Journal of the University of Chemical Technology and Metallurgy, 40, Book 2, 2005

EDITOR-IN- CHIEF
Prof. DSc Rumen I. Dimitrov
Department of Fundamentals of ChemicalTechnology,
Tel: (+ 359 2) 62 54 485
University of Chemical Technology and Metallurgy,
8 Kl. Ohridski ., 1756 Sofia, Bulgaria
E-mail: rumen@uctm.edu

Chapters:

 

Review
METHODS FOR DETERMINATION OF MICROPORE SIZE DISTRIBUTION
P. Nikolov, D. Mehandjiev
Chemical Technology
 ELECTROCHEMICAL SURFACE TREATMENT OF CASTINGS AND DETAILS IN ION MELTS
N. Lingorsky
ELECTRICAL PROPERTIES OF BUTYL RUBBER COMPOSITES CONTAINING BORON CARBIDE
F. El-Tantawy1, N. Dishovsky2
EFFECT OF THE LACCASE-MEDIATOR SYSTEM ON THE OXYGEN AND CHLORINE DIOXIDE PULP BLEACHING
I. Valchev, G. Radeva, E. Valcheva
STRUCTURAL DESIGN OF PACKINGS THROUGH CAD SYSTEM
D. Rozalinov I. Stoeva
Chemical Engineering
 PRELIMINARY ACTIVATION OF ZEOLITES FOR GAS AND VAPOUR ADSORPTION
E. Ivanova, B. Koumanova
THE APPLICATION OF NATURAL MATERIALS IN THE BIOTREATMENT OF PHENOLIC WASTEWATERS
B. Koumanova, Z. Yaneva
Metallurgy
STUDIES ON A TECHNOGY FOR PRODUCTION OF STEEL BIMETALIC INGOTS BY ELECTROSLAG REMELTING
Z. Zlatev, H. Argirov
STRUCTURE INVESTIGATION OF STEEL BIMETALLIC INGOTS PRODUCED BY THE ELECTROSLAG REMELTING METHOD
H. Argirov, Z. Zlatev
Chemistry
 ON KINETICS OF â -OXIDE FORMATION ON PtT IN AN ALKALINE MEDIUM
P. Iotov, S. Kalcheva
Technical Scieances
 MONTE CARLO ERROR ANALYSIS OF A STRAIN GAUGE MONITORING DEVICE
C. Pavlitov1, A. Aleksandrov2, R. Rusinov1, G. Bayram2
GENERATOR OF UNIPOLAR MAGNETIC IMPULSES
A. Andonov1, I. Kostov2, S. Parvanov1
INVESTIGATION OF THE INTERACTION IN HYPERELASTIC-RIGID COUPLE DURING SLIDING
V. Iliev, R. Yovchev, G. Mihailov

 

METHODS FOR DETERMINATION OF MICROPORE SIZE DISTRIBUTION
P. Nikolov, D. Mehandjiev

Institute of General and Inorganic Chemistry Bulgarian
Academy of Sciences
“Acad. G. Bonchev” str., bl. 11, 1113 Sofia, Bulgaria
e-mail: plamen_m.nikolov@abv.bg
 Received 12 May 2005
Accepted 18 May 2005

The most often used methods for determination of micropore size distribution are analyzed. The methods are classified from mathematical point of view and comparisons between their advantages and drawbacks are made. The most important problems arising from their application are noted. The main conclusion is that all modern methods incorporate some arbitrary assumptions and the micropore size distributions depend from the chosen models.
Keywords: pore size distribution, micropores, adsorption, generalized adsorption isotherm.

ELECTROCHEMICAL SURFACE TREATMENT OF CASTINGS AND DETAILS IN ION MELTS
N. Lingorsky

University of Chemical Technology and Metallurgy
8 Kliment Ohridski, 1756 Sofia, Bulgaria
e-mail: lingorsky@abv.bg
 Received 24 March 2005
Accepted 27 April 2005

A review of the technologies for electrochemical surface cleaning of castings and details in ionic melts from scale and doss is presented. The research work in the finding of new compositions of ionic melts and the chemical processes of the scale and doss decomposition are thoroughly considered. The probable cathode and anode processes of the electrolysis and the discharging gases at the electrodes are summarized. The results for the optimal parameters of the electrochemical process: current density, temperature and composition of the melt, number and duration of the cathode and anode cycles etc. are assessed. The secondary cleaning processes of the castings: rinsing with water as well as surface passivation with H3PO4 are also described. Data on the corrosion resistance of number of construction materials used in the installations for electrochemical cleaning of castings and details in the most common ionic melts of NaOH with the addition of carbonates is reported. A review of the incorporated in the Bulgarian industry technological equipment for finishing treatment of castings and details is made, as the trends for future investigations in this field are pointed out.
Keywords: ion melts, casting, detail, reversible electrolysis.



ELECTRICAL PROPERTIES OF BUTYL RUBBER COMPOSITES CONTAINING
BORON CARBIDE
F. El-Tantawy1, N. Dishovsky2

1Department of Physics
Suez Canal University Ismailia, Egypt
2Department of Polymer Engineering
University of Chemical Technology and Metallurgy
1756 Sofia, Bulgaria
e-mail: dishov@uctm.edu
 Received 12 May 2005
Accepted 17 May 2005

The effect of boron carbide B4C ceramic on the electrical characteristics of butyl rubber based vulcanizates is investigated. Static electrical conductivity, thermoelectric power, conductivity temperature dependence, current-voltagetemperature characteristics and dielectric constant-temperature dependence are studied as a function of the filler content in the region 20-40 phr. The considerable effect of B4C on all investigated properties is observed. It is shown that tunneling mechanism controls the conduction mechanism in the butyl rubber/ B4C composites. Thermoelectric power confirms that the butyl rubber/B4C compound is a p-type semiconductor. Electrical conductivity temperature dependence shows double NTCC and PTCC effect.
Keywords: butyl rubber/B4C composites, electrical properties.



EFFECT OF THE LACCASE-MEDIATOR SYSTEM ON THE OXYGEN AND CHLORINE DIOXIDE PULP BLEACHING
I. Valchev, G. Radeva, E. Valcheva

University of Chemical Technology and Metallurgy
8 Kl. Ohridski, 1756 Sofia, Bulgaria
e-mail: ivoval@uctm.edu
 Received 19 April 2005
Accepted 26 April 2005

Pulp delignification with the laccase-mediator system exhibits favorable bleaching properties and has an environmental impact. The aim of the present paper is to study the effect of the laccase-mediator system on the delignification and the
pulp properties after the subsequent bleaching with oxygen and chlorine dioxide. An unbleached and an oxygen bleached hard wood pulp are used in a study of delignification with system laccase NS 51002 of Novozymes AS and mediator HBT. The enzyme treatment is carried out in the temperature interval 30oC - 60°C, while the reaction time variation ranges from 30 min to 180 min. The kinetics of kappa reduction and brightness increase is studied. It is found that an exponentional kinetic equation can be applied and that there is a correlation between the kappa number and the absorption coefficient. A higher delignification effect of the enzyme treatment (additional kappa reduction more than 30 %) after the chlorine dioxide bleaching is achieved. The laccase-mediator system does not affect the pulp viscosity.
Keywords: laccase-mediator system, pulp bleaching, kinetics.



STRUCTURAL DESIGN OF PACKINGS THROUGH CAD SYSTEM
D. Rozalinov I. Stoeva

University of Chemical Technology and Metallurgy
8 Kl. Ohridski blvd, 1756 Sofia, Bulgaria
e-mail: roz@uctm.edu
 Received 10 March 2005
Accepted 14 May 2005

The polygraphic industry undergoes fundamental changes. Marketing economics call for a combination of high quality and low cost price of the production. This is achieved by automation of the production, implementation of high technologies and the use of innovational materials. A whole new generation of specialized software has been applied, based on CAD systems (Computer Aided Design) i.e. computer assisted design. Their study, application and analysis in the field of the structural design of packings are the subject of research of this article. The CAD/CAM/CAE systems began their development in 1975. The efficiency of their implementation was proved in 1995. In 1998 begins the development of specialized CAD/CAM/ CAE packets intended for the structural design of packings. For the first time at the polygraphic exhibition DRUPA 2000, there was presented a new CAD system. It is based on a parametrical and variational CAD system. The product “Eng View Synergy” of the ENG VIEW Systems Company is a totally new and revolutionizing concept for the structural design of packings. The packings, developed in different structural design in response to the requirements of the practice, and with the assistance of the CAD system “ ENG VIEW SYNERGY”, demonstrate significant opportunities, namely – substantial facilitation of the processes of their structural design and shaping. Based on the experiment that was carried out, we defined the advantages and the disadvantages of the implemented CAD system. They have to be taken into consideration for the development of new program product, created on the basis of the parametrical and variational CAD for the structural design of the packings. There has been proposed a solution through the introduction of a subsystem with artificial intelligence. This is an intelligent computer program which makes use of knowledge and procedures for finding solutions aiming at solving problems that are too complicated and require human expertise in order to be resolved properly.
Keywords: design, packing, CAD/CAM, paperboards.

University of Chemical Technology and Metallurgy
8 Kl. Ohridski, Sofia 1756, Bulgaria
e-mail: almi8473@yahoo.com
 Received 10 May 2005
Accepted 07 June 2005

The possibility of improving the properties of natural clinoptilolite taken from the southeastern part of Bulgaria, for the adsorption of sulfur dioxide and vapours of water, methanol and ethanol, was studied. The selectivity of the zeolite increases in the order: C2H5OH < CH3OH < SO2 < H2O. The activation by washing out with warm distilled water leads to double increase of the distribution coefficient. The water in the pores of the natural and synthetic zeolites should be removed for the most effective use of their adsorption volume. In the recent research this was achieved by heating. The thermal activation of the samples even only at 120oC increased two to three times the zeolite adsorption capacity. Chemical activation of the natural clinoptilolite, through multiple treatment of the samples with hydrochloric acid solutions with constant and varying concentrations, was tested as a possibility for alteration of the clinoptilolite properties. The influence on the distribution coefficient is various, for SO2 it passes through maximum, for H2O it decreases and for C2H5OH – remains nearly constant.
Keywords: adsorption, natural clinoptilolite, activation, sulfur dioxide, vapours of water, methanol and ethanol.



THE APPLICATION OF NATURAL MATERIALS IN THE BIOTREATMENT OF PHENOLIC WASTEWATERS
B. Koumanova, Z. Yaneva

University of Chemical Technology and Metallurgy
8 Kl. Ohridski, 1756 Sofia, Bulgaria
e-mail: bogdana@uctm.edu
 Received 10 May 2005
Accepted 07 June 2005

The effect of the sorbents (bentonite, perlite and activated carbon (AC)), on the biotreatment of wastewaters containing phenol (P), 2-nitrophenol (2-NP), 4-chlorophenol (4-CP) and 2,5-dichlorophenol (2,5-DCP), respectively, was investigated. The removal of phenol and its derivatives through aerobic process without any sorbent has been also studied. Comparing both processes it was established that the time necessary for complete removal of the pollutants was considerably shortened when the adsorbent is added. The comparative analyses of biological oxidation, pure adsorption and sorbent assisted bioprocess demonstrated the feasibility and effectiveness of the combined process for the removal of toxic recalcitrant organics.
Keywords: phenol, 2-nitrophenol, 4-chlorophenol, 2,5-dichlorophenol, sorbent assisted bioprocess, bentonite, perlite, activated carbon.

 

STUDIES ON A TECHNOGY FOR PRODUCTION OF STEEL BIMETALIC INGOTS BY ELECTROSLAG REMELTING
Z. Zlatev, H. Argirov

Institute of Metal Science, Bulgarian Academy of Science
67 Shipchenski prohod Str., 1574 Sofia, Bulgaria
e-mail: h.argirov@ims.bas.bg
 Received 08 February 2005
Accepted 11 March 2005

The most frequently used methods for producing bimetal are based on deformation, detonation forming, thermal diffusion, special processes of melting and electrochemical deposition. The metallurgical techniques for bonding present interest. We have carried out research for working out technological electroslag remelting conditions to produce bimetallic ingots. A new plant flow diagram has been developed for the manufacture. Experimental melting was performed on a laboratory electroslag remelting installation. Bimetallic ingots were produced of different steel grades.
Keywords: metallurgy, electroslag remelting, bimetal, ingots, steels.



STRUCTURE INVESTIGATION OF STEEL BIMETALLIC INGOTS PRODUCED BY THE ELECTROSLAG REMELTING METHOD
H. Argirov, Z. Zlatev

Institute of Metal Science, Bulgarian Academy of Science
67 Shipchenski prohod Str., 1574 Sofia, Bulgaria
e-mail: h.argirov@ims.bas.bg
 Received 08 February 2005
Accepted 11 March 2005

The quality of layers bonding in clad metal should be such, that its exfoliation in service would be impossible. Clad metal should be technological in manufacturing various products from it. Thus, economic effect is achieved for the chosen ratio of the steel layers thickness and production processes. Complex properties and new technological properties, which are missing in one-layer steels, are obtained. Bimetallic steel ingots are produced in an electroslag remelting installation. Macro - and microstructure are analysed. It is established that the structure of the steels is dense, free of defects. A complete fusion is achieved.
Keywords: bimetal, ingots, steels, macrostructure, microstructure

 

ON KINETICS OF â -OXIDE FORMATION ON PtT IN AN ALKALINE MEDIUM
P. Iotov, S. Kalcheva

University of Chemical Technology and Metallurgy
8 Kl. Ohridski blvd, 1756 Sofia, Bulgaria
E-mail: iotov@uctm.edu
 Received 27 May 2005
Accepted 07 June 2005

Surface oxides on Pt in 0.05 M KOH are formed potentiostatically at potentials varying between 2.00 and 2.50 V for polarization times, tp , up to 738 s at temperature values in the range from 293 to 313 T. This procedure results in deposition of â-oxide films whose charge density, qox , is less than 0.945 mC cm-2. Cyclic voltammetry reveals one oxide reduction peak whose potential value depends on the polarization potential and time but not on the temperature of the electrolyte. The temperature increase leads only to augmentation of the oxide thickness. The linear plots of 1/ qox versus log tp obtained for different polarization potential and temperature values show that the oxide growth follows inverselogarithmic kinetics and hence the process is limited by the rate of escape of Pt4+ from the metal into the oxide. The experimental data provide to determine the potential drop across the film and the intensity of electric field within the oxide layer. The latter values are compared to those obtained for â-oxide films grown on Au under identical conditions. They are suggested to match the requirement imposed by the oxide growth mechanism.
Keywords: â-oxide, platinum, oxide growth kinetics, potentiostatic polarization.