Brewery Setup Blog

Cooling method of wort

There are two cooling methods for wort: one cooling method and two cooling methods. However, in terms of energy saving and control, the primary cooling mode is more and more used today.

(1) Two stage cooling

The two-stage plate heat exchanger is composed of front and rear sections. An intermediate plate is installed between the two sections. Cold water is used for cooling in the front section, and refrigerant (such as glycol or alcohol solution) is used for cooling in the rear section. The cooling water temperature of the front section should be below 20 ℃. After the cooling of the front section, the wort temperature should be reduced to 40 ℃ ~ 50 ℃; After cooling, the temperature of wort should be reduced to fermentation temperature. The water after heat exchange in the front section can be used as feeding water.

The plate heat exchanger has a resistance of 0.25 ~ 0.35Mpa. Wort and coolant need to be pumped to directly cool the wort of 90 ~ 95 ℃ from the rotary sedimentation tank to the fermentation temperature. The cooling time should be controlled within 1 h to match the production capacity of gyratory sedimentation tank. Therefore, the production capacity of plate heat exchanger is required to be larger.

After the plate heat exchanger is used, it must be fully circulated with hot water and hot alkaline water for washing and sterilization to prevent scaling and affect the heat exchange effect.

(2) Primary cooling

The primary cooling  , the brewing water is cooled to 3 ℃ ~ 4 ℃ (this water is commonly known as ice water) by direct ammonia cooling, and then one-time heat exchange is carried out with hot wort in the plate heat exchanger. When the wort is cooled to the fermentation temperature, the ice water is heated to about 75 ℃ ~ 80 ℃. This water can be directly used as washing water.

Compared with the two-stage heat exchanger, the one-stage plate heat exchanger has only one section, no intermediate plate and simple structure.

The main points of primary cooling technology are as follows:

A. The import temperature of wort is about 95 ℃.

B. The cooling time should be controlled within 1 h. too long cooling time will affect the utilization rate and efficiency of gyratory sedimentation tank Juice quality.

C. The pumping pressure of wort and ice water is 0.1 ~ 0.15Mpa.

D. The proportion of wort and ice water consumption was 1: (1.2-1.4).

E. The water temperature for cleaning and sterilization is 85 ℃ ~ 90 ℃; The washing temperature of alkaline water is 75 ℃ ~ 80 ℃.

F. The time of cleaning and sterilization with pump circulation is 20 ~ 30min

G. The temperature of cooling medium ice water is 3 ℃ ~ 4 ℃

Preparation of ice water: brewing water is pumped to ammonia evaporator, cooled to 3 ℃ ~ 4 ℃ and stored in ice water tank for standby. The ammonia evaporator adopts multi pass heat exchanger with tube sheet structure. There is a water channel in the pipe, and the refrigerant evaporates between the pipes. During the preparation of ice water, ice should be prevented, the flow rate of water in the pipe should be greater than 0.8m/s, and the ammonia evaporation pressure should be controlled in the range of 0.2 ~ 0.3MPa.

(3) Comparison of one stage cooling and two stage cooling

The second stage of two-stage cooling is refrigerant, which exchanges heat with hot wort higher than local water temperature; The first stage of cooling is to freeze the local brewing water.

The main advantages of primary cooling are as follows:

A. In the first stage, brewing water is used as refrigerant without alcohol or glycol.

B compared with two-stage cooling, the temperature of hot water is much higher, and the utilization rate of heat energy in saccharification chamber is greatly improved.

C. During the two-stage cooling operation, water and refrigerant should be used at the same time, and the temperature changes greatly during the cooling process, which is not easy to be stable;In the process of primary cooling, only ice water is used as the refrigerant, the parameters of cold and hot medium are unchanged, the operation is stable and easy to control.

D.Because the logarithmic average temperature difference of heat exchange between cold medium and hot medium is smaller than that of two-stage cooling, the heat exchange surface of d-stage cooling is smaller than that of two-stage cooling.Compared with the two-stage cooling, the accumulated heat needs to be increased by 45%. However, there is no peak load in the primary cooling, so the load of the refrigerator is relatively light and the installed capacity is small.

E. In general, one-stage cooling can save 30% ~ 40% power compared with two-stage cooling.

(4) Precautions for primary cooling operation

The maximum allowable working pressure of plate heat exchanger is generally 1MPa. Generally speaking, the normal working pressure is 0.2MPa, and the maximum is 0.4MPa. Because too high differential pressure will deform the thin plate and reduce the sealing performance of the sealing ring, it is not allowed to increase the differential pressure at will.

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