Kogeneracija i povrat topline u industrijskom postupku

Related to energy requirements for non-cellulose i. e. polyester production as an energy-intensive process, potential saving options are proposed. From the process data, it is evident that unit operations need electric and thermal energy in significant amounts. At the same time, improved energy management could be realized by applying a combined heat and power system (CHP) instead of the usually used process with separate heat and power production. In addition, the boiler flue gases with a sufficiently high outlet temperature could be used for combustion air preheating. Considering industrial process data, a calculation and comparison between the primary energy demand for conventional, CHP system and flue-gas heat recovery is presented. Comparison between separate heat and electricity production i.e. the conventional system with an overall efficiency of 55.6 % and CHP with efficiency of 85 %, shows an absolute efficiency increase of 29.4 %. Using an air preheater for combustion air temperature increasing saves 5.6 % of the fuel and at the same time diminishes thermal pollution because the exhaust flue-gas temperature becomes 77.3 °C instead of 204°C. Conclusively, cogeneration and flue-gas heat recovery presents fuel savings, which also implies economic and environmental benefits.Predložene su mogućnosti uštede energije u industrijskoj proizvodnji poliestera kao energetski intenzivnom procesu. Iz procesnih podataka proizlazi značajna potrošnja električne i toplinske energije u procesnim operacijama. Istodobno, poboljšanje gospodarenja energijom moguće je ostvariti primjenom kogeneracije, tj. zajedničke proizvodnje toplinske i električne energije kao zamjene za uobičajenu odvojenu proizvodnju istih. Nadalje, plinovi izgaranja sa zadovoljavajućom temperaturnom razinom mogu se upotrebljavati radi predgrijavanja zraka za izgaranje. U skladu s procesnim podacima provedeni su proračuni i usporedba potrošnje energije za konvencionalni i kogeneracijski sustav kao i povrat topline dimnih plinova. Komparacija odvojene proizvodnje toplinske i električne energije s učinkovitošću od 55,6 % i kogeneracije s 85 % ukazuje na porast apsolutnog iskorištenja od 29,4 %. Primjenom predgrijača radi povišenja temperature zraka za izgaranje ušteda goriva je 5,6%. Time se istodobno smanjuje toplinsko opterećenje okoliša što rezultira iz sniženja izlazne temperature dimnih plinova od oko 127 °C. Zaključno, kogeneracija i povrat topline dimnih plinova osim sniženja specifične potrošnje energije rezultira ekološkim i gospodarstvenim prednostima

Impact of hybrid system in polyester production

This study represents the evaluation of energy efficiency improvement using combination of natural gas, solar energy and flue gases heat recovery in polyester production. The analyzed energy sources are used for dry saturated steam generation. The energy consumption for combined system on location (φ = 45°49′) with collector field of 23.23 × 103 m2, was investigated. The hybrid system was calculated for four variants: (1) solarized process without flue gases heat recovery, (2) solarized processes with heat contend in flue gases using economizer, (3) solarized processes with heat contend in flue gases using an air preheater and (4) solarized processes with heat contend in flue gases using economizer and air preheater. The best method among presented sources is solution using economizer and the air preheater with natural gas, solar energy and flue gases heat recovery. The natural gas consumption is reduced for 67.82% which indicates that this solution is the optimal one. At the same time the volume of exhaust flue gases is diminished from 4947.1 to 1430.4 $m^3_{\text{FG}}$/h while simultaneously decreasing outlet temperature of 172.85°. Together with considerable energy savings, this hybrid system is sustainable and environmentally acceptable