{"id":895,"date":"2024-07-19T14:13:52","date_gmt":"2024-07-19T12:13:52","guid":{"rendered":"https:\/\/handbook.kanco2.no\/?page_id=895"},"modified":"2024-08-15T14:00:30","modified_gmt":"2024-08-15T12:00:30","slug":"cooling-of-unused-waste-heat","status":"publish","type":"page","link":"https:\/\/handbook.kanco2.no\/en\/smarte-integrasjoner-av-co2-fangstanleggog-energigjenvinningsanlegg\/kjoling-av-ubenyttet-spillvarme\/","title":{"rendered":"Cooling of unused waste heat"},"content":{"rendered":"
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Chapter 3<\/p>\n\n\n

Cooling of unused waste heat<\/h2><\/div>\n\n\n\n
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Chapter 3<\/h2>\n\n\n\n
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Description of the energy system<\/a><\/div>\n\n\n\n
Smart integrations per technology<\/a><\/div>\n\n\n\n
Smart integrations<\/a><\/div>\n\n\n\n
Measures in existing waste incineration plants<\/a><\/div>\n\n\n\n
Heat supply to capture plants<\/a><\/div>\n\n\n\n
Recovery of waste heat from capture plants<\/a><\/div>\n\n\n\n
Cooling of unused waste heat<\/a><\/div>\n\n\n\n
Other measures for the use of waste heat<\/a><\/div>\n\n\n\n
Conclusion<\/a><\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n\n\n\n
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The capture plant has a continuous cooling requirement of 20.2 MW, regardless of the seasons. For \"KAN Referansa\" it is essential that the heat can be cooled away when it cannot be delivered to the DH network. That is, a cooling system must be installed that can cool 20.2 MW on a 'hot' day. When the DH requirement is present in winter, heat pumps will cover much of the cooling from the capture plant.<\/p>\n\n\n\n

If it is essential to cut the maximum power requirement for cooling, the solution with a HP supplying steam to the capture plant can be profitable, which will cut the maximum cooling power from the capture plant to 14.7 MW. This will require more cooling of heat from the waste incineration plant, but it is reasonable to assume that the infrastructure for this already exists.<\/p>\n\n\n\n

If it is possible to take the heat from the capture plant (2.6 MW from OH condenser and CO2 compression and liquefaction) directly to the DH grid on the return, this should be used. As shown in Figure 2, the DH grid always has a heat requirement of at least approx. 6.5 MW. This will mean that the capture plant will only need an installed cooling capacity of 17.6 MW. In GWh over the year, it will increase the cooling of the turbine heat, but there is already installed cooling capacity for this.<\/p>\n\n\n\n

8.1 Local Cooling - Dry Cooling\/Cooling Tower<\/h3>\n\n\n\n

The reference plant has assumed that all waste heat will be cooled through dry coolers on the roof. Dry coolers are at the mercy of the outside temperature, it is assumed that the Dimensioning Outdoor Temperature (DOT) is not warmer than 25 \u00b0C, and on days when it is possibly warmer than 25 \u00b0C it can be accepted that the cooling water back to the capture plant will be somewhat warmer than 25 \u00b0C. Some capture technologies will have the ability to vary the round-trip temperature of cooling water according to season. It is about 110 hours per year with outdoor temperatures warmer than 25 \u00b0C. Subchapters 8.5, 8.6 and 8.7 cover possibilities for cooling down to 25 \u00b0C cooling water when the outside temperature is 25 \u00b0C or higher.<\/p>\n\n\n\n

For simple calculations of electricity consumption, it is assumed that the average outdoor temperature when cooling is needed is 15 \u00b0C, and that the air is heated to close to 25 \u00b0C. Furthermore, a power consumption of 0.09 W\/(m3\/hr) of air is assumed. When calculating area requirements, it is assumed that there is 2 \u00b0C between the outside temperature and the cooling water temperature, in addition to 50 % relative humidity.<\/p>\n\n\n\n

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Dry coolers have a significant area requirement, figures from suppliers show that the area requirement is approx. 0.032 m2\/kW cooling power (assuming 2 \u00b0C between outside temperature and cooling water temperature). The need for space becomes even greater if there are restrictions on sound levels.<\/p>\n\n\n\n

A total area requirement of approx. 640 m2 for the carbon capture plant if the heat from OH condenser and CO2 compression and liquefaction cannot be used directly for the DH return is required. <\/p>\n\n\n\n

The area requirement will be approximately 560 m2if the heat from OH condenser and CO2 compression and liquefaction can be used directly for the DH return.<\/p>\n\n\n\n

If the waste heat is used through a HP for steam production for the capture plant, the area requirement will be 425 m2, as part of the cooling requirement is covered by HP. <\/p>\n\n\n\n

If you use the waste heat through a HP for steam production to the capture plant and extract the high-temperature heat OH condenser and CO2 compression directly to the DH return, the area requirement is 340 m2, as the cooling is covered by the DH return and steam producing HP.<\/p>\n<\/div>\n<\/div>\n<\/div>\n\n\n\n

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A typical dry cooler block in a V layout is shown in Figure 62.<\/p>\n\n\n\n

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Figure 62 Typical V-layout for dry chillers (Source: ThermoKey Heat Exchange Solutions)<\/figcaption><\/figure>\n\n\n\n
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This is not included in the area requirement for cooling for the heat from the turbines in the summer, as it is reasonable to assume that a cooling effect has already been installed for this. For some waste incineration plants, this can cause noise level challenges, which should be carefully considered. Requirements for lower sound levels typically result in lower fan speeds and the need for larger heat exchange areas. Relevant suppliers are ABK-Qviller, Kelvion, Thermo Control, Eptec, Aircoil, Reftec, etc.<\/p>\n\n\n\n

8.2 Increased inlet temperature of absorber<\/h3>\n\n\n\n

It is normal to assume\/specify an inlet temperature for flue gas to absorber of approx. 40 \u00b0C, this depends on the capture supplier. The temperature specification implies a significant cooling requirement for incoming flue gas in the capture plant's direct contact cooler. <\/p>\n\n\n\n

Studies carried out by a player in the KAN network (Stat-kraft) together with TCM show that although higher inlet temperature (up to 55 \u00b0C) results in slightly increased heat demand in stripper (reboiler duty), the reduced cooling requirement and effect on heat integration is so significant that higher inlet temperature should be considered. For this study, as previously mentioned in subchapters 6.3 and 7.2, an inlet temperature of 55 \u00b0C has been assumed. It is perhaps somewhat more realistic that this one is lower.<\/p>\n\n\n\n

8.3 Use of the district heating system as a cooling source<\/h3>\n\n\n\n

Normally, the return temperature in a district heating system is so high (55-70 \u00b0C) that it can contribute little or no cooling of a CO2 capture plant without the use of heat pump technologies (see Chapter 7). <\/p>\n\n\n\n

If the return temperature in district heating is sufficiently low, it can be used to cool the capture plant partially or completely by direct heat exchange, without the use of heat pumps. This would be highly energy efficient and cost effective.<\/p>\n\n\n\n

Two of the players in the KAN network have therefore investigated whether it is possible to use the district heating system itself to a greater extent as a cooling source with a greatly reduced return temperature. In the two studies, it was investigated whether it was possible to reduce the return temperature of district heating by heat exchange of the return flow towards a low-temperature heat load (e.g. seawater cooling) elsewhere in the district heating system. Such cooling of DH return enables a significantly higher proportion of direct heat exchange without the need for heat pumps. The solution would also utilize existing infrastructure in a very efficient way since existing pipeline networks can be used. Such a scheme is feasible, but the management of such a system was considered slow and difficult to control. The two companies chose not to further develop the concept of artificial cooling of DH return. <\/p>\n\n\n\n

Actions to reduce the return temperature from DH customers will always be positive and improve the capacity and efficiency of the district heating system.<\/p>\n\n\n\n

If the supply of cooling to the capture plant is limited (for example by very high air temperatures on a hot summer day or little surplus area), one or more of the heat pumps (described in Chapter 7) may be a solution to ensure the final cooling of the plant by compulsory upgrading of energy to the DH network. Such forced upgrading of the waste heat will cause the extra added heat to be; <\/p>\n\n\n\n