Metals flyash

D. A. Tillman and C. Leone, "Control of Trace Metals in Flyash at the Tacoma, Washington Multifiiels Incinerator," Proceedings of the Mmerican Flame Research Committee Fall International Symposium, San Francisco, 1990. 

The Clean Air Act of 1990 has made trace metal content in fuels and wastes the final ash-related compositional characteristic of significance. Considerable attention is paid (ca 1993) to emissions of such metals as arsenic, cadmium, chromium, lead, mercury, silver, and zinc. The concentration of these metals in both grate ash and flyash is of significance as a result of federal and state requirements of particular importance is the mobility of metals. This mobility, and the consequent toxicity of the ash product, is determined by the Toxic Characteristic Leaching Procedure (tclp) test. Tables 8—10 present trace metal contents for wood wastes and agricultural wastes, municipal waste, and refuse-derived fuel, respectively. In Table 8, the specific concentration of various components in the RDF governs the expected average concentration of trace metals. 

The waste provides a source of chlorine and of metals. The latter are incorporated into flyash, which carries over to the cooler (250-400°C) post-combustion zone of the incineration system. 

The organic precursors are incorporated into, or adsorb onto the surface of the flyash in the post-combustion zone, and, following a complex sequence of reactions which are catalysed by metals (primarily copper) in the flyash, lead to the formation of PCDD/Fs along with other chlorinated trace organics. 

The amount of carbon and of metals (especially of copper) present in the flyash. 

Weng CH, Huang CP (1994) Treatment of metal industrial wastewater by flyash and cement fixation. J Environ Eng 120 1470-1488... 

When biomass is co-fired with coal (even in small percentages), the alkali metals in biomass ash can alter the properties of the resulting mixed ash. This could have a significant impact on the coal plant s operating and maintenance costs or even operability. The addition of biomass to a coal-fired power plant can also nullify ash sales contracts for coal flyash. Biomass ash components in feedstocks may also reduce the long-term efficiency and effectiveness of certain (selective catalytic reduction, SCR) systems for the selective catalytic reduction ofNOx. 

An important example related lo the atmospheric aerosol is the droplet containing dissolved sulfates that form as a result of the oxidation of SO2 in solution. The sulfates may be present a.s sulfuric acid or in a partially neutralized form as ammonium salts or metallic salts from sources such as flyash. The droplet size distribution and chemical composition are determined by a combination of thermodynamic and rate processes. In this section, we consider only equilibrium thermodynamics as it affects the vapor pressure of the drop. 

Solidification This method is a modification of the reserve pit method. When drilhng is completed, a mixture of cement, flyash (from coal-fired utility boilers), and/or lime or cement kiln dust is added to the contents of the pit. The liquid in the pit does not necessarily need to be removed. The contents of the pit solidify into a concrete-like block, which immobilizes the heavy metal components. 

The fates of vanadium and nickel w also examined during the BGS test pro am. Metal balances were conducted for the tests when cofiring petroleum coke with coal— with and without the addition of urban wood waste. On average, and with little deviation, the vanadium partitioned equally between flyash and slag only half of the vanadium ended up in the flyash. Only 25 percent of the nickel ended up in the flyash with 75 percent reporting to slag [15,29-31]. 

---