DEVELOPMENT OF A PRACTICAL PROCESS FOR A NATURAL GAS CALORIFIC VALUE ADJUSTMENT SYSTEM WITHOUT BLENDING RICH GAS

摘要

Liquefied Natural Gas (LNG) is becoming an increasingly important part of the world's energy sources. The security of obtaining an LNG source is paramount to the countries importing LNG from foreign countries. As a result, the general trend is to import LNG on a long-term basis (15 to 25 years on a take-or-pay basis) from more than one source. The calorific value of gas varies from source to source. This fluctuation results in the loss of a large amount of cash flow to suppliers and gas quality to customers. Currently calorific value adjustment systems have been adopted in order to supply Natural Gas with constant calorific value. However, the systems are expensive because of blending rich gas or injecting nitrogen. This paper presents a practical process to adjust the calorific value of Natural Gas (NG) without blending rich gas or injecting nitrogen. The proposed process, developed by computer simulation, uses the column type special separator operating at the specific equilibrium status with the control of temperature and pressure in order to separate LNG into high calorific value of LNG stream and low calorific value of vapor gas. The effects of various parameters affecting both productivity and economics of the process are discussed and analyzed quantitatively. The simulation performed in this study reveals optimum operating conditions, which detail the most economical operation of the LNG satellite system. The proposed process has several advantages over the existing system. It increases safe operation of the LNG satellite system by eliminating the Liquefied Petroleum Gas (LPG) facility, which has a different safety regulations, maximizing the benefits by reducing operation cost, and obtaining high gas quality index for the customer.