Domestic and international technologies for liquefied LNG

At normal pressure, when the temperature drops to -163°C, natural gas transforms from a gas to a liquid, which is what is known as LNG. LNG is a non-toxic, colorless, odorless liquid with a density of approximately 425 kg/m3 at -163°C. The main advantage of LNG is that its volume is reduced to about 1/600 of the volume it has in gaseous form under standard conditions; therefore, under certain specific conditions, storing and transporting natural gas in the form of LNG can be more economical than using gaseous natural gas. LNG transport is currently the primary method for transporting natural gas over long distances, and it represents an effective way to improve the utilization rate of natural gas resources in marine and desert areas. Moreover, the cost of LNG transportation is only 1/6 to 1/7 of that of pipeline transportation, and it also helps to reduce the risks associated with laying pipelines due to insufficient gas supplies. Yes, LNG plants are large in scale, their equipment is expensive, the purification and liquefaction processes are complex, and operating costs are high. The initial investment for an LNG plant with a daily production capacity of 400 m3 is over 1×108 yuan. Most of the world’s LNG is transported by ship. LNG carriers have complex structures, high technical requirements, and are extremely costly to build. Furthermore, due to the low storage temperature, an LNG leak will quickly result in the formation of an explosive cloud; therefore, it poses a high level of danger during production, storage, and transportation. The process of supplying natural gas in the form of LNG is known as the LNG supply chain, which includes steps such as natural gas liquefaction, LNG storage, LNG transportation and loading/unloading, and LNG regasification. Based on the purpose of liquefaction, natural gas liquefaction plants are typically divided into base-load and peak-shaving types. The purpose of a base-load liquefaction plant is to transport natural gas in liquid form to consumption sites, and it is characterized by continuous operation throughout the year and relatively steady output. The purpose of a peak-shaving liquefaction plant is to provide a method for storing and regulating gas supply in natural gas supply systems. When the amount of gas supplied through pipelines exceeds the demand, the excess natural gas is liquefied and stored in the LNG tanks of the liquefaction plant. When the pipeline supply is less than the demand, the stored LNG is vaporized again and added to the supply system. LNG is typically stored at low temperatures and normal pressure, with storage temperatures below -161°C and pressures generally not exceeding 0.03 MPa. LNG storage tanks are classified into three types: above-ground metal tanks, above-ground metal/concrete tanks, and underground tanks. The daily evaporation rate of large LNG storage tanks is generally between 0.04% and 0.1%. The transportation methods for LNG include sea transport and road transport via tankers. The purpose of LNG regasification is to convert liquefied natural gas back into a gaseous state so that it can be supplied to users. The re-vaporization process takes place in specialized evaporators, which are divided into open tube rack evaporators (ORV), submerged combustion evaporators (SCV), and air-temperature evaporators.

Sea transport is an important link in the LNG supply chain, responsible for the long-distance transportation from base-load liquefaction plants to LNG receiving stations. According to statistics, the cost of shipping LNG accounts for 20% to 55% of the total cost of the LNG supply chain. Basic load liquefaction plants are usually built by the sea with accompanying shipping terminals. The function of an LNG receiving station is to receive, store, and regasify LNG, with the regasified natural gas being fed into conventional natural gas distribution networks. In addition, some receiving stations also have the function of LNG transfer, that is, transporting LNG to LNG satellite stations using specialized small ships or tankers. Based on international experience, the minimum scale for LNG receiving stations at present is 300×104 tons per year. The main types of operational LNG ocean-going carriers are the MT type (Moss Rosenberg type) and the GT type (Gas Transport type). The main difference between them lies in the structure of the LNG cargo hold and its relationship with the ship’s hull. At 1990 price levels, the construction cost of an LNG carrier with a cargo capacity of 12.5×104 m3 is approximately $170–200 million, while the corresponding cost of transporting natural gas by sea is about $0.40–0.47 per 1000 km•m3. According to statistics, in 1999 there were 113 LNG carriers worldwide, with a total transport capacity of 1243.2 ×104 m3.

Inland transportation of LNG includes tank truck transport and inland waterway shipping. Globally, the scale of inland transportation of LNG is far smaller than that of sea transportation. Abroad, inland transportation is primarily used as a transfer method from LNG receiving stations to satellite stations. Such satellite stations are equipped with LNG reception, storage, and regasification facilities; they can supply gas independently to dispersed industrial users, small and medium-sized towns, or residential areas, or they can serve as peak-shaving facilities for large-scale gas supply systems. Furthermore, it is expected that LNG-fueled vehicles will see rapid development, and inland transportation will then take on the task of supplying gas to LNG refueling stations.

Abroad, there are companies like BV, Air Product, and Linde; in China, some claim to have such capabilities but lack actual performance evidence

There are already quite a number of people in the country who dare to claim to have expertise as well as proven results. However, due to confidentiality agreements, practice is not possible in the short term. For example, at Huasan No.3 Hospital, Dazhou and Ordos – they are responsible for the overall design and construction, while the foreign party provides the process packages. But they can’t take on jobs alone

6# Bastaro: Yes, the process package still comes from abroad. Also, there are very few domestic manufacturers capable of producing low-temperature tanks (fully enclosed type); foreign parties generally do not allow them to participate in the design, at most allowing them to handle only supporting tasks.

I just don’t understand: liquefied natural gas requires investment, so why build liquefied natural gas facilities in a country like ours with such limited gas resources?

A passerby learned it; I really didn’t understand it before

Chuan Kong Jue has the capability to take on the overall contracting of a project of 1.2 million square meters