Chemical production grew in every region of the United States during 2016, according to the American Chemistry Council (ACC). Furthermore, the ACC predicts that growth will translate into more than $1 trillion in chemical revenues by 2020. At the same time, the U.S. Energy Information Administration’s 2017 outlook report forecasts that refinery production will increase by more than 20 percent from 2016 through 2040 — largely due to increasing production volumes of renewables, natural gas and crude oil. With a growth trend expected to continue on an upward trajectory, petrochemical and refinery companies are sure to look for solutions by which to increase operational efficiencies and reduce downtime.
Used after process heating operations, temporary cooling solutions such as cooling towers, chillers and air conditioners provide significant benefits. They allow petrochemical and refining companies to avoid project delays and improve their balance sheet by avoiding high cost capital expenditure (CAPEX) commitments on short- to mid-term duration needs.
When considering a temporary cooling system, it is important that the equipment matches the specific demands of the environment. Each downstream project is unique and has different needs, so there is no such thing as a one-size-fits-all approach. Therefore, it is critical to work with a temperature control provider that understands how to design a system that effectively ties into an existing process.
Petrochemical and refining companies worldwide are benefiting from the cost savings and operational efficiencies that temporary cooling solutions can provide. This article describes three applications in which temporary temperature control solutions were deployed in the petrochemical and refining industry to restore vital project cooling needs. The temporary solutions allowed the plants to maintain economic gains and operational productivity.
Maximizing Ammonia Summer Throughput
The process for producing ammonia requires a hydrogen/nitrogen mass feed-rate ratio of exactly 3:1. If either of these mass flows cannot be maintained at an appropriate flow rate consistent with this ratio, then ammonia production will suffer proportionally. The nitrogen required for the reaction comes from the nitrogen contained in air and enters the reactor via a large compressor.
During the summer, air becomes less dense as the ambient temperature increases. Because a compressor is a volumetric machine, the air-mass flow-rate drops inversely in proportion to the outside temperature. In this case, the air-mass flow-rate decreased during peak summertime temperatures to 43,000 lb/hr, with ammonia production dropping proportionally. This is in contrast to the wintertime, when the producer was able to sustain the maximum air-mass flow-rate of 50,000 lb/hr into the reactor.
One method of increasing air throughput to wintertime flow rates is to increase air density by cooling the air entering the compressor suction. In fact, this producer had already put into place an inlet air-cooling system. However, it proved unreliable and could not consistently increase airflow rates. This situation forced the ammonia producer to begin searching for a solution that would consistently maximize air-mass flow throughout the year.
A specialized group of process engineers evaluated various scenarios for providing the required cooling, and they recommended a staged solution. The ammonia producer’s configuration draws ambient air into a filter housing and then directly into the compressor suction. Therefore, in order to minimize system changes, the third-party engineers designed an intake air-conditioning system that cooled ambient air. The ambient air leaves the filter at 50 to 55°F (10 to 13°C) and enters the compressor suction. Special provisions then were designed into the system to minimize compressor-intake pressure drop.
After implementation, the producer was able to increase ammonia production by 38 metric tons/day due to an increase of air-mass flow of approximately 5,550 to 7,500 lb/hr. This solution consistently maintains an air-mass flow-rate between 48,000 to 50,000 lb/hr — even at peak ambient temperatures of 100 to 105°F (38 to 40°C).
Process Cooling of Diluted Bitumen
A large sustainable-energy company was facing a high temperature challenge at its tank-farm facility, located near its main operations north of Fort McMurray, Alberta, Canada. The tank farm provides cooling and blending of hot bitumen to produce diluted bitumen (also called dilbit) for the company’s downstream customers.
The producer anticipated that the facility was at risk of being unable to adequately cool diluted bitumen below the required temperature needed to avoid flashing of light-end vapors. High dilbit temperatures would require a reduction in flow to the tanks just when the operator required the storage and processing capacity the most. Without a cooling solution, the producer faced potential impacts to its operations, including a reduction in facility throughput.
The energy company called in a third-party provider of temperature control solutions that had experience in cooling heavy hydrocarbons and executing the rapid development of temporary projects. A scope review process kicked off the project. Numerous components of the design and engineering phase were studied to simulate and evaluate potential solutions, and to determine the final process system and utility equipment needs for operation. As a result, several deliverables for the project were developed and provided to the producer, including:
- The conceptual process design of the trim cooling circuit, including thermal and hydraulic models.
- The mechanical and electrical process requirements of the project, including utility needs.
- A cooling process control philosophy, including equipment configuration diagrams.
- A conceptual project layout based upon the determination of what equipment would be necessary to accomplish the task.
- The final process design package, including overall project scope, engineering data and simulations that validate the installed project would meet the producer’s needs.
Upon completion of the scope review and project definition and engineering stages, the bitumen producer decided to have the project designed and installed to a standard that would permit for potentially long-term use in a plant environment. For example, the glycol loop connections would be hard piped, and a cable tray would be used to run cable between electrical gear. Due to the growing complexities of the project, the bitumen producer contracted a Canadian engineering, procurement and construction (EPC) management firm to undertake the engineering and construction phases.
A specialized team of engineers were tasked with the responsibility for technical support and project-management counsel. Key tasks included oversight of power generation and temperature control equipment delivery to the site, and supervision of work efforts with the EPC to ensure equipment was safely and efficiently installed and commissioned.
The temperature control solution, including 4,000 tons of cooling equipment energized by 6 MW of power, was installed by the project partners. The solution currently remains in operation at the bitumen producer’s facility. It successfully provides cooling of up to 192,000 bbd of dilbit from 134°F to below 100°F (57°C to below 38°C).
Preventing Damage to a Continuous Catalytic Reformer
The continuous catalytic reformer (CCR) in a refinery connects naphtha-grade material with hydrogen in a series of reactors that contain platinum catalyst. This reaction increases the octane value of the naphtha feed stream so that it is suitable to be blended into the gasoline pool. One of the side reactions, which reduces yields, is the cracking of feed materials into light hydrocarbon gases. Thus, the purpose of a low pressure separator is to remove as many of these lighter hydrocarbons and hydrogen gas from upgraded naphtha hydrogen gas. However, if there is not enough cooling in the low pressure separator, then heavier hydrocarbons will remain in the recirculated gas. This can cause process problems downstream of the low pressure separator.
A Midwestern refiner was experiencing condensation of heavier hydrocarbons in certain portions of the recycle-gas circuit. This caused a $50 million loss due to significant production downtime and maintenance costs involved with shutting down the CCR in order to fix the recycle-gas compressor system. This issue was significantly worse during the wintertime when portions of the recycle-gas piping were exposed to colder ambient temperatures, which facilitated condensation.
In order to avoid more damage, the refiner needed a solution that could successfully condense heavier hydrocarbons in the separator rather than the downstream piping.
A temperature control expert proposed a solution whereby they used the existing exchanger. However, instead of using plant cooling water as a cooling medium, a glycol solution would be recirculated from an air-cooled chiller. The proposed solution reduced the gas inlet temperature from about 250 to 40°F (121 to 4°C) at a design duty of 4.3 MMBTU/hr. A final conducted analysis showed that the maximum duty achieved 4.87 MMBTU/hr —13 percent higher than the project design duty.
In conclusion, the applications described are just a few of many regarding temporary cooling solutions. Such solutions can help the petrochemical and refining industry mitigate operational hazards, minimize CAPEX spending and ensure optimal production uptime. The maximum benefit of these temporary systems can best be realized by partnering with a provider with technical, engineering and project-management expertise. Such providers can execute a customized, scalable turnkey solution for short- and long-term needs.
Putting Temporary Process Heating and Cooling Equipment to Work
Emergency shutdowns in the petrochemical and refining industries can be handled with temporary solutions such as power rental, heating and cooling and compressed air solutions to help maintain seamless operation. A provider with the technical, engineering and project-management expertise can help execute a customized and scalable turnkey solution to meet your needs by offering:
- Process optimization, engineering and design.
- The ability to engineer solutions to improve the bottom line.
- A large fleet of portable, modular cooling towers.
- Seasonal and supplemental process cooling.
- Rapid emergency response.
- Temporary utilities during shutdowns and turnarounds.
- Vessel cooling to increase production through process de-bottlenecking.
- A network of local service centers.
- A range of generator rentals for temporary power needs.
- Environmentally compliant equipment.
- Thermal discharge temperature relief.
Petrochemical and refining solutions should include:
- Addressing seasonal process cooling limitations.
- Providing low temperature refrigeration systems.
- Emergency cooling tower replacement.
- Temporary cooling during repairs and turnarounds.
- Environmental compliance.
- Disaster recovery support.
- Supplemental air to process units.
- Process and operational de-bottlenecking.
- Emergency response for unplanned process and utility outages.
- Utilities for short-term research and development production runs or qualifications.
- Improving equipment reliability.
- Qualified professional process engineering team and support.