Institute of Chemical Engineering
"Heat and Mass-Transfer in gas-liquid systems"
Main topics of investigations:
1. Packed bed columns for absorption, desorption, distillation, and direct heating. Development of new high efficient packings, especially for extremely low and extremely high liquid superficial velocity, new types of liquid phase distributors and devices for wall effect elimination.
2. Unified method and program for calculation of packed bed column apparatuses for absorption, desorption, distillation, and direct heating using in all cases the same non-linear balance differential equation and the same equation for determination of mass transfer coefficient. The heat transfer coefficient is calculated using the analogy between heat and mass transfer. The Marangoni effect and the axial mixing are taken into account.
3. Development of bioreactor with semi fixed packing for aerobic and anaerobic processes, especially appropriate for waste water purification.
4. Technologies for SO2 and NOx removal and for utilization of flue gases heat.
5. New structured active carbon for use as adsorbent and catalyst carrier. The essence of the invention is that the active carbon is formed in such a way, that the fluid flows through its capillaries. Thus the thickness of the diffusion layer is very low, not larger than the capillary radius. It means the diffusion does not limit the process.
Industrial contacts:
Up to now, in Bulgaria and in many other countries, more than 900 apparatuses and installations are implemented in the industry for carrying out 17 different technological processes, such as absorption, desorption, distillation, and direct heating, mainly for purification of wastegases and waste waters and for utilization of flue gases heat. All of them are after our patents and basic design.
Scientific products intended to be implemented in industry
1. Enhancement of the energy efficiency of the Wellman-Lord method for purification of flue gases from sulfur dioxide.
A new type of a packing and a distributor enabling purification of flue gases containing sulfur dioxide by absorption with water solution of sodium sulfite/ bisulfite in packed columns at full countercurrent regime. The increase of the absorption driving force leads to reduced apparatus height and steam consumption for solution regeneration. The quantity of water evaporated for solution regeneration is reduced from 8 to 6.2 kg/kg sulfur dioxide.
State of readiness: installation design, know-how commitment
2. System with a gas-steam turbine and contact economizers
A new system of contact economizers and a gas turbine with a combustor fed with steam instead of overstoichiometric air. The thermodynamic investigations show that the new system ensures installation coefficient of energy efficiency up to 2.3%. Through technological and economical calculations, it is proved that by means of the turbine with steam injected combustor, the heat cost can be reduced in our country over 2 times at a higher profitability of the production. Two Bulgarian patents are registered for the system:
State of readiness: installation design, know-how commitment
3. Methods and devices for utilization of heat from thermal power stations
Utilization of the heat of the flue gases from industrial boilers and reduction of the emissions of carbon dioxide and nitrogen oxides. Implemented in Thermal Power Stations Sofia, Schumen and Plovdiv.
State of readiness: final market product, installation design, know-how commitment
4. Highly efficient rectification installations for production of rectified and double rectified ethanol from fermented hydrolysate
In accordance with a framework contract with “Unitech Ltd” the team participated in the building of three rectification installations, two of them put into operation
State of readiness: final market product
5. A new system with five column rectification installation for double epuration and double rectification for production of high quality ethanol from fermented hydrolyzate.
State of readiness: final market product, implementation as a supplement to an existing installation in Selanovci village.
6. Installation for dehydration of ethyl alcohol by means of molecular sieves after the method PSA (pressure swing adsorption)
Installation for dehydration of ethyl alcohol by means of molecular sieves after the method PSA has been developed. Its production capacity is 10000 l/day. The installation is built by “Unitech” Ltd in G. Oriahovitza and is situated on the territory of “Sugar Plants” Company. The investor is “Synthezia” Ltd- Sofia. It is equipped with centralized computer system for control and automation. The main units and apparatuses are made in Bulgaria. The molecular sieves are supplied from abroad.
State of readiness: final market product
7. Installation for methanol regeneration in biodiesel production.
A new type of a column apparatus for regeneration of methanol at glycerin removal in the biodiesel production has been developed. The regenerated methanol is returned back in the production cycle and thus a significant economical effect is realized. Pay-back term – 2 months. The installation is built by “Unitech” Ltd for the needs of Bioenergomash Ltd.
State of readiness: final market product
8. Method for processing of carbon containing materials, Bulgarian Patent № 63594/26.06.2002
A method is developed for obtaining of adsorbents, soot, charcoal-catalysts (metal or metal oxides on carbon), for decrease of the sulfur content in solid fuels, and for increase of the output of liquid products from solid fuels derived from peat to anthracite, oil residuum, wood, cellulose products and wastes, polymers and polymer wastes. The raw materials (directly or after a preliminary manufacturing as milling to size under 10 mm, impregnation with acids, bases or salts), are heated gradually from room temperature to of 1100oС at atmospheric pressure with speed up to 500o/min with constant insufflations with some of the following gases: air, flue gases, carbon dioxide, nitrogen, inert gas and/or addition of water vapor from 0 to 100%, ammonia, or mixture of some of those components. The pyrolytic and activation processes are carried out simultaneously. The solid product rests at end temperature from 1 min. to 48 hours and is cooled after this without access of air in the same media or in inert one.
State of readiness: installation design, know-how commitment.
Papers of the research scientists published in journals with IF (last 5 years)
1. Zhelev, T. K., K.A. Semkov, More Efficient Flue Gas Energy Recovery through Pinch, Journal of Cleaner Production, 12 (2), 165-170, 2004.
2. Zhelev, T. K., K.A. Semkov, More Efficient Flue Gas Energy Recovery through Pinch, Journal of Cleaner Production, 12 (2), 165-170, 2004.
3. Darakchiev R., Inlet and internal devices for packed columns, Chem. Biochem. Eng. Q., 18 (2), 145-153, 2004.
4. Darakchiev R., T.Petrova, S.Darakchiev, Gas distribution in columns with packing Raschig Super-Ring, Chem. Eng. Process., 44 (8), 827-833, 2005.
5. Darakchiev S., T.Petrova, R.Darakchiev, Gas distribution in packed-bed columns with IMTP and Ralu-Flow, Chem. Biochem. Eng. Q., 19 (2), 147-152, 2005
6. Kolev N., S. Nakov, L. Ljutzkanov, D. Kolev, “Effective area of a highly efficient random packing”, Chem. Eng. and Proces. 45, 6 (2006), 429-436.
7. Kolev N., B. Kralev, Packing with stamped horizontal lamellas operating at extremely low liquid loads. I. Hydrodynamics of a single plate. Chem. Eng. Technol. 30, No 1 (2007), 52-58.
8. Dzhonova-Atanasova D., N. Kolev, Sv. Nakov, “Determination of Liquid radial Spreading Coefficient of Some Highly Effective Packings”, Chem. Eng. Technol. 30, Nr.2 (2007), 202-207.
9. Nakov S., N. Kolev, L. Ljutzkanov and D. Kolev, “Comparison of the effective area of some highly effective packings”, Chem. Eng and Processing, 46 (2007), 1385-1390.
10. Kolev N., B. Kralev, E. Razkazova-Velkova“Packing with stamped horizontal lamellas operating at extremely low liquid loads. II. Effective surface area” Chem. Eng. Technol. 31,Nr.1 (2008), 103-109.
11. Kolev D., D. Dzhonova-Atanasova, N. Kolev, “Vertical plates wit inclined capillary grooves for redistribution of liquid phase over the cross-section of packed column. Chem. Eng. and Proces. 47, 01, (2008) 833-841.
12. Kolev N., B. Kralev, E. Razkazova-Velkova, Packing with Stamped Horizontal Lamellas Operating at Extremely Low Liquid Loads II. Effective Surface Area, Chem. Eng. Technol., 31,No 1, (2008) 103-109.
13. Kolev N., B. Kralev, E. Razkazova-Velkova, Packing with stamped horizontal lamellas operating at extremely low liquid loads 3. Pressure drop of the packing. Chem. Eng. Technol., 31,No 4, (2008), 588-593.
14. Darakchiev. S., Kr. Semkov, “Study of modern high effective random packings for ethanol-water rectification”, Chem. Eng. Technol., 31 (7), 1039-1045, 2008.
15. Petrova T., R.Darakchiev, K.Semkov, S.Darakchiev, Estimations of gas flow maldistribution in packed-bed columns, Chem. Eng. Technol., 31 (12), 1723-1729, 2008.
Books
N. Kolev Packed bed columns for absorption, desorption, rectification and direct heat transfer”, Elsevier, (2006), Amsterdam, Boston, Heidelberg, London, New York . (687 pages., 390 fig.)
Staff:
Prof. N. Kolev, PhD, D.Sc.; Prof. R. Daraktschiev, PhD, D.Sc.; Assoc. Prof. Kr. Semkov; Assoc. Prof. Sv. Nakov, PhD; Assoc. Prof. L. Ljuzkanov, PhD; Assist. Prof. D. Dzhonova-Atanasova PhD; Assist. Prof. E. Razkazova-Velkova PhD; Assist. Prof. T. Petrova, PhD.