Stripping operation wastewater

The following information is requested as part of a wastewater treatment stripping operation for ethyl alcohol (EtOH). Generate a Txy diagram given the vapor-liquid equilibrium (VLE) data below. What is the vapor mole fraction of the ethanol if the liquid mixture contains 3.6mol % ethanol ... 

Chevron s WWT (wastewater treatment) process treats refinery sour water for reuse, producing ammonia and hydrogen sulfide [7783-06-04] as by-products (100). Degassed sour water is fed to the first of two strippers. Here hydrogen sulfide is stripped overhead while water and ammonia flow out the column bottoms. The bottoms from the first stripper is fed to the second stripper which produces ammonia as the overhead product. The gaseous ammonia is next treated for hydrogen sulfide and water removal, compressed, and further purified. Ammonia recovery options include anhydrous Hquid ammonia, aqueous Hquid ammonia, and ammonia vapor for incineration. There are more than 20 reported units in operation, the aimual production of ammonia from this process is about 200,000 t. 

EPA has also developed pretreatment standards for industrial faciHties that discharge directiy to pubHcly owned treatment works (POTWs). The three types of pollutants of principal concern are pollutants that interfere with the operation of the POTW, pollutants that contaminate the sludges produced in the POTW, and pollutants that pass through the POTW or that are otherwise incompatible. One particular concern is volatile contaminants that can be stripped into the air during conventional wastewater treatment and become air pollution problems. These pretreatment standards are included in the effluent guidelines for the different industries. 

Air stripping is used to remove 90% of the toluene (molecular weight = 92) dissolved in a 10 kg/s (159 gpm) wastewater stream. The inlet composition of toluene in the wastewater is 500 ppm. Air (essentially free of toluene) is compressed to 202.6 kPa (2 atm) and bubbled through a stripper which contains sieve trays. In order to avoid fire hazards, the concentration of toluene in the air leaving the stripper is taken as 50% of the lower flammability limit (LFL) of toluene in air. The toluene-laden air exiting the stripper is fed to a condenser which recovers almost all the toluene. A schematic representation of the process is shown in Fig. 2.11. Calculate the annual operating cost and the fixed capital investment for the system. The following physical and economic data are available ... 

USEPA issued the NESHAP for benzene waste operations March 7, 1990, under the Clean Air Act. The compliance date was May 1992. It affects not only equipment leaks but also emissions of benzene in wastewater streams. Eacilities with greater than 10 tonnes/year benzene in wastewater streams are affected. They must identify wastewater streams containing greater than 10 mg/L benzene and divert them to units that will reduce benzene to acceptable levels, that is, below 10 mg/L or by 98%. This rule affected most major refineries and olefins plants. Mobil Corp. spent 10 million on a benzene recovery project at its Chalmette, LA, refinery. The refinery uses vacuum steam stripping to decrease benzene emissions by about 10 tonnes/year. One Gulf Coast petrochemical plant has also spent 10 million on a wastewater stripping facility, which reduced benzene levels from several thousand mg/L to less than 5 mg/L [70]. 

Although neutralized wastewater falls a clear IS ft before entering the settlement basin, and settled effluent passed through a straw bale filter, operating data reveal no evidence of any effect on pH of carbon dioxide stripping in the fall, or of straw bale filtration on metals concentrations.14... 

The recovery area uses a patented organic solvent to remove the maleic anhydride from the reactor effluent gas. Aconventional absorption (2)/stripping (3) scheme operates on a continuous basis. Crude maleic anhydride is distilled to separate light (4) and heavy (5) impurities. A slipstream of recycle solvent is treated to eliminate any heavy byproducts that may be formed. The continuous nonaqueous product recovery system results in superior product quality and large savings in steam consumption. It also reduces investment, product degradation loss (and byproduct formation) and wastewater. 

Part II covers the unit operations of flow measurements and flow and quality equalizations pumping screening, sedimentation, and flotation mixing and flocculation filtration aeration and stripping and membrane processes and carbon adsorption. These unit operations are an integral part in the physical treatment of water and wastewater. 

Example 9.13 A wastewater containing 25 mg/L of NH3-N is to be stripped. The temperature of operation is 15°C and the flow is 0.013 m /s. Determine the amount of air needed assuming a multiplying factor of 1.5 for the minimum theoretical G. Calculate the cross-sectional area of the tower. Assume a superficial velocity of 0.30 m/s. 

Problems associated with calcium carbonate scale formation. Because ammonia stripping is operated at a high pH (11 or above), calcium deposits on the packing materials can be expected. If these deposits are not periodically dislodged and broken up by the hydraulic force, excessive accumulation can restrict the flow of both the wastewater and the air, thereby reducing the effectiveness of the system. 

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