Heat recovery in the textile dyeing and finishing industry: lessons from developing economies

Abstract

Many developing countries, including African ones, look forward to developing strong integrated textile industries to add value to already-available raw materials. Dyeing and finishing activities are, however, energy-intensive. In many cases, these depend on imported fossil fuels. By turning to heat recovery, significant cost savings can be achieved improving profitability and competitiveness. The techniques and technologies of heat recovery from waste water and exhaust air are analysed. Experiences prove that in most cases heat recovery requires low investment and has a low payback of normally less than 2 years. The case of the Mauritian dyeing and finishing industry is highlighted, including the possible use of a low-cost heat recovery unit made from indigenous resources.

Photocatalytic Degradation of Dyes: An Overview

“…Among the various waste water treatment procedures, dye removal has occupied a prominent place. Because of aesthetic and environmental concerns, the degradation of dyes in the effluent water of textile dyeing and finishing industry has been most significant [37]. The semiconductors especially TiO2 and ZnO are employed as nanorods, nanospheres, thin porous films, nanofibers and nanowires or supported on polymeric films [40].…”

“…The size and Phase (Anatase) are important. Adsorption of the dye on the catalyst surface is also important (Freundlich isotherm) [34] TiO2 Indigo Acid Red 14 14ARI14) The azo and Sulphonate groups determining factor for degradation [37] SiO2 nanoparticle doped with Ag and Au Methyl Red OH radical produced initiates and also sustains the degradation of the dye [38] Titanium dioxide Emerald Green Degradation rate constant depends on pH [39] ZnO and TiO2…”

Waste Heat and Wastewater Recovery in Textile Processing Industry: A Case Study of Adopted Practices

“…up to 80-90 °C, which after the application is directly disposed of as hot wastewater. To reduce the waste generation at the source the best approach is the onsite reuse of the hot wastewater within a similar application [20,21]. This could be achieved with collection and screen filtration of the hot wastewater from one stage of the process and its reuse in the other stage of the same process, as shown in Fig.…”

Waste Heat Recovery in Textile Industry: A Review

“…The latter is generally preferred to the former because its heat transfer efficiency is higher by 3to5 times. Plate heat exchangers require less capital investment than shell-and-tube heat exchangers made of materials like high-grade stainless steel, essential to resist corrosion due to textile waste water [4].…”

“…Subsequently, cooling water is collected and re-utilised, thus, recovering heat and water. Under the most favourable conditions, cooling water recovery has been reported to have a payback period of 12 months [4].…”