The cooperation between Esso (Thailand) Public Company Limited and Exxon Chemical Company has resulted in construction of the paraxylene project, dubbed Thailand Aromatics Project (TARP), in the compound of Esso Sriracha Refinery. Construction of the paraxylene plant, worth 16,000 million baht, was completed in 1999. The project boasts another milestone in the refinery's history.

On safety, TARP's performance is ranked amongst the industry's very best. All personnel involved in the project - from Esso and Exxon employees to contractor workers - have made an outstanding safety performance, with a record of 11 million working hours with the injury rate at less than half of the best worldwide safety performance for the chemical industry. The project's success results from the team's pro-active safety program with a philosophy, safety plan, key safety elements and goals.

The quality of the Thai workforce is another highlights of TARP as seen in all areas, from painting, insulating, to concrete finishing work and welding. The apparent example is in welding. The average rate of weld repair on TARP was better than the industry norm in Europe and North America.

The world-scale plant is fully integrated with the Esso Sriracha refinery. It produces about 350,000 tons per year of paraxylene, using reformate and mixed xylenes as feedstock. Exxon Chemical affiliates will market the output from the plant in Thailand and the Asian region.

Paraxylene is a petrochemical used to make Purified Terephthalic Acid (PTA), the raw material for producing polyester film, packaging resin and fabrics, for which the Thai and Asian markets are growing faster than anywhere else in the world.

The plant incorporates licensor and Exxon technology to make it highly efficient, safe and environmentally friendly.

The Refining Process

Having been heated and desalinated, crude oil is sent to atmospheric pipestills, of which the operation is based on products' different boiling points. The pipestill consists of a tall vertical tower that contains layers of perforated trays. Heated crude oil from the furnace enters the pipestill tower near the bottom. The lighter boiling components rise up the tower while the heavier boiling components fall to the bottom.

As the lighter components pass through the perforated trays, the oil's temperature gradually drops and vapor is condensed on the trays. The distillation of oil vapors at different temperatures produces various petroleum products such as naphtha, kerosene, diesel and fuel oil.

Light oil from the atmospheric pipestill overhead is sent to the naphtha hydrofiner, where sulfur is removed and then flows to a series of towers called the light ends unit. The separated components consist of a gas stream, which is used for refinery fuel, LPG and naphtha. The naphtha is further separated as light and heavy naphtha. Light naphtha is sent to the gasoline-blending unit. Heavy naphtha with low octane is sent to the continuous catalyst regeneration powerformer to boost its octane by restructuring the molecules of oil. Part of this oil is fed to the aromatics plant to produce paraxylene. The other part is sent to produce different grades of unleaded gasoline.

The oil from the first side stream of the atmospheric pipestill is directed to the kerosene hydrofiner to eliminate sulfur. Most of this oil is blended with additives to produce jet fuel, and the rest is used to make the kerosene.

The oil from the atmospheric pipestill's second side stream is hydrofined and then blended with hydrofined oil from the third side stream to make diesel.

Part of the oil from the bottom of the atmospheric pipestill is sent to a vacuum pipestill to make asphalt or fuel oil. The side stream from the vacuum pipestill is sent to the conversion unit.

The fluidized catalytic cracking unit converts naphtha into lighter oil by molecule cracking. After conversion, the distillation process is used again to separate components into a gas stream that is used for refinery fuel, LPG, and reformate streams that are eventually reblended to produce gasoline. The oil from the side stream of the pipestill is sent to the gasoline hydrofiner and used to make diesel. The oil from the bottom of the pipestill is then sent to make fuel oil.

In summary, Esso Sriracha Refinery's main produce are LPG, gasoline, jet fuel, kerosene, diesel, fuel oil, asphalt, paraxylene and benzene. In addition to a sophisticated computer control system, systematizes laboratory checks conducted by Esso experts are carried out to ensure the highest quality products.