Separation of15N by chemical exchange in NO, NO2−HNO3 system under pressure

Abstract

The basic isotopic exchange reaction is responsible for the separation of ISN in the Nitrox system that between gaseous nitrogen oxides and aqueous nitric acid with a single stage separation factor ~= 1.055 for 10M nitric acid, at 25 ~ and atmospheric pressure takes place. In order to know what happens in ~5N separation at higher pressure, when the isotopic transport between two phases is improved, a stainless steel laboratory experimental plant with a 1000 mm long • 18 mm i.d. column, packed with triangular wire springs 1.8• mm 2, was utilised. At 1.5 atm (absolute), and 2.36 mlcm -2 .min -l flow rate HETP was 7% smaller than at atmospheric pressure and 1.5 times smaller flow rate. HETP at 3.14 mlcm-2.min -I flow rate and 18 atm is practically equal with that obtained at atmospheric pressure and 2 times smaller flow rate. The operation of the ISN separation plant at 1.8 atm (absolute), instead of atmospheric pressure, will permit doubling of the 10M nitric acid flow rate and of lSN production of the given column.

The Production of the Isotope 15N by Isotopic Exchange in Nitrox System at Pressure

“…The calculus of the isotopic separation (S) and of the height equivalent to theoretical plate (HETP) [10] for each column was done by using the mean values of the 15 N concentration of the plateaus 1 -12, marked on the graph of figure 1. The HETP values were calculated not only in the case of operation at total reflux but also in production, in order to have comparison elements with the data of separation plant operated at atmospheric pressure, (table 3).…”

The Calculus of the Operation Parameters at Pressure of the Primary Separation Column of the 15N Production Plant

“…The data obtained on an experimental separation column 100 cm length and 18 mm inside diameter, with the same type of packing as of the primary separation column, are presented in the table 2, [2].…”

“…The isotopic concentration at the bottom of the separation column The total isotopic separation at steady state and total reflux is: (5) where: N b and N t are the 15 N molar fractions in nitric acid or nitrogen oxides, measured at the bottom and in the top of the separation column; n is the number of the transfer unities, or theoretical plates, achieved in the separation column: n = Z/HETP (6) where: HETP is the height equivalent to the theoretical plate (cm). Initially is measured 15 N molar fraction on nitrogen oxides samples from the bottom and in the top of the separation column, at steady state and total reflux, then the total isotopic separation and the number of transfer unities (n) are calculated, [2]. In the same operation conditions can be calculated the 15 N molar fraction at the column bottom, if HETP (for the specific packing and 10M HNO 3 flow rate) and the column length (Z) are known, by using the following relation: N b = 3.66 x 10 -3 x 1.055 Z/HETP /(1 + 3.66 x 10 -3 .1.055 Z/HETP ) (7) The maximum product of a separation column (plant)…”

“…It was experimentally proved on a laboratory scale plant that at 0.8 atm (1.8 atm absolute) it is possible to increase the flow rate of 10M HNO 3 in the 15 N separation column 1.57 times in comparison with the operation at atmospheric pressure [2].…”

Dynamic modelling and simulation of15N separation by chemical exchange in NO, NO2–HNO3system

“…Various aspects of the complex process of 15 N separation have been analysed in numerous studies [1][2][3][4][5][6]. Experimental data are available from measurements of the 15 N separation in different operating conditions (various pressures, nitric acid concentrations, experimental plants, etc.).…”