While, on one side, since years, there are a lot of talks about air pollution, the same is not for water consumption, even huge alarms have been highlighted by the scientific community. Water is still considered something that can be exploited without limitations.
Unfortunately, the actual situation is critical and it has to be faced as a global problem: in emerging Countries, water consumption is constantly increasing, but the access to drinking water is not yet guaranteed to the entire world population.
Even if water is covering the most of our planet, drinking water represents only a minimal percentage, intensive agriculture, industrial processes and pollution are quickly reducing even more its availability.
It is time to realize that every one of our actions has consequences on the environment and to start acting to reduce our impact: it is not just matter of slogans, it is matter of life. We have to move towards a reduction in the consumption of natural resources, and water is one of the most important for the life. Same like air and hearth, water is essential: using it in a respectfully is an imperative obligation.
Coming to textile industry, and, specifically, to denim production, water represents a key factor with significant consumption during dyeing pre-treatments and post- treatments.
In fact, all indigo dyeing machines, regardless if based on slasher or rope technologies, are equipped with up to three/four washing boxes, both before and after the pure indigo dyeing section. These boxes are generally fed with hot softened water.
Target of these washing processes is, if before dyeing, the removal of impurities from the yarn to allow the best dyeing results and, if after dyeing, the removal of unfixed dye stuff and all the chemicals remainders used during the process.
To give an idea of the numbers we are talking about and the related involvements of ecology and economy aspects, you can consider that, depending on the technology – slasher or rope – and the machine production capacity, water consumption ranges from 5 to 15 cubic meters per hour, corresponding to 120-360 cubic meters per day in case of 24 hours working activity.
Considering these numbers, it is obvious the necessity and the impact of reducing the water consumption and consequently steam for its heating and chemicals.
Targeting to reduce these enormous consumptions of water and steam, the classic washing boxes of dyeing ranges have undergone several updating during the last years. For example: the water counterflow feeding, the internal division in multiple compartments, the adding of spray systems with pumps or cascades, etc., sometime even combined with ultrasonic generators. Unfortunately, all these efforts have not fully reached the expected results.
In fact, when the yarn sheet moves in water, according to hydrodynamic laws, a film, made of liquid, is formed on both the surfaces, that moves together with the yarn sheet. This film is preventing a real exchange with water and, thus the cleaning effect, that happens only where are “NIPS” (see Figures 1-2) when the yarn touches the guide rollers.
To improve the washing effect, is thus necessary to create a turbulence enough to disturb the forming of these films.
The ideal washing, talking about yarn sheets, should assure a few key advantages: the maximum exchange water/yarn, the maximum removal of soluble and not soluble substances, the absolute absence of any disturbing of yarn distribution in the sheet, no power consumption and the minimum water consumption is possible.
The importance of washing efficiency, both if part of pretreatment operations as well as in case of final steps of the dyeing process, cannot be underestimated. In fact, the good results of final fabric quality are largely depending on these washings, as well as the process costs.
In general, washing techniques are considered by mechanical designers, something very simple and not allowing any significant revolution if keeping the system mechanically simple and with low maintenance.
On the contrary, a brilliant idea, verified and experimented in our laboratory, has allowed MASTER to develop the cylinder named “CRAFTYROLL” (Pat.). It is based on a special radial structure whose functioning effect is shown in Figure 3. Unlike classic cylinders, “CRAFTYROLL” when rotating, is imposing hydrodynamic force to water, forcing its passage through the yarn sheet – enveloping the cylinder – and achieving a strong remarkable washing effect.
In other words, our “CRAFTYROLL”, in addition to the traditional system where the yarn moves through the water, it adds the innovative system making the water pass through the yarn, thus enhancing the washing effect.
This special and innovating cylinder is available as per usual diameters of existing washing boxes, both in slasher and rope dyeing ranges, easily replacing regular cylinders, without any problem.
Substituting all the cylinders in a typical washing box, same as in Figure 1., it is possible to achieve both the single improvement of washing effect on each single cylinder as well as a global turbulence in the entire box volume, which avoids those films enveloping the yarn in today standard boxes, enhance the washing effect.
Thanks to these effects, the feeding water flow can be drastically reduced, at least by 50 percent and, consequently, wastewater will also be reduced, it will be more concentrated of contaminants, with the advantage of reduce the costs of effluents treatment plant.
Proportionally, similar reduction is achieved on products consumption for initial depuration and steam for its heating, thus bringing to economical savings.
At the same time, besides the ecological and economical advantages, the yarn results much more clean with consequent advantages during the fabric wet finishing processes with a higher final quality.
“CRAFTYROLL” cylinders are definitely the most simple and functional solution for a better washing effect using less water, that is to say, they are the answer to the pressing requests of saving this extremely precious resource, thinking to the future.
It is important to highlight that the requested economical investment to change all the cylinders of one washing box like in Figure 1 with “CRAFTYROLL” ones (Figure 3) is approximately the half of the one requested to install ultrasonic devices, which, by the way, have a limited life. At the same time, “Craftyroll” assures a higher washing efficiency and zero power consumption.
Finally, as an additional application, “CRAFTYROLL” cylinders can be also installed in washing boxes of fabric dyeing and finishing machines, even in textile sectors other than denim production, extending the advantages also to these operations.
Posted: November 21, 2023
Source: MASTER S.r.l.