Method for Determining and Calculating Thermal Balance and Thermal Efficiency of Ceramic Spray Drying Tower
1Key Takeaways
This standard provides guidelines for the measurement and calculation of thermal balance and thermal efficiency in ceramic spray drying towers. It outlines the procedures and methods necessary to assess the performance of such equipment under standard operating conditions. The document includes definitions, test method…
2Expert Interpretation
This article provides an in-depth interpretation of the national standard GB/T 46589—2025, "Methods for Determination and Calculation of Heat Balance and Thermal Efficiency of Ceramic Spray Drying Towers." It details the standard's scope of application, definitions of core terms, material and heat balance calculation models, key measurement items and methods, and thermal efficiency calculation formulas. Furthermore, it offers standardized implementation paths and energy-saving optimization suggestions, aiming to provide authoritative technical guidance for energy management and energy efficiency improvement in the building ceramics industry.
Core Framework and Technological Evolution of GB/T 46589—2025
The release of GB/T 46589—2025, "Methods for Determination and Calculation of Thermal Balance and Thermal Efficiency of Ceramic Spray Drying Towers," marks a crucial step forward for the standardization of energy metering and energy efficiency management in my country's building ceramics industry. This standard systematically constructs an energy audit methodology for ceramic spray drying towers, a high-energy-consuming core piece of equipment. Its technical framework originates from a scientific summary of traditional thermal testing experience and incorporates modern metrology techniques and energy efficiency evaluation concepts. The standard's technological evolution path is clear: from early, fragmented, experience-based thermal testing to today's unified, standardized measurement system based on rigorous physical models and standardized operating procedures. This not only enhances the comparability and credibility of energy efficiency data but also provides indispensable basic data support for enterprises to conduct refined management, implement energy-saving technological upgrades, and participate in carbon emission accounting.
Analysis of Core Terminology and Measurement Benchmark System
The standard clarifies the basic definitions and unified benchmarks necessary for thermal calculations in Chapters 3 and 4, which are prerequisites for ensuring accurate and comparable calculation results.
Key Terminology Definitions:
- Spray Drying Tower (Equipment): The standard references and modifies the definition in GB/T 28890—2012, clarifying that its function is to atomize slurry and dry it into powder in hot air. This definition defines the physical boundaries of the applicable scope of this standard.
- Oven-Dry Powder: Defined as powder that does not contain free radical moisture. This concept is the core benchmark throughout the entire standard's calculations. All material and heat inputs and outputs are converted to "per kilogram of oven-dry powder," eliminating calculation interference caused by fluctuations in the final moisture content of the powder, making energy efficiency evaluation more fair and scientific.
Unified Calculation Basis: The standard clearly stipulates that the temperature basis is 0°C and the mass basis is 1 kg of oven-dried powder. Using an absolute basis (0°C) instead of ambient temperature avoids sensible heat calculation errors caused by changes in ambient temperature, ensuring the inherent consistency of measurement results at different times and locations. Using oven-dried powder as the normalization basis is a core innovation in energy efficiency benchmarking in the ceramics industry, making it possible to compare the energy efficiency of drying towers with different capacities and product formulations.
Standardized Measurement Procedures and Key Item Methodologies
Chapter 6, "Measurement Items and Methods," is the core of the standard's practical operation. Its detailed provisions reflect the rigor of the standard's development. The measurement requires the system to undergo periodic measurements for at least 4 hours after continuous stable operation for at least 48 hours. This ensures that the data represents the equipment's normal operating energy efficiency, rather than transient conditions.
The standard systematically categorizes the measured objects into four main types and specifies the measurement points, frequencies, methods, and instrument accuracy requirements for each, forming a complete monitoring network. Application Case: Determination of Slurry Moisture Content The standard stipulates that the wet basis moisture content of the slurry should be sampled every 2 hours and measured after mixing. The method is as follows: Weigh the slurry mass m1, dry it in an oven at (110±5)°C for 2 hours, and then weigh it again to obtain the mass m2. Calculate the mass m2 using the formula x=[(m1-m2)/m1]×100%. Although this method is traditional, it clearly specifies the drying temperature, time, and weighing accuracy (0.001g balance), effectively controlling human error and ensuring the reliability of the original data, laying a solid foundation for subsequent complex balance calculations. For the measurement of gas flow rates (such as combustion air and flue gas), the standard specifies in Appendix C a detailed method for selecting measuring points based on the principle of equal area (such as the equal-area concentric ring method for circular pipes) and a flow velocity calculation formula based on the Pitot tube, ensuring that representative average flow rate data can still be obtained even when the flow velocity distribution across the pipe cross-section is uneven. An important quality control clause is **6.3.5**: For data requiring multiple measurements and averaging, the deviation of each data point should be less than **5%**, otherwise the test results are invalid. This provision ensures the stability of the measurement process and the validity of the data from a statistical perspective.In-depth analysis of the material and heat balance calculation model
Chapters 7 and 8 construct the core calculation model of the standard. First, material balance calculations are performed to accurately determine the amount of moisture evaporation during the drying process, which is the basis for calculating effective heat consumption. Material Balance Model: Based on the law of conservation of mass, the income item is only the mass of slurry entering the tower (m_jl), and the expenditure items are the mass of powder exiting the tower (m_fl) and the amount of water evaporated (m_h). The oven-dry powder yield m_o is calculated using the formula m_o = m_jl^0 × (1 - x_jl) = m_fl^0 × (1 - x_fl), thus normalizing all material quantities to the value under the benchmark of "per kilogram of oven-dry powder". The calculation logic is clear, providing an accurate material flow framework for heat balance. Heat Balance Model: The standard establishes a complete heat balance account through the heat balance boundary diagram in Figure 1 and the formula group in Chapter 8. This is the most essential part of the standard.
| Balance Category | Income Item (QIncome) | Expenditure Item (QExpenditure) | Key Points for Calculation |
|---|---|---|---|
| Heat Balance |
|
|
|
The heat balance table (Table 6) visualizes the heat of each item and its percentage of total revenue, which can intuitively reveal the heat distribution of the equipment and quickly locate the main heat loss links (usually the sensible heat of flue gas and surface heat dissipation).
Calculation of thermal efficiency and key energy efficiency indicators
Chapter 9 defines the core indicators for evaluating the energy efficiency of ceramic spray drying towers and their calculation methods.
1. Effective heat of drying (Qyx):This is the minimum energy required to theoretically complete the drying of powder. The calculation formula (35) considers the enthalpy change of the entire process of heating the water in the slurry from the inlet temperature to 100°C, evaporating, and then heating the water vapor to 125°C (the set final evaporation temperature). This definition is more rigorous than simply using the latent heat of vaporization and takes into account the actual process conditions.
2. Heat supplied (Qgj): Defined as the sum of fuel combustion heat (Q1) and waste heat utilization heat (Q5). This indicates that the standard encourages and recognizes the use of external waste heat, treating it as part of the total energy input. 3. Spray drying tower thermal efficiency (ηr): This is the most crucial energy efficiency indicator, calculated using formula (37): η_r = (Q_yx / ΣQ) × 100%. Where ΣQ is the total heat input. It should be noted that this efficiency is the device thermal efficiency, reflecting the proportion of the drying tower system that converts all input heat into effective drying heat. Industry-leading thermal efficiencies can exceed 50%.4. Drying heat consumption per unit product of powder (Qrh):Calculated according to formula (39), the unit is kgce/kg (kg standard coal/kg oven-dried powder). This indicator directly links energy consumption with output and is an intuitive indicator for measuring the energy intensity of production, which is convenient for enterprises to conduct cost analysis and for the state to control the energy intensity of the industry. The calculation formula is Q_rh = Q_gj / 29307, where 29307 is the lower heating value of 1kg standard coal.
5. Waste heat utilization ratio (ηy):Calculated according to formula (40), η_y = (Q5 / Q_gj) × 100%. This indicator is specifically used to evaluate the level and energy-saving effect of enterprises in utilizing external heat sources such as waste heat from kilns, and to guide enterprises to carry out system energy saving.
Standard Implementation Recommendations and Energy-Saving Technology Directions
Based on the systematic measurement and calculation methods provided by this standard, enterprises can carry out the following work to improve energy efficiency:
Implementation Path Recommendations:
- Establish a Regular Energy Efficiency Monitoring System: Referring to this standard, configure compliant measuring instruments (compliant with GB/T 24851), and conduct heat balance tests on the spray drying tower regularly (e.g., quarterly or semi-annually) to establish energy efficiency records.
- Conduct Energy Efficiency Benchmarking: Using the calculated thermal efficiency η_r and unit product heat consumption Q_rh, benchmark against different production lines within the enterprise, and against industry benchmark values or reference values in standards to identify gaps. **Focusing on Major Heat Losses:** By analyzing the heat balance sheet, identify the largest heat expenditure items (usually flue gas heat loss Q3' and surface heat dissipation Q4') as priority directions for energy-saving technological upgrades. **Energy-Saving Technology Direction Guidance:** **Reducing Flue Gas Heat Loss:** This is the area with the greatest potential for energy saving. Technical measures include: optimizing combustion control to reduce the excess air coefficient; using flue gas waste heat recovery devices (such as heat exchangers) to preheat combustion air or slurry (this will increase Q5 and improve η_y); and appropriately reducing flue gas temperature while ensuring the powder moisture content is within acceptable limits. **Reducing Surface Heat Dissipation:** Inspect and strengthen the insulation layers of the tower body, hot air ducts, and hot air furnace to ensure they are intact and effective, thereby reducing surface temperature. Optimize process operation: Increase the solid content of the slurry (reduce X_jl), directly reducing the total amount of water that needs to be evaporated, thereby reducing Q_yx and total energy consumption. Stabilize production, avoid frequent start-ups and shutdowns, and ensure that the "continuous and stable operation" required for testing becomes the norm. Improve combustion efficiency: Strengthen fuel management, clean the burner regularly, and reduce heat loss from incomplete combustion of solids and gases (Q5', Q6'). GB/T 46589—2025 is not only a set of measurement methods, but also a set of energy diagnosis and management tools. Its widespread application will promote the transformation of China's building ceramics industry from extensive energy use to refined, data-driven green manufacturing, and play an important supporting role in achieving the "dual carbon" target.