Hydrotreating nitrogen and ammonia balance

RefineryHydrotreatingNitrogenBalance creates an immutable material-balance receipt for an early hydrodenitrogenation screen. It connects the total nitrogen carried by an OilAssayCharacterisation to explicit hydrogen use and a requested nitrogen mass fraction in the calculated liquid product.

This is stoichiometric accounting, not a reactor or yield model. It does not identify organic nitrogen species or predict pathways, kinetics, catalyst performance, severity, phase equilibrium, separation, heat duty, hydrocarbon cracking, product yield, or regulatory compliance.

Basis and equations

The caller supplies feed mass F in kg, feed nitrogen mass fraction zN, target product nitrogen mass fraction xN, and hydrogen consumption nu in mol H2 per mol nitrogen removed. The minimum nu = 1.5 supplies the three hydrogen atoms in one mole of ammonia. Larger values are explicit screening assumptions and their excess hydrogen is retained in the liquid bookkeeping balance.

NIST reports ammonia as H3N with molecular weight 17.0305 g/mol. The receipt derives nitrogen molar mass consistently:

M_N = M_NH3 - 1.5 M_H2

For nitrogen removal R_N, the liquid-mass change per kilogram of nitrogen removed is:

a = (nu M_H2 - M_NH3) / M_N

Because the target is defined on calculated product mass, the closed-form removal is:

R_N = (F zN - xN F) / (1 + xN a)

The receipt reports initial, removed and remaining nitrogen; hydrogen consumed; ammonia produced; hydrogen retained in liquid; product mass; achieved product nitrogen; and total and nitrogen closure residuals. Invalid or non-closing inputs fail closed.

Java example

The qualified DOE/OEDI Big Hill assay reconstructs 0.1095129 mass% bulk nitrogen. The 10 ppm target and 4.0 mol H2/mol N below are illustrative caller assumptions, not measured or fitted design values.

RefineryHydrotreatingNitrogenBalance receipt =
    RefineryHydrotreatingNitrogenBalance.calculate(
        1000.0, 0.001095129, 10.0e-6, 4.0);

double productMassKg = receipt.getProductMassKg();
double hydrogenConsumedKg = receipt.getHydrogenConsumedMassKg();
double ammoniaProducedKg = receipt.getAmmoniaProducedMassKg();

On that 1000 kg basis, the receipt removes 1.085135947 kg nitrogen, consumes 0.624703028 kg hydrogen, produces 1.319399583 kg ammonia, retains 0.390439393 kg hydrogen in the liquid bookkeeping balance, and returns 999.305303446 kg liquid product at 10 ppm total nitrogen. Total-mass and nitrogen residuals are zero within floating-point tolerance.

Use calculateForAssay(...) to read getBulkNitrogenMassFraction() without mutating the assay, its cuts, or the thermodynamic system.

Provenance and engineering boundary

The engineer must select and document the H2/N ratio and target for the intended screen. A design, yield, duty, catalyst, product-quality, or compliance claim requires independently validated nitrogen-species, reaction, feed, reactor, separation, and operating-condition models.