Oxygen electrostatic precipitation

The oxidant preheater, positioned in the convective section and designed to preheat the oxygen-enriched air for the MHD combustor to 922 K, is located after the finishing superheat and reheat sections. Seed is removed from the stack gas by electrostatic precipitation before the gas is emitted to the atmosphere. The recovered seed is recycled by use of the formate process. Alkali carbonates ate separated from potassium sulfate before conversion of potassium sulfate to potassium formate. Sodium carbonate and potassium carbonate are further separated to avoid buildup of sodium in the system by recycling of seed. The slag and fly-ash removed from the HRSR system is assumed to contain 15—17% of potassium as K2O, dissolved in ash and not recoverable. 

Electric steel furnaces charging, pouring, oxygen blow Fumes, smoke, particulates (dust), CO Segregating dirty scrap proper hooding, baghouses or electrostatic precipitator... 

Of the major components of flue gas, oxygen and water vapor influence the reactions of the oxides considerably, hut carbon dioxide does not. Under irradiation, NO is oxidized by reactions with O, OH, and H02 radicals. The resultant N02 is oxidized to HN03 by reaction with OH radicals. S02 is similarly oxidized to H2S04 by reactions with O and OH. The products can also be converted to aerosols and collected in electrostatic precipitators. 

This process converts crushed coal, oxygen, and steam at 820 to 1000°C and near-atmospheric pressure in a fluid-bed gasifier. After passage of the raw gas through a waste heat recovery section, flyash is removed by cyclones, wet scrubbers, and electrostatic precipitators. Further processing, depending on end use, yields a gas suitable as synthesis gas or pipeline gas. 

Environmental concerns of lime kiln operation chiefly relate to exhaust gas dust control and are usually solved by water scrubbing. The slaked lime (calcium hydroxide) produced by the scrubber can be employed as a base in the operations of a chemical complex, or sold. Electrostatic precipitation of precooled gases is also used, sometimes in series with water scrubbing. The dissociated carbon dioxide discharged is not ordinarily regarded as a pollutant. The amount discharged from this source is far less than the carbon dioxide produced by fossil fuel combustion. Lime kilns associated with Solvay ammonia-soda plants may be able to recycle a part of the dissociated carbon dioxide, particularly if the concentrations are raised by the use of oxygen-enriched combustion air. Recently, interest has been shown... 

When oxygen-rich air is blown through a copper matte a large amount of SO2 is produced. This is contaminated with dust from the ores and hence it is cleaned by scrubbers and electrostatic precipitators and then fed to the (attached) sulfuric acid plant. This plant consumes all the SO2 and produces sulfuric acid. However, due to copper converter operations, the percentage SO2 and the gas flow vary considerably. External heating sources (oil fired burners) are provided if required and similar workings are used for zinc smelters and to use the SO2 produced for sulfuric acid production. 

The application of oxy-combustion to a coal-fired steam cycle is illustrated in Fig. 10.6. Since combustion of coal in pure oxygen produces flame temperatures much higher than combustion in air, a portion of the C02-rich flue gas is typically recirculated back to the burner to limit the peak temperature in the combustion chamber. Different arrangements can be adopted Fig. 10.6 recycles a portion of the dry exhaust from the flue gas desulfurizer (FGD) back to the stream that transports the pulverized coal to the burner. A wet recycle stream, drawn just downstream of the electrostatic precipitator, provides additional inert gas to keep the furnace temperature close to that found in air fired boilers. 

Dust burdens are being reduced by the use of electrostatic precipitators. The oxygen level at the electrostatic precipitator is around 7%. Providing the whole process is under effective control, NOx levels should be at an acceptable level. 

When the Toyama-Shinko boUer bums 1% sulfur fuel oil, the flue gas contains approximately 450 ppm SO2 and 2.5 to 4% oxygen. The gas passes through an electrostatic precipitator, which reduces its particulate concentration to about 0.012 gr/scf, and is then fed to Ae FGD unit at a rate of 467,000 schn. It flows first through a venturi prescrubber, which cools it from 284° to 140°F, then through a packed absorber where it contacts dilute sulfuric acid, and finally through a mist eliminator before being reheated and released to the stack. 

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