#solvent extraction

Radical desalination approach may disrupt the water industry

Hypersaline brines -- water that contains high concentrations of dissolved salts and whose saline levels are higher than ocean water -- are a growing environmental concern around the world. Very challenging and costly to treat, they result from water produced during oil and gas production, inland desalination concentrate, landfill leachate (a major problem for municipal solid waste landfills), flue gas desulfurization wastewater from fossil-fuel power plants, and effluent from industrial processes.

If hypersaline brines are improperly managed, they can pollute both surface and groundwater resources. But if there were a simple, inexpensive way to desalinate the brines, vast quantities of water would be available for all kinds of uses, from agriculture to industrial applications, and possibly even for human consumption.

A Columbia Engineering team led by Ngai Yin Yip, assistant professor of earth and environmental engineering, reports that they have developed a radically different desalination approach -- "temperature swing solvent extraction (TSSE)" -- for hypersaline brines. The study, published online in Environmental Science & Technology Letters, demonstrates that TSSE can desalinate very high-salinity brines, up to seven times the concentration of seawater. This is a good deal more than reverse osmosis, the gold-standard for seawater desalination, and can hold handle approximately twice seawater salt concentrations.

Unique interface and unexpected behavior help explain how heavy metals act

Refining platinum, plutonium, or certain other metals often depends on how the metal behaves at liquid interfaces. The challenge? Scientists have limited ways to analyze the details of liquid interfaces. Now, researchers described in significant detail how water molecules surround a platinum-based ion. Their description includes an unexpectedly complex structure that forms on the liquid's surface. The team noticed no less than three different forms of water wrapping around the ion. The complex water structure is unexpected and it creates unusual behaviors compared to those observed around smaller and lighter ions under similar conditions.

Refining platinum and other precious metals involves moving the desired metal from one liquid to another. But little is known about how that transfer works on the molecular scale. This work helps explain how platinum and other heavy metals move and react across liquids.

Solvent extraction, the go-to technology for reprocessing nuclear waste or refining rare earths and precious metals, involves the preferential transfer of a targeted chemical species between two immiscible phases through a liquid-liquid interface. Relatively little molecular-scale information is known about the mechanism or mechanisms of this transfer across an interface. Why? In large part, the knowledge gap is because most experimental probes cannot interrogate liquid interfaces directly. Even the best surface sensitive probes are only sensitive to limited components of interfacial structure.

A base oil solvent extraction plant is a symphony of complex engineering, where each piece of equipment plays a critical role in transforming crude oil distillate into a high-purity base oil. While the chemical process of solvent extraction is fascinating, it is the physical machinery that brings this science to life on an industrial scale. Let's take a tour of the essential machinery that forms the backbone of a modern solvent extraction plant.

1. The Extraction Column: The Heart of the Process

This is where the core separation magic happens. The most common type is the Rotating Disc Contactor (RDC). This tall, vertical column is designed to maximize contact between the heavy oil feedstock (entering near the top) and the light solvent (entering near the bottom). Inside, a central shaft with rotating discs creates a turbulent mixing zone, shearing the fluids into small droplets to provide a vast surface area for the solvent to selectively dissolve the impurities. Other designs like packed or sieve tray columns are also used, but the RDC is renowned for its efficiency and handling capability.

2. The Solvent Recovery System: The Circulatory System

Efficiency in a solvent plant is paramount, and this system is dedicated to recycling the valuable solvent. It primarily consists of distillation columns:

Raffinate Stripper: The purified oil stream (raffinate) leaving the extraction column is saturated with solvent. It is heated and fed into a raffinate stripper, where steam or a vacuum is applied to evaporate and recover the solvent from the oil.

Extract Stripper: The impurity-rich stream (extract) undergoes the same process in its own dedicated extract stripper, which is often more robust due to the heavier nature of the extract.

Solvent Dehydration Column: Water is an enemy in this process. Any moisture that enters the system is removed in a dedicated dehydration column to maintain the solvent's purity and effectiveness. The recovered, dry solvent is then cooled and recycled back to the extraction column.

3. Heat Exchangers and Furnaces: The Temperature Managers

Temperature control is vital. A network of shell and tube heat exchangers is used throughout the plant to pre-heat and cool various streams by transferring heat from one process stream to another, dramatically improving energy efficiency. For the high temperatures required in the strippers, direct-fired furnaces or fired heaters are used to bring the oil-solvent mixtures to their precise boiling points.

4. Pumps, Vessels, and Tanks: The Support System

No plant can operate without this essential infrastructure:

Pumps: High-pressure centrifugal pumps are the workhorses, moving fluids throughout the entire process—from feedstock charge pumps to solvent circulation pumps and product transfer pumps.

Storage Tanks: Large atmospheric tanks are needed to store incoming feedstock, the finished raffinate (base oil) product, and the recovered extract.

Surge Drums and Accumulators: These smaller vessels are placed strategically to ensure a steady flow of material, dampen pressure fluctuations, and provide temporary holding capacity between major units.

5. The Solvent Conditioning System: The Guardian

Over time, the solvent can degrade or become contaminated. A small side-stream of the circulating solvent is continuously sent through a solvent conditioning system. This may include filters to remove particulates and a clay treator or a small regenerator to remove degradation products and acids, ensuring the solvent maintains its high selectivity and purity.

Integration is Key

A solvent extraction plant manufacturer is a company that designs and manufactures equipment used to extract oil from seeds and other materials by using solvents like hexane. These plants are widely used in the vegetable oil industry as they have high extraction efficiency and can process a variety of seeds including soybeans, sunflower, rapeseed, and more. Solvent extraction is a popular method for oil extraction as it can extract up to 99% of the oil from the seeds

Supercritical fluid extraction (SCFE) is a broadly used process to obtain specific compounds (called target molecules or simply products) from plant based raw materials. Following are some of the other processes used for extraction:

Hydrodistillation & Steam Distillation

Solvent Extraction

Microwave-assisted Extraction

Mechanical Pressing

Ultrasound-assisted Extraction

Detente Instantanee Controlee (DIC)

Hydrodistillation boils the solution with the dissolved raw material. Different products from the raw material boil off at different temperatures and are separately collected on condensation at these respective different temperatures. A variant of hydrodistillation is steam distillation. Both use heat and therefore can alter the chemical structure of the product. This lowers extraction purity.

Flavours and fragrances extracted using supercritical fluid extraction (SCFE), for example, are more similar to the original product than those obtained via hydro or steam distillation.

Solvent extraction uses solvents such as hexane, acetone and others to obtain the products. The solvent first dissolves the product from the raw material. Thereafter, the solvent and product are separated to obtain the product. The solvent does not completely separate from the product i.e. there is some contamination. Again, this affects the purity of extraction.

Apart from purity, another issue with solvent extraction is the lack of selectivity. When extracting astaxanthin from microalgae, solvent extraction using hexane or acetone provided lower yields. This is because these solvents cannot differentiate between astaxanthin and the astaxanthin-lipid combine. Using supercritical fluid extraction (SCFE) for the same purpose delivers more than double the yields as obtained from solvent extraction.

Properties of the supercritical fluid (SCF) best explain the plus points of supercritical fluid extraction (SCFE). An SCF is a fluid with its:

Pressure above its critical pressure; and

Temperature more than its critical temperature.

In the state, the SCF’s properties can:

Be similar to that it its liquid state;

Resemble those of its gaseous phase; or

Be a mix of these two phases.

Changing the pressure alters the solvent power of the SCF. Solvent power is the capacity of the SCF to dissolve a product from the raw material. At a certain pressure, the SCF dissolves one particular product from the raw material. Few if any of the other products get dissolved and those too in minimal quantities.

Oleoresins are a kind of spice that occur naturally in plants as a blend of oil and resin. They are in great demand on account of their multiple health benefits. However, they can deliver their positive health effects only if the method used for oleoresin extraction and / or oleoresin oil extraction separates them in their purest possible form. Any change in chemical composition during extraction and their health benefits get negatively affected.

Medicinal properties of oleoresins make them capable of fighting off the following conditions:

Cancer

Rheumatism

Colic Flatulence

Diarrhea

Joint Ache

Infections in the Urinary Tract

Muscle Pain

Two main methods used for oleoresin extraction as well as oleoresin oil extraction are:

Supercritical Fluid Extraction (SCFE)

Solvent Extraction

SCFE is a highly targeted process in that it extracts only the required compound. This required compound is called the target molecule or simply the product. In this case, the target molecule is the oleoresin in question. The reason for its precise nature lies in the mode of operation which we shall see later.

Solvent extraction, on the other hand, can leave behind residues. It uses a solvent to first dissolve the product. The solvent is then separated from the product via evaporation or purging or other such methods. The solvent does not completely separate from the product, thereby contaminating it.

Hydrodistillation may also be used for oleoresin extraction and oleoresin oil extraction. The product is first dissolved in water and the solution is boiled. At one particular temperature, the product will boil off and is collected on condensation. Heat used in the process can however change the chemical composition of the product. Oleoresins are vulnerable to heat, light, and oxidation.

SCFE uses a supercritical fluid (SCF). This is a fluid at a:

Pressure above its critical pressure; and

Temperature above its critical temperature.

Interestingly, the solvent power or the capacity of the SCF to dissolve a particular product can be adjusted via pressure. The solvent power is high at elevated pressures and low at reduced pressures. At a certain pressure, the SCF will dissolve only a certain oleoresin. Few other compounds from the raw material will dissolve in it and that too in negligible quantities. When the pressure is lowered, the product will come out of solution from the SCF.

Flavours find application in the beverages, bakery, confectionary, dairy, and convenience foods industry. Fragrances are employed by the cosmetics, toiletries, soaps, detergents, and fine fragrance businesses.

User preferences over the world are shifting in favour of products with pure and natural ingredients. Extraction of flavours with the carbon dioxide (CO2) supercritical fluid extraction (SCFE) process preserves the purity of the extracted molecule. It is for this reason that the process is preferred in flavour and fragrance extraction.

There are more than 250 species of plants from which over 500 natural raw materials are extracted for the flavours and fragrances industry. Among the most in-demand flavours and fragrances are rose oil, tuberose absolute, angelica root oil, jasmine absolute, ambrette seed oil, and orange flavour oil.

On the global scale, the flavours and fragrances market is forecasted to grow at a CAGR of 4.3% from 2019 onwards and reach $36.6 billion by 2024. Natural ingredients are widely regarded as safer and healthier. The demand for natural ingredients in products is an important factor expected to propel the market to greater and greater heights. The dairy and beverage industry is increasingly resorting to the utilization of biotic elements. Flavours are also finding increasing application in the dietary supplement, pharmaceutical, and nutraceutical businesses. And with expanding disposable incomes, customers are more than willing to spend extra for these natural products.

Heating a fluid to above its critical temperature and hiking its pressure to more than its critical pressure takes it to the supercritical stage. Properties of a supercritical fluid (SCFE) are very peculiar in that they can be similar to that of a liquid, a gas, or somewhere in between these two states. For example, its density is higher as that of a liquid. Solvent power is directly proportional to density. However, its surface tension and viscosity is low, similar to that of a gas. This helps it penetrate deeper inside porous raw material.

An interesting point about the density and solvent power of SCFs is that they can be controlled through minor changes in pressure and temperature. By precisely adjusting the pressure, the SCF can be made to extract one particular target molecule with little or no inclusiont of other molecules. In short, SCFE extracts molecules in their relatively pure form - exactly what the market is asking for.

Conducting SCFE with carbon dioxide (CO2) i.e. CO2 SCFE adds another layer of benefits. CO2 has a low critical temperature of 31.1 deg-Celsius. Therefore, CO2 SCFE process temperatures for flavour and fragrance extraction is not very high. This prevents the thermal degradation of the target molecule, transforming into better purity. Then again, the critical pressure of CO2 is 73.9 bar. This is not very high and, again, requires the use of not very high process pressure.

Effect of Oil Extraction Method on the Functional Properties of Biodiesels of Selected Oilseeds

Gbashi M. Samuel | Yanshio T. Emmauel | Kingsley N. Nwankwo ""Effect of Oil Extraction Method on the Functional Properties of Biodiesels of Selected Oilseeds""

Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-3 | Issue-6 , October 2019,

URL: https://www.ijtsrd.com/papers/ijtsrd25252.pdf

Paper URL: https://www.ijtsrd.com/engineering/mechanical-engineering/25252/effect-of-oil-extraction-method-on-the-functional-properties-of-biodiesels-of-selected-oilseeds/gbashi-m-samuel

engineering journal, open access journal of chemistry, indexed journal