Systems absorption cooling

LITHIUM BROMIDE - A chemical used in combination with water in absorption cooling systems. 

If we consider the case in which both the SOFC and PEM systems have the same power output and efficiency, then the heat, which is the enthalpy content, of the exhaust streams produced by both systems will be the same. However, the heat produced by the SOFC will be at a higher temperature and therefore has a higher exergy than that from a PEM fuel cell. We can, therefore, say that the heat from an SOFC is more valuable. The heat that is liberated in a PEM fuel cell is around 80°C and has limited use both within the system and for external applications. For the latter, it may be limited to air space heating, or possibly integration with an absorption cooling system. The heat that is produced by an SOFC on the other hand is exhausted at temperatures of around 1000°C and is clearly more valuable, as it can also be used, as we have seen, in a bottoming cycle. 

Steam and cooling water requirements for ammonia absorption refrigeration systems are shown in Table 1 for single-stage and two-stage units. The tables are based upon cooling water to the condenser of 85°F with 100°F condensing temperature. Water from the condenser is used in the absorbers. 

Steam and Cooling Water Required for Ammonia Absorption Refrigeration Systems... 

The thermal compression or absorption refrigeration systems are less common. They do not require a compressor. Their energy source is steam, natural gas, or waste heat. This system requires much more cooling water than the previous one, but may be economical if a large amount of waste heat is available.21 See references 20 and 21 to determine heat and cooling water requirements. 

One of the most notorious cases of industrial disaster took place in 1984 in Bhopal, India. A plant with a license from the Union Carbide company was making methyl isocyanate (MIC), CH3NCO, which is an intermediate for the manufacture of pesticides. MIC boils at 39 °C, and the vapor density is heavier than air and very toxic by inhalation and skin absorption. The maximum allowable air concentration is 0.02 ppm by volume over 8 h. MIC also reacts with water and produces heat, which must be removed to prevent boiling over. On that day in 1984, the cooling system failed during... 

The cooled process gas that leaves the Syngas Scrubber is fed to the Amine unit. The amine unit consists of an absorption-stripping system plus associated equipment. In this system a circulating amine stream (activated MDEA - or Methyl Diethanolamine) absorbs the C02 in the C02 Absorber. The amine is regenerated in the C02 Stripper with the C02 being recycled to the compressor. 

Alien a process requires temperatures lower than those attainable by cooling water (less than 10(FF), refrigeration must be used. Most refrigeration systems use compression refrigeration, but occasionally absorption refrigeration systems are employed if an inexpensive low-level heat source is available. 

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