Hydrogen and fuel cells foster a great opportunity for the deployment of sustainable and clean mobility of future, alternative to electric vehicles. For a project related to a hydrogen truck, we are supplying in several steps a series of brazed plate exchangers, completely manufactured in stainless steel.
The heat exchangers are employed on the hydrogen vehicle to transfer the heat from the cooling circuit of the fuel cell to the main cooling circuit of the vehicle, in order to maintain the two cooling circuits separated.
These are in fact heat exchangers of the same version as common brazed plate heat exchangers, but instead of copper they are completely made in using stainless steel.
The project started one year ago and required a series of sizings and technical refinings, in order to define the model of heat exchangers to be supplied. As usual in these kind of brazed plate heat exchangers, and even more in this particular case, the exchangers have been pressure tested and also passed destructive testing, in order to ensure maximum reliability of the thermal transfer equipments.
Previous videos focused on anodic oxidation applications triggered some questions, mostly referred to the selection of corrosion resistant materials in heat exchangers. In fact, heat exchangers employed in anodic oxidation have to work with solutions of sulphuric acid with 20% concentration, at temperatures of approx 20-25° C. Based on ISO-corrosion diagrams, these conditions would suggest the use of AISI 316. But the risk in these kind of plants is that the temperature goes even higher, for example during the shut down of the plants during the summer season.
Another kind of material must then be selected, being the Avesta 254 SMO, a high-performing alloy which offers excellent corrosion resistance even at high concentrations of suplhuric acid and temperature levels. In case it’s not enough, it is also possible to use Titanium, commonly employed with seawater applications thanks to its excellent resistance to high concentrations of chlorides and high temperatures.
Talking about costs, if AISI 316 represents 100, for both Avesta 254 SMO and Titanium the cost is about 200, depending on variations on the market.
When sulphuric acid concentration gets higher the problem gets more complicated, and Avesta and titanium are no more suitable. It is therefore necessary to use Hastelloy C276, another high-performing alloy with a quite high cost and with relatively low availability on the market. Anyway, this is a kind of material that can be cold-printed, and so a perfect solution for plates in heat exchangers.
The options are quite similar in case of shell and tube exchangers, being it possible to find on the market tubes in Avesta 254 SMO, and also titanium pipes even if it can be a little more difficult, as well as for Hastelloy C276. But there are also other materials that can be employed here, such as Incoloy and Monel. These are anyway more sophisticated materials, involving higher costs both for the raw material and the working process.
When the corrosion level goes even higher, it’s also possible to use graphite exchangers. These are exchangers with a peculiar construction, in some way similar to plate and shell and tube exchangers, made using mixtures of graphite.
Moreover there are plastic exchangers, in particular U tube bundle exchangers consisting in an ensemble of tiny plastic tubes to be immersed inside the tank to be thermoregulated. Usually these are made using polypropylene or PVC or other plastic materials, depending on the kind of application, workability and the temperature levels. Involving heating tasks, in fact, using plastic always requires great attention.
Finally, leaving the anodic oxidation field and entering the pharma sector, talking about resistance of materials using corrosive fluids there are also exchangers and reactors made with glass. Anyway, this is a completely different industrial production environment, with very different levels of accuracy and much more delicate than more ‘heavy’ anodic oxidation plants.
The ‘magic word’ is non-clogging filling packs on cooling towers. A long-term customer of Tempco, with several textile facilities around Europe and an important installed park of evaporative towers, launched a few years ago an intervention to increase performances and efficiency on operational costs of these machinery.
Some year ago we did a complete analysis of critical issues involving plants using evaporative towers, installed in a couple of industrial production facilities. In collaboration with an engineering and design studio, we made it clear that the rapid and excessive clogging of the filling packs within the towers generated a decrease of their cooling capacity, combined with a gradual increase of power consumption.
The technical office then agreed on testing a tower equipped with a non-clogging filling pack, different from a splash type one, obtaining quite good results that convinced them to adopt this solution as a standard for all of the plants, first equipment cooling towers but also for the revamping of existing ones.
Now following an annual maintenance and integration program, the customer is gradually substituting all of the filling pack systems of its towers, even if it requires bigger machines, and therefore a higher first investment cost, but with a two-seasons long ROI, achieving a strong decrease on maintenance and energy consumption costs.
Mono fluid thermoregulation units are therefore systems that, if properly programmed, allow to follow the thermal scheme of a reactor or a chemical equipment. The units allow to monitor, control and regulate temperatures of the product inside the reactor. Mono fluid thermoregulation employs a circulating pump, ensuring the flow of the fluid between the jacket of the reactor, or the half pipe of the equipment, and an array of heat exchangers, or electrical heaters. The whole system is managed by an electronic regulator that controls the temperature of the fluid.
On the secondary circuit it is possible to have vapour, employed to heat the fluid, and refrigerated water or cooling tower water for the cooling of it. If vapour is not available, a heating section can be employed using electrical resistors, managed as well by the electronic regulator.
The system can be managed by remote using a PLC, an electronic regulator or other interfaces. It is then possible to control a quite varied range of temperatures, starting from under zero temperatures down to -30°, going up to very high temperatures, reaching also 250° C. Depending on the range of temperature required, the fluid employed will be simple water, or glicol water with anti-freeze to reach low temperatures. Pressurized water, over-heated, is employed to reach temperatures up to 140° C, and finally diathermic oils or silicone oils are employed for high temperatures.
Diathermic oil is usually employed for plants involving only high temperatures, while silicone oil, or synthetic oil, is used in plants requiring a wide range of temperature regulation, from under zero up to very high temperatures. These oils have indeed the characteristic of having a good flowing property at low temperatures, and also offer good thermodynamic and physic properties at very high temperatures.
These units can be provided compliant to several regulations, depending on the kind of application or the Country of installation. Taking about chemical and pharmaceutical industry, it will very common to be in presence of an explosion risk environment, thus requiring an Atex execution. If the units are for installation within the United States these will be compliant with UL regulations, while if the destination is Russia they will be provided with EAC certification.
Very often mono fluid thermoregulating units have to be combined with dedicated refrigerating groups, not directly integrated within the unit in order to ensure production continuity in case for example of a fault in the cooling section. This kind of thermoregulation systems must indeed be conceived to ensure maximum flexibility, maximum reliability and extreme precision in temperature control.
We collaborate since approximately 10 years with a customer that operates in the lead-acid batteries recycling, providing special cooling systems employed on the burners within the plants, aimed to the recovery of materials.
These systems present a quite typical composition, which includes:
self-draining dry cooler functioning with only water
pumping group with 2 redundant pumps
monitoring and managing panel
A peculiar characteristic of the solution is the redundancy of equipments, due to the fact that for this kind of application, requiring extreme operating conditions and working constantly 24/7 during 365 days per year, it’s absolutely necessary to always ensure the availability of the cooling process.
The presence of lead-acids also eventually creates a very harsh and aggressive working environment, and therefore another characteristic is the employ of stainless steel materials for the construction of the instruments.
An actual trend in energy saving is the implementation of free cooling systems combined with chillers to achieve cooling in industrial processes.
When a production process requires for example cold water at the temperature of 15° C, its is necessary to install a chiller that allows to obtain water at these temperatures for the whole time period of the year. But during the Winter season it’s possible to employ direct thermal transfer systems leveraging the low temperatures of external ambient air. These are dry cooling or free cooling systems consisting in thermal transfer arrays or huge radiators with ventilation that allow to cool water.
The convenience of installing these kind of systems depends on two main factors, first of all the latitude of the installation site of the plant. Secondary, the temperature levels required by the kind of industrial process involved.
Having for example a production process that needs cooling water at the temperature of 15° C, it will be necessary to have a chiller during the Summer season. But during Winter, or whenever the ambient air temperature falls down 10° C, it is possible to obtain water at the temperature of 15° C using a classic dry cooler. Achieving a significant energy saving: it is indeed possible to completely shut down the compressors of the chiller, while keeping only the energy consumption related to the pumps that provide the circulation of refrigerated water and the fans for ventilation. For a 100 kW plant, for examples, it leads to a saving of 30 kW of energy consumption related to the compressors per hour. The energy saving that can be achieved is then directly related to the thermal duty required.
It is therefore necessary to properly evaluate both the temperatures required by the industrial process and the average local seasonal temperatures, in order to estimate the return of investment in every specific case of the implementation of a free cooling system.
Here’s a new Tempco Infographic dedicated to the growing adoption of IoT and Artificial Intelligence solutions within companies in the manufacturing sector, pushing innovation of the process industry toward data-driven models. Connected machines and components ‘talk’ to operators and plant managers, allowing the real time monitoring of the state of production and at the same time of the conditions of manufacturing assets.
Real-time condition monitoring of processes and production systems allows not only to maximize productivity reducing waste and errors, increasing quality using optimization models developed with AI algorithms for specific industrial applications. The data science also allows to extend the life cycle of machinery and equipments, enabling new predictive maintenance functions to increase plants’ availability and reliability, avoiding expensive production downtimes.
IoT and AI combined provide at last a transparent insight on effective energy consumes of production processes, aiming to a constant real-time improvement of energy efficiency and costs reduction within the process industry. This is also the goal of the iTempco platform, which employs IoT, analytics and cloud to maximize thermal energy efficiency and energy saving in temperature control and thermal energy management applications for production processes of all kind of industrial sectors.
The thermoregulating units are completely framed and have been developed to implement monofluid thermoregulation of the temperature of the reactors.
Monofluid thermoregulation is indeed a solution very widely employed within the chemical and pharma industry. Here, a unique working thermal fluid flows within an array of heat exchangers, providing the diverse temperature regulation levels for each of the production steps. The solution avoids the downtimes related to empty and load operations of different thermal fluids inside the circuit, achieving in addition very fine levels of temperature control.
The two thermoregulating units have been equipped with state of the art technological solutions, in order to obtain very high levels of precision in the control of process temperatures with tolerances of +/-1° C.
A question we are very often asked in Tempco is if during maintenance and regeneration operations on plate heat exchangers the gaskets have to be all replaced every time. The answer is… yes and no. Which means that sometimes the substitution is necessary, sometimes not, and it depends on the kind of application involved.
First of all let’s divide two cases, the first one being heat exchangers for heating that work using vapour. In this case, it is very likely that the exchanger will have gaskets in Ethylene-Propylene Diene Monomer (EPDM). This kind of gasket will result very stressed by the vapour at high temperatures. When opening the exchanger, it will be clear to see that gaskets are stressed, because EPDM has a lower elastic return coefficient than Nitrile or Vition. So that after 2 or 3 years of operations it looses the elastic return of a brand new gasket. If we don’t replace them after having washed the plates and re-assembled them, we will probably encounter leaks on the exchanger. It is then suitable to replace all of the gaskets while at it.
Otherwise, if we have a plate heat exchanger working with cold water, for example coming from a cooling tower at 30° C or from a refrigerating group, after 3 or 4 years of operations the plates will be dirt and to be washed, but gaskets will probably look as new. It is then very likely that it will be possible to keep and re-use them, especially in case of clip-on gaskets that don’t require the use of glue.
Of course, some good common sense must be used here also. If the regeneration intervention involves a huge plate heat exchanger, with for example a frame of 200 plates with a 0,4 sm surface each and nozzles with 100-150 diameters… the operation will clearly have a high cost, maybe after 4 years of operations. The cost of a replacement of the gaskets will thus have a partial impact on it too, but very much worth it if the exchanger, once washed and re-assembled with the old gaskets still on it and not replaced, will start leaking.
The tip is then to ask experts to have a look on it, which means that in Tempco when we open a plate heat exchanger, we prepare a proposal for the customer that includes the cost of new gaskets, even splitted. And then contacting the customer telling him if it’s better to effectively replace them or, otherwise, if the old gaskets can undergo a further working cycle.
Last month we’ve tested a special refrigerating group developed for production lines of tubes to be employed in dialysis plants manufactured by a pharma company.
The tubes for dialysis systems require a very delicate and sophisticated production process, due to the fact that they are employed for blood transport. The tubes are in particular employed with a peristaltic pump, being squeezed in order to pump the blood.
Mechanical and elastic characteristics of the tubes are therefore fundamental, ensuring they are smooth and flexible but at the same time very much resistant.
The system we’ve supplied is a first equipment prototipe that produces a refrigerated air flow at a controlled temperature down to -15° C, with precisions of +/- 0,5° C. The refrigerated air is employed in a patented process which allows to obtain a suitable modification of the dialysis tube.
Previously, the manufacturer employed a venturi effect cooling system, but it failed in obtaining the necessary effect. The results of the test phase of the new refrigerating group totally satisfied the customer, eventually leading to the decision to implement these equipments in all its production lines installed in its facilities globally.