The reconciliation of the material balance of a natural gas processing plant

Abstract

Accurate material balances serve as essential tools for controlling, evaluating and optimising petrochemical processes. In natural gas processing plants, where there are only phase separation processes and no chemical reactions, accurate material balances are crucial for ensuring the optimal processing of the natural gas hydrocarbons. Due to random and gross errors, caused by faulty or miscalibrated instrumentation, wrong sampling methods and erroneous laboratory analyses, measured data are unreliable and unsuitable for material balances. In order to compensate for incorrect measured variables, data reconciliation is required, to satisfy the constraints of the material balance and minimise the residual error between the measured and the adjusted variables. Although many software packages exist that do data reconciliation, this work used Microsoft Excel to perform material balance reconciliation on Sasol's natural gas processing plant at Temane, because it is the most widely used engineering tool in the petrochemical industry. A literature study was done and mathematical techniques for the reconciliation of plant data, and statistical methods to verify the results, were obtained. Spreadsheets were created in Microsoft Excel to: process raw input data: derive correction coefficients from historic data; conduct steady-state testing; eliminate gross errors; reconcile the material balance, and verify the results via a sensitivity analysis. This work was implemented and is presently being used to reconcile the material balance of the naturalgas processing plant at Temane.