ADNOC Gas is a key enabler of ADNOC’s ambitious growth plans and decarbonization strategy. the 7th largest natural gas reserves globally, enabling UAE gas self-sufficiency and industrial growth, and expanding export capacity to meet increasing global gas demand.
ADNOC Gas was formed as part of the consolidation of the operations of ADNOC Gas Processing, ADNOC LNG and ADNOC Industrial Gas. The company became operational on 1 January 2023.
ADNOC Gas Processing (AGP) operates gas processing plants with a combined processing capacity of 8 billion standard cubic feet of gas per day. ADNOC Gas Processing’s first plant was opened in 1981, and the company has gone on to build facilities such as Asab-0, the Bab and Buhasa plants, Asab-1 and 2, the Habshan complex, the Ruwais plants, and a natural gas liquid (NGL) distillation complex at Ruwais. One of the world’s largest plants of this type is Habshan-5, and its facilities include sulfur recovery units (SRUs) that are capable of recovering 1,300 tons per day of sulfur from feed gas. Each of these SRUs operates together with a tail gas treatment unit (TGTU).
Summary of the project
As a part of an AGP digitalization initiative, start-up and shutdown procedural automation was implemented in 2019 at the Habshan-5 plant, starting with SRU 551. A first for ADNOC’s downstream operations, this sought to improve operational safety and efficiency by systematically automating and standardizing operations based on the expertise of the company’s most skilled operators. A further aim was the reduction of workload during unusual state operations.
For SRU 551 at Habshan-5, Yokogawa successfully implemented an Exapilot modular procedural automation solution. The company subsequently installed this solution at three other SRU units at Habshan-5.
Based on the success of the SRU Exapilot project, AGP’s process control team forged ahead with its digitalization initiative in 2020 and 2021 by implementing automation for the C2 recovery/rejection mode changeover at the NGL distillation complex. In this, it had the assistance of Habshan-5 Area1 Operations and Yokogawa India.
The Challenges and the Solutions
Procedural automation involved the following challenges:
- Standardization of procedures
- Reduction of total time required for startup and shutdown
- Reducing the number of deviations from standard operations
- Recording of individual operator actions
- Connecting Exapilot to the HMI
- Reducing human error
A detailed study of the SRU processes was performed so that they could be automated using modular procedural automation. The following sequential procedural modules were subsequently developed for AGP Habsan-5:
- SRU start-up
- SRU shutdown
- C2 recovery to rejection (One touch operation – full automation)
- C2 rejection to recovery (One touch operation – full automation)
For SRU startup, the following procedural modules were developed:
- Incinerator start-up
- Degassing compressor start-up
- Sulfur degassing start-up
- Reducing gas generator (RGG) start-up
- Gas admission to reaction furnace
- Unit start-up
- Quench tower preparation, circulating loops
- Amine absorber and regenerator filling and circulation
- Sulfiding/desulfiding procedure
The above procedure modules were used to standardize the start-up, shutdown, and changeover processes. The know-how of the most experienced operators was embedded in the Exapilot main procedures and sub-procedures to ensure that uniform standard operating procedures (SOP) were followed by all personnel, regardless of skill level. The continuous monitoring of start-up, shutdown, and changeover enables the issuance of timely alerts to operators upon the detection of deviations. This helps to reduce transitional (off spec) products by shortening the switching time (grade changeover) for critical process parameters.
The developers of the SRU startup modules incorporated the suggestions and other input provided by the SRU 551 operation team. Beginning with the startup of an incinerator (H-104), Exapilot follows a predefined procedure to ensure the safe startup of the SRU.
Sample Exapilot Report (incinerator H-104)
As per operation requirements, the following activities are completed by Exapilot during H-104 start-up:
- SRU start-up begins with the startup of refractory repair for H-104.
- 551HV7671-VL is forced to cascade as blower (551B102B) is selected and controller FIC1125,1126 is forced to reset position.
- Ramping SV of PIC3268
- TIC4206 held in range 120-160 deg C for 8 hrs.
- Monitoring of RAMP up till 800 deg C, with ramp rate 25 deg C/hr.
Ethane recovery rejection changeover automation in NGL units (540/541)
The ethane (C2) recovery/rejection procedure modules are as follows:
- 540 C2 recovery to rejection
- 540 C2 rejection to recovery
- 541 C2 recovery to rejection
- 541 C2 rejection to recovery
The following functions are executed:
- Ramping of controllers (SV/MV increment/decrement), parallel and fixed time-based activities
- Monitoring of exchanger critical parameters and deviations (if any), alerts to operators, parallel and fixed time-based activities
- Stabilization of parallel and fixed time-based activities, starting after ramping completion. (PV/SV comparison and alert if not in acceptable range)
Exchanger routing changeover:
- Condition check for changeover
- Ramp open/close of valve
- Monitoring of exchanger parameters
- Exchanger route changeover
The following were achieved by using Exapilot to automate procedures at the Habshan-5 plant:
- One touch operation for C2 recovery to rejection & vice versa, and controller set values, mode change, etc. are fully automated.
- Controllers are forced to reset position during H-101, H-103, H-104 start-up.
- SV/MV values are fed into DCS as per operational requirement.
- SV/MV values are ramped for smooth operation.
- Temperature ramp for H-101, H-103, and H-104 is monitored. Ramping must be in range as per the dry out curve and holding must be as per the assigned time.
- For dry out, does not move forward with procedure until the desired temperature is reached.
- For dry out, during HOLD/WAIT period, temperature is continuously monitored and operators are immediately notified if temperature goes out of range.
- Deviations from standard operations are prevented, e.g. when burner starts for H-101 and temperature peaks at 500 deg C., procedure does not move forward until temperature declines to 250 deg C.
- Standardization of procedures for uniform operation
- Standardization of total time required for start-up and shutdown
By embedding the best operator knowhow to standardize operating procedures, the Exapilot solution has shown excellent results in reducing total man hours for plant start-up/shutdown and minimizing human error.
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