Caustic Recovery Plant

Project Description

Recovery of Caustic Soda (NaOH) for Textile Effluents:

Caustic is highly alkaline in nature and hygroscopic properties. Caustic soda is also known as 'lye' and it is a white, solid ionic compound consisting of sodium (Na+) and hydroxide ions (OH–). When it is dissolved in water, it forms high pH solution. Caustic solutions have the capability to dissolve organic matter hydrocarbons, and as such chemical. It is widely used in the market to clean process equipment and for other applications.

Caustic is used in many industries in many applications. The biggest users of caustic are the pulp, paper, and textile industry. The Pulp, paper industry caustic is used to purify fibres, cellulosic fibres by removing dissolving all kinds of organic contaminants. In the textile industry, similar application of removing contaminations from rayon fibres before it go to the fabric manufacturing and mercerization.

The mercerization process is charged with caustic is used for treatment of cotton fabric to improve the lustre of the fabric and to improve the affinity to dyes and these are in all of these applications very high concentrated of caustic is used. Uses of Caustic are in the food dairy and beverage industry where caustic is used to clean equipment to make sure that the process equipment is clean for the next batch. In pharmaceutical industry, caustic is used for element to high value components materials and for regeneration of residence in various applications.

In most cases caustic is simply going to drain to the wastewater treatment plant to be treated as part of the overall wastewater of the plant. Caustic is an expensive chemical it's the price varies depending on manufacturing and production, but it's overall between 300 to 900$ per tonne of solid 100% caustic. So, recovering of caustic before it goes to the drain and before it goes to the wastewater treatment plant can save a lot of money to the user. It also saves water energy and overall, the cost saving for the recovery of caustic is to the manufacturer is very high. Also, as exporters, our plants are highly desired across a variety of sectors.

Caustic Soda (NaOH) Recovery Process

Textile Wastewater Treatment
Mercerising Machine Waterman Engineers Australia

It is a caustic when it goes to the wastewater treatment plant it increases the pH of the wastewater often this makes difficult wastewater treatment process. So, before caustic is sent to the wastewater treatment plant it needs to be neutralised and by recovering the caustic before it goes to the wastewater not only the caustic is being saved, but also the acid consumption for neutralisation is being reduced. In addition, the overall carbon footprint of the plant is reduced and there are savings by reducing the flows to the wastewater treatment. It's interesting because the effluent that recovered caustic from the membranes is better than the raw caustic that buy originally. Overall, the reduction from the caustic of organic matter is almost complete the caustic is clear, and the caustic is at the same concentration of what was fed into the membered system.

There is a complete solution, also a family of systems in market for recovering the caustic from mercerization. Available membrane is based on the central product, this is a nanofiltration membrane that not only has an optimal separation property to pass the cost they can retain all the contamination, but it also has the stability that is required to withstand these high pH conditions and often also high temperature conditions. This membrane is a spiral bound element around it. Designed system family the caustic of systems that offer solutions for small medium and large flow rates for recovery of caustic.

These are very harsh conditions. Typical caustic is used in the industry, anything between 1-20% and the temperatures can go as high as 70 degrees centigrade or 160 Fahrenheit. The combination of high concentrated caustic at high temperature or very corrosive harsh most materials fail in short time. The construction materials of the systems and membranes have to be very carefully picked in order to serve and provide long life of product in the industry. Typical life can be between 1-5 years depending on the cost the concentration and depending on what is to be removed from the cost state, but a good number is 1 to 5 years.

Smallest system typically treats around 5000 gallons per day or one cubic metre per hour. It is based on one single pressure vessel with loaded with spiral bound elements. Their largest system is designed to treat 250,000 gallons per day. For larger flow rates, as manufacturers of caustic recovery plants we can either customise the larger system or provide multiple scales of the large systems. Moreover, as a suppliers of caustic recovery plants our products are praised by customers for their dependability, durability, stellar result, and sturdy build.

These automated systems operating mode varies from the small systems to the large systems, the nature of the small systems are more, they are more manual, that's basically what the client wants from a very small system, they operate in a batch mode, meaning that we have a tank it contains caustic, contaminated caustic, we run a batch mode, we treat this caustic and then clean the membrane and move on to the next day.

The medium sized systems have a lot more automation they are kind of what we defined semi automatic, they can run at both batch mode or continuous mode and the large systems are fully automated with full controls and they run in a fully continuous operating mode.

Caustic recovery plants for textile industry
Caustic Recovery Plant for Textile Effluents

Working Principle of Caustic Recovery Plant:

Caustic soda recovery / caustic recovery method with the use of a heat source, caustic is heated to its boiling point, and the vapours produced by boiling are used to heat the weak liquid.

The vapours formed by flashing this heated liquid at a lower pressure are then utilised again. The weak liquid is concentrated to 250-300 gpl in dry Mercerized and 450-500 gpl in wet Mercerized, which can be reused with moderate caustic loading.

Explanation of Working Caustic Recovery System:

Weak Caustic lye, around 5-6 Be (40 - 50 gpl), is collected in a storage tank from the impregnation and washing chamber. The suspended particles, fluff, and other debris are then filtered in a filtration unit. The feed to CRP then runs through a series of preheaters, which use flash vapour from the condensate flashes to preheat the wash liquor, resulting in little steam loss while heating the wash liquor to its boiling point. The liquor in the tubes comes into touch with the steam in heater 1's shell side and begins to boil. The vapour liquor combination enters the flash vessel via a tangential entry, where the vapors separate and enter the 2nd stage shell.

The lower pressure developed with the help of a water ring vacuum pump causes the boiling in the successive effect. The boiling point of the liquor is reduced as a result of the decreasing pressure, and it begins to boil. Due to the pressure differential, the concentrated liquor enters the second heater and comes into indirect touch with the produced vapour, and the process is repeated. A product pump removes the concentrated product from the last step. This is then either stored or purified using a Concentrated Lye purification technique.

The vapour generated at the final stage of the caustic recovery system / caustic soda recovery plant must be condensed. Either hot water or an adiabatic evaporator system is used to accomplish this. Water at room temperature is passed through tubes of an exchanger in a hot water system, where it becomes hot due to vapour. Because this hot water is uncontaminated, it can be safely used in the process or boiler as needed.

The effluent is transported through the exchanger and sprayed in an Adiabatic Evaporator in some circumstances where the hot water created cannot be properly used. Waste heat is lost in the form of vapour, resulting in lower effective steam usage. Also gone is the annoyance of too much hot water.

Who can install this caustic recovery system?

If you are user and that you purchase caustic in large quantities and you dispose caustic in large quantities to your wastewater treatment and most likely also use acid to neutralise this caustic and you use the caustic at 1% concentration or higher, most likely you're a very good candidate for caustic recovery system. Overall, you will save money on purchasing less caustic and let's not forget the environmental impact of recovering caustic. Caustic has a lot of sodium in it and disposing sodium into the environment is not a good thing. It's a global goal to reduce disposal and use of sodium. So, recovering caustic is basically improvement of environmental sustainability and if we can help the environment and save money, this is a win situation.

It Is Worth To Recover Caustic Soda:

Chemicals are used in large quantities by the textile industry to prepare, clean, and colour materials. Caustic soda (NaOH) is one of the most often utilised compounds to improve the strength and shine of cellulosic materials. Cotton is dipped into a concentrated caustic soda solution and additional wetting agents under tension at room temperature during the mercerizing process. The mercerized fabric is rinsed with water at the end of the mercerizing cycle to remove any surplus caustic.

The rinse water, which is mostly weak caustic, is typically produced in large quantities, and if discharged without treatment, can result in a significant loss of caustic soda and a high consumption of acid for neutralisation in the Effluent Treatment Plant (ETP), resulting in large volumes of sludge.

Caustic recovery plants for textile industry

Advantages of
Chemical Recovery:

  • Reduced waste caustic discharge & effluent treatment costs
  • Savings from reduced purchases of caustic soda
  • Saving in energy cost for heating water
Caustic Waste Treatment

Why Caustic Recovery Plant is Necessary?

Caustic treatment system

After food, cloth is the second most important need of humans. The textile industry's fundamental milestones are producing fibres and then processing them to manufacture clothing.

Because of this unavoidable need, the textile industry has developed at a quicker rate as the population and living standards have risen over time. As a result, the textile industry has established itself near countries' biggest export and import markets.

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