The Basics of Thermic Fluid Heaters: Everything You Need to Know
Introduction – Thermic Fluid System
Hi, all my TFH readers. Today, we will discuss all the basics related to thermic fluid heaters. In this article, we covered the following: What is a Thermic Fluid heater? What is the working principle of a thermic fluid heater? What are the key components of a thermic fluid heater? What are the advantages and applications of a thermic fluid heater? Thermic fluid heaters, also known as thermal oil heaters, are essential components of many industrial processes. They generate heat by circulating a thermic fluid (thermal oil) without high pressure. Unlike traditional steam boilers, which use water as the heat transfer medium, thermic fluid heaters use specialized fluids that can operate at higher temperatures without the associated high pressures.
The significance of thermic fluid heaters in industrial processes cannot be overstated. They offer several advantages, including precise temperature control, efficient heat transfer, and low maintenance requirements. These attributes make them ideal for industries where consistent and reliable heat is crucial, such as the chemical, textile, and food processing.
The working principle of thermodynamic fluid heaters is relatively straightforward. The heated fluid transfers heat to the desired process or application, ensuring efficient and controlled thermal energy distribution.
Components of Thermic Fluid Heaters
Heat Exchanger
The heat exchanger is a critical component of a thermic fluid heater. It transfers the heat generated in the heater coil to the thermodynamic fluid. Heat exchangers are designed to maximize heat transfer, ensuring that the thermodynamic fluid is heated efficiently and uniformly. The design and construction of the heat exchanger can vary depending on the specific application and the type of fuel used.
Heater Coil
The heater coil is the component where the fuel is burned. It is typically made of high-quality steel or alloy to withstand the high temperatures generated during combustion. The heater coil is designed to provide a large surface area for heat transfer, ensuring that the thermodynamic fluid is heated quickly and efficiently. The coil’s design also allows for uniform heat distribution, preventing hotspots and ensuring consistent performance.
Thermic Fluid Pump
The thermic fluid pump circulates the thermic fluid through the heat exchanger and the heater coil. The fluid circulation system consists of a primary pump coupled to an electric motor, an emergency diesel engine drive, and a clutch and V Belts. This pump must be robust and reliable, as continuous circulation of the thermic fluid is crucial for maintaining consistent heat transfer and preventing overheating. The pump’s capacity and design are determined based on the specific requirements of the thermic fluid heater system.
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Screw Feeder
Screw feeder is provided for the feeding of imported coal/petcoke. Screw feeder speed can be modulated, which is governed by thermic fluid outlet temperature of the heater. Varying the speed of the screw feeder regulates the fuel feed to the combustor. This reduces the ON/OFF working of the heater due to load fluctuations & imported is burnt inside the Thermic Fluid Heater furnace with refractory lined combustor.
Combined Deaerator Cum Expansion Tank
Deaerator cum expansion tank is provided in the retrunline. The Thermic fluid in the complete circuit expands in volume when heated. The volume expansion rate is 7% per 100°C rise in the temperature of the thermic fluid. Hence, the selection of the size of the expansion tank depends upon the fluid content of the total system. As a guideline, the expansion tank capacity should be at least 20% of the total volume of oil to be filled up in the system. The deaeration vessel capacity depends upon the flow rate. Its size can be roughly decided considering 2.5 to 3 m/s fluid velocity at its inlet nozzle.
The standard de-aerator cum expansion tanks supplied is suitable for most of the standard processes. If the volumetric expansion of the thermic fluid of the system is more than the capacity of the expansion tank, a separate extra expansion tank needs to be incorporated.
The thermic fluid also contains higher fractions that flash off at elevated temperatures while commissioning. These must be driven out of the system to ensure proper equipment functioning. The combined expansion and deaerator tank is designed to take care of the expansion of the thermic fluid and drive away the gases or trapped air. This tank should be installed at least 1 meter ( 3 feet ) above the highest point in the thermic fluid pipelines. It is also necessary to confirm that the NPSH available at the pump suction is more than required for your pump by at least 0.5 m. Supports are welded to the tank, with the help of which the tank can be fixed and bolted to the structure.
Drain /Over Flow /Make-Up Tank
The tank kept on the ground to which drain and overflow from the combined expansion and deaerator tank are connected has to be of a capacity at least equal to the capacity of the combined expansion and deaerator tank. The overflow pipe should be taken to the bottom of this tank and should be provided with a sparger arrangement to avoid hot oil coming in contact with air to prevent it from degrading. While installing the thermic fluid circulating pump arrangement, a small pump of 1000 liters/hr should be installed. at about 30-40 MLC of pumping head. The pump is connected to the suction side of the TF circulating pump to charge the system with thermic fluid when required. It is necessary to have such an arrangement because it is not advisable to use the thermic fluid circulating pump to charge thermic fluid in the system. This will also help fill the system from the bottom, driving out all the entrapped air.
Diesel Engine Drive In Case Of Power Failure
A Diesel engine is provided as an emergency drive parallel to the motor to keep the thermic fluid in circulation when electric power fails. When the power fails, circulation in the thermic fluid circuit will stop. However, there is always some amount of fuel in the furnace, which keeps burning. Also, hot flu gases are present in the heat exchangers. The fluid in the heat exchanger is at a standstill and starts picking up heat from the flue gases. This increases the oil temperature in the coils. Each thermic fluid has a safe operation limit called the film temperature, which should not be crossed, or else the thermic fluid will degrade.
To avoid this, a separate diesel engine-driven pump is provided in parallel to the electrically driven pump. The engine is to be started manually immediately on failure of the TF circulating pump. First, before starting the engine, the pulleys need to be engaged by the belt provided. Power is transmitted through V-belts to the main pump. The pump runs at a lower speed ( 1000 to 1100 rpm ) and delivers approximately 1/3rd of the rated flow through the heater. Thus, the fluid flows at 1/3rd of the rated velocity, which is sufficient to take away the radiant heat liberated by the hot bed and refractory and to avoid a rise in film temperature, thereby avoiding degradation of thermic fluid.
Note: As it is critical to take care of power failure conditions, the health of the generator is always to be ensured by starting the diesel engine daily and adhering to the maintenance schedule recommended by the supplier.
Combustion Air System
One forced draft fan supplies the air required for the combustion of the fuel. The air required for the combustion can be divided into primary and secondary. Primary air contributes to the combustion of the fixed carbon in the fuel. Secondary air contributes to the combustion of the volatile matter of the fuel. Primary and secondary air from the FD fan gets heated in APH.
The primary air duct from APH connected to the furnace below the bed. This air supplies the oxygen required for the combustion. The suction damper is provided at the FD fan to regulate the air quantity as required. Secondary air duct is further connected to nozzles of furnace structure above the l bed. There is a control damper provided in the primary as well as the secondary ducting, which controls the air pressure head. Depending upon volatile matters in fuel, we have to control secondary air quantity.
Flue Gas System
Flue gas is a product of the combustion of the fuel. The flue gas typically consists of CO2, N2, and O2 as major constituents with temperatures in the order of 850- 950 ºC. The flue gases give their heat to the therrnic fiuid circuit, which isl utilized in the process. Flue gases gererated in the combustion cnamber irst i transfer their heat to the radiant coil. Then the gases are passed through the threei pass heat exchanger. The flue gases further pass on to the second stage heat recovery in APH, and gases are cooled down to around 220-230℃。 The gases then pass through the pollution control equipment ( TMC / TREMA ). The solid particles in the flue gases are separated in it, and clean gases go to the Chimney through the ID fan.I Gases get exhausted in the atmosphere through the chimney.
Ash Handling System
The Ash is another product of combustion and consists mainly of the non-combustible residue and mneral matters . The ash is collected at various points along the flue gas path. The majority of the ash is collected at the control equipment ( TMC/TREMA ), the APH and below the ash-selling chamber. This ash at APH and the ash settling chamber are at a high temperature at around 500-600 °C. So Hopper/Chamber at these points should have refractor lining(i.e insulate and frecrete layers ) .
The ash at TMC & APH is discharged through sliding gate arrangements in a closed chamber constructed below it. To remove the ash, 1) close the sliding gate, 2) open the ash door provided to the closed chamber, 3) remove the ash, 4) close the door, and 5) reopen the sliding gate.
The ash at TREMA is discharged through rotary airlock valves (RAV ), collected in suitable barrels or gunny bags, and dumped from time to time.
Electrical Control Panel
The electrical control panel box is supplied separately from the Thermic Fluid Heater and must be erected to the Thermopac. The location and foundation details of the panel box are given in the “General Assembly ” drawing.
Three phase 415V, 50 cycles A.C electrical supply with neutral and earth is required for operating the thermic fluid heater. The supply to the thermic fluid heater should be given through a main switch fuse having adequate capacity, as mentioned in the following table. The backup fuse capacity to suit the total electric loading should also be maintained. The main switch fuse capacity should be a little more for safety. No extra starter or switch is required for the thermic fluid heater circulation pump motor, blower motor, etc. The panel board is pre-wired.
Switches for other pumps, such as TF, a make-up pump for pumping TF from the storage tank to the deaerator tank, etc., should be separately installed by the customer at points convenient for operation.
Working Principle of Thermic Fluid Heaters
Thermic fluid heaters operate on a simple yet effective principle. Heat is generated in the heater coil using a fuel source, such as natural gas, oil, or biomass. The fuel is combusted in the heater coil, producing high temperatures. The heat generated in the heater coil is then transferred to the thermic fluid as it circulates through the heat exchanger.
Thermic fluid system is a forced circulation single phase heating system. The thermic fluid circulated in the heat exchanger coils absorbs the heat. The heat exchanger consists of radiant and convective coils. The hot flue gases formed in the combustion chamber heat the flid. The heat exchanger is single-pass on the oil side and four-pass on the gas side. Hot flue from the combustor enters the radiant coil. Then, it flows through the three passes of the convective heat exchanger assembly. Heat is transferred to the oil during these passes.
The Hot fluid from the heat exchanger outlet is taken to the utility through the thermic fluid pipelines. The fluid transfers the heat to the process and returns to the heater. The orifice plate is fitted across the heat exchanger. The pressure drop across the rifice plate indicates the flow through the col. Low flow across the coil is an indication of the coil choking. The heater is tripped. The alarm and the low oil flow signal are generated on the panel. This avoids the overheating of the coil tube material due to less flow.
As the thermic fluid passes through the heat exchanger, it absorbs the heat from the heater coil, raising its temperature. The heated thermic fluid is circulated through a closed-loop system, transferring the heat to the desired process or application. This ensures efficient and controlled heat distribution, allowing for precise temperature control and consistent performance.
Applications of Thermic Fluid Heaters
Chemical Industry
In the chemical industry, precise temperature control is essential for various processes, such as distillation and polymerisation reactions. Polymerization heaters provide consistent and reliable heat, ensuring these processes are carried out efficiently and safely. Their ability to operate at high temperatures without high pressure makes them an ideal choice for chemical plants.
Textile Industry
The textile industry relies on consistent and controlled heat for the dyeing, drying, and finishing processes. Thermic fluid heaters offer precise temperature control, ensuring these processes are carried out efficiently and consistently. Their low maintenance requirements and reliable performance make them popular in textile manufacturing.
Food Processing Industry
Maintaining consistent and controlled heat in food processing is crucial for pasteurisation and drying. Pasteurization on heaters provides the necessary heat while ensuring precise temperature control, which is essential for product quality and safety. Their ability to operate at high temperatures without high pressure makes them a preferred choice in food processing plants.
Rubber and Plastics Industries
In the rubber and plastics industries, thermic fluid heaters are used for molding, extrusion, and vulcanization processes. They provide consistent and controlled heating to molds and dies, ensuring uniform curing and shaping of products. These heaters are also employed in calendering and laminating processes, where precise temperature control is essential for achieving the desired material properties. Thermic fluid heaters operate efficiently at high temperatures, making them ideal for these applications. By improving energy efficiency and reducing downtime, they contribute to cost savings and enhanced product quality in rubber and plastic manufacturing.
Publishing and Print Industries
Thermic fluid heaters are crucial in the publishing and print industries for maintaining optimal temperatures during printing and drying processes. They are used in heating rollers and drying systems to ensure fast and even drying of inks, preventing smudging and improving print quality. These heaters also provide consistent heat for laminating and binding processes, enhancing the durability and finish of printed materials. Their ability to operate at high temperatures without degradation ensures reliable performance in demanding printing environments. By improving energy efficiency and reducing downtime, thermic fluid heaters help streamline production and maintain high standards in the publishing and print industries.
Metal Fabrication and Finishing Plants
Thermic fluid heaters are widely used in metal fabrication and finishing plants for heat treatment processes such as annealing, tempering, and hardening. They provide precise temperature control, ensuring uniform heating and cooling of metal components to achieve the desired mechanical properties. These heaters are also employed in coating and drying systems, where consistent heat is required for curing paints and finishes. Their high thermal stability and efficiency make them ideal for these applications, reducing energy consumption and operational costs. Additionally, thermic fluid heaters help extend the lifespan of equipment by minimizing thermal stress, contributing to improved productivity and product quality in metal fabrication.
Paper Industries
In the paper industry, thermic fluid heaters are used for drying and curing processes during paper production. They provide consistent and efficient heat for drying paper sheets, ensuring uniform moisture content and preventing warping or curling. These heaters are also employed in coating and laminating processes, where precise temperature control is essential for achieving desired surface finishes. Their thermal stability and efficiency help reduce energy consumption and operational costs. Additionally, thermic fluid heaters contribute to improved production speeds and product quality, making them indispensable in modern paper manufacturing processes.
Crude Oil Extraction and Processing Industries
In crude oil extraction and processing, thermic fluid heaters are used for heating and temperature control in processes such as distillation, cracking, and desalting. They provide efficient heat transfer, ensuring optimal operating conditions for equipment like heat exchangers and reactors. These heaters help maintain consistent temperatures, improving process efficiency and product yield. Their thermal stability and ability to operate at high temperatures make them ideal for these applications. By reducing energy consumption and operational costs, thermic fluid heaters contribute to improved productivity and profitability in the crude oil industry.
Advantages of Using Thermic Fluid Heaters
Efficient Heat Transfer
Thermic fluid heaters are designed to provide efficient heat transfer, ensuring the thermic fluid is heated quickly and uniformly. Using specialized fluids allows them to be used at higher temperatures without high pressure, resulting in efficient and controlled heat distribution.
Precise Temperature Control
One key advantage of thermic fluid heaters is their ability to provide precise temperature control. The closed-loop system and thermic fluids allow for consistent and accurate temperature regulation, ensuring that industrial processes are carried out efficiently and with consistent quality.
Low Maintenance Requirements
Thermic fluid heaters have relatively low maintenance requirements compared to traditional steam boilers. Using thermic fluids eliminates the need for water treatment and the associated corrosion and scaling issues. Additionally, the robust design and construction of thermic fluid heaters ensure reliable performance and long service life, reducing the need for frequent maintenance and repairs.
Deaerator/Expansion Tank Integral Arrangement
The integrated deaerator and expansion tank arrangement ensures the removal of air and moisture from the thermic fluid, enhancing system efficiency and preventing corrosion.
High Flow Rate Ensures Longer Life of Thermic Fluid and Heater Coil
The high flow rate of the thermic fluid minimizes thermal degradation, extending the life of both the fluid and the heater coil.
Operates on a Variety of Fuels
The heater is compatible with multiple fuel types, including diesel, natural gas, biomass, and more, depending on local availability and cost-effectiveness.
Fully Automatic Unit
The system is fully automated, ensuring precise control over the desired temperature of the thermic fluid. This automation eliminates manual intervention, reduces human error, and ensures consistent performance.
Conclusion
In conclusion, thermic fluid heaters play a crucial role in various industrial processes by providing efficient and controlled heat. Their working principle involves generating heat in a heater coil using a fuel source, transferring it to a thermic fluid through a heat exchanger, and circulating the heated liquid to the desired process or application.
The importance of thermic fluid heaters in industries such as chemical manufacturing, textile production, and food processing cannot be overstated. They offer several advantages, including efficient heat transfer, precise temperature control, and low maintenance requirements, making them an ideal choice for applications where consistent and reliable heat is essential.
Adopting thermic fluid heaters will likely increase as industries seek ways to improve efficiency and reduce operational costs. By understanding these heaters’ working principles, components, and applications, industries can make informed decisions and optimize them for better performance and sustainability.
For further exploration of thermic fluid heaters and their applications in various industries, consider consulting industry publications, regulatory guidelines, and best practices from leading companies in the field. Prioritizing hermetic fluid and utilities can enhance operational efficiency and create a more sustainable future.