design and construction details

7/25/2019 Design and Construction Details

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DESIGN AND CONSTRUCTION DETAILS

I. Designing of Fixed dome type Biogas !ant

a. The fixed dome plant, having gas storage chamber as integral part of the digester. It

has four important components viz i. Digester (fermentation chamber ii. !as storagechamber" iii. #lant dome" and iv. Displacement chambers (Inlet $ outlet.

b. %ee &or'ing principle of anata #lants (attached sheets.

c. The theoretical e)uations for designing of these four important components of anataplant using fresh animal manure (in slurr* form as feed stoc' are described belo&+

ssumptions

-. D + + + -./0 + -

1. D 2 3 -./0

4. D 3 -./0 d

5. D for the smallest size plant should not be less than 1 mt.

0. #max 3 67 cm of &ater column (approx. 677 8g2m

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9. :g3 44; of the dail* gas production (corresponds to < hours gas production

/. :i3 :oT3 7.75 cum28g of fresh cattledung.

-7. The minimum p should be /cm (/,7 mm for the smaller size anata plant.

?here#max 3 @aximum allo&able gas pressure inside the plant

A 3 >ated gas production in m

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of the plantBg 3 Dail* gas *ield 2 unit from=manure for a given D 3 Diameter of the digester 3 Diameter of the gas storage chamber

3 Total height of the digester including gas storage chamber

d 3 eight of the effective digester (fermentation chamber:d 3 :olume of digester (fermentationC chamber

g 3 eight of the gas storage chamber

:g 3 :olume of gas storage chamber

f 3 eight of the plant domeEd 3 Dail* feed (slurr* to the plant in lts

>T 3 *draulic >etention Time

:i 3 :olume of inlet displacement chamber:o 3 :olume of outlet displacement chamber

m 3 eight of the displacement chamber

l 3Fength of the displacement chamber (inlet or outletb 3 Greadth of the displacement chamber (inlet or outlet

p 3 :ertical distance (gap bet&een the ceiling of the anata plant dome &here the

gas outlet pipe is fixed and the lo&er end of the discharge opening

Digeste" Design

The D and of the anata plant has to be designed b* trial and error in accordance

&ith the assumption 4 $ 5. The total digester of the fixed dome plant consists of


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a. Eermentation chamber or the effective digester of the plant and

b. !as storage chamber.

Goth (a and (b above are integrated part of each other as explained in the section ofspecial plant components of a fixed dome plant.

a. Design of the fermentation chamber

:d3 Ed H >Ti J1

:d3 ==== H dii

5 5:dd 3 ===== iii

D1

b. Design of the gas storage chamber

:g3 44; of A

:g3 7.44 A iv

D

1

g:g 3 ======== v

5

5 :gg3 ======= vi

D1

Total eight of the digester

3 d K g vii

Lote + If the D2 is not correct as per assumption, ta'e a ne& value of D (not less than 1

mts. for fresh calculation. This procedure for calculation should be follo&ed till theD2 is close to -./0 (or D 3 -./0

Disp!a#ement #$am%e" design

There are t&o displacement chambers in the fixed dome plant inlet displacement

chamber (IDA and outlet displacement chamber (JDA The IDA is the integral part of the

inlet tan' and the JDA is the integral part of the Jutlet tan'. The combined volume of both

the displacement chambers (IDA $ JDA are e)ual to the total volume of the gas storagechamber (!%A so that the slurr* displacement due to biogas accumulation in the latter is

!%A ma* be accommodated e)uall* in the former i.e. IDA and JDA.

Therefore @g 3 :i K :o viii

:g 3 1 :i 3 1 :a ix

@ 3 67 g x

Lote + Eor famil* size anata plants of 1,4,5 $ 9 cum capacit*, the value of m is fixed as

9- cm (9-7 cm for the sa'e of standardization in the design" therefore the e)uation (H does

not hold good for these four sizes of anata plants:i 3 :o 3 m x l x b xi

G* fixing appropriate value of either F or b, the value of other parameter or the

displacement chambers can be calculated from e)uation (xi


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#lant Dome Design

p 3 /7 mm (minimum as per assumption xii

t 3 D250 xiiit 3 (p K m xiv

%elect value of t as the greater of the t&o calculated from e)uations (xiii and (xiv.

Lote+

a. Erom the structural point of vie&, the minimum height of the dome (&ithout

reinforcement should be 'ept as D25. 0.

b. t should al&a*s be 'ept more than m to avoid an* dogging of gas outlet pipe dueto slurr* getting in to it, &hen there is no gas stored in the !as storage chamber,.

c. Eor the smallest famil* size anata plant, the minimum practical value of p &ould

be /7 mm (or / cm

II. Designing of mo&a%!e d"'m type Biogas !ant(

a Digester :olume 3 Dail* Foading H >etention time

b !as holder volume 3 07 ; size of the plant

design and construction details

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