The mass balance model has a level of detail that provides sufficient redundancy of measurements and crosschecking between measurements.

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2 ABSTRACT This paper shows different aspects of the implementation of S-TMS Production Accounting System at BRC Antwerp refinery. In addition, it describes BRC Antwerp refinery's yield accountant experience using the S-TMS Production Accounting System on a daily basis since At BRC Antwerp refinery, the production accounting system is highly integrated with other refinery systems, thus minimizing the manual data entry efforts and avoiding duplicated entry errors. The mass balance model has a level of detail that provides sufficient redundancy of measurements and crosschecking between measurements. As one of the asset management tools, production accounting technology has helped refineries and petrochemical facilities detect material losses by improving data quality and operating procedures. The simultaneous crosschecking of the site s transactions, movements, inventories, lab data and measurement systems, on a daily basis, by subjecting them to the mass balance constraint is the cornerstone of good refinery information. Operation and planning decisions have also benefited from the revised data. The paper describes many aspects of the daily operation of the system in the refinery, what errors are typically found and how S-TMS helps to find them. ERTC Asset Max 2010, Budapest, Hungary Page 2 of 12

3 INTRODUCTION Refinery wide mass balance is the basis of any loss control initiative. As one of the asset management tools, production accounting technology has helped refineries and petrochemical facilities detect material losses by improving data quality and operating procedures. Trustworthy refinery information is achieved by crosschecking the site s purchases and sales, tank movements, inventories, laboratory and flow meters measurements, on a daily basis, by subjecting them to the mass balance constraint. Operation and planning decisions also benefit from the revised data. The implementation of S-TMS Production Accounting system at BRC refinery started at the end of The project took approximately a year from the kick-off to the use of the new production accounting system. Soteica's S-TMS production accounting system is now used for solving the daily refinery- wide mass balance. The BRC refinery is located north of the Port of Antwerp at the center of the ARA region on a 105-hectare site. It was originally commissioned in 1968 and acquired by Petroplus in May The refinery has a nameplate throughput capacity of 107,500 barrels per day. Fig. 1: BRC refinery ERTC Asset Max 2010, Budapest, Hungary Page 3 of 12

4 BRC products include propane and butane gas, naphtha, automotive gasoline, gasoils, heavy fuel oil and sulphur. The majority of BRC's production sold in the ARA region. The refinery includes an atmospheric distillation unit, a vacuum distillation unit, a visbreaking unit, a naphtha desulphurization unit, a catalytic reforming unit, an isomerization unit, a gasoil desulphurization unit, a sulphur unit, a naphtha fractionation unit and a liquid gas separation unit. Soteica provided and implemented the S-TMS production accounting system. Soteica is a technology company that develops, implements and sustains applications for the process industry in the following areas; Production Accounting (S-TMS), Advanced Planning and Scheduling (S-SOM), Energy Management and Optimization (Visual MESA) and Operator Trainers (S-OTS). Soteica also provides services in the area of advanced control. THE PRODUCTION ACCOUNTING PROJECT During the different stages of the project implementation a great value was captured, which included acquiring detailed knowledge of plant and tank farm operations and movements, accounting of hydrocarbon streams that were previously ignored and review of the flow meters and accounting procedures. The sponsorship of the project by the refinery management and the active collaboration of Soteica's and BRC's project teams, both in the implementation stages and afterward, were very important to the success of the project. Before S-TMS implementation, two different and separate models were used for production accounting purposes, one for the tank operations and the other for the process units. These two models had different levels of granularity in each one. The two systems were maintained separately. Results consolidation was made daily in Excel spreadsheets to perform margin calculations that were sent to the corporate office, and the results were integrated at the monthly report level, which was done at the end of the month. As a result of the Production Accounting project, Soteica implemented a refinery-wide mass balance model that is solved on a daily basis and provides the information required by the planning department. The refinery information now resides in a single system. BRC refinery model includes the processing units as black boxes and has the receipt and shipment points of the site as boundary limits. The tank farm is modeled tank by tank. All daily operation measurements and all significant hydrocarbon movements for each plant are ERTC Asset Max 2010, Budapest, Hungary Page 4 of 12

5 entered daily. The model also includes the generation and consumption of fuel gas, fuel oil, natural gas and the sulphur and hydrogen produced and consumed. Crude composition is also calculated on a daily basis. The level of detail of the modelling provides sufficient redundancy of measurements and crosschecking between measurements. The analysis is done simultaneously in the whole refinery on a tank-by-tank and unit-by-unit basis. The role of production accounting is to find sources of errors and work in a continuous improvement mode towards having an overall measurement system in the best shape possible. The reporting becomes the common information platform for the refinery s data. Best practices indicate that production accounting cannot be done automagically. In all cases the accounting and analysis phase must be done on a daily basis with human intervention. The production accountant has to be in control of the data used to achieve the goal of producing the mass balance. S-TMS is highly integrated with the existing information technology infrastructure, thus minimizing the manual data entry efforts and avoiding duplicated entry errors. S-TMS retrieves information from the data historian and lab system and imports information from the inventory database, and from the receipts, shipments and movements database. S-TMS Production Accounting System S-TMS is an application that allows to model inventories and material movements (receipts to tanks, tanks to shipment, process to tanks, tanks to tanks, etc.) most common in the process industry. The goal of this model is to capture all necessary measurement information for the calculation of inventories and material movements in a given period and to generate a mathematical model for mass balance reconciliation that, when solved, allows to detect losses, custody transfer errors and data input errors in a generalized and methodical way. S-TMS has an embedded engine for the statistical errors minimization algorithm for mass balance reconciliation. Both the traditional gross error identification method, and the successive error identification and simultaneous compensation method are available. If multiple gross errors are present in the data (the usual case in an industrial setting), the traditional gross error identification method will spread the error in a way that makes it very difficult to detect its location. Therefore, S-TMS implements a successive error identification ERTC Asset Max 2010, Budapest, Hungary Page 5 of 12

6 and simultaneous compensation method which allows for a much more precise location of the gross error (leaks, instruments bias, etc). Fig. 2: Information Flow S-TMS web client provides screens for distributed data capture, both manual and from other systems. S-TMS can import and/or export information from/to other systems, like historian, lims, erp and in-house systems. S-TMS calculates inventories for different types of tanks (e.g. API, API floating roof, sphere, bullet) and different type of available information (e.g. strapping table or geometry, bob and tape, level, gross volume, net volume, net mass, density, density from composition, number of units). S-TMS also keeps track of changes of service (material code changes) in tanks. ERTC Asset Max 2010, Budapest, Hungary Page 6 of 12

7 Fig. 3: Inventory measurements S-TMS calculates flows and movement quantities from different type of available information (e.g. source tank inventory differences, destination tank inventory differences, weigh scale data, gross/net mass, gross/net volume, etc.) Fig. 4: Flows and movements ERTC Asset Max 2010, Budapest, Hungary Page 7 of 12

8 S-TMS composition tracking module allows the calculation and tracking of the composition of a group of tanks and movements. This is typically used in refineries to track the crude unit charge composition and the crude tanks composition, but can be applied to any area of the site. S-TMS planning tracking module and pipeline tracking module are also available in S-TMS, although they were not implemented in BRC. S-TMS planning tracking module allows the comparison of planning information and actual performance data, for any type of plan (like gasoil net production, crude unit charge, fuel gas consumption, butane receipts, etc.). S-TMS pipeline tracking module allows the tracking of batches location in a pipeline. The pipeline model can include injections and extractions between pipeline segments. S-TMS Results Analyzer allows to solve cases studies and analyze gross errors and solver results. This is facilitated through different views that are color-coded. Different case studies can be created for the same period. The S-TMS Results Analyzer Campaign Studies module allows to create periods with arbitrary start time and end time that can overlap with the normal accounting periods. This is typically used by plant personnel to perform mass balance analysis around a process unit during a certain campaign or operation mode. No data entry is required for these periods, as the system will generate the input data by integrating movements, flows, and changes of materials of the corresponding accounting periods. Fig. 5: Results analyzer ERTC Asset Max 2010, Budapest, Hungary Page 8 of 12

9 S-TMS has a complete set of standard reports that include, among others, tank inventory, net production, unit yield, tank movements and mass losses reports. S-TMS Report designer allows the creation of new reports and the modification / customization of existing ones. S-TMS MS-Excel Add-in allows for data export to Excel spreadsheets. It accesses data through a set of Excel like functions that can be assigned to spreadsheet cells. Fig 6. : Sample report in pdf format Fig 7.: Report designer ERTC Asset Max 2010, Budapest, Hungary Page 9 of 12

10 Fig 8. : Excel Add-in for data analysis and reporting S-TMS is fully configurable through the use of calculation plugins, properties data sources, element versions, element grouping, and user permissions by model and period statuses. Usage parameters configuration allows detailed customization of input screens, summary screens, data sources availability and default values. S-TMS element versions are used to keep the history of the configuration of models, nodes, connections, node groups and connection groups. Each version of the element is valid for a specific period of time. This allows auditing of the results for earlier periods with no loss of the configuration information valid at the time. S-TMS tasks scheduler module can schedule the execution of scripts at a given date and time (like run a report, a connector, create periods, run reconciliation, run database backups, etc). S-TMS command processor allows to execute a set of commands (like create a measurement, create a movement, etc.) defined in a text file of predefined format. PRODUCTION ACCOUNTING PROJECT BENEFITS During the model building phase, the project team gained a detailed knowledge of the plant operations and the tank farm movements and calculations. All existing accounting procedures were reviewed and improved in order to gather the information required to perform the daily mass balance. Afterward, when S-TMS was used on a daily basis, exceptions were caught that otherwise would have been ignored. As a result of the implementation of S-TMS the following benefits were detected upon the implementation of the new production accounting process at BRC refinery: ERTC Asset Max 2010, Budapest, Hungary Page 10 of 12

11 Inventory calculations are improved, particularly for floating roof tanks correction and for heavy hydrocarbons VCF factor. Sulphur tank inventory calculation has been also added to the model. Flow meters calculations are improved, as S-TMS performs temperature correction for flow meters readings available at flow conditions. It takes significantly less time to produce a more accurate balance with S-TMS than with the previous system. The successive error identification and simultaneous compensation reconciliation method points in direction of unreliable flow meters, and missing oil movements. Incorrect densities for tanks are flagged up in daily mass balance reconciliation with measurement corrections of significant impact. This allows to act promptly to amend incorrect densities, resulting in more accurate Stock Reporting. Also, as S-TMS can read densities from the lab system, inventories can be recalculated if new results from the laboratory are available at a later time. S-TMS production accounting system helps bring to light and analyze systematically any discrepancies between the daily recorded receipts and shipments and those calculated by the midnight tank gauging, which are especially difficult to estimate accurately for ongoing operations. S-TMS points out the meters that need to be calibrated. This allows managing and sustaining a more focused instrumentation maintenance program. S-TMS validates the movements coming from the in-house tank movement system while importing them, performing a simultaneity analysis that helps identifying wrongly estimated quantities in early stages. Graphical presentation of the model is a vast improvement. Results analyzer graphic presentation helps understand the plant operations and movements of the day and find possible errors by displaying a color coded flow diagram and different views that help analyze the information. S-TMS crude composition calculations are a huge improvement on previous method of calculation. Crude composition is also tracked, in detail, within another dept. This information is also required for external reporting to Belgian authorities, and historically has always differed from the crude composition for mass balance ERTC Asset Max 2010, Budapest, Hungary Page 11 of 12

12 accounting. Since the implementation of STMS, these differences are no longer apparent, and all departments have confidence in S-TMS crude composition reports. Reports are used by different areas of the refinery and are also sent to the corporate office. Most of shared files with corporate systems are produced in Excel, so the capability to produce S-TMS in this format is a great benefit. All amendments to uploaded, (corporate), info, are performed in a much speedier manner than previously. Excel add-in has proved to be a very useful tool when wanting to access historical data for large periods of time. Refinery loss calculations are done in S-TMS, replacing the calculations done previously in several separate subsystems, which allows quicker calculations of the daily or monthly loss values. Loss calculations are used for monitoring inventory and receipts and shipments data entry errors. Errors in daily data entry appear as larger than expected daily gains/losses. S-TMS has proven to be flexible and very user friendly. The model is easily Conclusions maintained and modified by the planning department including changes such as: creation of new meters, new tanks, new movements and even new process units. Data entry screens are easily customized to include new historian tags, default values and new laboratory measurements. A refinery wide mass balance production accounting system is the first step towards a loss control initiative. In addition, it provides useful information for the continuous improvement of the overall measurement system and generates widely accepted results for the yields of the units individually as well as the refinery as a whole. Bibliography Oscar Santollani, Diego Ruiz, Marcela Brina, Goran Serka. ERTC, Asset Maximization Conference, May 2008, Lisbon. Refinery Production Accounting - Making all your measurements mass balance". The BRC Refinery - Petroplus holding Corporation, 2006 Petroplus Holdings AG < ERTC Asset Max 2010, Budapest, Hungary Page 12 of 12