Industrial gases and compressed air

The use of dew point sensors or transmitters for moisture measurement is one of the many parameters widely monitored in industrial applications, especially in the production of industrial and specialty gases, as well as the use of compressed air systems.

monitoring process

Monitoring the moisture content of process gases is crucial for maintaining consistent product quality and protecting gas distribution and production equipment from damage. However, moisture measurement is increasingly being used as a means to improve energy efficiency and reduce operating costs, especially when using gas drying systems.

Moisture measurement in compressed air system

Compressed air is commonly referred to as the 'fourth industrial facility', providing power to drive many different industrial processes and systems, from pneumatic tools and material handling equipment to food preparation and waste recycling facilities.

A typical system uses a compressor to draw in and pressurize the atmosphere. Then, after being combined with an air treatment filter and dryer, it is stored in a receiving device and distributed to the point of use through pipelines as needed.

The atmosphere typically contains pollutants such as particulate matter, moisture, and oil vapor (depending on the environment). Under normal circumstances, these are usually not considered hazardous, but when air is compressed and the volume is reduced, the concentration of pollutants and the associated risk of damage to downstream equipment or manufactured products in contact with the air will increase. For example, moisture can cause corrosion to internal equipment and pipeline surfaces, and lead to lubricant emulsification. In applications such as food production, moisture can stimulate the growth of harmful microorganisms.

Under normal atmospheric and environmental conditions, each cubic meter of air at 35 ° C and 60% relative humidity contains approximately 23 grams of water vapor. Raising the pressure to 7 bar will increase the steam concentration by 8 times; In this example, each cubic meter of compressed air will contain 184 grams of water vapor. Please note that the temperature of the air will increase when it passes through the compressor. As it cools, the ability of air to hold the same volume of water decreases, so steam condenses in liquid form.

A typical 90kW compressor running for 8 hours a day will produce 970m ³ of compressed air and 140L of water. The British Compressed Air Association (BCAS) has released a best practice guide for compressed air filtration and drying (BPG104), which explains that "after compression and subsequent cooling, compressed air is discharged from the aftercooler, 100% saturated with water vapor".

Compressed air dryer

Therefore, the role of the dryer in each compressed air system is crucial for reducing or eliminating the presence of moisture. Dryers use refrigerant, film, or adsorption (desiccant) technology, typically specified to meet the expected high water vapor load for each application.

Traditionally, calculating the optimal drying cycle is based on the length of time required to adjust the known capacity of compressed air, and the selection of a dryer is usually only based on the energy consumption level stated by each manufacturer. Although this method may be acceptable when energy costs are low, it may be flawed when costs continue to rise and operating profit margins are under increasing pressure, as it may result in the dryer running much longer (consuming energy) than necessary.

What needs to be done is to precisely control the drying process so that the drying stops immediately when the moisture content in the compressed air reaches the correct level. This is where dew point sensors and transmitters play a crucial role, as they can eliminate wasted energy while maintaining good air quality.

It is difficult to summarize how much energy can be saved by adding integrated dew point sensors, as each application is different. However, it is appropriate to say that for applications such as food production that generate compressed air for a long time, energy consumption is significantly reduced compared to compressed air applications where dryers do not effectively control moisture,

Moisture measurement in industrial gas manufacturing

Similar situations also occur in the production of industrial gases, such as oxygen and nitrogen.

Due to factors such as manual handling, health and safety issues, and transportation and storage costs, people are gradually no longer using bottled gas and large gas storage tanks. On the contrary, more and more companies are using on-site gas generators.

These systems typically use pressure swing adsorption (PSA) or membrane technology to separate high-purity oxygen and nitrogen streams from compressed air sources. Although the adsorbents, hollow fibers, and semi permeable membranes used in PSA systems remove moisture during gas separation, it is still crucial to demonstrate that the dry air produced by each dryer meets the correct standards.

In addition, the integration of moisture measurement or dew point sensors will ensure optimal efficiency of the drying system, guarantee good air quality, and help reduce energy consumption and operating costs.

Traceability, safety, and peace of mind

One of the key benefits of being able to accurately monitor the moisture content in compressed air or separated airflows, regardless of the application, is that it can demonstrate gas safety and suitability for use. Especially in some critical production areas such as food and pharmaceuticals, the presence of moisture may have a destructive impact on the products being manufactured. The ISO standard for compressed air quality is ISO 8573.1, which specifies the maximum allowable levels of particulate matter, moisture, and oil pollution.

Compressed Air Quality Standards

Diversified choices

The use of next-generation humidity sensors or dew point transmitters, such as our SF series, will play an important role in reducing energy consumption and improving product or process quality. These instruments are capable of measuring dew point, moisture content, and low concentrations of trace moisture. They provide repeatability, multiple options, and are suitable for OEM and retrofit devices.