SECTION 437700 - DIGESTER GAS CONDITIONING AND WASTE GAS BURNER SYSTEM
PART 1 - GENERAL
1.1
SUMMARY
A.
This section specifies equipment required to condition and pressurize raw, wet anaerobic
digester gas for delivery to one of two digester gas boilers (specified elsewhere), or to a Waste
Gas Burner to be wasted. The equipment specified herein shall be procured as a single
complete system and installed by the Contractor.
B.
In general, the digester gas conditioning systems shall process the digester gas through the
following units in the sequence specified here:
C.
1.2
1.
Raw, water-saturated warm digester gas shall be piped from the anaerobic digesters into
dual hydrogen sulfide removal vessels (specified elsewhere). The wet digester gas shall
then be piped to a moisture removal unit. The moisture removal equipment shall include
an air-cooled glycol chiller unit, a glycol circulation pump, and a gas-to-liquid heat
exchanger to reduce the gas temperature for moisture condensation.
2.
The digester gas shall then pass through a coalescing particulate filter to remove particles
larger than 6 microns.
3.
When a demand for digester gas is called for from the boilers, two gas blowers (one duty,
one standby) shall pressurize the gas for delivery to the boilers. Alternately, when no
demand for digester gas from the boilers is called for, a control valve shall direct the flow
to an enclosed digester gas burner.
4.
The liquid water condensate removed from the digester gas shall be piped via a gas-tight
trap device directly to an equipment drain at each condensate removal point. Condensate
shall not be collected and piped above ground to a common drain.
The systems and assemblies furnished under this section shall be designed, manufactured,
and/or supplied by a single vendor. Submittals without all systems included in this specification
will not be accepted.
DESIGN AND PERFORMANCE CRITERIA
A.
Performance Requirements: The digester gas handling and waste gas burner system shall be
capable of treating gas produced by anaerobic digesters to the quality identified in Part B of this
section. The digester gas, after passing through the hydrogen sulfide removal vessels, has
characteristics listed below:
1.
2.
3.
4.
5.
Minimum Gas Flow: 45 scfm
Design Peak Flow: 180 scfm
Inlet gas pressure: 0 – 10” w.c.
Average Gas Temperature: 60-100 °F
Methane, percent by volume (dry): 50-60%
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6.
7.
8.
9.
B.
Maximum Hydrogen sulfide: 100 ppmv
Water Expressed as Relative Humidity: 100%
Minimum Allowable Pressure in Digesters: 6” w.c.
Maximum Allowable Pressure in Digesters: 13” w.c.
Design Requirements
1.
2.
3.
4.
5.
6.
7.
Glycol Solution Chiller: The chiller shall be designed and selected for continuous duty
and for the site elevation and temperatures to constantly supply a propylene glycol
solution to the chilling heat exchanger. The digester gas chiller shall operate on 460 volt,
60 Hz, 3 phase power service. The chiller capacity shall be 33,800 Btu/hr as a minimum
under the design conditions of this section.
Digester Gas Heat Exchanger: A heat exchanger shall utilize the chilled glycol solution
in a gas-to-liquid section to reduce the gas temperature to a maximum of 40°F for
condensation.
Digester Gas Coalescing Particulate Filter: The filter shall be an in-line filter with
removable elements. The filter shall remove 100% of all particles larger than 6 microns.
The filter shall be rated for a minimum of 10 psig. The condensation of gas in the heat
exchanger and the filtration of particulates and moisture in the coalescing particulate
filter shall reduce the moisture content to a maximum of 2% by volume.
Digester Gas Blower: The digester gas blowers shall be designed to constantly operate
under the conditions indicated in this section while meeting the following performance
criteria:
a.
Blower capacity: 45-180 scfm
b.
Minimum Discharge Pressure: 2 psi
c.
Minimum Efficiency at Average Gas Flow: 60%
d.
Motor voltage/Phase: 460/3
Enclosed Waste Gas Burner (Flare): The waste gas burner shall be designed for
intermittent operation, and shall meet all applicable SCAQMD emission requirements for
all ranges of flows, including, but not limited to:
a.
Smokeless Capacity: 100%
b.
Operating Temperature: 1400-1800°F
c.
Retention Time: 0.6 seconds minimum at 1500°F
d.
Emissions:
1)
NOx: 0.06 lbs/MM Btu
2)
CO: 0.20 lbs/MM Btu
e.
Destruction Efficiency
1)
Total Organic Compounds: 99%
2)
Total Non-Methane Organic Compounds: 98%
Explosion Proof Requirements: The digester gas conditioning system control panel, the
glycol circulation system’s chiller and pump shall be located more than 10 feet away
from digester gas conditioning equipment such that they are outside the Class I, Division
2 classified envelope, as defined by NFPA 820. All other digester gas conditioning
equipment shall conform to NFPA 70 for service in a Class I, Division 2, Group D space.
Electrical cabling, conduit and control wiring from the remote equipment shall be as
specified.
Control System: The Digester Gas Handling and waste gas burner System shall control
and monitor the operation of all equipment included herein. The System shall monitor
pressure levels in the digesters and relieve pressure in excess of the maximum allowable
(as indicated in Section 1.2.A) by operating a flow control valve to the waste gas burner.
The System shall continuously monitor gas flow to both the waste gas burner and to the
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boilers. The control panel shall be powered by 480 V, 3-phase power supply as provided
by the Contractor. The control panel shall include all required electrical controls, motor
controls, annunciation devices, alarm systems, and logic devices required for a fully
operable system as required by this specification.
1.3
RELATED WORK
A.
Section 033000 – Cast-in-place Concrete
B.
Section 221060 – Stainless Steel Pipe
C.
Division 26 – Electrical
D.
Division 40 – Process Integration
E.
Section 432100 – Digester Gas Boilers
F.
Section 437100 – Digester Gas H2S Scrubber System
G.
Section 437600 – Digester Gas Safety Equipment
1.4
SUPPLIER QUALIFICATIONS
A.
1.5
The equipment supplier shall have a minimum of 5 years of experience in supply similar
equipment for digester gas purification with the specified treatment and conditioning units.
QUALITY ASSURANCE
A.
Qualifications of installers: Use adequate numbers of skilled workmen who are thoroughly
trained and experienced in the necessary crafts and who are completely familiar with the
specified requirements and the methods needed for proper performance of the work of this
section.
B.
Factory Testing: Factory tests shall be performed according to the Supplier’s standard test
procedures. Certified test results shall be provided as product data. Testing shall contain, at a
minimum, the following:
1.
2.
3.
C.
Static tests of all control and protective circuits.
Not less than five (5) days of operation of the system at the Supplier’s factory with
ambient air as the testing fluid.
The digester gas blower shall be factory tested to confirm performance.
Basis of acceptance: The manufacturer's recommended installation procedures, when approved
by the Engineer, will become the basis for inspecting and accepting or rejecting actual
installation procedures used on this work.
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1.6
WARRANTY
A.
The digester gas handling and waste gas burner system including all equipment,
instrumentation, appurtenances, controls, and system performance, shall have a written
Warranty for the lesser of 18 months from the receipt date of the complete system, or for 12
months of operating time unless otherwise specified. The warranty shall include parts and
labor. Furthermore, the manufacturer shall provide a performance guarantee that the conditions
specified in Section 1.2 will be met. The manufacturer shall provide instrumentation and
monitoring systems sufficient to verify the performance of the system in accordance with the
requirements of this section.
B.
Where equipment or system does not perform as required above, the equipment shall be
repaired or replaced by the manufacturer at no cost to the Owner until such conditions are met.
1.7
PIPING COORDINATION
A.
1.8
The supplier shall coordinate with the Contractor for the design and installation of all
interconnecting digester gas and drainage piping so that the digester gas handling system
functions properly. The Contractor shall furnish the Supplier with piping layouts prior to
fabrication. The Supplier shall review Contractor pipe layouts and notify both the Contractor
and the Engineer of any changes required to make the digester gas handling system function
properly.
ENVIRONMENTAL CONDITIONS
A.
The equipment to be provided under this section shall be suitable for installation in weather
exposed locations at the operating wastewater treatment plant in Riverside, California. The
project site is approximately 600 feet above sea level. Outside ambient temperatures are
expected to range between 40°F and 100 °F.
B.
The area within five (5) feet of the digester gas blowers, the hydrogen sulfide removal vessels,
the gas particle filter and any digester gas valves is considered hazardous in accordance with
NFPA 70 Class I, Division 1, Group D. The area beyond 5 feet and within 10 feet is considered
hazardous in accordance with NFPA 70 Class I, Division 2, Group D.
1.9
SUBMITTALS
A.
Compliance: A copy of this specification section, with addendum updates included, and all
referenced and applicable sections, with addendum updates included, with each paragraph
check-marked to indicate specification compliance or marked to indicate requested deviations
from specification requirements or those parts which are to be provided by the Contractor or
others. Check marks shall denote full compliance with a paragraph as a whole. If deviations
from the specifications are indicated, and therefore requested by the Contractor, each deviation
shall be underlined and denoted by a number, referenced to a detailed written explanation of the
reasons for requesting the deviation. The Engineer shall be the final authority for determining
acceptability of requested deviations.
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B.
Shop Drawings: Before any of the materials of the Section are fabricated, the Contractor shall
submit complete shop drawings to the Engineer in accordance with the provisions of Section
013300, “Contractor Submittals”. Shop drawings shall show all details of:
1.
2.
3.
4.
Certified general arrangement drawings showing all important details and materials of
construction, dimensions, loads on supporting structures, and anchor bolt locations.
Equipment dimensions, component parts and list of materials.
Electrical wiring diagram and details.
Drawing and catalog information detailing all control devices in the control cabinets as
well as overall panel layout interconnection diagrams and construction.
C.
Materials list: Submit three (3) copies of a complete list of all materials and equipment
proposed to be furnished and installed under this portion of the work, giving manufacturer's
name, catalog number, and catalog cut for each item where applicable.
D.
Foundation recommendations and anchor bolt sizing for the vessels, and seismic design
calculations signed and sealed by a California registered structural P.E.
E.
Supplier’s information confirming interface requirements between PLC and plant SCADA
system.
F.
Predicted performance curves for the specified blower operating requirements showing
pressure-capacity, power-capacity and efficiency-capacity curves and surge points. Capacity
shall be shown in cfm, corrected for the site elevation. All performance parameters are to
reflect site conditions.
G.
Predicted digester gas temperature rise from the blower at maximum and minimum inlet gas
flows.
H.
Installation requirements, showing clearances required for maintenance purposes and mounting
details.
I.
Following installation, the Contractor shall provide to the Engineer the equipment supplier's
written report certifying that equipment:
1.
2.
3.
1.10
Has been properly installed and connected.
Is in accurate alignment.
Is free from undue stress imposed by piping or mounting bolts.
PRODUCT HANDLING
A.
Protection: The Contractor shall use all means necessary to protect the condition and integrity of
the equipment provided under this section both during and after receipt of said equipment, and
to protect the installed work and all other trades.
B.
Replacements: In the event of damage during installation, Contractor shall immediately make
all repairs and/or replacements necessary to the approval of the Engineer and at no additional
cost to the Owner.
C.
Deliver materials in manufacturer's original packaging with all tags and labels intact and legible.
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D.
Store and handle material in such a manner as to avoid damage; store at site under cover if
required to meet the conditions of this section.
PART 2 - PRODUCTS
2.1
ACCEPTABLE MANUFACTURERS
A.
Proprietary products: References to specified proprietary products are used to establish
minimum standards of utility and quality. Other materials may be considered by the Engineer
in accordance with the provisions of Section.
B.
Acceptable Manufacturers:
1.
Varec Biogas, a division of Westech Industrial, Inc. (Basis-of-Design)
2.
Martin Machinery, LLC
3.
Perennial Energy, Inc.
4.
John Zink Company, LLC
5.
Or equal
2.2
DIGESTER GAS CHILLER
A.
Construction:
1.
2.
3.
4.
5.
2.3
General: The glycol chiller shall be of the air-cooled weather proof type using screw,
reciprocating or scroll type compressors as the refrigerant motive force. The chiller shall
be a completely packaged unit, factory assembled and tested. The chiller shall have a
fan-cooled condenser refrigerant compressor unit, refrigeration circuit, evaporator, a
power panel and a control panel, full factory refrigerant and oil charge, and accessories
for field installation. The glycol chiller shall be powered from the digester control panel.
Materials of construction:
a.
Condenser tubes: Copper of aluminum
b.
Condenser fins: Aluminum
c.
Evaporator brazed plate: Stainless steel
d.
Evaporator shell and tube: Carbon steel
e.
Frame: Steel
Compressor and Motor: Refrigerant compressors shall be the direct drive, hermeticallysealed type easily accessible for service. The lubrication system shall be force fed.
Compressor motor power factor shall be 0.9 or greater. Provide vibration isolation
between motor compressor unit and frame.
Chilled Glycol Circulation Pump: The pump shall be a centrifugal type pump with a
TEFC motor designed to circulate the specified flow of glycol solution.
Glycol Solution Expansion Tank: The expansion tank shall be the pressurized bladder or
diaphragm type.
DIGESTER GAS HEAT EXCHANGER
A.
Construction:
1.
The digester gas heat exchanger shall be manufactured and tested in accordance with the
ASME Pressure Vessel Code. All welding shall conform to the latest standards of the
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2.
B.
Installation:
1.
2.4
American Welding Society. The heat exchanger shall be the stainless steel multi-finnedtube-core type in a stainless steel housing. Flanged connections shall be provided for
connection to external piping systems. The heat exchanger housing shall have one or two
removable cover plates that allow access to clean the fin-tube core. The heat exchanger
housing shall be provided with NPT drain connections for gas condensate removal. The
heat exchanger shall have an NPT port for installation of a level switch at the point of
condensate accumulation.
Two (2) expansion joints shipped loose to be installed at the inlet and outlet of the
exchanger.
The heat exchanger shall have drain and vent connections and support for horizontal
mounting and shall be installed per the manufacturer’s recommendations. The support
shall be constructed of welded channel and angle steel.
DIGESTER GAS COALESCING FILTER
A.
Construction:
1.
2.
3.
4.
B.
The filter shall Class 150 flanges for in-line connections to piping. Filtration shall be
achieved by stationary, interior filter units consisting of a metal basket and attached fins,
covered by the polypropylene filter element with molded PVC ends. The filtration level
shall be 100% removal of 6 mircron and larger particulates. The filter shall be designed
for vertical mounting with a horizontal in-line flow direction. The filter shall be tapped
and equipped with a 1-inch threaded drain opening. The filer shall be floor mounted.
The unit shall provide access for servicing and easy, quick removal of the pleated filter
element for inspection, cleaning or replacement as necessary.
Two (2) ½-inch connections, one upstream and one downstream of the filter shall be
provided for the purpose of connecting a differential pressure monitoring device. The
vessel shall be provided with a differential pressure gauge installed with valving for
isolation and atmospheric calibration.
The filter system shall be equipped with an ultrasonic level switch for monitoring high
condensate level in the base of the vessel. This system shall provide a signal which shall
be indicated on the touch screen in units of inches of level, and shall further provide
adjustable set-points for alarm and shutdown levels
At the design flow rates, temperatures and pressures, the filter shall not have a clean
pressure drop greater than 2 in. W.C. The filter vessel shall be capable of withstanding
no less than 5 PSIG pressure/vacuum.
Materials of Construction:
1.
2.
3.
4.
Vessel shell: 304 stainless steel
Filter support legs: 304 or 316 stainless steel
Gaskets: Non-asbestos synthetic fiber/nitrile binder
Filter elements: Polypropylene
C.
Spares: One extra filter element shall be provided with the filter.
D.
Experience: Filter assemblies shall be manufactured in the United States. Manufacturers shall
have a minimum of 5 years’ experience in the design and manufacture of this type of
equipment, and shall have a minimum of 10 units operating successfully on digester gas
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installations in this country.
2.5
DIGESTER GAS BLOWERS
A.
Construction:
1.
2.
3.
4.
5.
6.
7.
8.
9.
2.6
The blowers shall be of the direct or magnetic electric motor driven VFD controlled
regenerative type, designed to deliver digester gas at any volume within the capacity
range of the blower, with a relatively constant pressure. The blowers shall be of nonsparking design. VFDs shall be provided to modulate digester gas flow, sized and
selected for the intended service. The blowers shall be capable of exerting a minimum of
0" WC vacuum at the suction side, and shall deliver sufficient pressure to service the
digester gas-fuelled-boiler discharge nozzle at a minimum of 2 psi and shall operate
down to 45 scfm without surging.
The casing shall be cast aluminum. The impeller shall be aluminum and the shaft shall
be 316 stainless steel. Process connections shall be ANSI flanged connections. The
lowest part of the blower casing shall include a ½-inch NPT stainless steel drain
connection with an isolation valve.
The blower shall be driven by a 460 Volt, 3 phase 60 Hz electric motor. The motor shall
have a high temperature switch and shall be suitable for installation in a NFPA 70 Class
I, Division 1, Group D area
The VFD shall be capable of controlling the blower motor by either a manually selected
speed control or by a 4-20 mADC signal provided by the PLC. The operator shall be able
to select a desired pressure at the operator interface console (Touch Screen), and the VFD
will automatically control the blower speed to maintain the selected digester pressure.
The blower shall be furnished with a vibration sensor, mounted on or near the driven end
bearing housing assembly of the blower, and shall develop an output of 4-20 maDC
representative of in/sec vibrations from the blower. The PLC shall accept this signal, and
shall process the signal for touch screen display as well as adjustable alarm and shutdown
levels.
Suitable flexible connectors shall be furnished to isolate the blowers from the piping
system.
Structural Skid: The blowers shall be supplied on a structural skid. The skid shall be
manufactured from ASTM A-36 structural members. The sizes, weights and shapes of
the structural members shall be engineered to support all assemblies and sub-assemblies
in loading, transport and operation. Design criteria for the structure(s) shall be as
required by CBC 2010 and ASCE 07. All welding shall be accomplished per AWS
Section 1.1. Skid finishing shall be in compliance with the preparation, priming, and
painting methods described in section 3.6 of this specification.
Protective Devices: Emergency stop buttons shall be provided and located on the
digester gas compression system. The emergency stop button shall be provided with an
enclosure suitable for installation in a NFPA 70 Class I, Division 1, Group D area
Experience: Manufacturers shall have a minimum of five (5) years’ experience in the
design and manufacture of this type of equipment.
DIGESTER GAS ENCLOSED BURNER SYSTEM (FLARE)
A.
The Digester Gas enclosed flare system shall be a unitized, modular system including all
components for a complete and operational system.
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B.
The Digester gas enclosed flare system shall be pre-piped and pre-wired to the extent possible,
requiring minimal field re-assembly. The flare assembly shall be designed to be installed
remotely from the Digester Gas Handling System (refer to drawings for exact location).
Installation of conduiting, piping, wiring, etc. between the systems is the responsibility of the
installing contractor. The systems shall be designed with junction boxes at each sub-system
such that the installing contractor will need only to attach interconnect wiring to numbered
terminals. Interconnect wiring diagrams shall be provided by the system supplier.
C.
The Digester gas enclosed flare system shall include, but not be limited to, the following
components which shall meet as a minimum the listed specifications:
1.
The main gas valve shall be a pneumatically (compressed air), or electrically actuated
butterfly valve equipped with a stainless steel disk and viton or Teflon seat. The operator
shall be provided as a spring fail close device and shall close when directed by the logic
in less than 2 seconds. For electrically actuated valves, a backup battery shall be
supplied. The manufacturer shall provide the regulator train and mounting facilities for
plant compressed air at between 80 and 100 psig.
2.
3.
Flame arrester: A pressure relief and flame arrester assembly shall be installed at the inlet
to the flare. The assembly shall have an integral thermal shut-off valve. The pressure
drop it imposes on the system shall be a maximum of 2 inches w.c. The flame arrester
shall be constructed of cast aluminum housing with aluminum flame element. The flame
arrester shall be provided with pressure monitoring such that both flare back pressure and
flare + flame arrester back pressure can be monitored. The assembly shall be Varec
series 440 or equal.
Flare stack: The flare stack shell shall be constructed of 1/4" minimum thickness ASTM
A36 carbon steel, and shall be a maximum of 35 ft. in height. Sections of the flare
cylinder shall be attached via continuous welds conforming to AWS D1.1 standards. The
flare stack shall have the following properties and accessories.
a.
Lifting lugs: Minimum two (2) lifting lugs shall be provided, each capable of
carrying the entire weight of the unit.
b.
Maximum internal temperature rating: 2000º F.
c.
Maximum external skin temperature: 250º F.
d.
Concrete Pad Protection: Flare mounting shall be designed such that a minimum
of 4" of passively ventilated air space is provided beneath the insulated flare floor
and the concrete pad.
e.
Insulation: Three (3) layers of ceramic fiber insulation blanket (maximum
2,300OF) or 3” of castable refractory shall be provided as combustion cylinder
protection. If blankets are used, two one inch layers of 8#/ft3 blanket shall be
installed, using overlap outer face construction methods, over one (1) 2 inch layer
of 4 lbs/ft3 density material. Insulation shall be attached to the flare wall and floor
with Inconel 600 series studs and washers.
f.
Insulation coating for blankets:
High temperature, sprayed on surface
sealer/protectant.
g.
Manway: Min. 18" x 18" square, insulated, installed above burners.
h.
View ports: Minimum of two (2), each 2" NPT with removable tempered glass
covers and cooling holes. Viewports shall be located to view the pilot flame, the
base of the main flame and each thermocouple.
i.
Thermocouple ports: As required, 2" NPT with bushing and cooling holes.
j.
Source test ports: Minimum two 4" NPT with cooling holes.
k.
Main gas inlet nozzle: Stainless steel, raised faced slip on weld flange meeting the
requirements of 150 # ANSI specifications, size is 4" ANSI to connect to the 4"
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flame arrester.
The external portion of the stack shall have a SSPC-SP-6 surface preparation and
the manufacturer’s standard priming and top coating, with color by Owner.
m.
Natural gas fueled pilot gas inlet nozzle: 1/2" NPT.
n.
Where required to meet low flow, provide a low turndown (LTD) burner train inlet
nozzle: Diameter as required.
Burner: The burner unit shall have the following properties and accessories:
a.
Anti-flashback: All burners furnished shall be anti-flashback type.
b.
Construction: 304L/316L Stainless Steel (<0.03% carbon content) with castable
refractory venturi liners.
c.
The burner arrangement shall be designed such that a smooth main flame light off
from the pilot burner will take place under all flow conditions. The pilot burner
shall not be located more than 12 inches from the combustion chamber shell
d.
Burner Warranty: The Stainless Steel portions of the burner assembly shall be
warranted by the manufacturer to perform for the purpose for which it is intended,
and to be capable of maintaining compliant operation over the range of specified
design pressures, flow rates and heat rates for a minimum period of two (2) years
from date of delivery to site when operated continuously (>85% Duty Cycle)
within the specified design flow rate and heat loading limits. Offers which do not
address this burner warranty requirement may be considered non-responsive.
e.
Products of combustion temperature measurement shall be provided by a type K
ceramic protection tube thermocouple located adjacent to a test port. The
thermocouple shall be wired to a temperature controller which controls the
modulating air dampers to maintain the specified operation temperature. The
temperature controller shall be complete with a 4-20 mA current output and two
alarms.
Flame safeguard controller: Honeywell or engineer approved equivalent, factory mutual
reviewed. Device shall include an ultra violet signal amplifier module and shall display
flame signal strength at the control panel.
Ultraviolet scanner: Honeywell or equal, Factory Mutual reviewed. Device shall be
"self-checking" type.
Natural Gas pilot system: Removable pilot assembly rated at 40,000 Btu/hr, including
pressure regulator, pressure indicator, solenoid valve, manual shutoff valve and pilot gas
pressure manometer port. Plant natural gas pressure connection shall be a maximum of 2
psig.
Total combustion and quenching air control: Motor operated, 12 gauge galvanized steel
damper(s) with 3/4" shaft at each inlet. 4-20 maDC actuator damper motor(s) shall be
utilized at the louver(s). Actuators shall cause louver(s) to fail open on loss of signal.
Actuators shall be housed in a NEMA 7 enclosure per NFPA 820.
Flare temperature controller: Flare temperature control shall be directed by the inherent
analog control capabilities of the supervisory PLC system, with capabilities of
proportional, integral and derivative control. Controller shall drive damper actuator
motors via a 4-20 maDC signal, and shall include operator adjustable set-point control for
both operational setpoint and low flare temperature. Logic in the PLC controller shall
include auto start louver position signal and automatic switch over capabilities to control
to an adjustable set-point flare temperature setting. Temperature control system shall be
capable of controlling the flare temperature to within +/- 30o F of set-point.
Electronic spark ignition: 5000 V electronic igniter assembly removable from outside the
flare without disconnecting conduit or wiring.
Flare anchor system: Flare mounting feet shall be provided such that appropriate
anchorage can be provided using a HILTI HIT C-100 System using HFA or HAS inserts.
l.
4.
5.
6.
7.
8.
9.
10.
11.
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12.
13.
14.
D.
Spare Parts: One each of the following devices, of the manufacturer, type and model installed
in the system, shall be provided as a part of this scope of work and supply;
1.
2.
3.
4.
5.
6.
7.
8.
2.7
Embedment depth and spacing shall provide full overturn and seismic attachment to
foundation. Flare shall be designed to withstand loads & stresses per the requirements of
UBC100 mph wind loading and seismic zone 4 criteria.
Finish: The stack shall be internally coated with a 1.5 mil layer of bitumastic for
corrosion protection. High temperature primer and finish coat over sand-blast prepared
metal. Sand blasting shall be to SPC SP-10 guidelines.
Ignition transformer enclosure: The enclosure for the ignition transformer shall meet
NEMA 7 to meet NFPA 820 criteria and shall receive the 120 VAC power and hi-tension
conduits.
Flare junction enclosure/main control panel: The flare mounted junction box(s) / panel(s)
shall meet NEMA 7 criteria, and shall house all of the flare mounted electrical gear
required to meet the operational requirements of this specification.
Thermocouple
Flame Safeguard module
Flame Signal Amplifier module
U.V. Flame monitoring sensor
Pilot gas igniter
Louver actuator motor
Pilot gas ignition transformer
Complete set of fuses applicable to system operation
CONTROLS AND ELECTRICAL
A.
General: Controls and electrical devices and systems shall conform to the requirements of
Divisions 26 and 40. All controls necessary for the manual and fully automatic operation shall
be provided.
B.
Instrumentation: All instruments provided by the manufacturer shall be in accordance with
applicable Sections in Division 26, “Electrical,” and Division 40, “Process Integration.” In
addition to instrumentation previously listed, the manufacturer shall supply, at a minimum, the
following instruments:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
C.
Digester gas inlet and outlet temperature transmitters (at heat exchanger).
Glycol inlet and outlet temperature transmitters.
Chiller pump suction pressure indicator
Chiller pump discharge pressure indicator
Coalescing filter differential pressure indicator
Coalescing filter level indicator
Blower inlet and outlet pressure indicators
Blower inlet and outlet pressure transmitter
Blower inlet pressure switch
Blower temperature transmitter
Two (2) mass flow meters: One downstream of the blowers; one downstream of the
control valve to the flare.
Two (2) flare pressure indicators, one upstream and one downstream of the flame trap.
Mass Flow Meters: Mass flow meters shall be supplied to meter flow to both the boilers and to
the flare and shall meet the following requirements:
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DIGESTER GAS CONDITIONING AND
WASTE GAS BURNER SYSTEM
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1.
2.
3.
2.8
The mass flow meters shall be constructed of 316L stainless steel, all welded, with an Sstyle sensor and a maximum operating temperature of 350°F. Meters shall be installed in
a horizontal orientation.
Flow vanes shall be provided for installation upstream and downstream of the meters.
Mass flow meters shall be manufactured by Fluid Components International, or equal.
GAS HANDLING AND WASTE GAS BURNER (FLARE) CONTROL SYSTEM
A.
General: The control panel for the Digester Gas Handling and Flare System shall be compliant
with NEMA 12 specifications at a minimum, and shall be located in the Digester Control
Building, located approximately 50 feet away from the heat exchanger, coalescing filter and
blowers, and approximately 250 feet away from the enclosed flare. The control panel shall be
mounted, installed and pre-wired to the extent possible by the system manufacturer. All
conduiting and wiring shall be completed at the factory to the maximum extent possible. The
complete control system shall be manufactured, wired and tested in a UL approved panel shop,
and shall be specifically designed for the performance of the electrical and logical control
requirements of this project. The control panel shall bear the official UL label confirming UL
classification as an “Industrial Control Panel”. The panel shall include as a minimum, but not
be limited to, the following components:
1.
2.
3.
4.
A load center for all the motors, fixtures, controls and devices included with the system.
The electrical system shall include voltage transformer(s), disconnects, main and branch
circuit protectors and any other protection and/or control devices required for complete
operation of the system based on a single electrical service supply of 480 VAC, 3 Phase,
60 Hz.
A PLC based control center to receive all the signals from the various safeties, controls
and monitoring equipment, and to automatically control all the various components of the
system. An Ethernet module shall be incorporated in the PLC to accommodate
connection to the plant SCADA system. One licensed copy of the appropriate software
shall be provided to the Owner as a part of this scope of work and supply.
An operator interface panel to allow either manual or automatic selection for the control
of the operational components of the system. Such operator interface shall be provided
as a “Touch Screen”, and shall be fully compatible with the PLC and shall be designed
for industrial duty applications.
Safeties: The system shall be equipped with the following safeties as a minimum:
a.
b.
c.
d.
e.
f.
g.
h.
5.
Blower Motor overcurrent
Blower motor undercurrent (surge)
High Flare Temperature
Low Flare Temperature
Flame Failure
Low Digester Pressure
High Digester Pressure
High coalescing filter condensate level
Control Panel Face Mounted Devices: The system shall be equipped with the following
control panel face mounted devices as a minimum:
a.
Auto Dialing Alarm System (ADAS) to accept a minimum of four inputs and shall
be capable of being programmed to contact a minimum of 8 phone numbers.
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437700 - 12
b.
c.
d.
e.
f.
g.
h.
i.
j.
k.
l.
m.
n.
B.
Alarm and shutdown message annunciation (Touch Screen Display)
Load center circuit breakers as required for full system operation.
Test/Off/Auto Switch for the blower
Test/Off/Auto Switch for the system
Open/Closed/Auto switch for the flare shutdown valve
Flame failure annunciation for the flare (Touch Screen)
High flare temperature annunciation (Touch Screen)
Low flare temperature annunciation (Touch Screen)
Inlet Valve Failure annunciation (Touch Screen)
Low DG Pressure annunciation (Touch Screen)
High DG Pressure annunciation (Touch Screen)
Test/Off/Auto Switch for the pilot ignition system
Flame Failure Reset
Operation Logic and Control: The manufacturer shall provide control logic, at a minimum, of
the following:
1.
Upon receipt of signal from the boilers, the compressors will start up to provide the
required pressure to the boilers.
2.
When pressure at the digesters exceeds the preset upper pressure limit (as indicated in
Section 1.2.A), the control valve to the flare shall operate open to a set stop that passes
the minimum flow required by the flare. The control valve will continue to operate in the
open position until the pressure in the digesters drops below the preset limit. At no time
shall the control valve operate in a range that sends an insufficient flow of gas to the flare
to meet emission requirements.
3.
When pressure at the digesters exceeds the preset lower pressure limit (as indicated in
Section 1.2.A), the system shall not operate the blowers or the control valve to the flare.
PART 3 - EXECUTION
3.1
INSTALLATION
A.
General: Install the work of this section in strict accordance with the manufacturer's
recommendations as approved by the Engineer.
B.
Installation shall proceed in compliance with the submitted installation schedule, as approved
by the Engineer.
C.
The work of this section shall be installed plumb and perpendicular to piping where required on
Construction Drawings.
D.
Painting: Marred or abraded surfaces shall be cleaned and refinished in accordance with the
manufacturer’s recommendations.
3.2
START-UP & TESTING
A.
Factory Test: The entire system, including all controls shall be tested at the manufacturer's
plant before shipment. Complete test reports shall be made available which shall show all
system controls operate correctly prior to shipment.
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WASTE GAS BURNER SYSTEM
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B.
Start-up: The manufacturer shall furnish his factory trained representative for a minimum of
three (3) days of start-up & training labor. The representative will remain on site until start-up
of the system has been completed to the engineers’ satisfaction, unless failure to achieve a
successful start-up is NOT the fault or cause of the manufacturer.
C.
Functional and Validation Tests: Upon completion of the installation, functional and validation
tests shall be performed by the Contractor with the assistance of the manufacturer's
representative in accordance with Section 017500, “Commissioning”. The manufacturer’s
representative will demonstrate compliant operation of the system to the engineer’s satisfaction.
Should the system NOT perform to the requirements of this specification, the expense of any retesting, if required, will be borne by the system manufacturer, unless failure to achieve
successful operation is neither the fault or cause of the manufacturer.
3.3
TRAINING
A.
When all required approvals of this portion of the work have been obtained, and at a time
designated by the Owner and/or Engineer, the Contractor and/or the manufacturer’s
representative in charge of start-up and testing shall thoroughly demonstrate to the Owners
operation and maintenance personnel the operation and maintenance of all items installed under
the work of this section.
B.
The instructions shall be separate from the installation, start-up and equipment adjustment
services.
3.4
CLEANING
A.
Clean exposed surface of all grease, dirt and other foreign materials.
B.
Touch up all marred or abraded surfaces as specified herein.
3.5
PAINTING
A.
Surface Preparation
1.
All surfaces of equipment shall be provided with the manufacturer’s standard shop
priming and painting system. The installing Contractor shall be responsible for field
touch up coating, in accordance with Specification Section 098000, “Protective Coatings”
and the manufacturer’s recommendations.
END OF SECTION 437700
WRCRWA
PLANT EXPANSION PROJECT

DIGESTER GAS CONDITIONING AND
WASTE GAS BURNER SYSTEM
437700 - 14