a Organic heat carriers are divided into two major categories, mineral oils and synthetics. The mineral oil-based organic heat carrier is produced by the high-temperature cracking or catalytic cracking of petroleum, and the formed distillate oil is refined as a raw material. Synthetic organic heat carrier is made of chemical or petroleum as raw material by organic synthesis process, such as biphenyl. In order to ensure the normal use of organic heat carriers, the quality and performance indicators, such as the maximum use of temperature, viscosity, flash point, residual carbon, acid value, etc. should be specified.
1. Maximum operating temperature. The allowable film temperature of the organic heat carrier is a very important indicator. In the thermal calculation, the mainstream temperature of the organic heat carrier is determined so as to ensure the normal use of the organic heat carrier. The relevant foreign regulations are also so stipulated.
2. Viscosity refers to the degree of dilute thickness and fluidity of the organic heat carrier under the specified conditions (as measured by GB 256-88). The greater the viscosity, the poorer the fluidity, the greater the power of the circulating pump and the more difficult the pipeline transportation. If the change in viscosity value exceeds 15% of the original technical indicator, the organic heat carrier should not be used.
3. The flash point is the lowest temperature at which the flash flame occurs when the flame approaches, after the organic heat carrier vapor and air are mixed together 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. The use of organic heat carrier for a long time or improper use may cause the flash point of the organic heat carrier to decrease. According to GB267-88 standard, when the flash point change exceeds 20% of the original index, it should be stopped.
4. Residual carbon refers to carbon residue that is decomposed, polymerized, and precipitated when the organic heat carrier is overheated by heating. The main components of residual carbon are colloids, indoline and polycyclic aromatic hydrocarbons in organic heat carriers. The size of the residual carbon 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 not be used again.
5. The acid value refers to the total content of organic acids in the organic heat carrier. Organic organic acids do not corrode metals when the organic heat carrier temperature is ≤100°C and there is no moisture. When the temperature of the organic heat carrier exceeds 100° C., the organic acid corrodes 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 lower than 0.02 mgKOH/g, and if it exceeds 0.5 mgKOH/g, the use should be stopped.
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