Flue additives

Sintering. The charge for sintering is prepared by blending selected concentrates, smelter by-products, returned sinter, flue dust, and when required, additional fuel such as coke bree2e. The blend is then peUeti2ed in preparation for sintering. 

Because of the wide variation in composition and properties of brown coal (see Table 3), efficient combustion of these fuels caimot be accomphshed by a single system. The moisture content limits combustion efficiency because some chemical energy is required to convert Hquid water to steam in the flue gases. The steam then increases the dew point of the gases, requiring higher temperatures to avoid condensation in the stack. For fuels up to 25% moisture content, 80% efficiency can be achieved. As the moisture content increases to 60%, the efficiency decreases to 70% and efficiency continues to decline about another 1% for each additional 1% moisture to 70%. 

Static mixers are used ia the chemical iadustries for plastics and synthetic fibers, eg, continuous polymeri2ation, homogeni2ation of melts, and blending of additives ia extmders food manufacture, eg, oils, juices, beverages, milk, sauces, emulsifications, and heat transfer cosmetics, eg, shampoos, hquid soaps, cleaning Hquids, and creams petrochemicals, eg, fuels and greases environmental control, eg, effluent aeration, flue gas/air mixing, and pH control and paints, etc. 

Minor and potential new uses include flue-gas desulfurization (44,45), silver-cleaning formulations (46), thermal-energy storage (47), cyanide antidote (48), cement additive (49), aluminum-etching solutions (50), removal of nitrogen dioxide from flue gas (51), concrete-set accelerator (52), stabilizer for acrylamide polymers (53), extreme pressure additives for lubricants (54), multiple-use heating pads (55), in soap and shampoo compositions (56), and as a flame retardant in polycarbonate compositions (57). Moreover, precious metals can be recovered from difficult ores using thiosulfates (58). Use of thiosulfates avoids the environmentally hazardous cyanides. 

Currently, the most frequently used technology for SO reduction in the flue gas is a SO adsorbing additive. With such an additive, the following steps occur.Oxidation of SO to SO in the regenerator. 

Because O2 is necessary to convert SO2 to SO, decreasing O2 in the regenerator has been found to reduce the effectiveness of the SO removal additive. The SO additives used in regenerators operating in a partial CO combustion mode, where excess O2 is frequentiy limited to <0.2 vol % in the flue gas, are less successful in reducing SO. In such cases, SO removal is typically 20—30% less than for a full CO combustion (1 + % excess O2) case (45). 

The additive approach to reducing SO emissions can be either detrimental or beneficial toward NO reduction. Early alumina-based SO removal additives actually produced substantial increases in NO content in the flue gas (48). The more recent spinel-based SO removal additives have been reported to reduce NO emission by 30% in one commercial trial (49). 

The Dravo hydrate addition at low temperature process involves a two-step injection of water and dry sorbent in a rectangular 19.8-m duct having a cross section of 2 m. In one step water is injected through atomization nozzles to cool the flue gas from 150°C to approximately a 15°C approach to adiabatic saturation. The other step involves the dry injection of hydrated lime, either downstream or upstream of the humidifica tion nozzles. Typical SO2 removals were 50—60% at a Ca S ratio of 2. 

Other problems that can be associated with the high dust plant can include alkaH deterioration from sodium or potassium in the stack gas deposition on the bed, calcium deposition, when calcium in the flue gas reacts with sulfur trioxide, or formation and deposition of ammonium bisulfate. In addition, plugging of the air preheater as weU as contamination of flyash and EGD wastewater discharges by ammonia are avoided if the SCR system is located after the FGD (23). 

The specific electrical resistance of concrete can be measured by the method described in Section 3.5. Its value depends on the water/cement value, the type of cement (blast furnace, portland cement), the cement content, additives (flue ash), additional materials (polymers), the moisture content, salt content (chloride), the temperature and the age of the concrete. Comparisons are only meaningful for the... 

As a first step in the driver analysis, the eapital required to make eaeh alternative operational is estimated. An orifiee ehamber is required to reduee the flue gas pressure for the steam turbine and motor alternatives. In this partieular ease, it is assumed that a third-stage separator is required for the power reeovery alternatives only and that an eleetrostatie preeipitator is used in all eases. Construetion and engineering are estimated as pereentages of total direet material and total material and eonstruetion, respeetively. An allowanee of 15% is made for eontingeney. Beeause the separator often ineludes a royalty fee, this item is added to the power reeovery alternates. As shown in Table 4-7, the motor alternative will require the least eapital. The power reeovery alternatives require additional eapital amounting to 4.63 and 4.75 per million respeetively. 

The burner should be designed for handling preheated combustion air. Preheated combustion air is obtained by diverting part of the exhaust from the gas turbine. The air from the turbine is clean, hot air. To recover additional heat energy from the exhaust flue gases, a steam coil is placed... 

Selective catalytic reduction (SCR) is cmrently the most developed and widely applied FGT technology. In the SCR process, ammonia is used as a reducing agent to convert NO, to nitrogen in the presence of a catalyst in a converter upstream of the air heater. The catalyst is usually a mixture of titanium dioxide, vanadium pentoxide, and hmgsten trioxide. SCR can remove 60-90% of NO, from flue gases. Unfortunately, the process is very expensive (US 40- 80/kilowatt), and the associated ammonia injection results in an ammonia slip stream in the exhaust. In addition, there are safety and environmental concerns associated with anhydrous ammonia storage. 

Air emissions from coking operations include the process heater flue gas emissions, fugitive emissions, and emissions that may arise from the removal of the coke from the coke drum. The injected steam is condensed and the remaining vapors are typically flared. Wastewater is generated from the coke removal and cooling operations and from the steam injection. In addition, the removal of coke from the drum can release particulate emissions and any remaining hydrocarbons to the atmosphere. 

Natural gas containing 98% methane and 2% nitrogen by volume is burned in a furnace with 15% excess air. The fuel consumption is 20 cubic meters per second, measured at 290°K and 101.3 kPa (or 14.7 psia). The problem is to determine how much air is required under these conditions. In addition, we want to determine the baseline environmental performance of the furnace by calculating the quantity and composition of the flue gas. 

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