Thermal Oil Heating System
In the wood based panel industry, thermocompressor is they key equipment which used to produce plywood, medium density fibre board, chip board and so on. The thermocompressor normally direct heated by electricity and heat carrier fluid (steam, water or thermal oil) During the process, the wood panel surface is contact with thermocompressor and rise to a very high temperature, waters in the wood panel become steam, there will be a temperature between the panel surface and the inside. Heated steam and water carries the thermal energy to heat the panel inside. This heating system is composed of wood, air and water, the heat transfer property is actually poor. It takes time to heat the panel inside to reach the desired temperature. This method is not suitable for thick panel product. There are some requirement of the heating medium for direct heating 1. Large heat capacity, good heat conduction performance.
- Good thermostability, nonflammable
- Non toxic, odorless, non-corrosiveness
- Low cost
Compare of steam and super heated water, thermal oil is the most ideal fluid to be used in wood base panel industry. Especially for plywood, chip wood and fibre wood product. Why? 1. Steam The temperature of saturated steam is depends on the pressure. The higher temperature requires higher pressure. For example, if operator want the steam to be 200℃, the pressure is 1.6 Mpa, if 220℃, the pressure will be 2.3Mpa. After heated the plywood, steam temperature decreased and steam become condensate water, condensate water will effect the steam circulation and effect the steam heating capacity. When use steam boiler to make plywood product, you must discharge the condensate water in time. Or else it will effect the whole production process. Disadvantages: 1. The max temperature is around 200℃, the steam pressure is around 1.6Mpa. The steam boiler pressure is at least 2.5Mpa. Customer will have to invest a lot of money for the boiler and pipeline connection. 2. There are great energy wasted during the process of heating the water to 100℃.after the steam become condensate water, there are also thermal energy remains in the water but can not be used. Because the water will be discharged directly. 3. The thermal energy loss during the circulation is large! And the steam is hardly to be recycled. The overall energy utilizationis only 30~40%. 4. Steam flows too fast during the process (20~30m/s), it is hard to keep the temperature stable during the process.
|Steam||Superheated Steam||Superheated Water|
|Heat Capacity kj/m³||22,136||13,222||741,064|
2. Super heated water: This is a closed loop circulation heating system. As it shown in the table, superheated water has the largest heat capacity at temperature 200℃, about 30 times of steam. During the wood based panel production process, the fluid volume is fixed, to provide the same thermal energy, superheated water pipe is much more small than steam pipes. Also, superheated water can be recycle used in the process. The flow speed is slower than steam so the thermal efficiency is high. The overall energy utilization is about 40%~50%. Disadvantages: It requires high pressure water container and high pressure boiler, the overall system is complicated, and the circulation system is work under high pressure too. There are scale deposit produced during the process and this material will corrode the equipment. To avoid this problem, customer have to choose condensate water. 3. Thermal oil heating system Thermal fluid heating system can provide 320℃ high temperature and work under low pressure. Thermal oil heater is applied in the wood based panel industry since 1980s, nowadays it become more and more applied in medium density fibre board industry, chip board industry, plywood industry and so on. Thermal oil is almost a perfect heat carrier during the wood base panel production process. And it will finally replace all of the steam boiler. Thermal oil heater provide 300℃ high temperature at 0.4~0.6 Mpa pressure. Thermal fluid heating system is a closed loop circulation system, it provide a uniform heat transfer process. Operator can control the temperature accurate, temperature accuracy is ±1~2 ℃ Thermal oil heater is a energy saving equipment, there is no heat loss during the process, thermal oil can be recycle used. he overall energy utilization is about 60%. There is no corrosion during the process.the service life is much longer than traditional steam boiler. Thermal oil heating system do not require large scale room, do not need large water treatment equipment, do not need large water storage container, do not need high pressure pump. There is only little running cost and maintenance cost.