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Exergetic, environmental and economic assessment of sugarcane first-generation biorefineries

Silva Ortiz Pablo A., Flórez-Orrego Daniel, Oliveira, Jr Silvio de, Maréchal François, Maciel Filho Rubens

Journal of Power Technologies

2019

Vol. 99, nr 2

67--81

First generation ethanol (1G) contributes to the majority of the ethanol produced worldwide, predominantly centered on corn and sugarcane. Nevertheless, several issues are regularly highlighted concerning the long-term sustainability of this technology, including its intensive water and land use, potential contamination of soils through the distillation residues, as well as the balance between fuel and food crops. Accordingly, in this study, a process design approach for biomass to ethanol production (1G ethanol technology) from sugarcane was performed by using Aspen Plus® software, based on the autonomous distillery (AUT, ethanol production) and the annexed plant (ANX, joint ethanol and sugar production) configurations. In addition, a performance comparison in respect to the exergy efficiency and the irreversibility as quality indicators of the conversion processes is carried out to identify potential improvements in the production facilities. Hence, the shortcomings of the techno-economic assessment of ethanol production can be overcome by using exergy efficiency as a suitable indicator for process performance. Moreover, the technical/sustainability aspects related to the process design of the sugarcane biorefineries are discussed in light of the renewability exergy index (λ). In general, the ANX plant has a saving in the process irreversibility rate of about 6%, whereas the average unitary exergy cost is 10% lower (AUEC= 2.41 kJ/kJ), in contrast to the AUT distillery. Moreover, a techno-economic analysis was carried out to assess the annexed plant and the autonomous distillery systems, considering the estimated capital expenditure. The results indicated that the ANX biorefinery has higher capex than the AUT distillery. It is noted that the higher investments are associated with sugarcane reception, ethanol production (juice extraction) and the combined heat and power sub-systems. Concerning system performance, the ANX plant presented a better overall exergy efficiency, with 41.39 %. Although this multi-criteria analysis is applied to 1G ethanol technology; it may be well-matched for various biorefineries/bioprocesses as a methodology to support decision-making as concerns potential improvement, well ahead of detailed process design.

Warunki techniczne opłacalności systemów kogeneracyjnych

Śnieżyk R.

Rynek Energii

2006

nr 6

13-15

Ostatnio w Polsce modne są relatywnie małe systemy kogeneracyjne. Układy takie budowane są w wielu miejscach niezależnie, od warunków technicznych oraz względów ekonomicznych. Omówiono podstawowe urządzenia układów skojarzonych z obiegiem parowym, turbiną gazową oraz blokiem siłowniano-ciepłowniczym wraz z oceną ich przydatności w różnych warunkach technicznych i ekonomicznych. Przedstawiono przykład układu skojarzonego, w którym niewłaściwy dobór wielkości urządzeń spowodował nieopłacalną eksploatację systemu ciepłowniczego. Omówi ono rozwiązanie zastosowane przez Polish Energy Partners S.A. we Wrocławiu-Zakrzowie na terenie POLAR S.A. Wskazano skutki niewłaściwego zbilansowania potrzeb cieplnych i energii elektrycznej. Wzrost cen energii cieplnej spowodował rezygnację dużej części odbiorców ciepła z zasilania z elektrociepłowni z turbiną gazową. Przedstawiono problemy techniczne z prowadzeniem systemu ciepłowniczego spowodowane skokami ciśnienia w sieci ciepłowniczej wynikające z niewłaściwej wielkości urządzeń. Te skoki ciśnienia mogły być przyczyną kilku awarii sieci ciepłowniczej, które wystąpiły po uruchomieniu tego źródła ciepła. Na podstawie koncepcji opracowanej przez Autora dla Słupska wskazano najlepsze rozwiązane. We wnioskach przedstawiono propozycje wymiarowania układów skojarzonych w zależności od potrzeb cieplnych.

Recently, small combined heat and power systems have been popular in Poland. These systems are installed in many places in the country disregarding technical requirements or economic conditions. The present paper presents basic cogeneration system equipment combined with the steam loop, gas turbine and gas engine as well as the evaluation of their usability under various technical and economic requirements. A typical scheme of a combined heat and power system was presented where the wrong sizing of the equipment caused unprofitable use of district heating system. The paper also discusses the system used by the Polish Energy Partners S.A. company in Wroclaw - Zakrzow at the POLAR area. The results of incorrect balancing of the heat and energy demand are shown as well. The increase of heat energy prices made a large number of customers stop using heat energy supplied by gas turbine plants . The paper presents technical problems related to running district heating system resulting from rapidly increasing pressure within the district heating network which was caused by wrong sizing of the equipment. These rapid fluctuations of pressure may have caused several breakdowns of the district heating network which occurred after the start-up of this heat source. Based on the concept designed by the Author for the town of Słupsk the best solution was indicated. In the conclusions some proposals for the sizing of combined heat and power systems were presented depending on the heat loads.