Modularized smoke tube type steam generator

Abstract

The invention relates to a modularized smoke tube type steam generator, which is different from a known multi-channel smoke tube type steam boiler and consists of a plurality of smoke tube type gas-steam heat exchange modules (1, 2 and 3). In this way, the smoke tube type steam boiler with the evaporation capacity larger than 20 tons per hour can be manufactured. In order to reduce the exhaust gas temperature, an independent water loop smoke tube type gas-water heat exchange module (4) is connected behind the smoke tube type gas-steam heat exchange modules (1, 2 and 3). All the heat exchange tubes (8) of the smoke tube type heat exchange modules (1, 2, 3 and 4) are coaxially aligned, the number, the length and the diameter of the heat exchange tubes (8) can be changed according to needs, the heat exchange tubes can be conveniently cleaned through a compressed air gun (38), and therefore the modularized smoke tube type steam generator is particularly suitable for biomass fuel such as straw.

Description

Technical Field

[0001] The invention belongs to the field of steam boilers, in particular to a modular smoke tube steam generator suitable for biomass fuels such as straw. Background Art

[0002] Generally, water tube steam boilers are used for high-power and high-pressure steam, while smoke tube steam boilers are the first choice for low-power and low-pressure steam, because smoke tube steam boilers with low pressure and low output are usually more efficient. Smoke tube steam boilers generally require a heavier pressure shell, and generally cannot be manufactured on site like water tube steam boilers, so the output power of smoke tube steam boilers will be limited by transportation weight. Therefore, in practical applications, there are almost no smoke tube steam boilers with an evaporation capacity of more than 10 tons / hour.

[0003] Especially in biomass combustion systems, the advantage of smoke tube steam boilers is that dust deposits in smoke tube heat exchanger pipes are easier to blow off than dust deposits outside water tube heat exchanger pipes. In addition, smoke tube steam boilers have a larger water content and can better play the role of energy buffer, so the stringent requirements for the shutdown and startup speed of similar industrial steam boilers with frequently changing loads are relatively reduced, which is particularly important.

[0004] To improve efficiency, smoke tube steam boilers are generally designed as multi-channel boilers with different tube diameters. Reversing the airflow direction between channels not only increases the draft requirements, but also makes it impossible to blow through all tubes in a concentrated manner. Therefore, smoke tube steam boilers are usually used to burn coal, natural gas or oil, because these fuels usually do not require continuous cleaning maintenance.

[0005] Multi-channel smoke tube steam boilers are generally composed of compact units that have been type-certified. Due to the complex design, they cannot be produced on an automated production line and cannot be customized on demand. The steam generator composed of multiple gas-steam modules designed according to CN201811060700.4 is only suitable for water tube steam boilers and not for smoke tube steam boilers.

[0006] Known smoke tube steam boilers generally have only one water chamber. After the low-temperature feed water is sent into the water chamber, it will soon mix with the existing high-temperature water that determines the exhaust gas temperature. The premature mixing of high and low temperature water will lead to reduced efficiency. In order to use low-temperature water to cool the flue gas, an economizer must be installed downstream. If dust purification is required for biomass fuels such as straw, a separate device needs to be added, but it is not clear where this separate device should be arranged.

[0007] If the flue gas flow rate is increased to avoid ash accumulation, more electricity will be consumed. The rising fuel prices require a deeper optimization of the boiler design. For this reason, designers must be able to freely determine the specifications and dimensions of the smoke tube steam boiler, which is difficult to achieve in traditional multi-channel smoke tube steam boilers.

[0008] In order to improve boiler efficiency and combustion quality, it is considered to recover the flue gas at the tail of the boiler to preheat and dry the straw bales, but in order to ensure that the straw does not fall apart, the drying flue gas should not be higher than 115°C. The known feedwater economizer cannot do this, so the known smoke tube steam boiler cannot produce steam and hot water at the same time. Summary of the invention

[0009] The task of the present invention is to design a modular smoke tube steam generator suitable for biomass fuels such as straw, with a steam evaporation capacity of more than 10 tons / hour, a simple design and structure, and can be automatically processed and manufactured in the factory and then transported by ordinary heavy trucks or exported in containers. The surface of the smoke tube heat exchanger is easy to clean during operation, and the exhaust temperature is much lower than that of the known modular smoke tube steam generator, allowing designers to optimize and select all heat-related specifications and dimensions as needed.

[0010] The modular smoke-tube steam generator of the present invention is composed of a plurality of cylindrical, completely horizontally placed, sequentially arranged, pressure-resistant, smoke-tube heat exchange modules. The heat exchange tubes of the smoke-tube steam generator are all arranged horizontally and parallel to each other in the longitudinal direction.

[0011] The steam chambers of the gas-steam heat exchange modules of the modular smoke-tube steam generator of the present invention are interconnected through steam pipes, and the water storage chambers are interconnected through an overflow pipe arranged outside the modular smoke-tube heat exchange device. In order to overcome the possible slight displacement caused by thermal expansion of the heat exchange module, the overflow pipe is provided with a curvature.

[0012] In order to reduce the flue gas temperature after heat exchange as much as possible, one or more smoke tube type gas-water heat exchange modules with the same outer diameter, coaxial and the same number of heat exchange tubes or an economizer can be connected downstream of the modular smoke tube type gas-steam heat exchange module.

[0013] The modular smoke-tube steam generator of the present invention is provided with hot water by an independent hot water circuit, and the heat energy of the hot water can be used to preheat feed water, preheat combustion air, dry fuel or provide heat. The heat exchange tube with the largest diameter is arranged in the first smoke-tube gas-steam heat exchange module, and the heat exchange tube with smaller diameter can be used sequentially in the subsequent smoke-tube heat exchange modules.

[0014] Since the number of heat exchange tubes in each smoke-tube heat exchange module is the same, heat exchange tubes of different diameters can also be used in the same smoke-tube heat exchange module to optimize the flow rate. All smoke-tube heat exchange modules are firmly connected by horizontal fixed tie rods, which extend over the entire length of the modular smoke-tube steam generator of the present invention.

[0015] The horizontal fixing rod is arranged in the insulation layer outside the pressure shell of the modular smoke tube steam generator, so the temperature difference between the pressure shell and the horizontal fixing rod is always small and has little effect on the tensile stress of the horizontal fixing rod.

[0016] Since the modular smoke-tube steam generator of the present invention may be relatively long, its possible thermal expansion must be considered, and such thermal expansion generally only occurs in the direction of the heat exchange flue gas flow. One end of the first smoke-tube gas-steam heat exchange module is fixed to a fixed bracket connected to the equipment foundation at one side of the heat exchange flue gas inlet chamber, and the other supporting points of the modular smoke-tube heat exchange module of the present invention are arranged on a movable bracket with rollers below to prevent thermal expansion.

[0017] In order to accurately calibrate the position between the smoke tube heat exchange modules of the present invention during assembly, each movable bracket with rollers is mounted on a support plate with a large number of adjustment screws. In order to evenly distribute the load on the equipment foundation and prevent the smoke tube heat exchange module of the present invention from deforming, the torque of these adjustment screws is adjusted with a torque wrench so that they all have approximately the same torque.

[0018] If the hygroscopic dust generated by straw burning accumulates between the vertical perforated plates of the smoke tube heat exchange module, the conformal space between the vertical perforated plates of the smoke tube heat exchange module is at risk of corrosion. Therefore, it is necessary to fill the conformal space with a hardening material, such as cement mortar with very fine particles, to prevent corrosion. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A simplified side view of a modular smoke-tube steam generator is shown.

[0020] Figure 2 Shows a cross section of a smoke tube heat exchange module mounted on a drum.

[0021] Figure 3 A side view showing the transition area between two smoke-tube modules.

[0022] Figure 4 The figure shows the situation of filling the conformal space of the smoke tube heat exchange module with materials such as cement mortar.

[0023] Figure 5 A side cutaway view of the heat exchange flue gas inlet chamber with a compressed air gun is shown.

[0024] In the figure: 1-first smoke tube type gas-steam heat exchange module, 2-second smoke tube type gas-steam heat exchange module, 3-third smoke tube type gas-steam heat exchange module, 4-smoke tube type gas-water heat exchange module, 5-equipment foundation, 6-pressure-resistant shell, 7-water level sensor, 8-heat exchange tube, 9-heat exchange water supply, 10-steam pipe, 11-overflow pipe, 12-steam chamber, 13-water storage chamber, 14-heat exchange flue gas inlet chamber, 15-heat exchange flue gas discharge chamber, 16-anti-thermal expansion soft connection, 17-induced draft fan, 18-fixed bracket, 19 -reinforcement ribs, 20-movable bracket with rollers, 21-columnar rollers, 22-steel plates, 23-leveling layers, 24, -adjusting screws, 25-horizontal fixing rods, 26-insulation layers, 27-sealing strips, 28-rubber tubes, 29-cement mortar injection holes, 30-cement mortar, 31-cement mortar funnels, 32-cement mortar vibrators, 33-compressed air gun holes, 34-water-cooled walls, 35-insulation layers, 36-heat-resistant ceramic layers, 37-ball valves, 38-compressed air guns, 39-support plates. DETAILED DESCRIPTION

[0025] The present invention will be described in detail by means of an embodiment, which is a modular smoke tube steam generator having a steam output of about 17 tons / hour at a pressure of 1.25 MPa.

[0026] according to Figure 1 The modular smoke-tube steam generator is composed of a first smoke-tube gas-steam heat exchange module (1), a second smoke-tube gas-steam heat exchange module (2), a third smoke-tube gas-steam heat exchange module (3) and a smoke-tube gas-water heat exchange module (4). The modules are sequentially arranged on a completely horizontal equipment foundation (5).

[0027] All smoke tube heat exchange modules (1, 2, 3, 4) have a pressure-resistant casing (6), and they should also contain other statutory safety equipment and devices as well as respective overflow pipes (11), especially respective water level sensors (7).

[0028] All the smoke-tube heat exchange modules (1, 2, 3, 4) contain the same number of heat exchange tubes (8), and the diameters of these heat exchange tubes (8) are different, but each heat exchange tube (8) in all the smoke-tube heat exchange modules (1, 2, 3, 4) is arranged in sequence and coaxially aligned. Only straight-line flow can occur in the heat exchange tube (8) and no deviation can occur. Therefore, the modular smoke-tube steam generator of the embodiment of the present invention can be regarded as a one-way boiler, so that the surface of all the heat exchange tubes (8) can be cleaned at one time using compressed air.

[0029] The heat exchange feed water (9) is sent to the third smoke tube type gas-steam heat exchange module (3). The smoke tube type gas-water heat exchange module (4) provided in this embodiment can help achieve low-temperature smoke exhaust. However, if the smoke tube type gas-water heat exchange module (4) is not used, an economizer module can also be arranged to replace the third smoke tube type gas-steam heat exchange module (3) or the smoke tube type gas-water heat exchange module (4), or the third smoke tube type gas-steam heat exchange module (3) and the smoke tube type gas-water heat exchange module (4) to preheat the feed water of the steam generating device of the present invention. The economizer module here is shorter in length but has the same diameter as the smoke tube type gas-steam heat exchange module (1, 2). In this embodiment, the length of all smoke tube type heat exchange modules (1, 2, 3, 4) is 3.5 meters.

[0030] The smoke tube type gas-steam heat exchange modules (1, 2, 3) of the present invention are interconnected on one side of the steam chamber (12) via a steam pipe (10). The large diameter steam pipe (10) can achieve a very small pressure difference between the steam chambers (12), so that the water level in the smoke tube type gas-steam heat exchange modules (1, 2, 3) is not affected.

[0031] On one side of the water storage chamber (13), the smoke tube type gas-steam heat exchange modules (1, 2, 3) are interconnected through an overflow pipe (11). The diameter of the overflow pipe (11) in this embodiment is set to 160 mm, so that the water flow rate between the third smoke tube type gas-steam heat exchange module (3) and the second smoke tube type gas-steam heat exchange module (2) is less than 0.23 m / s, so the pressure loss is very small and has no effect on the water level. The water level of the third smoke tube type gas-steam heat exchange module (3) will be slightly higher than that of the second smoke tube type gas-steam heat exchange module (2), while the water level of the first smoke tube type gas-steam heat exchange module (1) is the lowest, but only the millimeter level water level difference is considered when setting the water level sensor (7).

[0032] The outer diameter of all the smoke tube type heat exchange modules (1, 2, 3, 4) is 2.95 meters, so they are suitable for road transportation. The heaviest first smoke tube type gas-steam heat exchange module (1) is about 16.5 tons, which is suitable for non-special transportation tools to carry.

[0033] All the smoke tube type heat exchange modules (1, 2, 3, 4) in this embodiment include 183 heat exchange tubes (8), wherein the first smoke tube type gas-steam heat exchange module (1) only includes DN100 (φ108 mm) heat exchange tubes (8), and the second smoke tube type gas-steam heat exchange module (2) only includes DN80 (φ89 mm) heat exchange tubes (8). In order to optimize the second smoke tube type gas-steam heat exchange module (3) and the smoke tube type gas-water heat exchange module (4) in this embodiment, two types of heat exchange tubes (8) with diameters of φ89 mm and φ76 mm are selected. It can be seen that according to the present invention, the designer can set the flue gas flow rate, the number of heat exchange modules and the number of heat exchange tubes (8) as needed, and the diameter, length and material of the heat exchange tubes (8) can also be changed, so that the design of the entire modular smoke tube type steam generator is optimally optimized.

[0034] Hot flue gas at 720-920°C (850°C in this embodiment) enters the modular smoke tube steam generator through the heat exchange flue gas inlet chamber (14), and is then discharged through the heat exchange flue gas discharge chamber (15) via the anti-thermal expansion flexible connection (16) and the induced draft fan (17).

[0035] The modular smoke tube steam generator is firmly connected to the equipment foundation (5) on one side of the heat exchange smoke inlet chamber (14) through a fixed bracket (18) and a reinforcing rib (19), and other movable brackets (20) with rollers fall on columnar rollers (21), so that the modular smoke tube steam generator can overcome thermal expansion along the gas flow direction. Each smoke tube gas-steam heat exchange module (1, 2, 3) includes a water level sensor (7), and a signal from one of the water level sensors (7) will start the heat exchange water supply (9).

[0036] Figure 2 The cross section of the smoke tube type heat exchange module installed on the drum is shown, 183 heat exchange tubes (8) are supported by a movable bracket (20) with rollers and a columnar roller (21), and the steel plate (22) arranged on the equipment foundation (5) is leveled by a leveling layer (23) composed of hardened material.

[0037] The precise positioning of all the smoke tube type heat exchange modules (1, 2, 3, 4) is achieved by a support plate (39) with a large number of adjustment screws (24), and the torque of the adjustment screws (24) is adjusted by a torque wrench, which can not only ensure that all the smoke tube type heat exchange modules (1, 2, 3, 4) are accurately close together, but also ensure that the weight load is evenly distributed, thereby preventing the smoke tube type heat exchange modules (1, 2, 3, 4) from being deformed.

[0038] All the smoke tube type heat exchange modules (1, 2, 3, 4) are interconnected by a horizontal fixed tie rod (25), and the horizontal fixed tie rod (25) extends to the entire length of all the smoke tube type heat exchange modules (1, 2, 3, 4). The horizontal fixed tie rod (25) is located in the insulation layer (26) outside the pressure-resistant shell (6), so the temperature of the horizontal fixed tie rod (25) is always close to the temperature of the pressure-resistant shell (6), and the thermal expansion of the two is almost synchronized. The horizontal fixed tie rod (25) is made of spring steel and can be pre-tightened with a torque wrench. Its tensile stress always remains positive even when the temperature changes, and the thermal expansion stress is always lower than the allowable value of the spring steel.

[0039] All smoke tube type heat exchange modules (1, 2, 3, 4) are connected to each other only by tension and only generate forces in the longitudinal direction, and no local forces will be generated in the vertical direction to affect the safe operation of these pressurized heat exchange modules.

[0040] Figure 3 A side view of the connection area between two smoke tube heat exchange modules connected by horizontal fixed tie rods (25) is shown. The modular smoke tube steam generator load is distributed over the entire cylindrical roller (21). There is a sealing strip (27) and a sealing ring in the sealing strip (27) that is not shown in this figure between the two smoke tube heat exchange modules, so that cement mortar (30) can be filled in the conformal space between the two smoke tube heat exchange modules.

[0041] An overflow pipe (11) of a certain length is used to balance the water level between the smoke tube type gas-steam heat exchange modules (1, 2, 3), and the overflow pipe (11) arranged outside the thermal insulation layer (26) has a certain curvature to overcome the thermal expansion deformation of the smoke tube type heat exchange module.

[0042] Figure 4 The invention discloses a method for filling the conformal spaces between smoke tube type heat exchange modules (1, 2, 3, 4) with cement mortar (30). Filling the hollow conformal spaces can prevent the hygroscopic dust generated by biomass combustion from accumulating therein and causing corrosion.

[0043] After all the smoke tube type heat exchange modules (1, 2, 3, 4) are installed, the rubber tube (28) is passed through all the heat exchange tubes (8) and pressurized to seal the overlapping parts of the heat exchange tubes (8), and then a cement mortar injection hole (29) is punched through the insulation layer (26) and the pressure-resistant shell (6). With the help of a cement mortar vibrator (32), cement mortar (30) is filled into the hollow conformal space from the cement mortar injection hole (29), vibrated and the air is discharged.

[0044] Figure 5The side cross-sectional view of the heat exchange flue gas inlet chamber (14) with a compressed air gun (38) is shown, and the 850°C heat exchange flue gas enters the first smoke tube type gas-steam heat exchange module (1) through the heat exchange flue gas inlet chamber (14). The heat exchange flue gas inlet chamber (14) is made of steel, and is arranged with a double-layer water-cooled wall (34), and the inner lining is composed of a heat insulation layer (35) and a heat-resistant ceramic layer (36).

[0045] A compressed air gun channel (33) with a ball valve (37) is arranged opposite each heat exchange tube (8). When the ball valve (37) is opened and the compressed air gun (38) is pushed in, compressed air can be sprayed out through the compressed air gun (38) to clean the dust on the surface of the heat exchange tube (8).

[0046] In this embodiment, the flue gas waste heat after the flue gas-steam heat exchange module generates steam can be recovered and converted into hot water through the flue gas-water heat exchange module (4), so that the flue gas waste heat can be further utilized. The modularized flue gas-steam generator of the present invention has a simple design and structure, can realize automated production, reduce manufacturing costs and improve equipment quality, thereby expanding the market for flue gas-steam boilers and improving product competitiveness.

[0047] Obviously, the above embodiments are only examples for clear explanation, and are not intended to limit the implementation methods. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from this are still within the protection scope of the present invention.

Claims

1. A modular smoke tube steam generator, comprising a smoke tube gas-steam heat exchange module, a smoke tube gas-water heat exchange module, a pressure-resistant shell, a heat exchange tube, a steam tube, a steam chamber, a water storage chamber and other safety and control devices required by law; characterized in that: The modular smoke tube steam generator is composed of a plurality of cylindrical smoke tube gas-steam heat exchange modules (1, 2, 3) which are completely horizontally placed and sequentially arranged. The heat exchange tubes (8) of the smoke tube gas-steam heat exchange modules (1, 2, 3) are interconnected, the steam chambers (12) of the smoke tube gas-steam heat exchange modules (1, 2, 3) are interconnected through steam pipes (10), and the water storage chambers (13) thereof are interconnected through curved overflow pipes (11) arranged outside the smoke tube gas-steam heat exchange modules (1, 2, 3).

2. A modular smoke tube steam generator according to claim 1, characterized in that: A smoke tube type gas-steam heat exchange module (1, 2, 3) is arranged behind the smoke tube type gas-water heat exchange module (4), which has the same outer diameter and the same arrangement method and number of heat exchange tubes (8) as the smoke tube type gas-steam heat exchange modules (1, 2, 3), and the water around these heat exchange tubes (8) comes from an independent water circuit.

3. A modular smoke tube steam generator according to claim 2, characterized in that: All the smoke-tube heat exchange modules (1, 2, 3, 4) are connected together by horizontally extending, prestressed horizontal fixed tie rods (25), which extend over the entire length of the modular smoke-tube steam generator and are arranged between the pressure-resistant shell (6) and the insulation layer (26).

4. A modular smoke tube steam generator according to claim 1, characterized in that: All the smoke-tube type heat exchange modules (1, 2, 3, 4) comprise heat exchange tubes (8) of different diameters, wherein the diameters of the heat exchange tubes in each smoke-tube type heat exchange module (1, 2, 3, 4) may also be different.

5. A modular smoke tube steam generator according to claim 1, characterized in that: The first smoke tube type gas-steam heat exchange module (1) is fixed on a fixed bracket (18) connected to the equipment foundation (5) on one side of the heat exchange smoke inlet chamber (14), and the other supporting points of the modular smoke tube type steam generator are supported on a movable bracket (20) with rollers supported by a columnar roller (21).

6. A modular smoke tube steam generator according to claim 1, characterized in that: The columnar roller (21) rolls on the support plate (39), and the accurate position of the support plate (39) in the vertical direction is determined by a plurality of adjusting screws (24), and the torque of the adjusting screws (24) is adjusted by a torque wrench.

7. A modular smoke tube steam generator according to claim 1, characterized in that: The hollow conformal spaces between the smoke tube type heat exchange modules (1, 2, 3, 4) are densely filled with cement mortar (30).

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