As a vital component of the basic chemical and food processing sectors, the salt production industry relies heavily on a stable and efficient supply of heat energy. From the extraction and refining of raw salt to the drying and packaging of finished salt, each critical link requires continuous heat input to ensure smooth process flow and consistent product quality. As the core support equipment of the thermal energy system, industrial boilers play an indispensable role in this process. They are not only the primary source of heat energy for salt production plants but also a key component in determining production efficiency, product costs, and environmental performance. Whether using traditional evaporation salt production or modern vacuum salt production technology, the performance and operating status of industrial boilers directly impact the overall stability and economic efficiency of the salt production line. Therefore, a deep understanding of the uses and application mechanisms of industrial boilers in salt production plants is crucial to promoting the efficient development of the salt production industry.
In the production line layout of a salt production plant, the placement of industrial boilers must fully integrate the needs of the production process to ensure efficient transmission and utilization of heat energy. Typically, boilers are located near major heat-consuming units. This layout minimizes the length of steam transmission piping, reduces heat loss during steam transmission, and reduces pipe resistance, ensuring a stable steam supply. In large salt production plants, to meet the heat demands of multiple production lines or large-scale production, boilers are often clustered, forming independent boiler rooms. This area is also equipped with fuel storage areas, water treatment systems, and flue gas treatment facilities, forming a complete heat supply center.
The relationship between boilers and the evaporation and crystallization units demonstrates a strict capacity matching logic. The evaporation unit consumes the most heat energy in the salt production process. Its primary function is to evaporate the water in the brine through heating, increasing its concentration. The crystallization unit, on the other hand, requires specific temperature and pressure conditions to precipitate salt crystals from the highly concentrated brine. Therefore, the boiler's steam output must be precisely designed based on the evaporation capacity and the processing capacity of the crystallization unit to ensure that each heat-consuming unit receives sufficient and stable steam. To cope with load fluctuations during production, boiler systems typically include backup units or flexible load adjustment capabilities. When the heat demand of the evaporation and crystallization units fluctuates, the boiler can quickly adjust steam output to prevent production from being disrupted by insufficient or excessive heat supply.
During the salt production process, industrial boilers convert chemical energy into thermal energy through fuel combustion, heating the water within the boiler to its boiling point and producing saturated or superheated steam. This steam is transported to each heat-consuming unit via dedicated pipelines. During transportation, the pipelines are insulated to minimize temperature drops and condensate formation. Once the steam reaches equipment such as the evaporator or crystallizer, it indirectly exchanges heat with the brine through heat exchange tubes. The steam releases latent heat and condenses into water. This condensate is collected through a steam trap, with some of it being recycled back into the boiler as feedwater, achieving secondary heat recovery.
Steam pressure and temperature are key parameters affecting salt quality, and different salt production processes have varying steam parameter requirements. During the evaporation stage, if the steam pressure is too low or the temperature is insufficient, the brine's evaporation rate will slow, extending the production cycle and potentially causing the brine to remain in the evaporator for an extended period, leading to localized over-concentration and affecting the stability of the subsequent crystallization process. If the steam pressure or temperature is too high, the brine may boil violently, generating large amounts of foam. This foam can carry brine into subsequent equipment, causing salt loss and accelerating scaling on the evaporator's inner walls, reducing heat exchange efficiency. During the crystallization stage, the stability of steam parameters is even more crucial. The crystallization process requires relatively constant temperature and pressure. Excessive steam temperature fluctuations can lead to uneven growth of salt crystals, resulting in crystals of varying sizes and shapes, affecting the appearance and particle size uniformity of the finished salt. Furthermore, steam pressure fluctuations can disrupt the vacuum level of the crystallization system (in vacuum salt production processes), further compromising the crystallization process and even reducing product purity.
Common industrial boiler types in salt production plants include coal-fired boilers, gas-fired boilers, biomass boilers, and waste heat boilers. These types of boilers vary significantly in efficiency, operating costs, and environmental performance.
Coal-fired boilers are the most widely used type of boiler in traditional salt production plants. Their main advantages are relatively low fuel prices and widespread fuel supply, enabling them to meet large-scale, long-term heating needs. However, coal-fired boilers have relatively low thermal efficiency, typically between 70% and 85%. Furthermore, the combustion process produces large amounts of pollutants such as sulfur dioxide, nitrogen oxides, and dust, requiring complex and costly flue gas treatment facilities to meet environmental requirements, which increases operating costs.
Gas-fired boilers, powered by clean fuels such as natural gas and liquefied petroleum gas, have high thermal efficiency, typically reaching 90% to 98%. Pollutant emissions during combustion are far lower than those of coal-fired boilers, particularly nitrogen oxides, resulting in superior environmental performance. Furthermore, gas-fired boilers offer fast start-up and shutdown times, high load adjustment flexibility, and the ability to quickly respond to fluctuating heat demands of the salt production line. They also occupy a relatively small footprint and require minimal maintenance. However, the operating costs of gas-fired boilers are significantly affected by fuel prices. When natural gas and other fuel prices are high, their operating costs can be significantly higher than those of coal-fired boilers. Furthermore, they require a more stable fuel supply, requiring reliable gas pipelines or storage facilities.
Biomass boilers, fueled by renewable biomass such as crop straw, wood chips, and biomass pellets, align with sustainable development principles, offer relatively low fuel costs, and emit near-zero carbon dioxide during combustion, resulting in better environmental performance. However, biomass fuel has a low bulk density, making storage more difficult and requiring a larger storage space. Furthermore, the fuel's relatively low calorific value and significant compositional fluctuations can lead to unstable boiler combustion and affect the stability of steam parameters. Furthermore, biomass boilers are prone to slagging, requiring regular slagging removal and a relatively high maintenance frequency. Waste heat boilers (HRSGs) are energy-efficient boilers that utilize waste heat from industrial production processes to generate steam. They require no additional fuel, and their thermal efficiency depends primarily on the quality and utilization of the waste heat. They can typically recover 30%-50% of this waste heat, significantly reducing the salt plant's overall energy consumption. However, their operation relies on a stable supply of waste heat. Large load fluctuations in the salt production line, coupled with unstable waste heat resources and parameters, can directly impact the steam production and stability of the HRSG. Therefore, HRSGs are often used in conjunction with other boiler types to ensure a stable heat supply for the salt plant.
In vacuum salt production systems, industrial boilers are the primary heat source. The steam they generate directly determines the efficiency and product yield of the vacuum salt production process. The core principle of vacuum salt production is to lower the boiling point of brine under vacuum conditions, allowing it to evaporate at lower temperatures, thereby reducing heat energy consumption and preventing impurities in the brine from decomposing or deteriorating due to high temperatures. In this process, boiler steam first enters the heating chamber, where it transfers heat to the brine through heat exchange tubes, causing it to rapidly evaporate under vacuum. The resulting secondary steam is then introduced into the next-effect heating chamber for further use. After releasing heat, the boiler steam condenses into water and enters the condensate recovery system.
Steam distribution and temperature control are crucial in this process. Steam distribution must be precisely controlled based on the heat demand of each heating chamber in a multi-effect evaporation system to ensure that each effect receives the appropriate amount of steam. This prevents insufficient steam supply in one effect, which could lead to reduced evaporation efficiency, or excessive steam supply, which could lead to wasted heat energy. At the same time, temperature control must be closely coordinated with the vacuum system. Different heating chambers with different numbers of effects require different steam temperatures to accommodate the evaporation requirements of brine at varying concentrations. For example, in the first-effect heating chamber of a multi-effect evaporator, the brine concentration is low, requiring higher steam temperatures to increase the evaporation rate. In contrast, in the final-effect heating chamber, the brine concentration is higher, leading to a higher boiling point. Therefore, the steam temperature must be appropriately adjusted to prevent brine overheating and scaling. Improper steam temperature control not only affects evaporation efficiency but can also cause brine scaling on the heating tubes, reducing the heat transfer coefficient and further increasing heat energy waste. It may even require downtime for cleaning, impacting production continuity.
In addition to providing heat energy for the evaporation and crystallization units, steam generated by industrial boilers also plays a vital role in supporting the stability of the salt production process and equipment operation. Many key equipment in the salt production line rely on steam power, most notably the vacuum pump in the vacuum system. The vacuum salt production process requires maintaining a stable vacuum environment. The vacuum pump generates negative pressure through steam jets, extracting non-condensable gases and some secondary steam from the evaporation chamber to ensure a stable vacuum. Steam pressure and flow directly affect the vacuum pump's extraction capacity. Insufficient steam pressure reduces the vacuum pump's negative pressure, leading to reduced vacuum in the evaporation chamber, an increase in the boiling point of the brine, and decreased evaporation efficiency. Unstable steam flow can cause vacuum fluctuations, impacting the stability of the crystallization process. Furthermore, some salt production plants use steam as a power source for material conveying and mixing equipment to ensure smooth material transfer and mixing during production.
At the same time, controlling boiler steam pressure and temperature is crucial for ensuring the consistency of salt products. The salt production process imposes strict requirements on salt purity, particle size, moisture content, and other indicators, and the control of these parameters is closely related to the temperature and pressure during the production process. During the salt crystal growth stage, excessively high steam temperature can lead to a sharp increase in brine supersaturation, resulting in the precipitation of a large number of fine salt crystals, affecting the particle size of the finished salt. Excessively low steam temperature can slow salt crystal growth and easily lead to crystal agglomeration. By precisely controlling the pressure and temperature of boiler steam, a stable thermal environment is provided for the crystallization process, ensuring consistent growth conditions for salt crystals in each batch. This ensures consistent performance across all finished salt products, avoiding product quality variations caused by fluctuations in process parameters and meeting stringent market requirements for salt quality.
In the salt production process, industrial boilers not only generate heat but also, when combined with waste heat recovery systems, become a crucial component in energy efficiency optimization. The use of condensate recovery systems is a key means of achieving secondary thermal energy utilization. After exchanging heat with brine, boiler steam condenses into high-temperature condensate. This condensate contains a significant amount of sensible heat, and direct discharge would result in significant heat energy waste. The condensate recovery system, using equipment such as steam traps and recovery pumps, collects this condensate, filters it, deoxidizes it, and returns it to the boiler as feed water. This system not only reduces fresh water usage and water treatment costs, but also utilizes the sensible heat in the condensate, reducing the fuel consumption required for water heating in the boiler and significantly improving the overall thermal efficiency of the boiler system. According to statistics, a reasonable condensate recovery system can reduce boiler fuel consumption by 10%-20% while also reducing wastewater discharge, meeting the dual requirements of energy conservation and environmental protection.
In addition, integrating industrial boilers with waste heat boilers is an effective way to further improve energy efficiency in salt production plants. The salt production process generates a large amount of waste heat, such as secondary steam from the evaporation unit, waste heat from boiler flue gas, and high-temperature exhaust gases from the salt drying process. Waste heat boilers can recycle this previously wasted heat to heat water and generate low-pressure steam. This low-pressure steam can be used to dry salt products, preheat brine, or serve as an auxiliary heat source to feed the evaporation system, thereby reducing steam production requirements and fuel consumption in the main boiler. In multi-effect evaporation salt production, the secondary steam generated by the final evaporation process has a low pressure and cannot be directly used in the next evaporation process. However, this heat can be recovered in a waste heat boiler. The resulting low-pressure steam is used to preheat the brine entering the first evaporation process, raising the initial brine temperature and reducing the steam consumption of the main boiler in the first-effect heating chamber. This integrated approach not only achieves cascaded utilization of waste heat resources but also reduces the salt plant's overall energy consumption and carbon emissions, driving salt production towards higher efficiency and energy conservation.
Salt production is characterized by high continuity. Any interruption to the production line results in significant economic losses. The operational reliability of industrial boilers directly determines the ability of the salt production line to operate continuously. Therefore, developing a scientific and rational boiler maintenance strategy is key to ensuring continuous production in the salt plant. Boiler maintenance management primarily includes daily inspections, periodic overhauls, and preventive maintenance. During routine inspections, personnel must monitor boiler parameters such as pressure, temperature, water level, fuel supply, and flue gas emissions in real time to promptly identify and address operational anomalies such as valve leaks, instrument failures, and unstable combustion. Regular maintenance requires inspection, cleaning, and replacement of key components such as the boiler's heating surfaces, burners, water treatment systems, and safety accessories, in accordance with the equipment maintenance manual. For example, scaling and dust accumulation on the boiler's heating surfaces should be regularly cleaned to ensure efficient heat exchange. Safety valves and pressure gauges should also be regularly calibrated to ensure their sensitivity and reliability, thereby preventing potential safety incidents.
At the same time, the application of performance and safety monitoring systems provides technical support for stable boiler operation. Modern salt production plants' industrial boilers are generally equipped with automated monitoring systems. These systems utilize sensors installed at key locations within the boiler to collect real-time data on steam pressure, temperature, water level, fuel flow, flue gas composition, and other parameters, transmitting this data to a central control system. The central control system analyzes and processes the data. If any parameters exceed the set range, it promptly issues an alarm and automatically implements appropriate adjustments to restore normal boiler operation. For some critical safety parameters, the system also features an emergency shutdown function, which can quickly cut off the fuel supply in the event of a dangerous situation, ensuring the safety of the boiler equipment and operators. Furthermore, through the long-term accumulation and analysis of monitoring data, it is possible to identify performance trends of boilers, predict potential equipment failures, and formulate maintenance plans in advance for preventive maintenance. This further improves boiler operational reliability, reduces unplanned downtime, and ensures the continuous and stable operation of the salt production line.
With the modernization of the salt production industry, the integration of industrial boilers with modern automation systems has become a key trend for improving production efficiency and ensuring stable operation. Real-time monitoring and control technology is the core of this integration. By combining boiler operating parameter monitoring with automated control systems, precise control of boiler operating conditions is achieved. In this integrated system, sensors distributed throughout the boiler continuously collect key data such as steam pressure, steam temperature, boiler water level, fuel flow, feedwater flow, flue gas temperature, and flue gas composition, and transmit this data in real time to a central control system. The central control system processes and analyzes this data in real time using a dedicated software platform. Operators can intuitively view various boiler operating parameters on the monitoring interface, gaining a clear understanding of the boiler's operating status and promptly identifying parameter anomalies, thereby avoiding operational risks caused by untimely manual monitoring. In addition to real-time monitoring, the automated control system also features intelligent regulation, automatically adjusting boiler operating parameters based on changes in the salt production line's heat demand to achieve energy-efficient operation. When the evaporation or crystallization unit of the salt production line reduces heat demand due to production schedule adjustments, the automated control system analyzes changes in parameters such as steam pressure and steam flow to automatically reduce the boiler's fuel and feedwater flow, reducing steam production and avoiding heat waste caused by excess steam. Conversely, when the production line's heat demand increases, the system automatically increases fuel and feedwater supply to increase steam production and ensure timely and sufficient heat supply. Furthermore, the automated control system optimizes boiler operating parameters. For example, by precisely controlling the fuel-to-air ratio, the fuel is fully burned in the boiler, improving fuel utilization and reducing energy losses caused by incomplete combustion. By adjusting the boiler's blowdown rate, the boiler's scale buildup is reduced, ensuring efficient heat transfer on the heating surfaces and further reducing energy consumption. This intelligent regulation not only reduces operator workload but also ensures the boiler is always operating in optimal condition, ensuring heat supply to the salt production line while maximizing energy efficiency.
In the salt production process, optimizing the performance of industrial boilers is a key measure to improve energy efficiency and reduce production costs. Improving thermal efficiency and reducing fuel consumption are the core goals of boiler performance optimization, and various technical measures can be employed to achieve this. First, optimizing the boiler's combustion system is a key approach to improving thermal efficiency. Improving the burner's structural design allows for more complete mixing of fuel and air, reducing incomplete combustion. Furthermore, implementing advanced combustion control technologies allows for real-time adjustment of the fuel-air ratio to maintain optimal combustion, improving fuel efficiency. Second, strengthening the cleaning and maintenance of the boiler's heating surfaces and regularly removing scale and dust deposits can effectively improve the heat transfer coefficient and reduce heat loss within the boiler. Furthermore, using high-efficiency insulation materials to insulate the boiler body and steam piping to reduce heat loss is also an effective means of improving boiler thermal efficiency. For example, replacing traditional insulation with new composite insulation materials can reduce heat loss from the boiler surface by over 30%, significantly improving thermal energy utilization. The application of steam management and system balancing methods is also an important component of boiler performance optimization. Steam management primarily involves the rational allocation of steam, condensate recovery and utilization, and stable steam pressure control. Regarding steam distribution, a scientific steam allocation plan is developed based on the priorities and heat demands of each heat-consuming unit in the salt production line to prevent excessive steam from being taken up by non-critical heat-consuming units and to ensure steam supply to critical units. Furthermore, by installing steam flow metering devices, steam consumption by each unit is monitored in real time to promptly identify steam waste and implement corrective measures. Regarding condensate recovery and utilization, in addition to establishing a comprehensive condensate recovery system, the value of condensate can be further enhanced by increasing its recovery temperature and reducing contamination during the recovery process. For example, condensate can be used to preheat boiler feed water or heat brine, achieving cascaded thermal energy utilization. Steam system balancing requires a dynamic balance between boiler steam output and the steam demands of each heat-consuming unit to avoid energy waste or production interruptions caused by an imbalance in steam supply and demand. For example, by establishing a steam network pressure stabilization system, steam pressure changes within the network can be monitored in real time. When pressure is excessive, steam can be dissipated through pressure relief valves or directed to backup heat units. When pressure is too low, boiler loads can be adjusted promptly or backup boilers activated to replenish steam supply, ensuring the entire steam system maintains stable and efficient operation. Furthermore, thermal calculations and simulations of the steam system can be used to optimize the diameter and layout of steam pipelines, reduce pipeline resistance losses, further improve steam transmission efficiency, and achieve overall steam system balance and energy conservation.
As the salt production industry moves towards sustainable development and energy transition, technological upgrades of industrial boilers and adjustments to the energy structure are key initiatives. The use of clean fuels, the construction of hybrid boiler systems, and the integration of renewable energy sources not only help salt plants reduce pollutant emissions and carbon intensity, but also enhance the flexibility and stability of energy supply, laying the foundation for green, low-carbon, and efficient production in the salt production industry.
In short, industrial boilers are core supporting equipment for efficient production and sustainable development in salt plants. Their technological level and operational management capabilities are directly related to the competitiveness and long-term development of the salt production industry. In the future, with the continuous advancement of energy technology and the continuous improvement of environmental protection requirements, salt plants need to further strengthen the technological innovation and application exploration of industrial boilers, promote the development of boiler systems in a more efficient, cleaner and smarter direction, and contribute to the sustainable transformation of the global salt industry.
