Abstract
This work evaluates the economics of GTL plant using two synthesis gas methods. The first method called the base case utilizes oxygen as fuel for combustion of natural gas, while the proposed case uses steam/CO2 instead of Oxygen. The aim is to ascertain a more economically viable GTL configuration for an optimal GTL process. The associated flare gas at Egbema production sites in the Niger Delta has been chosen as case study. The gas flowrate is 50MMscfd of raw natural gas which was pre-treated before being fed into the main GTL plant. The liquid yield result shows that the proposed method has a liquid yield of 5730b/d over the 5430b/d gotten from the base case representing an increase in product yield of 5.5%. The economic analyses show a quicker pay-out time of 4.9 years from the proposed model compared to 5.9 years from the base case. Using the proposed method gave an annual cashflow increase of 20.9% and NPV increase of 59.7% at 10% discount rates. Also the DCF-ROR from the proposed method was 20.3% compared to 16.6% gotten from the base method. Thus the proposed method is more profitable in terms of NPV. The project is recommended for application in the Niger Delta stranded and remote gas locations that have before now been subjected to flaring.
Highlights
The basic problem of natural gas lies in its transportation and storage
A natural gas price difference of US$0.5/Mscf led to a 0.36 year increase in pay-out time and a 1.5% decrease in the discounted cash flow rate of return (DCF-ROR) for the Autothermal reformer (ATR) reforming of the Gas to liquids (GTL) plant, 0.4 years increase in pay-out time and 1.7% decrease in DCF-ROR for the proposed steam/CO2 reforming method
The difference in configuration of the GTL plant in the two methods was in the synthesis gas unit
Summary
The basic problem of natural gas lies in its transportation and storage. Unlike oil which is liquid, natural gas takes the shape of its container; special containers must be deployed for its transportation and storage. Gas-to-Liquids (GTL) technologies can offer adequate monetization of small associated gas volumes in scattered locations in the Niger Delta. GTL was viewed as a capital intensive project requiring huge capital expenses and availability of large volume of gas for economic viability. Because of these constraints, only very few large scale commercial plant are Petroleum Science and Engineering 2019; 3(2): 85-93 operational [2,3,4,5]. The processes involved in GTL plant operations are divided into four main units given below: The natural gas pre-treatment units, the synthesis gas unit, the Fisher Tropsch unit, the product upgrading unit. In the Fischer Trospch unit, the synthesis gas is reacted to form synthesis crude which is upgraded in the product upgrading unit [11, 12]
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