Selection of natural gas liquefaction process
So far, there are three mature liquefaction processes in the field of natural gas liquefaction: step refrigeration cycle process, hybrid refrigeration cycle process and expander refrigeration cycle process.
A) Cascade refrigeration cycle process
B) Hybrid refrigeration cycle process
C) Expansion refrigeration cycle process
Technical and economic comparison of three processes
Set the energy consumption of step refrigeration cycle as 1. See table 3.1-2 for the comparison of various refrigeration cycles and table 3.1-3 for the comparison of characteristics of various refrigeration cycles.
Table 3.1-2 efficiency comparison of various refrigeration cycles
| Refrigeration technology | Relative energy consumption with stage refrigeration |
| Stage refrigeration cycle | 1.00 |
| Mixed refrigerant refrigeration cycle | 1.15 |
| R22 precooled N2-CH4 expansion refrigeration cycle | 1.35 |
Table 3.1-3 comparison of characteristics of various refrigeration cycles
| Index | Stage refrigeration |
MRC | Expansion refrigeration |
|
Efficiency |
high | medium | low |
|
Complexity |
high | medium | medium |
|
Type of heat exchanger |
plate-fin | plate fin or tube wound | plate-fin |
|
Heat exchanger area |
small | large | small |
|
Adaptability |
high | medium | medium |
Considering the factors of investment, energy consumption, operation and maintenance, the mixed refrigerant refrigeration process is selected as the liquefaction process of the unit.
3.2 System overview
After Desanding, heating, pressure regulating and metering, the feed natural gas enters the natural gas pretreatment system, removes CO2, Hg, heavy hydrocarbon and H2O, enters the liquefaction cold box, is cooled, liquefied and supercooled in the plate fin heat exchanger, throttled and flashed to the flash tank, and the separated liquid phase enters the LNG storage tank as LNG products.
The main process and technical methods of the unit are:
Use MDEA to remove carbon dioxide;
Molecular sieve is used to remove trace water;
Removal of mercury by sulfur impregnated activated carbon;
Filter molecular sieve and activated carbon dust with precision filter elements;
MRC (mixed refrigerant) cycle refrigeration process is adopted to liquefy all purified natural gas;
The process system includes:
Desanding, heating, pressure regulating and metering system of feed gas;
Pretreatment system (including decarbonization, dehydration and heavy hydrocarbon removal, mercury and dust removal);
MR proportioning system and MR compression circulation system;
Contact us:
Sichuan Rongteng Automation Equipment Co., Ltd.
www. rtgastreat.com
E-mail: sales01@rtgastreat.com
Phone/whatsapp: +86 138 8076 0589
Address: No. 8, Section 2 of Tengfei Road, Shigao Subdistrict,
Tianfu New Area, Meishan city, Sichuan China 620564
No. 8, Section 2 of Tengfei Road, Shigao Subdistrict,
Post time: Dec-26-2022
