Multiple-Effect Evaporator (MEE) Steam Economy Calculator

In concentrated solutions (caustic soda, aluminate, black liquor, crystallizing ZLD brine), dissolved solids cause immense boiling point elevations ($Delta T_{BPE} = 15^circ-30^circ ext{C}$). Because vapor boils at saturation temperature but the liquid boils at $T_{sat} + Delta T_{BPE}$, this temperature jump is permanently deducted from the available driving force in every single effect. If too many effects are specified, $sum Delta T_{BPE}$ exhausts the total available thermal head, dropping effective $Delta T$ to near-zero.

Vapors generated from chemical feeds carry dissolved atmospheric gases ($CO_2, O_2, N_2$) or vacuum in-leakage. Even a 0.5% concentration of non-condensable gas creates a stagnant insulating boundary layer over condensing calandria tubes, dropping the steam-side condensing film coefficient by 50% to 75%. Continuous top and bottom calandria vent orifices piped to the next effect or vacuum condenser are mandatory.

In falling film evaporators, liquor must maintain a continuous wetting rate per tube circumference ($w_{min} ge 150-200 ext{ kg}/( ext{m}cdot ext{h})$). If liquid distribution trays suffer clogging, unlevel installation, or low feed rate, the falling liquid film breaks into dry rivulets. The bare metal tube overheats, baking organic syrups, proteins, or polymers into rock-hard burnt crusts that choke tube bundles.

High vapor release velocities from boiling liquor generate fine aerosol mists. Without high-efficiency demister chevron pads or tangential vapor separator bodies sized for low vapor velocity ($v_{vap} < 0.05 sqrt{( ho_L - ho_V)/ ho_V}$), concentrated chemical liquor carries over into the next calandria steam chest. This contaminates pure boiler-return condensate, forcing contaminated condensate dumping and creating severe boiler feedwater treatment costs.

Standard austenitic stainless steels (304L, 316L) suffer violent transgranular stress corrosion cracking (SCC) when exposed to hot chloride or alkaline solutions at temperatures above $60^circ-70^circ ext{C}$. High-temperature effects ($T > 100^circ ext{C}$) in caustic soda or salt evaporation must utilize pure Nickel 200/201 or Titanium Grade 2 metallurgy; using 316L results in catastrophic calandria tube fracture within months.