Abstract
This study aims to evaluate the environmental and energy effects of the reuse of 1.0 m³ of water in a cooling tower obtained from an oil refinery effluent. An arrangement comprising reverse osmosis (RO), evaporation (EV), and crystallization (CR) was created for water desalination. Six process routes were evaluated; for this purpose, each of them was converted into an specific scenario of analysis: S1: pre-treatment with Ethylenediaminetetraacetic acid (EDTA) + RO + EV (multi-effect distillation) + CR; S2: S1 with pre-treatment by BaSO4; S3: with Ca(OH)2/CaCO3/HCl; S4: S3 with waste heat to supply the thermal demand of EV; S5: S3 with steam recompression in EV; and, S6: S3 with HNO3 in place of HCl. The analysis was carried out by attributional LCA for primary energy demand (PED) and global warming (GW) impacts. The comparison was carried out for a reference flow (RF) of: add 1.0 m3 of reused water to a cooling tower with quality to proper functioning of this equipment. S4 presented the best performance among the analyzed possibilities (PED: 11.9 MJ/RF; and GW: 720 gCO2,eq/RF). However, dependence on other refinery sectors makes it inadvisable as a regular treatment option. Thus, S5 appears as the lowest impact scenario in the series (PED: 17.2 MJ/RF; and GW: 1.24 kgCO2,eq/RF), given the pre-treatment technique of RO-fed effluent, and the exclusive use of steam recompression to meet total EV energy demands. Finally, an intrinsic correlation was identified between RO water recovery efficiency and the accumulated PED and GW impacts on the arrangements that operate with heat and electricity.
Highlights
The oil sector continues to be the main primary energy source, contributing with about 35% of global fuel consumption in 2017 [1]
The results demonstrate the significant influence of the solid waste originating from the treatment and the use of electricity in climate change (CC) impacts, as well as the higher reverse osmosis (RO) efficiency for the quality of the reuse water compared to the ultrafiltration technology
The method applied in this study encompasses six steps: (i) specification of the effluent quality upstream from the industrial wastewater treatment plants (IWTP) in the refinery, and the choice of a process use for which recovered water is intended for; (ii) definition of water recovery strategies and setting the analysis scenarios; (iii) description of the recovery systems in terms of their technological approach and operational conditions, as well as resource consumption and emissions; (iv) designing of mathematical models to represent each system, from the data and information obtained in the previous step; (v) application of the life cycle assessment (LCA) technique to establish an environmental diagnosis for each scenario concerning primary energy demand and global warming; and (vi) perform a critical review of the obtained results
Summary
The oil sector continues to be the main primary energy source, contributing with about 35% of global fuel consumption in 2017 [1]. Due to Brazil’s local reality—of irregular water density and, scarcity of this natural resource in large urban centers at certain times of the year, several regulatory agencies have increased their restrictions on water collection and effluent disposal, in order to mitigate the depletion of the national water network. This scenario has stimulated recent research aimed at increasing the efficiency of effluent treatments and, decrease damage to the extraction and disposal sites of this resource. Water reuse is an approach that has been gaining ground in this area, consisting in treating part, or even, when possible, the whole effluent and subsequently destining it for the supply of industrial or Energies 2019, 12, 326; doi:10.3390/en12020326 www.mdpi.com/journal/energies
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