EKSERGIJSKI STEPEN KORISNOSTI PRI SAGOREVANJU I GASIFIKACIJI BIOMASE

U radu je izvršena uporedna analiza eksergijskih stepena korisnosti pri sagorevanju biomase i gasovitog goriva koje nastaje u procesu istosmerne gasifikacije. Uporedna anliza je pokazala da se viši eksergijski stepen korisnosti ostvaruje sagorevanjem gasovitog goriva, odnosno da termičku transformaciju biomase treba obaviti nakon potpune gasifikacije u reaktorima istosmernog toka, i naknadnim sagorevanjem gasa u spregnutom sistemu istosmerni reaktor – ložište za sagorevanje.Publishe

POVEĆANJE STEPENA KORISNOSTI KOTLA KONTROLOM PROCESA SAGOREVANJA I KORIŠĆENJEM GORNJE TOPLOTNE MOĆI GORIVA

U radu je izvršena analiza korićšenja fizičke toplote gasovitih produkata za povećanje stepena korisnosti kotla i smanjenje emisije štetnih polutanata. Rezultati analize su pokazali da se korišćenjem gornje toplotne moći goriva stepen korisnosti kotla može povećati do 16%.Publishe

PRIMENA KONVEKTIVNOG REKUPERATORA ZA KORIŠĆENJE OTPADNE TOPLOTE STAKLARSKE PEĆI

U radu je prikazano toplotno postrojenje za korišćenje otpadne toplote koja nastaje u procesu proizvodnje staklenih vlakana. Rezultati materijalnog i toplotnog bilansa dobijenih na osnovu eksperimenta pokazuju da se korišćenjem fizilke toplome može smanjiti toplotnog gubitka sadržan u toploti produkata za 63%.Publishe

Gradual combustion of wood logs by the use of preheated air

The tendency to automate operation and minimize human involvement in small-scale biomass boilers has led to an increase in pellet usage. Standardized biomass-derived solid fuels are getting a bigger share in the market. In this battle, traditional firewood is not yet ready to give in. Compared with the standardized fuels, the processing of firewood is cheaper, emits smaller amounts of parasite emissions whereas complete combustion and automation require further development. To achieve these requirements, wood log gasification is a promising intermediate step. The paper aims to design gasification and combustion chambers for a 25-kW wood-log-fired water boiler. For both processes, preheated air is used. Its appropriate distribution and preheating are the main tasks that are realized by the use of a CFD model. In the gasification chamber, the oxidation should take place at least 20 cm before the introduction of the secondary (combustion) air, which is introduced by the use of many openings. Their numbers and positions are envisaged to achieve as complete as possible combustion in a larger area and to divert the flame. A gradual introduction of air in a larger area should reduce carbon monoxide (CO), nitrogen oxides (NOx), and the emissions of volatile organic compounds (VOC), whereas the diversion of the flame should reduce the emissions of particulate matter.http://www.hm.kg.ac.rs/Publishe

Experimental Investigation of an 18-kW-Wood-Log-Fired GasificationBoiler

Compared with other solid biofuels, fuelwood as the oldest biomass fuel source, requires lessprocessing, which results is smaller processing and transportation emissions. Oppositely, the air pollutantemissions are larger due to inefficient combustion control influenced by an uneven size distribution anddifferent moisture content. The previous facts explain why biomass gasification boilers are mainly usedfor steady-state combustion. In this kind of operation, the majority of air pollutant emissions are emittedduring the start-up and stoking processes. In the paper, experimental investigations of an 18-kW-wood-log-gasification boiler are presented. The boiler uses proven technology: two dampers for the control ofgasifying and combustion air, an extractive fan and downdraft gasification. Even this, proven technologycould be substantially improved regarding the efficiency and emission by the use of small modifications.The most creative modifications could be made by the use of: (i) refractory insets in the combustion zoneand (ii) different turbulators and small wings in the convective part of the boiler. The first are used topromote complete combustion and radiant heat transfer whereas the second are used to support convectiveheat transfer and to reduce particulate matter emissions. The examined boiler implemented thesemodifications and fulfilled the most stringent annexes of the standard EN 303-5:2012 regarding theefficiency and pollutant emissions.Publishe

THE MODEL FOR DETERMINATION OF THE TEMPERATURE AND THE GAS COMPOSITION OF BIOMASS GASIFICATION PRODUCTS BY THE USE OF MATERIAL AND ENERGY BALANCES

The paper presents the model for the analytical determination of the temperature and the gas composition of biomass gasification products in downdraft gasification reactors at atmospheric pressure. The temperature and the gas composition were determined by the use of material and energy balances.http://www.hm.kg.ac.rs/Publishe

Energetic and Exergetic Evaluation of 4 Systems for a Rotary Kiln Improvement

The energy balance of a rotary kiln used for calcination of 4400 kg/h of dolomite in a magnesium production company identified the kiln shell (26.35% of the input energy) and exhaust gases (18.95%) as the major sources of heat losses. To increase the efficiency of the kiln, the following systems are analyzed by the use of energy and exergy analysis: (i) system for preheating of the combustion air by heat exchange with the exhaust gas; (ii) system for space and DHW heating in the company by water heating with the exhaust gas sensible heat; (iii) system that consists of a recuperator that use sheat loss from the kiln shell to preheat the combustion air (designatedas iii-a) and the system given in (ii); and (iv) system that consists of (iii-a) and an cogeneration system that uses organic Rankine cycles upplied with heat by heat exchange with the exhaust gas. The system (ii) is the optimal solution by economic criteria because the company uses relatively expensive heavy fuel oil for space heating, where as exergetically, the most efficientis the the system (iv), which enables the kiln to have the exergetic efficiency of 36.02%.https://www.hm.kg.ac.rs/documents/Proceedings2014.pdfPublishe

Radiant recuperator modeling and design

Recuperators are frequently used in glass production and metallurgical processes to preheat combustion air by heat exchange with high temperature flue gases. Mass and energy balances of a 15 m high, concurrent radiant recuperator used in a glass fiber production process are given. The balances are used: For validation of a cell modeling method that predicts the performance of different recuperator designs, and for finding a simple solution to improve the existing recuperator. Three possible solutions are analyzed: To use the existing recuperator as a countercurrent one, to add an extra cylinder over the existing construction, and to make a system that consists of a central pipe and two concentric annular ducts. In the latter, two air streams flow in opposite directions, whereas air in the inner annular passage flows concurrently or countercurrently to flue gases. Compared with the concurrent recuperator, the countercurrent has only one drawback: The interface temperature is higher at the bottom. The advantages are: Lower interface temperature at the top where the material is under maximal load, higher efficiency, and smaller pressure drop. Both concurrent and countercurrent double pipe-in-pipe systems are only slightly more efficient than pure concurrent and countercurrent recuperators, respectively. Their advantages are smaller interface temperatures whereas the disadvantages are their costs and pressure drops. To implement these solutions, the average velocities should be: For flue gas around 5 m/s, for air in the first passage less than 2 m/s, and for air in the second passage more than 25 m/s

IMPROVING POWER PRODUCTION OF A SMALL HYDROPOWER PLANT

У раду је за две постојеће мале хидроелектране (МХЕ) које раде у спрегнутом систему моделом техноекономске оптимизације дефинисано техничко решење које омогућава повећање производности електричне енергије при протоцима воде који су мањи од минималног протока за који произвођач опреме гарантује доњу границу степена корисности турбине. У обе МХЕ је уграђена по једна турбина са унакрсним током (crossflow) исте снаге, 1475 kW. Експериментално је у експлоатационим условима за турбину у узводној МХЕ одређена зависност протока воде и степена корисности турбине, а резултати су показали изражени пад степена корисности при протоцима воде мањим од минимално препоручених протока произвођача турбине. Уградња друге турбине у низводној МХЕ и реконструкцијом изливног канала у узводној МХЕ омогућила би коришћење укупног расположивог бруто пада обе електране, и повећала годишњу производњу електричне енергије при протоцима који су мањи од минимално препорученог за 116 %.http://e2016.drustvo-termicara.com/Publishe

Risk Analysis Methods for Small Hydro Power Plants in Creating Insurance Policy

Small Hydro Power Plants provide more diversity in terms of financing projects, location selection, ownership, its applications as well as insurance methods, comparing to the Conventional Hydro Power Plants. Electricity produced by small hydro power plants could be used to improve energy efficiency of different production facilities, domestic and public lighting and other applications. However, those energy objects are exposed to the variety of risks that should be taken into consideration in different ph ases of objects’ construction, operation and maintenance. Understanding of those risks is crucial for undertaking of different techno-economic analysis, as well as establishing of the insurance policy for those power plants. The approaches used to create insurance policy for Small Hydro Power Plants in certain countries depend of the technology applied and development level of the country and will be provided in this paper.Publishe