Yes / In all industrial petrochemical plants and refineries, the furnace is the source of heat resulting from fuel combustion with air. The model-based furnace simulation is considered one of the efficient methods help to reduce the energy loss and maintain fixed refinery revenues, conserving energy, and finally reducing external fuel consumption and total fuel cost. In this paper, a model-based simulation is carried out for a natural air draught industrial scale furnace related to Liquified Petroleum Gas (LPG) production plant in Libya to thoroughly investigate the most responsible factors in lowering the furnace butane exit temperature, which is supposed to be two degrees Fahrenheit higher than inlet temperature. Therefore, to resolve this industrial problem, Aspen Hysys V10, coupling with EDR (exchanger design and rating) is used to carry out rigorous model-based simulation. This is specifically used to assess the impact of heat loss from inside the firebox to the surrounding medium and heat loss from the furnace stack and walls, besides the effect of excess air on the furnace efficiency. Furthermore, this research intends to verify whether the operating conditions, such as furnace tubes inlet flow rate, temperature and pumping pressure, are conforming to the upstream process design specifications or need to be adjusted. The results confirm that increasing furnace outlet temperature two degrees Fahrenheit from off specification 190 °F instead of 184 °F is successfully achieved by decreasing upstream stream flowrate 25% below the operating value and cutback excess air gradually until 20%. Also, the results clarify the necessity of increasing the flue gas temperature by 7% over design condition, to gain a significant reduction of heat loss of 31.6% and reach as low as 35.5 MBtu/hr. This improvement is achieved using optimum operating conditions of an excess air of 20%, and flue gas oxygen content of 3.3% delivered to stack. Accordingly, the furnace efficiency has been increased by 18% to hit 58.9%. Furthermore, the heat loss from the furnace walls can be also reduced by 68% from 5.41 MBtu/hr to 1.7 MBtu/hr by increasing the refractory wall thickness to 6 in., which entails an increase in the furnace efficiency by 3.66% to reach 58.96%. Decreasing the heat loss fraction through the refractory wall, pip doors, expansion windows and refractory hair cracks would also increase the efficiency by 21% to reach a high of 59.7%. Accordingly, a significant reduction in daily fuel consumption is observed, which costs 1.7 M$ per year. The outcomes of this research clearly show the potential of reducing the operation and maintenance costs significantly.

The main aim of the thesis is to evaluete properties of a simplified thermal calculation of the direct fired heater published in the journal Applied Energy at 2010 and its application to specific industrial cases. At first, general issues of process heaters are talk over. Second, calculation model in cited article is briefly introduced. After that, custom computational model at program Maple is created in accordance with published article. Subsequently, the model is applied to the existing process furnaces in the form of a check calculation. An integral part of the work is also a detailed discussion of the results obtained.

Tiriamojo darbo tikslas – ištirti spindulinio dujinio šildytuvo darbo režimo parametrus. Dujinis spindulinis šildymas yra ekonomiška, nekenksminga ir labai paprasta šildymo sistema. Tokia šildymo sistema naudojama patalpose su blogu sandarumu, taip pat kur yra dideli aukščiai. Tirtas ,,U‘‘ formos spindulinis dujinis šildytuvas. Tyrinėtos šiluminės savybės spindulinio šildytuvo paviršiaus, kaitimo savybės vamzdžio skirtinguose šildytuvo pjūviuose, vamzdžio įšilimo trukmė, galia šildytuvo, dujų sunaudotas kiekis. Spindulinis dujinis šildymas Lietuvoje mažai ištirtas. / Purpose of work: the research working mode of processed „U“ form radial gas–fired heater. The gas-fired heating is an economical, ecological, harmless and very simply heating system. Such heating system is used in the accommodations with high sealing and there are big height. Were processeded „U“ form radial gas–fired heater. Were explored heating dynamics of radial heater culvert surface, dynamics changing of culvert temperature in characteristic heater operating length section, duration till culvert heats to operating temperature, capacity of processed heater, the gas amount. The radial heating in Lithuanian is few processed and very heavy to do concrete conclusion.