Spiral heat exchangers are designed to handle the toughest heat transfer challenges

Alfa Laval’s spiral heat exchangers save refineries 54 TWh of energy annually and reduce CO2 emissions by over 13 million tonnes, Sunand Mohan, Director, Energy Division Middle East and Southern & Eastern Africa, Alfa Laval, tells OGN

Decarbonising heat, electricity, chemicals and fuels is crucial if the world wants to meet its commitments to the Paris Agreement while at the same time not sacrifice on the standards of living and foster economic and social growth. Energy efficiency is at the centre of this challenge.

Increased energy efficiency is considered as the biggest single contributor to meet the Paris Agreement with 45 per cent of CO2 emissions reduction coming it.

Sunand ... driving energy efficiency

With heat exchangers, there are three main methodologies to drive energy efficiency: Improving an existing installation; securing a good operation of the existing heat exchangers; and hunting for waste heat energy streams that can be reused for other purposes.

Spiral heat exchangers are designed to handle the toughest heat transfer challenges.

Whether it’s frequent fouling from dirty media or limitations from pressure drop and floor space, they are the ultimate problem solver for liquid-to-liquid and two-phase duties.

The robust, efficient and compact designs keep both installation and maintenance costs extremely low, and they have a proven reputation for almost never fouling up.

Alfa Laval’s spiral heat exchangers improve sustainability by minimising fouling or clogging even in duties involving very dirty, highly viscous, or particulate media.

The spiral core of the heat exchanger

The easy-to-open design makes cleaning quick and simple, ensuring low maintenance costs, while reduced pipework and steel structures means lower installation costs.

Each unit is fully customised, offering the best thermal fit for the specific duty with increased energy savings and reduced emissions. This is the result of thermal efficiencies two to three times higher than comparable shell and tube exchangers.

The manufacturing of Alfa Laval spiral heat exchangers incorporates an automated process for bending the edge of the channels. This is followed by a cold metal transfer automatic welding machine for the final closure weld.

The combined effect of this so-called RollWeldTM technique is consistent quality of the channel closure, which in turn is critical for the strength and corrosion resistance of the channel welds and thus the reliability of the overall unit.

The design of the easy accessible spiral heat exchanger allows to perform most services onsite without having to move the unit.

Experts can assist with everything from routine cleaning and inspections to more demanding issues.

Service centres are staffed by qualified welders, who can perform critical repairs on location.

Robust, efficient and compact designs have a proven reputation for high reliability in some of the toughest process duties across industries.

With added support from a worldwide network of local service experts, spiral heat exchangers deliver a truly sustainable uptime.

The design of the spiral heat exchanger allows to perform most
services onsite without having to move the unit

As a result of investing heavily in innovation, there are new products and solutions in development to support customers’ sustainability goals while keeping their process efficient.

One such example is when Alfa Laval was approached by a major petroleum refining company in the Middle East.

The end-user had third-party spiral heat exchangers installed in its refinery section wherein the spiral heat exchangers were responsible for cooling hydrocarbon slurry, but were faced with the situation where the slurry was getting overcooled.

A lowered temperature in the process stream would lead to high viscosity and thus a higher pressure drop, leading to cavitation in the downstream pump.

To compensate when cooling water flow is reduced, cooling water temperature increases coupled with low mass flows were leading to water side permanent fouling and corrosion problems.

Over a period of time, these problems were leading to a permanent loss of performance.

Also, while looking for a solution, the customer wanted to match end-to-end dimensions along with the nozzle sizes/projections in conformance to existing units. Therefore, the replacement items needed the existing facilities without any modification.

The piping and instrumentation diagram of the unit, the cooling water system, and the up- and downstream exchangers on the oil side were investigated.

Using QR codes end-users get direct digital support, including
troubleshooting assistance

Laboratory viscosity data along with other crucial process parameters were used — and not the parameters on the customer data sheet — to do a root cause analysis.

The provided laboratory viscosity data showed a lower viscosity than originally used. This meant that the over-surfacing had been higher than what was indicated on the first set of datasheets.

Maintaining an optimum velocity (neither too high nor too low) was another challenge as velocity was a crucial parameter to maintain the catalyst particles in suspension.

After careful evaluation of the data provided, the spike in viscosity of the hot side fluid due to overcooling was tackled in the new design.

Maintaining the plate width to the highest possible degree minimised the piping modifications required to install the new unit.

One major suggested change was to operate the exchanger co-currently.

Lower velocity due to higher viscosity can also lead to corrosion in plates and that was addressed in the new design by providing an alternative plate material.

The customer was already using spiral heat exchangers. However, it was important to not only use the right technology, but to design it considering the real-time operating problems that the heat exchangers can face.

Immediately after arrival, the new spiral heat exchangers, which were customised according to the customer needs, were installed and commissioned by the refinery technicians under the supervision of Alfa Laval specialists.

The units were started on schedule with performance in line with the guarantees.

Together with the customer, we are exploring connected exchanger technology.

The connected exchanger allows for continuous monitoring of the unit performance and for conditional maintenance that can be predicted in advance, allowing for more reliability and uptime.

In this initiative, QR codes are attached to every unit and scanning these codes guides the end-users to direct digital support, including troubleshooting assistance.

By using this, the users can directly log in their problems by uploading pictures and videos.

Alfa Laval’s installed plate heat exchangers save refineries 54 TWh of energy annually, compared to what they would consume with less efficient, conventional heat exchangers. And the corresponding reduction in CO2 emissions is over 13 million tonnes.

Imagine if every refinery switched to more efficient, compact welded plate heat exchangers for all of their processes, we could reduce energy consumption by 23 per cent and global carbon emissions by 245 million tonnes.

That’s the equivalent of what the entire country of Spain emits in a whole year.