Janvit Golob

Growth, lipid extraction and thermal degradation of the microalga Chlorella vulgaris

The microalga Chlorella vulgaris was cultured in a combined medium obtained by mixing standard Jaworski medium with a solution from the modified Solvay process that contained only NaHCO(3) and NH(4)Cl. Cell number, pH and nitrogen content were monitored throughout growth. Lipids were extracted from lyophilised biomass using CHCl(3)-MeOH. A combination of grinding, microwave treatment and sonication proved to give the best lipid extract yield. Freeze-dried algal biomass was also utilised for thermal degradation studies. The degradation exhibited three distinct regions - primary cell structure breakage paralleled by evaporation of water, followed by two predominant exothermic degradation processes. The latter were modelled using nth order apparent kinetics. The activation energies of the degradation processes were determined to be 120-126kJ/mol and 122-132kJ/mol, respectively. The degradation model may be readily applied to an assortment of thermal algal processes, especially those relating to renewable energy.

The Structure and Properties of Acrylic-Polyurethane Hybrid Emulsions and Comparison with Physical Blends

Aqueous acrylic-polyurethane hybrid emulsions were prepared by semi- batch emulsion polymerization of a mixture of acrylic monomers (butyl acrylate, methyl methacrylate, and acrylic acid) in the presence of polyurethane dispersion. Equivalent physical blends were prepared by mixing acrylic emulsion and polyurethane dispersion. The weight ratio between acrylic and polyurethane components varied to obtain differ- ent emulsion properties, microphase structure, and mechanical film properties of hy- brid emulsions and physical blends. Particle size and molecular mass measurements, scanning electron microscopy, glass transition temperature, and rheological measure- ments performed characterization of the latex system. The mechanical properties were investigated by measuring tensile strength and Koenig hardness of dried films. The experimental results indicate better acrylic-polyurethane compatibility in hybrid emul- sions than in physical blends, resulting in improved chemical and mechanical proper- ties.

Co-gasification of biomass and plastics: Pyrolysis kinetics studies, experiments on 100 kW dual fluidized bed pilot plant and development of thermodynamic equilibrium model and balances

Thermo-gravimetric analysis (TGA) of volatilization reaction kinetics for 50 wt.% mixtures of plastics (PE) and biomass (wood pellets) as well as for 100 wt.% plastics was conducted to predict decomposition times at 850°C and 900°C using iso-conversional model method. For mixtures, agreement with residence time of dual fluidized bed (DFB) reactor, treated as continuous stirred-tank reactor (CSTR), was obtained at large conversions. Mono-gasification of plastics and its co-gasification with biomass were performed in DFB pilot plant, using olivine as heterogeneous catalyst and heat transfer agent. It was found that co-gasification led to successful thermochemical conversion of plastics as opposed to mono-gasification. Unknown flow rates were determined applying nonlinear regression to energy and mass balances acknowledging combustion fuel, air, steam, feedstock, but also exiting char, tar, steam and other components in DFB gasification unit. Water-gas shift equilibrium and methanol synthesis requirements were incorporated into gasification model, based on measurements.

Testing a prototype pulse generator for a continuous flow system and its use for E. coli inactivation and microalgae lipid extraction.

Among other applications, electroporation is used for the inactivation of pathogens and extraction of substances from microorganisms in liquids where large scale flow systems are used. The aim of our work was therefore to test a pulse generator that enables continuous pulsed electric field (PEF) treatment for Escherichia coli inactivation and microalgae lipid extraction. In the continuous flow PEF system, the flow rate was adjusted so that each bacterial cell received a defined number of pulses. The results of PEF flow treatment showed that the number of pulses influences E. coli inactivation to the same extent as in the previously described cuvette system, i.e., batch system. The continuous flow PEF system was also tested and evaluated for lipid extraction from microalgae Chlorella vulgaris. In control experiments, lipids were extracted via concentration of biomass, drying and cell rupture using pressure or an organic solvent. In contrast, electroporation bypasses all stages, since cells were directly ruptured in the broth and the oil that floated on the broth was skimmed off. The initial experiments showed a 50% oil yield using the electroporation flow system in comparison to extraction with organic solvent.

IR Drying of Water-Based Acrylic PSA Adhesives

Results of infrared drying of an acrylic microsphere adhesive coating are presented. The effect of IR drying on adhesive coating was analyzed by Fourier transform infrared spectroscopy (FTIR). The adhesion strength was tested by peel adhesion measurement. Drying was experimentally carried out on materials dried to the same moisture extent at different operating conditions. The power of IR heating source, time of drying, and distance between adhesive coating and heating source were varied. The developed phenomenological model was compared with existing empirical models.

Thermal Hydrolysis of Cyanides in Spent Pot Lining of Aluminium Electrolysis

The spent lining of electrolysis pots is the main source of solid wastes in the production of aluminium. Being contaminated by cyanides, they may cause serious environmental problems for ground and surface waters. They have to be disposed of as special wastes or decontaminated prior to final disposal. This paper described the removal of free and complex cyanides from the spent pot lining waste by thermal hydrolysis. In addition, fluorides in the hydrolysis filtrate were precipitated by Ca(OH) 2 and disposed of together with the hydrolysed spent pot lining material.

Extraction of Non-polar Molecules from Green Alga Chlorella vulgaris by Electroporation

Preliminary study with extraction by electroporation of non-polar molecules from green alga Chlorella vulgaris showed very promising results. For successful extraction by electroporation from above mentioned alga takes at least 3.8 kJ of energy input/L dense algae, the best extraction is carried out around 7.2 kJ of energy input/L dense algae (at the amplitude of the electric field from 0,5 to 2,7 kV/cm). A sufficient quantity of algal biomass (dense algal suspension has > 107 cells/L in our experimental conditions). Indeed, when more cells are present in the suspension, the less likely the pulse will avoid cells due to the conductivity of the medium, resulting in better extraction by electroporation. It is also important to have optimal conductivity of the medium (1 to 1.3 mS/cm in our experimental conditions). Studied extraction by electroporation parameters for chosen alga (voltage, pulse length and different number of pulses delivered to biomass) and algal growth regeneration after different electroporation settings are presented.

Extraction of Sugar Solution from Sugar Beet Cossettes by Electroporation and Compressive Load

Extraction of sugar solution from sugar beet cossettes has been studied at different parameters of electric pulses, with electric field intensities varying from 0.52 to 1.52 kV/cm. Sugar beet has been exposed to different number of electric pulses of different duration. Experiments where the only treatment was compressive load gave us maximum juice yield of 30.64 %, with PEF treatment added juice yield rose to a maximum of 80.32%. The whole process lasted 30 minutes. The first 5 minutes we pressed with pressure of 9.254 bars, then electric pulses were applied, followed by additional 25 minutes of pressing. To compare juice yields and specific energy consumption, we also performed experiments replacing PEF treatment with more established thermal treatment at temperatures (30, 40, 50, 60, 72) °C.