1. Overview of Molten Salt Electric Heater:
The molten salt electric heater consists of a heating unit formed by special tubular electric heating elements combined with flanged bundles within a pressure vessel, utilizing nitrate salt for melting as the heating medium. Widely used in industries such as petrochemicals, dyes, resins, food, etc., it is applicable in explosion-proof areas of factory II, with an explosion-proof grade up to ExdⅡCT1-4. It is also equipped with an intelligent temperature control cabinet to meet users' requirements for heating temperature control.
2. Design of Molten Salt Electric Heater
Molten Salt Electric Heaters, also known as molten salt tanks, nitrate salt furnaces, or nitrate salt tanks, use tubular electric heating elements to heat nitrate salt, utilizing the molten nitrate salt as the heating medium.
2.1 Nitrate Tank Power Calculation
2.1.1 Calculated by molten salt volume: P = KV (KW)
Equation: V = Volume of Molten Salt (M³)
K—Power per unit volume (KW/M3)
Table 2-1: Molten Salt Unit Volume Power
Salt Melt Volume (M3) | ＜1 | 1~2 | 2~5 | ＞5 | |
Power per Unit Volume (KW/M³) | 40 | 35 | 25 | 20 |
2.1.2 Calculation based on furnace thermal efficiency: P=Q/ηK
Equation: Q – Heat required for heating the workpiece (KW)
η—heat efficiency of the硝酸盐furnace, η=0.4~0.5
κ—Voltage Reduction Influence Coefficient, κ=0.81
2.2 Installation of tubular electric heating elements
Select the model and quantity of tubular electric heating elements based on the furnace heating power. For common tubular electric heating elements, contact us at 0511-88326806 for structural forms, technical specifications, and dimensions.
When installing components, leave a distance of 60~120mm between the bottom of the component and the bottom of the slot to clear debris from the slot and serve as the expansion gap for the component. Fill the gap between the component and the mounting holes in the slot wall with asbestos rope to prevent the diffusion of nitrate salt vapor through the mounting holes to the busbar, which may cause arcing due to conduction. The level of the nitrate liquid cannot be below the effective height of the component, which is marked with a red line.
To accommodate the characteristic of high initial heating power (required to heat, melt nitrate salt, and reach operating temperature) and lower power during normal operation, the electrical heating elements should be connected in various wiring configurations for switching during the heating process.
2-2 Nitrate Salt Tank Initial Heating Schedule
Molten Salt Volume (m³) | ＜1 | 1~5 | 5~10 | ＞10 |
Initial Heating Time (h) | 8~12 | 12~24 | 24~30 | 30~40 |
2.3 Performance and Dimensions of Tubular Electrical Heating Elements
3. Molten Salt Electric Heater Control:
Primary Functions
1. Standard electrical protection is provided, including flow and short-circuit protection.
2. A standalone over-temperature alarm system independent of temperature control is equipped. When the internal temperature of the electric heater exceeds the set value, it will shut down the electric heater without automatic reset and output a contact signal.
3. A separate low-level alarm system is in place, which will automatically shut off the electric heater and send a signal when the liquid level falls below the required value.
4. Offer multiple interlock interfaces for connection with other equipment such as pumps, flow (pressure) switches, etc., to ensure that there is a certain flow rate of medium in motion during the heater's operation, guaranteeing system safety.
5. The control can provide signals to the DCS system such as heating system operation, stop, over-temperature alarm, level signal (low level alarm), interlock status, and temperature signal (4~20mA). All signals except the temperature signal are passive contacts; it can accept start and stop operation commands from the DCS, and the required contact capacity is also 220V 1A.
6. Equipped with PID temperature control function, the heating system can program the temperature rise curve of the medium and control the pump according to process requirements in case of insufficient flow or heating stoppage. This control system employs multi-level control technology, dividing the heater into several groups. The largest group can adjust pressure continuously. Based on the outlet temperature and after calculation, the control system automatically controls the on/off of each heater group and the output power of another heater group to achieve stepless power adjustment. This effectively improves the accuracy of temperature control.
For detailed information or technical support, please contact our technical support department.
Molten Salt Electric Heater
Iodized salt content (by weight) | Melting Point (°C) | Operating Temperature (°C) | Vaporization Temperature (°C) | Latent Heat of Fusion (KJ/Kg) | Average Specific Heat Capacity [KJ/(Kg.℃)] |
NaNO2100％ | 271 | 300~550 | 220 | 1.76 | |
NaNO3100％ | 317 | 325~600 | 380 | 189.66 | 1.84 |
KNO3100％ | 337 | 350~600 | 106.34 | 1.38 | |
KNO355％+NaNO345％ | 218 | 230~550 | 1.59 | ||
NaNO355％+NaNO245％ | 137 | 150~500 | 1.63 | ||
KNO350％+NaNO350％ | 230 | 300~550 | 148 | 1.00 | |
NaNO355％+NaNO245％ | 220 | 230~550 | 1.8 |
