Migration Behaviors of As, Se and Pb in Ultra-Low-Emission Coal-Fired Units and Effect of Co-Firing Sewage Sludge in CFB Boilers

Abstract

The migration behaviors of As, Se and Pb in ultra-low-emission coal-fired units were investigated and the effect of co-firing of sewage sludge and coal was explored in circulating fluidized-bed (CFB) boiler units. Samples of feed fuel including coal and sewage sludge, fly ash, bottom slag and desulfurization slurry were collected from five CFB units with a capacity between 150 MW and 350 MW and two pulverized coal boiler (PC) units with a capacity of 350 MW and 600 MW. The majority of As, Se and Pb in coal is released during coal combustion and enriched in fly ash. As, Se and Pb in fly ash and bottom slag are associated with inorganic matter, of which As, Se and Pb associated with silicates and aluminosilicates account for more than 60%. In the wet flue gas desulfurization (WFGD) unit, more than half of the As, Se and Pb migrates to the solid fraction and the concentrations of As, Se and Pb in fine solid particles are much higher than those in coarse solid particles and the liquid fraction. The proportions of exchangeable As, Se and Pb or associated with organic matter in gypsum are higher than those of fly ash and bottom slag. According to the two studied CFB units with blending ratios of sewage sludge below 10%, co-firing with sewage sludge has little effect on the migration and transformation characteristics of As, Se and Pb. Under a long-term acidic leaching environment, Pb in combustion by-products is in the range of low risk, while As and Se are in the range of medium risk.

Techno-Economic Analysis of Fluidized Bed Combustion of a Mixed Fuel from Sewage and Paper Mill Sludge

“…The data in Table 6 suggest that magnesium, potassium, calcium, chromium, copper, zinc, arsenic, and lead remained mostly in the ash after combustion, while all cadmium from all fuels used was transferred into the flue gas together with a substantial part of chlorine and mercury. These results are in accord with previously published works [31][32][33].…”

“…The migration behaviours of As, Se, and Pb during the co-combustion of sewage sludge with coal was investigated in circulating fluidized-bed (CFB) boiler units with a capacity between 150-350 MW and two pulverized coal boiler (PC) units with a capacity of 350 MW and 600 MW. In the wet flue gas desulphurisation unit, the proportions of As, Se, and Pb in gypsum are higher than those of fly ash and bottom slag [32]. Karasek [33] investigated the behaviour of heavy metals and their compounds during the sewage sludge incineration process.…”

Research on Carbon Emissions Prediction Model of Thermal Power Plant Based on SSA-LSTM Algorithm with Boiler Feed Water Influencing Factors

“…Boiler feed water quantity (t) X 4 Incoming raw water quantity (t) X 5 Demineralized water quantity (t) X 6 Elemental carbon content (tC) X 7 Coal consumption (t) X 8 Received base ash (%) X 9 Average low calorific value (kJ/kg) X 10 Fly ash carbon content (tC/t)…”

“…Carbon emissions from coal burning in grinding plants Y 9 Carbon emissions from fuel oil of the first power plant Y 10 Carbon emissions from fuel oil of the second power plant…”

“…The use of circulating fluidized bed (CFB) boiler units is an important way to solve the problem of using a large quantity of low-quality coal in China, and also an important way to achieve clean coal combustion [5,6]. CFB boilers can not only burn low-quality coal with low calorific value, but also achieve low-cost emissions reduction of NOx and SO 2 through low-temperature combustion in furnace and limestone calcination [7][8][9]. In view of the above advantages, CFB boilers have been widely used in China, especially in low-quality coal production areas such as Shanxi, Shaanxi, and Inner Mongolia [10].…”