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HBC rotary air preheater

key word:Heat exchange element

Category:


Product description

HBC rotary air preheater

 

1. Introduction

1.1. Purpose

Rotary air preheater is an important heat recovery equipment for power plant boilers. It absorbs the waste heat from boiler flue gas to heat the air entering the boiler. It can reduce the temperature of flue gas in the boiler and increase the temperature of the odorous combustion supporting air entering the boiler, so as to ensure that the power plant boiler can obtain higher combustion efficiency.

1.2. Model

33.5-V(H) I (B/T/Q/C)-2000-SMR(QMR)

33.5 -------- rotor diameter serial number of air preheater

V (H) ---- V indicates that the air preheater is vertical, and H is horizontal

I -------- the heat transfer between flue gas and air is counter current

B / T / Q / C -------- B stands for two compartment air preheater, T for three compartment air preheater, Q for four compartment air preheater, and C for concentric circle air preheater,

2000 -- height of heat exchange element (mm)

SMR (QMR) ---- SMR stands for half mode structure and QMR stands for full mode structure

Description: each air preheater rotor diameter serial number corresponds to different rotor diameter. The larger the model is, the larger the rotor diameter is, and the larger the radial dimension of air preheater is. Generally, the model of air preheater is 7 ~ 36, and the diameter of rotor is 1.32 ~ 19.82m.

The height of heat exchange element of air preheater is generally 50 mm.

The model of air preheater is determined according to the flue gas and air performance parameters of the boiler provided by the user.

1.3. Structural features

1.3.1. General layout. The arrangement of preheater is shown in Fig. 2-1. The flue gas from the boiler economizer enters the air preheater for heat exchange and cooling through the flue, and then enters the dust collector device. After dust removal, the flue gas enters the chimney and is discharged into the atmosphere. Generally speaking, the temperature of flue gas decreases from 370 ℃ to 130 ℃ after entering the air preheater. The air enters the air preheater in two ways. After heat exchange through the air preheater, the temperature of primary air rises from 20 ℃ to about 310 ℃. After mixing with cold air, it enters the pulverizer to dry the pulverized coal, and the pulverized coal is brought into the furnace through the burner for combustion. After heat exchange by air preheater, the temperature of secondary air rises from 20 ℃ to 330 ℃, and then enters the furnace to support combustion.

1.3.2. Working principle. The rotary air preheater absorbs heat from flue gas, and then transfers heat to cold air through continuously rotating heat transfer elements composed of special shaped metal plates.

Thousands of high-efficiency heat transfer elements are closely placed in the fan-shaped bin, which is radially separated by a cylindrical shell called the rotor. Outside the rotor, there is a rotor shell. Both ends of the rotor shell are connected with the flue gas duct. The rotary air preheater is equipped with radial seal and bypass seal to form half of flue gas and the other half of circulating air. When the rotor rotates slowly, the flue gas and air flow through the heat transfer element alternately. The heat transfer element absorbs heat from the hot flue gas and reduces the exhaust gas temperature. Then this part of heat transfer element is washed by cold air flow and releases the stored heat, which greatly increases the air temperature, so as to reduce the exhaust gas temperature and increase the air temperature.

1.3.3. Structural characteristics of main components. The rotary air preheater adopts the mode structure rotor, double (three) seal, three (two, four) compartment type, the main shaft is vertically arranged, and the air and flue gas exchange heat in the reverse flow mode. The rotary air preheater is mainly composed of rotor, rotor sealing system, central cylinder and end shaft, rotor shell, upper and lower connecting plates, heat transfer elements, upper and lower bearings and driving device.

1.3.3.1 the rotor inherits the mode structure scheme which has been popular with users for many years. The new structure scheme has no overlapping radial diaphragms. The rotor flow area is increased by 2% and the dead weight is reduced by about 8%. All heat transfer elements are replaced on the side. The rotor consists of nine sector silos manufactured by double bin workshop and nine sector silos installed on site. Fig. 2-2 shows the installation diagram of sector bin.

The advantages of the model rotor are as follows:

① The fan-shaped bin only needs to be connected with the center simple end plate at the installation site, which is not only quick to install, but also easy to guarantee the quality;

② It is difficult to control the center welding and radial welding;

③ Using the new model fan-shaped bin design scheme, the rotor self weight is reduced, the rotor flow area is increased, and the flow resistance is decreased;

④ On site adjustment and hoisting use of special tools, speed up;

⑤ Most of the heat transfer elements can be transported to the site in the mode fan-shaped warehouse, which has the advantages of low cost and small stacking volume.

The air preheater rotor designed by the above scheme can be installed in a few days, which saves 70% of the installation time compared with the field splicing design scheme. In addition, there is no need to use platform assembly on site, so it can save a lot of stacking site and assembly costs. Recently, HBC has developed a 48 compartment rotor on the basis of imported technology, which can meet the structural requirements of three seal system. Among them, 36 mode sector silos are completed by the manufacturer, and 12 mode sector silos are assembled on site, which further reduces the installation workload on site.

1.3.3.2. The rotor sealing system of rotary air preheater is designed according to the thermal deformation of rotor, which includes central cylinder seal, radial seal, axial seal, bypass seal and static seal. Among them, radial seal and axial seal adopt double seal structure or three seal structure. Figure 2-3 shows the radial and axial double seal structure. Multiple seals have great effect on reducing direct air leakage of air preheater, which can be seen from the following calculation formula of direct air leakage.

The calculation formula of direct air leakage area Ad1 is

Ad1=0.5KAρΔp/Z

K --- resistance coefficient;

A --- leakage area;

ρ --- air density;

Δ P is the pressure difference between flue gas and air;

Z -------- number of seal pieces.

1.3.3.3. Reducing the air leakage of rotary air preheater and keeping the air leakage rate stable in a certain period are the design characteristics and development direction of HBC rotary air preheater. In order to control the air leakage rate of the preheater for a long time and reduce the possible air leakage channels behind the fan-shaped plate and axial sealing plate of the preheater, the scheme of bilateral arrangement and welding seal is adopted in the static sealing structure of the preheater, as shown in Fig. 2-4. When the preheater is equipped with air leakage control system, labyrinth seal is used on both sides of the hot end sector plate, and the expansion joint static seal is used on both sides of the cold end sector plate and axial seal plate; when the preheater is not equipped with the air leakage control system, the expansion joint static seal is used on both sides of the hot end sector plate, cold end sector plate and axial seal plate.

1.3.3.4. The rotary air preheater is supported by reliable thrust radial roller bearing, and the reliable double row radial spherical roller bearing is used as the guide bearing for easy replacement. In addition, this kind of bearing adopts reliable oil bath water-cooling lubrication, does not need to be equipped with cooling system, and ensures no oil leakage. In order to prevent dust and water from entering, the bearing box (cover) adopts reliable sealing device, and is easy to repair and maintain.

1.3.3.5. Heat transfer element is the core part of rotary air preheater. The selection of heat transfer element plate type, material, thickness and manufacturing quality will have a significant impact on the operation performance of rotary air preheater. Table 2-1 shows the plate type and application range of heat transfer element. HBC imported several kinds of heat transfer element plate type and calculation program from American preheater company, which can analyze and calculate different furnace types and coal types, and obtain the best thermal performance parameters through different heat transfer elements collocation. All the heat transfer element boxes are made into small components. During maintenance, the heat transfer element boxes are pulled out from the access door of the rotor housing, which is very convenient for installation and replacement.

Table 2-1 plate type and application range of heat transfer elements

No. Pattern Suit fuel Characters
1 DUN
FNC
For not easy slagging (acid ash) coal (hot section heat exchange surface), oil or gas fuel (all heat exchange surfaces) Compared with DU element, the cross flow channel can enhance 10% heat transfer, with the same resistance coefficient and save 8% ~ 10% material
2 DN3
DL3
It is used for acid ash coal, alkaline ash coal (large ash mass) and high ash coal (all heat exchange surfaces), oil and gas fuel (all heat exchange surfaces) There are many dust removing straight channels, which can greatly improve the ash blocking of components;the heat transfer and resistance characteristics are the same as those of DU
3 DU3
UNU
For light slagging ash coal (all heat exchange surfaces), oil and gas fuel (all heat exchange surfaces) The heat transfer and resistance characteristics are the same as DU, which can save 5% mass
4 NF3.5
NF6.0
Coal fuel, long and thin slag or high moisture coal (all heat exchange surfaces) and other coal cold section layout Compared with NF6, NF3.5 has higher density and stronger heat transfer. The vertical closed channel is easy to be penetrated by soot blowing, but the heat transfer effect is not as good as that of DU
5 DFC All fuel High heat transfer, anti ash blocking, easy cleaning, mainly used in denitration preheater

1.3.3.6. The rotor is driven by the central transmission device. Each transmission device includes two electric drive devices, one main drive motor and one auxiliary drive motor. The main shaft drive motor is standby for each other. The drive system is equipped with frequency conversion control system, which can realize the soft start of rotary air preheater, and control the starting, purging and normal operation of rotary air preheater. If the main motor is out of service, the auxiliary motor will automatically switch to the running state to prevent the rotor from stalling. At the same time, the rotary air preheater is also equipped with a rotor stop alarm device to track the speed change of the rotor to ensure the safe and stable operation of the rotary air preheater.

1.3.3.7. The rotary air preheater is equipped with steam soot blower or pulse soot blower. The denitration preheater is also equipped with high-pressure water and steam (or compressed air) dual media soot blower to ensure the normal operation of rotary air preheater and prevent condensation and soot deposition under regular soot blowing.

1.4. Product series

HBC has designed and produced nearly 1000 rotary air preheaters, and has formed a series of products supporting boiler units with different capacity levels: rotary air preheater models are 19-34.5.

 

2. Main technical parameters

The main technical parameters of rotary air preheater are shown in table 2-2.

Table 2-2 main technical parameters of rotary air preheater

Name BMCR TMCR THA 75% THA 50% THA 40% THA THO
Designing coal type Air flow at the inlet of air preheater (t/h) 1370 1310 1236 1051 789 669 1266
Secondary air flow at the outlet of air preheater (t/h) 1014.4 950.8 889 772.9 579.3 476.3 914
Air flow of primary air (mixed, t/h) 215.2 212 208.1 168.5 129.3 123.1 209.7
Temperature of the primary air at the inlet of air preheater () 28 28 28 ______ ______ ______ 28
Temperature of the secondary air at the inlet of air preheater () 23 23 23 ______ ______ ______ 23
Temperature of the flue gas at the inlet of the air preheater () 402 396 389 370 340 324 374
Flue gas at the outlet of the air preheater (air leak not considered,) 130 ______ 125 ______ ______ ______ ______
Primary air  temperature (after mixed) () 316 308 299 283 260 232 302
From the primary air to flue gas side (kPa) 10000 ______ ______ ______ ______ ______ ______
From the secondary air to flue gas side (kPa) 4500 ______ ______ ______ ______ ______ ______
Required pressure drop of the flue gas (kPa) ______ ______ ______ ______ ______ ______ ______
Pressure drop of primary air (kPa) <800 ______ <0.747 ______ <0.747 ______ ______
Pressure drop of secondary air (kPa) <800 ______ ______ ______ ______ ______ ______
Pressure drop at flue side (kPa) <1000 ______ ______ ______ ______ ______ ______
Excess air coefficient at economizer outlet 1.24 1.24 1.24 1.403 1.54 1.595 1.24
Checking coal type Air flow at the inlet of air preheater (t/h) 1346 1286 1214 1035 778 662 1247
Secondary air flow at the outlet of air preheater (t/h) 970.7 920.1 859.4 751.5 564.3 464.1 887
Air flow of primary air (mixed, t/h) 231.6 228.1 224 181.5 139.3 132.7 225.9
Temperature of the primary air at the inlet of air preheater () 28 28 28 ______ ______ ______ 28
Temperature of the secondary air at the inlet of air preheater () 23 23 23 ______ ______ ______ 23
Temperature of the flue gas at the inlet of the air preheater () 397 392 385 367 336 321 370
Flue gas at the outlet of the air preheater (air leak not considered,) ______ ______ ______ ______ ______ ______ ______
Primary air  temperature (after mixed) () 265 259 251 238 218 194 254
From the primary air to flue gas side (kPa) ______ ______ ______ ______ ______ ______ ______
From the secondary air to flue gas side (kPa) ______ ______ ______ ______ ______ ______ ______
Required pressure drop of the flue gas (kPa) ______ ______ ______ ______ ______ ______ ______
Pressure drop of primary air (kPa) ______ ______ ______ ______ ______ ______ ______
Pressure drop of secondary air (kPa) ______ ______ ______ ______ ______ ______ ______
Pressure drop at flue side (kPa) ______ ______ ______ ______ ______ ______ ______
Excess air coefficient at economizer outlet 1.22 1.22 1.22 1.383 1.52 1.575 1.22

 

3. Equipment appearance and structural dimensions

3.1. Shape of rotary air preheater (see Fig. 2-5)

3.2. Structural parameters of rotary air preheater (see table 2-3)

Table 2-3 structural data of rotary air preheater

 

Item Parameters
Model 34- VI (T) - 1800 - SMR
No.s (units) 2
Manufacture HBC
Flue gas temperature at inlet (BMCR, ) 364
Flue gas temperature at outlet (BMCR, ) 128.2 (Uncorrected)
Air temperature at inlet  (primary air / secondary air)    (BMCR, ) 29/23
Temperature of primary air at outlet (BMCR, ) 301
Temperature of secondary air at outlet (BMCR, ) 321.7
Air leakage when put into operation and after one year of operation (BRL, 100%) 6,8
Material of the heating element in hot layer (mm) Q215-AF
Depth of the heating element in hot layer (mm) 0.5
Area of the heating element in hot layer (m2) 82548/per air preheater, both sides
Height of the heating element in hot layer (mm) 1000
Material of the heating element in intermediate layer (mm) Q215-AF
Depth of the heating element in intermediate layer (mm) 0.5
Area of the heating element in intermediate layer (m2) 39070/per air preheater, both sides
Height of the heating element inintermediate layer (mm) 500
Material of the heating element in cold layer (mm) Corten steel
Depth of the heating element in cold layer (mm) 1.2
Area of the heating element in coldlayer (m2) 21019/per air preheater, both sides
Height of the heating element in cold layer (mm) 300
Is there an electronic automatic control sealing system Yes
Motor model of the electronic automatic control sealing system TDY-150
Motor No.s of the electronic automatic control sealing system (unit) 6/per boiler
Motor speed of the electronic automatic control sealing system (r/min) 60
Motor power of the electronic automatic control sealing system (kW) 0.24
Air preheater bearing lubrication and cooling type Oil bath water cooling
Rotor diameter of the air preheater (mm) 16370
Rotor height of the air preheater (m) 2.56
Rotor weight of the air preheater (t) 480
Rotor speed of the air preheater (r/min) 0.85
Driving motor model of the air preheater Y200L1-6
Driving motor No.s of the air preheater (unit) 4/per boiler
Driving motor speed of the air preheater (r/min) 970
Driving motor power of the air preheater (kW) 18.5
Driving geared motor mounting type Foot mounting
Auxiliary pneumatic motor model of the air preheater 92RA017
Auxiliary pneumatic motor No.s of the air preheater (unit) 2/per boiler
Auxiliary pneumatic motor power of the air preheater (kW) 6.08

Note: the data in the table take a project as an example.

 

4. Selection method

The selection of rotary air preheater is mainly based on the relevant design parameters of the boiler, the analysis data of coal type and ash composition, natural conditions (including ambient temperature, altitude, earthquake and wind load, etc.), and the appropriate heat transfer element plate type shall be selected to ensure that the flue gas and air resistance are within the range required by the agreement, and can reach the guaranteed value of exhaust gas temperature required in the agreement, so as to determine the rationality The model of rotary air preheater and the height of heat transfer element.

 

5. Scope of supply and ordering instructions

5.1. Scope of supply

5.1.1. General requirements. HBC provides the air preheater and all its auxiliary equipment and accessories, including the equipment and devices in the preheater supply list, accompanying spare parts and special tools, etc.

5.1.2. Scope of supply. The scope of supply of main systems and equipment is as follows, and the detailed scope of supply shall be in accordance with the contract.

5.1.2.1. Rotary air preheater body.

5.1.2.2. Rotor transmission device.

5.1.2.3. Heat transfer elements.

5.1.2.4 soot blower and local control cabinet.

5.1.2.5. Sealing system.

5.1.2.6. Local instrument and control equipment.

5.1.2.7. Spare parts and special tools.

5.2. Ordering instructions

Before ordering, technical agreement of rotary air preheater must be signed, including main technical parameters, purging steam source and method, coal and ash composition and characteristic data, project overview, natural conditions (environmental temperature, altitude, earthquake and wind load, etc.) Design parameters, operation conditions, technical conditions, performance guarantee, design manufacturing, installation and commissioning requirements, design boundary and supply scope, etc.