Introduction of heat pump drying technology and its application cases

The generation and drying of heat pump dryer is an essential process in many industrial production and agricultural and sideline products processing With the progress of people's life quality, the awareness of environmental protection is becoming stronger and stronger, and the reserves of energy (such as natural gas, coal, oil) are increasingly exhausted The use of the original drying equipment with high energy consumption and high pollution, such as fuel oil and coal, is strictly restricted or even prohibited It is more and more urgent to find a kind of drying equipment which can replace the old one and is safe, environmental friendly and energy-saving Heat pump drying equipment came into being in this environment The history of heat pump drying technology since the 1970s, the United States, Japan, France, Germany and other countries have carried out the research of heat pump drying technology The International Energy Center (IEA) has concentrated a lot of research results on heat pump drying technology China also introduced this technology in the 1980s Zui was used for wood drying early and widely Due to the low temperature of heat pump drying, which is close to natural drying, it has been gradually applied to the drying of food and agricultural and sideline products in recent years, with good economic benefits and great progress in added value of products In particular, the implementation of energy conservation and environmental protection policies of our government has greatly promoted the development of heat pump drying technology Materials processed by heat pump drying equipment have also expanded from early wood drying to food processing, tea drying, tobacco drying, vegetable dehydration, fish drying, ceramic baking, sterilization and drying of drugs and biological products, sludge treatment, chemical raw materials and fertilizer drying and many other fields The principle of heat pump dryer the heat pump dryer is to use the inverse Carnot principle to absorb the heat of air and transfer it to the room, to achieve the temperature progress of the drying room, with the corresponding equipment to achieve the drying of materials The heat pump dryer is composed of compressor - heat exchanger (internal) - restrictor - heat receiver (external) - compressor and other devices to form a cycle system The refrigerant circulates in the system under the action of compressor It completes the process of gas pressure rise and temperature rise in the compressor (the temperature is as high as 100 ℃), it enters the internal machine and releases the high temperature heat to heat the air in the drying room, at the same time, it is cooled and transformed into liquid flow When it runs to the external machine, the liquid rapidly absorbs heat and evaporates again into gas state, and the temperature drops to - 20 ℃ - 30 ℃, at this time, the air around the heat absorber will be the source Continuously transfer heat to the refrigerant The continuous circulation of the refrigerant realizes the transfer of the heat in the air to the air temperature in the heating room of the drying room The operation principle of heat pump dryer is as follows: compared with other types of dryer, heat pump dryer has the advantages of energy saving and low operation cost Corresponding to the comparison of operating costs of various energy sources: the energy costs are as follows: the same generation of 86000kcal heat, the comparison of operating costs of the dryer From the above data, it can be seen that the operation cost of heat pump dryer is only 30% of electric heating dryer, 40% of fuel oil dryer and 60% of coal-fired dryer Moreover, the heat pump dryer does not need to consume any fuel, which saves the cost of transportation and storage of fuel, and the economic benefit is more obvious 2 Safety and environmental protection Heat pump dryer is to transfer the heat in the air to the drying room to achieve the purpose of drying, so it only consumes the electricity to carry the heat There is no need to consume other fuels, that is, to avoid the problems of safety and environmental pollution in the transportation and storage of fuels The operation process does not produce any pollutants 3 Good drying effect Because the heat pump dryer adopts automatic control, the operation state of the unit can be adjusted automatically according to the setting mode Stable temperature rise, uniform temperature, less temperature fluctuation Avoid the influence of human factors on the drying quality during the operation of fuel dryer Application case of heat pump drying technology heat pump drying technology is applied to tobacco drying industry Take Foshan kechuangda cold and hot equipment manufacturing Co., Ltd as an example in Hunan Province in 2007 The air space in the flue-cured room of the project is 8 * 2.7 * 3.16M, about 68m3 The capacity of flue gas in the baking room is 3500-5000kg fresh flue gas Originally, the drying equipment with coal as fuel was used for baking Now, the heat pump drying equipment is used as the heat source to bake the flue gas Foshan kechuangda cold and hot equipment manufacturing Co., Ltd has equipped two paka-180d (3P) heat pump drying units according to the project situation From the perspective of operation, Paka heat pump dryer has been operating normally, not easily affected by the weather and environment, and the unit is safe, reliable and easy to operate Both farmers and tobacco companies are satisfied with the use effect The specific evaluation is as follows: 1 Safety: there is an open fire in the original coal-fired baking house using coal as fuel, which may cause tobacco burning due to leakage of fire, resulting in huge losses for farmers The Paka heat pump baking machine (including power supply) is installed outside the baking house, and the heat is transferred from the heat pipe to the heating device of the baking house for heating, so there is no open fire in the baking house, so it is safe to do so 　　 2 Environmental protection: the original coal-fired baking house uses coal as fuel to bake, and emits toxic gases such as carbon dioxide and sulfur dioxide, which are harmful to human health The other dust and smoke emitted by the house greatly reduces the air cleanliness, and the stacking site seriously affects the surrounding environmental health However, the Paka heat pump baking house has no emission, which has no impact and harm on human body and the environment, so that the farmers and the residents in the smoking area are completely affected Farewell to the smoky labor and living environment 3 Energy saving: the average cost of a room of flue-cured tobacco in the original coal-fired baking room is about 600 yuan, and the cost of a Paka heat pump baking room with the same area is only about 420 yuan Compared with the cost of a Paka heat pump baking room, the cost is reduced by 30%, and the baking room adopts intelligent automatic control, without the need for special personnel to take care of it, and the labor cost is reduced by about 60% 　　 4 High quality: the original coal-fired baking house uses artificial combustion combustible materials to control the temperature Due to the influence of the temperature control by the factors such as the farmers' burning technology, physiological characteristics (rest), the quality of combustion materials and processing quality, the baking technical requirements are not met, resulting in the instability of the quality of tobacco leaves The Paka heat pump baking house has completely solved the automation and degree control of the heat source Therefore, the temperature control is up to ± 1 ℃, thus improving the tobacco baking quality 5 Labor saving: the original coal-fired baking houses are heated by artificial combustion materials, requiring a large number of labor to purchase or process fuel, and constantly adding or reducing materials to control the temperature during baking, so that the labor intensity of tobacco farmers is very large The Paka heat pump baking room can automatically control the temperature and humidity, without any fuel, which greatly reduces the labor intensity of tobacco farmers, and can bake multiple baking rooms at the same time very easily 6 Time saving: due to the misoperation and burning time, the temperature in the coal-fired baking room is slow, which leads to the waste of baking time Paka heat pump baking room has fast temperature rise, correct temperature control, programmed setting, so as to achieve the standardization of baking time, It can save more than 24 hours to bake tobacco evenly in each room Prospect of heat pump drying technology The material drying process is a huge energy consumption process According to statistics, in most developed countries, the energy used for drying accounts for 7% - 15% of the total energy consumption of the country, while the thermal efficiency is only 25% - 50% [26], and most of the drying processes, especially for heat sensitive materials such as food and biological materials, will have an impact on their luster, nutrition, flavor and organization Heat pump drying technology has the advantages of less energy consumption, less environmental pollution, high drying quality and wide application range Its excellent energy-saving effect has been confirmed by various domestic and foreign experimental research institutes At present, heat pump drying is developing towards the improvement of drying temperature, the development of new heat pump drying system, and the automatic control technology of heat pump As a technology that can reduce energy consumption and improve product quality, heat pump drying will bring significant technological revolution to the drying industry.