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6/07 p-lCIRC/DateDue indd-p,1

 

A Design of,A Sewage Sludge Gas Collector, and A.Hot Utter

Heitiflg System for the East Lansing Eichigan

Sewage Treatment Plant

A Thesis Submitted to

Tne Fa nlty of

7,,"r "1717* “1' r3” .* 1'77 A Twain
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a“- 44

Clair AL Shaler

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Cdndidete for the Degree of

Bachelor of Science

June 1936

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I'wish to take this ohportunity to thai} Yr. Ther0”r for the

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A View of the Imhoff tank

INTRODUCTION

The city of East Lansing Michigan and Michigan State
College jointly constructed a sewage treatment plant in
1928 to care for the sewage from the city and the College.
This plant consists of a bar rack, a pump station, and an
Imhoff sewage treatment tank. A brick building houses the
pump station and the bar rack.

The sewage flows through the Imhoff tank, during which
time suspended solids settle to the bottom of the tank.
These settled solids accumulate in the bottom part of the
tank, and together with its contained water is known as
sludge. This sludge is held in the tank for a period of
several months. The organic solids of the sludge undergo
digestion, during which process combustible gases, largely
methaneJare given off. At present these gases rise to the
surface of the tank through four gas vents, and escape to
the atmosphere. It is proposed to cover these gas Vents
and collect and utilize the gases. These gases when burned
will be used to heat water, which will be circulated through
radiators to heat the pump station. During the summer

months the gas will be wasted by burning it in a waste burner.

A typical analysis of sewage sludge gas shows:

Methane 76.6%
Carbon Dioxide 14.7%
Nitrogen 8.2%

Oxygen 0.5%

Experience at other plants has shown that the amount of
gas collected is from 0.36 - 0.44 cu. ft. per canita per day.
The average is 0.40 cu. ft. per csoita per day. On the basis
of the pres nt pooulation this will amount to 3,520 cu. ft.
per day, and on the basis of the year 1950 population this
will amount to 5, 80 cu. ft. ‘er day. Corresdonding heat
values are 650 to 750 3. T. U. oer cu. ft. of gas.

It will be shown later that the present estimated amount
of gas is more than sufficient to heat the pump station

building.

30 03311313

The design has the estimated population of 14,200 persons
for the year 1950 as its' basis. The amount of gas produced
is assumed to be 0.4 cu. ft. per capita per day. Using these
assumptions the amount of gas produced will be 5,680 cu. ft.
per day.

The four gas vents of the Imhoff tank will be covered with
a 4" reinforced concrete cover, and each cover will be fitted
with a gas collecting dome. In the outside gas vents the
five pillars, which are spaced at regular intervals, extend
f:om the surface of the tank to the top of the sludge hoppers.
In order to construct the cover a section of the pillar will
have to be removed. The underside of the ends of the covers
will be built 1 foot below the level of the water surface in
the flowing through chambers, and the highest point on the
covers till he at the water level. The covers'are sloped
upward from the ends to the gas domes so the gas will collect
at these points. The covers are below the water level so the
scum will not rise to the surface cf the rater in the vents
and form a hard mat. If the scum is kept wet it will settle
to the sludge hoppers. To prevent CIOgging, a scum.barrier
made of boards set loosely is placed at the bottom of the gas
domes. '

In order to get a good bond between the old concrete, and

the cover, a portion of the old concrete will have to be

iemoved. A strip of concrete 6" wide and 2" deep will be
removed from each side of each.vent along the line of the
cover. The joint between the vent, and the cover will have to
be water tight.

The gas collecting domes will be made of 3/8" steel plates.
Details of the cover and of the dome are shown on the blue
print.

The gas burner that will be used is a Basmor 25 - W'- 6
boiler. This boiler has an input rating of 165,000 3. T. U.
per hour and an output or available B. T. U. rating of
132,000 3. T. U. per hour. This boiler is made by the Premier
Heater Division of the Crane Co. LaPorte, Indiana.

There are three rooms that will require heat. They are 3
the mOtor room, and the room.adJoining, both of which are on
the first floor; and the pump room, which is in the basement
below the motor room.

The amount of radiation surface required in sq. ft. for
each room was obtained by following the procedure given by
H. A. Thrush and Co. of Peru, Indiana in Sweet's Catalog File
for 1936. The temperature to he maintained will be 70 degrees
Fahrenheit.

The size of the pipe used for piping the gas from.the Imhoff
tank to the burner will be 2" in diameter. The size of the pipe
for the hot water flow to the radiators will be 2" and 1%" in
diameter, and the return pipe to the boiler will be 2" in

diameter. All sizes of pine were taken from other designs.

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The res which rises to the surface of the tank is collected
the gas collecting dunes. The pressure due to tne rising
gas forces the was in the domes thrown pipes 2" in diameter

0

to the pump station. The ras goes through a condensate trap,

(.1

and then a meter records the amount of gas produced. For

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pas passes through a fires :ure relief and

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safety measures the
a flame tr 3. The pressure relief is connected to the waste
burner tirn ich is *la ced outside of the buildin3. Irom the

flame trap the gas goes to the burner. The water which is
heated to 180 degrees Fahrenheit is cir ulated taro gh :Tiies

2" and 1}" in diameter to the radiators, and is returned to

the boiler through pines 2" in diameter by means of an electric
circulating water pump.

a water tank is installs" heir the ceiling above the boiler
to care for the exgansion and co ntr: .ction of tile 1% -ter being
heated. A pipe is connected from the flow line to this tank.
A two pen temperature recorder records tne tendereture of tne
flow to the radiators and the return water. A 10 foot chimney
10 inches in diameter is us ed to carry awev the products of

coml U stion.

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ram 3&3 Collecting Domes to Taller

Formula _-om the Textbook,

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cu. ft. of “as per minute

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tie ooilei is e0 lees. ineieior tie drop 11 picssuie is,

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oressure is less tnan 1.0 lo. per sc. ii.

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Small Room - size'SD' X C' X 12'
Heat loss throu n all e; osed or cold surfaces.
Exuosed wall - brick wall coefficient 3 0.46

60 X 12 + 2(9 X 12) - (7 X 3)(doors) -

3(3 X 3)(windows) = 523 sq. ft.

V

Lose per h.ur = 73 X 0.46 X 5;: 3 17,000

Single window 0 X 6) - coefficient = 1.65

loss per hour - 70 X 1.55 X 0(5 X 3) 3 2,550

Ceiling - coefficient = 0.60

Loss per ho;

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Floor - assume temperature in basement to be
45 degrees in zero weather
Temperature difference is 25 degrees (73 - 45
Coefficient 3 0.62

Loss per hour 3 25 X 0.6s X (9 X 50) = 4,190

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Door (3 X 7) - coefficient - 0.

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Loss per hour = 70 X 0.69 X (5 X 7) = 1,012

Air entering room by infiltration
Two ai; changes every hour

V"

£2,243 cu. ft.

volume of rooi = 30 X 9 X 12

Coefficient = 0.036

Loss per hour 8 70 X 0.056 X 3,240 8,150

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i. 0. loss per hour = Sé,0”

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loss per hour -

Air entering room by infiltration
One air change every hour
Volume of room 3 53 X 15 X 18 2 8,130.0u. ft.
Coefficient 3 0.009

Loss per hour 2 25 X 0.00% X 8,130 = 1,820 B. T. U.

Total 3. T. U. loss oer hour 3 24,620 3. T. 3.

Radiation Requirements for Each Room
Using water with a temperature of 180 degrees F there will

be a heat emission of 170 3. T. U. per hour from each s;. it.

Of‘ rqxli-;tiTL3 enchsxte
Iotor Root 76,6d2 e 170 = 451 sq. ft.
Amsll Room $4,0JS f 173 3 2o0 sq. ft.
Pump Room 24,620 f 173 3 laE sq. ft.
Total radiating surface 2 703 sq. ft.

Total ;. T. U. requirement per hour 3 155,297

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1.57 ‘ 711' h"
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An estimate of the

given by the Premier Kezter Division,

Q

With an average 3. T. U. value of gas of

gas necessary for heating the water will be

de“re(-3 day.per sq. ft. of radiation.
Detroit Iichigen has 0,494 degree

Grand Rapids Kichigan has 6,554 degree

.L‘n

Using tne aveioge value of these two cities

degree days for East Lansing Lichigan would be

The total radiation is 796 sq.
Assum 210 heating de cys
of gas per day

6,511; X. 001 X 'f’gk"

210

9,470

 

Aplroximetely 3, 300 cu. ft. of 3L5 will be
year 1950, if the pres en Qt tyne of trectment
use. Cn tile be sis of the present pojulation of

approximately 1,050 cu. ft. of res Will

s.)

With an outdoor temperature of -10 de;rees F

tenoerature of 7) d: rees F the

follows:

dif erezice in t goersture, 30 de“

.i‘num COHS JLI“7.')L.iO.11 if]. C .1.

J»-

O.l X 33 X "Q” $0.875 = 5,575

gas consumfition following
Crone Co.,
700,

0.1 cu.

ft.

amount of gas required is

the procedure
the am unt of
ft. per
days

day s

the number of

6,514.

wasted in the

plant is still in

8,801 persons,

be wasted.

and on inside

5'. S

LLPorte Indiana

there is available only 5,550 cu. ft. of gs per

geretirc that can be maintained is:

7g x 3.1 K 7:5 2 17 degrees V
2 I}!

J.

Pressure Relief

Condensate Trap

wrought Iron Pipe

0)

7,1?“
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\TIIATEJ TOTAL COST

Boiler $235.00 + freight (02-79)

255 ft. 2" diameter C
92 ft. 1;" diameter C
20 ft. i" diameter C

Globe Valve

7 - 2" c
5 - 1-; .. 3
1 _ ;u C
Tees
7 - 2" 3

4 reducers

2" - 1;"

Elle 90 degree

20 - 2" c
12 - 1;" c
2 __;n C

Radiators

790 sq. ft.

03.50
1.75

0.50

$3.19
0.12

0.04 '

3237.79

10.00
10.00

10.00

44050
11.05

0.80

2.00

278.50

f c 1
do. S

Vent Covers

Cenent

Coarse Aggrerste
1.17 tons per
Steel

Reinforcin“

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Domes Steel 3

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cu. yd. X 8.61 C 1.20

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cu. ;Xi.:X 8.01 ’“ 1.30

0.570 lb. per t.

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02.20 per 110;

.. ; fis4.oo per 1,300 ft. 3. X.

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30 R5 nor h

Int aTorfl:

sl Estiméted Cost

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7.50

94.15

200.00

3 ,sss.07

14

CONCLUSION

The amount of gas assumed to be generated is a minimum,
also the coefficients used in determining the B. T. U. losses
are conservative. Consequently on the coldest day there will
probably be enough gas to maintain the desired inside

temperature of 70 degrees F.

 

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BO/LER ROOM LAYOUT
EAJT LANSING MICHIGAN

SE WAGE TREATMENT PLANT
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CLAIR A. JHAL ER

 

 

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