Thermodynamic analysis of a petroleum volatile organic compounds (VOCs) condensation recovery system combined with mixed-refrigerant refrigeration

Thermodynamic analysis of a volatile organic compounds (VOCs) condensation recovery system combined with mixed-refrigerant J-T (MRJT) refrigeration is illustrated in this paper, which provides an effective and economical choice for petroleum plants. VOCs is compressed, cooled by its recuperation process and separated in two simple rectification columns with 3-5 stages. The cooling powers for condensers at column top are provided by a high efficiency dual MRJT refrigerator at 100 K and 232 K, respectively. The cooling and separation characteristics of petroleum VOCs are also analyzed comprehensively. It is indicated that most of VOCs condensation load locates in high temperature region (>= 235 K approximately). It might be feasible to cool VOCs from 235 K to 110 K by cold purified air through recuperation. For a typical petroleum VOCs, non-methane hydrocarbon residual of 56 mg Nm(-3) is achieved with specific power consumption (SPC) of 0.1289 kWh Nm(-3), free of additional purifying units. According to the analysis on the effects of variable VOCs composition and pressure, the cooing loads of top condensers are close related to the performance of VOCs recuperation. C1 and C2 are key components to enhance recuperation at low temperatures and reduce SPC. Exceed C3 could enlarge cold stage condenser load and SPC due degraded cold stage recuperation; while exceed C4-C6 could reduce condenser loads and SPC. Higher VOCs pressure could also decrease SPC. (C) 2020 Elsevier Ltd and IIR. All rights reserved.