We are living in a highly industrialized world today. As we are enjoying its benefits, the responsibility of safeguarding the environment also increases. Recycling or recovery of useful chemicals from waste is one of the primary ways to achieve the valuable chemicals and simultaneously protect the environment from pollution, and that’s where the Caustic recovery system can play an important role.
Caustic is mainly employed in the Industrial cleaning of food-dairy-metallic components because of its soapy and alkaline nature, which also neutralizes acidic residues in the process. As a result, a high volume of caustic waste is generated every day in Pharmaceutical, Textile, Dairy, etc. industries. Typically the caustic concentration is about 1-2% but varies from <1% to >5% caustic. The caustic used may or may not contain additives like surfactants, chelating agents, buffers, etc. Such high caustic waste is not feasible to release into the environment as it increases the COD. Moreover, the price of caustic is also increasing and hence, recovering the used caustic from waste is essential.
Currently, Caustic is recovered by two methods, by Evaporation and Membrane separation. Evaporation has some drawbacks such as difficulty to scale up, High energy demand, High Opex, Capex, Maintenance, and monitoring cost. On the contrary, Membrane systems are a greener approach towards caustic recovery. The Opex and Capex of membrane systems are low with the versatile ability to scale up and customize the membrane system. Minimal Maintenance and monitoring cost makes it economically feasible to cater in the daily operations.
The typical caustic recovery process using a membrane system has following steps:
- The dirty caustic stream or streams are collected and sent to dirty or spent caustic storage tanks.
- Either entering or exiting this storage tank the dirty caustic should be screened to remove the large particulates. The screen size is typically about 400 microns.
- If removal of suspended solids is desired then the dirty caustic is sent to the Microfiltration system to clarify the caustic with suspended solids concentrated. If this quality of caustic is acceptable for reuse then there are no other processing steps.
- If removal of the dissolved solids is also required then the clarified caustic from Microfiltration is sent to Nano Filtration System. The NF System purifies the clarified caustic and concentrates the dissolved contaminants
- In case of no suspended solids, the dirty caustic is directly passed to the Nanofiltration system by-passing the Microfiltration stage.
The first widely used membrane type for caustic recovery was ceramic membranes. Ceramic membranes are not degraded by the pH and temperature of the dirty caustic stream. Their tubular configuration is suitable for removing and concentrating suspended solids. While ceramic membranes can concentrate suspended solids to thick slurries the commercial maximum suspended solids concentration is usually somewhat lower, depending on operational and cost considerations. Ceramic membranes then (as now) were limited to MF and UF pore sizes. The process development work done at the time showed that a ceramic membrane with a pore size of 0.1 microns to 0.02 microns produced a clarified caustic without any suspended or colloidal solids. The membrane is not tight enough to remove dissolved contaminants (sugars, low molecular weight carbohydrates, proteins, peptides, color compounds, etc.) so they will stay with the clarified caustic. This quality of caustic for reuse was acceptable to many food and beverage processing facilities and was commercially implemented.
Now we have NF membrane available which can be operated between pH 1-14 and hence can be more beneficial to get highly clarified/purified caustic spent which can be recycled & reused.
We at Nilsan Nishotech, Use a scale-down model for providing customized solutions for our valued clients. For Caustic recovery, Lab trials are performed using MF and NF filtration systems to check the feasibility of the project on an industrial scale. Our team of Experts and Researchers does a thorough analysis of the caustic waste to check various parameters such as solid contents, Caustic concentration and decide the way forward for efficient recovery.
Overall, Membrane technology is the future of caustic recovery and we at Nilsan Nishotech, have versatile experience in this field.
Advantages of using our Membrane systems
- Energy-efficient process
- Low maintenance and operating costs
- Versatile systems – can be used for multiple products
- Inbuilt CIP/SIP capabilities
- Sanitary System design system
- No effluent discharge
- Skid-mounted compact systems & less footprint.
- Attractive CapEx and OpEx over conventional separation/purification methods
- Wide range of membranes – In MF, UF, NF, RO – in different MOC, and in different module designs to meet specific processes.
