PTQ Q2 2024 Issue

with the necessary control systems, would require a signif- icant investment. Mitigation: Considering the risk of water cooler leakage and the associated costs for a gas conditioning system, it has been decided to maintain the tracing temperature at 120°C. This approach ensures the dry gas temperature remains at least 45°C above the dew point, effectively achieving a sim- ilar outcome to that of a gas conditioning system. Dry gas filter set-up Findings: During the evaluation of the compressor sys- tem’s components, it was discovered that the vendor had not incorporated a separator downstream of the seal gas filter. This omission meant that any liquid accumulating within the filter could only be removed by isolating the fil - ter, and the filter is isolated when the differential pressure is high. Analysis: The absence of a separator posed significant operational challenges. The filter’s small size and the pres - sure differential across it meant that detecting and remov- ing liquid entrainment effectively was problematic. Liquid that condenses and settles at the bottom of the filter can - not be adequately measured or separated from the seal gas under these conditions. This situation could lead to opera- tional inefficiencies and potential damage to the DGS due to the presence of liquid in the gas stream. Mitigation: To address this critical gap, negotiations with the vendor led to an agreement to install a separator on the filter drain line. This addition is designed with capabil - ities for proper liquid level detection and a draining option, significantly enhancing the system’s ability to manage and remove entrained liquids. The implementation of a separa- tor ensures that the DGS operates under optimal conditions by minimising the risk of liquid contamination.

Heat loss for 1in bare piping at different ambient temp and wind velocity

700

600

15 m/s

500

9 m/s

400

300

3 m/s

200

100

21 22

24 25 26 27

28 29

Ambient temperature (˚C)

3 m/s

6 m/s

9 m/s

12 m/s

15 m/s

Figure 2 Heat loss (w/m) in relation to wind speed (m/s) and ambient temperature (°C).

lacked a gas conditioning system, as recommended by API-692. The EPC contractor expressed concerns about installing such a system, citing potential impacts on the pro- ject’s schedule and cost. Additionally, the requirement for a gas conditioning system was not explicitly stated in the FEED deliverables, contributing to the decision against its implementation. Analysis: A gas conditioning system typically involves cooling the gas to condense out water and hydrocarbon, separating the condensed liquid, and then reheating the dry gas. The proposed configuration would ensure that the temperature across the heater raises the gas to at least above the compressor discharge temperature, thereby maintaining a substantial margin above the dew point. The dew point improvement observed is at least 45ºC, as depicted in Figure 3 . Nonetheless, there is a risk of cooling water leakage from the cooler, which could affect dry gas quality. Implementing a cooler, separator, and heater, along

Dew point estimation for gas conditioning system-DHT Quoted liquid carryover from the various types of mist extraction devices are usually in the range of 0.1-1 gal/MMscf. Ref GPSA Chapter 7 Separator

Heating

Sel Gas V

WC cool

To Dry Gas Seal

Sealgas

E-101

RGC Out

Cooler Out

RGS out

E-100

Ex HP amine

V-100

TEE-100

RGC Suc

Comp Dis & Seal DE

Seal Gas L

MIX-114

SAT-100

Sat Watr

RGC Suc

RGC Out

Sel Gas V

QRGC

HC dew point Water dew point

58.56 70.00

C C

HC dew point Water dew point

62.97 75.05

C C

HC dew point Water dew point

50.00 49.99

C C

Entrained Watr

RGComp

RT Dew Point

Ex HP Amine

Entrained WTR

To Dry Gas Seal

CompDis & Seal DE

Cooler Out

Seal Gas L Sel Gas V

RGS Out

RGC Suc

RGC Out

Sat Watr

Sealgas

0.0000 50.00 60.00 48.14 15.59 3.45

1.0000 50.00 60.00 3.552 156.15 1.60

0.9927 50.00 60.00 3.878 171.73 5.06

Vapour fraction Temperature Pressure Molecular weight Mass ow Phase comp mass ow (overall-HO) HC dew point Water dew point

1.0000 70.00

0.0000 70.00

0.9999 70.00

1.0000 95.40

0.0000 70.00

1.0000 95.40

1.0000 95.00

bar_g 49.00 3.788

49.00 3.877

49.00 18.02 10.00 10.00

49.00 3.878

60.00 3.878

49.00 18.02

60.00 3.878

60.00 3.552

kg/h kg/h

20 , 834.72 0.00

21 , 456.72 622.01

21 , 466.72 632.01

622.01 622.01

21 , 294.99 626.95

171.73 5.06

156.15 1.60

193.5 244.4

50.00 49.99

62.97 75.05

58.60 <empty>

58.56 70

<empty> 263.9

58.56 70.37

62.97 75.05

<empty> 263.9

62.97 75.05

Figure 3 Hysys output for gas conditioning system

PTQ Q2 2024