Limestone emissions

Ammonia injection near the bottom of bubbling bed combustors can lead to increases in emissions (Minchener and Kelsall, 1990 Hoke et al., 1980). The effect is attributed to the high oxygen concentration due to the close proximity of the primary air distribution which can lead to oxidation of ammonia. Studies have revealed that the optimum ammonia injection location is either in the upper furnace area or in the cyclone (Hoke et al., 1980 Minchener and Kelsall, 1990 Hiltunen and Tang, 1988 Shimizu et al., 1990). Injection locations anywhere else either increases emissions or creates unacceptable ammonia slip into the atmosphere. Experimental studies indicated that under high concentrations of char and limestone, emissions can increase with ammonia injection (Shimizu et al., 1990). The effect is attributed to the catalytic effect of char and limestone on ammonia oxidation. Using a kinetic model for formation, Johnsson (1989) has shown the importance of the ammonia oxidation in the presence of limestone and char catalyst. 

There are, however, technological means available to burn incompletely desulfurized fuels at the same time minimizing SO2 emissions. In the auto-desulfurizing AUDE boiler developed by IFF, the effluent is treated in place by an absorbent based on lime and limestone calcium sulfate is obtained. This system enables a gas desulfurization of 80% it requires nevertheless a relatively large amount of solid material, on the order of 200 kg per ton of fuel. 

Formation of emissions from fluidised-bed combustion is considerably different from that associated with grate-fired systems. Flyash generation is a design parameter, and typically >90% of all soHds are removed from the system as flyash. SO2 and HCl are controlled by reactions with calcium in the bed, where the lime-stone fed to the bed first calcines to CaO and CO2, and then the lime reacts with sulfur dioxide and oxygen, or with hydrogen chloride, to form calcium sulfate and calcium chloride, respectively. SO2 and HCl capture rates of 70—90% are readily achieved with fluidi2ed beds. The limestone in the bed plus the very low combustion temperatures inhibit conversion of fuel N to NO. ... 

A fluidized bed is an excellent medium for contacting gases with sohds, and this can be exploited in a combustor because sulfur dioxide emissions can be reduced by adding limestone, CaCO, or dolomite, CaCO MgCO, to the bed. 

Emissions control systems play an important role at most coal-fired power plants. For example, PC-fired plants sited in the United States require some type of sulfur dioxide control system to meet the regulations set forth in the Clean Air Act Amendments of 1990, unless the boiler bums low sulfur coal or benefits from offsets from other highly controlled boilers within a given utiUty system. Flue-gas desulfurization (FGD) is most commonly accomphshed by the appHcation of either dry- or wet-limestone systems. Wet FGD systems, also referred to as wet scmbbers, are the most effective solution for large faciUties. Modem scmbbers can typically produce a saleable waUboard-quaUty gypsum as a by-product of the SO2 control process (see SULFURREMOVAL AND RECOVERY). 

Sulfur dioxide emissions may affect building stone and ferrous and nonferrous metals. Sulfurous acid, formed from the reaction of sulfur dioxide with moisture, accelerates the corrosion of iron, steel, and zinc. Sulfur oxides react with copper to produce the green patina of copper sulfate on the surface of the copper. Acids in the form of gases, aerosols, or precipitation may chemically erode building materials such as marble, limestone, and dolomite. Of particular concern is the chemical erosion of historical monuments and works of art. Sulfurous and sulfuric acids formed from sulfur dioxide and sulfur trioxide when they react with moisture may also damage paper and leather. 

Bauxite and limestone handling and storage dust emissions are controlled by baghouses. 

Calcium, D. of - continued in limestone or dolomite, (fl) 813 in presence of barium, (ti) 333 with CDTA, (ti) 333 with lead by EDTA, (ti) 333 with magnesium by EDTA, 328 by EGTA, (ti) 331 by flame emission, (aa) 804 Calcium oxalate, thermal analysis 498 Calcon 318 Calculators 133 Calibration of apparatus, 87 of burettes, 88 of graduated flasks, 88 of pipettes, 88 of weights, 74... 

If a limestone or dolomite sorbant is added to the hot sand bed, the calcium oxide (CaO) produced reacts and combines with S02, thus reducing the emission of the pollutant. 

The energy use and emissions are similar as in the process production of cushion vinyl floor covering , but discarded cushion vinyl floor covering (waste) is the economic inflow and the different materials (goods), like PVC, limestone, glass fibre, etc., are the economic outflows. 

Scale formation in the scrubber can lead to sodium carbonate as an additional dry sorbent in the scrubber. Alternatively, limestone is also introduced into combustion chambers to treat sulfur dioxide emissions. Decomposition of CaC03 into CaO and CO2 occurs in the combustion chamber, and the resulting CaO combines with S02 to produce calcium sulfite. Notice that this process produced another potentially environmentally harmful pollutant (CO2) as it gets rid of a definite environmentally harmful pollutant (SO2). 

In the end, both approaches require the calcination of limestone to lime. The energy penalty in this process is about 4.5-5 GJ/ton of C02, which amounts to a 30-40% energy penalty of a transportation sector that uses air extraction for managing its own C02 emissions. This is comparable to the energy penalty incurred in the conversion of fossil fuels into hydrogen as a transportation fuel (Zeman and Lackner, 2004). 

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