How to Make Solvent Recovery Cost-Efficient

Do you Know Why Solvent Recovery is Essential for the Process Industries to Minimize the Manufacturing Cost?

If you get into the details of the manufacturing processes practiced in the process industries, you’ll find most of them use solvents. Why?

It’s because of their dissolving capacity. They’ve the capacity to dissolve other materials in them.

Solvents Usage

It doesn’t matter whether you’re dealing with Chemical Industry, Pharmaceutical Industry, Food and Agro-based Industry, Formulation Industry or any other type of Process Industry.

Solvents are important. Isn’t it?

But when you study the details of their usage, you’ll notice an important fact. In most of the manufacturing processes, they’re not consumed. They never get changed at the molecular level.

When you talk about the key starting raw materials, it gets incorporated in the final products either completely or partially. Of course, sometimes there’re molecular changes and some times they get incorporated s such.

When it comes to the reagents which are used in chemical reaction-based manufacturing processes, it’s different. Though they get changed at the molecular level, in most of the cases they never get incorporated in the final product.

Let’s come back to the solvent consumption in process industries. In most of the process industries they help the manufacturing processes by involving directly, but not get consumed.

And when you talk about the formulation industry, it’s a different story. Different types of solvents are used in making the formulation products to dissolve the active ingredients and become a part of the finished formulation. In short, they get consumed completely.

But have you ever thought what happens to the solvents after they’re used? It’s especially when they’re not consumed and don’t become the part of the final products!

So what happens to them?

Spent Solvent Streams

In fact, they come out of the manufacturing process sections as waste or spent solvent streams.

But the question is what to do with those spent solvent streams?

Will you allow them to go to the waste treatment plant?

No, you can’t. Why?

It’s because of two reasons:

• You know solvents are expensive. That’s why you can’t waste them and increase the manufacturing cost. Right?
• And when the solvents contaminate the waste water, the pollutant load gets increased. And naturally the waste treatment becomes difficult. That’ll result in high waste treatment cost and difficult treatment process. And of course, the overall manufacturing cost will go up.

Will you allow it to happen. No, you can’t.

So, how to address this issue?

Efficient Solvent Recovery is Important

The best option is to recover the solvents from the spent solvent streams and make them suitable for recycling in the manufacturing processes.

Then what about the industrial facility to recover the solvents?

If you get into the details of solvent recovery operations in the process industries, you’ll find most of them use dedicated solvent recovery plants.

And of course, the solvent recovery system must be efficient to recover the solvent to the maximum extent.

Equally important aspect is to achieve the recovered solvent quality suitable for recycling in the manufacturing process. It’s important. Because unless the recovered solvents are not recycled in the manufacturing, it’ll not serve any purpose.

But before getting into the details of the solvent recovery system, let’s talk about the solvents.

Know about the Solvents

As we’ve discussed earlier, solvents are important because of their dissolving capacity. They’ve the capacity to dissolve other materials in them. And most of the solvents are liquids at room temperature. They’re mostly petrochemical based and are expensive.

Based on their nature you can divide the solvents into two major categories:

Polar Solvents

The polar solvents like water. They mix well with water because of their higher affinity towards water.

Non-Polar Solvents

The non-polar solvents dislike water. That’s why highly non-polar solvents have very low miscibility in water.?

Even if they’re expensive, you don’t have any other choice. It’s because of the manufacturing process demands, it becomes necessary to use them in process industry.

So, you must know why they’re important to Process Industry.

Usage in Process Industries

Solvents play a very important role in chemical reactions, product separation, and purification very important in chemical reaction based process industries.

Reaction Processes

When the reactants are allowed to get dissolved in the solvent completely, the molecules come in close contact with each other and react to make the product molecule. Solvents help prepare homogenous solutions so that the reactions proceed at ease.

Of course, the solvent never get consumed in the reaction unlike the reactants, they help the reaction process.

Separation and Purification Processes

Only synthesizing the products by reacting the raw materials (reactants) is not enough. You need to isolate the product from the reaction mixture and purify it before it becomes suitable for the customers.

That’s why you need a combination of separation processes. The solvents dissolve the product molecules and recover them from the reaction mixture.

You know different solvents have capacity to dissolve different materials. One material may have more solubility in one solvent, but zero or very little solubility in other solvent. In fact, this aspect is utilized in purification processes like crystallization to purify the product molecules.

Other Process Industries

Some of the applications are mentioned below:

• In antibiotics fermentation industry suitable solvents are used recover the products from the fermented broth and purify them.
• In vegetable oil industry, oil extracting solvents like Hexane are used to extract the vegetable oil from the oil seeds using solid-liquid extraction process.
• You need solvents to make formulation products like agrochemical formulations, paints and coatings formulations, adhesives formulations.

Let’s come back to the solvent recovery system. In order to minimize the manufacturing costs, you need to make the solvent recovery system cost efficient. Right?

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For that you must know where the spent solvent streams are getting generated in your manufacturing operations and how much. Why?

Because unless you know the details in quantitative terms, you can’t take any corrective action.

So what to do?

That’s where the solvent balance comes into the picture.

Solvent Balance is the Starting Point

As you’re using solvents in your manufacturing process, the input mass will be equal to the output mass. Of course, the quantity and concentrations of the solvent in different solvent streams will be different. But the total solvent mass will remain same.

That’s where the solvent balance takes advantage of this concept. So, when you do detailed calculations across the manufacturing processes you come to know a lot about the spent streams.

As we’ve mentioned earlier, efficient solvent recovery system is important.

Make the Solvent Recovery System Efficient

In order to make the solvent recovery efficient, it’s important to segregate the spent solvent streams based on their composition and quantity. Why?

It’s because you need to optimize the solvent recovery process with respect to improving the recovery efficiency, minimize the losses, reduce the recovery costs and achieving recovered solvent quality.

Ensure that you don’t mix more than one solvent in any solvent stream and keep them separate, even if the quantities are small. Why? Because mixed solvent separation is difficult and expensive and invariably results in high solvent recovery cost.

When you get into the details of solvent recovery systems in the process industries, you’ll find most of the solvent recovery plants have three major areas:

Storage of Spent Solvent

You use spent solvent tanks to receive the spent solvent from the production plant and store for recovery operations.

Solvent Recovery Facility

It’s the solvent recovery facility is where the major operation of solvent recovery is carried out. To minimize the recovery costs, in most of the recovery processes distillation - including simple, fractional, azeotropic, extractive distillation processes – and liquid-liquid extraction processes are used.

Storage of Distilled Solvent

Distilled solvent storage tanks are used store the distilled solvents recovered from the solvent recovery systems. Based on the demands from the production plant the recovered solvent is provided.

Of course, the quality of the recovered solvents is of utmost importance. That’s why the job of solvent recovery is not only to recover the solvents at high efficiency but also to achieve the purity required by the manufacturing processes.

Let’s now get into the details of minimizing the solvent recovery costs

Minimize the Solvent Recovery Costs

You can implement many improvement initiatives to minimize the solvent recovery costs.

Some of them are mentioned below.

Go for Heat Economization

Most of the solvent recovery operations are based on distillation processes. Some of the operations are based on batch distillation and some use continuous distillation. Some of the processes are based on simple distillation whereas some us fractional distillation.

Of course, some of the solvent recovery processes are based on special distillation like extractive distillation and azeotropic distillation. Sometimes special extraction processes become necessary for achieving the solvent quality required for the manufacturing operations.

Irrespective of the processes used, in most of the processes heat transfer is necessary. That’s why efficient heat transfer becomes critical for making the system efficient.

When you consider the energy cost, efficient heat transfer becomes more important. In fact, heat integration along with system waste heat utilization can result in significant cost savings. Why?

Because in a distillation systems different process streams have different temperatures. When you use high temperature process streams to heat up the low temperature process streams, you save both the heating utility as well as cooling utility.

That’s what is nothing but Heat Economization.

Proper Heat Economization can result in reducing the manufacturing cost and make the distillation system cost-efficient.

Minimize the Vent Losses

Distillation operations in solvent recovery plant use solvent boiling operations. The possibilities of solvent losses are high where solvent boiling operations are carried out. Why?

Because when the solvent is boiled, liquid is converted into vapor and you condense it to get back it as liquid. If the solvent vapor is not condensed completely, some solvent vapor will get lost in the vent. So how to avoid that?

For that you need an effective vapor condensing system. Right?

That’s why in order to minimize the vent losses you need make the vapor condensing system efficient.

So of the initiatives you can consider are mentioned below.

Primary Condenser

It helps to install well designed Primary Condenser for condensation of the major part of the solvent vapor (designed for hundred percent condensation). Of course, for economic reasons you need to use optimized cooling utility.

Vent Condenser

It helps to install well designed Vent Condenser for condensation of the solvent vapor which gets escaped from the primary condenser. In fact, this is a safety equipment. It’s necessary to avoid the vent loss in case the primary condensation fails to perform.?

Optimized Cooling Utility

It’s preferable to use the cooling utility of lower temperature than that used for primary condensation. If required, you can go for two stage vent condensation based on the solvent properties.

Ensure that the coolant fluid flow is adequate in both primary and vent condensation systems. Any issue in utility supply and distribution can create problems. Due to the inadequate availability of the cooling fluids, the heat transfer will suffer badly resulting in solvent loss.

In fact, all the vent lines of solvent handling vessels and equipments must connect to a centralized vent condensation system. Ensure that the centralized system is capable of handling the solvent vapors adequately.

When it comes to the utility cost, ensure that you use the right cooling utility with respect to the cost. The utility must match with the process requirements. Any deviation in utility usage can result in increasing the manufacturing cost and affecting the manufacturing performance badly.

Avoid Solvent Loss in Distillation Systems

If you get into the details of the solvent recovery operations, you’ll find the possibility of solvents getting into the waste water treatment plant is higher in continuous fractional distillation systems. Why?

It’s because the bottom outlet of most of the fractional distillation systems especially when you’re distilling aqueous spent solvent streams, is itself a waste water steam. In normal operations, the bottom outlet will contain negligible amount of solvents.

But if the distillation systems are not operated optimally or the equipment and instruments are not performing properly, there’s a possibility of significant quantity of solvents getting lost in the bottom outlet.

So, it’s essential that the design and operations of the distillation systems are proper. In fact, close monitoring of the solvent recovery operations can help a lot in minimizing the losses and making the solvent recovery system cost-efficient.

Let’s Conclude

When you’re interested in making your Process Industry profitable and sustainable, you must make efforts to reduce the manufacturing cost. Why?

Because reducing the manufacturing cost of your products significantly, is the single most important improvement initiative. In fact, it's no longer an option. It's a must!

Most of the Process industries use solvents for manufacturing their Products. In most of the industries, unlike the key raw materials, they’re never consumed in the manufacturing processes.

Once used, the solvents come out of the manufacturing process sections as spent solvent streams.

But you can’t allow them to go to the waste treatment plant for treatment and increase your manufacturing cost.

You must Recover the Solvents Efficiently from the Spent Solvent Steams. Only Efficient Recovery is not enough. You must achieve the Recovered Solvent Quality suitable for Recycling in the Manufacturing Process. And above all you keep the Solvent Recovery Cost at Minimum Level.

But how to make the Solvent Recovery Cost-Efficient?

That’s where the Process industry innovations enter into the picture.

Process industry innovations can help you make the Solvent Recovery Cost-Efficient and reduce the manufacturing cost of your products significantly.

Once you implement the innovation initiatives in your manufacturing business covering all the critical functions, you yourself will be convinced that it produces results.

As we've discussed earlier, you can make the Solvent Recovery Cost-Efficient by implementing improvement initiatives.

Some of them are mentioned below:

• Solvent Balance is the starting point.
• Make the Solvent Recovery System Efficient
• Go for Heat Economization
• Minimize the Vent Losses
• Avoid Solvent Loss in Distillation Systems

In today's competitive business environment, making the Solvent Recovery System Cost-Efficient is not an Option. It's a Must.

But implementing the improvement initiatives calls for industrial experience and techno-economic expertise.

Perhaps you can consider taking the help of Industry Experts to make the process fast and effective.

What is your experience in Making the Solvent Recovery Cost-Efficient?