Dry fog humidification applications in the textile industry

Textile industry is a vital traditional sector in our country, employing over 15 million people. The related population involved in the cultivation, production, and processing of raw materials exceeds 100 million, playing a crucial role in social employment, economic growth, and foreign exchange earnings. In 2004, the total output value of China's textile industry reached 2.64 trillion yuan, with exports amounting to $97.4 billion, accounting for one-fifth of the global market, making China the undisputed leader in the world's textile industry. Since joining the WTO, China's textile industry has experienced rapid growth after facing more intense competition and a more open market. From a large and medium-sized enterprise perspective, the number of businesses surged from 21,000 in 2001 to 29,000 in 2004, an increase of 38%; sales increased from 866.3 billion yuan to 1.548 trillion yuan, a growth of 78%; and the number of employees rose from 7.63 million to 8.946 million. After 2005, with the elimination of textile quotas, the industry entered a post-quota era. This is both an opportunity and a challenge for many textile enterprises. It should be noted that there is an excess of textile and apparel production worldwide, with slim industry profits. Amid the cancellation of quotas and a weak global economic growth, and under the dual pressure from developed and developing countries, many Chinese textile enterprises are facing a low-profit era. Moreover, due to the tight energy and power supply, some enterprises are operating at reduced capacity, even having to cancel orders. Therefore, striving to enhance labor productivity, improve product quality, reduce waste rates, and conserve energy has become a critical approach for many textile enterprises to cut costs. Practice has proven that scientifically utilizing favorable air conditions can effectively achieve these goals.

Temperature, humidity, air velocity, dust concentration, and freshness are the five fundamental components of air conditions. They are closely related to production conditions, efficiency, process, product quality, and more. Among them, humidity is a significant factor affecting the quality of the air environment, with the relative humidity of the air exerting corresponding effects on people or objects in the environment. Research finds that humidity is a primary factor in air cleanliness, product durability, and thus influences product quality, work efficiency, and comfort, sometimes even being a decisive factor. In response to this, textile enterprises have long employed numerous methods to improve relative humidity in the air, aiming to achieve the optimal environment required for production. From early misting to later air conditioning humidification, and now to industrial humidifier humidification, a plethora of new technologies have emerged, playing a decisive role in the scientific modernization of textile and clothing production. The humidity requirements in the textile industry are 50%-85%RH. Specific humidity for different processes can be found in the attachment "Relationship between Textile Processes and Relative Humidity."

Let's take textile fibers as an example.

1. Relative Humidity and Moisture Content Relationship

Relative humidity in the air varies, and so does the moisture regain rate of fibers. As shown in Figure 1, an increase in relative humidity leads to a higher moisture regain rate of fibers, while the opposite is true.

2. Relative humidity and its relationship with strength

Relative humidity has a significant impact on the strength of fibers, enhancing and improving the alignment of long-chain molecules to increase strength. For cotton fibers, for example, when the relative humidity is between 60-70%, their strength can increase by approximately 50% compared to a dry state.

3. Relative humidity and elongation relationship

Moisture-absorbed fibers, due to increased intermolecular distances, are more prone to relative displacement under external forces, hence their elongation increases with rising relative humidity. Amongst them, wool, silk, and rayon fibers are more elongatable after reabsorbing moisture compared to natural fibers like cotton and hemp. As for synthetic fibers (such as polyester), their poor moisture absorption results in a lesser impact of relative humidity on elongation.

4. Relationship between relative humidity and softness

As relative humidity increases, due to the expanded intermolecular distances in fibers after moisture absorption, the hardness and brittleness of the fibers decrease accordingly, significantly improving the softness of the fibers.

5. The relationship between relative humidity and conductivity

Friction between mechanical surfaces and fibers, or between fibers themselves, inevitably leads to fiber electrification. When fibers carry different charges from the body, it hinders the smooth process of fiber stretching, combing, interlacing, and winding. When fibers have different charges, they do not adhere to each other, causing flyaways and pilling, leading to increased warp fraying and skipped picks, resulting in a rough fabric surface and scattered streaks. Increasing the relative humidity of the air can lower the specific resistance of fibers, thereby accelerating the dissipation of charges and eliminating static electricity.

Common Methods of Industrial Humidification and a Simple Comparison
Centrifugal Humidification: Advantages: Low cost; mature. Disadvantages: Large particles, poor uniformity; water waste. Suitable for outdoor humidification.