When plate heat exchangers are used for wort cooling, there are two main methods, namely the two-stage cooling method and the one-stage cooling method. In the past, the two-stage cooling method was most commonly used, but now the single-stage cooling method is being used more and more.
Two-stage wort cooling method The two-stage plate heat exchanger consists of two parts, namely the middle plate and the intermediate plate. The first stage of cooling is using city water as the cooling medium. The wort is cooled from about 95°C (Celsius) to about 40-50°C. The cooling water is heated from about 20°C to about 55°C. The second stage of cooling is performed using a deep-cooling refrigerant (ethanol or glycol solution) as the cooling medium. The wort is further cooled to a fermentation temperature of about 7°C and the refrigerant temperature is raised from -4 to -3°C to about 0°C and returned to the recooling station. The heat exchange water from the first stage can be used as feed water.
Single-stage wort cooling method This method uses a cooling medium to cool the hot wort (approx. 95°C) to the temperature of the inoculated yeast (approx. 7°C). The cooling medium is brewing water, which is first cooled directly to 2-4℃ with ammonia (commonly known as ice water), heated to 75-80℃ after heat exchange with hot wort, and the water can be used directly as washing water.
Compared with two-stage cooling, single-stage cooling method has the following advantages. 1.) Simple equipment, no intermediate plate.
2.) The chiller of two-stage cooling should keep the refrigerant at -4~-3℃, and the burden of wort is reduced from 40~50℃ to about 7℃; the chiller of cooling should bear the cooling load from room temperature to 2~4℃ heat load. Therefore, compared with two-stage cooling method, single-stage cooling method can save about 20%-30% of energy.
3.) The cooling water outlet temperature of the first stage of two-stage cooling is about 55°C. If it is used for dosing, it needs to be heated. The cooling brewing water outlet temperature is suitable for washing and does not need to be heated, which can reduce coal consumption and lower water consumption.