PTQ Q4 2024 Issue

Grayson Streed (GS) thermodynamic package to model the system accurately, where column operates under total reflux conditions. The Aspen Process Economic Analyzer (APEA) was employed to estimate equipment costs, ensur- ing a thorough economic assessment alongside the technical evaluation. The parameters set for this study were: • Feed rate: 98,000 bpd. • Feed total water content: 5,000 wppm.

Differences in resource use across the various setups for Cases 1-4

Utility

Case 1

Case 2 73,241

Case 3

Case 4

MP steam, kg/h

316

281

206

Cooling water, kg/h 979,018

5,480,465

668,139

661,194

Power, kW

526

549

521

Table 1

Utility consumption Utility consumption for each evaluated VD configuration is summarised in Table 1 . Analysis of utility consumption: • Single-stage dryers (Case 1) require higher MP steam, which is also reflected in higher cooling demand compared to Cases 3 and 4. • Single vacuum tower without pre-condenser (Case 2) requires significantly more steam for the ejector compared to other configurations. This high steam demand also results in greater cooling duty due to increased steam utilisation. • Power consumption is relatively similar across the configu - rations, except for Case 2, which exhibits slightly higher power needs due to its greater mechanical and thermal burden. Pre-condenser effectiveness: Integrating a pre-condenser (Cases 1, 3, and 4) substantially reduces utility consumption. By pre-condensing vapours before they enter the ejector, the load on ejectors and cooling systems is significantly decreased, leading to lower overall utility usage. Two-tower efficiency: The two-tower system (Case 3) with a pre-condenser shows improved efficiency in cooling duty compared to the single-tower setups (Case 1), highlighting the benefit of distributing the workload over more stages. Cost implications: Higher utility consumption, as seen in Case 2, can translate to increased operational costs, sug - gesting a potential trade-off between system simplicity and economic efficiency. This analysis underscores the importance of system con - figuration in optimising utility consumption and overall oper - ational efficiency in ULSD drying processes. The decision on which VD configuration to use should consider both the Capex and Opex. Financial implications Evaluation of financial implications of various VD configu - rations takes into account adjustments for inflation and is considered alongside Capex and Opex, based on historical and projected costs. Inflation adjustments: The equipment costs, sourced from the Aspen Process Economic Analyzer (APEA) prior to 2019, have been adjusted for an average annual inflation rate of 2.5% in Saudi Arabia from 2019 to 2024, cumulatively reaching about 13.15%. This adjustment reflects an increase in costs in line with economic conditions. Total installed cost (TIC): The TIC is estimated at seven times the equipment cost, derived from similar project data. Operational expenditure (Opex): This includes utilities (MP steam, cooling water circulation, and power) and sour water processing costs: • Sour water processing: $13.2 per ton

• ULSD product target total water content: 50 wppm. • Feed pressure and temperature: 12 barg and 160°C. • Product ULSD pressure and temperature: 9 barg and 45°C. • Air leakage rate: 45 kg/hr per vacuum tower. • Vacuum tower overhead pressure: Varied between -0.49 barg (392 mmHg) and -0.86 barg (115 mmHg) to achieve a ULSD product water content of 50 wppm. • Medium pressure ( MP) steam operating conditions: Pressure 11 barg and temperature 190°C. • Cooling water: Pressure 6 barg, supply temperature 30°C, return temperature 40°C. • Flare pressure: 0.3 barg. • Number of trays in vacuum tower: two (representing two theoretical stages). • Liquid residence time: five minutes in a single tower con - figuration, two minutes in the first tower, and five minutes in the second tower for dual tower configurations. • Number of ejector stages: two, with the compression ratio maintained the same for both stages and calculated using the formula (Pf/Pi) ^ (1/2), where Pf is the final pressure at discharge in bara (1.31 bara) and Pi is variable as previously mentioned. The study evaluated four distinct configurations of VDs to determine their efficiency and effectiveness under varying operational conditions, illustrated with four detailed figures (PFDs) representing Cases 1-4 and available at https://drive. google.com/drive/folders/1n3MefOF7tcGCffU3vy87a9t5p - 3b0Usa2?usp=sharing. Each configuration was modelled and analysed using Hysys simulation, including: u Case 1: Single vacuum tower with pre-condenser: This setup includes a pre-condenser system integrated with a single vacuum tower, designed to condense vapours before they enter the vacuum system, potentially reducing the load on the ejector and enhancing overall system efficiency.  Case 2: Single vacuum tower without pre-condenser: This configuration utilises a single vacuum tower without a pre-condensing step, providing a baseline scenario to eval - uate the impact of omitting the pre-condenser on system performance and operational costs.  Case 3: Two vacuum towers with pre-condenser: Incorporating two vacuum towers with a pre-condenser allows for enhanced separation efficiency and potentially reduces the load on the ejector.  Case 4: Flash vessel followed by vacuum tower: This configuration includes a flash vessel prior to the vacuum tower. The flash vessel is used to separate bulk water and heavy hydrocarbons under reduced pressure, which can significantly decrease the load on the subsequent vacuum tower and improve the drying process.

PTQ Q4 2024