ffsshhttiikk What I do
- Design chemical reactors and reaction systems
- Calculate mass and energy balances
- Design separation processes and equipment
- Model thermodynamic properties and phase equilibria
- Specify process equipment and piping
- Design process control systems
- Optimize chemical processes for efficiency
When to use me
When designing chemical processes, reactors, separation systems, or any process involving chemical transformations and separations.
Core Concepts
- Mass and energy balances
- Chemical reaction kinetics and reactor design
- Thermodynamics and phase equilibria
- Heat and mass transfer
- Separation processes (distillation, absorption, extraction)
- Process control and instrumentation
- Process safety and hazard analysis
- Equipment sizing and selection
- Process economics and optimization
- Transport phenomena
Code Examples
Mass and Energy Balances
from dataclasses import dataclass
from typing import List, Tuple
import numpy as np
@dataclass
class Stream:
name: str
mass_flow: float # kg/hr
component: str
mass_fraction: float
def mass_balance(
inlet_streams: List[Stream],
outlet_streams: List[Stream]
) -> Tuple[float, float]:
"""Calculate total inlet/outlet and component balances."""
m_in = sum(s.mass_flow for s in inlet_streams)
m_out = sum(s.mass_flow for s in outlet_streams)
return m_in, m_out
def component_balance(
streams: List[Stream],
component: str
) -> Tuple[float, float]:
"""Calculate component mass flow."""
inlet = sum(s.mass_flow * s.mass_fraction
for s in streams if "inlet" in s.name.lower())
outlet = sum(s.mass_flow * s.mass_fraction
for s in streams if "outlet" in s.name.lower())
return inlet, outlet
def combustion_air_requirement(
fuel_carbon: float, # kg C/kg fuel
fuel_hydrogen: float, # kg H/kg fuel
fuel_sulfur: float, # kg S/kg fuel
excess_air: float = 0.15 # 15% excess
) -> dict:
"""Calculate combustion air requirements."""
O2_stoich = 2.67 * fuel_carbon + 8 * fuel_hydrogen + fuel_sulfur
O2_actual = O2_stoich * (1 + excess_air)
air_required = O2_actual / 0.233
return {
"stoich_air_kg": O2_stoich / 0.233,
"actual_air_kg": air_required,
"flue_gas_kg": air_required + 1 - fuel_carbon - fuel_hydrogen - fuel_sulfur
}
# Example: Combustion calculation
fuel = {"C": 0.85, "H": 0.10, "S": 0.02, "O": 0.03}
air = combustion_air_requirement(fuel["C"], fuel["H"], fuel["S"], 0.10)
print(f"Stoichiometric air: {air['stoich_air_kg']:.2f} kg air/kg fuel")
print(f"Actual air required: {air['actual_air_kg']:.2f} kg air/kg fuel")
Reactor Design
@dataclass
class Reaction:
A: float # pre-exponential factor
Ea: float # activation energy J/mol
dH: float # heat of reaction J/mol
order: float
def arrhenius_rate(
T: float, # K
A: float,
Ea: float,
R: float = 8.314
) -> float:
"""Calculate rate constant using Arrhenius equation."""
return A * np.exp(-Ea / (R * T))
def cstr_design(
Fa_in: float, # mol/hr
X: float, # conversion
rA: float # mol/hr/m³
) -> float:
"""Calculate CSTR volume."""
Fa_out = Fa_in * (1 - X)
Fa_avg = (Fa_in + Fa_out) / 2
return Fa_in * X / rA
def pfr_design(
Fa_in: float,
X1: float,
X2: float,
k: float,
order: int
) -> float:
"""Calculate PFR volume using numerical integration."""
from scipy.integrate import quad
if order == 1:
def integrand(X):
return 1 / (k * (1 - X))
else:
def integrand(X):
return 1 / (k * (1 - X)**order)
V, _ = quad(integrand, X1, X2)
return Fa_in * V
def adiabatic_reactor_temperature(
T_in: float,
X: float,
dH: float,
Cp_avg: float,
MW_avg: float
) -> float:
"""Calculate outlet temperature for adiabatic reactor."""
return T_in - X * dH * MW_avg / Cp_avg
# Example: CSTR design
Fa_in = 1000 # mol/hr
X = 0.85
T = 400 # K
reaction = Reaction(A=1e6, Ea=50000, dH=-100000, order=1)
k = arrhenius_rate(T, reaction.A, reaction.Ea)
V = cstr_design(Fa_in, X, k * (1 - X) * 1000)
print(f"Rate constant at 400K: {k:.6f} s⁻¹")
print(f"Required CSTR volume: {V:.2f} m³")
Distillation Design
def mccabe_thiele_stages(
xD: float, # distillate purity
xB: float, # bottoms purity
xF: float, # feed composition
q: float, # feed thermal condition
alpha: float, # relative volatility
reflux_ratio: float
) -> dict:
"""McCabe-Thiele stage calculation."""
R = reflux_ratio
R_min = (xD - yF) / (yF - xF) if alpha > 1 else float('inf')
yF = alpha * xF / (1 + (alpha - 1) * xF)
N_min = np.log((xD / (1 - xD)) * ((1 - xB) / xB)) / np.log(alpha)
stages = N_min * (R / (R - R_min + 0.01)) if R > R_min else 1
return {
"minimum_reflux_ratio": R_min,
"minimum_stages": N_min,
"actual_stages": int(stages)
}
def heat_reboiler_duty(
L: float, # kmol/hr
lambda_v: float, # kJ/kmol
) -> float:
"""Calculate reboiler heat duty."""
return L * lambda_v
def diameter_column(
V: float, # m³/hr
rho_v: float, # kg/m³
rho_l: float, # kg/m³
F_factor: float = 1.0
) -> float:
"""Estimate column diameter using flooding velocity."""
V_surf = V / 3600 / (np.pi / 4)
D = np.sqrt(4 * V_surf / (F_factor * np.sqrt(rho_v / (rho_l - rho_v))))
return D
# Example: Distillation column
column = mccable_thiele_stages(
xD=0.95, xB=0.05, xF=0.50, q=1.0, alpha=2.5, reflux_ratio=1.5
)
print(f"Minimum reflux: {column['minimum_reflux_ratio']:.3f}")
print(f"Required stages: {column['actual_stages']}")
Heat Exchanger Design
def lmtd(
Th_in: float, # °C
Th_out: float, # °C
Tc_in: float, # °C
Tc_out: float # °C
) -> float:
"""Calculate log mean temperature difference."""
dT1 = Th_in - Tc_out
dT2 = Th_out - Tc_in
if abs(dT1 - dT2) < 0.01:
return (dT1 + dT2) / 2
return (dT1 - dT2) / np.log(dT1 / dT2)
def heat_exchanger_area(
Q: float, # W
U: float, # W/m²K
lmtd: float
) -> float:
"""Calculate heat exchanger area."""
return Q / (U * lmtd)
def overall_heat_transfer(
hi: float,
ho: float,
k: float,
t: float,
fouling: float = 0.0001
) -> float:
"""Calculate overall U value."""
return 1 / (1/hi + fouling + t/k + fouling + 1/ho)
def shell_and_tube_pressure_drop(
N: int, # number of tube passes
L: float, # m
V: float, # m/s
rho: float, # kg/m³
f: float = 0.02
) -> float:
"""Estimate pressure drop in shell and tube exchanger."""
return 4 * f * (L / 0.0254) * (N * V**2 / (2 * rho))
# Example: Heat exchanger
Q = 500e3 # W
U = 500 # W/m²K
LMTD = lmtd(120, 80, 30, 60)
A = heat_exchanger_area(Q, U, LMTD)
print(f"LMTD: {LMTD:.1f} °C")
print(f"Required area: {A:.1f} m²")
Process Safety Calculations
def relief_valve_sizing(
P_set: float, # psig
P_atm: float, # psig
A_required: float, # in²
Kb: float = 1.0,
Kd: float = 0.975,
Kv: float = 1.0
) -> float:
"""Calculate relief valve orifice area (API 520)."""
A = (m * Kb) / (C * Kd * Kv * P_set) if P_set > P_atm else A_required
return A
def toxicity_limit(
LC50: float, # ppm
exposure_time: float, # hours
LCLo: float = LC50
) -> float:
"""Calculate acceptable exposure limit (AEL)."""
return LC50 * (8 / exposure_time)**0.5
def flammable_limit(
LFL: float, # % volume
UFL: float, # % volume
concentration: float
) -> str:
"""Check if mixture is flammable."""
if LFL <= concentration <= UFL:
return "FLAMMABLE"
elif concentration < LFL:
return "TOO LEAN"
return "TOO RICH"
def tnt_equivalence(
mass: float, # kg
efficiency: float = 0.05
) -> float:
"""Calculate TNT equivalent for explosion."""
return mass * efficiency * 4.184e6 / 4.184e6
# Example: Flammability check
mixture = flammable_limit(LFL=1.0, UFL=10.0, concentration=5.0)
print(f"Flammability status: {mixture}")
Best Practices
- Always include safety factors in equipment sizing
- Perform HAZOP analysis for new process designs
- Consider environmental regulations in plant design
- Use simulation software (Aspen, HYSYS) for complex calculations
- Account for worst-case scenarios in relief system design
- Consider operability and maintainability in equipment layout
- Document all design basis and assumptions
- Use standard equipment sizes to reduce costs
- Consider energy integration and pinch analysis
- Validate calculations with hand calculations and simulations