Chemical and pharmaceutical industries

In the chemical and pharmaceutical industries there are a wide range of processes which require refrigeration. In most cases ammonia is used, or sometimes halogen-free or halogenated hydrocarbons. CO₂ is of no importance to date.

It is only in exceptional cases that the use of halogen-free refrigerants is not economic. In such cases CFCs such as R 13 or R 503, or brominated refrigerants such as R 13B1, were used until they were banned. As a rule these are very specialised applications with special conditions. One example is chlorine liquefaction plants. Today HFCs or PFCs are mostly used as CFC substitutes in these systems – which were previously filled with CFCs.

When considering whether halogen-free refrigerants are available, it is first of all necessary to distinguish whether existing systems are to be converted or completely replaced. For example, in the case of total replacement (new system) it is often possible to do without PFCs and HFCs. Since these are on the whole specialised applications, this field will not be discussed in depth here.

No information is available about refrigerant emissions in this specific sector of industry. The special problems associated with PFCs are discussed again in Chapter 3.3.8.

Turbo refrigeration systems

The industry sometimes uses process systems with cold-water or brine circulation. In view of the generally high refrigeration capacities, turbo (centrifugal) compressors are employed. In industrial applications, turbo compressors are also used in direct systems. In addition to the

technical information provided in Chapter 3.1.1, the following general points can be made about these turbo compressors:

Turbo refrigeration systems deliver large flow volumes and are thus suitable for refrigerants with low volumetric refrigeration capacities. They need a refrigerant with a high molecular weight, and until the ban on CFCs they were therefore run mainly on these refrigerants, as a rule R 11. Since the ban on CFCs, the refrigerant used in new systems has mostly been HFC-134a [FKW 1998a; Grage, Pareidt 2000]. Occasionally HFC-245fa is used, or HCFC-123 is still in use outside the EU [UNEP 2009].

In new systems, water (R 718) can be used as a refrigerant. First pilot systems have been created with water as refrigerant. Under a joint research project supported by the Federal Ministry of Education and Research, work is currently in progress on the development of a third generation of this R 718 turbo chillers [ILK 2010]. One implemented example of a turbo system with water as refrigerant is the turbo process system at DaimlerChrysler in Düsseldorf.

Since turbo compressors are mainly found in high-capacity chillers (water chillers) used for air-conditioning, the possibility of using water as refrigerant is described in more detail in Chapter 3.3.5.2 (air-conditioning of buildings).

As far as is known, halogen-free hydrocarbons are used only in systems in the petrochemical industry, where hazardous and, in particular, explosive substances are handled on a routine basis [UNEP 2006; UNEP 2009].

In view of its low molecular weight, ammonia is not suitable for turbo refrigeration systems.

In the construction of new systems, however, multi-stage ammonia systems, which are highly energy-efficient, are theoretically a technically feasible alternative to HFC turbo systems.

Such systems are not implemented, however, because of the very high costs involved in multi-stage ammonia systems [Axima 2003b].

Conclusions

The use of halogen-free refrigerants is state of the art in the chemical and pharmaceutical industry, apart from certain specialised applications.

If there are technical reasons – e.g. in existing systems – why it is not possible to do without fluorinated refrigerants, the use of PFCs should be avoided because of their very high global warming potential. Moreover, in view of the large refrigerant charges that are usual in these systems, particularly effective measures must be taken to minimise emissions of the fluorinated refrigerants.

As yet it is not possible to do without HFCs in turbo chillers. Water as refrigerant is very promising and trendsetting, but for cost reasons it cannot be used everywhere at the present time. When drawing up plans, however, one should always consider whether the use of turbo systems is absolutely essential, or whether it might make economic and ecological (energy-efficient) sense to use other technologies without HFCs.

3.3.3.3. Coldstores

Most foods, and also pharmaceutical products or blood plasma, for example, need to be kept cool during processing, transport and storage. Within this chain, coldstores (refrigerated and freezer warehouses) are used to store frozen products (product temperature ≤ -18°C) or chilled products (product temperature > 0°C), nearly 90% of which are foods. Initial storage of raw materials and/or finished products takes place at the manufacturer/processor. From there the finished products are sent – sometimes via intermediate stores (carriers’ warehouses) to central warehouses, where they remain until shipped to the point of sale, e.g. supermarkets.

Supermarkets themselves have their own storage facilities. As well as large central (regional) warehouses, the trade in Germany operates smaller trade warehouses which are usually closer to the point of sale [Meurer, Schwarz 2002].

The average size of coldstores ranges from 45,000 to 75,000 m³ [VDKL 2009a]. According to a survey by the German Association of Coldstores and Refrigeration Logistics Companies [VDKL 2009], there were more than 750 coldstores in Germany in 2009 with a total storage space of 21.6 million m³ or 4.5 million Euro-pallets. The survey covered not only commercial coldstores run by VDKL member companies, but also in-plant coldstores. The total capacity of the 239 commercial VDKL coldstores (approx. 80% of all coldstore operators are VDKL members) amounted to about 12.6 million m³ [VDKL 2009].

Until the 1990s, a small number of high-capacity systems (> 1 MW for deep-freeze applications) using the refrigerant R 22 (HCFC) were built for coldstores. In Germany, however, R 22 has been banned in new systems since 1 January 2000. HFCs have not acquired any importance as substitute refrigerants in this capacity range. For cost reasons alone they are not normally used [DKV 2003].

Today HFC systems are effectively found only in smaller trade/transhipment warehouses not exceeding 50,000 m³ in size [VDKL 2010]. These systems have a refrigeration capacity of less than 500 kW. In this capacity range the capital costs of HFC systems are often lower, because there are many series-production components available. This also improves the spare parts availability situation [VDKL 2003]. Other considerations include a simpler and speedier construction permit procedure and a broader and usually cheaper range of services [VDKL 2010]. One disadvantage is that there is rarely any energy optimisation and adaptation to specific conditions [DKV 2003]. No comparative information is available on overall costs (capital and operating costs).

A statistical survey by the VDKL [VDKL 2009a] of 246 coldstores with 554 refrigeration systems revealed that over 80% of the refrigeration volume is cooled using ammonia, about 16% with HFCs (mainly R 404A, R 134a), nearly 2% with R 22, and less than 1% with CO₂. In 2001 these applications emitted about 7 t of HFCs [Schwarz 2003b]. With a share of about 4% of industrial refrigeration, coldstores are not of any great importance with regard to HFC emissions. This is due in particular to the already large proportion of halogen-free refrigerants in this sector.

Reduction options

In large coldstores, which are mostly operated using refrigeration systems with a capacity of over 1 MW, ammonia is already the standard refrigerant used. Since these are premises without any public traffic, the great majority are ammonia systems with direct evaporation. In isolated cases, ammonia/CO₂ cascades have been in use for some years now as an alternative with favourable energy properties [UNEP 2003; Meurer, Schwarz 2002]. The quantity of ammonia installed in these systems is considerably smaller, with the result that the immission control authorisation procedure required for ammonia quantities of 3 t or more is not necessary [UNEP 2003; Axima 2003a]. Nevertheless, these systems have not succeeded in becoming established, partly because of the higher capital costs compared with ammonia systems [VDKL 2010]. The VDMA specification (draft) 24247-3 [VDMA 2009] basically recommends ammonia or an ammonia-CO₂ cascade for new coldstores. Coldstores with straight CO₂ systems are the exception in Germany and very rarely found [VDKL 2010].

UNEP [UNEP 2009] reports that in 2008 a chilling and freezer warehouse with a transcritical CO₂ refrigeration system was built in Denmark. As well as the necessary refrigeration capacity (1,500 kW), this system also supplies heat (1,200 kW) which is fed into a local heating system. In this form CO₂ is judged to be very cost-effective.

From a technical point of view there are no major problems involved in building ammonia systems or ammonia/CO₂ cascades for capacities of 500 kW or less. In view of the necessary safety precautions and the permits required, there is a need for long-term planning here. This planning input, the higher capital cost (up to 30% more) and a rather thin service network have so far prevented the use of this environmentally sound technology [VDKL 2010; DKV 2003; Peilnsteiner, Truszkiewitz 2002].

In the case of larger ammonia systems, the higher capital costs are offset by lower operating costs: compared with a normal HFC system, ammonia systems have any energy advantage of

some 15-20% [VDKL 2003; DKV 2003]. Since the refrigeration system is responsible for more than 70% of the energy consumption of a coldstore [VDKL 2009a], this permits a substantial reduction in energy costs. Refrigerant costs are also lower for ammonia systems [VDKL 2003; DKV 2003]. In practice, however, energy efficiency - or even operating costs in general - are quite often rated less important than capital cost [Peilnsteiner, Truszkiewitz 2002].

For fairly small systems (ammonia or ammonia/CO₂) the operating cost savings in the first few years are usually smaller than the extra capital cost compared with an HFC system. In the final analysis the depreciation period is the crucial factor for this cost comparison.

The high energy efficiency of ammonia systems is due to the favourable thermodynamic properties of ammonia. The TEWI figures for ammonia systems are therefore favourable.

Because of the greater heat of evaporation, it is also possible to select smaller-bore pipes than for HFCs [Peilnsteiner, Truszkiewitz 2002], which in turn has a positive effect on capital cost.

Unlike HFC systems, an ammonia system is built for the individual site. Components are produced in relatively small numbers. Material-related and production-related aspects also result in higher costs. For example, the fact that ammonia is not compatible with copper means that ammonia systems cannot use the copper pipes that are otherwise normal in refrigeration systems. For the reasons mentioned, such systems are on the whole more expensive to buy [DKV 2003], but of high quality.

In other countries, e.g. the Netherlands, one also finds smaller coldstores (with refrigeration capacities of around 350 kW or even lower) using highly energy-efficient ammonia/CO₂ cascades [Axima 2003a]. However, their construction has usually been facilitated by state assistance programmes [VDKL 2010]. From a technical point of view it would also be possible to build systems with a capacity of around 100 kW and a good coefficient of performance (COP). To date, such systems have not been implemented for cost reasons (capital cost) [Axima 2003a]. Selection of the necessary refrigeration components also becomes more difficult as the refrigeration capacity of the system decreases [VDKL 2010].

No information is available about specific abatement costs in relation to CO₂ equivalent. This is due to the fact that cost studies usually look at the entire field of industrial refrigeration and are not broken down by individual sectors.

Conclusions

Ammonia is the standard refrigerant in coldstores with refrigeration systems with a capacity exceeding 1 MW. In this capacity range the use of HFCs does not make technical or economic sense.

Refrigeration systems with ammonia or ammonia/CO₂ are state of the art in smaller coldstores as well (< 50,000 m³, system capacity < 500 kW). It is already technically possible to build ammonia systems with capacities of as little as 100 kW. Nevertheless, smaller coldstores in Germany have not so far used ammonia or ammonia/CO₂ systems, but only HFC systems. The reasons given are the higher capital cost and extra planning and authorisation work for ammonia systems. This disregards the fact that the energy efficiency of systems with natural refrigerants is very high and their operating costs are usually lower.