The gas entering the plant is assumed water saturated at 500 PSIG, free of carbon dioxide, and hydrogen sulfide. The gas is metered after passing through a molecular sieve bed (dried to -100'F water dewpoint) and through a dust filter to remove any molecular sieve dusting. The filter is not spared. Quick opening type permits changing filters in minutes. A DPI is provided to indicate time for change of filters.
In liquefaction, the dry gas is passed through the cold box (E- 1) where it is cooled to a temperature assuring total liquid. This sub-cooled liquid is sent through a separator. A smaller portion of the stream flashes in the separator. This stream, now at reduced pressure, is transferred to storage. The vapors Generated in the separator make up the refrigeration cycle.
This gas, combined with the refrigeration expander effluent, is passed through the cold box, where the feed gas is cooled then recompressed by the two-stage refrigeration expander compressors, through an aerial cooler and on to the refrigeration compressors. The gas from compression is cooled by aerial coolers and an external refrigeration system to near 0'F.
The stream is sent through the first stage of the refrigeration expander where it is cooled, passed through a separator and on to the second stage expander which further cools the gas at the lower pressure to its dewpoint. This stream combines with the vapor from the liquefaction circuit.
The separator for the expanders is not required at equilibrium conditions. However, at start up, the heavier hydrocarbons concentration create substantial liquids that must be removed prior to the expander. These liquids are diverted to the LNG stream.
The plant will reach Equilibrium in a very short period. The LNG accumulation from the system will have the same composition as the feed gas. Note that the feed gas, the LNG, and the fuel gas are all the same composition. If substantial heavy hydrocarbons are present, these will have to be removed in the liquefaction cycle. This cost will be additive to the base price.
The plant is all automatically controlled and provided with proper safety alarms and shutdown devices, fail-safe. A 16-spot enunciator is included in the panel to alert and guide the operator and, in the event, he is unable to correct the problem, to shut down the plant safely. Proper fire, pressure, and thermal relief devices are included to comply with U.S. codes. The flow sheet is incomplete in instruments and safety detail, its purpose being to show essential instruments for control of the process and heat and material balances.
Generally, control is by 4-20 milli ampere electronic circuits; 115V solenoids are used to control diaphragms on valves, etc., by 80-100 PSI dry air.
Instrument and service air are provided with 100% standby with dual pressure points permitting the compressors to operate together or independently, depending upon demands for service air.
The equipment supplied consists of skids prefabricated in our shops. These are:
1. One skid including compressor, gas engine driver, aerial coolers, separators, oil separator/filter, piping, and all instrumentation.
2. One skid including the dehydration consisting of dehydrators, molecular sieve, molecular sieve filter, controls, piping, insulation, electrical, regenerative gas heater, aerial cooler, and water knock out drum. This skid also includes the liquefaction systems, consisting of cold box, separators, LNG transfer pumps, piping, electrical insulation, and controls. This skid also includes the refrigeration unit gas chiller, piping, insulation, electrical, controls, and panel.
3. One skid including the expander containing both wheels, aerial oil cooler, oil reservoir, oil pumps, electrical, piping, controls, and panel.
4. Instrument air compressor package.
1. SITE WORK
All structural steel for skids, equipment supports, walkways, ladders, and platforms are included as well as interconnecting piping and controls.
Concrete is included for all skids and supports.
5. PRESSURE VESSELS
All pressure vessels are included to serve the functions shown on the flow sheet. All are ASME coded.
6. LNG STORAGE TANK
The regeneration gas heater and all Chromolox or equal immersion elements in oil systems are included.
The heater is electrical through 3 MMSCFD. Larger units are direct fired gas heaters.
All exchangers shown on the flow sheet are included. All are ASME and/or TEMA coded.
9. COOLING TOWERS
10. MECHANICAL AND PACKAGED EQUIPMENT
|A. Compressors||All compressors are packaged systems with complete local panels. These are high-speed (1,000-RPM) machines.|
|B. Expanders||Turbo expanders are Atlas Copco or equal complete skids, automated, controlled, full auxiliaries provided. A complete local panel board is included with alarm and shutdown signals sent to a central control room.|
|C. Pumps||Pumps are designed to perform the duties noted and are spared 100%.|
|D. Dehydration Package||The adsorbers are skid-mounted including all piping and controls. A charge of mol sieves is provided, installed at job site.|
|E. Refrigeration||Refrigeration unit is a package.|
|F. Filters and filter separators||F. Filters and filter separators included with appropriate package.|
All instruments are provided with piped and wired panel boards on each skid.
Junctions are in local panels for extensions to the main panel.
Field wiring is included.
All process and utility piping is included on the skids.
Field piping is included.
All piping is per ASME B.31-3.
Electrical is included with skids with junctions to a central source.
Field wiring is included.
Lighting is included at all skids.
Electrical is per NEMA coding and classification.
Inlet service and primary transformers to 480 V/3/60 are not included.
Insulation is included with the skids. Field insulation is included.
All material supplied is painted at least one prime coat of paint to your or our specifications. A final coat of paint is included to your or our specifications.
One charge of molecular sieve is included. All oils, lubricants, and antifreeze are provided for initial startup and operation.
17. STARTUP ENGINEERS
We provide startup engineers as required for startup and operator training.
All detailed engineering, drawings, specifications, and source documents are included.
Four complete sets of operating instructions, spare parts lists, recommended spare parts lists are provided.
All freight to our shops is included. Prices are F/A job site.
20. INSURANCE AND TAXES
Insurance is included while the material is in our hands. Insurance during shipping will be covered by the shipper at our cost.
No taxes for sales, excise, gross receipts, export or import taxes are included.
A 12-month mechanical warranty is provided with all mechanical equipment. All fabrication and installation of other materials are covered by a 12-month warranty.
The plant is also guaranteed to process one million standard cubic feet of gas per day over and above that required for fuel gas. The plant is guaranteed to produce 12,000 gallons (U.S.) of liquefied hydrocarbons per day. The composition of the liquid product will be the same as the inlet gas composition, unless heavy hydrocarbons have to be removed.
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