Mist-free operation

A (Column) Internal for the Mist-Free Operation of Wet (Cross Flow) Cooling Towers... 

Downstream from the 3rd bed, the gas is cooled and passed to an intermediate absorption tower, in which the S03 formed is absorbed in recirculating sulphuric acid. The cold and practically S03-free process gas is reheated to 380-440°C and returned to the converter, where the remaining SO2 is converted to S03 in a 4th catalyst bed. The rest of the S03 is subsequently recovered in a final absorption tower before the process gas, containing a small fraction of unconverted S02, is emitted through the stack. The combustion air is dried with the 98 wt% product acid in order to avoid corrosion and acid mist problems in the plant. The sulphuric acid process normally operates close to atmospheric pressure with the combustion air blower dimensioned just for compensation of the pressure drop through the plant. 

PRODUCED WELLHEAD FLUIDS are complex mixtures of hydrogen and carbon compounds with differing densities, vapor pressures and other characteristics. The wcllstrcam undergoes continuous pressure and temperature reduction as it leaves the reservoir. Gases evolve from liquids, water vapor condenses and part of the well stream changes from a liquid to bubbles, mist and free gas. Gas carries liquid bubbles and the liquid carries gas bubbles. Physical separation of these phases is one of the basic operations in production, processing and treatment of oil and gas. 

Steam used in the operation must be free of solids since the entrainment of solids in the mist from boilers is not an infrequent cause of physically poisoning the reforming catalyst at least in the upper (upstream) part of the reformer tubes. 

Mercurous chloride or calomel is insoluble and precipitates from solution. It can be separated in a thickener and removed from the system. Part of the calomel is treated with chlorine to regenerate the mercuric chloride scrubbing solution. The system is capable of achieving less than 0.5 ppm mercury in product acid or lower if reduced gas temperatures are used. It is important for efficient operation that the gas coming forward from the electrostatic precipitators is free from suspended mist and is classed as optically clear , otherwise contamination of the mercury scrabbing circuit will quickly destroy mercury removal efficiency. 

---