The natural gas cryogenic liquefaction technology uses natural gas or synthetic natural gas as feed gas to produce LNG after gas sweetening, dehydration, heavy ends removal and liquefaction. Based on this technology, a Small-scale Universal Modularized LNG Train has been developed.
Technical features, major technical performance orproduct functions:
1) Based on the project scale and the characteristics of gas source, the highly-efficient purification process such as molecular sieve and methanol wash process, low energy consumption LNG production technology such as expansion refrigeration, mixed refrigeration and simple cascade refrigeration, and several LNG storage systems can be selected.
2) A DCS assistance system which has alarm preanalysis and pretreatment suggestion is implanted in the DSC system.
3) The national 863 program “Synthetic Natural Gas Liquefaction Technology”has reached international advanced level via expert argumentation.
4) The technology has obtained 25 invention patents and 33 utility model patents.
At present, the technology has been successfully applied in the projects such as Changsha Emergency Peak Load Regulation Gas Liquefaction Plant, Jingbao COG to LNG project, etc.
a.CBM liquefaction technology
CBM liquefaction employs nitrogen expansion refrigeration process, independently developed by Xindi, which simple, less equipment, easy operation, stable running and low energy consumption.The main equipment includes purification unit(feed gas compressor, purification uint), refrigeration unit(recycle compressor,cold box, expander), storage unit (LNG tank and accessories) and control unit, which are all made in China.
Xindi has built a CBM liquefaction plant as general contractor in Jincheng, Shanxi Province. The plant’s treatment capacity is 150,000m3/d and it has been running safely and stably after it reached the designed capacity.
b.Natural gas liquefaction technology
As for natural gas liquefaction, Xindi has examples with nitrogen expansion refrigeration liquefaction process, natural gas expansion refrigeration liquefaction process, mixed refrigeration liquefaction process, cascade refrigeration liquefaction process,etc., especially, the mixed refrigeration liquefaction process developed independently by Xindi avoids liquid accumulation at the bottom of the cold box and makes the unit energy-saving and stable due to its unique liquid phase stream distribution technology. Its unique dehydration design for the refrigeration system greatly reduces start up time and cost; the unique refrigerant makeup system design also reduces the start up time.
c.LNG plant pressurized liquid transformation technology
By technical transformation for BOG recovery in the LNG storage tank and compressor system in the original natural gas liquefaction unit, it turns the“high temperature and high pressure state” LNG product into “low temperature low pressure state” LNG products and reduces gas loss.
Technical features, major technical performance or product functions:
1) It lowers the temperature and pressure of product LNG, and effectively reduces the gas loss during transportation and LNG filling process.
2) More advanced process, more reasonable parameters and more reliable equipment.
LNG before transformation: temperature -140～-145℃, saturation pressure;
LNG after transformation: temperature -155～-162℃, saturation pressure.
The LNG plant pressurized liquid transformation technology has been successfully applied in the LNG liquefaction plant of Shanxi Qinshui ENN Gas Co., Ltd. which was contracted by Xindi.
d.Spherical cryogenic liquid storage unit
Xindi has the proprietary intellectual property rights for this unit, which is applicable to cryogenic liquid storage, including LNG, liquid oxygen (O2), liquid nitrogen (N2), and other liquids that is stored under the temperature of -100℃~-196℃. The daily gasification is reduced to less than 0.15%.
This unit is a complete cryogenic liquid storage system, consisting of the technological process, main equipment, operation and control system, cryogenic liquid loading/unloading and safety facility, equipment & pipeline layout and the necessary auxiliary equipment. The storage tank body is spherical and is made of stainless steel. The filling volume can reach up to 95% of its total volume, comparing with cluster tanks of same volume (400m3-3,500 m3), the manufacturing cost has been reduced dramatically, comparing with the large vertical normal pressure LNG tank, the LNG spherical tank has lower operating & maintenance cost, lower evaporation loss and is safer.