MAXUS STARTS UP TEXAS PANHANDLE GAS PLANT

Warren R. True
Pipeline/Gas Processing Editor

Maxus Energy Corp., Dallas has started up its 190 MMcfd Sunray, Tex., gas-processing plant north of Amarillo to process gas from nearby gathering systems feeding it both sweet and sour natural gas.

The plant replaces processing formerly provided by Diamond Shamrock Inc. at its gas plant adjacent its McKee, Tex., refinery (OGJ, May 24, p. 79). Maxus broke ground for it in November 1991.

The $65.3 million Sunray plant features, the company says, a state-of-the-art cold box for producing helium-a new source of revenue for the company.

Maxus expects production of helium to add approximately $4 million in additional revenue during the first full year of plant operation.

TWO TRAINS

The Sunray plant, says Maxus, enables the company to maximize efficiency in extracting NGLs from both its produced and purchased gas.

The plant extracts CO2 and H2S to meet pipeline specifications and reduces the amount of nitrogen to boost the BTU content of the gas (Fig. 1).

The plant's state-of-the-art technology, says Maxus, results in annual fuel and operating expense savings of approximately $10 million. ABB Randall Houston, was general contractor.

Through separate trains, the Sunray plant processes sweet gas in the Ochiltree train and sour gas in the West Panhandle train.

The Ochiltree train processes approximately 120 MMcfd at full capacity. Because the gas has no H2S, it requires processing only through the expander unit to extract NGLS.

The sour-gas (West Panhandle) train processes approximately 80 MMcfd at full capacity.

Gas from the West Panhandle and Texas Hugoton fields, mainly from Moore and Sherman Counties, must be processed through an amine-gas contactor and a sulfur-recovery unit (SRU) in order to strip the gas of CO2 and H2S.

While the process for each stream differs, the end products are the same, except for the helium.

The methyl diethanolamine (MDEA) contactor removes 50% of the CO2 and reduces the H2S to 4 ppm. The gas then goes into the DEA contactor which removes final traces of H2S and all remaining CO2.

The resulting clean gas continues through the train, while the acid gas goes into the SRU.

This unit converts the H2S into elemetal sulfur through combustion and catalytic reaction.

In molten state, the elemental sulfur is stored in a cement-lined pit (with 5 days's storage capacity before being loaded into a truck for sales.

Before entering the -320 F. coldbox, the gas passes through a prechiller and dehydrator for cooling and drying.

The coldbox-10 x 10 x 120 ft tall-is designed to liquefy the hydrocarbons for NGL products and to extract helium for sale through long-term contract. Linde Division of Union Carbide Industrial Gases Inc., Tonawanda, N.Y., was supplier.

The coldbox can additionally increase the recovery efficiency of propane and ethane and reduce the amount of nitrogen, thus boosting the BTU content of the residue gas.

NGLs are sold, while the nitrogen is vented into the atmosphere. The low-pressure residue gas is used as fuel within the plant with any remainder being compressed for residue-gas sales.

On the Ochiltree train, gas passes through two dehydration systems and enters the expander. The expander raises then quickly lowers the pressure of the gas to liquefy the hydrocarbons for NGL products.

The residue gas is immediately sold, while the NGLs pass through a DEA contactor to extract CO2.

The NGLs from the Ochiltree train are combined with NGLs from the West Panhandle train for sale.

Ajax-Superior, a division of Cooper Energy Services, Springfield, Ohio, supplied the compressors and engines; compressor packaging was by KCI Inc., Tulsa.

OVERALL FIT

Maxus also operates a gas plant in Roger Mills County, Okla., that first began operating in 1983. Added compression in 1991 increased its capacity to 50 MMcfd.

Combined with the processing facilities at the Roger Mills plant, Maxus' processing capability in its Midcontinent region-one of four in which it operates world-wide-totals 240-250 MMcfd. The other areas are southeast Sumatra, northwest Java, and the U.S. Gulf Coast.

In 1992, the company produced more than 103 MMcfd in its Midcontinent region. Additionally, it purchased almost 51.5 MMcfd there. Produced NGLs totalled 8,913 b/d.

Revenues for the Midcontinent region from Maxus-produced natural gas sales in 1992 reached more than $37.5 million.

Maxus says that the region accounts for 52% of its total gas reserves and 54% of its worldwide gas production.