury capture in the ESP- FGD and SDA-FF combinations at coal-fired power plants, 2 evaluate the effect of catalyst degradation on mercury capture; 3 evaluate the effect of low load operation on mercury capture in an SCR- FGD system, and 4 collect data that could provide the basis for fundamental scientific insights into the nature of mercury chemistry in flue gas, the catalytic effect of SCR systems on Hg speciation and the efficacy of different FGD technologies for Hg capture.

This document, the second in a series of topical reports, describes the results and analysis of mercury sampling performed on a MW unit burning a bituminous coal containing 1. Four sampling tests were performed in March Due to mechanical problems with the boiler feed water pumps, the actual gross output was between and MW during the tests.

Mercury removal, on a. Synthesis on research results of FGD gypsum briquetting. Directory of Open Access Journals Sweden. Full Text Available FGD gypsum products can be characterized by significant solubility in water and dusting in dry state.

These characteristics can cause a considerable pollution of air, water and soil. Among many approaches of preparing utilization of this waste, the process of compaction using briquetting has proved to be very effective. Using FGD gypsum products a new material of fertilizers characteristics has been acquired and this material is resistant to the conditions of transportation.

This paper presents results of experimental briquetting of flue gas desulphurisation products in a roll press. The experiments were conducted in a laboratory roll presses LPW and LPW equipped with two interchangeable forming rings that form material into saddle-shaped briquettes with volume 6,5 cm3 and 85 cm3. The experiments were conducted with various percentage amounts of FGD gypsum moisture. The results provided information regarding influence of moisture and roll press configuration on quality of briquettes.

On the basis of obtained results, technological process and a general outline of technological line for FGD gypsum were developed. Two roll presses of own construction with different outputs were identified as appropriate for this purpose. A range of necessary works related to their adaptation for the FGD gypsum briquetting were pointed out.

Massive quantities of sulfite-rich flue gas desulfurization FGD scrubber materials are produced every year in the USA. In fact, at present, the production of wet sulfite-rich scrubber cake outstrips the production of wet sulfate-rich scrubber cake by about 6 million tons per year. However, most of the utilization focus has centered on FGD gypsum.

Therefore, we have recently initiated research on developing new strategies for the economical, but environmentally-sound, utilization of sulfite-rich scrubber material. In this exploratory project Phase I , we attempted to ascertain whether it is feasible to develop reconstituted wood replacement products from sulfite-rich scrubber material. In pursuit of this goal, we characterized two different wet sulfite-rich scrubber materials, obtained from two power plants burning Midwestern coal, for their suitability for the development of value-added products.

The overall strategy adopted was to fabricate composites where the largest ingredient was scrubber material with additional crop materials as additives.

Our results suggested that it may be feasible to develop composites with flexural strength as high as 40 MPa psi without the addition of external polymers. We also attempted to develop load-bearing composites from scrubber material, natural fibers, and phenolic polymer. The formulated composites showed flexural strengths as high as 73 MPa 10, psi. We plan to harness the research outcomes from Phase I to develop parameters required to upscale our value-added products in Phase II.

Ohio State Univ. Water Resources Div. The amendments to the Clean Air Act have spurred the development of flue gas desulfurization FGD processes , several of which produce a dry, solid by-product material consisting of excess sorbent, reaction products containing sulfates and sulfites, and coal fly ash.

Presently FGD by-product materials are treated as solid wastes and must be landfilled. However, landfill sites are becoming more scarce and tipping fees are constantly increasing. It is, therefore, highly desirable to find beneficial reuses for these materials provided the environmental impacts are minimal and socially acceptable. The purpose of the Phase 1 portion of the project was to characterize the chemical, physical, mineralogical and engineering properties of the FGD by-product materials obtained from various FGD technologies being developed in the state of Ohio.

Phase 1 also involved the collection of baseline economic data related to the beneficial reuse of these FGD materials. A total of 58 samples were collected and analyzed. In summary Phase 1 results revealed that FGD by-product materials are essentially coal fly ash materials diluted with unreacted sorbent and reaction products. High volume beneficial reuses will depend on the economics of their substituting for existing materials for various types of applications e. Environmental constraints to the beneficial reuse of dry FGD byproduct materials, based on laboratory and leachate studies, seem to be less than for coal fly ash.

Microbiological treatment for removal of heavy metals and nutrients in FGD wastewater. Shulder, Stephen J. Chloride chlorine in the fuel becomes dissolved and increases in the absorber loop, which can lead to a more corrosive environment. Inert matter in the limestone also enters the absorber and must be reduced to meet the gypsum quality specification.

To control the buildup of chloride and fines in the flue gas desulfurization FGD system a continuous blowdown or purge stream is utilized.

Environmental regulations on the discharge of treated FGD wastewater are becoming increasingly more stringent to control impacts on the receiving body of water stream, lake, river, or ocean.

These new limitations often focus on heavy metals such as selenium and nutrients including nitrogen and phosphorus compounds. The FGD chloride purge stream is typically treated by chemical addition and clarification to remove excess calcium and heavy metals with pH adjustment prior to discharge. However this process is not efficient at selenium or nutrient removal.

Information on a new approach using biological reactor systems or sequencing batch reactors SBRs to achieve reductions in selenium and nitrogen compounds ammonia, nitrite, and nitrate is discussed. Part 2 of this manual provides the electric utility engineer with detailed technical information on some of the major mechanical equipment used in the FGD system.

The objectives of Part 2 are the following: to provide the electric utility engineer with information on equipment that may be unfamiliar to him, including ball mills, vacuum filters, and mist eliminators; and to identify the unique technique considerations imposed by an FGD system on more familiar electric utility equipment such as fans, gas dampers, piping, valves, and pumps. Part 3 provides an overview of the recommended procedures for evaluating proposals received from FGD system vendors.

The objectives are to provide procedures for evaluating the technical aspects of proposals, and to provide procedures for determining the total costs of proposals considering both initial capital costs and annual operating and maintenance costs. Part 5 is a case study in using this manual in the preparation of a purchase specification and in the evaluation of proposals received from vendors. The objectives are to demonstrate how the information contained in Parts 1 and 2 can be used to improve the technical content of an FGD system purchase specification; to demonstrate how the techniques presented in Part 3 can be used to evaluate proposals received in response to the purchase specification; and to illustrate how the FGDPRISM computer program can be used to establish design parameters for the specification and evaluate vendor designs.

Simulation studies of the influence of HCl absorption on the performance of a wet flue gas desulphurisation pilot plant. The mathematical model of Kiil et al, Ind. Eng, Chem. In contrast to earlier models for wet FGD plants, the inclusion of population balance equations Compaction of FGD -gypsum.

It is shown that it is possible to produce compacted gypsum with a low porosity and a high strength on a laboratory scale by uniaxial compaction of flue gas desulphurization FGD - gypsum powder. Compacted FGD -gypsum cylinders were produced at a compaction pres-sure between 50 and MPa yielding.

Extension of the possibilities for disposal of the flue gas desulfurization FGD gypsum by the development of a process for the production of FGD gypsum.

In the course of this research project a completly new transformation of FGD -gypsum into FGD -anhydrite has been studied. The reaction is catalysed by small quantities of sulphuric acid resulting in a FGD -anhydrite without combined water and with an orthorhombic crystal lattice. The course of reaction was thoroughly investigated by laboratory test and hypothesis have been put forward. The process engineering has been developed from laboratory to pilot plant scale.

The FGD -anhydrite is technologically a novel product. The idea was to create it for cement industry as well as to put it on the filler market as a raw product. In principle, FGD -anhdrite will be suitable for the use in the cement industry due to its characteristics. However, it is not interesting for this market in this moment.

With respect to the filler industry, this application will enable a further-reaching usability of the FGD -gypsum than the traditional scope of the gypsum industry. First experiments show that the specific properties of processed FGD -anhydrite may qualify it as a high-grade filler. With 18 refs. Krishnakumar, Balaji; Naik, Chitralkumar V. Coal and Environment Research Lab. This paper presents validations of the Hg speciation predicted by NEA's MercuRator trademark package with an American field test database for 28 full-scale utility gas cleaning systems.

The validations for ACI applications demonstrated that Hg removals can be accurately estimated for the full domain of coal quality, LOI, and ACI rates for both untreated and brominated carbon sorbents. The predictions for ACI depict the test-to-test variations in most cases, and accurately describe the impact of ACI configuration and sorbent type. At the time, this represented the largest emissions control retrofit in the industry, and consisted of two MWe units.

These units burn a low sulfur subbituminous coal from the adjacent Navajo mine. This FGD system is considered to be a second generation design. At the time, it represented state-of-the-art of FGD technology, in terms of both process considerations and materials of construction. In the six years since startup, several modifications have been made in the areas of process chemistry, equipment configuration, and materials of construction.

These modifications are applicable to the next generation of FGD systems which will be designed in response to Acid Rain Legislation.

This paper presents the original plant design basis, summarizes the operating experience to date, and identifies the modifications and improvements which have been made since startup. In addition, recommendations for new installations are offered. The U. Department of Energy and EPRI co-funded this project to improve the control of mercury emissions from coal-fired power plants equipped with wet flue gas desulfurization FGD systems.

The project has investigated catalytic oxidation of vapor-phase elemental mercury to a form that is more effectively captured in wet FGD systems. If successfully developed, the process could be applicable to over 90, MW of utility generating capacity with existing FGD systems, and to future FGD installations. Field tests were conducted to determine whether candidate catalyst materials remain active towards mercury oxidation after extended flue gas exposure.

Catalyst life will have a large impact on the cost effectiveness of this potential process. A mobile catalyst test unit was used to test the activity of four different catalyst materials for a period of up to six months each at three utility sites.

Catalyst testing was completed at the first site, which fires Texas lignite, in December ; at the second test site, which fires a Powder River Basin subbituminous coal, in November ; and at the third site, which fires a medium- to high-sulfur bituminous coal, in January Results of testing at each of the three sites were reported in previous technical notes.

At Site 1, catalysts were tested only as powders dispersed in sand bed reactors. At Sites 2 and 3, catalysts were tested in two forms, including powders dispersed in sand and in commercially available forms such as extruded pellets and coated honeycomb structures. This final report summarizes and presents results from all three sites, for the various catalyst forms tested. Field testing was supported by laboratory tests to screen catalysts for activity at specific flue gas compositions, to investigate catalyst deactivation mechanisms and methods for regenerating spent catalysts.

Laboratory results are also summarized and discussed in this report. Land application uses for dry FGD by-products, Phase 1 report. FGD by-product materials are treated as solid wastes and must be landfilled. It is highly desirable to find beneficial reuses for these materials provided the environmental impacts are minimal and socially acceptable.

Many of the elements regulated by the US Environmental Protection Agency reside primarily in the fly ash. Phase 1 results revealed that FGD by-product materials are essentially coal fly ash materials diluted with unreacted sorbent and reaction products. Environmental constraints to the beneficial reuse of dry FGD by-product materials, based on laboratory and leachate studies, seem to be less than for coal fly ash. Wirsching, F. Knauf, Westdeutsche Gipswerke, Iphofen Germany.

A completely new reaction for conversion of FGD gypsum into FGD anhydrite was investigated in the research project which forms the basis for this article. The reaction takes place with moist, finely divided, FGD gypsum with the catalytic action of small quantities of sulphuric acid at temperatures around to C. Moisture-free FGD anhydrite with an orthorhombic crystalline structure ist obtained.

The conversion of the crystalline lattice of calcium sulphate dihydrate into calcium anhydrite II takes place directly through neoformation. The reaction and its mechanism were first investigated in laboratory trials. Any finely divided calcium sulphate dihydrate is suitable as the starting material. The process development was carried out up to a semi-industrial scale and the design principles were worked out for large-scale plants at power station sites.

The directly heated rotary tube kiln proved to be a suitable reaction unit. The FGD anhydrite is obtained in this process as a dry, finely divided, product with reproducible properties. Investigations were carried out into its potential applications for the cement industry and as a raw material for producing fillers.

In principle it is suitable for the cement industry. Applications as a filler allows the FGD gypsum to extend its uses outside the traditional areas of the gypsum industry. Initial trials indicate that after a processing procedure, which was also newly developed in the laborator, FGD anhydrite processes the characteristic features necessary for a high grade filler.

Experimental investigation of a pilot-scale jet bubbling reactor for wet flue gas desulphurisation. In the present work, an experimental parameter study was conducted in a pilot-scale jet bubbling reactor for wet flue gas desulphurisation FGD.

The pilot plant is downscaled from a limestone-based, gypsum producing full-scale wet FGD plant. Important process parameters, such as slurry pH, inlet The degree of desulphurisation, residual limestone content of the gypsum, liquid phase concentrations, and solids content of the slurry were measured during the experimental series.

The SO2 removal Addition of Cl in the form of CaCl2. Application study of Bio- FGD based on environmental safety during the coal combustion. Coal combustion produces a large amount of acidic gas, which is the main cause of acid rain and other natural disasters.

Compared with the traditional chemical desulfurization technology, biological desulfurization has the advantages of low operating cost, without secondary pollution, low carbon emission and the additional economic benefits. The environmental and economic benefits of the project were greater than the traditional desulfurization technology.

With the continuous improvement of environmental safety standards, Bio- FGD technology will have broad application prospects. Interest in using gypsum as a management tool to improve crop yields and soil and water quality has recently increased.

Abundant supply and availability of flue gas desulfurization FGD gypsum, a by-product of scrubbing sulfur from combustion gases at coal-fired power plants, in major agricultural producing regions within the last two decades has attributed to this interest. Currently, published data on the long-term sustainability of FGD gypsum use in agricultural systems is limited. This has led to organization of the American Society of Agronomy's Community "By-product Gypsum Uses in Agriculture" and a special collection of nine technical research articles on various issues related to FGD gypsum uses in agricultural systems.

A brief review of FGD gypsum, rationale for the special collection, overviews of articles, knowledge gaps, and future research directions are presented in this introductory paper. The nine articles are focused in three general areas: i mercury and other trace element impacts, ii water quality impacts, and iii agronomic responses and soil physical changes. While this is not an exhaustive review of the topic, results indicate that FGD gypsum use in sustainable agricultural production systems is promising.

The environmental impacts of FGD gypsum are mostly positive, with only a few negative results observed, even when applied at rates representing cumulative year applications.

Thus, FGD gypsum, if properly managed, seems to represent an important potential input into agricultural systems. According to the American Coal Ash Association, about Out of At present, unlike its cousin FGD gypsum, the prospect for effective utilization of sulfite-rich scrubber materials is not bright. In fact, almost In our pursuit to mitigate the liability of sulfite-rich FGD scrubber materials' disposal, we are attempting to develop value-added products that can commercially compete.

More specifically, for this Innovative Concept Phase I project, we have the following objectives: to characterize the sulfite-rich scrubber material for toxic metals; to optimize the co-blending and processing of scrubber material and natural byproducts; to formulate and develop structural composites from sulfite-rich scrubber material; and to evaluate the composites' mechanical properties and compare them with current products on the market.

After successfully demonstrating the viability of our research, a more comprehensive approach will be proposed to take these value-added materials to fruition. Volume 5, A laboratory greenhouse study conducted in fulfillment of Phase 2, Objective 2 titled. Yibirin, H.

The Clean Air Act, as revised in , has spurred the development of flue gas desulfurization FGD technologies that have resulted in large volumes of wet scrubber sludges. In general, these sludges must be dewatered, chemically treated, and disposed of in landfills.

Disposal is an expensive and environmentally questionable process for which suitable alternatives must be found. Wet scrubbing with magnesium Mg -enhanced lime has emerged as an efficient, cost effective technology for SO 2 removal. When combined with an appropriate oxidation system, the wet scrubber sludge can be used to produce gypsum CaSO 4 -2H 2 O and magnesium hydroxide [Mg OH 2 ] of sufficient purity for beneficial re-use.

Product value generally increases with purity of the by-product s. Such materials may have agricultural value as soil conditioners, liming agents and sources of plant nutrients Ca, Mg, S. This report describes a greenhouse study designed to evaluate by-product gypsum and Mg gypsum from the Zimmer Station pilot plant as amendments for improving the quality of agricultural soils and mine spoils that are currently unproductive because of phytotoxic conditions related to acidity and high levels of toxic dissolved aluminum Al.

In particular, the technical literature contains evidence to suggest that gypsum may be more effective than agricultural limestone in modifying soil chemical conditions below the immediate zone of application. Representative samples of by-product gypsum and Mg OH 2 from the Zimmer Station were initially characterized.

The gypsum was of high chemical purity and consisted of well crystalline, lath-shaped particles of low specific surface area. By contrast, the by-product Mg OH 2 was a high surface area material 50 m 2 g. Volume 4, A laboratory study conducted in fulfillment of Phase 2, Objective 1 titled.

Inhibition of acid production in coal refuse amended with calcium sulfite and calcium sulfate - containing FGD solids. Hao, Y. Control of S0 2 emission from coal combustion requires desulfurization of coal before its combustion to produce coal refuse.

Acid production in coal refuse due to pyrite oxidation and disposal of large amounts of FGD can cause environmental degradation. Addition of CaS0 3 and CaS0 3 -containing FGD to coal refuse may reduce the amounts of oxygen and ferric ion available to oxidize pyrite because the sulfite moiety in CaS0 3 is a strong reductant and thus may mitigate acid production in coal refuse.

In Chapter 1, it was shown that CaS0 3 efficiently scavenged dissolved oxygen and ferric ion in water under the conditions commonly encountered in a coal refuse disposal environment. In the presence ofCaS0 3 , the concentration of dissolved oxygen in water exposed to the atmosphere declined to below 0.

Calcium sulfite also inhibited acid leaching from fresh coal refuse in bench-scale columns under controlled conditions. Removal of fine particles in wet flue gas desulfurization system by heterogeneous condensation.

Yang, L. A novel process to remove fine particles with high efficiency by heterogeneous condensation in a wet flue gas desulfurization WFGD system is presented. The condensational grown droplets were then removed by the scrubbing liquid and a high-efficiency demister. This effect can be attributed to the formation of aerosol particles in the limestone and ammonia-based FGD processes. The performance of the WFGD system for removal of fine particles can be significantly improved for both steam addition cases, for which the removal efficiency increases with increasing amount of added steam.

A high liquid to gas ratio is beneficial for efficient removal of fine particles by heterogeneous condensation of water vapor. School of Environment and Natural Resources. Sulfite may cause damage to plant roots, especially in acid soils. Phase 1, [Annual report], December 1, November 30, Risk minimisation of FGD gypsum leachates by incorporation of aluminium sulphate. Alvarez-Ayuso, E. The incorporation of aluminium sulphate to flue gas desulphurisation FGD gypsum before its disposal was investigated as a way to minimise the risk supposed by the high fluoride content of its leachates.

The impact of wet flue gas desulfurization scrubbing on mercury emissions from coal-fired power stations. This article introduces a predictive capability for Hg retention in any Ca-based wet flue gas desulfurization FGD scrubber, given mercury Hg speciation at the FGD inlet, the flue gas composition, and the sulphur dioxide SO2 capture efficiency.

A preliminary statistical analysis of data from 17 full-scale wet FGDs connects flue gas compositions, the extents of Hg oxidation at FGD inlets, and Hg retention efficiencies. These connections clearly signal that solution chemistry within the FGD determines Hg retention. A more thorough analysis based on thermochemical equilibrium yields highly accurate predictions for total Hg retention with no parameter adjustments.

With the U. The large discrepancies for older FGDs are tentatively attributed to the unspecified SO2 capture efficiencies and operating temperatures and to the possible elimination of HCl in prescrubbers. The analysis also predicts re-emission of Hg O but only for inlet O2 levels that are much lower than those in full-scale FGDs. Properties of mortars made by uncalcined FGD gypsum-fly ash-ground granulated blast furnace slag composite binder. At 90 days the mortars with FGD gypsum is dramatically smaller drying shrinkage — micro strain than that without FGD gypsum about micro strain.

The release of the SO 4 2- from the mortar was analyzed, indicating that the dissolution of sulfate increases with FGD gypsum. Development of advanced retrofit FGD designs. The Clean Air Act Amendment is a dramatic departure from previous legislation in that it affords the electric utility industry the flexibility to achieve their portion of the sulfur dioxide reduction in a myriad of ways.

Each utility must look at its system overall. One strategy which may prove beneficial is to remove as much SO 2 as possible at facilities where there is an existing flue gas desulfurization FGD system or where one is planned. A range of design options are being investigated to determine both the SO 2 collection capability and the relative cost impacts of each option. Some of the design options considered include the use of trays, packing, additional liquid flow rate, and additives to boost the removal efficiency.

These options are being investigated for limestone, and magnesium-enhanced lime systems. The sensitivity of these designs to changes in coal sulfur content, chloride content, unit size, gas velocity, and other factors are being investigated to determine how the performance of a designs is changed and the ability to meet compliance.

This paper illustrates the type of analysis used to develop the advanced designs and presents the sensitivity of a Countercurrent spray tower design using limestone and forced oxidation to changes in specific design input parameters such as boiler load, tower height, and gas velocity. In addition, slurry from a full-scale wet FGD plant, experiencing formation of flat shaped crystals and poor gypsum dewatering properties, was transferred to the pilot plant to test if the plant would now start In this work, the particle size distribution, morphology, and filtration rate of wet FGD gypsum formed in a pilot-scale experimental setup, operated in forced oxidation mode, have been studied.