Computation of plate columns for NO_x absorption by a new stage‐to‐stage method

Abstract

A new stage-to-stage method has been developed for the calculation of NO, absorption columns. Each stage of the absorption column is simulated as a combination of a bubble column reactor (absorption) and an adiabatic plug flow reactor (oxidation). The bubble column reactor is modelled as two single stirred tank reactors, one as a gas-phase and one as a liquid-phase reactor, both coupled by mass and heat transfer. In this hydrodynamic model, a dynamic approach is adopted, in which the gas-phase transport of N204 is the limiting step for the absorption. A gas-phase pseudo-enhancement factor for N,04 is therefore introduced. The balance equations for a single phase of the bubble column are solved with a Newton-Raphson algorithm. The entire column calculation is divided into a gas and a liquid side. On both sides, the stage-to-stage method is applied in such a way that the overall calculation is performed as a loop process. The direction of the loop calculation follows that of the flow: gas-side upwards and liquid-side downwards.

Nitric Acid, Nitrous Acid, and Nitrogen Oxides

“…These static methods have the drawback of requiring the introduction of efficiency factors [51] that take into account limitation of transport of the reactants across the interface. Dynamic methods do not need empirical efficiency factors because they describe mass transfer in terms of physical and chemical laws [28], [31], [50], [52]. 3.…”

Absorção química de dióxido de nitrogênio (NO2)

“…Segundo a Wiegand et al (1990), à medida que aumenta a temperatura de alimentação da corrente gasosa, diminui a concentração de HNO 3 na corrente dos produtos do fundo da coluna, como se observa na Figura 5.…”

“…Para avaliar a absorção de dióxido de nitrogênio com reação química, em colunas de absorção, Wiegand et al, (1990) desenvolveram o modelo de equações das taxas de reação e observaram que a reação global (5) pode descrever o fenô-meno de transferência de massa com reação química, no processo de absorção. A reação avaliada pelos autores é de 3 a ordem, em relação ao reagente, dióxido de nitrogênio, e ocorre na fase líquida.…”

Renewable production of ammonia and nitric acid

“…We dynamically model the production complex based on existing work and first principles. Five submodels are considered: steam generation (STM), steam electrolysis (SOE), air separation (ASU), ammonia synthesis (NH3), and nitric acid production (HNO3) . We extend our steady‐state model to account for relevant process dynamics using dynamic mass and energy balances in units with large inertia: the SOE stacks, the steam boiler, the fixed‐bed reactors, the heat exchangers, the cryogenic distillation column, and the absorption column.…”