Hydrotreating hydrogen supply and outlet gas balance

RefineryHydrotreatingHydrogenSupplyBalance composes a qualified RefineryHydrotreatingSulfurBalance with explicit makeup-hydrogen purity, hydrogen supply factor, and average non-hydrogen molar mass. It reports the makeup-gas requirement and the ideal material balance of hydrogen, hydrogen sulfide, and the non-hydrogen makeup fraction.

This is material bookkeeping, not a reactor, separator, or recycle model. It does not predict kinetics, catalyst activity, pressure or temperature effects, hydrogen solubility, phase equilibrium, purge behavior, compression, heat duty, product yield, emissions, or compliance.

Basis and equations

The upstream sulfur receipt supplies consumed hydrogen mass and produced hydrogen-sulfide mass. The caller additionally supplies:

• hydrogen supply factor fH2, mol H2 supplied per mol H2 consumed, with fH2 >= 1;
• makeup hydrogen mole fraction yH2, with 0 < yH2 <= 1; and
• average molar mass MnonH2, kg/mol, for the non-hydrogen makeup fraction.

For consumed hydrogen moles nH2,cons, the makeup and outlet balances are:

nH2,in = fH2 * nH2,cons
nmakeup = nH2,in / yH2
nnonH2 = nmakeup - nH2,in
nH2,out = nH2,in - nH2,cons
nout = nH2,out + nH2S + nnonH2

The receipt calculates makeup and outlet masses from the explicit component molar masses. Its overall residual closes liquid feed plus makeup gas against liquid product plus outlet gas. If the upstream sulfur receipt removes no sulfur, the required makeup and outlet gas are both zero.

Java example

The example reuses the public DOE/OEDI Big Hill sulfur case qualified by the upstream receipt. The 90 mol% H2 makeup composition, 1.5 supply factor, and nitrogen-molar-mass non-H2 proxy are illustrative screening assumptions, not plant data or recommended design values.

RefineryHydrotreatingSulfurBalance sulfur =
    RefineryHydrotreatingSulfurBalance.calculate(
        1000.0, 0.0040867518, 15.0e-6, 2.0);

RefineryHydrotreatingHydrogenSupplyBalance gas =
    RefineryHydrotreatingHydrogenSupplyBalance.calculate(
        sulfur, 1.5, 0.90, 0.0280134);

double makeupMassKg = gas.getMakeupGasMassKg();
double outletMassKg = gas.getOutletGasMassKg();
double outletHydrogen = gas.getOutletHydrogenMoleFraction();
double residualKg = gas.getOverallMassBalanceResidualKg();

On this 1000 kg basis, the receipt consumes 253.971233373 mol H2 and supplies 380.956850059 mol H2 in 423.285388954 mol makeup gas. It reports 1.953729586 kg makeup gas and 5.769550859 kg outlet gas. The outlet gas is 3/7 H2, 3/7 H2S, and 1/7 non-H2 on this ideal molar basis. Overall mass closure is numerical zero.

Provenance and engineering boundary

• The public DOE/OEDI Big Hill crude-oil assay supplies the upstream sulfur case.
• The US Energy Information Administration defines catalytic hydrotreating as contacting petroleum fractions with hydrogen in the presence of a catalyst.
• The AIChE public hydrotreating overview describes excess hydrogen and sulfur conversion to hydrogen sulfide.
• The NIST Chemistry WebBook hydrogen-sulfide entry provides the H2S molecular weight used upstream.
• The NIST Chemistry WebBook nitrogen entry provides the illustrative nitrogen molar mass used as the non-H2 proxy.

The engineer must supply makeup-gas composition and excess hydrogen appropriate to the intended screen. A process-design claim requires a separately validated reaction/catalyst model, feed contaminant specification, operating envelope, gas-liquid equilibrium, recycle and purge model, separator and compressor model, product-yield model, and plant hydrogen-system constraints.