How to use organic heat carrier in spunbond non-woven equipment

Organic heat carrier is a general term for organic substances used as heat transfer medium, including heat transfer fluid, heat transfer oil, heat medium, etc., which is an organic medium used for indirect heat transfer. Because of its ability to generate high temperature under lower vapor pressure, high heat transfer efficiency, and convenient transportation, it is widely used in various industrial fields.


The spunbonded non-woven fabric process mainly uses polyester and polypropylene as raw materials. After the polymer is extruded and stretched to form continuous filaments, the filaments are laid into a net, and the fiber net is then bonded by itself, thermally bonded, Chemical bonding or mechanical reinforcement methods make the web into a non-woven fabric.


1. Thermal characteristics of equipment used in spunbond non-woven fabric industry


Taking the process flow of PP as the main raw material as an example, the equipment heat of spunbonded non-woven fabrics is mainly concentrated in the main screw, filter, meter, spinning box and hot rolling mill. Due to the difference in equipment structure, the above 5 parts use organic heat carrier to heat or keep the products and equipment in whole or in part. We divide it into three major parts, and the heating temperature varies with different raw materials.


2. Organic heat carrier used in spunbond non-woven fabric industry equipment is taboo against overheating


(1) Concept


Under the operating conditions of the heat transfer system, the average main fluid temperature of the heat transfer oil measured at the outlet of the heating element of the system is the working temperature; the maximum main fluid temperature of the heat transfer oil allowed at the outlet of the system heating element is the maximum working temperature. The temperature of the organic heat carrier exceeds its maximum allowable use temperature, that is, overheating. The 'Boiler Safety Technical Supervision Regulations' stipulates that the maximum operating temperature of the organic heat carrier should not be higher than its natural point. When the temperature is at least 10°C lower than the maximum allowable use temperature, and the average mainstream density of the radiant heating surface of the heating element is greater than 50kw/m, the maximum operating temperature of the organic heat carrier should be lower than its maximum allowable use temperature 20°C.


There is a difference between the maximum allowable use temperature of oil and the maximum operating temperature of the system because the highest point of the system medium temperature appears in the boundary layer that is in direct contact with the heating element, and the temperature obtained on the instrument side is the average main fluid temperature of the medium.


(2) Causes of overheating


① The maximum allowable working temperature of the selected oil is lower than the system working temperature;


②The temperature of the oil product is too fast when the system starts;


③The maximum heat flux density on the surface of the metal sheath of the electric heating element is greater than 20kw/m;


④ The flow velocity of the medium around the heating element is lower than 2m/s.


(3) Overheating hazards


Thermal cracking will occur after the oil temperature exceeds the maximum temperature it can withstand, and the cracking deterioration rate will increase exponentially with the continuous increase in temperature, and the deterioration rate of the organic heat carrier will increase, and sludge will gradually form in the system , Coking, reduce heat exchange efficiency, increase circulating pump load, and increase energy consumption.


3. Conclusion


The heat used in spunbond non-woven equipment is mostly in the form of electric heating. In the process of using organic heat carrier for heat transfer, it should prevent the occurrence of medium over-temperature, thermal oxidation and leakage to ensure the safety of operators and the normal operation of the equipment .