Dyebath Reuse In Textile Processing

DYEBATH REUSE Dyebath reuse is not a new development. It was in fact developed way back in 1970s in USA, when energy prices had rocketed up tremendously. We are using this technique successfully for white & light shades in three jet dyeing machines from the last one year, with significant reduction in effluent load as well as costs. Principle : In polyester dyeing more than 97% exhaustion of disperse dyes takes place, where as other additives generally remain in the bath. In practice this spent liqour is discarded as effluent. "DYEBATH REUSE" involves : i) storage of this exhausted dyebath in an overhead tank, ii) analyze it for remaining chemicals & dyes, iii) reconstitute if & as required & iv) the reuse it for subsequent batch. Design: An over head S.S. tank of 600 lts capacity is required for a low liqour type (450 lts liqour) jet dyeing machine to avoid splashing. Additional valves & piping is to be done as shown in the fig. The tank is kept about five feet above the Jet dyg. m/c. with the help of adequate supporting structure. The tank should have two drains; one leading back to the jet for reuse & another for final discharge after a certain level of reuse is achieved. A pump for lifting the liqour to the O.H. tank can be avoided if it is drained at 110*C under pressure. Environmental benefits :- more than 85% reduction in COD & Suspended solids is achieved with reuse ratio of 1:10in white shades. The water consumption also goes down by 90%. Economics : The chemicals, steam, electricity & water + effluent costs can be reduced by 88%, 40%, 10% & 80% respectively. The payback calculations are as shown below: COST OF 3 OVERHEAD TANKS EXTRA VALVES PIPING & STRUCTURE MAINTENANCE:-

Rs53,000 Rs5,500 Rs13,000 Rs7,000

TOTAL EXPENDITURE :SAVINGS IN DYEBATH REUSE/MONTH :PAYBACK PERIOD IN MONTHS :-

Rs78,500 Rs8,500 9-10 MONTHS