Mirjana Stamenić

Energy audit as a tool for improving overal energy efficiency in Serbian industrial sector

The paper presents characteristics of energy consumption in industrial sector of Serbia, the methodology and results of energy audits (EA) performed in industrial sites and potentials for energy efficiency (EE) improvements. The present state of industrial energy in Serbia could be characterized by significant technological out-of-date, low EE and low level of environmental protection. Presented analysis of the results of conducted EAs in selected industrial companies in previous period has shown the significant potentials for EE improvements in Serbian industrial sector (upgrading or replacement of equipment in the industrial energy sources and processes, introduction of energy management, improvement of steam supply and condensate return systems, the waste heat utilization, introduction of EE technology, improvement of EE in electrical equipment, usage of waste materials etc).

Size distribution of agglomerates of milk powder in wet granulation process in a vibro-fluidized bed

Results of experiments on the influence of technological parameters (intensity of vibration, granulation of the liquid feed, temperature of fluidization agent) on the change of size distribution, as well as mass mean diameter of the milk powder particles subjected to the wet granulation process (agglomeration) in a vibro-fluidized bed granulator are shown in this paper. Using water as a granulation liquid and air as a fluidization agent, it was found that mass mean diameter increases with increase of water feed, intensity of vibration, and decrease of air temperature. Increasing the intensity of vibration and decreasing the air temperature, primarily induces the increase of the dimensions of the initial nuclei. This can be explained on the basis of different influences that these changes (velocity of particle motion, intensity of particle collision, drying rate) have on the coalescence of particles with smaller and/or bigger dimensions.

Energy management system for energy efficiency improvement in the industrial sector of the republic of Serbia

Main primary energy sources in Serbia are coal, oil and natural gas, oil shale and renewable energy sources. The share of high quality primary energy sources (oil and natural gas) is less than 1% of total geological reserves, while the rest of 99% consists of different types of coal, with highest share of lignite - over 95%. Estimated technically available renewable energy sources potential in Serbia is 5.65 Mtoe, where 1.054 Mtoe of biomass and 0.909 Mtoe of hidro-power are already used. Speaking of energy efficiency in final energy consumption sectors of the Republic of Serbia holds unenviable position comparing to EU countries. Since 2000 there is series of strategic and legal documents that are adopted and they are governing the operation of energy sector as well as implementation of energy policy at state level. The Law on energy efficiency was adopted in March 2013. It regulates implementation of energy management system within industrial sector, on the local level (cities and municipalities) as well as in public buildings sector. The purpose of secondary legislative is to define, in more details, terms for obtaining status of designated company within the system for energy management in industrial sector and in public companies, training programs for energy managers, as well as method of appointing energy managers in designated companies.

Results of experimental research on parameters that determine stable operating limits of ceramic burner with packed bed of uniform spheres for combustion of low calorific gaseous fuels

The research presented in this paper focuses on parameters that determine stable operating limits of porous burner. The experimental research was carried out on laboratory installation consisting of ceramic cylinder filled with packed bed of Al2O3 spheres. Gaseous fuel is prepared by mixing the compressed natural gas (CNG) and nitrogen (N2) in defined ratio, depending on set heating value of the inlet gaseous fuel. Experimental program included combustion of low calorific gaseous fuel (7.5 to 15 MJ/m3) within porous burner, where inlet power ranged between 2 and 4 kW. Total number of experimental sets in experimental study was 16, where seven of them were considered as stable. Results of experimental research are presented and discussed within this paper.

Potentials for reducing primary energy consumption through energy audit in the packaging paper factory

Energy audit is a primary step towards a more rational use of primary energy sources in the energy-intensive process such as the production of packaging paper. By the adoption of the Law on efficient use of energy in 2013, energy audits have become mandatory for all industrial companies in Serbia. This paper presents the methodology and results of the one-day energy audit which was conducted in the Paper Factory - Belgrade (FHB). The measures to increase energy efficiency of the production process, together with the quantification of the savings in the primary energy consumption, are proposed based on the results of the study.

Experimental research of pressure drop in packed beds of monosized spheres a novel correlation for pressure drop calculation

Flow through packed beds of spheres is a complex phenomenon and it has been extensively studied. Although, there is many different correlations there is still no reliable universal equation for prediction of pressure drop. The paper presents the results of experimental research of pressure drop in packed bed of monosized spheres of three different diameters, 8, 11 and 13 mm set within cylindrical vessel of diameter dk = 74 mm, and two different heights of packed bed hs = 300 and 400 mm. It has been proposed modification of widely used Ergun’s equation in the form of fp = [150+1.3×(Rep/(1-e))]×(1-e)2/(e3×Rep) and new correlation fp = 1/[(27.4-25700×dh)/Rep+0.545+6.85×dh] for pressure drop calculation in sim- ple and convenient form for hand and computer calculations. For total number of 362 experimental runs the correlation ratio of the modified Ergun’s relation was CR = 99.3%, and standard deviation SD = 12.2%, while novel relation has CR = 93.7% and SD = 5.4%.

Experimental study on the efficiency of pulverized coal-fired steam boiler

The results of experimental investigation of pulverized coal combustion process with the aim to improve energy efficiency of an industrial steam boiler are presented in the paper. The investigation included measurement of combustion process parameters in four typical operating conditions, from minimum to maximum steam boiler load, and visualization of combustion process by using the camera with thermal imaging sensor. Several organizational and technical measures to improve energy efficiency of the industrial steam boiler are proposed and discussed in the paper. The measures are evaluated in terms of a possible reduction in the coal consumption and CO2 emissions.

Effect of small deviation of incident angle on thermal performance of parabolic-trough solar collector

The paper analyzes the effect of small deviation of incident angle relative to the focal plane on thermal performance of parabolic-trough solar collector. Decrease of solar collector thermal output is presented in form of coefficient of performance i.e. function of the incident angle deviation. In solar collector operation mode, working fluid (e.g. water) can become overheated. In that case, decreasing the thermal output would influence temperature drop of working fluid. Rotation of a parabola for a small angle relative to the focal plane will decrease the output thermal power of the solar collector. This analysis contributes to calculate deviation of incident angle relative to the focal plane in order to achieve the given thermal output for defined input parameters - collector type, local and real conditions (i.e. Sun position, orientation, time and date). In this paper, two-dimensional analytic geometry was used as a basic methodology for calculations and simulations.

Airflow measurements and mass and heat balance in a cardboard mill hall to approach energy efficiency

The results of field measurements conducted in Umka Cardboard Mill hall are presented in the paper. The points of interest were air temperature and humidity distribution inside the hall as well as the temperatures of the cardboard machine surfaces and inner walls of the hall. Temperature, humidity and velocity of air at supply-air openings were also measured. Based on the results material and heat balance of the hall was calculated and discussed. The aims of the study were to evaluate the thermodynamic properties and waste heat potentials of the air extracted from the hall by mechanical ventilation system.