Patented Technology

HeChen's Static Dust Cleaning Baghouse

Beijing HeChen Environmental Engineering Co.,Ltd (hereafter, called “HeChen”) is able to independently design, modify and install pulse-jet baghouse according to onsite various conditions and requirements, and has its own uniquely-patented static dust cleaning baghouse with rectangle filter cartridges (filter bags & cages).

Since 2001, HeChen's static dust cleaning baghouse has been applied to 50MW, 100MW, 200MW, 300MW and 600MW coal-fired units and are demonstrated to work steady and continually in poor flue gas conditions from variety fault coal combustion. For example, the baghouse’s development has experienced the following steps,

1. In 2001, the baghouse was first installed in a coal-fired boiler at 40 t/hr steam generation.

2. In 2003, the baghouse was first installed in a 50MW coal-fired unit in replacing the original electrostatic precipitator.

3. In 2004, the baghouse was first installed in a 100MW coal-fired unit in replacing the original electrostatic precipitator.

4. In 2005, the baghouse was first installed in a 200MW coal-fired unit in replacing the original electrostatic precipitator.

5. In 2006, the baghouse was first installed in a 300MW coal-fired unit in replacing the original electrostatic precipitator.

6. In 2008, the baghouse was first installed in a 600MW coal-fired unit.

     Due to lower dust emission (Dust concentration<10mg/Nm3 at outlet) and longer bag circle life (>= 6 years), HeChen's static dust cleaning baghouses have widely applied to a lot of coal-fired units.

Baghouse Introduction: Baghoues of one 100MW unit is taken (onsite photo) as an example to explain HeChen's static dust cleaning baghouse, and its work mechanisms as shown in Figure 1.

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Figure 1 Baghoues of one 100MW unit

     As shown in the figure 1, the baghouse has lower compartments known as dirty compartments into which dust particulates-laden flue gas (Tint yellow line) is introduced from the two horn ducts, and upper clean compartments into which filtered clean flue gas is exhausted out. The upper and lower compartments are separated by a metal cell-plate having rows of rectangle holes therein. A plurality of rectangle filter cartridges (bags & cages) are suspended from the cell-plate and thus downwardly into the dirty flue gas compartments. Eventually, filtered clean flue gas is induced to ID Fan. Cleaned flue gas from ID Fan outlet is back-blown through the piping on the roof-top of the baghouse into clean compartments to dislodge dust particulates caked on filter media periodically.  

Rectangle Filter Cartridge: As shown in Figure 2 (a), each filter cartridge is suspended from the cell-plate in alignment with one of the rectangle holes in the cell-plate. The rectangle filter cartridge is arranged in parallel gas flow and has very small flow resistance. As dust particulates-laden flue gas is introduced into the dirty flue gas compartments, the dust particulates are filtered and collected on the filter bags. The dirty flue gas travels inwardly to the interior of the rectangle filter bags, and upwardly out through the rectangle filter cartridge holes in the cell-plate and into the upper clean compartments, and is induced to ID fan (blue line in Figure 1). In comparison of the rectangle bag’s baghouse with pulse-jet circle bag’s baghouse, for the same filter area, the rectangle bag number is approximately 60% of pulse-jet circle bags. The HeChen baghouse is more convenient for online repair or replacement because its baghouse has special observation mirrors and flue gas duct isolation dampers & cold air valves. Theses are specially designed for online repair. In Figure 2 (b), the bag bottoms are fixed tightly in dirty compartments to prevent their damage of collision and abrasion when back-blowing off dust by cleaned gas. The fixed bags are very easy to be unfixed for replacing leaking bag. In general bag length is approximately 7,000 – 9,000 mm depending on unit capacity. The static dust cleaning system has no any damage on bags.

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 (a) Tops of filter cartridges

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(b) Bottoms of filter cartridges in dirty compartment

Figure 2 Filter cartridges of baghoues

Flue Gas Flow and Static Dust Cleaning: It can be seen in Figure 3 that the flue gas in this baghouse is divided by black dash lines into four aisles represented by purple wider lines for equally-distributed flue gas and easy online repair. The red lines represent cleaned flue gas flows from ID Fan outlet. The cleaned flue gas is blown by ID Fan back to baghouse for dislodging dust particulates caked on bags in dirty compartments.

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 Figure 3 Top view of the 100MW unit baghouse

     Electrical motors & dampers of cleaned flue gas are controlled by pressure transducers and DCS program to clean filter media in different bag compartments. The four flue gas flows in the four aisles merge at baghouse outlets and enter Wet Scrubber. During a continuous filtering operation, dust particulates cake onto the filter media, and increases flow resistance and decreases flue gas flow. The filter media must be frequently cleaned.

    When the pressure differential across the filter bags reaches the upper threshold limit, whereupon one suspended back-blow arm-conduit and positioning drive device, as illustrated in Figure 4, start to work and the associated flue gas damper is opened. The cleaned back-blow flue gas is forced in the related row of filter bags in the specific room. One clean circle is initially triggered, and then subsequently cleaning occurs upon each filter bag room regularly, until the pressure differential across the filter bags reaches the selected lower threshold limit, and the clean circle ends. The blown off dust particulates fall in the ash hopper.

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 Figure 4 Static dust cleaning system

    It is very convenient for online repair of the static dust cleaning system. The baghouse of this 100MW coal-fired unit has two horn inlet ducts as shown in Figure 5 (That is showing one of them). As stated above, the baghouse inside is divided into four flue gas aisles. Each horn inlet duct can provide flue gas to two flue aisles. If online repair is needed, a green valve will be closed to stop flue gas flow into one aisle and a grey cold air valve will be opened, and cold air will flow into the aisle and then people can enter this aisle to inspect and repair leaking bag, etc. This realizes quick online repair of leaking bags.

Inspection on Operation Result: Figure 6 shows the inspection result after about 3 months operation for the baghouse of this 100MW unit. The inspection result on one filter bags room in the clean compartment shows clearly there is no any dust leaked during the past about 3 months operation. The room looks very cleaning!

    Figure 7 is an operating screen picture of the 100MW baghouse in the unit’s control room. The baghouse was installed from the retrofit of original electrostatic precipitator. The red points in the figure 7 indicate the installation positions of back-blow arm-conduits and positioning drive devices, which is consistent with that shown in the figure 3.

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 Figure 5 Explanation of isolation and ventilation for online repair

    It can be seen from the figure 7 that the period of each back-blow time is designated 10 second. The pressure differentials across the filter bags are around 600 ~ 700 Pa. The dust particulates concentration is approximately 5 mg/Nm3, quite low!

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Figure 6 Picture of one room in clean compartment

                                after about 3 months operation

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 Figure 7 An operating screen picture of this 100MW unit baghouse.

 In comparison of Electrostatic Precipitator with five electrostatic dust removal zones (dust at the outlet < 10mg/Nm3), for a 600MW coal-fired unit,

1) Small footprint, HeChen baghouse (Rectangle filter cartridges) may occupy approximately 800m2, but electrostatic precipitator 1500m2.

2) Power saving can reach approximately 60%.

3) Static dust cleaning system (back-blow pressure: approximately 3kPa) simplifies dust cleaning system and reduces accident likelihood when compared with pulse-jet baghouse (70kPa-500kPa) and saves power consumption for compressed air production.

4) Low dust cleaning pressure reduces potential damage on bags due to expanding & shrinking of filter bag. HeChen filter bags have a longer cycle life, around 6 years or longer, and less bag leaking in practical operation even if the same filter fabric is used.

5) Cleaning flue gas (from ID Fan outlet) has the same temperature as that of bags, which avoids acid condensing & corrosion and thermal fatigue on bags.

6) A rectangle bag has larger area than a pulse-jet (circle) bag does. For the same filtration area total bag number of rectangle bags is approximately 60% of pulse-jet (circle) bag number.

 

Installation Examples

1. In 2014, the baghouse was installed in a 300MW coal-fire unit of  SunLight Power Station of Shanxi Province.

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2. In 2011, the baghouses were installed in 2×600MW coal-fire units of HeQu Power Station of Shanxi LuNeng Energy.

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 HeQu Power Station of Shanxi LuNeng Energy

3. In 2010, the baghouses were installed in 2×300MW coal-fire units of Coal-Gangue Power Station of Suan Ci Gou of Inner Mongolia.

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 Coal-Gangue Power Station of Suan Ci Gou of Inner Mongolia

4. In 2009, the baghouses were installed in 2×300MW coal-fire units of Coal-Gangue Power Station of Shanxi PingShuo.

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Coal-Gangue Power Station of Shanxi PingShuo

5. The construction of Zhangshan Power Station of Shanxi Province was started in 2006, and the baghouses were installed in its units 3 & 4 (2×600MW) in 2008. This was first time that the baghouses were installed in 2×600MW coal-fired units.

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Zhangshan Power Station of Shanxi Province