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7 April 2022
Chillers for the simultaneous production of hot and cold water for the pharmaceutical industry – an article for the Świat Przemysłu magazine

In the pharmaceutical industry, a very wide temperature range is used in production processes. We are talking about temperatures from the cryogenic level, i.e. – 196 ° C for liquid nitrogen, up to high temperatures for pasteurization or sterilization. Moreover, these temperatures are often used simultaneously in the production of the same products, but at different stages. This fact gives a unique potential which is discussed in this article. I am talking precisely about reducing energy consumption while ensuring the required temperatures at a high level of safety. As the reader has probably already noticed in his production facility, the above-described temperature range is produced by various methods. Like the manufacture of drugs, the cooling and heating associated with it can be complicated, so I’ll try to organize some basic knowledge first.

The table below shows the cooling and heating methods depending on the temperatures:

 

It can already be seen that, in terms of cooling and heating, there are temperature ranges in which devices operating in the same technology can be used – we are talking about compressor devices. I purposely avoid the term chiller or heat pump, because depending on the medium used, the same device will be described differently. For clarification, I present a basic diagram of the operation of a refrigeration device.

 

From the point of view of the use of cold, the above diagram shows a chiller or from the heat side – a heat pump. In essence, the cooling device receives energy from the heat source at a sufficiently low temperature, then raises the temperature parameter and transfers it to the upper source – air, water, etc. So the potential for producing cold and heat at the same time is obvious. Closed circuit compressor refrigeration equipment.

They can be divided according to many methods:
• Working temperatures (freezing / cooling / air conditioning),
• Mode of operation (space / process cooling),
• The medium used (F-gas / CO2),
• Operation modes (cooling / heat pump / multi-tasking) etc.

The primary method of dividing refrigeration technologies is the refrigerant used. So far, the most common devices work on popular F-gases such as r404a, r410, r134a etc. These factors contribute significantly to the increase in the greenhouse effect and are now regulated and phased out. Regulations such as Regulation of the European Parliament 517/2014 prohibit the use of factors with GWP above 2500. Other regulations impose quotas on the import of factors, impose CRO obligations, personnel certification etc.

However, I would like to emphasize that I am not in favor of phasing out technology by regulation. It is also a fact that F-gas refrigeration uses a lot of energy unnecessarily. Consequently, other – new technologies are much more profitable in financial terms.

This is where the r744 – CO2 devices come in. Cooling systems using this refrigerant are already very popular, liked and proven in industries such as trade, food industry and logistics warehouses. It is safe to say that they are the first choice.

Below is a list of features that customers can expect from the most modern, most energy-efficient chillers:

• Refrigerant r744 (CO2)
• Operation in transcritical mode
• Evaporator flooded
• Very high pressure standard of 80 / 120bar
• Gas coolers selected to be DT 3K or less
• High-temperature heat recovery
• Dedicated control system with remote supervision

As previously mentioned, CO2 devices have a very significant potential for heat production or recovery. How is it different from heat recovery from F-gases?

Due to the transcritical operation, on the heat transfer side, chillers on r744 can heat water up to + 95 ° C, compared to about 55 ° C for F-gas devices. Another method by which cooling devices can be divided are operating modes.

So we can distinguish:
1. Chillers with or without heat recovery
2. Heat pumps with or without cooling recovery
3. Devices simultaneously cooling and heating
4. Equipment that can cool, heat, or exercise
both of these activities at the same time

The chiller will cool the medium and discharge the heat to the environment. It is possible to use heat recovery. However, heat will be as much as it results from the production of cold. It will not be possible to force work in the “heat recovery” mode.

The heat pump produces hot medium. It extracts this heat from the environment in an air or ground heat exchanger. Some heat pumps have the option of “cooling recovery” which will work in a similar way to heat recovery. That is, it will not be possible to force the production of cold when no heat is required.

Cooling and heating devices are a typical example of a process system. There is no heat exchange with the environment anywhere. The amount of heat and cold are closely related and the energy balance between them must always be correct.

The last group of the most specialized systems are devices that can freely produce cold and heat, regardless of the energy balance between them. These devices have a heat exchanger that will give off excess heat or take it from the environment.

There is obvious potential for dual-function devices in all processes that require both cooling and heat at the same time, such as drying, pasteurization, etc. The heat available in heat recovery or in a heat pump is defined by two parameters:

• heating power in kilowatts [kW] – the amount of available heat
• temperature [0 ° C] regardless of the power

As I mentioned before, CO2 devices have a significant advantage over F-gas devices in terms of heating potential because it is possible to reach temperatures of up to 95 ° C with very low energy consumption. However, I must point out that these are not universal devices, as there are limitations in the scope of use for every installation. These limitations are more economic than technical. This means that there are hot water parameters that can be achieved, but it will be unprofitable in terms of energy consumption. We will start the economic analysis with a comparison of two chillers operating under the same conditions described below:

• Water 7/12 ° C
• The heat is transferred to the environment for the climate of Poznań
• 500 kW cooling capacity
• 100% permanent charge, 365 days a year
• No freecooling

Reference system (blue chart):

• R407c, working in very good parameters (better than the most common ones)
• Condensing temperature minimum 28 ° C, DT 10K

System compared (orange chart):

• R744, operating at the most common parameters
• Condensing temperature minimum 16 ° C, DT 3K (sometimes better parameters are met)

The chart below shows the energy consumption of the considered chillers per year.

 

As we can see, the difference in energy consumption between the considered devices is significant and amounts to 44%. The diagram of the F-Gas system is close to flat as F-Gas units are limited in their ability to operate at a minimum condensing temperature. In our case, I took the value of 28 ° C. So the F-gas chiller in winter at an outside temperature of 0 ° C will work the same as at + 18 ° C. This is a very good parameter that few devices actually achieve. Meanwhile, the CO2 chiller will be able to drop down to + 16 ° C condensing temperature.

Chiller on r407 for a year will use 880 thousand. kWh, and on CO2 491 thousand. kWh. This means that regardless of the current or future electricity rate, the cost of operating a CO2 device will always be lower.

How will this comparison look for a dual-purpose device, i.e. cooling and heating at the same time? We require water at a temperature of 18/60 ° C from both systems.

This means that during the year:

• Both units will produce: 4,380,000 kWh of chill at 7/12 ° C
• The F-gas device will produce: 5 841 234 kWh of heat and use 1 461 thousand. kWh of electricity
• A CO2 device will produce: 5 311 113 kWh of heat and use 931 thousand. kWh of electricity

For the price of 1kWh = 0.8 PLN, the cost of operation is as follows:

• PLN 1.522 million for r407c
• PLN 0.670 million for r744

The chart below shows the energy consumption of the compared devices per year. Energy savings for CO2 are over 36%.


As part of my practice as a consultant and designer of refrigeration systems and heat pumps, I have made hundreds or even thousands of similar comparisons. Taking into account the investment costs, the payback time for CO2 equipment ranges from 1.5 to approximately 6 years. To determine what the payback will be for the system that can be used in the reader’s facility, individual calculations must be made.

So far I wrote about the advantage of refrigeration on r744. However, the reader should also know about his limitations, which are on the warm side. Due to the operation in the supercritical circuit, a reasonable maximum temperature of the heated medium inlet should not exceed approx. 30 ° C.

To sum up, the pharmaceutical industry, due to its unique production technology, has a very large potential for energy savings through its wise use. I understand it wise to use energy that has already been used up many times without releasing it into the environment in the form of heat. The solutions I propose provide savings thanks to the reduction of energy consumption, regardless of its source. This is especially important for plants that have already reached their electrical or gas connection size limits. There are at least two commercially available and proven heat transformation technologies. They are different and suit different applications. Although I see a significant potential for the use of CO2 devices, the limits of their applications described above should be kept in mind. However, if your plant can use r744 refrigeration, it will definitely be a very profitable investment.

 

The entire content of the magazine can be found in the link below

https://publuu.com/view/422/8191/page/18

for the World of Pharmaceutical Industry Journal 1/2022 Maurycy Szwajkajzer