Improvement of Phase Change Materials (PCM) Used for Solar Process Heat Applications.

The high intermittency of solar energy is still a challenge yet to be overcome. The use of thermal storage has proven to be a good option, with phase change materials (PCM) as very promising candidates. Nevertheless, PCM compounds have typically poor thermal conductivity, reducing their attractiveness for commercial uses. This paper demonstrates the viability of increasing the PCM effective thermal conductivity to industrial required values (around 4 W/m·K) by using metal wool infiltrated into the resin under vacuum conditions. To achieve this result, the authors used an inert resin, decoupling the specific PCM material selection from the enhancement effect of the metal wools. To ensure proper behavior of the metal wool under standard industrial environments at a broad range of temperatures, a set of analyses were performed at high temperatures and an inert atmosphere, presenting a thorough analysis of the obtained results.

High chrome exhaustion in a non-float tanning process using a sulphonic aromatic acid.

Tanning processes performed in drums consume large amounts of water and chemicals, most of which end up in the wastewater. This study explores an alternative approach at an industrial scale to the traditional pickle-chrome tanning method. The new method replaces formic and sulphuric acids with sulphonic aromatic acid. Because it is done without float, there is a sizeable reduction in the amount of added salt and chrome salt as well as an increase in temperatures at the end of the tanning process. From an environmental perspective, the new method offers important advantages. For instance, there is no float addition in the tannage. Also, there are reductions of 94% and 99%, respectively, in the discharge of chlorides and chrome, as well as a 75% reduction in the residual float. Our financial assessment demonstrated that the new method is 42% cheaper than a traditional approach.

Minimization of the environmental impact in the unhairing of bovine hides.

This study tests an alternative method to the traditional unhairing method used during the process of tanning the hides. The new method is based on the substitution of sodium sulfide by hydrogen peroxide as an unhairing agent in both hair recovery and recirculation of the floats employed in the process. The properties of the hides obtained using the two methods have been compared and the results indicate that those hides have similar physical, chemical, and organoleptic properties. However, the differences existing from an environmental point of view are significant. These include reductions of water consumption (approx 70%), chemical oxygen demand (approx 35%), toxicity (98%) and total kjendhal nitrogen (50%). Also, the risk associated with the production of hydrogen sulfide is eliminated, which implies a great improvement in terms of safety for the workers. Given the large amounts of water and chemical pollution discharged in the process, the reductions in absolute values represent a significant improvement. A financial assessment was carried out to demonstrate that the proposed new system is 16% more economic than the traditional one.

Minimization of the environmental impact of chrome tanning: a new process with high chrome exhaustion.

In all tanning technology operations wastes are generated. These reach the environment as residual waters, solid and liquid waste as well as atmospheric emissions and odours. This study tests an alternative method to the traditional tanning method at an industrial level. The new method is based on tanning without float and by significantly increasing the temperature at the end of the tanning process. The properties of the leathers obtained using the two methods have been compared and the results indicate that those leathers have similar physical, chemical, and organoleptic properties. However, the differences existing from the environmental point of view are significant. It is not necessary to use clean water for this tanning. Moreover, there is a 75% reduction of the residual float, a 91% reduction of the chrome discharged, and a 94% reduction of the chlorides discharged. A financial assessment was carried out to demonstrate that the newly proposed system is 32% more economic than the traditional one.