Flue Gas Desulfurization Water Research Articles

Synergistic effect of air sparging in direct contact membrane distillation to control membrane fouling and enhancing flux

• The synergistic effect of air sparging in DCMD was studied. • The introduction of air sparging enhanced flux by as much as 10%. • AS-DCMD for simulated FGD water and CaSO 4 solution showed significant reduction in fouling. • The sparged air altered the colloidal behavior of the precipitating particles. In this paper, we present the synergistic effect of air sparging in reducing membrane fouling and enhancing water vapor flux in direct contact membrane distillation (DCMD). This air sparged-DCMD (or AS-DCMD) was tested with water containing saturated CaSO 4 and simulated flue gas desulfurized (FGD) water. Polytetrafluoroethylene (PTFE) and carbon nanotube immobilized membrane (CNIM) were used in this study. The permeate flux was found to be as much as 10% higher in AS-DCMD mode compared to conventional DCMD for both membranes. The morphology of foulants deposited on the membrane were analyzed by SEM and were found to significantly different in the presence of air sparging, as the sparging altered the colloidal behavior of the precipitating salts and the amount of salt deposited during AS-DCMD was 65% lower than that observed during DCMD. Relative flux reduction measured as the drop in flux due to fouling was measured using simulated flue gas desulfurization water from coal power plants (nearly saturated with CaSO 4 ), and an 32% improvement was observed when compared to DCMD. AS-DCMD appears to be particularly suitable for desalting high salt concentration brine where both the lower flux and fouling can be important considerations.

Method of flash evaporation and condensation – heat pump for deep cooling of coal-fired power plant flue gas: Latent heat and water recovery

Flue gas waste heat recovery and utilization is an efficient means to improve the energy efficiency of coal-fired power plants. At present, the surface corrosion and fouling problems of heat exchanger hinder the development of flue gas deep cooling. In this study, a novel flue gas deep cooling method that can reduce flue gas temperature below the dew point of vapor to recover latent heat and obtain clean water simultaneously is proposed to achieve improved energy efficiency. The heat transfer mode of this method is the direct contact mode, which takes the scrubber, e.g. the flue gas desulfurization (FGD) scrubber, as the deep cooling exchanger. The flash evaporation and condensation (FEC) device and heat pump (HP) are utilized to provide low-temperature medium, such as FGD slurry or water, for washing and deep cooling flue gas, to collect recovered water, and to absorb recovered waste heat. This method is called as the FEC–HP method. This paper elaborated on two optional models of the proposed method. The mechanism for recovering heat and water was also analyzed using the customized flue gas humidity chart, and the method to quantitate recovered heat and water, as well as the results of the case of a 300MW coal-fired generator set were provided. Net present value calculations showed that this method is profitable in the scenario of burning high-water-content coals. Several potential advantages of this method and suggestions for practical application were also discussed.

Analysis of Trace Elements in Flue Gas Desulfurization Water in the Coal Combustion System and the Removal of Boron and Mercury from the Water

A detailed analysis was performed on the slurry supernatant water obtained from a wet flue gas desulfurization (FGD) system in a pilot plant of a coal combustion facility using five different coals. The determination of trace elements in those samples was performed by use of inductively coupled plasma–atomic emission spectrometry (ICP–AES), inductively coupled plasma–mass spectrometry (ICP–MS), and other methods, while the analysis of major cations and anions was conducted by ICP–AES and ion chromatography, respectively. The levels of B, Se, and Hg in the FGD water were sometimes high (44–62 mg/L for B, 0.24–0.37 mg/L for Se, and 0.11–0.23 mg/L for Hg), and these values exceeded the Japanese national effluent standards for terrestrial water (10, 0.1, and 0.005 mg/L for B, Se, and Hg, respectively). Simulated FGD water was prepared as a result of the analysis mentioned above, and the removal of those hazardous elements was attempted using various adsorbents, including N-methylglucamine resins (DIAION CRB02 and CRB05), a N-methylglucamine fiber (Chelest fiber GRY-L), an iminodiacetic acid resin (DIAION CR11), a polyamine resin (DIAION CR20), an anion-exchange resin (DOWEX 1X8), activated alumina, and activated carbon. For the simultaneous removal of B and Hg from the simulated FGD water, which contained 60 mg/L of B and 0.11 mg/L of Hg, CRB02 was the most effective and the percent removal values for B and Hg were 88 and 97%, respectively. The resulting water met the effluent standards.

Verification of lime and water glass stabilized FGD gypsum as road sub-base

Flue gas desulfurization (FGD) gypsum is a by-product created when sulfur is removed from flue gases in power plants. The utilization of FGD gypsum as a road sub-base for construction purposes is unsatisfactory when compared with other by-products such as fly ash and steel slag. As a result, FGD gypsum has generally been treated as a waste product and landfill. A new type of semi-rigid road sub-base is proposed, which is a mixture of FGD gypsum, water glass and slaked lime. Laboratory studies of moulded samples of this new material were investigated using different curing methods and measuring unconfined compressive strength, soundness and water stability. The experimental results showed that the road sub-base material reflects excellent mechanical properties and soundness durability. This contributes not only to improved road performance, but also represents a new and improved beneficial use of FGD gypsum.

Role of Equalization Basins of Constructed Wetland Systems for Treatment of Particulate-Associated Elements in Flue Gas Desulfurization Waters

Pilot-scale experiments were performed to investigate the role of equalization basins used with constructed wetland systems for treatment of flue gas desulfurization (FGD) waters. Analysis of FGD water samples indicated that aqueous concentrations of Hg, As, and Se remained constant or changed very slightly in a pilot-scale equalization basin during a 24-h hydraulic retention time (HRT). No change in toxicity of FGD water occurred after one HRT. FGD particles were predominantly silt size, and approximately 99% of particles suspended in FGD water settled to the bottom of a 2.5-m-deep equalization basin during the first 4 h of the 24-h HRT. Approximately 90% of the total As, and smaller percentages of Hg and Se, in FGD water and particles were removed by particle settling in the equalization basin. Results of this investigation lend support to the use of equalization basins for treating FGD waters in constructed wetland treatment systems.

Flowable Fill Using Flue Gas Desulfurization Material

Abstract Flowable fills are an effective and practical alternative to commonly used compacted earth backfills. Flowable fill is a cementious material, commonly a blend of cement, fly ash, sand, and water, that does not require compaction, may be self-leveling at time of placement, may harden quickly within a few hours, and can be excavated in the future if need be. Many flue gas desulfurization (FGD) materials have low unit weight and good shear strength characteristics and thus hold promise for flowable fill applications. This paper focuses on the potential of using two types of FGD materials (spray dryer and wet fixated FGD material) in flowable fill as a replacement for conventional fly ash. Several design mixes were considered. The design mixes consisted of varying amounts of FGD material, cement, lime, and water. The mixes were tested in the laboratory for flowability, unit weight, moisture content, unconfined compressive strength, erodibility, set-time, penetration, and long-term strength characteristics. Tests were conducted for up to 90 d of curing. Without any additives, the FGD material was observed to be as good as a regular (normal set) flowable fill in terms of placeability, unconfined compressive strength, and diggability. FGD material flowable fill with additives and admixtures compares favorably with the characteristics of conventional quick set flowable fills.

96/03292 - PFEER and arrangements for recovery and rescue — Implementation

Flue gas desulfurization (FGD) gypsum is a by-product created when sulfur is removed from flue gases in power plants. The utilization of FGD gypsum as a road sub-base for construction purposes is unsatisfactory when compared with other by-products such as fly ash and steel slag. As a result, FGD gypsum has generally been treated as a waste product and landfill. A new type of semi-rigid road sub-base is proposed, which is a mixture of FGD gypsum, water glass and slaked lime. Laboratory studies of moulded samples of this new material were investigated using different curing methods and measuring unconfined compressive strength, soundness and water stability. The experimental results showed that the road sub-base material reflects excellent mechanical properties and soundness durability. This contributes not only to improved road performance, but also represents a new and improved beneficial use of FGD gypsum.