One. Overview
1. Structure
Bag dust remover, auxiliary systems and equipment include: import and export flue flange, dust hopper body between the flanges, bypass flue, valves, platform escalators, protection devices, automatic water cooling system, cleaning system and pre-coated gray system, hopper flow system (electric heater, pipe fittings etc the whole system), compressed air tanks, turbidity, broken bags detecting device etc, the whole dust removal device.
2. Working principle
Dusty gas enter each unit ash bucket through the draft tube. Under the guidance of ash bucket diversion system, large dust particles is directly into the hopper after the separation, the remaining dust enter into the box filtring zone with air. Through the filter bag, clean filtered air is exhausted through the housing upper, the poppet valve, exhaust duct.
In accordance with the filter conditions, dust control device close the poppet valve according to the setting procedures, when the bag reaches a certain amount of surface area. Controlling current unit offline, opening the electromagnetic pulse valve injection, and shaking off the dust on the filter bag. The dust that falls into the hopper is sent by means of pneumatic conveying system.
3. The boiler flue gas exhaust system process:
Boiler air preheater exit →bag filter → induced draft fan→wet cleaning equipment→ chimney
Two. Purpose
Specifing bag filter's operation, and ensuring the normal operation of boiler tail flue gas dedusting.
Three. Application
This procedure is applied to bag filter's startup, shutdown, bypass, etc.
Four. The equipment's basic parameters
Number Project Unit Design Parameters
1 Number of devices table 2
2 Rated gas flow Nm3/h 290000
3 The maximum gas flow Nm3/h 320000
4 Rated flue gas temperature of the equipment’s inlet ℃ 144
5 Flue gas impact temperature of equipment’s inlet ℃ 200
6 Equipment resistance Pa <1500
7 Equipment inlet’s dust concentration (wet flue gas) g/Nm3 70.5
8 The dust emission concentration guaranteed value of equipment outlet (converted to dry flue gas) mg/Nm3 30
9 Equipment design pressure KPa +2/-11
10 Day working hours h 24
11 Yearly working hours h 8400
12 Operation method Continuous operation
13 Apparatus body’s leakage rate % <2
14 The normal operation of the gas / cloth ratio m/s ≤1
15 Online maintenance runs gas / cloth ratio m/s ≤1.1
16 Ash bucket number piece 6
Five. Operating rules
1. Dust remover's starting
Dust filter's correct operation is directly related to whether the bag filter reaches its optimal performance, meanwhile it can effectively prevent the filter bag's premature failure.
1.1 The following tasks should be completed before starting:
1.1.2 If the bag is firstly put into use or ever used that has been off-line cleaning, the bag must be pre-spraying to prevent clogging of the filter bag. If the bag has been put into use, but only for a short time offline without ash cleaned. Therefore there will be residual ash layer on the bag, pre-spraying need not to be done;
1.1.2Checking whether all flue pipe's door is closed;
1.1.3 Checking whther equipment lines and fittings' leakage exist.
1.1.4 Adjusting the injection pressure, pulse frequency and pulse width;
1.1.5 Checking whether poppet valve's gas source is enough and smooth;
1.1.6 Opening ash conveying system and fully adhere to its working situation;
1.1.7 Checking whether each filter chamber's air inlet control valve is open.
1.2 Pre-spraying of dust filter
When starting, the new bag is more sensitive, prone to clogging. The flue gas contains a considerable amount of water vapor and other condensable gases, and the fuel is not enough.At the beginning, the temperature of the filter will be lower than the dew point temperature of water vapor, therefore, it is very important to protect filter when the stable operating temperature has not yet reached.The filter surface will be covered with a gray layer by pre-paint spraying to prevent blockages due to the moisture.In the pre-coating process, boiler must be offline. Slaked lime is needed as the following particle's size, or other validated pre-spray material is needed: 25% is less than 20um; 50% is less than 15um; 25% is less than 5um.
1.2.1 Opening the inlet manually control valve.
1.2.2 Starting pre-spray for duct filter, firstly open air poppet valve in each chamber
1.2.3In the pre-spraying process, cleaning timers and pulse valve in all rooms should all be turned off to prevent the filter bag's cleaning.
1.2.4 Opening induced drag fan under the condition that intake air control valve is closed. When the fan works to the maximum speed, slowly opening the inlet air control valve to 30% -40%, however do not let the induced draft fan be in super-power operation. Adequate air is needed to avoid that the pre-coating material falls into the ash bucket.
1.2.5 The pre-spraying trucks or blower is put on the proper position near the dust remover's air inlet pipe. Connecting the car delivery tube and pre-spray nozzle in the flue pipe with ash bucket's manhole doors, or open it.
1.2.6 Adhere to injecting pre-coating materials into the dust remover until each chamber's pressure drops or exceed 125Pa to 250Pa, that is more than an initial figure 125Pa to 250Pa. Observing the airflow or the blower speed, determining the water column's growth from 125Pa to 250Pa due to the pre-paint spraying on the filtering material rather than the wind increase.
1.2.7 Now pre-spraying is over, stopping the truck blower system, taking off the pre-spray nozzle, changed into the tube modification (cap) or covered by manhole doors.
1.2.8After pre-spraying, we should start the boilers and dust removal system. Combustion of the fuel should be within 48 hours after the pre-spraying, dust remover's pre-spraying is substantially an hour. Note: After the pre-spraying,the bag's dust removal should not be done before fuel combustion.
2. Dust remover's startup
2.1 Boiler's starting material is fuel oil, the flue gas temperature is up to 150-175 ℃ or higher after combustion.
2.2 Checking whether each chamber inlet manual regulating valve is opened;
2.3In order to open the induced drag fan, at least four room is online to ensure adequate flue gas channel;
2.4 Only when all the rooms online and the outlet temperature exceeds 140 ℃, the boiler burning could be started.
2.5 During the initial startup process, dust removal's pressure loss is relatively small and low due to the air volume and the amount of dust, automatic cleaning mode is automatically delayed, dust removal should be done before stable operation, in this time the best cleaning mode is differential pressure control. Knowing the thickness of the ash layer due to the differential pressure's rise, when dust remover could clean dust;
2.6 When bag dust remover initially starts, the complete cloth powder layer is not formed on the filtering bag's surface, a small amount of overflowed fine dust will form plumose smoke in the chimney.
3. Dust remover's operation
3.1 After starting, cloth powder layer will be formed on the surface of the filtering bag, dust remover will be in offline cleaning procedures.
3.2 In general,the best display of the dust remover's performance is dust removal system's pressure loss. Especially single filter chamber's pressure loss of the dust remover is the best display of dust-removal system, a sudden increase or falling of pressure loss means the filtering bag's blockage, leakage, the valve abnormal.Ash removal system failure or excessive accumulting dust in the asd bucket.
3.3 In order to protect the filtering bag, the pressure loss in each filter chamber may not exceed 2000Pa.
4. The ash removal of dust bucket
4.1 Offline cleaning pulse jet bag filter with long bag low pressure pulse cleaning control using manual and automatic mode, you can convert each other. Automatic control differential pressure (fixed resistance) and timing control modes can be mutual conversion, pressure test points are provided in the import and export of the filter manifold, and when the pressure reaches the set value (1500-1700Pa), dust each chamber sequentially executed pulse-jet cleaning, cleaning procedures have control cabinet (PLC low voltage cabinet) direct control.
4.2 Time control: selector switch selects "Auto" "time" position, when the timing control system meets the conditions, firstly close room # 1 poppet valve, then start blowing when room # 1 cleaning indicator lights.Opening 1 # poppet valve after blowing, room # 1 starts work; Closing 2 # poppet valve room about 20 interval seconds...... (repeat the job in room # 1 ), in order to complete the cleaning work of all the chamber into the next cycle, starting the dust cleaning process from the chamber #1 after the end of the period .
4.3 Fixed resistance control: Selecting selector switch "Auto", "fixed resistance", starting dust cleaning process when the pressure loss reaches to the set value, firstly start dust cleaning process, then close room # 1 poppet valve. Whne the instructions lights,start blowing,open the chamber # 1 poppet valve after blowing,start chamber # 1 poppet valve, close the chamber 2 # poppet valve for interval 20 seconds...... (repeat jobs in chamber1 #), successively complete the dust cleaning in all chamber. If the dust remover's resistance is still higher than the set value after dust cleaning, continue to clean dust. the cleaning process stop after the completion of a cycle, the dust removal's resistance exceed the set value, the cleaning prosess start again.
4.4 Dust cleaning process may have an operator in the field that starts automatically.
5. The bypass of the dust removal
During the normal operation of the boiler, it may produce a special condition, of which the high temperature is one case that can cause damage of the filtering bag. When the flue gas's temperature is higher than 180 ℃, at this time, the bypass valve need to open. Under adverse conditions, the filtering bag's material will be permanent damage, thus bypass control valves's automatic interlock must be installed to avoid inadvertent damage to the filtering bag.
6. Dust removal's downtime
6.1 Using PLC to close the dust remover, dust remover's poppet valve will close, and then manually shut down the air inlet valve (Note: When in the cleaning process of the filtering bag or accumlating dust is in the ash bucket, the ash conveying system should not be shut down)
6.2 The filter chamber is controlled by the PLC. Only under absolutely necessary condition, single filter chamber's offline is allowed.And online works should recover as soon as possible, because in the chamber's offline , dust remover's cleaning frequency will increase.By PLC or manually shut down the poppet valve, and completely close the inlet's manual control valve, thus achieving the full offline of filter chamber. On the offline filter chamber, marks are hung and limits are started to avoid sudden opening when staff inside the filter chamber.
6.3 When the dust remover's closing time is over 48 hours,performing the following steps:After the shutdown, removing the flue gas in filter chamber, in that flue gas contains a lot of water vapor and other condensable gases.
6.3.1 Doing 3-5 times ash removal before the cooling of dust collector
6.3.2 The dust inside hopper is completely cleaned up.
6.3.3 Closing ash convey system.
6.3.4 Starting fan and cleaning up dust with about one hour.
6.3.5 Closing induced draft fan.
6.3.6 Using the exhaust fan ventilation before entering the filter chamber, immediately closing and checking the door after inspection.
