Gaseous waste processing

There are several gaseous wastes emitted from the process (see Dunn and El-Halwagi, 1993, and Homewoik Problem 8.5). In this exanqile, we focus on the gaseous waste leaving the multiple effect evaporators, R, whose primary pollutant is H2S. Stream data for this waste stream are given in Ihble 8.1. A rich-( ase minimum allowable composition difference, of 1.5 x 10 ° kmol/m is used. 

Two major sources of H2S emissions from the process are the acid gas stream evolving from hydrogen manufacture, Ri, and the gaseous waste emitted from the separation... 

It is desired to synthesize a REAMEN for treating the gaseous wastes (Ri and Ra) of a viscose rayon plant. Three MSAs are available to select from. These MSAs are caustic soda, S], (a process stream already existing in the plant with mi = 5.0 kmol/m ), diethanolamine, Sa, (with m2 = 2.0 kmol/m ) and activated carbon, S3. The unit costs for S2 and S3 including stream makeup and subsequent regeneration are 64.9 /m and 169.4 /ro, respectively. Stream data ate given in Table 8.7. 

Three major sources in the kraft process are responsible for the majority of the H2S emissions. These involve the gaseous waste streams leaving the recovery furnace, the evaporator and the air stripper, respectively denoted by R), R2 and R3. Stream data for the gaseous wastes are summarized in Table 8.8. Several candidate MSAs are screened. These include three process MSAs and three external MSAs. The process MSAs are the white, the green and the black liquors (referred to as Si, S2 and S3, respectively). The external MSAs include diethanolamine (DBA), S4. activated carbon, Sj, and 30 wt% hot potassium carbonate solution, S6. Stream data for the MSAs is summarized in Table 8.9. Syndiesize a MOC REAMEN that can accomplish the desulfurization task for the three waste streams. 

One of the key challenges for this process is dealing with the wide range of contaminants in the waste HBr stream. Both inorganic and organic contaminants may be present. These contaminants are typically reactants and products of the upstream bromination process which generated the waste HBr. In addition, they may include corrosion products of upstream equipment or ionic materials present in the water used to scrub the gaseous bromination process effluent. The main concerns about contaminants in the feed streams are their effect on catalyst activity and stability and their effect on bromine product quality. 

A chemical waste is any solid, liquid, or gaseous waste material that if improperly managed or disposed of, may pose substantial hazards to human health and the environment (Table 1.2). At any stage of the management process, a chemical waste may be designated by law as a hazardous waste (Chapter 12). Improper disposal of such waste streams in the past has created a need for very expensive cleanup operations (Tedder and Pohland, 1993). Correct handling of such... 

The treatment and safe disposal of waste is equally important whether it be waste generated by the pulp and paper industry, by the leather industry or gaseous waste. Recently, in addition to other membrane-based processes, demand has grown in the wastewater treatment industry for a process that uses both a biological stage and a membrane module, known as the membrane bioreactor (MBR) process. The bioreactor and membrane module each have a specific function (1) the biological degradation... 

Membrane technology may become essential if zero-discharge mills become a requirement or legislation on water use becomes very restrictive. The type of membrane fractionation required varies according to the use that is to be made of the treated water. This issue is addressed in Chapter 35, which describes the apphcation of membrane processes in the pulp and paper industry for treatment of the effluent generated. Chapter 36 focuses on the apphcation of membrane bioreactors in wastewater treatment. Chapter 37 describes the apphcations of hollow fiber contactors in membrane-assisted solvent extraction for the recovery of metallic pollutants. The apphcations of membrane contactors in the treatment of gaseous waste streams are presented in Chapter 38. Chapter 39 deals with an important development in the strip dispersion technique for actinide recovery/metal separation. Chapter 40 focuses on electrically enhanced membrane separation and catalysis. Chapter 41 contains important case studies on the treatment of effluent in the leather industry. The case studies cover the work carried out at pilot plant level with membrane bioreactors and reverse osmosis. Development in nanofiltration and a case study on the recovery of impurity-free sodium thiocyanate in the acrylic industry are described in Chapter 42. 

By definition, the material balance includes materials entering and leaving a process. Inputs to a process or a unit operation may include raw materials, chemicals, water, air, and energy. Outputs include primary product, byproducts, rejects, wastewater, gaseous wastes, liquid, and solid wastes that need to be stored sent off-site for disposal and reusable or recyclable wastes (Figure 3). In its simplest form, a material balance is drawn up according to the mass conservation principle ... 

Carver-Greenfield process for extraction of oily waste Chemtect gaseous waste treatment freeze separation membrane microfiltration... 

Our energy supply is based to a large extent on the combustion of fossil fuels. The thermal energy released in this process can be used as such, but it can also be converted into electricity. In both cases, the gaseous waste constitutes an environmental danger it is... 

The electrolyte is an all-important part of the fuel cell. The reacting gases diffuse through the electrolyte to the surface of the electrodes, where the reactions take place. The ions are transported from the cathode to the anode through the electrolyte finally, the gaseous waste is transported through the electrolyte, back to the process gas streams. 

Table 5.24 presents potential sources of emissions during refining and petrochemical processes involved in crude petroleum treatment and Table 5.25 shows an estimate of gaseous wastes from petroleum refining plants with a capacity of 2.5 x 10 t of raw petroleum (which is equivalent to 1000 MWj yr ). 

Treatment of Caseous Waste. Gaseous wastes arise from the ventilation of process vessels and the concrete cells that house the plant and equipment used for reprocessing spent nuclear fuel. This gaseous waste is largely air contaminated with small entrained liquid or solid particles containing radioactive components. Some ventilation streams also are contaminated with oxides of nitrogen. 

The Army s test results for the PLASMOX technology raise a number of regulatory issues that must be resolved before this system could be permitted in the United States. These include improvements to the gas scrubber system, more complete knowledge of the fate of key components of the NSCWM (e.g., phosphorus), and better characterization of the solid, liquid, and gaseous waste streams. The processes used by U.S. plasma arc vendors also differ in significant ways from the PLASMOX process tested by the Army. 

---