Marek Velička

Modelling of thermal processes at waste incineration

ABSTRACT The article describes the possibilities of optimization of combustion processes at waste incineration, which require a specific approach in comparison with conventional fuels. The main cause is an instability of thermo-chemical properties of majority of waste. The work defines and evaluates criteria, which are critical for the waste incineration process. The numerical model “Combustion temperature” for optimization of thermal work of the waste incinerator was designed for support of implementation of other measures aimed at increasing the process energy efficiency, and it was verified in practice in real waste incineration plant.

Heat output of the recuperator for preheating natural gas from a mobile container device

The paper describes the methodology for determination of the heat exchanger output for mobile container device designed to supply stationary stations with natural gas. Expansion of the gas in the device is considered in two stages. In the first stage from over-pressure of 22 MPa down to over-pressure of 0.4 MPa and then in the second stage to over-pressure of 2.2 kPa or 170 kPa. The overall temperature drop during gas throttling, which depends not only on the initial and final pressure but also on the temperature, was calculated by numerical integration of the Joule-Thomson differential coefficient. For the throttling temperature between 0 and 55 °C, the total temperature drop in the first stage varies between 53.8 and 67.4 K, and in the second stage then up to 2 K. The heat exchanger output was determined by an iterative process. Smooth supply of 600 m3 of natural gas per hour requires a heat exchanger with an output of approx. 26 kW. Gas combustion micro-turbine consumption is of the order of m3 of natu...

Monitoring and simulation of the unsteady states in continuous casting

Kontinuirno litje obsega termicne, mehanske in kemicne procese, ki tecejo v kompleksnem sistemu, ki vsebuje vrsto elementov, kot so: strjujoca se jeklena žila (gredica), kokila z oscilacijskim mehanizmom, izvlecni mehanizem, vodno hlajenje s podsistemom hladilnih sob, vec kontrolnih podsistemov itd. Zunanji opazovalec lahko vidi proces kot robusten in stabilen, toda v resnici imamo vrsto fluktuacij (nihanj) internih termicnih in mehanskih velicin in kakovosti produkta (nastajajoce konti lite gredice). Raziskave (casovno) nestabilnega obnasanja velicin, kot so: temperaturno polje strjujoce se konti gredice, debelina trdne skorje in metalurska dolžina, so avtorji prispevka izvajali z industrijskim diagnosticnim sistemom (DGS), dopolnjenim s specialno merilno opremo in termicnim numericnim modelom. V clanku avtorji predstavljajo izbrane rezultate analiz, opazovanja in simulacije nestandardni procesnih stanj. Prav tako predstavljajo metode dolocevanja robnih pogojev za numericni model. Diskusija obsega tudi t.i. Leidenfrostov fenomen in njegov vpliv na koeficient prenosa toplote med vodnim hlajenjem s sobami. Za natancno dolocitev vsakokratnih robnih pogojev obstajajo tehnicne omejitve. Zato so v postavljenem modelu uporabljene le zglajene vrednosti v realnem casu in prostoru. Poznavanje trenutnega stanja ves cas spreminjajocega stanja, je predpogoj za doseganje kvalitetne proizvodnje brez napak. Zato je primerno uporabljati termicni numericni model s tekocim (on-line) oz. neposrednim spremljanjem internega stanja na konti livni napravi. Predstavljeni rezultati so tesno povezani z realnimi procesnimi podatki.

Experience with application of reagent to heat transfer surfaces of combustion device

Abstract The formation of deposits on heat exchange surfaces of combustion equipment causes a decrease in heat exchange, a decrease in power, and consequently deterioration in the economic balance of combustion equipment. The technology of French company A. I. T. DRIVEX has been developing and being applied in practice for many decades. Preventive technology is used as a mean reagent periodically injected during operation into the combustion chamber. Part of the application is always pre-prepared project resolving the location of the injection nozzles into the combustion chamber on the flue gas path. The article describes the experimental usage of reagent GEPERSUITE 2200 at the Sermaize refinery in France. The aim of the test is to evaluate the benefits and advantages of applied technology in the boiler refinery in full operation. The results clearly demonstrate that using the reagent GEPERSUITE 2200 is advantageous in terms of economic and technical properties.