An electric current-based monitoring system for EHDA of natural gas odorants

Due to its odorless nature, artificial odors are introduced into natural gas to enable easy detection when leakages occur (Saadatmand et al., 2015). The most commonly used method is drip injection (Tenkrat, 2016) which normally presents a problem during low flow periods due to low rates of diffusion. An alternative to this method would be electrohydrodynamic atomization.

Electrohydrodynamic atomization (EHDA), more commonly referred to as electrospray, is an atomization technique that uses a strong electric field to influence the breakup of a liquid into droplets (Grace & Marijnissen, 1994). By varying the applied electric field strength and the flow rate, for the same liquid, different electrospraying modes can be achieved. These modes include the cone-jet and the simple-jet modes. High-speed imaging and laser techniques are the most commonly used monitoring techniques to evaluate the droplet size, dispersion and which operational mode is taking place. However, such techniques may not always be practical in industrial processes.

A different method based on the characteristics of the spray’s electric current has been developed and proposed by Verdoold et al. (2014).

Figure 1. Schematic diagram of the setup

Figure 1. Schematic diagram of the setup

In this work, the authors have extended this electric current-based monitoring system for the use in the simple-jet mode (hundreds of mL·h-1). In addition, experiments will be conducted using tetrahydrothiophene (THT) as the spraying liquid to investigate the effects of the liquid’s physical properties on the spray’s electric current. The setup, a nozzle-to-ring up configuration, will be similar to the one used by Verdoold et al. (Figure 1).

The first experiments conducted in the enhanced dripping mode have shown a relationship between the frequency of the electric current and the droplet formation frequency (as shown in Figure 2). Further experiments will be conducted to find similar trends with higher flow rates, i.e. the simple-jet modes.

 

Figure 2. Electric current for a 50mL·h-1 water flow rate

Figure 2. Electric current for a 50mL·h-1 water flow rate

 

References

  1. Saadatmand, M., Foroughi, H., Dai, T., Misra, T., Bensabath, T. & Farnood, R. (2015). Odor fading in natural gas distribution systems. Process Safety and Environmental Protection, 94, 131-139.
  2. Tenkrat, D., Hlincik, T. & Prokes, O. (2016). Natural gas odorization. In Tech Open.
  3. Grace, J. M. & Marijnissen, J. C. M. (1994). A review of liquid atomization by electrical means. Journal of Aerosol Science, 25(6), 1005-1019.
  4. Verdoold, S., Agostinho, L.L.F., Yurteri, C.U. & Marijnissen, J.C.M. (2014). A generic electrospray classification. Journal of Aerosol Science, 67, 87-103.

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