I. Technical Definition and Classification Standards

High-temperature hot water boilers are thermal energy devices that use fuel combustion or electricity to heat water to temperatures above 130℃. Their core parameters include supply water temperature, operating pressure, and thermal efficiency. According to the American Society of Mechanical Engineers (ASME) standard, a high-temperature hot water boiler (HTHW) typically refers to equipment with a supply water temperature exceeding 121℃ and an operating pressure exceeding 1.1MPa. In practical applications, common parameters are a supply water temperature of 130-180℃ and a pressure ≤2.5MPa. Chinese standards use 130℃ as the dividing line between high and low temperature boilers. For example, the 29MW chain grate boiler used in the Zuojiazhuang area boiler room in Beijing has a supply water temperature of 150℃.

In terms of technical classification, high-temperature hot water boilers are classified by fuel type into coal-fired, gas-fired, oil-fired, and electric boilers; by circulation method into natural circulation, forced circulation, and once-through type; and by structure into shell-type (fire-tube) and water-tube type. Modern mainstream technologies include high-pressure electrode boilers (heated via water resistance) and circulating fluidized bed boilers (utilizing fluidized bed combustion technology). The latter can achieve a thermal efficiency of over 92% and nitrogen oxide emissions below 30 mg/m³.

II. Core Systems and Operating Principles High-temperature hot water boilers consist of three main systems working in tandem:

Water-Steam System: Water circulates in pressurized components such as the boiler drum, water-cooled walls, and convection tube bundles. It absorbs waste heat from the flue gas through an economizer and then enters the heating network after heating. For example, the heating system at Hongqiao International Airport uses eight plate heat exchangers, with variable frequency circulating water pumps regulating the flow rate to achieve stable operation at a supply water temperature of 130℃ and a return water temperature of 70℃.

Coal-Ash System: Coal-fired boilers use chain grate or circulating fluidized bed technology. Fuel burns in the furnace to generate high-temperature flue gas, which is then heated by an air preheater before entering the flue. Gas-fired boilers use water-cooled premixed combustion technology, achieving a thermal efficiency exceeding 99% and nitrogen oxide emissions below 20 mg/m³.

Flue Gas System: Flue gas passes through the furnace, convection tube bundle, and economizer before entering the dust collector and finally exiting through the chimney. Modern boilers are equipped with waste heat recovery devices, which can reduce the exhaust gas temperature from 200℃ to below 80℃, reducing heat loss by 15%.

III. Application Scenarios and Engineering Cases

Regional Central Heating: High-temperature hot water boilers are core equipment in urban combined heat and power (CHP) systems. For example, the Changqing District 2×70MW hot water boiler project uses forced circulation water tube boilers. Through system optimization and standardized construction, each boiler can heat an area of ​​over 2 million square meters, achieving 25% energy savings compared to steam boilers.

Industrial Process Heating: In food processing, chemical, and other fields, high-temperature hot water boilers provide a stable heat source. A pharmaceutical company uses a gas-fired high-temperature hot water boiler to heat process water from 20℃ to 160℃ to meet the requirements of the reaction vessels. Simultaneously, sensible heat is recovered through a flue gas condenser, achieving a comprehensive thermal efficiency of 95%. Airport Energy Center: Hongqiao International Airport's heating system utilizes four 29MW high-temperature hot water boilers, coupled with eight sets of plate heat exchangers, to provide winter heating, summer cooling, and year-round domestic hot water supply to the terminal building. The system dynamically matches the load through flow regulating valves, achieving 18% energy savings compared to steam systems.

IV. Technical Advantages and Safety Features

High Efficiency and Energy Saving: High-temperature hot water boilers have no latent heat loss during vaporization, resulting in a thermal efficiency 3%-5% higher than steam boilers. With enhanced heat transfer technologies such as threaded smoke tubes and corrugated furnace shells, the thermal efficiency of some equipment exceeds 98%.

Safety and Reliability: Water temperatures are below saturation temperature, resulting in low medium energy density and a 90% reduction in explosion risk compared to steam boilers. Modern boilers are equipped with multiple protection devices, such as leakage protection for electrode boilers and low water level alarms for coal-fired boilers.

Environmental Compliance: Through low-NOx combustion technologies (such as staged combustion and flue gas recirculation), nitrogen oxide emissions can be controlled below 15mg/m³, meeting the "dual carbon" target requirements. For example, Hebei Yongxin electric heating boilers employ a water-electricity separation design, achieving zero-emission operation.

V. Development Trends and Challenges

Clean Energy Transition: High-pressure electrode boilers, due to their flexible start-up and shutdown and pollution-free emissions, have become the preferred peak-shaving power source. A thermal power plant in Beijing uses a 10MW electrode boiler, combined with a molten salt energy storage system, to increase the renewable energy consumption rate by 40%.

Intelligent Control: Boiler control systems integrating IoT technology can monitor parameters such as water temperature and pressure in real time and optimize combustion efficiency through AI algorithms. For example, Broad Boiler's ASME-certified products are equipped with smart chips, enabling one-button start-up and shutdown, automatic blowdown, and other functions.

Material Innovation: To cope with high-temperature corrosion, the boiler's heating surfaces use TP347H stainless steel or nickel-based alloy coatings, extending their service life to over 15 years. Simultaneously, lightweight design reduces the transport weight of a single 70MW boiler from 25 tons to 18 tons, lowering installation costs.

Conclusion: As a key piece of equipment for energy conversion, high-temperature hot water boilers are evolving towards higher efficiency, environmental protection, and intelligence. With the deepening implementation of the "dual-carbon" strategy, their applications in areas such as district heating and industrial waste heat utilization will further expand, providing important support for building a clean and low-carbon energy system.