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SG rotary air preheater

key word:Heat exchange element

Category:


Product description

SG rotary air preheater

 

1. introduction

1.1. Main application occasions and uses

The equipment is mainly used as waste heat recovery equipment, and the main application occasions include the following three aspects:

1.1.1. Air preheater in large power plant boiler equipment.

1.1.2. Flue gas recuperator of denitration unit (SCR) with flue gas reheat system.

1.1.3. Waste heat recovery device of blast furnace, calciner and other equipment.

1.2. Model meaning

2-34-VI(T)-2100(2300)-SMR

2 -------- number of preheaters for each equipment used, 1~4

34 -- air preheater diameter serial number, 7~36

VI -------- V: vertical layout, the hot end is at the bottom; VI: vertical layout, the hot end is on the top; H: horizontal layout

(T) - - -Omitted for bi-section; T: tri-section; Q: quarter-section

2100 ------ height of heat exchange surface: total height of heat transfer elements (mm)

(2300) --- maximum allowable height: if there is resiDual space at the hot end of preheater, it is the total height of the maximum heat transfer element that can be installed

SMR--------Rotor structure: two piece assembly type, omitted, M: Full moDular; SM: semi moDular;

Shape: octagonal shape, omitted; R: round shape; 

Air preheaters - omitted: GGH: flue gas - flue gas preheaters, HAP: high temperature waste heat recovery device.

1.3. Structural features

The rotary air preheater of SG Co., Ltd. is based on the latest technology imported from ALSTOM company, and has carried out a number of adaptability optimization in Chinese market. It has the advantages of advanced technology, good reliability, reasonable design structure and fast installation, and has a variety of design methods to meet the actual needs of different users.

1.3.1. Shape and distribution. According to the shape of the rotor shell, the air preheater can be divided into square shape (only used for small integral factory air preheater), octagonal (see Figure 3-1) and cylinder shape (see Figure 3-2); according to the number of flue gas compartments, it can also be divided into two compartments (bi-section), three compartments (tri-section) and four compartments (quarter-section) (see Figure 3-3).

Two compartment air preheater is used in small pulverized coal boiler and large oil and gas fuel boiler, three compartment air preheater is used in large pulverized coal boiler, and four compartment air preheater is used in large CFB boiler. The air preheater used in non boiler occasions is mostly two compartment type. Compared with octagonal shape preheater, circular shell preheater has the advantages of less installation site, simpler structure and faster installation.

1.3.2. Rotor structure. SG adopts the moDule structure of quick installation to design the large preheater rotor. The combination of pin shaft and welding can effectively speed up the installation progress. Two typical rotor assembly methods are shown in Fig. 3-4.

1.3.3. Replacement method of heat transfer elements. Each layer can be designed to be lifted in from the top and replaced by drawer type from the side, which is greatly convenient for users to repair. The installation (replacement) mode of heat transfer elements is shown in Fig. 3-5.

1.3.4. Heat transfer elements. The basic development of SG preheater heat transfer elements is completed by the heat transfer element Development Laboratory of Alstom preheater company in the United States and SMR Research Institute of Sweden. A professional testing laboratory is set up in Shanghai Jiaotong University, which can test various performance data and have been verified by a large number of computers. Using large-scale assembly line manufacturing, not only the speed is fast, but also the geometric dimension is accurate in place. The waveforms of several commonly used heat transfer elements are shown in Fig. 3-6 and Fig. 3-7.

Different waveforms are used for fuels with different characteristics, and the specific application ranges are as follows:

1.3.4.1. DU series. At present, it is widely used in the hot section and middle temperature section of preheater. It is used in Medium Ash bituminous coal fuel. It has good heat transfer performance and anti clogging ability.

1.3.4.2. DUN series. In order to optimize on DU series, it has no pure corrugated plate, two pieces are positioning plate, groove pitch is twice of DU, two pieces are staggered half pitch, corrugated groove depth is slightly larger than DU, heat transfer effect is better than Du series, spacing between plates is larger than DU, anti blocking ability is also very good, it is a new generation of heat transfer components.

1.3.4.3. FNC series. The characteristics of the system waveform are that the grooves on the two corrugated plates are inclined, and there is no ripple between the grooves; the two pieces of elements have the same form and are arranged alternately; the heat transfer effect is the best among all types, but the cross contact point of grooves is easy to form ash blockage and is not easy to clean, so it is not suitable for medium temperature section of preheater. It is generally used for low ash fuel (including oil and gas); it should be used with caution in high ash fuel.

1.3.4.4.CU series. The positioning plate is a continuous deep corrugated plate. The pure corrugated plate and DU are basically the same, and the heat transfer effect is slightly worse than that of DU, but the operation resistance is large and the ash blocking resistance is acceptable, so it is rarely used at present.

1.3.4.5. NF series. The utility model has the advantages of low soot blowing efficiency, low soot blowing pressure and low soot blowing pressure.

1.3.4.6. UNF series. The heat transfer efficiency of NF series locating plate is better than that of NF, and the other one is still composed of flat plate or shallow corrugated plate with depth less than 1 mm, which can be used in GGH of desulfurization system.

1.3.4.7. DNF series. The pattern of the two plates is the same (but the inclined direction is opposite), and the ripple includes straight groove, plain pattern and inclined pattern. The straight groove and plain grain form a completely closed line, which separates the micro channel of heat transfer element from each other, which can keep the pressure attenuation slow down after the soot blowing steam enters the element, and the effective cleaning depth is greatly increased. The wave heat transfer capacity of this series is similar to that of DU series, especially suitable for flue gas air preheater with higher cold section heat transfer elements and air preheater with SCR system.

1.3.5. Air leakage control. A series of advanced sealing control methods have been used in the air preheater of SG in recent 10 years. The air leakage rate of qualified installation and commissioning equipment is 100%. A series of advanced design methods between rotor and shell have achieved the purpose of long-term reliable operation under the condition of close to zero clearance. The effective air leakage control methods used in practice are as follows:

1.3.5.1. Multiple seals. A few days ago, the flue gas and air in the preheater are all double sealed, and the primary air sealing area with high pressure difference is triple sealed.

1.3.5.2. End face bypass seal is set at cold end. After the self deformation of the rotor, the cold end periphery of the rotor slips over the end face bypass seal, which almost completely prevents the air from passing to the side of the rotor, and the source of axial air leakage is greatly reduced.

1.3.5.3. Seal plate to replace gap seal with Welded static seal. The cold end is welded with the axial sealing plate and the shell, and there is no air leakage in the operation stage, so the air leakage rate can be guaranteed for a long time.

1.3.5.4. Follow up seal is set at the end of sealing plate. It can completely prevent the air leakage at the gap left for the expansion of the sealing plate.

1.3.5.5. Set up pressurization and purging sealing system. In the middle of GGH sealing plate, the sealed net flue gas higher than the original flue gas pressure head is input through the high pressure head sealing fan, which can prevent the direct leakage of the original flue gas to the net flue gas; the purging wind energy sent to one side of the sealing plate will blow away the original flue gas carried by the rotor and prevent it from being brought into the clean flue gas. In theory, the system can also be used in air preheater, but the cost is high.

1.3.5.6. Effective and available hot end gap tracking system shall be adopted. The most advanced design uses the flue gas population temperature as the signal source to control the hot end sealing plate, greatly simplifying the system. For 1000MW class preheater, the system can reduce the overall air leakage rate by half.

1.3.5.7. Follow up adjustment of sector plate at hot end. The inner end of the hot end sector plate is suspended on the guide bearing, which ensures that it moves up and down synchronously with the axial expansion of the rotor, avoids large-scale friction inside the hot end, and maintains a small air leakage gap under all loads.

In recent years, the actual air leakage rate control effect of the unit preheater in operation is as follows (for all qualified preheaters installed and debugged)

300MW unit: 5% ~ 6% in one year and less than 8% in one overhaul period; (no hot end gap tracking system is set)

600MW units: 4% ~ 6% in one year and < 7% in one overhaul period;

1000MW units: 4% ~ 5% in one year and < 6% in one overhaul period.

When the sealing structure of the preheater is correctly installed and the flue gas temperature does not fluctuate greatly (within an overhaul period of 40 ℃ higher than the design value, generally 4 years), there is no need for special maintenance of the preheater equipment. Even if there is excessive wear of the seal, the air leakage rate index can quickly return to the initial state after readjusting to the design clearance.

1.3.6. Transmission device. It is up to the user to decide whether the belt drive (see Fig. 3-8) or the central shaft drive (see Fig. 3-9) is adopted for the general small unit (diameter less than 12m) of SG preheater. For the large diameter preheater, it is recommended to adopt the belt drive mode which is less affected by the change of rotating torque and works reliably.


1.3.7. Preheater bearing system. The guide bearing of preheater adopts double row centripetal spherical roller bearing, and the new design uses tension sleeve to connect the preheater shaft and bearing, so as to avoid the possibility of rotor deflection caused by loose locking bolt of connecting sleeve. The support bearing adopts spherical thrust bearing, and the bearing safety ratio is higher than 10 times, which ensures the long-term and reliable use of the bearing. The guide and support bearings are equipped with lubricating oil stations, which can timely cool and filter the lubrication, and effectively improve the working conditions of bearings.

1.3.8. Fire alarm and fire fighting devices. The SG is designed with an infrared head to directly monitor the metal temperature at the cold end of the rotor. The reaction speed is millisecond. It can give an alarm before the open fire occurs. At the same time, the swing drive mode is adopted. The actuator is outside the preheater, so there is no operation jam. The probe has a self-cleaning device, so the maintenance is very convenient; The thermocouple probe is equipped with a temperature monitoring thermocouple every 300 mm along the radial direction of the rotor. There is no blind area. The specially designed control system can eliminate the interference caused by the sudden change of flue gas and air temperature at the inlet and outlet of the preheater caused by the boiler (rapid load increase, startup of air heater and hot air recirculation), and the false alarm rate is extremely low. Large diameter nozzles are used in the fire pipe network of all lattices arranged above the preheater device to ensure that all rotor surfaces are covered and sufficient water is provided to meet the needs of rapid fire extinguishing.

1.3.9. Cleaning and soot blowing system. Each preheater is equipped with a large Dust blowing system, which can clean the upper and lower pipes for 1 hour. For the preheater with high cooling section layer (equipped with SCR boiler and flue gas air preheater), the soot blower is designed with double medium (steam + high pressure water) double soot blowing pipe, which can be used for on-line micro high pressure water flushing.

1.3.10. Shutdown alarm system. The system is used to monitor the rotation of the rotor. It is composed of the induction hoop installed on the supporting end shaft of the preheater and the induction probe fixed on the lower beam of the preheater. The display accuracy of the rotor speed is 0.03r/min.

1.4. Working principle

The heat exchange principle of rotary preheater is shown in Fig. 3-10 (taking VI type air preheater as an example). After the flue gas enters the preheater, the heat storage element inside the rotor is heated. After the rotor turns to the air side, the heat carried by the heat storage element is released to the air flowing through the rotor. The rotor rotates continuously, and the heat exchange process also continues.

1.5. Product series

The most basic parameter characterizing the preheater is the inner diameter of the rotor shell plate. The model number of preheater is used to correspond with it: the number of rotor compartments represents the number of radial cells in which the rotor is subdivided into heat transfer elements by radial diaphragms; The rotor speed is the rotation speed of the preheater in the operation stage. High speed will increase the heat storage rate of the rotor, but also increase the air leakage and operation power consumption. Therefore, the speed of the preheater has an optimal value, which is generally 1 ~ 1.5r/min for large preheaters. See table 3-1 for the main characteristic parameters of rotary air preheater. In table 3-1, the data is not listed because the preheater with model less than 24.5 is not used in large boiler units.

Table 3-1 main characteristic parameters of rotary air preheater

Model Rotor Inner diameterm common speedr/min Structure forms the rotor can be used in Optional number of rotor compartments
24.5 6.89 1.56 Two pieces assembly, half module 12182436
25 7.2 1.5 Two pieces assembly, half module 12182436
25.5 7.62 1.42 Two pieces assembly, half module 12182436
26 7.93 1.36 Two pieces assembly, half module 12182436
26.5 8.25 1.49 Two pieces assembly, half module 12182436
27 8.65 1.42 Two pieces assembly, half module 12182436
27.5 9.01 1,36 Two pieces assembly, half module 12182436
28 9.47 1.3 Two pieces assembly, half module 12182436
28.5 9.93 1.2 Welding assembly, half module 243648
29 10.33 1.15 Welding assembly, half module, full module 243648
29.5 10.84 1.1 Welding assembly, half module, full module 243648
30 11.3 1.05 Welding assembly, half module, full module 243648
30.5 11.83 1.12 Welding assembly, half module, full module 243648
31 12.39 1.07 Welding assembly, half module, full module 243648
31.5 12.95 1.03 Welding assembly, half module, full module 243648
32 13.5 0.99 Welding assembly, half module, full module 243648
32.5 14.25 1.28 Welding assembly, half module, full module 243648
33 14.95 1.23 Welding assembly, half module, full module 243648
33.5 15.62 1.24 Welding assembly, half module, full module 243648
34 16.4 1.19 Welding assembly, half module, full module 243648
34.5 17.25 1 Welding assembly, half module, full module 364860
35 18.1 I.00 Welding assembly, half module, full module 364860
35.5 18.91 1 Welding assembly, half module, full module 364860
36 19.83 1 Welding assembly, half module, full module 364860

1.6. Technical development of rotary air preheater

SG is the first manufacturer of rotary air preheater with heating surface in China. It is also the largest professional supplier in China. By 2008, SG has a manufacturing history of more than 50 years. The first typhoon hood rotary preheater (1958), rotor rotary preheater (1964), flue gas preheater (1996) and Quater-sector air preheater (2003) were all born in SG. The manufacturing methods such as double channel seal design scheme (1979), wave shape research of heat transfer element and flow Production process of corrugated plate (1976) were all initiated in China. So far, nearly 2000 preheaters have been manufactured, accounting for 45% of the domestic market.

With the continuous expansion of domestic thermal power installation scale and the rapid development of unit level to large-scale direction, SG successively imported technology from American AI stom preheater company, the most advanced preheater manufacturer abroad, in 1981 and 2001. Alstom preheater company has three branches in the United States, Japan and Germany. Since 1923, Alstom has obtained Ljungstrom Product manufacturing license from Sweden. At present, the three companies have manufactured more than 15000 rotary air preheaters (including more than 8000 in the United States). The introduction of technology has greatly improved the technical level of SG, making SG the largest preheater design and manufacturing company in the world since 2002, and has become the largest preheater manufacturer in the world for many consecutive years.

In terms of air leakage control, No.7 unit of Jianbi Power Plant was put into operation in 1979. For the first time in China, the air leakage rate of large-diameter preheater was controlled below 6% (without hot end gap tracking system), and multi-channel seal and welding static seal were all pioneers in China (since 1979). In recent years, with the use of various new technologies, the air leakage rate index of preheater has been greatly reduced. For nearly 200 preheaters of 60 ~ 1000MW units put into operation in recent 10 years, the air leakage rate is mostly controlled at the level of 3.5% ~ 5%. In an overhaul period, the air leakage rate increases by no more than 2%, which is not inferior to some preheaters without clearance tracking system. The 300MW CFB Unit put into operation in 2005 uses four compartment air preheater, and the air leakage rate is controlled at about 6% (the pressure head of primary air is 30KPa, the pressure head of secondary air is 15kpa).

The sealing system adopts the structure of independent rigid sealing plate, which makes the overhaul of the sealing plate of the preheater not need to carry out the complex flatness alignment and leveling work of the sealing plate in the boiler shutdown stage like other preheaters (i.e. non adjustable design or VN type) which integrates the sealing plate and the shell. Flexible transmission system design makes the preheater work reliably. The service life of the preheater is more than 30 years (SG put into operation before 1978, more than 200 sets of Products have been used for more than 30 years).

As for the small preheater, the gap tracking system of preheater is relatively small, and its effect is limited. Therefore, the system is phased out after adopting double channel sealing technology. At present, the hot end gap tracking system is basically cancelled for the preheater with diameter less than 12m. For large-scale preheater, the thermal deformation of preheater rotor is very large (proportional to the square of rotor diameter). For 1000MW unit, the sealing plate can track the rotor deformation range of more than 55mm, and the air leakage rate can be reduced from more than 7% to about 3.5%. The device can reduce the power consumption of the fan by millions of yuan every year, with excellent cost performance. In the past, the main reason for the poor operation of the device was that the electrical components used in the sensor could not adapt to the high temperature conditions and failed prematurely. In recent years, this problem has been fundamentally solved, such as the elimination of eddy current sensors, the use of flexible contact sensors with mechanical signal amplification device, and the use of flue gas temperature to control the position of sector plate (without sensor), etc The operation rate of the gap tracking system is close to 100%, and the maintenance period is more than 3 years.

Through 50 years of development, SG has the design and manufacturing capacity of a full range of rotary air preheaters with a diameter of 20m. In the aspect of basic R & D, SG cooperated with Alstom R & D Center Laboratory of USA and Power Engineering Laboratory of Shanghai Jiaotong University, and achieved obvious results in performance test of new heat transfer elements, stress analysis of large components, selection of appropriate anti-corrosion scheme, etc., and developed several new Products suitable for Chinese fuel characteristics and use characteristics, so as to provide users with high-quality, reliable and fast in time The company has laid a solid foundation for its spare parts and Products.

 

2. Main parameters

The rotary air preheater is a standardized series design, and its main interface dimensions are shown in Figure 3-11 (three compartment, 50 ° primary air bin angle, VI type). For the air preheater used for transformation. The interface size can be adjusted according to the actual situation.

See table 3-2 for the corresponding symbol size in Figure 3-11 (the actual design drawing shall prevail if the specific project size may be different from this table).

Interface dimension of SMR type tri-sectionp preheater with primary air bin angle (mm)
Model A B C D E G J K M N P
24.5 1969 1219 6375 4559 1207 1067 914 3950 1059 3950 1143
25 2121 1219 6680 4712 1359 1168 914 4100 1100 4100 1143
25.5 2324 1219 7087 4915 1562 1321 914 4300 1154 4300 1143
26 2477 1219 7391 5067 1715 1422 914 4460 1194 4460 1143
26.5 2680 1219 7798 5271 1918 1524 914 4660 1248 4660 1219
27 2870 1219 8179 5461 2108 1651 914 4850 1300 4850 1372
27.5 3048 1219 8534 5639 2286 1778 914 5030 1346 5030 1372
28 3264 1219 8966 5855 2502 1905 914 5250 1405 5250 1372
28.5 3251 1613 9728 6541 2578 1600 1219 5630 1508 5630 1473
29 3442 1613 10109 6731 2769 1727 1219 5820 1559 5820 1473
29.5 3670 1613 10566 6960 2997 1905 1219 6050 1619 6050 1473
30 3874 1613 10973 7010 3200 2057 1219 6250 1675 6250 1473
30.5 4140 1613 11506 7430 3467 2235 1219 6520 1746 6520 1651
31 4394 1613 12014 7684 3721 2413 1219 6770 1815 6770 1651
31.5 4661 1613 12548 7950 3988 2616 1219 7040 1886 7040 1727
32 4915 1613 13056 8204 4242 2794 1219 7290 1954 7290 1727
32.5 5131 1765 13792 8573 4426 2896 1422 7660 2053 7660 1981
33 5461 1765 14453 8903 4756 3150 1422 8000 2143 8000 1981
33.5 5791 1765 15113 9233 5086 3378 1422 8360 2240 8360 2083
34 6109 1765 15748 9550 5404 3632 1422 8730 2338 8730 2083
34.5 6414 1905 16637 9995 5683 3810 1422 9170 2457 9170 2210
35 6795 1905 17399 10376 6064 4089 1422 9600 2573 9600 2286
35.5 7176 1905 18161 10757 6445 4343 1422 10020 2685 10020 2286
36 7595 1905 19000 11176 6864 4648 1422 10480 2807 10480 2286

The shell height dimension R is related to the total height of heat transfer elements and rotor diameter, which is usually the total height of heat transfer elements plus 0.7 ~ 0.9m; the height dimension of cold end connecting plate is related to the weight of rotor, which is generally 1.80 ~ 2.15m for 300MW units, 2.15 ~ 2.80M for 600MW units and 3.0 ~ 3.4m for 1000MW units.

 

3. Design and selection

3.1. Selection calculation

The type selection of air preheater is completed by computer program, which uses numerical calculation method to accurately calculate temperature field data, resistance data and air leakage data of metal and fluid in preheater rotor. The heat transfer and resistance calculation parameters are from the data provided by the laboratory. The selection of preheater diameter is based on the parameters of exhaust gas or hot air temperature, allowable maximum resistance, etc. The type and configuration of heat transfer elements are determined according to the analysis data of fuel and ash

3.2. Parameters required for model selection

If the preheater and boiler required by the user are supplied by the factory, there is no need to provide a special type selection parameter table for the preheater, and the boiler calculation process will calculate the preheater parameters at the same time; if the air preheater is used for transformation, independent purchase or non boiler equipment, the basic selection parameters shall be provided according to the contents in table 3-3 (the smoke and air flow value shall be provided according to the total amount of one unit).

Table 3-3 basic parameters of rotary air preheater selection

Item Content Bi-section Tri-section Quarter-Section Remarks
Peripheral parameters Site altitude of 0m or atmospheric pressurem,Mpa) required required required
Number of heat exchangers required (Unit) required required required
Layout (indoor / outdoor) required required required
Arrangement direction of main shaft required required required Vertical or horizontal
Smoke air flow direction required required required Or hot end position of heat exchanger
Is a hot end gap tracking device required With/without With/without With/without The preheater with diameter more than 12m is required by default
Average ambient temperature and variation range(℃) required required required
Average air humidity and variation range% required required required
Air or secondary air inlet heating mode required required required Heater or hot air recirculation
Heating mode of primary air inlet If with If with Generally not required
Fuel or flue gas composition parameters Fuel industry analysis data required required required
Fuel element analysis data required required required
Fuel consumptiont/h see remarks see remarks see remarks If there is smoke, air flow can be saved
Excess air coefficient at flue gas inlet see remarks see remarks see remarks If there is smoke composition, it can be saved
Excess air coefficient at outlet see remarks see remarks see remarks If there is hot air flow, it can be saved
Ash composition analysis data (%) required required required Oil gas fuel is not required
Ash flow and specific heat capacity see remarks see remarks see remarks Only required for high ash coal
Input and required smoke air flow 
It is required for every different working condition
Flue gas flow into heat exchanger (kg / s) required required required
Required hot air or hot secondary air flow (kg / s) required required required It is the amount of hot air at the outlet of heat exchanger with bi-section
Total primary air flow required (kg / s) required required Flow after mixing in front of pulverizer
Input and required temperature parameters
It is required for every different working condition
Flue gas inlet temperature () required required required 430
Air or secondary air inlet temperature () required required required
Primary air inlet temperature () required required
Required temperature of primary air before pulverizer () required
Input pressure and allowable resistance
It is required for every different working condition
Flue gas inlet pressure (kPa) required required required
Pressure of hot air or hot secondary air (kPa) required required required
Primary air pressure at heat exchanger outlet (kPa) required required
Performance guarantee requirements The default is MCR condition Allowable maximum air leakage rate required required required The default value is less than 6% within 1 year and 8% within 4 years
Allowable maximum smoke or air resistance (kPa) required required required By default, the flue gas resistance is less than 1.3kpa
Required exhaust gas temperature or minimum hot air / hot primary air temperature () required required required Select one item, and the smoke exhaust temperature should be indicated as after or before air leakage correction


3.3. System supporting conditions

3.3.1. Power supply conditions. The parameters of AC / DC, voltage level, frequency and phase shall be informed.

3.3.2. Instrument air source. The parameters such as purity, pressure and available air volume should be informed.

3.3.3. Soot blowing steam. The parameters such as temperature, pressure and available gas volume should be informed. The general requirements are 1 ~ 1.4mpa, 320 ~ 350 ℃.

3.3.4. Dynamic compressed air. If air motor is required, air source with pressure of 0.6 ~ - 0.8MPa should be provided.

3.3.5. Fire water. The required pressure is 0.6 ~ 0.8MPa, and the water is supplied from the water supply circuit of the fire protection system according to the design requirements

3.3.6. Cooling water. For bearing lubricating oil station, the required pressure is 0.2 ~ 0.5mp'a, the water quality is ordinary tap water or clean neutral inDustrial water, and the water quantity is according to the design requirements.

3.4. Special supply requirements

3.4.1. Whether turning air motor is required, and whether DC motor or air motor is required for auxiliary drive motor.

3.4.2. Whether enamel surface material is required for cold end heat transfer elements, and whether there are special requirements for thickness and material of heat transfer elements at hot end.

3.4.3. Service life requirements of heat transfer element, bearing and reducer.

3.4.4. Whether hot end soot blower is required (generally only for lignite fuel).

3.4.5. Spare parts requirements for random operation within 3 years.

3.4.6. Whether the lubricating oil station needs double pump system.

3.4.7. Whether there are special size requirements for the interface of smoke and air Duct.

3.4.8. Whether there are special material requirements for structural parts of preheater.

3.4.9. Whether it is necessary to set up the local transmission device control box, whether the soot blowing program control needs the additional control equipment such as the independent control system (generally the boiler program control), the local control box of the lubricating oil station (generally dxcs control), and whether additional temperature and pressure measuring instruments are needed.

3.4.10. The default design and supply interface of preheater is the connection flange of flue gas Duct and body shell. The local cable is the primary measuring element and local connecting cable in the system, excluding the cable between DCS and DCS. If necessary, it shall be specified.

3.4.11. Specific requirements for painting and thermal insulation.

3.4.12. Delivery place requirements.

3.4.13. Format and language requirements of instructions and drawings.

3.4.14. Whether on-site measurement is required (for modification project date).

3.4.15. The rotation direction of the preheater is reversed by default, that is, the secondary air is heated first, and the daily value is flue gas → secondary air → primary air → flue gas diversion.

 

4. Selection examples

Table 3-4 and table 3-5 show the design structural parameters and type selection results of typical three compartment air preheaters for 300, 600 and 1000 MW boiler units, while table 3-6 shows the material configuration of typical rotary air preheaters (the engineering differences are large, and the values are for reference only).

Table 3-4 design performance parameters of typical three compartment air preheater for 300, 600 and 100wv boiler units

No. Item 300MW 600MW 1000MW
1 Air flow at primary air inlet (kg/s) 72.87 121.9 158.71
2 Air flow at secondary air inlet (kg/s) 212.97 466.99 724.39
3 Inlet flue flow (kg/s) 372 680.72 1021.5
4 Air flow at primary air outlet (kg/s) 55.74 94.56 112.22
5 Air flow at secondary air outlet (kg/s) 209.06 461.95 716.2
6 Outlet flue flow (kg/s) 393.04 713.1 1076.18
7 Primary air flow temperature adjusted(kg/s) 6.95 33.21 83.92
8 Primary air flow while entering mill(kg/s) 62.69 127.77 196.13
9 Primary air inlet temperature() 28 27 27
10 Secondary air inlet temperature() 23 23 24
11 Flue inlet temperature () 361 376 373
12 Primary air outlet temperature () 334 328 337
13 Secondary air outlet temperature() 343 342 345
14 Flue outlet temperature (uncorrected, ) 149 132 132
15 Flue outlet temperature(corrected,℃) 143 128 127
16 Air temperature entering mill() 302 251 206
17 Flow resistance of primary air (kPa) 0.56 0.47 0.4
18 Flow resistance of secondary air (kPa) 0.61 0.85 1.01
19 Flow resistance of flue gas (kPa) 1.02 1.03 1.18

Table 3-5 Typical results of type selection of 3-compartment and 3-compartment air preheater for 1000V boiler

No. Item 300MW 600MW 1008MW
1 Preheater model 2-29VI(T) 2-32(T) 2-34VI(T)
2 Preheater rotor diameter (m) 10.33 13.5 16.4
3 Boiler SCR device Without Without Without
4 Rotate direction Flue gas Secondary air Flue gas Secondary air Flue gas Primary air
5 General height of the heating elements(mm) 1980 2080 2300
6 Full loading of each rotor (t) 2X215 2X368 2X582
7 Gross weight of each preheater (t) 2X314 2X516 2X798
8 Heating exchange area of each preheater (m2) 2X51225 2X95030 2X148230
9 Air leakage gap adjustment system Without With
10 No.s of transmission motor Double motors Double motors + Air motor

Table 3-6 material configuration of typical rotary air preheater

No. Parts Material
1 Heating element of hot layer and interm. Layer Cold rolled low carbon steel sheet SPCC
2 Heating element of cold layer CortenNSI
3 Anti-corruption heating element of cold layer The base material is low carbon steel, and each side is coated with 0.15 ~ 0.22mm acid resistant enamel
4 Rotor, shell parts Carbon steelflue preheater use Corten or NSI
5 Central cylinder Heat resistant steel 20 or Q345
6 Guiding shaft Medium strength alloy steel, forgings
7 Ring belt pin, transmission gear Medium strength wear resistant steel, surface nitriding heat treatment
8 Bearing support Medium strength alloy steel, forging (no cast iron material)
9 Rotor sealing Select corrosion resistant steel and stainless steel as required
10 Geared motor Forged alloy steel (without cast iron material)

 

5. Scope of supply and order requirements

5.1. Typical scope of supply

5.1.1. Supply interface position agreement: take the flue gas and air inlet and outlet flange of air preheater as the boundary (screw holes can be opened as required or welded with the expansion joint of flue gas Duct); the interface of cleaning, fire fighting and cooling water is the main body; the pipe flange is located about 300m outside the local shell circle of air preheater; the electrical system interface is the local control cabinet or junction box, and the motor is connected to The connection terminal and soot blower interface is the population flange of steam inlet valve. The position of each interface is generally shown on the PID diagram of the equipment.

5.1.2. Preheater body components: including rotor central shaft, rotor moDule and connecting pieces, transmission shroud (without central shaft drive), heat transfer element support bracket, upper and lower intermediate beams, preheater shell and support, secondary air center part (used to separate primary and secondary air), transition angle of flue gas Duct connection, strengthening support pipe and anti-wear parts, etc.

5.1.3. Sealing plate and static seal: sector plate and static seal on both sides, axial sealing plate and static seal on both sides, upper and lower sealing discs of central shaft, etc.

5.1.4. Free expansion guide device: including main and auxiliary support expansion device and limit block.

5.1.5. Sealing system: including radial, axial, circumferential and central sealing plates, mounting fasteners, pressing plates, etc.

5.1.6. Heat transfer element: including heat transfer element package of hot section, medium temperature section and cold section.

5.1.7. Transmission device of preheater: including main motor, auxiliary motor, turning motor (optional), main reducer, auxiliary reducer, hydraulic coupler, overrunning clutch, transmission gear and fixed assembly (without central shaft drive), adjusting gasket and connecting bolt, and local control cabinet (optional).

5.1.8. Fire detection equipment of preheater: including temperature acquisition equipment (infrared probe or thermocouple, choose one), probe installation equipment, probe driving equipment (only for infrared probe), local control cabinet, connecting cable of each sub part (excluding external protection iron pipe), etc.

5.1.9. Hot end automatic air leakage control system: only large air preheater configuration, including sector plate up and down adjustment drive device, local junction box, rotor position sensor, flue gas population temperature measurement thermocouple, local control cabinet, connecting cable of each sub component (excluding external protection iron pipe), etc.

5.1.10. Rotor stop alarm equipment: including induction hoop, signal inDuctive proximity switch, local junction box, etc.

5.1.11. Bearing and lubrication equipment of preheater: guide bearing and bearing pedestal, supporting bearing and bearing pedestal, bearing lubricating oil station and local junction box, etc.

5.1.12. Soot blowing equipment: cold end soot blower, hot end soot blower (lignite fuel, flue gas air preheater, preheater for SCR boiler are recommended to be installed, other situations do not need), generally single medium of steam, flue gas air preheater and preheater for SCR boiler are steam and high pressure water, local control cabinet, etc.

5.1.13. Fire fighting and cleaning equipment: including fire pipe network and nozzle above rotor, multi nozzle cleaning pipe and water source filter, etc.

5.1.14. Access door and observation door hole: inspection manhole door, hot end operation observation window, cold section operation observation window (preheater equipment with internal lighting), heat transfer element and shroud installation door, etc.

5.1.15. Body maintenance and repair platform: including guide bearing, support bearing maintenance platform and approach escalator, transmission device maintenance platform and approach escalator, soot blower maintenance platform, etc. (generally, it belongs to the scope of boiler supply with boiler frame connection platform).

5.1.16. Special tools: including bearing assembly and disassembly tools, rotor jacking station, moDule lifting tools, cold section heat transfer element package pulling tool, sealing plate installation ruler, circumferential sealing surface on-site processing tools, etc.

5.1.17. Thermal insulation and paint: including primer, heat preservation claw nail, etc. The exposed metal topcoat, insulation cotton and guard board are generally consistent with the boiler body style and are provided by the boiler supplier.

5.1.18. Local measuring instrument: including bearing oil temperature measuring thermal resistance, lubricating oil station temperature gauge, pressure gauge, etc.

5.1.19. Random spare parts: including 2% of various sealing plates, packing and other sealing fillers.

5.1.20. Name plate and identification.

5.2. General specifications

5.2.1. Overview:

5.2.1.1. Purpose. Rotary air preheater is mainly used to recover the waste heat of flue gas from boilers and other equipment. It is a heat recovery equipment for heating air and other media required for combustion. It takes heat transfer elements in the rotor as the carrier to continuously recover heat through continuous rotation.

5.2.1.2. Basic qualification requirements of suppliers. Must have long-term design and manufacturing experience, and have similar equipment more than 5 years of use performance. The type selection of air preheater should consider the equipment investment and operation cost, and select the best Product model.

5.2.1.3. Document requirements. The procurement unit of air preheater usually provides the bidding document according to the basic requirements of the project, while the supplier provides the bidding document according to the requirements of the bidding document. The performance and structural parameters of the equipment, the scope of supply, and the differences in the requirements of the bidding document shall be indicated in the tender document.

5.2.2. Selection and arrangement. In principle, the layout and structure of air preheater shall be subject to the requirements of the bid inviting party, such as vertical or horizontal, downward or upward direction of flue gas, and number of compartments. If the bidding document is not clear, the supplier shall provide the most suitable proposal.

5.2.3. Heat transfer performance. The heat transfer performance requirements are as follows:

5.2.3.1. Controlled by the performance parameters of heat transfer elements used, the supplier shall adopt the varieties that conform to the characteristics and variation range of the user's fuel. However, considering the operation indexes such as resistance and wear, it is not suitable to adopt the wave form of single heat transfer element with good heat transfer index.

5.2.3.2. The source of various performance parameters of heat transfer elements shall be the data of professional heat transfer element measurement department or laboratory, preferably the data of professional development department, and have been verified by actual operation for no less than 3 years.

5.2.3.3. Performance data shall cover multiple operating conditions and fuel types. The computer program used to provide performance calculation should have a certain margin to ensure that the output temperature parameters do not change significantly after the heat transfer element is used for a certain stage.

5.2.4. Resistance performance. As with the heat exchange index, the resistance coefficient should be obtained from the professional laboratory and real machine verification. The computer program used to provide resistance calculation should also have a certain margin, and the supplier should provide the maximum flow resistance guarantee value.

5.2.5. Wear resistance. It is necessary to limit the average velocity of flue gas to prolong the wear time of heat transfer elements in hot section. The supplier shall provide life guarantee data.

5.2.6. Corrosion resistance. For the fuel with low exhaust gas temperature and high sulfur content, the thickness and material of cold section heat transfer elements should be specified, and the supplier should also provide life guarantee data. The supplier shall also provide the heating temperature required under various working conditions under the low temperature medium inlet heating mode recommended by the user.

5.2.7. Air leakage guarantee data. The supplier shall provide the performance data under the following maximum continuous operation conditions:

5.2.7.1. Guarantee value of air leakage rate at the initial stage of operation.

5.2.7.2. Guarantee value of air leakage rate after 4 years of continuous operation.

5.2.7.3. Guarantee value of primary air leakage rate.

5.2.8. Reliability and guaranteed life. The annual reliable and continuous operation time of the equipment and the times of shutdown caused by air preheater accident shall be put forward. The overall service life of air preheater is 30 years, that of bearing and reducer is 10 years, that of sealing plate is 4 years, that of heat transfer element in hot section and middle temperature section is not less than 80000 h, and that of heat transfer element in cold section is not less than 50000 H

5.2.9. Basic requirements for design structure:

5.2.9.1. Sealing material, heat transfer element material and thickness, rotor material, etc. shall be listed in detail in the document.

5.2.9.2. It is necessary to explain the temperature detection method and monitoring position adopted for fire alarm. The fire protection system should cover all the upper surfaces of rotors, and large caliber wide angle nozzles should be used. The fire water supply system can not be linked with the fire detection system of the air preheater, so as to avoid unnecessary equipment damage and shutdown Due to water spraying into the air preheater During the false alarm or manual controllable stage.

5.2.9.3. Thermal deformation data and fulcrum load value of equipment operation shall be provided.

5.2.9.4. It is necessary to determine whether the hot end clearance tracking system is configured. The system should have the ability of automatic exit in case of accident and adopt the most concise design method.

5.2.9.5. The configuration mode and start-up sequence of transmission device shall be described in detail.

5.2.9.6. Local electrical control system shall be minimized to reduce maintenance. Transmission device and local control cabinet of lubricating oil station shall not be set as far as possible, and corresponding control functions shall be completed by DCs.

5.2.10. Implement the standard requirements. The material requirement standard is the national standard of the country where the equipment is used or the general international standards such as JIS, ASME and en, and the performance test standard is recognized by the inDustry such as GB, ASME and JIS.

5.3. Special specifications

5.3.1. Waveform and plate thickness of heat transfer elements. In view of the influence of the wave shape of the heat transfer element on the operation resistance, heat exchange, wear and other indicators, the waveform of enhanced heat exchange type should be adopted in the hot section of the air preheater, and the waveform that is convenient for soot blowing and dredging should be adopted in the cold section; The thickness of heat transfer elements shall meet the service life requirements of the equipment: for the preheater equipped with SCR boiler, the height of the heat transfer element in the cold section layer shall be within all SCR operation load ranges, and all ammonium bisulfate deposits shall be deposited inside the cold section layer; for the use of high sulfur coal (with flow rate greater than 1.5%), enamel surface shall be used for the cold section layer heat transfer element.

5.3.2 design form of rotor structure. The rotor of large air preheater should be made into moDule structure to facilitate on-site installation, instead of the design form that needs to be assembled on the platform on site; the connection with the central shaft should be made with pin shaft as far as possible to improve the installation speed.

5.3.3. Adjustment form of sealing plate. The sealing plate shall be designed separately from the shell of air preheater to improve its adjustable capacity; the number of regulating points shall not be too many to speed up the operation and maintenance; the rigidity of the sealing plate shall ensure the anti deformation ability of the sealing surface, so as to avoid re leveling the sealing surface in the maintenance stage.

5.3.4. Sealing design scheme:

5.3.4.1. The rotor seal shall be at least designed as a complete double channel, i.e. the sealing plate shall seal more than 2 rotor cells; for CFB boiler with high pressure head, the four compartment preheater shall be used, and the seal between flue gas and air shall be three.

5.3.4.2. Radial seal shall be set between upper and lower radial diaphragms and sector plates of rotor.

5.3.4.3. Axial seal shall be set between outer end of radial diaphragm and axial sealing plate.

5.3.4.4. Bypass seals shall be set between the upper and lower end faces of the rotor and the flange of the rotor shell, and the cold end bypass seal shall be arranged on the rotor end face to form a self sealing pair by using the thermal deformation of the rotor to avoid air winding to the side of the rotor.

5.3.4.5. The central seal shall be set between the central shaft and the rotor, up and down.

5.3.4.6. A tight air seal shall be set at the position where the central shaft extends out of the shell to avoid ash leakage.

5.3.4.7. The expansion gap at the tail of sealing plate shall be provided with sealing strip.

5.3.4.8. The seal shall be designed to be connected with the rotor bolt to facilitate adjustment and replacement.

5.3.4.9. The thickness of the sealing plate should not be less than 2.5mm. Different grades of corrosion-resistant materials should be selected according to the working conditions.

5.3.4.10. The hot end gap tracking system should be adopted for large preheater to minimize air leakage.

5.3.5. Transmission device design mode:

5.3.5.1. The preheater shall be designed with main drive motor and auxiliary drive motor at least, which can make the air preheater operate with load.

5.3.5.2. For large preheater, it is necessary to set low-speed pneumatic motor for turning adjustment stage.

5.3.5.3. Each motor shall be interlocked with each other; the air supply pipeline of pneumatic motor shall be equipped with solenoid valve, which can automatically put the air motor into operation after power failure of motor.

5.3.5.4. Hydraulic coupler or variable frequency starting mode is adopted as soft start protection mode.

5.3.5.5. When the main motor is running, other motors and air motors shall be able to be disconnected without following.

5.3.5.6. Rotor bearing. The guide bearing adopts double row radial spherical roller bearing, and the supporting bearing adopts spherical roller thrust bearing; the bearing shall be able to absorb a small amount of rotor deflection load, and its service life shall not be less than 100000 H.

5.3.5.7. Bearing cooling and filtering system. Water cooling sleeve of bearing pedestal or independent lubricating oil station shall be equipped to cool lubricating oil. The lubricating oil station can also filter the lubricating oil. The local temperature and differential pressure before and after the filter should be set in the station, and the start-up and shutdown of the filter should be controlled by DCs according to the bearing oil temperature; the filter should be in the form of double barrel to ensure that the filter element can be cleaned or replaced without shutdown.

5.3.5.8. Shutdown alarm system. The rotor speed numerical signal shall be provided for gap tracking system and DCS; the alarm shall be set by DCs, and the speed accuracy shall be 0.03r/min. The signal needs to adopt three take two mode, and sets the local junction box.

5.3.5.9. Clearance tracking system. Each sector plate at the hot end shall be equipped with a set of lifting drive device, and the rotor position sensor or flue gas temperature shall be used to control the running position of the sector plate. The whole system shall operate automatically, and at least the automatic exit protection function shall be set under the conditions of rotor stop, motor overload of lifting device and sensor failure. The working state and alarm signal of the system can be sent to DCS and can communicate with DCS.

5.3.5.10. Fire detection system. Infrared probe or thermocouple probe is used to measure the change gradient of metal temperature or air outlet temperature of rotor cold section, and the stage signals of rapid temperature change of normal preheater such as boiler soot blowing, using air heater or hot air recirculation can be eliminated. Local operation display screen is required to display the fault point and track the 12h (adjustable) temperature change trend curve of the measuring point, and the alarm signal can be displayed by DCS.

5.3.5.11. Soot blowing system. The soot blowing system includes soot blower body, steam pressure regulating valve and other parts, which are divided into semi telescopic form (conventional configuration) and full telescopic form (special configuration). For flue gas air preheater and SCR boiler preheater, steam and high-pressure water should be used. Among them, high-pressure water medium is used to flush heat transfer elements, high-pressure water pump is matched by soot blower, and local operation cabinet is set on site. The control of conventional soot blower is controlled by boiler soot blowing program control.