AN OPTIMIZATION PROGRAM AT LYONDELLBASELL

Size: px

Start display at page:

Download "AN OPTIMIZATION PROGRAM AT LYONDELLBASELL"

Silas Banks
6 years ago
Views:

1 AN OPTIMIZATION PROGRAM AT LYONDELLBASELL James Hackney Senior Advisor Equistar Chemicals, LP, a LyondellBasell Company Abstract: LyondellBasell has undertaken a project in optimizing the feedstock purchasing, planning, scheduling and execution functions in our olefins business. After working to understand our existing business, dataflow and workflow processes, we undertook a study in what those processes should look like. In other words, how should we do our business? That led to scoping out over a dozen subprojects and a redesign of the business processes, which included resource requirements and job descriptions. The subprojects included implementing new tools, revamping some existing ones, and developing others from scratch. Each subproject planned for infrastructure, implementation, training and long-term support. One of those subprojects was a multi-site program in implementing Real Time Optimization (RTO) and Advanced Process Control (APC). This paper discusses how the business requirements were translated into a subproject scope, how that scope was executed, some results, and some lessons learned.

2 INTRODUCTION LyondellBasell s subsidiary Equistar Chemicals, LP has six North American ethylene production sites, with a nameplate capacity of 10.7 Blb/yr. They are located in Channelview, Chocolate Bayou, La Porte, and Corpus Christi, TX, and also Morris, IL and Clinton, IA. Three of the facilities primarily crack ethane and propane, and the other four sites primarily crack liquids, though they can crack some amount of Natural Gas Liquids (NGL) as well. Table 1 gives a summary of the plants. Each site is unique, using slightly different ethylene cracking technologies, differing in size and products. There is considerable capability to transfer intermediate products between plants. Some sites have Hydrocarbon Recovery Units (HRU), producing such products as benzene, toluene, and butadiene. Table 1. Equistar Chemicals U.S. Olefin Plants Site CVO LPO CPO CCO CLO MIO Location Channelview, TX (2 plants) La Porte, TX Chocolate Bayou, TX Corpus Christi, TX Clinton, IA Morris, IL Startup 1976, C2= Capacity [1] 3.85 Blb/yr 1.74 Blb/yr 1.2 Blb/yr 1.7 Blb/yr 0.96 Blb/yr 1.2 Blb/yr Technology Lummus Kellogg/Linde Lummus SWEC Kellogg Lummus Feedstock To 90% Gas Oil NGL + Light Naphtha To 100% Gas Oil To 90% Gas Oil Ethane/ Propane NGL HRU? Yes No Yes Yes No No Considering our flexibility, we undertook a study as to how our ethylene business processes should be set up and communication mechanisms between the different parts. That led to scoping out over a dozen subprojects and a redesign of the business processes, which included resource requirements and job descriptions. The subprojects included implementing new tools, revamping some existing ones, and developing others from scratch. Each subproject planned for infrastructure, implementation, training and long-term support. One of those subprojects was a multi-site program in implementing Real Time Optimization (RTO) and Advanced Process Control (APC).

3 DEVELOPING APC & RTO SCOPE The purpose of the APC and RTO subproject was to provide the process automation necessary to ensure the proper execution of the plan. The plan is produced by the olefins optimization and operations planning group. It identifies the feedstock allocations to the plant, the constraints the plants should generally run against (which can include marketing or logistical constraints), and the price deck. The price deck includes breakeven feedstock prices and incremental product prices. The APC and RTO scope was thus limited to those applications that support the plan. For example, a plant might have a propylene fractionator that is not a plant throughput constraint. Even though APC on such fractionators generally make significant money, it would not have been considered in this case for a new or revamped APC application. The primary focus was on those applications that historically have been plant throughput constraints. The other applications could be justified on their own merits. It is vitally important then that the APC and RTO push against the right constraints. We sought to achieve this by using: Consistent models Consistent prices Consistent limits The right process data The right feedstock composition The right tuning It was obvious that each olefins plant needed key advanced controllers and feed maximization. Each of our plants already used DMCplus to one degree or another. We needed to make sure that the existing applications were sufficient to achieve our goals and to install any new necessary applications. Some applications were so old, but running well, that the long-term support was in question; these applications were to be revamped as well. We had three rigorous RTO applications (Aspen Plus Optimizer): two in Channelview and one in Corpus Christi. The Corpus Christi RTO also included simplified models of the Hydrocarbon Recovery Units (HRU), since these can sometimes constrain the olefins plant feed. That brings up the important point that the planning models may be constrained outside the olefins plant. In the case of Channelview, with its two crackers and HRUs, the planning model may be solving a different problem than individual RTOs. The RTO needs to solve a problem that is consistent with the problem the planning model solves. We decided to use a simplified RTO approach [2] that would encompass both olefin units and the HRU. The simplified RTO uses rigorous models on the furnace yields (SPYRO ), rigorous charge gas compressor models, and flash drums for the feed separators. All other models in the RTO are either component splitters or DMC-type models (EODMC). The HRUs are modeled similar to the planning model. In addition, steady state targets from DMCplus are used to feed data into the RTO, which allows the optimizer to run more frequently, about every 30 minutes in our case.

4 The advantages of the simplified optimizer include: Low cost Higher execution frequency More robust in solving Flexibility to add rigor later Another advantage is that the simplified model structure can be aligned with the planning model quite readily. Of course, the simplification comes with a price. There are parts of the plant that are not rigorously modeled, and the optimizer cannot solve certain problems in those areas. An example is the optimum ethylene loss in the Demethanizer overhead. Such problems will have to be solved offline. Simplified optimizers also rely heavily on the underlying APC applications. Back-end nonlinearities are another issue. For us, however, the advantages outweighed the disadvantages for what we wanted to do in supporting the plan. Rigorous Optimizer Simplified Optimizer w/ selected rigorous models Simplified Optimizer SPYRO AspenPlus Predict, Measure, Reconcile Feed Maximizer APC Linear Program Predict everything Regulatory controls Measure everything Figure 1. The Spectrum of Modeling Rigor The RTO works with the APC which works with the DCS and instrumentation. With the simplified RTO, the integration and consistency with APC is crucial. The integration and consistency with the planning process is just as important. An optimizer with the wrong set of prices may lose as much money as it makes. The planning, RTO, APC and DCS must all work as a system and that system must be robust and supportable.

5 Planning Process constraints, offsets RTO Watch Aspen Watch The Plan limits RTO DMC/CLP constraints, prices targets SP s feedstock composition Scheduling Monitoring System DCS / Instrumentation IP.21 Figure 2. The Planning / RTO/ APC / DCS System The Chocolate Bayou plant already had a project underway to implement key APC and a simplified optimizer [3]. After reviewing their scope during our scoping stage, it was realized that it was a near perfect fit with what we were doing. Since their project was already underway we did not want to delay it, and so it remained a stand-alone project and has become our prototype. The Corpus Christi olefins plant had already completed their RTO and APC. Again, it fit nicely with what we were doing, and so the scope for that site was rather limited. Finally, other important items that focused on long-term needs were included in the scope, instrumentation was added and operator training materials and documentation was developed. Three levels of monitoring systems were implemented (DCS loop monitoring, APC application monitoring, and RTO monitoring). A control engineer was hired and of course, new computer servers (26) were needed. The schedule initially had the APC and RTO work completing in a little over a year, which was dependent on parallel work at four major sites.

6 EXECUTION AND TRACKING Two APC/RTO contractors were used in this work and several controllers were revamped internally. It is vitally important to distribute responsibility in such a program. Each site had an Equistar lead for the APC work, and similarly, an RTO lead. The contractor in both APC and RTO had leads. In addition, a central control engineer was assigned to each site. It was the responsibility of the site lead to manage the work and contractors. However, when disagreements arose, or technical questions developed, the issue could be taken to the Technical Steering Committee. This committee was made up of a contractor and Equistar employees, and its purpose was to resolve technical issues. Consistency between sites was an important consideration of the team. Project Steering Committee Commercial Governance Technical Steering Committee CVO DMC LPO DMC CLO DMC MIO DMC CVO RTO LPO RTO CLO RTO MIO RTO Figure 3. APC Project Structure With such an undertaking, several problems naturally occurred: Turnarounds, outages and shutdowns DCS conversion project Reduced plant feed Personnel changes Resources pulled Instrumentation problems

7 Plant equipment problems Other projects preventing APC work To keep up with all the activities and changes, weekly phone conferences were held for the APC work for each site, and bi-weekly calls for all the RTO work. The site leads and contractor leads both participated. Additionally, the contractors submitted weekly reports that included progress, action items, issues, and schedules. The APC and RTO technical lead submitted bi-weekly reports to the overall project lead. As can be imagined from the list of external problems, delays were inevitable. Whenever potential schedule issues arose, we tried to swiftly come to a resolution. Since the contractors were not always dedicated solely to this work, sometimes issues arose in getting the resources back after an Equistar caused delay, resulting in further delays. Quick, open dialog proved essential in resolving these issues. Supporting infrastructure was also important. Not only were new instruments added, but new computer servers were as well. New automated mechanisms were developed and implemented in getting pricing information from the planning group to the RTO. Mechanisms for getting feedstock information to RTO were also needed. Interim solutions were required when other systems were not ready. Systems were also implemented to increase the visibility of the controllers and optimizers and their key performance indicators (KPI). It is important to keep track of the progress, issues, action items, spending, milestones and schedule. Spreadsheets were used primarily for that purpose. 100% OOIP APC Execution Progress 90% 80% 70% Percent Complete 60% 50% 40% 30% 20% 10% 0% 1/1/2006 4/11/2006 7/20/ /28/2006 2/5/2007 5/16/2007 8/24/ /2/2007 3/11/2008 6/19/2008 Date Figure 4. Subproject Progress Chart

8 RESULTS One very positive aspect of the project was that it enjoyed lots of support throughout the company. Of course, that also meant managers were paying close attention to how the project was being run and its results. The APC and RTO subproject was successfully executed, though some items remain to be completed as there are future enhancements and improvements left to be done. Not all aspects of the project went smoothly. Instead of one year, it took us over two years to finish the work. Some controllers turned out to be more difficult than others, and some had to be reworked. There were also numerous delays due to turnarounds, outages, shutdowns, and resource availability. Some pre-test work had to be redone. The following list summarizes what was done: The system was developed and put together (RTO, feed maximization, APC, DCS, instrumentation) to support our planning and olefins business processes. We commissioned 51 DMCplus controllers and 5 feed maximizers. We commissioned four new simplified RTOs. One of those included the entire olefins complex (two olefin units, C4 recovery (butadiene), C5 recovery (isoprene), aromatics recovery, alkylation, etc.) in one model. We installed 28 new transmitters and many existing instruments were repaired. (One valve remains to be replaced, awaiting a turnaround). We made systemic changes to some of our regulatory control practices. We developed new systems for getting price and liquid feedstock information to RTO. We developed APC and RTO training materials and trained operators and engineers. Twenty-six computer servers were installed. We justified and hired a new process control engineer. We added a new position in central process engineering to support RTO and material balances across sites. We managed two APC contractors and did several DMC controllers in-house. Over 100 people participated in the subproject (not including board operators). With all of the work done in this project, recognition of the contributions of people was essential. The sponsors (vice-presidents) and core team members went to all the sites to recognize the supporting folks with gifts and heartfelt thanks. BENEFITS The APC and RTO work was not justified separately from the larger project, but rather, its infrastructure for the whole olefins business and planning process. That is not to say that each site did not get extra benefits; APC and RTO applications make money in their own right. That said, here are some of the observed benefits: When not furnace limited, the feed maximizers put more feed in and can run against backend constraints. With new and repaired instrumentation, furnaces can run at lower oxygen. Variability decreased, and we can run closer to spec in many cases.

9 There is much more consistency in the control of our olefin plants. For example, each plant has the RTO Feed Maximizer APC structure. Engineering limits were critically examined and set. Energy usage has decreased with the APC applications. CHALLENGES AHEAD Having created this infrastructure means that we now must sustain the benefits. There are several challenges in doing that. Keeping instrumentation in good working order is a significant challenge. Yet it is crucial to sustain the benefits. Preventive and predictive maintenance can help, as can smart transmitters. However, the maintenance system must be in place for those technologies to work. Diligence in maintenance is essential. Keeping APC and RTO limits set properly can be a challenge over time. We have set up processes for job functions, such that, if the control and RTO systems are not pushing against the right constraints, it should get noticed and communicated. Keeping skills up can be very difficult when personnel changes are frequent. From the time we started the project, some sites experienced three different RTO engineers. We developed operator training materials but we need to put more emphasis on training our support people. We must demand that the APC, feed maximization and RTO be functional and in good working order. Operations should take ownership of the APC and if it does not work properly, they should demand it be fixed, instead of simply turning it off and leaving it at that. KPIs can help focus management s attention. LESSONS LEARNED With a project of this size, there are bound to be many lessons learned, things done right and things done wrong. The following is an unorganized list that tries to capture these lessons: Pretest work should be done by the same people who do the step testing, modeling and commissioning. Pretest just before step testing. We contracted pretest activities over a year before some of our step testing. Things had changed, and in some cases we had to do another pretest before step testing. Be very clear in the statement of work for the contractor. We thought our methodologies were essentially the same as the contractor when we developed the statement of work document. It turns out however, that some were different enough to cause issues. Track issues and progress and set up tracking mechanisms early. Try to be thorough. If the contractor is giving written reports, have them be in the format that makes it easy for you to track progress and issues. Track the following: o Scope (I tracked the percent complete for each payment milestone) o Action items

10 o Issues to be resolved o Delays - make sure you track the time and cause Weekly site status calls - since we were doing work simultaneously at various sites, we had a weekly conference call per site. These were scheduled for 30 minutes. Additionally, we had an RTO conference call for all sites bi-weekly. Save everything - create a shared folder, and put some structure into it. Address training - operators and engineers need to be trained on new or revamped applications. Long-term training needs should be addressed as well. Site technical leads and backups that were new or new to the technology needed training also. Make sure you have experts or super users on staff when the program is complete. Prepare for known conflicts, such as turnarounds and outages. For programs that take significant time, watch out for resources being pulled for other purposes. This includes internal and external resources. For distributed programs, assign a lead and backup for each site s APC and RTO work. These people are responsible for the work at the site. The overall lead needs to communicate often with the site leads and address issues that cannot be resolved locally. The technical steering team helped to resolve technical issues and conflicts that affected multiple sites. Some technical best practices were addressed by this team. Watch out in lump sum bids for not in budget conflicts. The statement of work needs to address this. After this project, I have much more respect for RTO engineers and their skills. Understanding business and work flows was very beneficial. The contractor matters - this applies to skills, experience and resources. Standardize wherever it makes sense. Delegation and multitasking is necessary! Plan for the unexpected. What will you do if the plant shuts down? What if key instrumentation does not get installed in time? Make sure you include long-term support personnel in your plans and make sure training is available. If it doesn t work in simulation, it won t work in the real plant. Operations should take ownership of the APC applications. When they are not working properly, operations should demand they be fixed. RTO needs to solve a problem that is consistent with the problem the planning model solves. Recognition can come in many forms, including gifts, but a sincere, personal, handshake and thank you from management (as high as you can get) goes a long way. People make the difference.

11 CONCLUSION As part of a large, multi-site project of optimizing Equistar s olefin business processes, a subproject of implementing RTO and APC was executed. The scope of the RTO and APC was developed specifically to support the planning and business processes. Though there were many challenges, over 100 people helped make the vision a reality. There were many lessons learned, but there are still challenges ahead to ensure that the benefits of the APC and RTO infrastructure are sustained.

12 REFERENCES 1. From Industry Info website. Ethylene only Shindo, H., et al., Furnace Optimizer in a Naphtha Cracker, Ethylene Producers Conference, New Orleans, Louisiana, April Rickard, K. A., et al., Some Key Issues on a Successful Application of a Real-time Optimization System at an Ethylene Plant, Ethylene Producers Conference, Houston, Texas, April 2007.

Simplify APC Tuning and Configuration

WHITE PAPER Simplify APC Tuning and Configuration Advanced Process Control Tushar Singh, APC Product Marketing, Aspen Technology, Inc. Lucas Reis, APC Product Management, Aspen Technology, Inc. Introduction