Gas 2025 Issue

Figure 4 SEM particulate sizing

Figure 5 EDS spectroscopy

A solvency test, magnetic separation test, scanning elec- tron microscopy (SEM, see Figure 4 ), and energy dispersive X-ray spectroscopy (EDS, see Figure 5 ) were performed to help determine the composition of the unknown material in the system. The solvency test and magnetic separation test indicated that the samples were inorganic and had an affinity for a magnetic source. However, the SEM and EDS analyses concluded that the sample was a form of ferrous sulphide with an elemental composition of sulphur (S) and iron (Fe) at atomic percentages of 66.3% and 33.7%, respectively. The SEM analysis indicated that the amine contained particles ranging in size from 2 microns to greater than 10 microns. Online gravimetric analysis was also conducted on the pre- and post-carbon filters in the amine regeneration sys - tem at points upstream and downstream of the filters. This test determined the particulate concentration in samples of the amine upstream and downstream of each filter (see Table 1 ). Online gravimetric analysis has previously been described as critical for accurately assessing total suspended solids (TSS) in samples at risk of solid formation on contact with air, which are liquid samples with high levels of dis- solved iron (such as amine and sour water samples). This method is used to determine particulate content in a variety of fluids and is particularly advantageous when it is desired to capture the particles directly from a process fluid while in operation, minimising the risk that derives from artefacts caused by a reaction of the fluid with air exposure.

Gravimetric analysis results

Unit/vessel

Inlet

Outlet (mg/L)

Removal

(mg/L)

Pre-carbon amine/F-305

0.6 3.5

0.5 5.8

17%

After-carbon solids filter/F-307

Table 1

Based on this gravimetric analysis, it was determined that a minimal amount of the solid contamination present in the amine was being removed by the existing filtration. As a result, the solids would continue to build up within the amine sys- tem, causing operational issues unless an alternative solution was deployed. The 17% solids removal efficiency observed in the pre-carbon filter was inadequate to maintain proper operations of the amine treater system and indicative of both undersized filtration and inadequate removal efficiency for the service. The post-carbon filter showed a 0% removal of particulates in the amine and was most likely overwhelmed due to the poor upstream filtration. Typical removal at the pre- and post-carbon filtration stage should be 95% or more. Fit for purpose A two-step solution for the facility’s amine unit was pro- posed. The first step was to utilise a filtration vessel from

Sweet NGL Sour gas

Lean amine

Regen

Absorber

Sour NGL

F-306 carbon bed

Flash tank

F-305

F-307

Rental

Figure 6 Flow diagram with gravimetric sample locations and rental vessel tie-in points

Gas 2025