# Product Mapping & Facility Fit in Multipurpose API Plants: Campaign Sizing, Equipment Train Matrix & Changeover Optimization

# Executive Summary & Industrial Context

In commercial Active Pharmaceutical Ingredient (API) and fine chemical manufacturing, constructing dedicated production facilities for every single molecule is economically unviable. Modern bulk drug manufacturing relies on Multipurpose API Manufacturing Facilities—flexible multi-equipment suites capable of producing dozens of distinct APIs across sequential campaigns.

However, running different synthetic routes in shared equipment introduces complex engineering challenges:

Batch Charging Frequency ( $f_{charge}$ ) & Batch Cycle Time (BCT): Aligning raw material charging intervals with controlling unit operation bottlenecks to maximize annual plant throughput without liquid hold-up.
Process Equipment Capability & MOC Matrix: Matching chemical environment severity against Glass-Lined Steel (GLS), Stainless Steel (SS316L), and Hastelloy C-22 across 10 major unit operations.
Equipment Train Fitting & Volume Matching: Enforcing the $60\% - 85\%$ volumetric occupancy rule for reaction, crystallization, filtration, and drying steps.
Campaign Turnaround Optimization: Scheduling cleaning wash windows and line changeovers between multi-product campaigns.

This engineering guide provides an authoritative technical framework for conducting Product Mapping & Facility Fit Analysis, featuring deep mathematical formulations for Batch Cycle Time (BCT), a comprehensive 10-Equipment Process Capability Matrix, and an annual operational mapping table for 5 commercial APIs.

# 1. Batch Cycle Time (BCT) & Batch Charging Frequency ( $f_{charge}$ )

In a multipurpose batch plant, overall facility productivity is governed not by average reaction rates, but by the Controlling Unit Operation (The Bottleneck Step).

# 1.1 Mathematical Definition of Batch Cycle Time (BCT)

The total un-staggered processing time for a single batch ( $BCT_{single}$ ) across $k$ sequential unit operations is the direct sum of individual operation durations ( $t_i$ ):

BCT_{single} = \sum_{i=1}^{k} t_i = t_{reaction} + t_{crystallization} + t_{filtration} + t_{drying} + t_{micronization}

However, when running continuous campaigns, charging new batches into the primary reactor ( $R-101$ ) every $BCT_{single}$ hours results in severe plant under-utilization.

The Controlling Batch Cycle Time ( $BCT_{controlling}$ ) is defined by the longest single unit operation in the equipment train:

BCT_{controlling} = \max \left( t_1, t_2, t_3, \dots, t_k \right)

# 1.2 Batch Charging Frequency ( $f_{charge}$ ) & Charging Interval ( $\Delta t_{charge}$ )

To achieve maximum volumetric throughput without causing liquid accumulation or vessel overflow in intermediate aging tanks ( $CR-201$ ), raw material charges into the primary reactor must be spaced by the Minimum Charging Interval ( $\Delta t_{charge}$ ):

\Delta t_{charge} = BCT_{controlling}

The Optimal Batch Charging Frequency ( $f_{charge}$ ) (batches per day) is:

f_{charge} = \frac{24 \text{ Hours/Day}}{\Delta t_{charge}} = \frac{24}{\max(t_i)}

# 1.3 Total Campaign Completion Time Equation ( $T_{campaign}$ )

For a planned campaign of $N_{batch}$ batches, including a fixed changeover wash window ( $t_{wash}$ ), total campaign turnaround time ( $T_{campaign}$ ) in hours is:

T_{campaign} = \left( (N_{batch} - 1) \cdot \Delta t_{charge} \right) + BCT_{single} + t_{wash}

  +-----------------------------------------------------------------------------------------+
  | STAGGERED BATCH CHARGING FREQUENCY (f_charge) TIMELINE                                  |
  +-----------------------------------------------------------------------------------------+
  |                                                                                         |
  |  Batch 1:  [ R-101 (8h) ] ──► [ CR-201 (6h) ] ──► [ ANFD (5h) ] ──► [ RCVD Drying (16h) ]  |
  |  Batch 2:         [ R-101 (8h) ] ──► [ CR-201 (6h) ] ──► [ ANFD (5h) ] ──► [ RCVD (16h) ] |
  |                   ▲                                                                     |
  |                   │                                                                     |
  |             Charge #2 at t = 16h (Matching RCVD Drying Bottleneck Δt_charge = 16h)     |
  |                                                                                         |
  +-----------------------------------------------------------------------------------------+

# 1.4 Case Study: Bottleneck Impact on Product A

Consider Product A (Atorvastatin Intermediate) unit operations:

$t_{reaction} (R-101) = 8.0 \text{ Hours}$
$t_{crystallization} (CR-201) = 6.0 \text{ Hours}$
$t_{filtration} (ANFD-301) = 5.0 \text{ Hours}$
$t_{drying} (RCVD-401) = 16.0 \text{ Hours}$ (Bottleneck)
$t_{micronization} (MIL-501) = 3.0 \text{ Hours}$
Single Batch Duration ( $BCT_{single}$ ): $8 + 6 + 5 + 16 + 3 = 38.0 \text{ Hours}$
Controlling Cycle Time ( $BCT_{controlling}$ ): $16.0 \text{ Hours}$
Optimal Charging Interval ( $\Delta t_{charge}$ ): $16.0 \text{ Hours}$
Charging Frequency ( $f_{charge}$ ): $1.50 \text{ Batches / Day}$

If batches are charged every $8.0 \text{ hours}$ (the reaction time) instead of $16.0 \text{ hours}$ , Batch #2 will arrive at $RCVD-401$ while Batch #1 is still drying, causing $100\%$ liquid hold-up in CR-201 and halting production. By enforcing $\Delta t_{charge} = 16.0 \text{ hours}$ , annual output increases from 63 batches to 270 batches (+428% gain).

# 2. Process Equipment Capability Matrix (10 Units vs 5 Products)

Below is the technical specification matrix detailing the 10 Process Equipments installed in the multipurpose facility, defining MOC, volume range, operating pressure/temperature envelopes, agitator styles, and supported API product campaigns:

Equipment Tag	Description & Module	Metallurgy (MOC)	Nominal Capacity	Working Volume (60-85%)	Temp Envelope	Pressure Rating	Agitator / Drive Type	Compatible Products
R-101	Primary Glass-Lined Reactor	Glass-Lined (GLS)	6,300 L	3,780 – 5,355 L	-20 °C to +200 °C	-1 to +6 bar	Retreat Curve Impeller (RCI)	Product A, Product E
R-102	Secondary SS Reaction Vessel	Stainless Steel 316L	5,000 L	3,000 – 4,250 L	-30 °C to +180 °C	-1 to +4 bar	Hydrofoil Turbofoil Agitator	Product B, Product C
R-103	Corrosive Chemistry Reactor	Hastelloy C-22	8,000 L	4,800 – 6,800 L	-40 °C to +220 °C	-1 to +10 bar	Pitch Blade Turbine (PBT)	Product D, Product E
R-104	High-Pressure Hydrogenator	SS316L Heavy Wall	5,000 L	3,000 – 4,250 L	-10 °C to +150 °C	0 to +20 bar	Gas-Inducing Hollow Shaft	Product C (Pregabalin)
CR-201	Crystallizer & Aging Tank	Glass-Lined (GLS)	6,300 L	3,780 – 5,355 L	-15 °C to +120 °C	-1 to +2 bar	Anchor Agitator with Scrapers	Product A, Product B, Product D
ANFD-301	Agitated Nutsche Filter Dryer	Hastelloy C-22	3.0 m² Area	1,800 L Cake Vol	-20 °C to +140 °C	-1 to +4 bar	S-Blade Hydraulic Agitator	Product A, Product C, Product E
CENT-302	Vertical Basket Centrifuge	SS316L Teflon Lined	48" Diameter	450 kg Wet Cake	0 °C to +80 °C	Atmospheric	Variable Speed Bottom Discharge	Product B, Product D
RCVD-401	Rotary Cone Vacuum Dryer	SS316L Mirror Polish	2,000 L Gross	1,200 L Working	+20 °C to +130 °C	Full Vacuum (-0.98 bar)	Double Cone Tumbling Motion	Product A, Product C, Product D
VTD-402	Vacuum Tray Dryer	SS316L 20-Tray	1,500 L Total	900 L Tray Loading	+20 °C to +100 °C	Full Vacuum (-0.95 bar)	Static Hot Water Shelves	Product B, Product E
MIL-501	Fluid Energy Air Jet Mill	SS316L Ra < 0.4 µm	150 kg/h	Continuous Pass	Ambient (+25 °C)	7 bar Compressed Air	High-Velocity Jet Nozzles	All Products (A, B, C, D, E)

# 3. The 60%–85% Volumetric Occupancy Rule & Reaction Stoichiometry

# 3.1 The Volumetric Occupancy Rule ( $60\% - 85\%$ Rule)

To ensure effective mixing, heat transfer, and foaming clearance, batch liquid volume ( $V_{liquid}$ ) in a reactor must satisfy strict volumetric occupancy limits relative to nominal volume ( $V_{nominal}$ ):

0.60 \le \frac{V_{liquid}}{V_{nominal}} \le 0.85

Below $60\%$ Occupancy: Agitator blades may un-submerge or operate near the liquid surface, causing vortex air entrainment, severe foaming, incomplete mass transfer, and un-wetted heat transfer surface area.
Above $85\%$ Occupancy: Insufficient freeboard vapor space leads to liquid entrainment into overhead condensers during reflux or vacuum distillation.

# 3.2 Stoichiometric Batch Scale-Up & Volume Allocation

For a target batch output of $M_{API}$ (kg per batch), the required raw material charge $M_i$ and reaction vessel volume $V_R$ are calculated via:

M_i = M_{API} \cdot \frac{MW_i}{MW_{API}} \cdot \frac{1}{Y_{overall} \cdot ST_i}

V_R = \frac{\sum \left( \frac{M_{solvent}}{\rho_{solvent}} \right) + \sum \left( \frac{M_{solid}}{\rho_{solid}} \right)}{\eta_{occupancy}}

Where $Y_{overall}$ is overall molar yield and $\eta_{occupancy} \approx 0.75$ .

# 4. Annual Master Campaign Schedule (5 Products across 10 Equipments)

Below is the annual operational campaign schedule for 5 Commercial APIs produced in sequential campaigns across the 10 process equipment modules over 300 operating days (allowing 32 days for changeover wash windows and preventive maintenance):

Product Name	Campaign Window	Annual Target Output	Batch Scale (kg/batch)	Required Batches	Primary Equipment Train	Occupancy %	Campaign Days	Changeover Wash
Product A: Atorvastatin Intermediate	Jan – Mar (75 Days)	18.0 MT	300 kg	60 Batches	R-101 (GLS) ──► CR-201 ──► ANFD-301 ──► RCVD-401 ──► MIL-501	74% – 82%	68 Days	7 Days
Product B: Amlodipine Besylate API	Apr – May (50 Days)	12.5 MT	250 kg	50 Batches	R-102 (SS316L) ──► CR-201 ──► CENT-302 ──► VTD-402 ──► MIL-501	65% – 78%	44 Days	6 Days
Product C: Pregabalin API	Jun – Aug (70 Days)	24.0 MT	400 kg	60 Batches	R-104 (Hydro) ──► R-102 ──► ANFD-301 ──► RCVD-401 ──► MIL-501	70% – 84%	63 Days	7 Days
Product D: Metformin HCl Advanced	Sep – Oct (55 Days)	30.0 MT	600 kg	50 Batches	R-103 (Hastelloy) ──► CR-201 ──► CENT-302 ──► RCVD-401 ──► MIL-501	68% – 80%	49 Days	6 Days
Product E: Losartan Potassium	Nov – Dec (50 Days)	15.0 MT	300 kg	50 Batches	R-101 (GLS) ──► R-103 ──► ANFD-301 ──► VTD-402 ──► MIL-501	62% – 76%	44 Days	6 Days
ANNUAL TOTALS	300 Operating Days	99.5 MT / Year	—	270 Batches	10 Equipment Train Modules Fully Utilized	62% – 84%	268 Days	32 Wash Days

# 5. Master Facility Fit Engineering Audit Checklist

Calculate Controlling BCT: Determine $BCT_{controlling} = \max(t_i)$ and enforce charging interval $\Delta t_{charge} = BCT_{controlling}$ .
Audit Charging Frequency ( $f_{charge}$ ): Verify $f_{charge} = \frac{24}{\Delta t_{charge}}$ to prevent intermediate hold-up in crystallization or aging tanks.
Verify Volumetric Range: Ensure liquid reaction volume is between $60\%$ and $85\%$ of nominal vessel rating for agitation and heat transfer safety.
Match Process MOC Matrix: Verify corrosive chemistry (acidic halides, nitrations, chlorinations) against Glass-Lined Steel (GLS) or Hastelloy C-22.
Plan Changeover Wash Windows: Allocate 5 to 7 days of solvent reflux cleaning, line flushing, and analytical sign-off between consecutive API product campaigns.

# Applicable Engineering Standards & Guidelines

ISPE Baseline Guide Volume 3: API Manufacturing (2nd Edition).
ICH Q7: Good Manufacturing Practice Guide for Active Pharmaceutical Ingredients.
ASME BPE-2022: Bioprocessing Equipment Standard.