CASE STUDY 2: PROCESS SCHEDULING AND DEBOTTLENECKING FOR A MULTIPRODUCT BIOTECH FACILITY
Figure 7. Equipment-occupancy chart for a multiproduct biotech facility. Rows denote various steps of each unit operation.
The columns denote the process time in days.
For this case study, process scheduling and debottlenecking was conducted for a biotech facility manufacturing four therapeutic
products to minimize the required number of buffer preparation tanks. The harvest for the second product is generated as a
byproduct from the first process. For the third product, harvest was generated from the first or second process. Similarly,
the fourth product was generated from the first, second, or third process.
Figure 8. Tentative number of tanks required. Rows denote various tank sizes. The columns denote the process time in days.
Figure 7 shows the overall scheduling for the processes that require buffers. Using the available data on the volume and composition
of buffer required for each step and the scheduling of each step, the requirement of buffer per shift and the total buffer
requirement were calculated. Next, the tank requirement scheme was developed for each shift based on the volume of buffer
to be prepared. All the buffers are prepared only one day before to avoid storage and stability issues. The scheme is shown
in Figure 8. Next, tank usage was scheduled by maximizing the use of each tank by vertically shifting rows (e.g., we can use
a 600-L tank for the preparation of 400-L buffer, if it is available). If buffer stability is not a problem, horizontal shifting
can be performed to minimize the number of tanks and to level the daily workload. The optimized tank usage scheme is shown
in Figure 9. Data are also shown in Table 2.
Figure 9. Optimized tank requirements. Rows denote various tank sizes. The columns denote the process time in days.
The approach illustrated in this second case study is simple and effective; however, we did not consider the actual buffer
preparation time in our analysis and instead approximated it using the average time for buffer preparation, which varied from
2 to 3 h. Tank wash and media transfer time was accounted for in the average time only. Although, this made the analysis quite
simple and accurate for application here, alterations should be made for cases where this approximation may not be valid.
Table 2. Requirements for the second case study
This case study shows the application of the suggested method for identifying the optimized number of buffer and media preparation
tanks for a multiproduct biotech process. The above numbers of tanks are proposed for preparing a total of 48,235 L of 25
different buffers per week using only eight tanks with a total volume of 5,750 L.