A brief discussion on the industrial boiler market

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The English term for CFB boilers is “circulating fluidized bed boiler”. There are two main types of such boilers: one produces steam, which is used for power generation; the other produces hot water, which can be utilized in industries like fertilizer plants. In these plants, coal is used as a raw material to synthesize fertilizers with the help of steam – this is a typical example of an industrial boiler. Most industrial boilers still burn coal; those that burn gas are generally waste heat boilers designed to recover waste heat. Among industrial boilers, circulating fluidized bed boilers are quite common. Industrial boilers are important thermal energy and power generation equipment; China is the country with the highest production and usage of boilers in the world today. China’s manufacturing industry was established and developed after the founding of the People’s Republic of China. Especially since the reform and opening up, with the vigorous development of the national economy, there are over a thousand enterprises nationwide that hold boiler manufacturing licenses at various levels; these enterprises can produce industrial boilers of different grades. Overview of industrial boilers: For a considerable period in the future, coal-fired industrial boilers will remain the dominant product in China, with most of them being medium- to large-capacity boilers (with a single-unit evaporation capacity of ≥10 t/h). However, coal-fired boilers cause severe environmental pollution. With changes in the energy supply structure and increasingly strict requirements for energy conservation and environmental protection, the development and use of natural gas will enter a period of rapid growth. Small coal-fired industrial boilers will be phased out in the central urban area. Therefore, efficient, energy-saving, and low-pollution industrial boilers that utilize clean fuels and clean combustion technologies will be the trend in product development. 1 Overview of industrial boilers in China 1.1 There are enterprises in China that hold boiler manufacturing licenses; as of the end of 2002, this included 37 enterprises with YJ-grade licenses, and 674 enterprises that held licenses specifically for component manufacturing. In 2002, the installed capacity of industrial boilers nationwide was 576,000 units, with a total thermal power of 1.9946 million MW. In 2002, the manufacturers of Class A and B boilers produced a total of 23,600 industrial boilers, with a capacity of approximately 90,600 steam tons. Statistics show that the total output of the top 50 industrial boiler manufacturers accounts for more than 50% of the total demand. 1.2 Characteristics of the industrial boiler industry: Over the past 15 years, the annual production volume of industrial boilers across the country has remained between 70,000 and 100,000 steam tons. In 1987, the national production of industrial boilers reached 85,483 steam tons, and in 2001 it was still 85,400 steam tons. However, the number of enterprises in the industry has increased from 551 initially to 969, nearly doubling in size. The majority of these newly added enterprises are small-sized firms classified under Categories C and D. These companies actually account for over three-quarters of the total number of enterprises in the industrial boiler industry—a clear case of abnormal development. There are over 1,000 existing boiler manufacturing enterprises in our country; there are too many factories, the products among them are highly similar, and most of them do not engage in mass production. In 2001, only 18 companies had a production volume of over 1,000 steam tons; together they produced 37,613 steam tons worth of boilers, accounting for 44% of the total national output of industrial boilers that year. The annual production capacity of boilers in Class C and D enterprises is only about 50 steam tons on average, with a total of 732 such facilities, indicating a low level of concentration in the industrial boiler manufacturing sector. Due to the large number of production sites, there is an oversupply of small and medium-sized furnaces. Among more than a thousand boiler enterprises, only about 100 have the capability for independent design; most of the others lack basic technical development capabilities. Many small and medium-sized enterprises are struggling; some have numerous problems, leading them to switch production or go out of business. Over the past 10 years, industrial boiler products have undergone some new changes due to various factors. The proportion of industrial boilers with a capacity of ≤ 4 t/h dropped from 60% in 1991 to 30% in 2001, a reduction of almost half, while the proportion of boilers with a capacity of ≥ 10 t/h increased from 25% to 54%, resulting in a demand that exceeded the supply for large-capacity boilers. The proportion of coal-fired boilers declined from 90% in 1991 to 81% in 2001, whereas the proportion of oil and gas-fired boilers increased from less than 6% in 1991 to over 15% in 2001; electric heating boilers began to be used. In terms of combustion methods, the proportion of circulating fluidized bed boilers in the total boiler capacity increased from 3% in 1991 to over 10% in 2001; the share of stoker-fired boilers also saw a slight increase. In terms of the types of industrial boilers, the share of water-tube and fire-tube boilers in terms of capacity dropped from 45% in 1991 to 21% in 2001, while the share of internal combustion boilers increased from less than 4% to over 10%. 2 Challenges and Opportunities Faced by the Industry and Enterprises 2.1 After joining the WTO, China’s boiler industry is under tremendous competitive pressure. After joining the WTO, as the protection provided by manufacturing licenses weakened, the number of foreign companies applying for such licenses in China increased at an astonishing rate of 15% per year. By the first half of 2002, the number of foreign boiler and pressure vessel manufacturers that had obtained domestic manufacturing licenses had reached 626. In recent years, foreign companies have also established 14 joint venture or wholly-owned enterprises in China, most of which produce oil and gas boilers. Due to the low tariffs after entry into the market, a large number of foreign boilers flooded into China’s market: 1,646 units in 2000, 2,491 units in 2001, and 3,246 units in 2002. Therefore, China’s industrial boiler industry and enterprises are facing the pressure of significant tariff cuts and a growing number of foreign companies obtaining permits to manufacture in China. 2.2 Energy-saving and environmental protection requirements are becoming increasingly stringent. Industrial boilers in China consume approximately one-third of the annual total raw coal production. They emit over 600 million tons of CO2 and 5–6 million tons of SO2, accounting for 21% of the country’s total emissions. Our country approved the Kyoto Protocol in 2002; once the protocol comes into effect, we are required to reduce greenhouse gas emissions. Energy conservation and emission reduction in industrial boilers will undoubtedly be a top priority. To reduce the damage caused by SO2 to the environment, major cities have implemented restrictions on the use of coal-fired boilers in urban areas. Recently, Fuzhou City released the “10th Five-Year Plan for the Prevention and Control of Acid Rain and Sulfur Dioxide Pollutants in the Acid Rain Control Area of Fuzhou City”. According to the plan, by 2005, the use of small coal-fired boilers will be phased out within the built-up area of Fuzhou. The urban area will also actively transition to gas-fired, geothermal, and electric boilers. 2.3 Rising prices of raw materials used in boiler manufacturing, along with fierce competition among enterprises. After February 2002, the prices of raw materials for boiler manufacturing rose in the national steel market. The prices of auxiliary equipment used in conjunction with boilers also increased one after another. All these factors put additional cost pressures on boiler manufacturers. On the other hand, due to the large number of manufacturers in the industrial boiler industry and the high degree of similarity among their products, competition among companies – especially price wars – has intensified. There is also undercutting and overt or covert competition during the bidding process; some companies even go to great lengths to gain market share, resulting in increased production without corresponding increases in revenue. This undoubtedly erodes the profits of industrial boiler manufacturers and weakens the ability of some companies to sustain sustainable development, with a few even seeing their future ruined as a result. 2.4 The energy consumption structure will change, and the rapid development of natural gas exploration and utilization will bring opportunities for the growth of industrial boilers. The recoverable reserves of conventional natural gas in our country amount to around 10–14.7 trillion cubic meters. The West-East Gas Transmission Project will be put into full operation by 2004, and the 8 provinces and municipalities along its route will benefit from it. Natural gas from the Sichuan-Chongqing Basin will be supplied to Hunan and Hubei, natural gas from the East China Sea region will reach Ningbo, and natural gas from the Changqing Oil Field will supply North China. Meanwhile, China is actively utilizing international natural gas resources. It will gradually construct a long-distance pipeline linking Central Asia, Russia, China, and South Korea, as well as develop maritime oil and natural gas pipelines from the Middle East through Asia and Australia to China’s southeastern coast. The LNG project in Fujian Province relies on gas supplies from the Tanggu gas field in Indonesia; after extraction, the natural gas is liquefied at low temperatures and transported by sea to the LNG receiving station in Xiuyu, Putian, Fujian. Gas will be supplied to gas consumers in five cities—Fuzhou, Putian, Quanzhou, Xiamen, and Zhangzhou—as well as to newly built gas power plants in Putian, Xiamen, and Jinjiang. Gas supply is scheduled to commence in 2007. All these indicate that the development and application of natural gas in our country have entered a period of rapid growth. The industrial boiler industry should seize this opportunity to develop corresponding natural gas utilization equipment and provide relevant system services. 3. Trends in product development within the industrial boiler industry
In the future, the market development of industrial boiler products will be influenced not only by factors such as the growth rate of China’s national economy and the scale of investments, but also increasingly by energy policies as well as requirements regarding energy conservation and environmental protection. With the spread of high-performance products and improvements in product quality, around 50,000 steam tons of industrial boilers will need to be replaced each year between 2000 and 2010. After 2010, about 70,000 steam tons of industrial boilers will need to be replaced annually. Together with new installations, the demand for industrial boilers is expected to be around 100,000 to 120,000 steam tons per year by 2010. In the future, the proportion of small-capacity coal-fired boilers in large and medium-sized cities will decline significantly. Boilers that utilize clean combustion technologies such as circulating fluidized bed boilers will see rapid development, while gas-fired boilers will make substantial progress as well. There is great market potential for boilers that use municipal waste and biomass as fuel. The market for regenerative electric heating boiler systems will further expand alongside the reform and development of the power industry. Therefore, efficient, energy-saving, and low-pollution industrial boilers that utilize clean fuels and clean combustion technologies will represent the trend in the development of industrial boiler products, moving toward high-end and high-value-added product markets. 3.1 Layer-fired boilers: Layer-fired chain grate boilers are the most common type in China, and these boilers require further improvements in terms of energy efficiency and environmental performance. Greater development potential exists on the basis of washing and screening raw coal while simultaneously improving combustion equipment. Small fixed-grate boilers that still use manual coal feeding and intermittent combustion will inevitably be phased out, to be replaced by newly developed types of boilers. 3.2 Circulating fluidized bed boilers The circulating fluidized bed combustion technology features enhanced heat transfer, high combustion efficiency, wide fuel adaptability, and low pollutant emissions. It should be actively developed and applied in coal-fired industrial boilers with a capacity of ≥ 10 t/h. This type of boiler represents a very promising clean combustion technology. 3.3 Fuel and gas boilers: Fuel or gas-fired industrial boilers can not only improve the thermal efficiency of the boilers, but also significantly reduce pollutant emissions. However, it is constrained by initial investment and operating costs. Furthermore, **with the promotion of policies aimed at reducing fuel consumption, the development of fuel-fired boilers is expected to be curbed. However, as environmental protection efforts intensify, and thanks to projects such as the West-East Gas Pipeline and the utilization of international natural gas resources, most cities are beginning to adopt clean energy sources. As a result, a large number of gas-fired boilers will replace the existing coal-fired boilers, giving the gas-fired boiler market very promising prospects. It is expected that in the future, gas boilers will account for 15% to 20% of the total annual production capacity of industrial boilers. 3.4 Electric heating boilers have advantages such as cleanliness and reliability. However, electricity is a clean secondary energy source, and its price is relatively high; the operating costs of electric heating boilers are 6 times those of coal-fired boilers and 2 times those of oil or gas-fired boilers. As a result, electric heating boilers have not seen much development in China over the years. However, with economic development, the acceleration of power infrastructure construction, and stricter environmental protection requirements—especially after the implementation of time-of-use electricity pricing—electric heating boilers have seen relatively rapid development. The market for electric heating boilers will expand, with storage-type electric boilers remaining the dominant product type. 3.5 Waste incineration boilers: There have been significant changes in the composition of municipal solid waste in China at present. Combustible materials such as paper, plastic, wood, and fibers, along with other organic substances, have increased in quantity; the quality of this waste is now sufficient for incineration. As a result, it has become possible to generate electricity from urban waste incineration, which creates conditions for the development of waste incineration boilers. Waste incineration reduces the volume of waste by 90% and its weight by over 70%. The heat recovered is used to generate steam, with an efficiency of around 85%; approximately 30% of this energy is converted into electricity. Therefore, waste incineration technology will become an emerging industry with great development potential in our country. By drawing on advanced foreign technologies to rapidly develop domestic waste incineration boilers, there is a very broad market prospect for them. 3.6 Water-coal slurry boilers: Water-coal slurry is a new type of coal-based fluid that serves as a clean and environmentally friendly fuel; it is prepared by mixing approximately 35% water, about 65% coal, and 1% to 2% additives. Water-coal slurry retains the combustion properties of coal, while also possessing liquid combustion characteristics similar to those of heavy oil. Water-coal slurry resembles oil in appearance, has good fluidity, is stable for storage and easy to transport, offers high combustion efficiency, and results in low pollution emissions. Domestic practices in burning coal-water slurry have proven that approximately 1.8 to 2.1 tons of coal-water slurry can replace 1 ton of fuel oil, resulting in cost savings of about 600 yuan. Therefore, water-coal slurry has good prospects for replacing oil and gas fuels in industrial boilers that are used on a large scale. In addition, industrial boilers such as condensing boilers and semi-gas flow combustion boilers also have certain potential for development in China, and they should be given attention as well. 4 Conclusion China’s boiler industry is neither a \"sunrise industry\" nor a \"sunset industry\"; rather, it is an industry that will coexist with humanity forever. In China, it is also an industry that continues to develop. However, at present, China’s industrial boiler industry and enterprises are also facing various challenges and opportunities. As main players in market competition, industrial boiler manufacturing enterprises should have a clear understanding of both their external environment and internal conditions. They must define their market positioning and manage it from a strategic perspective, knowing what to do and what not to do. It is essential to adhere to a market-oriented strategy. By relying closely on scientific and technological progress as well as innovation, and under the guidance of **energy and environmental protection policies**, enterprises should adjust their organizational and product structures. They must seize opportunities to develop high-end products that meet market demands and possess unique characteristics. This will facilitate corporate development and ensure strong, sustainable growth potential. Only in this way can they secure a foothold in the fierce market competition. Energy-saving renovation technologies for industrial boilers ① Installation of energy savers for fuel boilers ； The hydrocarbons processed by the fuel energy saver undergo changes in their molecular structure: there are more small molecules, the distance between molecules increases, and the viscosity of the fuel decreases. As a result, the degree of atomization and refinement of the fuel before combustion is greatly improved; it burns fully upon entering the combustion chamber under conditions of low oxygen levels. This allows the air supply required for the combustion equipment to be reduced by 15% to 20%, preventing heat from being carried away through the flue gases, and resulting in a decrease in flue gas temperature by 5°C to 10°C. After being treated by the energy saver, the fuel used in combustion equipment exhibits improved combustion efficiency; as a result, fuel consumption is reduced by 4.87% to 6.10%. Additionally, it is evident that the flame becomes bright and intense, black smoke disappears, and the furnace interior becomes clear and transparent. Thoroughly remove coking from the combustion nozzles and prevent re-coking. Eliminates the buildup of residue on the furnace walls caused by incomplete combustion of fuel, thereby achieving environmental protection and energy conservation. **It reduces the pollution of the air caused by the exhaust gases emitted from combustion equipment; harmful components in these exhaust gases such as carbon monoxide (CO), nitrogen oxides (NOx), and hydrocarbons (HC) are significantly reduced, with the emission of harmful exhaust gases being cut by more than 50%. At the same time, the dust content in the exhaust gas can be reduced by 30%–40%. Installation location: Installed between the oil pump and the combustion chamber or nozzle; the ambient temperature should not exceed 360°C. ② Install an energy saver for condensing gas boilers ； The exhaust gas from gas boilers contains up to 18% water vapor; the large amount of latent heat contained in it goes unused, resulting in high exhaust gas temperatures and significant losses of sensible heat. After burning, natural gas still emits pollutants such as nitrogen oxides and a small amount of sulfur dioxide. Reducing fuel consumption is the best way to cut costs. The condensing gas boiler economizer can be installed directly in the flue of existing boilers to recover energy from the hot exhaust gases, thereby reducing fuel consumption with significant economic benefits. At the same time, the condensation of water vapor helps to absorb pollutants such as nitrogen oxides and sulfur dioxide from the exhaust gases, reducing pollutant emissions and thus playing an important role in environmental protection. ③ Adopt condensing waste heat recovery boiler technology ； In traditional boilers, the flue gas temperature is generally between 160 and 250°C, and the water vapor in the flue gas remains superheated; it is therefore impossible for it to condense into liquid water and release its latent heat of vaporization. As is well known, the thermal efficiency of a boiler is calculated based on the lower heating value of the fuel, without taking into account the heat losses associated with the latent heat of vaporization in the higher heating value of the fuel. Therefore, the thermal efficiency of conventional boilers generally can only reach 87%–91%. The condensing waste heat recovery boiler, on the other hand, reduces the flue gas temperature to 50–70°C, thereby fully recovering both the sensible heat in the flue gas and the latent heat released during the condensation of water vapor, thus improving thermal efficiency ； Condensate water can also be recycled. ④ Heat pipe waste heat recovery technology is used at the rear of the boiler ； Waste heat is the energy that remains unused in energy utilization equipment under certain economic and technical conditions; in other words, it is excess or unused energy. It includes seven types: waste heat from high-temperature exhaust gases, waste heat from cooling media, waste heat from exhaust gases and wastewater, waste heat from high-temperature products and slag, waste heat from chemical reactions, waste heat from combustible exhaust gases, liquids and wastes, as well as the residual pressure of high-pressure fluids. According to investigations, the total waste heat resources in various industries account for approximately 17% to 67% of their total fuel consumption, and the waste heat resources that can be recovered make up about 60% of the total waste heat resources. Superconducting heat pipes are the main heat conduction elements in heat pipe waste heat recovery systems, and they differ fundamentally from ordinary heat exchangers. The heat exchange efficiency of heat pipe waste heat recovery devices can reach over 98%, a level that no ordinary heat exchanger can achieve. The heat pipe waste heat recovery unit is compact, accounting for only 1/3 the size of a conventional heat exchanger. Its working principle is as shown in the diagram: the left side is the flue gas channel, the right side is the clean air (water or other medium) channel, with a partition in the middle to keep them separate and prevent interference. The hot flue gas is discharged through the left channel; as it is discharged, it flows over the heat pipes. When the temperature of the flue gas exceeds 30°C, the heat pipes become active and transfer heat to the right side automatically. At this point, the left side of the heat pipes absorbs heat, and the temperature of the hot flue gas drops as it passes through these heat pipes; the heat is then absorbed by the heat pipes and transferred to the right side. At room temperature, clean air (water or other media), driven by a blower, flows in the opposite direction along the right channel to wash over the heat pipe; at this point, heat is released on the right side of the heat pipe, heating the clean air (water or other media). The temperature of the air increases as it passes through the heat pipe. A waste heat recovery device composed of several heat pipes is installed at the boiler’s exhaust outlet; it absorbs the heat from the flue gas and transfers it rapidly to the other end, thereby reducing the exhaust temperature to near the dew point and minimizing heat loss. The heated clean air can be used to dry materials or fed back into the boiler for reuse. Improve the thermal efficiency of boilers and industrial furnaces, reduce fuel consumption, and achieve energy savings. When designing and manufacturing industrial fuel, gas, and coal-fired boilers, in order to prevent corrosion of the heated surfaces at the rear of the boiler as well as ash accumulation, the exhaust gas temperature under standard conditions is generally not lower than 180°C, and can reach up to 250°C. The emission of hot flue gases not only results in significant waste of thermal energy but also pollutes the environment. A heat pipe waste heat recovery unit can recover the heat from flue gas; the recovered heat can be used to heat water for use as make-up water in boilers and for domestic purposes, or to heat air for use as combustion air in boilers or for drying materials. It saves fuel costs, reduces production expenses, lowers exhaust emissions, and achieves both energy conservation and environmental protection. The investment in renovation pays off within 3-10 months, yielding significant economic benefits. ⑤ Adopt scale prevention and removal technologies ； By using boiler descalers and electronic scale preventers, optimizing the water and steam circulation system, and properly controlling the boiler’s blowdown rate, scale can be reduced and the boiler’s thermal efficiency improved. ⑥ Adopt fuel additive technology ； Additives are incorporated into the fuel to optimize it, thereby reducing soot formation and improving thermal efficiency ； ⑦ Adopt new fuel ； New eco-friendly fuel oils are used to reduce fuel costs. ⑧ Oxygen-enriched combustion technology is employed ； The oxygen content in the air is ≤21%. The combustion in industrial boilers also takes place under such air conditions. Practice has shown that when the oxygen content in the gas burned in the boiler exceeds 25%, energy savings of up to 20% can be achieved ； The boiler’s startup heating time is reduced by 1/2–2/3. Oxygen enrichment involves using physical methods to extract oxygen from air, resulting in a gas composition with an oxygen content of 25%–30%. Oxygen-enriched combustion assistance is a cutting-edge energy-saving and environmental protection technology. Over the past decade or so, driven by increasing environmental regulations and the need to save energy, oxygen-enriched combustion has emerged as a new combustion technology that has seen rapid development around the world. Nowadays, some developed countries in the West require that all new industrial furnaces and boilers use oxygen-enriched air instead of ordinary air for combustion. ⑨ Adopting swirl combustion boiler technology ； As is well known, traditional boilers have two major drawbacks: first, smoke and dust are emitted during combustion, serving as a significant source of pollution ； Second, the coal cinders are not burned fully, resulting in extremely severe energy waste. Compared with traditional industrial boilers, the new pure smokeless and energy-saving swirl combustion boiler technology has absolute advantages. It saves 30%~35% more coal compared to hand-fired boilers, and 25% more coal compared to chain-type automated boilers. Since the pure smoke-free energy-saving technology utilizes PID frequency conversion and ABM power-saving systems, it saves 40% more energy compared to traditional boilers. It enables over 90% combustion and utilization of volatile substances, whereas traditional boilers achieve only around 78% combustion efficiency for such substances, with 22% of the dust being released into the atmosphere. The pure smoke-free energy-saving swirl combustion technology achieves a ash combustion rate of 97%, while traditional boilers have an ash combustion rate of only around 80%. It is for these reasons that this technology allows the furnace temperature to be increased from 1200°C to around 1500°C, improving combustion efficiency, saving fuel, and meeting customers’ needs. ⑩ Replace with air-source heat pump hot water unit technology ； Replace the existing fuel (gas) hot water boiler with an air-source heat pump hot water unit ； It can save 30% to 50% in energy consumption. ⑾ Coal-fired boilers can be converted into fuel (gas) boilers ； Boilers are important heat supply devices in the national economy. Industries such as electricity, machinery, metallurgy, chemicals, textiles, papermaking, and food processing, as well as industrial and domestic heating systems, all require boilers to supply large amounts of thermal energy. A boiler is a device that uses the thermal energy or other forms of energy released by fuel combustion to heat a working medium (an intermediate heat carrier) to certain parameters. A boiler used to heat water and convert it into steam is called a steam boiler, or steam generator; a boiler used to heat water and raise its temperature to turn it into hot water is called a hot water boiler, while a boiler used to heat organic heat carriers is known as an organic heat carrier boiler. From the perspective of energy utilization, a boiler is an energy conversion device. In a boiler, the chemical stored energy of primary energy (fuel) is converted, through the combustion process, into thermal energy contained in the combustion products (flue gas and ash). This thermal energy is then transferred to an intermediate heat carrier (such as water and steam) via heat transfer, and it is this medium that carries the heat to the equipment that requires it. This intermediate heat carrier for transferring heat is considered a secondary energy source, as its purpose is to supply energy to energy-consuming devices. When an intermediate heat carrier is used to convert heat into work in a heat engine, it is called a \"working fluid.\" If the intermediate heat carrier merely transfers heat to a heating device to enable heat utilization, it is usually referred to as a \"heat medium\". Boilers can be classified into four categories according to their use: power station boilers, industrial boilers, ship boilers, and locomotive boilers. The first two types are also known as stationary boilers, as they are installed on a fixed base and cannot be moved. The latter two types are known as mobile boilers. This book introduces fixed industrial boilers. Three main processes take place in a boiler: (1) The fuel burns inside the furnace, and its chemical stored energy is released in the form of heat, resulting in flames and combustion products (flue gas). When selecting a boiler, companies need to consider the following factors: 1. How much steam and hot water is required for the company’s production processes or heating needs. 2. Boiler steam parameters or hot water parameters. 3. Conduct an analysis of the selection relationship between steam boilers and hot water boilers. 4. Selection of industrial boiler types. 5. Type of coal used in the boiler. 6. Others such as dimensions and load variations. 1. How to determine the capacity and number of boilers: Determining the capacity of boilers when purchasing them is an important issue. Generally speaking, the output or capacity of a boiler should be determined based on the steam consumption in the production process, the heating area, and the heat required for domestic hot water. First, the user needs to determine the overall load range ； Next is the peak condition, including the duration of peak loads and the frequency of peaks, that is, the periodicity with which peaks occur, such as the number of peak occurrences per month, as well as the differences between winter and summer on a weekly, monthly, and annual basis. Once the overall load requirements and peak demand are determined, the selection of equipment capacity and quantity can be considered. When making a choice, the issue of backup capacity for emergency shutdowns also needs to be considered. A backup capacity generally refers to one backup boiler. This needs to be determined based on the user’s importance; if high continuity is required in production, the issue of backup equipment must be given careful consideration. The economic operating load for typical boilers is above 75% of the rated load; therefore, the actual load of the boilers in use should generally be above 50% of the unit’s own rated load. In other words, the equipment supplied by the manufacturer should maintain stable high efficiency within a range of 50% to 100% of its rated output. In the past, for safety reasons, users would purchase excessive quantities, resulting in the equipment operating at low load levels for extended periods, which was very uneconomical. For boiler rooms with a total capacity of 8 tons per hour or a thermal power of 6 megawatts (MW) or more, it is appropriate to choose three units with corresponding capacities. Due to the differences between winter and summer, devices with different power outputs can be purchased. However, for newly built boiler rooms, choosing equipment with the same capacity makes operations, maintenance, and management more convenient and cost-effective. Such an arrangement of auxiliary equipment in the boiler room can be planned reasonably. Considering situations with significant differences such as peak and off-peak times, as well as winter and summer, one can also opt for two large-sized and one small-sized devices. Depending on the requirements, it may be necessary to build a new boiler room; choosing a slightly larger number of devices than three is also acceptable, but too many devices should not be used. Instead of opting for numerous devices, it is better to choose equipment with a higher capacity. Given the current quality of domestic equipment, it is necessary to consider having backup units. Foreign equipment has a high reliability and utilization rate, but since they consider the initial investment cost to be small compared to the subsequent operation and maintenance costs, they generally opt for spare equipment. In the event of a shutdown due to an accident, backup equipment can be used, thus ensuring that the operational requirements are met. In foreign countries, where higher requirements are placed on the equipment adjustment ratio, emphasis is mainly placed on the selection of combustion equipment. At present, there are not many types of combustion equipment in our country, so there are limited options in this regard. Abroad, for loads with short peak periods, it is recommended to use thermal storage boilers or large-capacity, high-output shell-type thermal storage internal combustion boilers to handle such loads. In recent years, our country has also made considerable efforts in the field of regenerators, which indeed yield energy-saving results. A regenerator is a device consisting of a large-volume heat storage container along with associated control valves and management components; it is an apparatus for storing thermal energy. The medium stored in regenerators is mostly water (with other media such as steam, etc., as well). The high-temperature water stored in the heat accumulator can release steam at any time to meet production needs. It enables the boiler to operate at a high efficiency and stable load on a regular basis, making it an energy-saving device. To some extent, it can reduce the investment in boiler equipment by industrial and mining enterprises. In many industrial and mining enterprises in our country, the demand for steam is uneven throughout the 24 hours of a day, with periods of high demand and periods of lower demand. In factories operating on a single shift system, work starts at 8 a.m.; after 9 a.m., the steam demand in various workshops rises rapidly, decreases slightly at 12 p.m., rises to a peak around 1 p.m., and then drops back to low levels or even stops altogether by around 4 p.m. The load conditions vary for two-shift and three-shift systems. Therefore, the operation of boilers requires high standards. If the factory operates at high or low loads with large instantaneous fluctuations, a sophisticated automatic combustion control system is necessary to maintain stable steam pressure and ensure a certain level of boiler efficiency. With the use of a regenerator, the boiler can operate continuously at its rated or economic load, simplifying operation and management. When the thermal load in the factory reaches its peak, the regenerator can release steam; when the thermal load is low, the excess steam generated by the boiler can be stored in the regenerator. Before selecting a heat accumulator, industrial and mining enterprises should calculate the steam demand of their own departments and draw a load curve. Analyze the load distribution and methods for balancing steam consumption, and finally determine whether it is necessary to use a heat accumulator. 2. How to determine the parameters for steam and hot water: Users need to determine the parameters for steam or hot water based on their usage requirements. Most of the boilers required by industrial and mining enterprises for production are steam boilers. Steam is mostly used in industries that require heat at specific temperatures to meet the demands of their production processes, such as textiles and dyeing, food and sugar production, rubber and paper manufacturing, and the petrochemical industry. Therefore, the saturated steam parameters of the boiler must be determined in accordance with the requirements of the production process specifications. The advantage of saturated steam is that it ensures a constant temperature required for production. Generally, the pressure in a boiler is always higher than the saturated steam pressure required for production, as this is necessary to overcome pressure losses in the pipes or piping systems. In many cases nowadays, the pressure indicated on the boiler’s nameplate is much higher than the pressure required for operation. For example, many users purchase boilers rated for 13 psi, but in reality they operate at only 5 psi or 6 psi. Operating at such low pressure has an adverse effect on steam quality. As the pressure decreases, the specific volume of the steam increases, resulting in an **increase in the flow velocity at the outlet, which in turn leads to an increase in the amount of water carried by the steam. Generally, the pressure required for actual production, plus the pressure drop needed to overcome all pipeline resistance, along with a 25%~30% safety margin, is sufficient. The head of the feed water pump is specified according to the boiler’s specifications; if the actual operating pressure of the boiler is too low, the electrical energy consumed by the feed water pump represents a significant waste. The steam parameters for boilers in small power plants can be adjusted according to the requirements of the turbine. Most use superheated steam at 25 atmospheres of pressure. If the turbine is designed to handle superheated steam at 13 atmospheres, it is advisable to use a boiler that produces superheated steam at 16 atmospheres, as this will result in better steam quality. For hot water boilers used for heating cities and factories, the commonly adopted temperature parameters are an inlet water temperature of 95 degrees Celsius and an outlet water temperature of 70 degrees Celsius. Currently, there are three types of urban heating systems in China ； Heating for thermal power plants, regional boiler rooms, and decentralized small-capacity boiler rooms. The first two are centralized heating, with the development trend being regional boiler rooms for heating; currently, small-scale decentralized boiler rooms are more common. For district heating, high-temperature hot water boilers and the supply and return water temperatures will adopt a 130/70 parameter. Currently, hot water boiler products come in three options: 95/70, 115/70, and 130/70. In actual use, the operating pressure of hot water boilers is mostly lower than the designed pressure, mainly due to limitations imposed by the existing pipeline system. 3. The selection between steam boilers and hot water boilers: Since hot water heating is more energy-efficient and comfortable than steam heating, there is a shift from steam heating to hot water heating due to energy-saving requirements. However, steam heating is still required in the production processes of many industrial and mining enterprises; as a result, these enterprise users need both steam and hot water. How to choose a model in this situation is a rather complex issue. It is necessary to conduct a specific analysis to determine what equipment should be used. Roughly, there are the following scenarios: A. In industrial and mining enterprises, the amount of steam used is very large while the demand for hot water for heating is relatively small; in such cases, a steam boiler can be used, along with a surface heat exchanger to generate hot water. B. When the heating system requires a large amount of hot water, only a small amount of steam is needed but at a high pressure, it may be advisable to install a separate small steam boiler outside the hot water boiler to serve as the steam source. C. When both the amount of hot water and the amount of steam are relatively small, a boiler suitable for both steam and water can be used. D. When both the volume of hot water and the amount of steam are very large, it is necessary to study the system as a whole. 4. Relationship between coal types and selection: Coal is the fuel for the domestic boilers used in most industries in China. The characteristics of coal are quite complex. For example, anthracite is difficult to ignite, and low-quality coal with high ash content is also hard to ignite. Although lignite has a high volatile content, its moisture content is equally high, making it difficult to ignite as well. These fire-resistant coals impose special requirements on the design of the furnace arch, and the issues in this regard are quite complex. With highly developed industry, the types of fuel used in boilers have been carefully selected and remain relatively stable. Most of the coal supplied in our market is raw coal, and it is difficult to maintain a consistent quality among its various sources. The coal produced by small local mines is put on the market, making the variety of coal used for combustion more complex. Therefore, before purchasing equipment, users must carefully study the development trends of coal varieties with the local fuel supply authorities to ensure that the furnace and arch design are appropriate. 5. Selection of industrial boiler types
A. Selection of combustion equipment type
The choice of combustion equipment primarily depends on the type of fuel used by the enterprise user; however, there is also some overlap regarding the adaptability of combustion equipment to different fuels. In brief, the chain grate, in conjunction with the furnace arch, can burn a wide variety of coal types. However, under a given furnace arch, the adaptability of coal is also within a certain range. Due to the high metal consumption of chain grates, coal with a low calorific value requires a larger grate area, which in turn increases the metal consumption. Therefore, chain grates are suitable for coal with a medium or higher calorific value (above 4000 kcal/h), especially high-quality coal. A reciprocating grate enables mixing during coal combustion, thus allowing the use of a wide range of coal types. However, under the cooling condition of a reciprocating grate, it is not as good as a chain grate, and it is suitable for burning coal with high ash content, as the ash acts to protect the grate bars from overheating and being damaged. Suitable for coal with a calorific value of 2700~4500 kcal/kg. The inverted grate of the coal feeder has the advantage of wide adaptability to coal types, but it is not suitable for burning anthracite, as layered combustion furnaces for anthracite require a long rear arch, whereas the coal feeder uses an open furnace chamber with secondary air. The coal feeder features semi-suspended combustion and provides sensitive load regulation. However, the dust content in the flue gas from the coal feeder grate is high. Therefore, to leverage the advantages of the stoker furnace, it is first necessary to do a good job in reducing the dust content in the exhaust gases. To enable users to choose this option, it is necessary to ensure that there are not too many fine particles in the raw coal, to make use of secondary air in the furnace, and to implement devices for collecting fly ash and restarting combustion; these measures are needed to reduce the dust content in the exhaust gases to a level that is close to or slightly higher than that of chain grate furnaces. The boiling furnace is a new type of furnace that is being actively developed both domestically and internationally. The development of fluidized bed boilers abroad focuses on environmental considerations, while in China the emphasis is more on using lower-quality coal. It can burn any type of coal with a calorific value of 1300 kcal/kg or higher. When burning high-quality coal and low-quality coal, the arrangement of the heating surfaces in the combustion chamber and the operating methods differ. Boiling furnaces have low metal consumption and low costs, offering great prospects for development. In general, coal-fired boilers are not suitable for small industrial boilers with a capacity of 20 tons per hour or less, due to the complexity of their auxiliary equipment and the resulting inefficiency. In the central and southern regions of our country, the multi-fuel boilers that use both coal powder and sugarcane bagasse also have a capacity of over 10 tons per hour. B. Selection of the “boiler” type: Currently, there are three types of boilers: shell-type (fire tube), fire and water tube combined type, and water tube type. Each of these three types has its own characteristics. Shell-and-tube and fire-tube types are suitable for boilers with smaller capacities, such as 4 tons per hour or less. Water-tube boilers are suitable for boilers with larger capacity, such as those with a capacity of 4 tons per hour or more. Generally speaking, water-tube boilers are safe. Under the same external dimensions, the furnace of a water-tube boiler can be slightly taller; the conditions for arranging the furnace arch are better than those in shell-and-tube and fire-tube boilers, which is beneficial for combustion. 6. Other factors and their relationship to selection: In addition to the three most fundamental factors of boiler output, working fluid parameters, and coal type, there are other aspects such as physical dimensions, load variability, water quality of the water source, air pollution, as well as the level of mechanization and automation – all of which are related to the selection of main and auxiliary equipment. The external dimensions of the boiler must be taken into consideration when expanding an existing boiler room. For example, for 10-ton/hour, 6-ton/hour, and 6.5-ton/hour double-drum horizontal (SHL) boilers of the same model, products from different manufacturers can vary significantly in size, so users need to understand the details of the products supplied by the manufacturers. In general, product selection is a rather complex issue that cannot be resolved merely through theoretical discussion. The most crucial issue when making a selection is to understand the actual quality of different products. The selection factors we analyzed above are based on the assurance of reliable quality for various types of products. If the quality of the product is poor, then no matter how good the selection theory is, it’s meaningless. So, in the end, product quality and variety are the fundamental guarantees for selection. Only on the basis of a variety of products and high quality can the selection process achieve the desired results. How to select industrial boilers – determining the capacity of a boiler when purchasing one is an important issue. Generally speaking, the output or capacity of a boiler should be determined based on the steam consumption in the production process, the heating area, and the heat required for domestic hot water. Discussion on the selection of industrial boilers: When purchasing boiler equipment, enterprises must clarify their own requirements as well as the offerings of boiler manufacturers in the market. The factors to be considered in selecting a boiler are summarized as follows: 1. How much steam and hot water is required by the enterprise for its production processes or heating needs. 2. Boiler steam parameters or hot water parameters. 3. Conduct an analysis of the selection relationship between steam boilers and hot water boilers. 4. Selection of industrial boiler types. 5. Type of coal used in the boiler. 6. Others such as dimensions and load variations. (1) How to determine the capacity and number of boilers: Determining the capacity of boilers when purchasing them is an important issue. Generally speaking, the output or capacity of a boiler should be determined based on the steam consumption in the production process, the heating area, and the heat required for domestic hot water. First, the user needs to determine the overall load range ； Next is the peak condition, including the duration of peak loads and the frequency of peaks, that is, the periodicity with which peaks occur, such as the number of peak occurrences per month, as well as the differences between winter and summer on a weekly, monthly, and annual basis. Once the overall load requirements and peak demand are determined, the selection of equipment capacity and quantity can be considered. When making a choice, the issue of backup capacity for emergency shutdowns also needs to be considered. A backup capacity generally refers to one backup boiler. This needs to be determined based on the user’s importance; if high continuity is required in production, the issue of backup equipment must be given careful consideration. The economic operating load for typical boilers is above 75% of their rated load; therefore, the actual load on the boilers in use should generally be above 50% of the unit’s own rated load. In other words, the equipment supplied by the manufacturer should maintain stable and high efficiency within the range of 50% to 100% of its rated output. In the past, for safety reasons, users would purchase excessive quantities, resulting in the equipment operating at low load levels for extended periods, which was very uneconomical. For boiler rooms with a total capacity of 8 tons per hour or a thermal power of 6 megawatts (MW) or more, it is appropriate to choose three units with corresponding capacities. Due to the differences between winter and summer, devices with different power outputs can be purchased. However, for newly built boiler rooms, choosing equipment with the same capacity makes operations, maintenance, and management more convenient and cost-effective. Such an arrangement of auxiliary equipment in the boiler room can be planned reasonably. Considering situations with significant differences such as peak and off-peak times, as well as winter and summer, one can also opt for two large-sized and one small-sized devices. Depending on the requirements, it may be necessary to build a new boiler room; choosing a slightly larger number of devices than three is also acceptable, but too many devices should not be used. Instead of opting for numerous devices, it is better to choose equipment with a higher capacity. Given the current quality of domestic equipment, it is necessary to consider having backup units. Foreign equipment has a high reliability and utilization rate, but since they consider the initial investment cost to be small compared to the subsequent operation and maintenance costs, they generally opt for spare equipment. In the event of a shutdown due to an accident, backup equipment can be used, thus ensuring that the operational requirements are met. In foreign countries, where higher requirements are placed on the equipment adjustment ratio, emphasis is mainly placed on the selection of combustion equipment. At present, there are not many types of combustion equipment in our country, so there are limited options in this regard. Abroad, for loads with short peak periods, it is recommended to use thermal storage boilers or large-capacity, high-output shell-type thermal storage internal combustion boilers to handle such loads. In recent years, our country has also made considerable efforts in the field of regenerators, which indeed yield energy-saving results. A regenerator is a device consisting of a large-volume heat storage container along with associated control valves and management components; it is an apparatus for storing thermal energy. The medium stored in regenerators is mostly water (with other media such as steam, etc., as well). The high-temperature water stored in the heat accumulator can release steam at any time to meet production needs. It enables the boiler to operate at a high efficiency and stable load on a regular basis, making it an energy-saving device. To some extent, it can reduce the investment in boiler equipment by industrial and mining enterprises. In many industrial and mining enterprises in our country, the demand for steam is uneven throughout the 24 hours of a day, with periods of high demand and periods of lower demand. In factories operating on a single shift system, work starts at 8 a.m.; after 9 a.m., the steam demand in various workshops rises rapidly, decreases slightly at 12 p.m., rises to a peak around 1 p.m., and then drops back to low levels or even stops altogether by around 4 p.m. The load conditions vary for two-shift and three-shift systems. Therefore, the operation of boilers requires high standards. If the factory operates at high or low loads with large instantaneous fluctuations, a sophisticated automatic combustion control system is necessary to maintain stable steam pressure and ensure a certain level of boiler efficiency. With the use of a regenerator, the boiler can operate continuously at its rated or economic load, simplifying operation and management. When the thermal load in the factory reaches its peak, the regenerator can release steam; when the thermal load is low, the excess steam generated by the boiler can be stored in the regenerator. Before selecting a heat accumulator, industrial and mining enterprises should calculate the steam demand of their own departments and draw a load curve. Analyze the load distribution and methods for balancing steam consumption, and finally determine whether it is necessary to use a heat accumulator. (II) How to determine the parameters for steam and hot water: Users need to determine the parameters for steam or hot water based on their usage requirements. Most of the boilers required by industrial and mining enterprises for production are steam boilers. Steam is mostly used in industries that require heat at specific temperatures to meet the demands of their production processes, such as textiles and dyeing, food and sugar production, rubber and paper manufacturing, and the petrochemical industry. Therefore, the saturated steam parameters of the boiler must be determined in accordance with the requirements of the production process specifications. The advantage of saturated steam is that it ensures a constant temperature required for production. Generally, the pressure in a boiler is always higher than the saturated steam pressure required for production, as this is necessary to overcome pressure losses in the pipes or piping systems. In many cases nowadays, the pressure indicated on the boiler’s nameplate is much higher than the pressure required for operation. For example, many users purchase boilers rated for 13 psi, but in reality they operate at only 5 psi or 6 psi. Operating at such low pressure has an adverse effect on steam quality. As the pressure decreases, the specific volume of the steam increases, resulting in an **increase in the flow velocity at the outlet, which in turn leads to an increase in the amount of water carried by the steam. Generally, the pressure required for actual production, plus the pressure drop needed to overcome all pipeline resistance, along with a 25% to 30% safety margin, is sufficient. The head of the feed water pump is specified according to the boiler’s specifications; if the actual operating pressure of the boiler is too low, the electrical energy consumed by the feed water pump represents a significant waste. The steam parameters for boilers in small power plants can be adjusted according to the requirements of the turbine. Most use superheated steam at 25 atmospheres of pressure. If the turbine is operated with superheated steam at 13 atmospheres gauge, it is advisable to use a boiler that produces superheated steam at 16 atmospheres gauge, as this will result in better steam quality. For hot water boilers used for heating cities and factories, the commonly adopted temperature parameters are an inlet water temperature of 95 degrees Celsius and an outlet water temperature of 70 degrees Celsius. Currently, there are three types of urban heating systems in China ； Heating for thermal power plants, regional boiler rooms, and decentralized small-capacity boiler rooms. The first two are centralized heating, with the development trend being regional boiler rooms for heating; currently, small-scale decentralized boiler rooms are more common. For district heating, high-temperature hot water boilers and the supply and return water temperatures will adopt a 130/70 parameter. Currently, hot water boiler products come in three options: 95/70, 115/70, and 130/70. In actual use, the operating pressure of hot water boilers is mostly lower than the designed pressure, mainly due to limitations imposed by the existing pipeline system. (III) Selection relationship between steam boilers and hot water boilers: Since hot water heating is more energy-efficient and comfortable than steam heating, there is a shift from steam heating to hot water heating due to energy-saving requirements. However, steam heating is still required in the production processes of many industrial and mining enterprises; as a result, these enterprise users need both steam and hot water. How to choose a model in this situation is a rather complex issue. It is necessary to conduct a specific analysis to determine what equipment should be used. Roughly, there are the following scenarios: A. In industrial and mining enterprises, the amount of steam used is very large while the demand for hot water for heating is relatively small; in such cases, a steam boiler can be used, along with a surface heat exchanger to generate hot water. B. When the heating system requires a large amount of hot water, only a small amount of steam is needed but at a high pressure, it may be advisable to install a separate small steam boiler outside the hot water boiler to serve as the steam source. C. When both the amount of hot water and the amount of steam are relatively small, a boiler suitable for both steam and water can be used. D. When both the volume of hot water and the amount of steam are very large, it is necessary to study the system as a whole. Overall, product selection is a rather complex issue that cannot be resolved merely through theoretical discussion. The most crucial issue when making a selection is to understand the actual quality of different products. The selection factors we analyzed above are based on the assurance of reliable quality for various types of products. If the quality of the product is poor, then no matter how good the selection theory is, it’s meaningless. So, in the end, product quality and variety are the fundamental guarantees for selection. Only on the basis of a variety of products and high quality can the selection process achieve the desired results. 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