FGD gypsum

Feed slurry is introduced into the basket through either single or multiple feed pipes, or by other means such as rotating feed cone to help distribute the solids on the basket wall. In most cases, feed slurry is introduced at an intermediate speed, although in some applications (FGD gypsum, for one), feeding is done at full speed. There are several methods available to control the feed and cake level such as mechanical, paddle-type feelers, capacitance probes, ultrasonic sensors, feed totalizer, or load cells. 

Moist particulate solid wastes, such as predried FGD gypsum filter cake, can be extruded (Fig. 8.20) in, for example, flat die pellet presses (4 in Fig. 8.20) yielding cylindrical agglomerates, which are dried and screened prior to load-out. 

Fig. 8.20 Pelleting of wet FGD gypsum by medium-pressure agglomeration (flat die pelleting, courtesy Amandus Kahl, Reinbek, Germany)...

Fig. 8.21 Flow diagram of a FGD gypsum roller press briquetting plant Thermal drying of the feed is not shown Fig. 8.22 Roller press for the briquetting of (synthetic, FGD) gypsum in a flue gas desulfurization plant inset, synthetic gypsum briquettes (courtesy Koppem, Hattingen/ Ruhr, Germany)...

B. Guan, et al., Alpha-Calcium Sulfate Hemihydrate Preparation from FGD Gypsum in Recycling Mixed Salt Solutions, Chemical Engineering Journal, 174 (2011), 296-303. 

As described in section 4, the amount of mercuiy in FGD products may increase in the future if these units are optimized for co-capture. Therefore, there is the potential for creating new pathways of mercuiy release into the environment when the resulting by-products are utilized or placed in a landfill [73-74]. To know the stability of the mercury captured or if the mercury leach from CUBs and enter the groundwater is necessary to know what species of mercury are present in the CUBs. The presence of mercuiy in wet FGD gypsum may threaten... 

Figure 3. Thermal decomposition profile of FGD-gypsum sample from a Dutch co-combustion power station.

In order to improve our understanding of the speciation of mercuiy in FGD gypsum, the authors have used thermodynamic equilibrium models in order to predict the composition of the chemical species in gas phase using the HSC-Chemistry 5.0 software. The theoretical study was carried out in the same conditions that the experimental study, at atmospheric pressure and temperatures ranging between 25 and 800 C. HSC-Chemistiy program uses data base with enthalpy, entropy and calorific capacity values for more than 15000 species. This software allows modify the quantity of different species implicated in the reaction and the program determines tlie products formed, theoretically, in the equilibrium. 

Effects of Flue Gas Desulfurization (FGD) Gypsum on the Performances OF Cement-Based Materials... 

Flue gas desulphurization (FGD) gypsum is a waste generated at coal burning power stations where FGD clean coal combustion and scrubbing processes are installed to remove SO2 from the flue gases. In this chapter, the possibility of FGD gypsum as an admixture in cement-based materials, such as Portland cement, concrete, and geopolymer was explored. 

Effects of themially treated FGD gypsum on the geopolymer were also explored. The geopolymer made from 90% of the fly ash and 10% of FGD gypsum thermally ti eated at 800 for 1 h obtained the better compressive strength of 37.0 MPa. The micro structural characteristics of the geopolymer were evaluated using FTIR (Fourier... 

Utilization of FGD gypsum as an admixture in cement, concrete, and geopolymer is feasible. Using the industrial waste of FGD gypsum we can produce composite admixture for Portland cement and concrete, or prepare geopolymer, which can save natural resources greatly. 

In this work, the admixture of FGD gypsum in cement and concrete was G-I while G-II was used as an admixture in geopolymer. 

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