Optimizing the Performance of Process Heaters
Process heaters play an important role in thermal systems. Effective use of heaters helps industries save energy and maximize the efficiency of their processes.
Thermal insulation is one of the most common practices used to minimize energy loss in heat generation, transfer, and transmission processes, while insulation and refractories are used to enhance the efficiency of boilers, ovens, furnaces, storage tanks, heaters etc.
What are refractories and insulation systems made of? These industrial energy savers are made of non-metallic materials that have low thermal conductivity. They help to maximize the overall efficiency of process heating systems by reducing heat loss, maintaining desired temperature, enhancing heat transfer, reducing heat storage, and so on. Although properly designed insulation systems can significantly increase the efficiency of thermal systems, they cannot fully eliminate heat losses in thermal processes.
Apart from heat loss, the efficiency of a process heating system can be significantly lowered by poor performance of a heater. The effectiveness of an electric heater can be optimized through the following ways:
i. Supply heater with regulated voltage
An overvoltage can cause a heater to fail or damage the equipment that it is attached to. To avoid this, a heater should always be supplied with a regulated voltage that matches its rated value. Ensuring that a heater is supplied with its rated voltage also helps to lengthen its life.
ii. Ground the equipment
Incorrect grounding or lack of it can cause damages to the entire heating system in case of electrical failure. To avoid such damages, the equipment that a heater is attached to should be properly grounded. This also helps to protect personnel from injuries in case of an electrical failure.
iii. Use temperature control systems
A thermal system should have a process temperature control system and a high limit control system. PID temperature controllers are recommended because they offer fast response and high accuracy temperature control. In addition, they provide more stable control than thermostats or ON/OFF switching controls. However, PID temperature controllers are more expensive.
iv. Prevent heater contamination
Accumulation of organic or conductive contaminants on heater elements can cause it to fail. When the contaminants accumulate on heater windings, they can cause arcing failure and lower the effectiveness of a heater. Conductive contaminants can short power terminals and damage the heater. Oils, lubricants, and processing materials should not be allowed to come into contact with heater leads.
v. Avoid exposing leads and terminations to high temperature
Excessive vibrations and high temperatures can damage the leads of a heater. For ambient temperature applications, fibreglass-insulated lead wires can be used. For higher temperatures, ceramic bead insulation or high-temperature lead wire should be used. In case of moving machinery, heaters should be firmly attached to the equipment to ensure that their leads are not damaged by excessive vibrations.
vi. Use a suitable heater
Different heating systems have different load requirements. It is therefore important to ensure that a thermal system is fitted with a heater whose wattage matches its load requirements. This helps to limit ON/OFF cycling. In addition, a suitable heater should meet the size specifications to ensure that it tightly fits in the equipment. This helps to minimize air gaps thereby enhancing the overall efficiency of the thermal system.
vii. Avoid excessive heater cycling
Excessive temperature cycling can stress resistance wires and damage a heater. It can also cause extreme oxidation of the wires thereby lowering the effectiveness of a heater. To avoid excessive heater cycling, PID controllers should be employed instead of the commonly used thermostats. Heater temperature cycling can be minimized further by coupling SCR power controllers and solid state relays to PID controllers. Although this solution is expensive, it enables heating systems to perform optimally.