# Feasibility Study of Using Carbide Slag as In-Bed Desulfurizer in Circulating Fluidized Bed Boiler  
[PERSON]  
[PERSON]  
and sorbent. A lot of technical methods for emission reduction have been studied and used with CFB boilers to achieve better results. Some CFB boilers adopt 900 \({}^{\circ}\)C as the bed temperature to improve combustion efficiency but some researchers, including [PERSON] et al. [6], found that desulfurization efficiency reached the best value in the range of 800 to 850 \({}^{\circ}\)C. The reaction rate decreased when the temperature increased, while the sulfation rate rose rapidly, which blocked pores of calcium oxides. As a result, the utilization of the sorbent was inhibited. This situation occurred in most commercial CFB boilers [7]. In these boilers, when the furnace temperature rose above 900 \({}^{\circ}\)C, the consumption of sorbent increased. Some countries have very strict environmental standards, such as China which has ultra-low emission standard [8]. To meet these standards, many efforts have to be made to improve the desulfurization efficiency with relatively low cost. Thus, it is important to find an effective but low-cost sorbent as an alternative to limestone. A few researchers [9; 10; 11; 12; 13] have carried out research to find a substitute to limestone as the desulfurizer from industrial waste containing Ca. [PERSON] et al. [9] added red mud to a loose coal and found that the presence of red mud could significantly fix the sulfur with fixation rates over 79%. [PERSON] et al. [10] compared the sulfation behavior of limestone and white mud from paper manufacture as SO\({}_{2}\) sorbent at fluidized bed combustion temperatures on a thermogravimetric analyzer (TGA). They found the white mud showed better sulfation capacity than the limestone, as the surface area of the calcined white mud was approximately twice as large as the calcined limestone at the same calcination temperature. [PERSON] et al. [11] evaluated white clay, carbide slag, and steel slag as SO\({}_{2}\) sorbent in a 6 t\(\cdot\)h\({}^{-1}\) industrial grate furnace. They found that a nearly 50% reduction in SO\({}_{2}\) emission was achieved. Moreover, [PERSON] et al. [12] investigated the desulfurization performance of several alkaline waste slags, including carbide slag, alkaline slag, waste marble, and limestone in an absorber bottle. They found that both carbide slag and alkaline slag exhibited much higher desulfurization capacity compared to waste marble and limestone. [PERSON] et al. [13] compared the SO\({}_{2}\) capture capacity of three industrial wastes, including calcium carbide residue, brine sludge, and white lime mud at 1000-1600 \({}^{\circ}\)C in a fixed bed. They found that white lime mud gave the highest desulfurization efficiency of 80.4% at 1000 \({}^{\circ}\)C in coal combustion. All of these results confirmed that industrial wastes containing Ca have the potential to be reused as alternative desulfurizers. As mentioned above, carbide slag is a promising candidate for the alternative in-bed desulfurizer. Carbide slag is typically a by-product during the hydrolysis process of calcium carbide (CaC\({}_{2}\)) in the production of acetylene. The main component of carbide slag is Ca(OH)\({}_{2}\)[14]. More than 40 million tons of carbide slag is produced per year all over the world [15]. However, carbide slag is difficult to reuse. It is ordinarily landfilled, resulting in land occupation, environmental pollution, and waste of a calcium resource. Carbide slag is likely to contaminate soil and groundwater because it is strong alkaline (pH \(>\) 12). [PERSON] et al. [16] studied SO\({}_{2}\) adsorption by carbide slag and limestone in the fixed bed and found that carbide slag possessed higher SO\({}_{2}\) adsorption capacity than limestone at 700 \({}^{\circ}\)C. Similar studies were also conducted by [PERSON] et al. [11] and [PERSON] et al. [12], both of which confirmed the potential in desulfurization.