(589m) Impact of Equipment Cost Estimation Model Selection on the Techno-Economic Analysis of Chemical Plants

Accurate capital cost estimation in the early phases of chemical plant projects are essential for the successful commercialization of chemical technologies. However, existing capital cost estimation models often lack clear selection criteria. Additionally, their accuracy depends heavily on detailed process design information, which is typically limited and uncertain during the initial design stages. To reduce any financial risks of such projects, it is crucial to understand how cost estimates evolve as process design data becomes more defined.

This study investigates the variability of capital cost estimates with respect to both the level of process design detail and the choice of estimation model. Furthermore, we analyze individual equipment cost estimates across models to assess the uncertainty at the unit level. We evaluate 14 capital cost estimation models, including 7 for conceptual design^1-6, 6 for practical design^7-12, and 1 for detailed design. Three case studies are conducted to assess the cost models: a methanol plant based on two-stage methane reforming, an olefin plant that utilizes naphtha and methanol feedstocks, and a hydrogen liquefaction plant. These cases respectively represent processes dominated by catalytic conversion, separation, and cryogenic liquefaction.

Our results reveal significant discrepancies among the estimation models (Figure 1). For methanol and olefin plants, detailed cost estimates are 56-102% and 31-51% higher than practical estimates, and 105-638% and 90-220% higher than conceptual estimates, respectively. Conversely, for hydrogen liquefaction—a process with an unconventional configuration—detailed estimates are 47-66% lower than practical estimates and 89-95% lower than conceptual estimates. Across all models, estimated capital cost variability at a medium plant scale ranges from -92.8% to +240.3% for the methanol plant, -86.1% to +168.0% for the olefin plant, and -46.0% to +656.8% for the hydrogen liquefaction plant. These findings highlight the substantial impact of both estimation model selection and process definition level on early-stage cost projections.

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Figure 1. Range of capital recovery costs by cost estimation models: (a) methanol plant, (b) olefin plant, (c) hydrogen liquefaction plant