In recent years, the Asian market has seen a rapid increase in polyester production, the manufacture of which depends on the use of ethylene oxide and ethylene glycol. However, the production of these two substances is a very energy-intensive process, which is why the chemical industry is increasingly relying on sustainable techniques.
Until 2016, the Taiwanese Oriental Union Chemical Corporation (OUCC) from Taipei used two dated compressors, which required a lot of maintenance and therefore no longer met the increased requirements of the chemical industry. The OUCC consequently commissioned Mehrer Compression from Germany with the production of a modern two-stage dry-running compressor for volatile organic compounds. The resulting TVZ 900 is oil-free and water-cooled, has been specially designed to meet the requirements of OUCC and is capable of properly recycling waste gases for use in other production processes. Thanks to its direct-coupled motor, the TVZ 900 is extremely energy efficient, low maintenance and guarantees a system availability of 97%.
Before the acquisition of the TVZ 900, the compressor that OUCC was using needed increasingly more maintenance to the point that OUCC finally decided that it had to be replaced as quickly as possible, which was why it was important to find a company that would be able to supply both a highly energy efficient compressor and to do so quickly. OUCC had been in contact with the compressor supplier Taiwan Pneumtech, which recommended the TVZ 900 manufactured by Mehrer Compression as highly suitable for its needs. The TVx series, which this model is part of, has been specifically designed for use with process gases such as hydrogen (H2), carbon dioxide (CO2) and ethylene (C2H4), which are common in the chemical and petrochemical industry and in R&D systems. The 900 series is one of the largest systems in Mehrer Compression’s product range.
The TVZ 900 is a two-stage dry-running compressor with a V-block and is designed for compressing flammable gases. Due to the fact the chemical and petrochemical industries often work with flammable substances coupled with the fact that the associated machines are often simultaneously exposed to extreme temperature fluctuations, their safety is a top priority. Hence the compressor systems used in these settings also have to be specifically adapted for use in explosive environments. Thanks to its pressurised enclosure, the TVZ 900 also guarantees the safety of OUCC’s employees in these environments, as all of its components meet the company’s minimum requirements for Ex-zone 2, II 3G, T3.
“What we also consider to be of particular note regarding the TVZ 900 is the fact that it is extremely easy to maintain,” says Jerry Wang, CEO of Taiwan Pneumtech, which had recommended the system to OUCC. “Thanks to the direct-coupled motor, its energy efficiency is 2-4% higher than that of a belt-driven compressor.” In addition, it has a smaller size thanks to its optimised design and space-saving arrangement of all its components, and only takes up around 40% of the floor space required by similar compressors. This means that the system can be easily integrated into any machinery park. Being extremely flexible, the compressor also automatically responds to the different process-related volume flow requirements through the aid of a frequency inverter.
Closed secondary cooling circuit prevents damage
Since OUCC works with a wet gas mixture that contains carbon dioxide, all of the compressor’s components had to be made from stainless steel to prevent corrosion. The compressor also had to be fitted with automatic condensate discharge valves because gas saturated with water vapour increases the risk of a water hammer, which can cause serious economic damage by bringing the entire production system to a standstill. Another requirement that the compressor had to meet was that it had to have an efficient cooling concept that would be optimally matched to the production process. To ensure this, the company used a closed secondary cooling circuit.
If the cooling system isn’t perfectly matched to the production process, there is a risk that cooling water that is too cold might cause water condensate to be discharged through the suction valves, which can damage the system. The cooling system of the TVZ 900 has been specially designed to avoid this risk. That is, the high-volume flow on the one hand and the low temperature difference on the other ensure that the entire compressor’s temperature is always kept within the required range. The compressor’s excess heat is transferred to the cooling system on site by a heat exchanger and the entire system is controlled through the automated volume flow control, which regulates the cooling water’s flow to the heat exchanger.
Fast commissioning and efficient support
Due to the high level of connectivity of today’s chemical plants achieved thanks to the standards of Industry 4.0, it is really important for any new equipment to perfectly fit into the system’s periphery. “In such projects, it is therefore always advisable for a new compressor to be commissioned by its manufacturer, because they will be able to interpret the unit’s messages most effectively,” says Wang. “That is, it is often also possible to solve system-related issues using remote maintenance technologies.” Mehrer does so by using data interfaces such as Modbus RTU (RS 485), Profibus and Profinet/Ethernet – and preferably Profinet PN/PN coupler. This allows the compressor specialists to access the supplied control unit on site as soon as a user has established a physical connection and approved remote access. This enables Mehrer to quickly and easily make changes to the software and update the control program when needed.
When, for example, the TVZ 900 was installed in the south of Taiwan in Kaohsiung in January 2016, Mehrer was able to assist with the unit’s commissioning, as changes in OUCC’s process parameters made it necessary to adjust control-related settings. The smooth interaction between Mehrer, its Taiwanese distribution partner and OUCC employees subsequently made it possible to efficiently work on the system remotely and to commission the high-pressure compressor in March 2016 as planned.