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In recent years, Chinese environmental authorities have expressed interest in the use of Tradable Discharge Permits (TDP) as a regulatory instrument to control pollutant emissions. Environmental professionals still have not had enough experience however, in designing and managing TDP systems, especially for non-uniformly dispersed pollutants. As an empirical study, this paper proposes an inter-zonal TDP system and analyzes its effectiveness in cost saving and environmental protection for reducing water pollutant COD (Chemical oxygen demand) in Tianjin, China. Zonal permit system (ZPS) and emission permit system (EPS) are discussed for comparison. The inter-zonal TDP System is demonstrated to improve cost efficiency by allowing permit trades between zones, as long as water quality constraints are satisfied. The transactions are assumed to proceed in a multilateral sequential way and are simulated with a circularly running linear programming (LP) model. The simulation of permit transactions among 20 firms shows that to reach the same COD removal target, ZPS, inter-zonal TDP system, and EPS lowered the total reduction cost by 12.8%, 14.6%, and 15.8%, respectively. EPS, however, brought about "hot spots" problem. Finally, the transaction costs and sensitivity of the three TDP systems to changes in both COD reduction rate and the initial permit allocation are discussed, and policy implications are addressed. [ABSTRACT FROM AUTHOR]

Thesolubility of ammonium metavanadate (NH4VO3)in ammonium salt solution is significant for the precipitationof NH4VO3from the vanadium-containing solution.The solubilities of NH4VO3in the (NH4)2SO4–H2O, NH4Cl–H2O, and (NH4)2SO4–NH3–H2O systems weremeasured using dynamic method in the temperature range from (298 to343) K. The investigated concentration is up to 3.0 mol·kg–1, 2.5 mol·kg–1, and 5.2 mol·kg–1for (NH4)2SO4, NH4Cl, and NH3, respectively. The solubility of NH4VO3decreases sharply with the addition of (NH4)2SO4or NH4Cl while thesolubility of NH4VO3in the mixed NH3and (NH4)2SO4(0.10 mol·kg–1) solution increases first and then levels off withincreasing NH3concentration. The solubility product constant(KSP) of NH4VO3wasalso determined using the standard-state thermodynamic data. The Bromley–Zemaitismodel was applied to model the solubility of NH4VO3in the systems mentioned above, and five pairs of new modelparameters were obtained via the regression of the experimental solubilities.A chemical model was established to successfully calculate the solubilityof NH4VO3in all systems. All of the work donein this research will provide a thermodynamic basis for industrialdevelopment in the precipitation of NH4VO3. [ABSTRACT FROM AUTHOR]

The solubility of gypsum (CaSO4·2H2O) in ammonium solutions plays a significant role to preventgypsum scaling on the heater and tower in the treatment of ammonium-Nwastewater bearing sulfate ions by the steam stripping process. Inthis work solubilities of calcium sulfate dihydrate in NH4Cl, NH4NO3, and mixed NH4Cl and(NH4)2SO4solutions up to 343.15K were measured using the classic isothermal dissolution method. Theinvestigated concentration (at ambient temperature) is up to 1.50mol·dm–3for both NH4Cl and NH4NO3. The solubility of CaSO4·2H2O was found to increase sharply with either NH4Cl or NH4NO3concentration, whereas the temperaturehas a limited effect. The XRD analysis of equilibrated solids forthese systems shows that CaSO4·2H2O isstable in all cases over the temperature range (298.15 to 343.15)K. The electrolyte nonrandom two-liquid (the electrolyte NRTL) modelembedded in AspenPlus was applied to model the solubility of CaSO4·2H2O in the above systems. The newly obtainedmodel parameters were used to well estimate the solubility of CaSO4·2H2O in all cases with a relative deviationof 1.52 %. [ABSTRACT FROM AUTHOR]

Oneof the key steps of coking wastewater treatment is phenolicand tar removal via extraction. However, the high loss of the extractant,i.e., methyl isobutyl ketone (MIBK), leads to the high cost of theprocess. The adoption of a novel solvent or solvent blend is consideredas an efficient way to address this problem. In this paper, sevensolvents (benzene, toluene, m-xylene, ethylbenzene, 1, 3, 5-trimethylbenze,cyclohexane, and octanol), selected as candidate diluters for MIBKaccording to operating requirements, are studied with a nonlinearprogramming (NLP) model based on ideal counter-current extraction.The results, verified with experiments, suggest toluene is the mostpromising candidate. Further investigation of this solvent blend revealsthat both Dblend(the distribution coefficientof phenol between solvent blend and water) and mMIBK(the MIBK concentration in raffinate) increase with xMIBK(the molar fraction of MIBK in blend).The trade-off between the extraction performance and MIBK loss recommendsthe blend with xMIBK= 0.05 as extractantfor coking wastewater treatment. An industrial process consistingof extraction, back stripping, distillation, and mixer is presented.A corresponding NLP model is established for its operating optimization.To improve the accuracy, the representatives of typical phenolicsand tar in wastewater (2,4 dimethyl phenol, m-xylene, and quinolone)are also considered in addition to phenol. The case study indicatesthat the blend exhibits economic advantage over pure MIBK with a makeupcost of 11.15 ¥/t, much less than the 185.15 ¥/t in thecase of MIBK. [ABSTRACT FROM AUTHOR]

Duckweedbiomass is gasified in a thermochemical-based superstructureto produce gasoline, diesel, and kerosene using a synthesis gas intermediate.The superstructure includes multiple pathways for conversion of thesynthesis gas to liquid hydrocarbons via Fischer–Tropsch synthesisor intermediate methanol synthesis. Low-temperature and high-temperatureFischer–Tropsch processes are examined using both iron andcobalt based catalysts. Methanol may be converted to hydrocarbonsvia the methanol-to-gasoline or methanol-to-olefins processes. Thehydrocarbons will be refined into the final liquid products usingZSM-5 catalytic conversion, oligomerization, alkylation, isomerization,hydrotreating, reforming, and hydrocracking. A process synthesis frameworkis outlined to select the refining pathway that will produce the liquidfuels as the lowest possible cost. A rigorous deterministic branch-and-boundglobal optimization strategy will be incorporated to theoreticallyguarantee that the overall cost of the solution chosen by the synthesisframework is within a small fraction of the best possible value. Aheat, power, and water integration is incorporated within the processsynthesis framework to ensure that the cost of utility productionand wastewater treatment are simultaneously included with the synthesisof the core refining processes. The proposed process synthesis frameworkis demonstrated using four case studies which determine the effectof refinery capacity and liquid fuel composition on the overall systemcost, the refinery topological design, the process material/energybalances, and the lifecycle greenhouse gas emissions. [ABSTRACT FROM AUTHOR]