Keys to more efficiently cooling sodium citrate

And the role that vertical heat exchangers can play in improving production

Author: Jamie Zachary

Sodium citrate can be found in many areas of our daily lives. It’s represented in what we eat, whether that be ice cream or bratwurst. It’s what gives club soda both its sour and salty flours. It’s what allows cheese to melt without becoming greasy. It’s even found in personal care products, from baby wipes to detergents.

Sodium citrate also plays an essential role in many industries. It can be used to prevent donated blood from clotting in storage, or even as an essential ingredient in many COVID-19 vaccines.

Sodium citrate is the salt of citric acid. It is produced through the neutralization of citric acid with high purity sodium hydroxide or carbonate. The solution then goes through a crystallization process, followed by a drying and cooling stage.

The drying and cooling stage represents a key component of this process by maintaining product quality as well as suitability for downstream equipment such as screening, packing, storage and transport.

We recently caught up with Gerald Marinitsch, Global Director, Industrials for Solex Thermal Science. He shared insights into the sodium citrate manufacturing process, as well as the role vertical heat exchangers play at the cooling stage.

1. What needs to be considered when cooling sodium citrate?

Sodium citrate is a sodium salt with citric acid. There are different variants of the salt such as:

Monosodium citrate (C6H5O7Na) usually produced from a solution of sodium bicarbonate
Disodium citrate (C6H5O7Na2)
Trisodium citrate, which can by anhydrous (C6H5O7Na3) or hydrated (C6H5O7Na3*nH2O); the hydrate can be a mono or dihydrate

These salts are hygroscopic and attract water to their surface. This makes the surface of the particles “sticky,” thereby compromising the flowability of the salt. This can easily lead to blockages in any sort of process and conveying equipment.

When it comes to cooling applications, the issue is even more tricky. The product is usually coming from an upstream drying process – along with hot, moist air, which is traveling with the product in the void. While cooling the product, the air in the void also gets cooled down. Because cold air cannot carry as much moisture as cold air, the moisture may condensate. This effect needs to be avoided in any cooler to ensure proper continuous operation of the equipment.

Solex can calculate temperature and moisture level at any point within our vertical heat exchangers. We can then implement countermeasures such as air injection to reach high availability of the plant and to minimize downtime. We have more than 20 years of experience in this industry, with multiple installations located in countries around the world.

2. Where does the cooling of sodium citrate typically take place?

Typically, after the drying stage. Depending on the plant layout, screening of the product could be before or after the cooler.

3. Is the product being cooled in powder or granular form? And are there any handling considerations?

The salt is actually more of a crystal or granule than a powder. Our vertical heat exchangers are designed specifically for free-flowing particles and granules such as this. The particle size distribution of the product is essential for considerations such as plate spacing and the choice of discharge feeder which have the largest impacts in guaranteeing uniform mass flow.

4. How do our heat exchangers facilitate increases in production capacity?

The standard technology for processing sodium citrate used to be fluidized bed dryers and coolers. Such systems are usually comprised of one unit that includes a drying and a cooling stage. In case of production increases, the cooling part of the fluidized bed system can be revamped to an additional drying stage. Yet a new cooler is needed downstream of the dryer.

Solex’s vertical heat exchangers need very little floor space. This means plant operators can seamlessly integrate them into their operations with significantly less revamp costs than another fluid bed cooler.

5. Does the “green” nature of our equipment benefit producers?

Yes, of course. Solex vertical heat exchangers have almost no moving parts, and consume less energy than conventional fluid bed systems. Also, because we do not need air to fluidize the product, the amount of gaseous emissions is low in comparison.

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Ready to talk specifics? Contact a Solex team member today.

Solex is the global market leader and developer of high-efficiency, indirect heat exchange technology for the heating, cooling and drying/conditioning of free-flowing granular materials such as solid granules, pellets, beans, seeds and particles.

Over the past 30 years, our Canadian-headquartered company has installed more than 800 heat exchangers in more than 50 countries worldwide with applications ranging from industrial materials and fertilizer to oilseeds and sugar.

Gerald

Gerald Marinitsch, Global Director, Industrials, Solex Thermal Science

Gerald joined Solex in 2014 and now leads the company’s efforts within industrial applications such as chemicals, metals and minerals and sands. Contact Gerald.