Simulation of the Process of Odorizing a Natural Gas

Abstract

A model of odorizing a natural gas is built on the basis of the system of motion of viscous, compressible, heatconducting, two-component medium with account for the odorant diffusion. Calculations of convective and diffusional mixing, in a channel, of a gaseous methane main fl ow interacting with its side jets containing an odorizing gas has been performed. The regimes of fl ow at different gas velocities in the main and side channels are considered, and the process of the equalization of the odorant concentration by convective and diffusional mechanisms are considered.Introduction. In addition to cleaning and drying, the preparation of a natural gas for utilization comprises also its mixing with a small quantity of a gas-odorant having pronounced organoleptic properties. At all of the gas-distribution stations of Russia, use is made of the MNM (mixture of natural mercaptans) odorant manufactured in accord with the Specs. 51-31323949-94-2002. It has the odor of hydrogen sulfi de with a low perception threshold (its odor can be perceived at a partial odorant pressure starting from 0.19 mg/m 3 and above) [1]. In gas-distributing systems, the partial density of the odorant is approximately 16 mg/m 3 , which allows one to diagnose the presence of natural gas in air. There exist various technologies of odorizing the natural gas, with an odorant being introduced into the gas fl ow in both the liquid and gaseous state [2]. In the liquid state, an odorant is injected into a gas pipeline with the aid of a proportioning pump. In odorizing with mercaptan vapors, part of the general gas fl ow is branched off, saturated with the odorant vapors, and thereafter is returned into the general gas fl ow. The accuracy with which the odorant concentration is maintained in the natural gas is low in the existing odorizing systems: under the condition of natural gas fl ow close to a stationary one, the relative error of the odorant partial density lies in the range from 5 to 20% [1]. The transient state of the change in the gas fl ow rate in a pipeline, as well as the fl uctuations of the surrounding air temperature, increases the error of gas batching. For this reason, in developing systems for odorization process automation, it is necessary to describe the convective and diffusional mixing of the natural gas with an odorant for different regimes of fl ow.Mathematical Model and Method of Solution. The model of the process of odorizing the natural gas is based on the system of equations of motion of a viscous, compressible, heat-conducting, two-component gas in which the odorant diffusion is taken into account [3]:

Chromatographic Examinations in the Gas Network Odourised by Tetrahydrothiophene

“…Researchers proved, that Reynolds Average Navier-Stokes (RANS) equations with the k-ε turbulence model show a strong agreement for the experimental data from a real pipeline. Similar results achieved Tukmakov et al [33] using model built on the basis of built on the basis of the system of motion of viscous, compressible, heatconducting, two-component medium with account for the odorant diffusion. Also, Nagaresh et al [34] used mass transfer model, correlated for bibble diameter estimation, and SVM-based model.…”

“…In Russia, at all of the gas-distribution stations, the MNM (mixture of natural mercaptans) is used. It has the odour of hydrogen sulphide with a low perception threshold (partial odourant pressure is starting from 0.19 mg · m -3 and above) [6]. In Italy, two gas odourants are used: one consists entirely of tetrahydrotiofene, whereas the other one is a mixture of three mercaptans, i.e.…”