Propane (Propane) is an organic compound whose chemical formula is CH₂CH₃. It is a colorless and odorless gas and slightly soluble in water, ethanol and ether. The main applications of propane include petrochemicals, environmental protection and scientific research.

Propane is commonly used as refrigerant, internal combustion engine fuel or organic synthesis raw material, and can also be used as a raw material for cracking ethylene and propylene, and to make acrylonitrile, nitropropane, perchloroethylene, etc. In addition, in refineries, propane can be used as a solvent for deasphalting, desulfurization and as a coolant for other petrochemical products.

JZNC-XPP02B-3 This article will give you a detailed introduction to the preparation process of propane in refineries and VEGA’s measurement solution for propane, a medium with ultra-low dielectric constant and complex properties.

Propane preparation process in refinery

Propane preparation process of the refinery: crude propane is obtained from the propylene rectification tower reactor of the cracking unit, and then purified by the propane rectification tower to obtain propane with 90% purity, which is cooled by the tower reactor and sent to the propane storage tank, or the finished propane can be separated from the catalytic cracking gas. VEGA radar level gauges are used to measure the level of propane storage tanks.

Figure 1. Propane storage tank

Measurement difficulty

1. Propane has a very low dielectric constant of about 1.67, which will affect the reflected signal of radar waves.

2. The installation position is limited, there is no installation port on the tank body to install the radar, and it can only be installed on the by-pass pipe.

3. Because the propane in the reservoir needs to be recycled, in order to ensure that the propane is in a liquid state, the temperature will also change, and the propane inside the tank is a gas-liquid two-phase, when the temperature occurs, the dielectric constant will also change.

JZNC-XPP02B-3

VEGA Solutions

The customer originally used a capacitive liquid level meter, but as mentioned above, the dielectric constant of the medium in the tank is changed, which will cause the capacitance value of the capacitive liquid level meter to change, so the measurement results are very unstable.

The VEGAPULS 6X can be used for measurements in horizontal tanks already equipped with bypass tubes at the customer’s site. With the existing bypass tube structure, the radar signal can be better focused, and even low dielectric constant media such as propane can obtain good measurements without being affected by changes in dielectric constant.

In addition, why did we not use guided wave radar level meter to measure here? As shown in Figure 2 below, the bypass tube itself has a height of more than 2m. If the guided wave radar level meter is used, it will be very troublesome to lift the instrument to more than 4m before it can be taken out during debugging and maintenance. With this in mind, we ultimately chose a non-contact radar.

As is evident from the echo curve in Figure 3, the effective measurement of the echo curve is very good.

When developing a measurement solution, it is necessary to choose different frequencies of radar according to different media characteristics, volatility, gas phase density, etc., but with the introduction of the VEGAPULS 6X series, selection is no longer difficult, and now only one model can cope with a variety of different occasions.