- A control system for turbomachines on an open platform that allows gas to be recycled inside the compressor avoiding flares, with optimization of costs and profits, both in the greenfield and brownfield.
PlantPAx Modern DCS
- Automation of turbomachinery control system based on integrated Allen-Bradley ControlLogix configurable algorithms
- Energy savings
- Higher efficiency
- Increased profitability
The sight of a blaze in the night, when you pass by a refinery, has something fascinating about it if you don’t stop to think about what’s behind these flares. We all perfectly understand that this, like any combustive phenomenon, is in fact polluting the atmosphere.
A more in-depth analysis about the operation of these plants would lead us to the conclusion that the energy wasted in this way could be exploited.
The increasing attention shown in recent times by many companies with regard to efficiency and the reduction of plant management costs, in addition to greater sensitivity to environmental sustainability policies, should lead to a gradual decline of these flares.
But how do you minimize a phenomenon that causes serious harm to the community and denies the company the opportunity to make the best use of its resources?
As often happens, the solution to the problem is not so complex and is characterized specifically by a cost/benefit ratio decidedly in favor of the latter.
Having a turbomachine control system that allows the recycling of the gas produced by the compressor running the turbine means the ability to reuse an energy resource that would otherwise have to be combusted, creating a flare. A system that translates into tangible benefits in terms of reduced energy consumption, improved productivity and asset use and, last but not least, reduced environmental pollution.
Chemical engineering and technology to increase profitability
Energy Control Technologies, in short ECT, was established in the United States about a dozen years ago and for three years it has been operating its own subsidiary in Europe. The company has focused its activity on the control of open-platform turbomachinery, specializing in applications, know-how and control algorithms for large rotary compressors for industrial plants, whether axial, centrifugal, steam turbines, gas turbines or turbo-expanders.
It is a niche activity that plays a role in industrial automation applications and is based on the creation of very complex algorithms that, taking into account the thermodynamics of the gas inside the compressors, avoid the need to burn a flare, ensuring energy efficiency not only for the compressor but also for the machine and the entire system. Such systems require extremely high levels of processor scanning response rates from the hardware point of view, around 30/40 milliseconds, and find their ideal application when integrated within a compressor control system.
ECT has found these features in Rockwell Automation, for which it has been an OEM partner for over ten years, recognizing the Allen-Bradley® ControlLogix® programmable automation controller (PAC) as its most historic, reliable and benchmarked hardware installation, with the added value of seamless integration with the PlantPAx® distributed control system.
Proprietary vs. open platforms
About 30 to 40 years ago, when this market niche was developed, PLCs on the market did not offer the required performance and this meant that for anti-surge functionality the industry developed proprietary hardware platforms on which the software was installed. Although this is not an optimal situation, because it creates a close dependence between the company and the developer of the black-box solution, this type of technological landscape is still quite frequent; for example, in terms of costs and service time in the event of failure or the handling of spare parts intended only for that unit.
By providing configurable, nonprogrammable control algorithms for turbomachines installed on open hardware platforms, with a preference for Rockwell Automation ControlLogix, ECT is successfully helping to eradicate this practice based on its customers’ reported benefits. The choice to provide configurable and nonprogrammable algorithms means that the core of the algorithm is sealed and cannot be changed. For example, the 600 configuration parameters to run the basic surge control algorithm on a specific machine or plant, create a repeatable process that is perfectly documented and therefore absolutely independent from whoever developed it. This allows it to be maintained over time because it is based on the same building blocks that are well documented and therefore can be replicated project after project.
A best practice project
An example of this is the project carried out by ECT and Rockwell Automation for an OEM operating in the Czech Republic who has built a compressor for a Slovakian Oil & Gas company. It is a compressed ethylene gas application and specifically a plant unit on the main refining process. Although this unit is not essential for refining and does not have any impact on the operation of the plant in the event of its shutdown, it represents an improvement which greatly increases the productivity of the refinery. In a highly competitive industry such as refining, the exploitation and partial reuse of material obtained from process waste and the consequent increase in productivity make the availability of these satellite plants particularly important, as they have a strong impact on the profitability of oil and gas companies.
In this project, an electric motor has been installed with a two-stage compressor controlled by valves whose opening/closing function allows for the regulation of gas flow, as well as pressure and temperature. The control system is based on a ControlLogix PAC for the anti-surge functionalities, with valves controlling the passage to each stage in order to avoid uncontrolled increases in temperature and gas pressure that would compromise the compressor and risk melting it. The system also includes control loops with wedge controllers that inject cold gas into the recycling line to compensate for overheating with early valve opening based on ethylene transformation curves. All of this has been achieved by integrating the compressor control system, managed through Rockwell Automation’s PlantPAx DCS.
A distinct characteristic of this project is the use of the ControlLogix multi-processor architecture. Where a compressor control system using Rockwell Automation solutions is already in place, it is particularly useful to integrate an additional CPU dedicated to the ECT algorithms for the anti-surge. In this way, the two systems, although perfectly segregated as each has its own CPU and I/O card, coexist on a single PAC and create a fully integrated solution for machine control and anti-surge management, overcoming the dichotomy represented by hybrid situations where the anti-surge function is managed with black box solutions completely disconnected from the compressor control system.
In the case of the Slovakian oil & gas company, the project was created from scratch, but such a solution is also perfectly applicable to existing plants, where proprietary platforms for anti-surge can be replaced and integrated into a single control environment represented by the existing PlantPAx system. This integration provides access to all the native analytics capabilities of the PlantPAx distributed control system to improve, for example, predictive maintenance strategies and minimize downtime.
The results mentioned above are specific to ECT’s use of Rockwell Automation products and services in conjunction with other products. Specific results may vary for other customers.
Partner Company Statement
Energy Control Technologies (ECT) delivers control solutions for turbocompressors, steam turbines, gas turbines, turboexpanders, screw compressors, reciprocating compressors, and centrifuges. ECT solutions increase energy efficiency and production while improving machine protection.
ECT Solutions include surge control, performance control, loadsharing, steam turbine speed and extraction control, gas turbine fuel control and sequencing, turboexpander control, vibration protection, plant air network control, simulation services, and centrifuge control and protection systems.
Published December 28, 2020