Gas Monitoring, Scrubber Balancing, and Nitrogen Balancing

Some of the important applications in the chemical and petrochemical industries that are carried out using thermal mass flowmeters are-

• Flare and flue gas monitoring
• Scrubber balancing
• Nitrogen Blanketing

In this article, each of these applications has been explained in detail.

1. Flare gas monitoring

A wide range of flow rates means that monitoring flare gas is challenging and can give rise to several problems. The normal flow rate of the flare gas is zero. However, when there is venting to the flare due to the pressure in the separator, there is a spike in the flow rate before it returns to zero with the release of the pressure. Additionally, this can cause a dramatic change in temperatures and the composition of the gas.

Thermal dispersion mass flow meters are most commonly used for flare gas monitoring because it gives the following advantages.

There is no requirement for external calibration for temperature and pressure correction because thermal flow meters provide direct mass flow measurement. The thermal mass flow meter measures a wide range of velocities have the ability for ultra-low velocity measurements. In fact, thermal flow meter sensors can capture velocities as low as 10SFPM and as high as 40,000 SFPM (sometimes higher with the use of a specialized shield). This huge range is beneficial when it comes to flare gas flow rate monitoring. For example, some brand thermal flowmeter can be calibrated for two conditions, both extreme in nature. One channel is for the vent gas and the other for capturing the upset state. The user's end system can then easily maneuver this by switching channels automatically; using a contact closure on the terminals. Our 3/4" rugged  flow sensor can withstand the extreme upset flare gas conditions. These devices are fast to respond, with a response time of less than 2 seconds. The response time is dependent on the flow rate. This is unlike the constant power devices that function by measuring the temperature change, thus having limits on measuring low flow rates. It has in-line or insertion probe thermal mass flow meters which can be used to measure large size ducts.

2. Flue gas (or headers) monitoring

The gases that exit from the various processes in a plant through a flue into the atmosphere are known as flue gases. Thermal gas mass flow meter can be used to monitor their emissions rates. Additionally, the different header ducts and pipes that lead to the main exhaust stack can also be monitored to give a warning in case there is an upset in the standard process.

3. Scrubber Balancing

As the name suggests, different types of scrubbers are used to clean (or scrub) the emission gases before they are released into the atmosphere. By using mass flow rate sensors at several points in the scrubber system, the efficiency of the system can be measured and the flow rates of the gases checked.

4. Nitrogen Blanketing

Sometimes, to prevent the content of a large tank from coming in contact with the surrounding air, a layer of nitrogen is used as a blanket. This is known as nitrogen blanketing and thermal mass flowmeters are especially effective in measuring the flow of this nitrogen and keep an eye out for any leaks in the process,thermal flow meter is a perfect choice as nitrogen gas flow meter.

Silver Automation Instruments supply low price cost thermal mass flow meters for flare gas, flue gas and nitrogen gas flow measurement.