Plate heat exchangers have been widely used in many industries. Many sugar mills in Europe, America, South Africa and India also use it in the heating of clear juice, dilute juice in the exudation method, the heating of the syrup molasses before entering the tank, and the final cooling of the molasses (before entering the waste honey tank), the effect is good, Some sugar mills are also used for heating mixed juice. Some good examples of applications are listed below.
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· 1. Used for clear juice heating
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· The Dalton sugar factory in South Africa uses a Plate heat exchanger, using 44 plates, each with a heating area of 0.79m2. The flow rate of clear juice is 130t / h, it is heated from 92 ℃ to 104 ℃, the saturation temperature of the waste steam used is 111 ℃, the heat transfer coefficient is 3400W / m2.K, the pressure drop of clear juice through the Heat Exchanger is 76kPa; Not fully open, that is, the actual temperature difference is still small, and the heat transfer coefficient is still higher. The juice heater is turned on after five weeks of continuous operation. There is some sludge deposited inside, and there is a black film on the board surface, which is easy to wash away with water. Nande Sugar Factory, Germany, sugar beet juice amount is 600t / h. Before the clear juice enters the evaporation tank, 4 plate heat exchangers are used to heat it in four stages. The juice vapor of the 1-4 effect evaporation tank is used as the heat source. The temperature reached by each stage of heating It is only 3 ℃ lower than the juice vapor temperature, and finally reaches 127 ℃.
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· In the 1980s, Guangzhou Overseas Chinese Sugar Factory (carbonic acid method) applied a Plate Heat Exchanger to the clear juice heating. The plate area was 0.79m2, 50 plates were installed, and the effective heating area was 37.9m2. Using the first effect juice steam, the amount of juice is 117t / h, the juice inlet temperature is 68.7 ℃, the juice outlet temperature is 100.7 ℃, the temperature rise is 32 ℃, the inlet steam temperature is 114.2 ℃, the drain temperature is 108.4 ℃, and the heat transfer coefficient K value is 4010W / m2 .K, the pressure drop of clear juice through the heat exchanger is 36kPa. Its discharge temperature is about 6 ℃ lower than the inlet steam temperature, and there is a little water in the device. If the drainage is smooth, the K value will be higher. The equipment was disassembled and inspected after more than ten days of continuous use, and the surface of most of the plates was still as smooth as new. There is very little dirt, which can be wiped off with a soft cloth.
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· Guangdong Shunde Sugar Factory (sulfite method) sugar factory uses a plate heat exchanger with a plate area of 1.07m2, which is used as the third-stage heating of clear juice. The average amount of sugar cane juice is 254t / h, the temperature of using waste steam is 129 ～ 130 ℃, the juice temperature before heating is 106 ～ 108 ℃, and the temperature after heating is 120 ～ 126 ℃, the heat transfer coefficient is 2400 ～ 3900 W / m2.K.
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· Guangdong Zhujiang Ganhua Plant uses a plate heat exchanger for the first-level heating of clear juice, with a heat transfer area of 35m2. After heating, the juice temperature is only 2 to 4 ° C lower than the steam temperature. After 15 days of use, the temperature difference is 4 to 6 ° C, and the heating temperature is higher than the original 60m2 tube heater. Its heat transfer coefficient is 2700 ～ 4000W / m2.K.
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· Another sulfite sugar factory uses a plate heat exchanger with a plate area of 0.36m2 and 90 pieces installed. The effective heat transfer area is 31.68m2. The first effect juice steam is used to heat the clear juice. The average measured data in seven days is: clear juice flow rate 37.2 t / h, the juice inlet temperature is 76 ℃, the juice outlet temperature is 107 ℃, the temperature rise is 31 ℃, the steam inlet temperature is 113 ℃, the steam condensate temperature is 112.5 ℃, and the heat transfer coefficient is 2300W / m2.K. After more than ten days of use, it is disassembled and inspected. There are few deposits on the surface of the plate, which can be washed off with water and a soft brush.
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· The heat transfer performance of heating clear juice with a plate heat exchanger is more than double that of the tube type, so the heat transfer area used can be reduced by half or more. It is better to use the first effect juice steam here, which has a certain energy saving effect (than heating with waste steam). In the case of good performance of the heat exchanger and close to the evaporation tank, the use of juice steam heating can make the juice temperature close to the juice vapor temperature, only 3 to 5 ℃ lower, which can basically meet the needs of evaporation. Juice steam heating can also prevent sugar juice coking due to excessive steam temperature. Some domestic sugar mills use waste steam, and some factories have suffered serious coking due to careless operation, and it is difficult to remove the coking matter.
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· 2. For heating mixed juice
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· The Dalton sugar factory in South Africa uses a plate heat exchanger to heat the mixed juice, 50 plates. Used for two months, cleaned once a week, the flow of cane juice is 103 ～ 130t / h, heated from 72 ～ 76 ℃ to 94 ～ 97 ℃, the saturation temperature of used steam is 109 ～ 111 ℃, the heat transfer coefficient is 2900 ～ 3380W /m2.K, the pressure drop of cane juice is 0.05 ～ 0.1MPa. When the shutdown is turned on, there is sediment and cane bran deposited inside, and there is a thin layer of scale on the board surface, but it is less than the tube heater, which can be rinsed with water and brushed off. Each work class conducts a "backwash" to wash away part of the sediment. But it is best to remove the fiber debris in the cane juice first with a sieve.
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· For materials such as mixed juice containing more solid suspended solids, the effect of using a wide-flow plate heat exchanger is better. A sugar sulphite factory abroad, using this heat exchanger and the third effect evaporation juice steam to heat the mixed juice and sulfur fumigation juice, can run continuously for 30 days, the juice vapor pressure used is very low, only 40kPa absolute pressure, Steam temperature is 75 ℃. The heat transfer coefficient reaches 2090 ～ 2440W / m2.K, and its heating area is more than half smaller than that of the tube type. Two sugar beet sugar plants in Poland (more than 2,000 tons of sugar beet per day) used a wide-slot plate heat exchanger in the mid-1990s, using juice vapor (temperature about 60 ° C) from a sugar canister to heat the exuded juice. The temperature is raised from about 30 ° C to about 50 ° C, then ash is added and heated to about 88 ° C with steam condensate and third effect juice steam. The operation condition is good, and it can be used continuously for a squeezing season. After shutdown, it can be sprayed with high-pressure water to remove all the deposits on the surface of the plate. It uses a large number of low-temperature heat sources, which significantly reduces the fuel consumption of sugar factories.
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· The wide-flow plate heat exchanger can use vacuum low-temperature juice vapor as a heat source to heat low-temperature cane juice, which has great energy-saving value.
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· 3. Used for molasses cooling
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· Molasses cooling before entering the storage tank is a key measure to prevent the deterioration of molasses during storage. However, the viscosity of molasses is large, heat transfer is difficult, and the effect of using a general heat exchanger is not great. In South Africa and Australia, it is better to use plate heat exchanger to cool molasses. Both Gladhow and Sezela sugar factories in South Africa use plate heat exchangers to cool molasses. The molasses flows one way in the container, and the cooling water passes through five passes. The size of the plates used by them is 1556 × 416mm, the number of plates is 96 and 160 respectively, the heat transfer area is 50 and 83m2, the amount of molasses processed is 11.5 and 12.6t / h, and the molasses hammer is about 81. The temperature of molasses, the former is cooled from 59.8 ℃ to 42.8 ℃, the latter is cooled from 62.1 ℃ to 36.7 ℃, the inlet and outlet temperature of cooling water, the former is 30.2 and 36.3 ℃, the latter is 23.3 and 46 ℃, the amount of cooling water is 13.8 And 6.1t / h; heat transfer coefficients are 96.3 and 112W / m2.K, respectively. The heat exchanger needs to be opened and cleaned with water once a month.
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· The Bingera sugar factory in Australia used a plate heat exchanger manufactured by the German GEA company to cool molasses in 1990. The model is B12, equipped with 149 pieces of V-shaped corrugated plates with a size of 1400 × 400mm. The heat exchange area is 67.6m2. Water is flowing one way. The actual amount of molasses processed is 10 ～ 15t / h. The temperature of molasses is reduced from 57 ～ 62 ℃ to about 37 ℃. The temperature of cold water used is 32 ～ 35 ℃. The amount of water is automatically adjusted according to the temperature, which is 1.5 ～ 3 times of the amount of molasses. The heat transfer coefficient is 200 ～ 550W / m2.K. The pressure drop of molasses is 50 ～ 150kPa. The equipment runs normally during the full squeezing season (it was disassembled for inspection and cleaning in the middle), and the stainless steel plate (model 316SS) has no visible corrosion. The cold water used must be clean. Lower temperature river water has been tried, but it will form soft attachments between the plates and hinder heat transfer.
