STUDY OF OPERATION AND MAINTAINENCE OF A CAUSTIC RECOVERY UNIT

Abstract

Caustic soda also known as sodium hydroxide is a chemical widely used by multiple industries all over the world. One such industry is the textile industry which utilizes caustic soda in the wet processing of fabric to improve the luster and quality of the fibers. The effluent from these processing sections contains wastewater with a high amount of sodium hydroxide, which remains unreacted. This project focuses on the recovery of caustic soda from these wastewater streams to reduce the costs spent by the industry in buying the raw material. The main objective of this project is to concentrate a dilute five percent lye solution up to forty percent, which can then be reused as raw material for the processing sections. Different concentration enhancing techniques have been described in detail and the importance of using the evaporation method is highlighted. A triple effect evaporator system is designed manually and simulated on Aspen HYSYS to compare the results. The user for triple effect evaporator what is the concentration of caustic solution provides a high steam economy of two point three kilograms of water evaporated per kilogram of steam with a low capital investment and payout period of 2.3 years. Three thousand five hundred kilograms per hour of water is obtained from a four thousand kilograms per hour Caustic feed solution. The Caustic Recovery Unit serves a dual purpose of enhancing the concentration as well as the generation of hot water minimizing energy losses.