What are the advantages of heat pump drying technology compared to traditional drying technology

What is the advantage between heat pump drying technology and traditional drying technology? At present, drying is used in almost all production processes in agriculture, food, chemicals, ceramics, medicine, mineral processing, pulp and paper making, wood processing and other industries. The quality of dry materials depends on whether the constant temperature is well controlled. The heat pump drying technology is a mild and nearly natural drying method, which is more suitable for drying most heat sensitive materials such as agricultural products and medicinal herbs.
The principle of a heat pump dryer is to use the inverse Carnot principle. The gas is pressurized by the compressor to become a high-temperature and high-pressure gas (with a temperature of up to 100 ℃), which enters the heat exchanger (condenser) on the indoor side. The refrigerant condenses and liquefies, releasing high-temperature heat to heat the air in the drying room. The materials in the drying room are vaporized and evaporated by hot air, and the evaporated water vapor is discharged by the dehumidification system to achieve the purpose of drying the materials. The heat pump dryer only needs to consume the electrical energy used by the compressor during operation, and can obtain more energy from the air, with an energy efficiency ratio of up to 400%, which is more energy-saving than other drying methods.
1、 The characteristics of traditional drying technology
Currently, most dehydrated vegetable production still uses the traditional drying method of heating and drying in the drying room, which has several problems:
1. The drying temperature is too high. The traditional drying technology makes it difficult to control the drying temperature, which is generally around 75-90 ℃. However, the dehydrated vegetable drying process requires that the drying temperature should not exceed 65 ℃.
2. Drying time is too long. Traditional drying techniques require at least 24 hours for processing 1 ton of vegetables, and sometimes rework is required due to poor drying results, resulting in longer processing times.
3. High energy consumption. Traditional drying techniques have low thermal efficiency, ranging from about 30% to 60%. During the drying process, the heat of evaporated water accounts for about 36%, the loss of exhaust gas accounts for about 58%, the heat carried away by dry materials and the heat loss of the dryer account for 2% and 2%, respectively, with a thermal efficiency of only 40%.
2、 Characteristics of Heat Pump Drying Technology
1. The drying temperature is low. The production process of heat pump drying technology is about 38-52 ℃ lower than traditional drying technology, that is, the heating temperature of heat pump drying technology is around 37 ℃.
2. Short drying time. The production process of heat pump drying dehydrated vegetables requires no more than 8 hours of time, usually completed from preheating to 4 hours of product output.
3. Good drying quality. The vegetables produced by the heat pump drying process have good color and stable internal quality.
4. Low energy consumption. Due to the use of air circulation in the heat pump drying process, the heating temperature is low, the drying time is short, and the capacity is large. So the heat pump drying process consumes less energy and is a good energy-saving product.
3、 Comparison of economic and technical indicators
The economic and technical indicators of heat pump drying technology are significantly higher than traditional drying technology, mainly reflected in energy conservation, quality, efficiency, and other aspects.
1. In terms of energy consumption: (1) Heat pump drying: According to testing, the heater processing 1 ton of fresh vegetables consumes 20kg of standard coal, the heat pump is 2.75kW, and the circulating fan consumes 0.2kW of electricity. Calculated based on 4 hours of operation, its energy consumption is 11.8kW, the conversion coefficient of standard coal is 407g/(kW • h), and the standard coal is 4.803kg. The total energy consumption is 20kg+4.803kg=24.803kg (standard coal); (2) Traditional drying: a total of 240kg of standard coal is consumed, and the power consumption of the circulating fan is 2.4kW. The conversion coefficient of standard coal is 407g/(kW • h), which is 0.977kg of standard coal. The total energy consumption is 240+0.977=240.977kg (standard coal). The energy-saving efficiency ratio of the two methods is: (1-24.803/240.977) × 100%=90%。
2. Quality aspect: Heat pump drying process, stable product quality, good color, and no residual substances such as SO2.
3. In terms of efficiency: The product is dried using a heat pump drying process, with qualified moisture content, no rework, and a short drying time.