2.8.15 Surge/ Buffer Hoppers

2.8.15               Surge/ Buffer Hoppers

 

                        Fly ash from the various collection chutes/hoppers of each unit shall be conveyed to buffer/surge hopper, four nos. for each unit.  The minimum effective storage capacity of buffer hopper shall be 10 minutes storage of extraction stream capacity. The bottom portion of the buffer/surge hopper  shall be of conical shape.  Aeration pads shall be provided in the conical portion of buffer hopper to prevent compaction and to fluidize the fly ash during discharge from the buffer hopper.

 

                        Buffer/surge hoppers are to discharge the fly ash extracted from various fly ash collection chutes to pressure transporter system in case of vacuum/pressure extraction system and pressure transportation system.

 

                        Each hopper shall be constructed by 10 mm thick MS plate as per IS 2062 with 10 mm thick abrasion resistant alloy cast iron liners of 300 – 350 BHN hardness at sloping surfaces and outlet area..  Each hopper shall include an access door.  Circular doors shall have a diameter not less than 750 mm, whilst rectangular doors shall have dimensions of at least 750 mm x 750 mm.

 

                        Pressure relief valves to atmosphere from the buffer/surge hoppers are prohibited.

 

                        In order to prevent contaminated air being entering into vacuum pump, 1×100% capacity bag filters shall be provided on buffer/surge hopper.

 

2.8.15.1            Instruments

 

                        Each buffer/surge hopper shall be provided with following instruments as a minimum.

 

a)         Hopper ash level switches                       High                 :           1 No.

                                                                        Low                 :           1 No.   

 

b)         Pressure gauge at the transport

            air inlet line                                                                   :           1 No.

 

c)         Pressure switches at the                         High – High       :           1 No.

            transport air inlet line                              High                 :           1 No.

                                                                        Low                 :           1 No.

                                                                        Low – Low        :           1 No.   

           

d)         Differential pressure gauge

            across the bag filter                                                        :           1 No.

 

e)         Differential pressure switch

            across the bag filter                                                        :           1 No.

 

f)          Pressure or Vacuum gauge with

            bag filter depending on pressure

            or vacuum extraction system                                           :           1 No.

 

g)         Pressure gauge at each of

            the fluidising air inlet line                                                :           1 No.

 

h)         Temperature gauge at each of

            the fluidising air inlet line                                                :           1 No.

 

i)          Vacuum gauge in each of the

            vacuum line to vacuum pump                                         :           1 No.

 

j)          Vacuum switch in each of the                 High – High       :           1 No.

            vacuum line to vacuum pump                 High                 :           1 No.

                                                                        Low                 :           1 No.

                                                                        Low – Low        :           1 No.   

 

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