a organic heat carrier is divided into two major categories of mineral oil type and synthetic type. The mineral oil type organic heat carrier is formed by exchanging the distillate oil formed as a raw material in the process of high temperature cracking or catalytic cracking of petroleum. Synthetic organic heat carrier is made of chemical or petroleum as raw material through organic synthesis process, such as biphenyl. In order to ensure the normal use of the organic heat carrier, its quality and performance indicators, such as the maximum use temperature, viscosity, flash point, residual carbon, acid value, etc. should be specified.
1. Maximum use temperature. The allowable membrane temperature of the organic heat carrier is an important indicator to determine the mainstream temperature of the organic heat carrier during thermal calculation to ensure proper use of the organic heat carrier. The relevant foreign regulations are also stipulated.
2. Viscosity refers to the degree of alkalinity of the organic heat carrier and the fluidity (measured according to GB256-88) under specified conditions. The greater the viscosity, the worse the fluidity, the greater the power of the circulation pump, and the more difficult it is to transport the pipeline. If the viscosity value changes by more than 15% of the original specification, the organic heat carrier should not be used continuously.
3. The flash point refers to the lowest temperature at which short flashing occurs when the flame approaches when the organic heat carrier vapor and air form a mixed gas under heating conditions. The lower the flash point, the greater the evaporation rate of the organic heat carrier and the worse the safety, and vice versa. At the same time, the higher the flash point, the smaller the loss of the organic heat carrier during use. If the organic heat carrier is used for a long time or improperly used, the flash point of the organic heat carrier may be lowered. According to the GB267-88 standard, when the flash point changes more than 20% of the original index, it should be stopped.
4. Residual carbon refers to residual carbon which is formed by decomposition and polymerization of an organic heat carrier when it is heated to an excessive temperature. The main components of residual carbon are colloidal, qingqing and polycyclic aromatic hydrocarbons in organic heat carriers. The magnitude of the residual carbon value can be used to determine the tendency of the organic heat carrier to coke. Generally controlled at 0.02W%, when the residual carbon value exceeds 1.5W%, it should be regenerated, otherwise it can no longer be used.
5. The acid value refers to the total content of organic acids in the organic heat carrier. When the organic heat carrier temperature is â‰¤ 100 Â° C and there is no moisture, the organic acid does not corrode the metal. When the temperature of the organic heat carrier exceeds 100 Â° C, the organic acid is also corrosive to the metal as the temperature and the acid value increase. In order to reduce the corrosion of metals by organic acids, the acid value should generally be less than 0.02 mg KOH / g, such as more than 0.5 mg KOH / g, should be discontinued.
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