Innovation and Technology Advancements in Measurement of Ultralow Sulfur in Natural Gas Products
Authors: Veerakumar Ukkirapandian , Lallan Sanjay Singh , BaHamaish Zeyad Nasser , Abbas Ahmad 
Published: November 2017

Abstract

Objectives
Objective of this project is to identify right technology and equipment for measurement of sulfur in natural gas products and adapt configuration changes of the system to avoid co-elution and for accurate measurement of individual sulfur compounds at ultralow level in the matrix of butane, propane and LNG. This involves standardization, validation and trials with plant samples.

Methods and procedures
There are different techniques by which sulfur impurities are measured. Some of them are lead acetate paper, air oxidation and combustion, potentiometric titration and gas chromatography (GC) with sulfur chemiluminescence detector (SCD) or Pulse Flame photometric detector (PFPD) or atomic emission detector (AED). We have worked extensively to identify, validate and adopt a new and advanced analytical technique for measurement of sulfur impurities in LNG and LPG products. As the level of quantification goes to ppb level it is very important that the measurement methods must be reliable, stable and acceptable to all customers.

Results and discussion
GC with SCD has been identified as the best suitable one, for our products to determine individual sulfur compounds such as hydrogen sulfide, carbonyl sulfide, methyl, ethyl, propyl, butyl mercaptans and total sulfur. Several trails were performed with certified butane, propane and LNG standards at very low concentration levels and with real plant samples to validate and check for matrix effect and co-elution of COS with propane. The use of methyl mercaptan as calibration standard simplifies the calibration process as all sulfur compounds in our products have equimolar response in SCD.
The innovation and advancement made in the instrument configuration with right separation column, dual plasma burner and improved vacuum level by frequent maintenance of pumps improved the accuracy level of determination of sulfur compounds. The products from plant were tested and monitored for these sulfur impurities daily and their level was much lower than the specification limit delivering high quality products to customer.

Conclusions
Closely monitoring the quality of in-process and finished products from plant helped operators to make corrective actions immediately, in case there is increasing trend in these impurities or total sulfur. This has resulted in improvement of quality and their satisfaction giving more value for customers. Lower the level of sulfur impurities in our products, lower will be the environmental pollution through domestic usage or in power generation. It enhances the reputation of the company and generates more business and revenue.

Novel / additive information
The measurement of sulfur components is important for health, environmental and industrial (corrosion) protection. Environmental regulation require a gradually further decreasing emission of pollutants. The advancements developed have been documented and are suitable for monitoring quality and improvement. This is a valuable knowledge which will benefit other companies in oil and gas sector.