Flash Drum

A flash drum can be assimilated to a reactor that has to be sized as a function of the gas flow rate. The diameter of the flash drum is then calculated using the following equation (Turton et al. (1998)):


dj = (- • 600 • Aj)3 (2.18)


where dj is the diameter of the flash drum and Aj is its gas volumetric flow rate. Then, the same method than for the reactor detailed below is applied to calculate the mass of stainless steel and the same correction factor is applied for pressure.

Heat exchanger

Since detailed design data for a shell and tube heat exchanger are available at different sizes and that no datasets are available at different sizes in ecoinvent®, the design data are used to directly calculate the quantities of materials. The heat exchanger is composed by two different materials: stainless steel for the tubes and the shell, and unalloyed steel for the other parts of the heat ex­changer. Equivalences are available for the production of these two materials in ecoinvent®. For each material, a mathematical expression is developed to scale its quantity as a function of the exchange area, based on the available design data. The amount of stainless steel was found to follow a linear scaling law of the type:


where mj is the mass of stainless steel to be calculated mj, ref the one of a reference heat exchanger and Aj is the exchange area. The amount of unalloyed steel was found to follow a similar law to Equation (2.16). The exponent kj, m was estimated to 0.59. These masses are then used to calculate the LCI of the associated equivalent materials, with Equation (2.15).

For the cost estimation of a heat exchanger, it is also necessary to apply a correction factor for the pressure (Turton et al. (1998)). Following the analogy between cost and impact estimation, the correction factor Cj for the pressure
is also applied to the impact scaling, and the correlations from Turton et al.

(1998) are used to correct the emissions of the LCI.

The masses are also used to calculate the impacts due to the transport and disposal. For the disposal, it is assumed that 98% of the steel can be recycled. This is the assumption made by Felder and Dones (2007) for the recycling of metal catalysts. The remaining 2% are assumed to be disposed in sanitary landfill as inert material. The impacts from the assembly and the disassembly are neglected.

Updated: September 27, 2015 — 7:30 am