Juha Tanskanen

Homotopy parameter bounding in increasing the robustness of homotopy continuation methods in multiplicity studies

Homotopy continuation methods are globally convergent methods, which can also be utilized in multiplicity studies. However, when the starting point and/or solution multiplicities lie on separate homotopy path branches, one or more of the solutions may be missed. This is due to the absence of real space connections between separate homotopy path branches, thus preventing multiple solutions being reached from a single starting point. In this paper, a concept is presented that enables a tracking starting point and solution multiplicities in cases where the standard problem-independent homotopy method fails. The concept is based on homotopy parameter bounding and enables the connection of separate homotopy path branches. The concept performance is examined using distillation column examples. In the examined cases the concept is found to improve robustness by establishing a path in real space such that solutions are approached that would be unattainable using the standard homotopy method.

Removal of nitrate by modified pine sawdust: Effects of temperature and co-existing anions

The effect of temperature, sulphate and phosphate, and the initial nitrate concentration on nitrate removal was studied with synthetic solutions. Chemically modified pine sawdust (Pinus sylvestris) anion exchange resin (MPSD) was used in the sorption studies. The resin was synthesized by reacting pine sawdust with epichlorohydrin, ethylenediamine and triethylamine in the presence of N,N-dimethylformamide. Nitrate removal was successful at 5-70 °C. Higher temperatures caused nitrate removal to decrease moderately, but sorption capacities of 22.2-32.8 mg/g for NO3-N were achieved. The removal of nitrate in the presence of sulphate or phosphate was studied at concentrations of 30 mg N/l, 10-500 mg S/l and 1-50 mg P/l. A significant decrease in nitrate reduction was observed at sulphate and phosphate concentrations of 100 mg S/l and 50 mg P/l, respectively. The effect of initial nitrate concentration was studied in column. Nitrate sorption was clearly dependent on the initial concentration. Desorption of nitrate in column was completed using about 80 bed volumes of 0.1 M NaCl solution. The sorption data were fitted to the Langmuir, Freundlich and Redlich-Peterson adsorption models. The Redlich-Peterson and Langmuir models gave the best fit, which suggests monolayer sorption. Thermodynamic studies revealed that the sorption of nitrate was spontaneous and exothermic in nature. The results imply that modified pine sawdust could be a feasible alternative in the treatment of real industrial wastewaters.

Removal of nickel and vanadium from ammoniacal industrial wastewater by ion exchange and adsorption on activated carbon

AbstractNickel and vanadium were removed from real ammoniacal industrial wastewater (Ni 2–4, V 40–50 mg/L) obtained from a synthesis gas scrubber. The aim of the study was to develop an industrial application for simultaneous removal of nickel and vanadium. The studied methods were adsorption (activated carbon (AC), AquaSorb® 2000), anion exchange (Amberjet™ 4200 Cl) and cation exchange (Amberjet™ 1200 H). AC removed > 95% of nickel at pH 5.5–9 (dose > 2 g/L) but the vanadium uptake remained poor. In batch cation exchange, all nickel was removed (optimum pH 4–7) and 70–75% of vanadium was removed at pH 7 (5–10 g/L). All nickel was removed in batch anion exchange (optimum pH 5.5–9, 2–10 g/L). Over 89% of vanadium was removed in batch anion exchange at pH 7 (1–10 g/L). Adsorption capacities of 4.36 and 48.9 mg/g were obtained for nickel and vanadium in anion exchange at pH 7. In column anion exchange, all nickel and 92–98% of vanadium were removed in all three ion exchange cycles at pH 7–9. In regeneration,...

Performance of a commercial industrial-scale UF-based process for treatment of oily wastewaters.

An evaluation was made of the performance of a commercial industrial-scale ultrafiltration (UF)-based process for treatment of highly concentrated oily wastewaters. Wastewater samples were gathered from two plants treating industrial wastewaters in 2008, and in 2011 (only from one of the plants), from three points of a UF-based treatment train. The wastewater samples were analyzed by measuring the BOD7, COD, TOC and total surface charge (TSC). The inorganic content and zeta potentials of the samples were analyzed and GC-FID/MS analyses were performed. The removal performances of BOD7, COD, TOC and TSC in 2008 and 2011 for both plants were very high. Initial concentrations of contaminants in 2011 were lower than in 2008, therefore the COD and TSC reductions were also lower in 2011 than three years before. Regardless of the high performance of UF-based processes in both plants, at times the residual concentrations were considerable. This could be explained by the high initial concentrations and also by the presence of the dissolved compounds that were characterized. Linear correlation was observed between COD and TOC, and between COD and TSC. The correlation between COD and TSC could be utilized for process control purposes.

Graphical targeting procedures for reactor systems

Abstract This paper demonstrates how it is possible to extend the ‘attainable region’ concept (Glasser, Hildebrandt and Crowe [1]) to reactor systems with a larger number of components present. The extended procedure is demonstrated on the steam reforming reactions, a system that is originally described by three reactions and five components. Further, we address the entire reactor/recycle/separation system. A graphical representation of the process in the composition space is presented. This representation may form the foundation for a new graphical synthesis concept.

Hydrolysis of organosolv wheat pulp in formic acid at high temperature for glucose production

Organosolv methods can be used to delignify lignocellulosic crop residues for pulp production or to pretreat them prior to enzymatic hydrolysis for bioethanol production. In this study, organic solvent was used as an acidic hydrolysis catalyst to produce glucose. Hydrolysis experiments were carried out in 5-20% formic acid at 180-220 °C. Wheat straw pulp delignified with a formicodeli™ method was used as a raw material. It was found that glucose yields from pulp are significantly higher than yields from microcrystalline cellulose, a model component for cellulose hydrolysis. The results indicate that cellulose hydrolysis of real fibers takes place more selectively to glucose than hydrolysis of microcrystalline cellulose particles does. The effect of the particle size on pulp hydrolysis was investigated, the crystallinity of hydrolyzed pulp was measured by XRD analysis, and the product distribution and its influence on the process was discussed.

Acid-catalysed xylose dehydration into furfural in the presence of kraft lignin.

In this study, the effects of kraft lignin (Indulin AT) on acid-catalysed xylose dehydration into furfural were studied in formic and sulphuric acids. The study was done using D-optimal design. Three variables in both acids were included in the design: time (20-80 min), temperature (160-180°C) and initial lignin concentration (0-20 g/l). The dependent variables were xylose conversion, furfural yield, furfural selectivity and pH change. The results showed that the xylose conversion and furfural yield decreased in sulphuric acid, while in formic acid the changes were minor. Additionally, it was showed that lignin has an acid-neutralising capacity, and the added lignin increased the pH of reactant solutions in both acids. The pH rise was considerably lower in formic acid than in sulphuric acid. However, the higher pH did not explain all the changes in conversion and yield, and thus lignin evidently inhibits the formation of furfural.

Kinetics of furfural destruction in a formic acid medium

Furfural is one of the key chemicals produced from hemicellulose pentosans in acidic conditions. In the same conditions, furfural also undergoes degradation reactions leading to yield loss. In this study, the kinetics of furfural degradation in a formic acid medium containing 2 to 30% (w/w) formic acid and 0.05 to 0.16 mol L−1 furfural was studied in small batch reactors. The reaction temperatures were 160, 180, and 200 °C. The results showed that the overall order of the reaction changes with the amount of formic acid catalyst: in high acid concentration (30%) the apparent order of reaction is over one and in low acid concentration (2%) the order of reaction is below one. The proposed kinetic model, which includes an uncatalysed and an acid-catalysed term, is capable of estimating this behaviour. The model and findings presented in this study can support the optimisation of furfural production conditions.

Phenomenon driven process design methodology: Focus on reactive distillation

Abstract The phenomena oriented process design approach was introduced in a previous paper [1]. In the present paper the approach is formalized into what is called ‘Phenomenon driven process design methodology’. The features of the methodology are demonstrated by applying the methodology to the design of MTBE production process. The example aims at illustrating how creativity can be included in process design in a systematic way.

Vanadium(V) removal from aqueous solution and real wastewater using quaternized pine sawdust.

Cross-linked and quaternized pine sawdust was tested for vanadium removal from a synthetic aqueous solution as well as from real industrial wastewater which had a considerable amount of vanadium and other ions such as sulphate, ammonium and nickel. The maximum vanadium sorption capacity of the modified pine sawdust was found to be 130 mg/g in synthetic solution and 103 mg/g in real wastewater. Modified pine sawdust worked well over a wide range of pH. Column studies with real wastewater proved that vanadium was efficiently desorbed from the material with 2 M NaOH and that the material could be reused.