Stripping systems

Natural gas contains both organic and inorganic sulfur compounds that must be removed to protect both the reforming and downstream methanol synthesis catalysts. Hydrodesulfurization across a cobalt or nickel molybdenum—zinc oxide fixed-bed sequence is the basis for an effective purification system. For high levels of sulfur, bulk removal in a Hquid absorption—stripping system followed by fixed-bed residual clean-up is more practical (see Sulfur REMOVAL AND RECOVERY). Chlorides and mercury may also be found in natural gas, particularly from offshore reservoirs. These poisons can be removed by activated alumina or carbon beds. 

Fixed-bed desulfuri2ation is impractical and uneconomical if the natural gas contains large amounts of sulfur. In this case, bulk sulfur removal and recovery (qv) in an acid gas absorption—stripping system, followed by fixed-bed residual cleanup is usually employed. 

Stripping Air stripping is applied for the removal of volatile substances from water. Henry s law is the key relationship for use in design of stripping systems. The minimum gas-to-liquid ratio required for stripping is given by ... 

Fixed cost of stripping system associated with S4, = 270,000 (Rowrate of wastewater, kg/s/- ... 

There are many possible combinations of supply and exhaust air. For example, a line jet could be used as a shield in an opening, as a stripping system on surfaces, for blowing contaminants into an exhaust, etc. An enclosure could be designed with a line jet in the opening, with a wall jet inside to increase efficiency, or with a low-momentum jet inside or outside the opening to replace the room air supply. In this section, only some basic combinations are described. 

Whether for a distillation, absorption, or stripping system the material balance should be established around the top, bottom, and feed sections of the column. Then, using these liquid and vapor rates at actual flowing conditions, determine the flooding and maximum operating points or conditions. Then, using Figures 9-21B, -21E, or -21F, establish pressure drop, or assume a pressure drop and back-calculate a vapor flow rate, and from this a column diam-... 

Of the four enhanced volatilization methods described above, documentation exists to support the contention that the low-temperature thermal stripping system has the greatest ability to successfully remove contaminants that are similar to gasoline constituents (i.e., compounds with high vapor pressures) from soil. The limitations of some enhanced volatization techniques can be attributed to the following ... 

Normally, treatment of coproduced groundwater during hydrocarbon recovery operations will include, as a minimum, oil-water separation and the removal of dissolved volatile hydrocarbon fractions (i.e., benzene, toluene, and total xylenes). In addition, removal of inorganic compounds and heavy metals (i.e., iron) is often required. Dissolved iron, a common dissolved constituent in groundwater, for example, may require treatment prior to downstream treatment processes to prevent fouling problems in air-stripping systems. Heavy metals removal is normally accomplished by chemical precipitation. 

Innovation drivers Alternative paint strippers have been developed as a consequence of the chlorine debate . However, neither the detailed requirements related to occupational health and safety (TRGS 612 and 212) nor the lower efficiency (cf (3)) clearly supported the penetration of the market with the alternative paint stripping systems. One barrier may be that the users have to change their work and purchasing procedures to apply the alternatives successfully. By end of the nineties the construction employers liability insurance started, based on the public media, an information campaign about the risks of DCM-containing paint strippers. 

Another coke formed in a FCC unit is occluded or residual coke. In a commercial unit this coke corresponds to coke formed on catalyst porosity and its content depends on textural properties of the catalyst (pore volume and pore size distribution) and the stripping system capacity in the reaction section. Finally on the FCC catalyst rests some high-molecular weight of nonvaporized hydrocarbons. These molecules do not vaporize or react at the reactor conditions and accumulate in the catalyst pores like a soft carbonaceous residue with high hydrogen content. 

The Aeromix BREEiZE is an air stripping system for removal of ex situ volatile organic compounds (VOCs) from aqueous waste streams. The BREEZE is commercially available and has been used in numerous remediations. 

The Aeromix BREEZE air stripping system is a transportable system designed with an aeration tank coupled with a blower. The aeration tank incorporates CYCLONE nonfouling, all stainless steel air diffusers that provide the air-to-water interface needed for stripping and contaminant removal. 

Cost of an air stripping system is site specific and contaminant specific. In 1991, the cost of air stripping contaminants with a Henry s law coefficient from 0.1 to 10 was estimated to range from 0.07 per 1000 gal of water treated to 0.70 per 1000 gal of water treated (packed-tower system). As the Henry s law coefficient was decreased to 0.005, costs rapidly rose to 7.00 per 1000 gal of water treated (D164241, p. 7). 

Factors that impact the cost of an air stripping system include system design, emission controls, effluent treatment (if required), and operations and maintenance. The addition of an air treatment system roughly doubles the cost of an air stripping system (D164241, p. 7). 

The cost of GAC-FBR technology was compared with the cost of air stripping in 1995. Capital and operating costs on an annual basis were projected to be 72,200 for the GAC-FBR system, a cost less than 30% of the 252,000 projected for the air stripping system (D130392, p. 5). 

The vendor claims that the thermal stripping system treats soil contaminated with gasoline, diesel fuel, or kerosene, at prices equal to or lower than those using off-site incineration or landfarming. They also state that the system has the potential to treat chlorinated and fiuorinated hydrocarbons. 

The Thermatrix, Inc., PADRE process is a commercial, off-gas treatment technology that purifies airstreams contaminated with volatile organic compounds (VOCs). The PADRE vapor treatment process traps VOCs using filter beds that contain a proprietary resin. This regenerative adsorption method involves an on-line treatment bed for infiuent air, while another bed undergoes a desorption cycle. PADRE often works in conjunction with soil vapor extraction or air stripping systems. The PADRE process can be applied at site remediation projects, industrial wastewater facilities, and industrial air processing sites. 

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