High Quality China Small Scale Liquefied Natural Gas Factory - Customized 2~10×104m3 / D natural gas liquefaction plant – Hengzhong

Introduction

The construction of the project 50 × 10⁴m³/ D natural gas liquefaction project and supporting facilities and one 10000 m3 LNG full capacity tank. The main process units include feed gas pressurization, decarbonization unit, dehydration unit, mercury and heavy hydrocarbon removal unit, liquefaction unit, refrigerant storage, flash steam pressurization, LNG tank farm and loading facilities.

How does the pre-liquefaction treatment of natural gas work?

The well stream of plant feed comes in gaseous form by pipe. Natural gas extracted from the ground contains impurities, water and other associated fluids, so before liquefaction can take place, the gas needs to go through a treatment process to remove undesired substances. The gas goes through a series of vessels, compressors and pipes where gas is stepwise separated from heavier fluids and impurities.

First, water and condensate are removed, followed by removal of acid gas (carbon dioxide, CO2), hydrogen sulfide (H2S) and mercury (Hg). These substances are unwanted, as they may cause ice forming during liquefaction and corrosion in pipelines and LNG heat exchangers. The remaining mix is precooled, and other, heavier, natural gas liquids are then separated from the mix before liquefaction takes place. Removed hydrocarbons can be stored and sold separately. The remaining gas mostly consists of methane and some ethane, which is brought to liquefaction.

How does liquefaction of LNG work?

Transporting compressed gas long distances by pipe can be costly and time consuming, but by cooling natural gas to -162°C, it turns into liquid matter, and its volume decreases by 600 times. This makes it possible to transport the gas by ship, and this process is made possible at the LNG plant. The liquefaction and LNG cooling process are based on thermodynamic refrigeration cycles, and takes place in cryogenic heat exchangers, which absorbs heat from the natural gas. Flash gas and BOG can be used as fuel for turbines used for onsite power generation.

We mainly separate between two main types of liquefaction processes: the classical cascade process where different refrigerants which vaporize at different temperatures are used, and the mixed refrigerant cycle where a continuous, single blend of refrigerants is cooled. Either way, the end product is LNG, which is stored in cryogenic tanks on site before being shipped off.