manufacture 1
Post on 04-Apr-2018
220 Views
Preview:
TRANSCRIPT
-
7/30/2019 Manufacture 1
1/36
MANUFACTURE
OFPRODUCER GAS
-
7/30/2019 Manufacture 1
2/36
PREFACE
This report provides the information
pertaining to the construction, operation and
maintenance of a 500kg per hour biomass
gasifier system .
The first part of the report provides detailed
information regarding the construction and the
working of the gasifier system. The second
part provides information regarding operation
and maintenance of the gasifier system.
This also includes operating the thermal
equipment with the producer gas.
-
7/30/2019 Manufacture 1
3/36
PART 1
SOLID BIO-RESIDUE GASIFIER SYSTEM
-
7/30/2019 Manufacture 1
4/36
INTRODUCTON:
Biomass has been a major energy source prior
to the discovery of fossil fuels like coal and
petroleum. Even though its rule is presently
diminished to developed countries. It is widely
used in rural communities of the developing
countries, further it is used for limitedindustrial uses. Biomass besides being in solid
form can be converted into gaseous form
through gasification.
1.0CONCEPT AND PRINCIPLEBiomass is a natural substance, which
stores solar energy by the process of
photosynthesis in the presence of sunlight.
It chiefly includes cellulose, lignin with anaverage composition of C8H10O3 with
slight variation depending on the nature of
the biomass. The producer gas thus
generated during the gasification process is
combustive. This process is thus possible
-
7/30/2019 Manufacture 1
5/36
in a device called gasifier in a limited
supply of air. The clean combustible gas is
combusted in a burner to generate heat. Inthe reactor the biomass process after
undergoing drying in the upper zones
leaving behind char. The volatilities
undergoes oxidation in the combustion
zone with air being partially supplied in
the surrounding nozzles and the remaining
drawn from the open top. The product
gases of oxidation further gets reduced by
a bed of charcoal and yield a combustiblegases having a calorific value of 4.5-5
MJ/KG with an average composition of
CO-20%, CH4-4%, H2-20%,CO2-12%
and rest N2.
-
7/30/2019 Manufacture 1
6/36
2.0USAGE OF PRODUCER GASThermal energy of the usage the order4.55.0 MJ is released by forming 1ml of
producer gas in the burner. Flame
temperature of as high as 1680K by
optimal premixing of air with gas . For
applications which require thermal energy
gasifiers can be a good option as a gas
generator.
Typically the heat generated by 1 litre offuel oil is generated by 3.5-4 kg of
biomass . The exact composition depends
upon the energy content of the producer
gas , which in turn depends upon the
moisture content of the biomass used .Gasifier is an ideal solution for the above
situation, where hot gas after combustion
can be directly let into the end used
equipment.
-
7/30/2019 Manufacture 1
7/36
3.0SYSTEM DESCRIPTION ANDWORKING
The overall schematic of the gasifier
system is depicted in the figure.
The reactor is basically a downdraft
system where both gas and feed stock
move downward as reaction proceeds. Airrequired for gasification is partly drawn
from the top and the remaining air from
the air nozzle surrounding the combustion
zone . The required suction for this process
is obtained by using the venture effect of
spray nozzles (scrubber) and blower.
Biomass after drying and pyrolysing in the
upper zone of the reactor , undergoes
volatile combustion leading fixed carbonor char by the time it reaches the oxidation
zone , in the oxidation zone volatiles
undergo oxidation with the release of CO2
and H2O. This process undergoes
reduction, in the presence of hotbed of
-
7/30/2019 Manufacture 1
8/36
charcoal and yield a combustible gas
mixture.
The hot gas is led to cyclone and further to
cooling in cleaning train, where the raw
gas which cools to ambient temperature by
a water spray arrangement in cooling
section. The gas then flows to the burnernear the drier.
-
7/30/2019 Manufacture 1
9/36
3.1REACTORThe reactor is basically mild steel
fabricated shell with insulated liningand has an inner lining of ceramic ,
compose largely of alumina . There are
2 sets of nozzles (provided around
combustion zone) which are kept open
during the operation of the system. The
individual air nozzles are provided
with a water seal which are kept open
during the operation and closed to shut
down respectively .There are ignition ports provided
below the air nozzles for torching the
reactor ( to start the reactor ) , water
seals are provided with pneumatic
valves which drain out water duringinitial starter and fills water into the
seals during emergency situations. This
arrangement is separate for 2 sets of air
nozzles in corporated.
-
7/30/2019 Manufacture 1
10/36
A water seals forms the top of the
reactor with a removable cover.
This cover is kept open during theentire operation of the system to
facilitate loading of chips and the air
being drawn from the top, there is a
motorized screw at the bottom to
extract the char . The char outlet is into
a stainless steel fabricated container.
The container has a capacity to hold
approximately 1 shift discharge from
the system.The screw system is decided by the set
of timers both for frequency of
operation and duration. The container
provided has pneumatic valves.
Under normal operation top valve iskept open and bottom is closed .The
switch provided will result in top valve
closing and the bottom opening to
unload the char collected in container.
The system also has a provision to
-
7/30/2019 Manufacture 1
11/36
keep both the valves open for
maintenance and during system
shutdown both valves are closed. Thesystem has necessary safety intelocks
and alarms for improper usage . The
screw is cooled both internally and
externally for which cooling tower is
employed.
-
7/30/2019 Manufacture 1
12/36
3.2COOLING AND CLEANINGTOWER
CYCLONE: The hot dust laden gas
that exits the reactor is passed through
a hot cyclone . Cyclone does the
function of removal of certain quantity
of solid particles . The dust that gets
separated falls into a collection bin
below and thus needs to be emptied
periodically.
COOLING SYSTEM: Twin H2O
spray stations are employed with spray
from top. The spray is developed from
a jet which mixes with the gas and
cools the gas to the ambienttemperature and in process removes
dust and tar. There is a small dump
provided at the bottom which form exit
for the cooler for separating gas and
H2O gets collected in the H20 seal and
-
7/30/2019 Manufacture 1
13/36
overflows by gravity to a
sump,moisture trap is provided at exit
of the scrubber to remove the H2Oparticles in gas .
FLARE
This is provided to check the initial
quality of the combustible gas. Gas is
flared in the burner for few minutes
prior to changeover to drier .It is an
automatic operational system.
-
7/30/2019 Manufacture 1
14/36
LOADING OF CHARCOAL
The reactor is loaded with drycharcoal, preferably till the top or 1m
above the air nozzle level. The size of
charcoal to be loaded is around
40mm*40mm*50mm. Care is taken to
allow only charcoal which is free of
metal pieces, plastic etc.
FEED STOCK REQUIREMENT
The range of biomass that can be usedin the reactor as feed stock are coconut
shells without fibre, different species
of wood whose density is above 300-
350kg/m^3. The maximum moisture
content should be around 12-15 %.
-
7/30/2019 Manufacture 1
15/36
START UP PROCEDURE
Gasifier start up
1.Switch on the instrumentation andcontrol panel.
2.Push the switch to start-up mode,
which will automatically open the
gas nozzle towards the flare.
Manually close fully the main gas
valve near the gasifier. Manually
open the flare line bypass valve.
3.Keep the main gas feed valve closed
near the drier.4.Switch on the cooling tower pump
and fan.
5.Open the reactor top cover.
6.Top the reactor with properly sized
biomass.7.Open all the ignition ports.
8.Hold a flame in the form of a bio-
stack till the char gets red hot.
Combustible gas gets compressed
within few minutes after the ignition.
-
7/30/2019 Manufacture 1
16/36
9.After successfully torching the
reactor close the ignition ports. Open
the air nozzle plugs to allow air entrythrough the air nozzle in the reactor.
10.Light the gas in the flare once theoxygen level falls below 2% the gas.
Start-up diffusion mode typically
within the reactor.
11.Top the biomass chips in thereactor as they undergo mixing
thoroughly at regular intervals of
time depending upon theconsumption of feed time has to be
set manually. Normally the
consumption or time period is 10-20
minutes.
12.System has to operate on flaremode for more than half an hour for
stabilization and to ensure gas of
good quality.
-
7/30/2019 Manufacture 1
17/36
RUN MODE
1.Manually push the button and
energize the run mode.
2.At-least one of the drier local pumps
switch needs to be on.
3.All the drier panels should not beunder flame condition
simultaneously.
4.Open main gas feed valve.
5.Close the flame line valve.
STOP MODE
Manually switch is in the stop mode
energizing. This system is already in
emergency mode.
1.Switch off the cooling tower.
2.Close the flare line valve.
-
7/30/2019 Manufacture 1
18/36
SCREW OPERATION MODE
Though the manual switch
energizes the cyclic timer this cantake place when main gas valve is
open in auto mode or manual inch
mode to operate the screw
interlocks and the top valve should
be open, ash discharged bottom
valve should be closed and screw
choking pump should be on. A
separate switch for unload is
provided which can be operated byauthorised personnel. In closed
mode screw motor can be switched
on with interlock of ash discharge
top valve and ash discharge bottom
valve both being open.
-
7/30/2019 Manufacture 1
19/36
INSTRUMENTATION
The system is provided with H2O tube
manometer at strategic locations formonitoring the health of gasifier.
Pressure switches are provided for
pumping the cooled H20 is provided
with thermostat and O2 level sensor or
controller is provided to indicate O2
percent in producer gas line. These
lines are connected to audio visual
annunciators. In the event of O2 level
exceeding 2%, the operator has tocheck for air leakage into system. The
operation of the screw is automatic
with both on/off timers. The controller
is set at 400 -440 *C. Poor quality of
gas as well as flame failure willgenerate alarm at pre-set temperature.
-
7/30/2019 Manufacture 1
20/36
ASH DISCHARGE VALVES
Switches are turns on manually for ash
discharge.
Interlocks are provided to ensure weather
emergency switches are not energized. This
allows discharge to take place even in
emergency mode. Under normal operation ashtop valve is open and bottom valve is closed.
During discharge top valve is closed and
bottom valve is open. In stop mode both the
valves are in closed position.
-
7/30/2019 Manufacture 1
21/36
SAFETY VALVES / INTERLOCKS
1.Push button to switch on flare ignition in
start up mode.
2.Flare igniton button works automatically
in emergency mode.
3.Main gas blowers are ON when scrubber
pumps are ON and not in emergencymode.
4.Alarms are installed to warn if discharge
valves are opened for more than 10
minutes.
5.Ash discharge valve is open only if screwvalve is OFF.
-
7/30/2019 Manufacture 1
22/36
OPERATION
AND
MAINTAINANCE
-
7/30/2019 Manufacture 1
23/36
DRIER OPERATION
1.Start the drier with fuel oil combustion.2.Once it is ensured that the gasifier operation is
satisfactory and gas generated is combustible,
feed the gas only when oxygen level drops
below 2%.
3.To start the gas feed into dries, close the flareline valve manually and push the switch intorun mode by which flare line valves closes and
main gas line opens.
4.Use the valve near the burner and blower tocontrol the quantity of gas flow. Reduce the oil
flow while increasing gas flow. Airflow has tobe controlled by using BUTTERFLY valve.
5.Always divert gas into the drier when oilflame is on.
6.Once the gas flow starts manometer indicatespositive pressure.
7.Do not switch off the combustion blower incase of flame failure. This is the only way to
remove the gas inside the drier.
8.Set the PID controller at desired temperature.
-
7/30/2019 Manufacture 1
24/36
9.Flame failure is indicated with the help ofthermocouple and controller within 15 seconds
of flame failure.10. Gas feed to drier will cut off and flare line
will open in the following cases.
1.Power failure
2.Flame failure
-
7/30/2019 Manufacture 1
25/36
MONITORING THE SYSTEM
The normal and proper working of gasifier is
ensured by visual inspecton of air nozzle.Continuos flow of biomass is a good sign of
normal gasification process with the
generation of good quality of air. For a given
flow rate sudden or abnormal increase in
pressure indicates the buildup of ash. Thissituation is temporary and can be eliminated
by installing screw conveyors for few seconds
until pressure comes back to normal.
ASH EXTRACTIONThe screw provided needed to be operated
periodically to remove ash formed in the
reactor during gasification process.. this is
required to keep pressure drop within limits
therby allowing trouble free operation.
-
7/30/2019 Manufacture 1
26/36
SHUT DOWN OF OPERATION
During shut down following process must be
followed.1.Switch off the blower if in operation and
close the main gas valve and open flare
bypass valve.
2.Immediately ignite the gas.3.
Top the biomass chips in the reator.
4.Close air nozzle valves, this closes air entryinto reactor.
5.Allow the fumes to come out of the reactortop.
6.Switch off the pump if in operation.7.Switch off the instrumentation and panel.
-
7/30/2019 Manufacture 1
27/36
MALFUNCTIONING AND TROUBLE
SHOOTING
It is important to know the reasons formalfunctioning of reactor. These may be the
following reasons.
1.There could be air leakages into gasifier,resulting in dilution of producer gas .this
leakage can occur at reactor or coolingtower.
2.There can be blockages in the reactor or inthe cooling and cleaning section, causing
resistance to gas flow.
Total pressure drop should not exceed
300-350mm at full load operation.
-
7/30/2019 Manufacture 1
28/36
MAINTAINANCE OF SYSTEM
GASIFIER SECTION
REACTOR
1.Rotate ash conveying screw one turn beforestart up for ash removal.
2.Unload the reactor once the pressure dropsexceed the limit or else unload the ash every
1200hrs.
3.The collection of bin below the cyclone has avolume of 25lts and needs to be emptied every
8hrs.this operation is performed withoutshutting down the gasifier.
4.Extract solid residue from the screw exit waterafter each screw operation.
5.Tighten the bolts and nuts after the first 25minutes of run.
-
7/30/2019 Manufacture 1
29/36
COOLING AND CLEANING SYSTEM
COOLER
1.Clean the cooler sprays and check the spraypattern once every 150 hours of run.
2.Clean the water dump seal-off the solidresidues once every 150 hours of run orduring any schedule weekly shutdowns.
3.Tighten all the bolts and nuts after the first25 hours of run.
VALVES AND BLOWERS1. Clean the control valves pipelines and
blower every 150hours run.
2. Lubricate the bearings of the blower and
change the gland once every 600hours of
operation, use lithium soap based grease.
-
7/30/2019 Manufacture 1
30/36
WATER PUMP
1.Check the foot valve strainer every 150 hoursof operation. Clear off any dust collected on it.
WATER UNDER CIRCULATION
1.Every week slowly add 40 grams of polyelectrolyte in both the tanks and using the
valves keep the water under circulation.
2.Add 500grams of ALUM in both the tanksand using valves kee the water under
circulation.
3.Keep the circulation ON for 30 minutes.4.Allow the water to settle for 1 hour.5.Repeat the above procedures several times
depending on usage and biomass used
during the week.
6.Drain the water slowly through sand andactivated carbon.
-
7/30/2019 Manufacture 1
31/36
LEAK TEST AFTER ASSEMBLY
The entire gasifier has to qualify a leak test,
which is one of the most important event inthe erection of system. Critical sub-
assemblies like the reactor and ash
extraction system, cooler, cyclone have to
qualify the leak test. However an entire
system must undergo a leak test at all theflange joints after the erection at site.
This has to be done in order to ensure that
air doesnt leak into the system and dilute
the producer gas. To conduct this testconnect a pressure link which supplies air at
a pressure of 100-150mm H2O to the exit
duct-in from the blower ,that is prior to the
duct-in connected to the flare. Fill the water
seals of reactor, cooler , water dump and
cyclone with adequate water upto overflow
level. Further cover the top cover of reactor
and fill the top cover water seal with water.
Next, open the pressure line and apply soap
water at all possible flange joints.
-
7/30/2019 Manufacture 1
32/36
Incase there is leak, bubbles will form at all
those points. Ensure all the possible leaks
are pluged properly. In a similar mannerconduct leakage test at all the duct-ins that
leads to the burner.
The leak test, is to be conducted every time
whenever the system is dismantled for anyform of maintainance.
CHECK FOR AIR LEAKAGEGASIFIER
IN COLD CONDITION-PRESSURISED
MODE
1.Light a wick . Blow off the flame and holdthe extinguished wick near to all possible
points for leakage, like the flanged joints
and pipe joints. Incase there is a leak, there
will be tendency for the flame to be drawn
inwards or sucked, indicating the leaking
point.
2.Mend all leaks found.3.The leakage of air could also be due to
insufficient water in the water fills under
-
7/30/2019 Manufacture 1
33/36
the reactor, cyclone and cleaning system.
Ensure that adequate water is retained till
the overflow level.
DOS AND DONTS
DOS
ENSURE THAT1.The Charcoal or biomass does not have
any extraneous materials like, stones,
metal etc.
2.Adequate water level is maintained in allthe water seals.3.Water is being sprayed continuously inthe coolers, water jacket of the screw
conveyor prior during the run.
4.Coolant water temperature does notexceed 5*C above ambient during the
run.
5.Correctly sized dry biomass is beingloaded into the reactor and level
maintained.
6.There is water in the top cover waterseal when it is shut.
-
7/30/2019 Manufacture 1
34/36
7.Reactor is loaded with biomass duringthe operation at regular time intervals
depending upon the consumption.8.There are no voids or gaps in the reactor
by absorbing through the air nozzle.
DONTS
DO NOT1.Pour water into the reactor under any
circumstance to shut down the reactor.
2.Use larger sized and wet biomassother than specified.
3.Expose the bottom of reactor toatmosphere when the reactor is hot.
4.Operate the gasifier at higherload/flow rate immediately after fresh
start, if done there is a possibility of
biomass not totally converting into
char by the time it reaches the air
nozzle. Hence follow start up
procedure meticulously.
5.Extract more charcoal.
-
7/30/2019 Manufacture 1
35/36
UNLOADING THE REACTOR AND
PROCEDURE FOR REACTOR
REPAIR
The reactor has to be unloaded once
the pressure drop across the reactor
shoots beyond 350mm H2O or else as
mentioned in the maintainanceschedule. It is better to leave the
system unoperated for sufficiently
long time, say a day so that the reactor
bed cools down and makes the process
of unloading easier. Firstly the ashextraction system supports bolts has to
be lowered till it touches the ground
and then should be secured tightly.
The support bolts has to loosened until
the wheels touch the ground. Use
water to cool the unloaded hot
charcoal pieces, if this is not done then
there might be chances of fire hazard.
The screw once removed needs to be
closely examined for any erosion or
damages. Check the metallic braded
-
7/30/2019 Manufacture 1
36/36
graphite gland rope before refitting , if
it is too compressed then it has to be
changed.
DAILY CHECK
1.Level in all water seals.2.Drain blower bottom valve.3.
Clean cyclone bottom ash bin.
4.Clean ash extraction system outletduct .
5.Ensure all valves are closed and noair gets into system during
operation.
top related