Revision as of 13:31, 20 June 2018

Introduction

Feed gas is available at the battery limit of FNNPF Plant through the 24” Encana connector pipeline, joining the feed gas pipeline with the Receiving Station located at the edge of the plant. The normal arrival pressure is 1100 psig, whereas the maximum arrival pressure can go up to 1170 psig. The receiving station is provided with an ESD skid, custody transfer meter, CO2 & H2S analyzers and the plant flow meter. The receiving station is designed for 1300 psig pressure.

The inlet gas then flows to the following stages:

Inlet Gas Measurement: gas enters the process plant to be measured

Raw Gas Separation: the gas has any entrained liquids or containments removed

Raw Gas Filtration: the gas is has any remaining liquids or containments removed

Inlet Gas Flow

Referring to figure 2 the FNNPF’s raw gas inlet flowline in the inlet/outlet building consists of the following:

• 2 manual raw gas inlet block valve and 2 inch vent to depressure to safe location

• Process raw gas inlet ESD valve (XV-8003)

• Meter run

• Inlet gas analyzer

Inlet Gas Block Valves

The 16” raw gas inlet flowline is equipped with a manual inlet block valve upstream and downstream of the Inlet ESD valve. These block valves are normally open. In addition a corrosion coupon is located at the start of the inlet piping to monitor corrosion rates.

Purge Valving

Directly upstream of the ESD (XV- 8003) valve is a 2” high-pressure purge gas tie-in for use during turnaround purging/sweeping, and train repressuring. The purge gas flowline is as follows:

• the purge gas flow line is equipped with local manual valving that is normally closed

• the purge gas flow is normally blinded (or car sealed closed) to prevent the higher pressure raw gas from potentially entering the purge gas piping and souring the FNNPF sales gas flow. The purge gas originates as high-pressure buyback fuel gas from the outlet sales gas flow.

Inlet ESD Valve

The raw gas inlet ESD valve (is located directly downstream of the manual raw gas inlet block valve). The ESD valve is triggered to close automatically in response to alarm/emergency conditions. The valve is only used to isolate the inlet gas from the process – it never acts to control inlet pressure or flow as it is either fully open or shut. The operation of the ESD valve is triggered as follows:

• Alarm/emergency conditions triggered by the safety system or DCS which initiates the automatic closure of the ESD valve to process from the raw gas inlet.

• The FNNPF Control Room Operator can:

- remotely trigger the closure of the ESD valve using onscreen controls at the DCS workstations

- remotely reset the ESD valve using the onscreen selection

- remotely reopen the ESD valve

The ESD valve has local open/closed position indication. As well, the valve position is relayed to the Control Room. The valve can also be operated in local operation, in the event that the valve cannot close from the Control room. At the request of the Control room operator, the area operator will switch the valve over to local operation and use instrument air to close the valve.

Inlet Gas Run

The gas after flowing through the ESD valve then enters the meter run where the flow, temperature and pressure is recorded in a flow computer. This computer will automatically and accurately adjusted the process to be the most efficient for the gas quantities entering the plant.

Inlet Raw Gas H2S/CO2 Analyser

The inlet gas analyzers function as follows:

• The analyzers measure the concentration of H2S and CO2 in the incoming raw gas and then discharges the gas sample via an outlet valve to FNNPF’s HP flare system.
• The analyzer’s measurement data are relayed to the FNNPF’s Control Room where the H2S and CO2 concentrations appear onscreen at the DCS workstations.

Operations Monitoring

The FNNPF Control Room Operator monitors the onscreen H2S and CO2 readings from the analyzer. Vigilantly monitoring the readings provides the first indication of swings or spikes in the acid gas content that may impact the FNNPF’s sweetening operations.

Important

Any change to the inlet gas analyzer (e.g., blocking in, flaring, repair, or calibration) must be relayed to the Control Room Operator.

Inlet Seperation

After the raw gas leaves the inlet metering and flow piping it enters the Inlet Separator. Refer to Inlet Seperator(PV-1109) For more information.

After going through the seperator, the raw gas goes though the Inlet gas filter to removed any fine liquids or mists entrained in the gas. Refer to Inlet Gas Filter(FI-1105) for more information.