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Booster compressor improves energy efficiency for Taiwanese chemical company

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Hydrocarbon Engineering,

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 in particular. 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 Corp. (the 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 GmbH 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 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 OUCC 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, who recommended the TVZ 900 manufactured by Mehrer Compression GmbH 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 the product range of Mehrer Compression GmbH – a specialist compressor manufacturer based in Baling, Germany.

Customer-specific modifications in accordance with the chemical industry's requirements

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 that 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. This is why 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,” said Jerry Wang, CEO of Taiwan Pneumtech Machine Corp., who 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 in order 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,” said Hartwig Alber, responsible for Marketing & Business Development at Mehrer Compression GmbH. “Another requirement that our 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, we use 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; 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 onsite 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.

In-house manufacturing guarantees reliable quality

All major components are manufactured in-house at Mehrer’s in order to ensure the quality of all the components. For this purpose, the high-pressure compressor experts work closely with German and Central European forges and foundries. This allows the company to ensure that all of the compressor’s components meet the highest requirements, such as, for example, the Mehrer crosshead pistons, which are specially designed for continuous operation in heavy-duty operating conditions and give the compressor a service life of over 20 years.

Moreover, all of the pressurised parts that are in contact with gas and are pressurised are subjected to a hydrostatic pressure test before being approved, and after which they are awarded a test certificate with their batch number. “We subject all of our components to a full-performance test”, said Alber. “Among other things, this also involves checking whether the device meets the customer’s requirements. For OUCC, we performed this particular test using moist air. However, depending on requirements and following an individual assessment, this test can also be conducted with other gases such as carbon dioxide, nitrogen or helium. We also only ever approve our systems for delivery once we know that the actual values match the required target values.”

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 he will be able to interpret the unit’s messages most effectively,” said 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 allows Mehrer to quickly and easily make changes to the software and update the control programme 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 Compression GmbH, 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.

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