# Design, Sizing & Thermal Rating of a 100 KLD Multiple Effect Evaporator (MEE), VOC Stripper & Vacuum System for ZLD in Chemical & API Plants

In active pharmaceutical ingredient (API) manufacturing and specialty chemical synthesis plants, Zero Liquid Discharge (ZLD) trains must handle high-TDS wastewater containing volatile organic solvents. A conservative industrial plant design operates on a 20 Hours/Day Basis ($100 \text{ KLD} / 20 \text{ h/day} = \mathbf{5,000 \text{ kg/h}}$ feed rate), reserving 4 hours daily for CIP acid/alkali washing, descaling, and decanting turnarounds.

This comprehensive technical guide details the mass-energy balance, 10% VOC Stripper surface condenser sizing, MEE vacuum pump & surface condenser rating, and Technoforce 40% TDS outlet hybrid topology for a 100 KLD ($100,000 \text{ Liters/Day}$) industrial ZLD facility.

# 1. Conservative Design Basis: 20 Hours/Day Operating Schedule

Industrial ZLD plants experience scaling by inorganic salts ($\text{CaSO}_4$, $\text{Na}_2\text{SO}_4$, $\text{NaCl}$) and bio-fouling. Designing for 20 operating hours per day provides essential engineering margins:

# 1.1 Feed Effluent Composition Breakdown (5,000 kg/h)

• Volatile Organic Solvents (VOCs): $10.0\% \text{ w/w}$ ($500 \text{ kg/h}$ Methanol, IPA, Acetone, Toluene).
• Inorganic Total Dissolved Solids (TDS): $5.0\% \text{ w/w}$ ($250 \text{ kg/h}$ mixed sodium salts).
• Water Content: $85.0\% \text{ w/w}$ ($4,250 \text{ kg/h}$ $\text{H}_2\text{O}$).

# 2. Upstream Solvent Stripper Column & VOC Surface Condenser Sizing

# 2.1 Stripper Column Operating Parameters

To prevent volatile organic solvents from contaminating the MEE distillate ($\text{COD} > 5,000 \text{ ppm}$), feed is introduced into an atmospheric steam stripping column with Sulzer Mellapak 250Y structured packing:

• Live Stripping Steam Rate: $0.125 \text{ kg steam / kg feed} = \mathbf{625 \text{ kg/h}}$ live steam ($1.5 \text{ bar(g)}$).
• Overhead Vapor Generation: $500 \text{ kg/h}$ VOCs $+ 150 \text{ kg/h}$ water vapor $= \mathbf{650 \text{ kg/h}}$ overhead vapor at $82.0^\circ\text{C}$.
• Stripped Bottoms Output to MEE: $\mathbf{4,500 \text{ kg/h}}$ ($250 \text{ kg/h}$ TDS $+ 4,250 \text{ kg/h}$ water $= 5.56\% \text{ TDS}$, VOC $< 100 \text{ ppm}$).

# 2.2 Stripper Overhead Surface Condenser Sizing ($A_{cond,strip}$)

The overhead VOC vapor is condensed in a dedicated tubular Stripper Surface Condenser:

• Condensation Thermal Load ($Q_{strip}$): $650 \text{ kg/h} \times 900 \text{ kJ/kg} / 3,600 = \mathbf{162.5 \text{ kW}}$.
• Cooling Water Flow ($32^\circ\text{C} \to 37^\circ\text{C}$): $28.0 \text{ m}^3/\text{h}$.
• Logarithmic Mean Temp Difference ($\text{LMTD}$): $24.5^\circ\text{C}$.
• Overall U-Value: $0.85 \text{ kW/m}^2\text{K}$.

# 3. MEE Mass Balance: 40% TDS Outlet to ATFD

Raw Feed (5,000 kg/h) ➔ [ VOC Stripper ] ➔ [ FFE-1 + TVR ] ➔ [ FFE-2 ] ➔ [ FCE-3 ] ➔ 40% Brine Slurry (625 kg/h) ➔ ATFD
 (10% VOC | 5% TDS)     (500 kg/h VOCs)    (1,240 kg/h H2O)  (1,285 kg/h)  (1,350 kg/h)  (250 kg/h Salt + 375 kg/h H2O)

# 3.1 Mass Balance Derivation for 40% Brine Slurry

# 4. MEE Vacuum System & Main MEE Surface Condenser Rating

# 4.1 Liquid Ring Vacuum Pump (LRVP) Specification

Effect 3 operates under deep vacuum to lower the boiling point of concentrated brine to $68.0^\circ\text{C}$ ($T_{sat} = 49.5^\circ\text{C}$ considering $18.5^\circ\text{C}$ BPE):

• Operating Pressure: $-0.88 \text{ bar(g)}$ ($0.12 \text{ bar(a)}$ absolute pressure / $90 \text{ mmHg}$).
• Vacuum Pump Package: 2-stage Liquid Ring Vacuum Pump (LRVP) with air ejector booster ($15.0 \text{ kW}$ motor).

# 4.2 Main MEE Surface Condenser Sizing ($A_{cond,MEE}$)

Effect 3 vapor ($1,350 \text{ kg/h}$ at $0.12 \text{ bar(a)}$) is condensed in a vertical shell-and-tube surface condenser:

• Condenser Thermal Load ($Q_{cond,MEE}$): $1,350 \text{ kg/h} \times 2,362 \text{ kJ/kg} / 3,600 = \mathbf{885.8 \text{ kW}}$.
• Cooling Water Flow ($32^\circ\text{C} \to 38^\circ\text{C}$): $127.0 \text{ m}^3/\text{h}$.
• Logarithmic Mean Temp Difference ($\text{LMTD}$): $14.5^\circ\text{C}$.
• Overall U-Value: $0.95 \text{ kW/m}^2\text{K}$.

# 5. Complete Equipment Rating & Sizing Summary (20h Basis)

• Cooling Tower Sizing: Check our interactive Cooling Tower Sizer for utility condenser sizing.
• Engineering Documentation: Download technical design whitepapers at our Documentation Center.