1 September 2022
By Washington Wang, Senior Sales Manager
The PTA Industry
PTA is an abbreviation that is short for Purified Terephthalic Acid. This important bulk-chemical, raw material is commonly used as the main component in the production of polyester fiber, polyester bottle flakes and polyester film. These products are widely used in chemical fibers, light industry, electronics, construction, and other everyday items that are a critical part of the global, and national economy.
The PTA production process can be divided into two parts: the oxidation unit and the hydrogenation refining unit. Raw material PX (P-Xylene) is treated with acetic acid as the solvent, oxidizes into crude terephthalic acid under the action of catalyst, and then crystallizes, is filtered, and dried into crude products. Crude terephthalic acid is hydrogenated to remove impurities, and then recrystallized, centrifuged, separated, and dried into a final and purified PTA finished product.
New Industry Trends & Challenges
In recent years, the PTA market has changed with the emergence of several new trends. First, the industry value chain continues to extend gradually into both upstream and downstream segments, including integrating into both refining and chemical units. As a result of integration, the concentration of PTA capacity has overall been improved. Larger industry enterprises have been able to leverage the scale, while smaller enterprises are facing challenges. Further development of technology in single-line production has increased output from historic rates of 1.0 million tons/year, to current rates of 2.2 million tons/year. The next generation of technology promises output ranging from 2.5-3.0 million ton/year, already in development and continuing further expansion.
These new trends together present new challenges for plant equipment, including pumps and valves, to manage greater flow capacity with less energy consumption, and higher overall efficiency from both stable performance as well as precise control and regulation. Some of the most severe and critical applications in the plant can be found at the tank bottoms, where harsh conditions make smooth operation and precise control an even bigger challenge. Failure to meet these demanding requirements can result in unplanned plant shutdowns and huge losses of production and profits.
This article addresses these harsh applications, applying lessons learned and introduces the Masoneilan™ 75000 Series: a severe service tank mount level control valve using the most recent technology developments in additive manufacturing and advanced digital diagnostics.
Masoneilan, Brand History in Advanced Control Valve Innovation
Founded by William Mason in 1882, Masoneilan control valves have long been a leading solution in control technology for over 140 years. Starting with the earliest development of steam regulators in the late 1800’s, the Masoneilan brand has been the first to industry with many innovations such as the first quick-opening single-seat control valve, the first eccentric rotary valve, and the first adjustable Cv micro flow valve. Throughout history, Masoneilan has not only delivered superior control valve products, but has also pioneered the science behind them including developing the method for calculating the Cv value (flow capacity) of a valve, the valve noise prediction method, and the FL pressure recovery coefficient within a control valve.
Today, Masoneilan remains a global leader in flow control performance across the world. Millions of installed control valves are widely used in the largest Oil & Gas segments, including refining, petrochemical, chemical, and LNG. Specialty application in PTA, fertilizer, and coal chemical are commonplace for general service and specialty valves that are unmatched in performance, as well as in the thermal power and nuclear power segments where custom solutions are the market standard.
The Masoneilan brand is part of the Baker Hughes’ portfolio of industry leading products, providing unique access to some of the industries greatest engineering talents and centers of design innovation. Leveraging the latest technology and patents available to the market, Masoneilan continues to lead in today’s key areas of development such as additive manufacturing and digital asset management, such as advanced control & diagnostics.
Next Generation PTA Valve Development
Thanks to a rich history and research investment, Masoneilan is widely recognized by process industry customers as a leading brand in the field of control valves, and more specifically severe service and specialty application control valves. PTA applications, such as tank mount level control angle valves, are prime examples of this scenario as the process medium contains particles with high corrosion, high oxidation, as well as high temperature and pressure that demand specialty solutions.
The specialty valve design must look at the full range of operating conditions. Designs typically start with material selection, along with design and structure to ensure fit for service for corrosive fluids, as well as the high velocity and erosive particles within the fluid. Upon satisfying these requirements, the valve must then be designed to manage the high temperature transient conditions and include a robust trim design to manage the high pressure drop. All process variables drive strict requirements and careful consideration, otherwise operating life can be minimal.
Masoneilan has a large portfolio of valves capable to manage the service for multiple applications in the PTA process. Often, the 35002 Series Camflex, 21000 Series single port globe valve, or 41005 Series cage guided control valve are effective solutions. However, given the high velocity, presence of erosive particles, and depending on the severity of the tank wall application, a more advanced and unique solution for the PTA tank mount level control application is the Masoneilan 75000 Series. The 75000 Series is used for severe service control valve applications where the conditions and environment are most harsh.
The Masoneilan 75000 Series valve includes many enhanced features, including a long-bending, sweep angle design to eliminate direct particle impingement against a “dead-angle” on the valve surface. Alternative globe or angle valve technologies with direct surface obstructions will quickly deteriorate from erosion from the PTA slurry’s rapid crystallization. Internal valve cavity structure is a robust, simple one-piece valve spool stem with heavy guidance, suitable for saturated slurry flow generated by a large range of gas chemical conditions and gasification induced vibration. The valve core trim has proven features for increased stability with wing-type plug guidance, flow-to-open design, large diameter stem, anti-erosion anodized materials, and heavier plug guiding against vibration. These features are core to the overall “hammer-type” operational design providing a strong anti-vibration hammer type plug to break through internal crystallization.
In many cases installation is required in tight spaces, such as under a tank or on a side wall. The 75000 Series’ flow-to-open design and side wall mount includes a horizontal stem. This compact design is essential to avoid deflection from side loading of large size trim and actuator components. Shortened yoke and actuators reduce the wear on the trim and make for easier installations. In many cases, tank mount level control valves also come with a second set of packing to act as a wiper to clear any contamination. Additionally, there is an optional design with a purge connection to inject fluid, such as steam, to clear crystallization or particles built up around the guiding surfaces.
Continuous Innovation
Baker Hughes research centers continue development of proprietary materials using the latest technologies in additive manufacturing. Dual laser printing methods allow for dual grade materials to be developed to create a durable base layer to avoid brittleness against high thrust sealing and a hardened outer layer that is fused to the base for ultimate erosion resistance. The latest methods for printing titanium are being utilized to minimize material waste from machining a 1-piece plug assembly, as well as optimizing the material structure for maximum material strength.
The latest in control valve positioner technology, the Masoneilan SVI™ 3, now includes advanced diagnostics that can detect early signs of erosive wear without opening the valve for manual inspection. With Valve Lifecycle Management (VLM) diagnostic software such as ValvAware can monitor the “as-shipped” factory condition over time to quantify material loss and detect leakage before it occurs. This allows process control engineers to avoid unexpected shutdowns or process losses and minimize maintenance crews exposed to unsafe areas.
Domestic China, Local Case Study
The Masoneilan 75000 Series severe service control valves have many installations in domestic PTA units within China. Zhejiang Dushan Energy Co., Ltd. PTA, located in Pinghu, Zhejiang, is one such example and a first unit to extend upstream as part of a complex to build a complete industrial chain of polyester filament yarn.
The first phase of the PTA project was design with an annual output of 2.2 million tons/year and was, at the time, the largest PTA unit in the world. A rapid construction cycle drove the unit to full production in only 2 years, a rare example of incredible execution within the industry. The project also introduced BP’s latest green and intelligent PTA production process technology, resulting in energy savings and consumption reduction through lower waste emissions, reduced production cost, device investment savings, and high degree of system automation.
For this unit, Masoneilan supplied the oxidation and refining unit angle control valves with large sizes for high capacity up to 16X18 inch, with an ANSI pressure rating of up to 1500 pounds. Valve materials include titanium, duplex stainless steel, and stainless steel.
In October 2019, Dushan Energy Co., Ltd. PTA plant successfully completed commissioning and start-up. In April 2020, after six months of operation, the unit was shut down for planned maintenance and inspection. An installed 75000 Series control valve was highlighted as having the most demanding operating conditions and the most critical position among the ten valves identified requiring disassembly, inspection, and repair evaluation. Upon inspection, the valve was in good condition and no identifiable wear of the valve internals was found.
Taking Energy Forward
The world of energy is constantly changing. Continuous push for safer, cleaner, and more efficient solutions drives our customers every day. These needs are the source of our motivation at Baker Hughes. These trends will all continue as the world pushes for still further advancements in lower cost solutions, energy conservation, and emission reductions.
These plant standards start with the equipment, especially the control valves used to operate the plant. As a major valve innovator and manufacturer in the PTA industry, Baker Hughes’ Masoneilan Control Valves product development team continues to enhance their offering, extending to new applications and technologies to exceed current limitations. We maintain close communication with users, and carefully listen to their feedback on our products. These comments and suggestions are invaluable to our pipeline of product upgrades.
About Baker Hughes
Baker Hughes (NASDAQ: BKR) is an energy technology company that provides solutions for energy and industrial customers worldwide. Built on a century of experience and with operations in over 120 countries, our innovative technologies and services are taking energy forward – making it safer, cleaner, and more efficient for people and the planet. Visit us at bakerhughes.com.