Analysis Types
ChemProject provides a wide range of criteria for the assessment of syntheses, branches and steps, suitable for comparisons, identification of optimization needs, and as metrics for optimization progress.
Minimal Volume-Time Output (VTOmin)
The standard Volume-Time Output (VTO) parameter reflects the impact of a chemical process on the cost of occupancy of a specific production infrastructure with known vessel volumes. Since such production equipment assignments rarely are known at the synthesis selection stage, ChemBytes introduces a VTO variant which doesn't require any specific apparatus assignments - the VTOmin parameter. The idea is simple: Instead of utilizing the available reactor volumes as the calculation parameter (resulting in various fill levels), only the actually required unit operation volumes are taken as the calculation parameter.
VTOmin = operation max. volumes total [m3] * operating times total [h] / product [kg]
This corresponds to the lowest possible VTO value of the process, where always a reactor fill-level of 100% is reached and therefore always just one run per step is required. This best-case scenario effectively decouples the quality of the process from the availability of infrastructure.
Implementation: VTOmin values are calculated at the step, branch and synthesis levels and refer to their respective product amounts. The operation max. volume is approximated by the sum of the involved material weights and volumes, so best specify solvents in volume (not weight) units. If a unit operation has no assigned volume (e.g. drying), its operating time still contributes to the total time. Transferred materials as well as the volume effect of volume exchanges (extractions) are taken into account. – The VTOmin value remains unspecified if some operating times are missing at the current level. In such cases ChemProject displays an info area providing a convenient interface for entering the missing operating times.
The PMI provides reflects the material efficiency of a process. It is calculated as follows:
PMI = total weights of added materials [kg] / final product [kg]
For the determination of the total weight of the involved materials, volume amounts are converted to weights, intermediates and branch imports are included into the material total, while transferred materials are ignored. PMI values are calculated at the step, branch and synthesis levels and refer to their respective product amounts.
Since PMI calculations strictly require that all materials are taken as weights, ChemProject only calculates the value if the densities of all materials specified as volumes are present. If some densities are missing, an info area providing a convenient interface for entering the missing densities is displayed.
Please note that the PMI parameter does not provide direct information on the infrastructural impact of a process, like vessel occupancy and operating times. Consider to utilize VTOmin parameter if such information is required.
The volume factor provides metrics for the volume efficiency of a synthetic step. It is similar to the PMI parameter above, but takes the approximated material volumes instead of weights as the calculation argument:
Volume Factor = total added materials [kg; L] / step product [kg]
The total volume is approximated by adding up material volumes and weights. When solvents are specified in volume units, the Volume Factor provides better volume approximations than PMI; also, no input of missing densities is required. If all materials are specified as weights, then the Volume Factor value is the same as the PMI value.
Operation Volume Intensity (OVI)
This parameter reflects the volume efficiency of a unit operation. It is defined as the maximum required unit operation volume (see Maximum Volume) per kg step product:
OVI = max. required volume [kg; L] / step product [kg]
The maximum volume approximates the volume by adding up material volumes and weights. It therefore provides best results when solvents are specified as volumes instead of weights.
This parameter provides metrics for the assessment of the disposal and/or recycling costs of the utilized materials (see Disposal Assessment). Considering that recycling costs often may exceed the purchase costs of e.g. solvents, this is a fundamental assessment. ChemProject allows the assignment of a waste category to each material, ranging from category 0 (default) to a maximum of category 5 (extremely costly disposal/recycling). The Disposal Impact value combines these assignments into a single, weighted parameter, where catxVol is the total of all materials of waste category x.
Disposal Impact = (cat0Vol + 2*cat1Vol + 3*cat2Vol+ 4*cat3Vol +5*cat4Vol) / totalVol
A synthesis with a low disposal impact will cause much smaller disposal and/or recycling costs than a synthesis with a high one.
This parameter allows the location of steps having the highest potential on synthesis cost reduction upon yield improvement. The background is, that increasing the yield of the lowest yielding steps not necessarily has the highest impact on overall costs. This impact depends on several factors, such as the location of the step in the synthesis, the accumulated intermediate costs, the added material costs, etc. - The Yield Impact analysis simulates an individual yield increase of each step by an arbitrary amount of 20%, e.g. from 70% to 90%. The resulting synthesis material cost reductions (in percent) are presented in the chart in descending order of impact.
This parameter approximates the maximum required volume of a unit operation. It is in part determined by the total of all materials either added or transferred from the previous unit operation. Additionally, if more than one exchange volume is specified, e.g. when an organic phase is extracted with multiple portions of an aqueous phase which is removed after each extraction, then simply adding up these materials would result in a too high volume. Instead, only the largest of these exchange volumes is added to the total (see Volume Handling ).
MaxVol = added materials total + transferred materials total + largest exchange volume (per unit operation)
The sum of materials does not distinguish between material weights and volumes and therefore is an approximation of the maximum volume. It works best if the solvents are specified as volumes, not weights. If exact volume data are required, it is recommended to utilize the Observed Volume parameter instead.
The calculation of the volume resulting from the dissolution of a solid material in a solvent is non-trivial. Volume calculations therefore usually resort to the approximation of the sum of volumes weights towards a total volume.
However, ChemProject offers a simple way for the calculation of non-approximated volumes. By marking the maximum and minimum fill levels of the glass vessel in which a unit operation takes place in lab scale, the corresponding observed volumes can be determined. These observed max. and min. unit operation volumes can be entered in the Source Data section of ChemProject and will be scaled to fit the calculated synthesis scale. See Volume Handling for more details.
This is the simple sum of all materials added to a unit operation. Transferred volumes are ignored, as well as the volume effects of exchange volumes. Material weights and volumes are not distinguished in the total.
The overall time the unit operation equipment is occupied per step. It is calculated by multiplying the operation time by the required runs per step.
Indicates the human resources required for running a unit operation. It is calculated by multiplying the Equipment Occupancy Time (see above) by the number of required operators.