LitvĂnov, Czech Republic
LOWER COSTS, GREATER PERFORMANCE
[ Published in HOERBIGER@MOTIONâ€‚November 2014 ]
Czech Republic-based oil company Unipetrol for the first time installed the new eHydroCOM capacity control system from HOERBIGER in its Czech industrial gas plant. With great success: Unipetrol is benefitting from significant cost savings and increased performance in the operation of a nitrogen compressor.
The largest refinery, petrochemical and agrochemical complex in the Czech Republic is located on the outskirts of LitvĂnov, 50 miles northwest of Prague. The plant is owned by Unipetrol, the leading Czech oil and petrochemical company, which is part of the Polish PKN Orlen Group. The LitvĂnov site also encompasses a complex that produces polymers and other chemical products, such as ammonia. Nitrogen is required for the production of ammonia and is produced in a local plant operated by industrial gas specialist Air Products.
AMMONIA, STARTING MATERIAL FOR FERTILIZER
The Air Products plant in LitvĂnov liquefies and distills air, which is then separated into oxygen and nitrogen. The refinery uses oxygen to generate hydrogen from heavy petroleum residues. A portion of the hydrogen is used to create pure fuels. The remainder is enriched with nitrogen and converted into ammonia used to manufacture urea, which is an important fertilizer in farming.
The Air Products plant uses a Peter Brotherhood (Dresser-Rand) reciprocating compressor featuring an electric motor drive to compress the nitrogen - leaving the air separation station at 60 bar - to 324 bar. The nitrogen is conducted via pipelines to Unipetrol's ammonia plant, where hydrogen is added and the resulting mixture is conducted into an ammonia reactor.
IMPROVEMENTS THROUGH SOPHISTICATED CONTROL
At a rated power of 2,300 kilowatts, the nitrogen compressor costs Unipetrol almost 2 million euros a year in electricity alone. It goes without saying that savings potential had to be found, which resulted from the weaknesses of the original stepped compressor control unit.
At a capacity of exactly 75 percent or 50 percent, this process worked well. For any other delivery volume, however, nitrogen had to be throttled back, from the outlet side to the intake side of the compressor, via a bypass valve. The compression of excessive amounts of nitrogen unnecessarily wastes energy. In addition to the unnecessary power consumption, the stepped control moreover negatively impacted the downstream process.
ADVANTAGES OF STEPLESS CONTROL
Almost simultaneously with Air Products' and Unipetrol's quest for ways to lower operating costs in LitvĂnov, HOERBIGER was searching for pilot customers interested in a new capacity control system such as eHydroCOM.
Unipetrol was already using HydroCOM, the stepless capacity control system, made by HOERBIGER in other reciprocating compressors. They have been extremely satisfied with the resulting energy savings and reliability. The idea of an all-electric version of HydroCOM with comparable performance and even lower project costs was therefore highly attractive.
The eHydroCOM system was commissioned in May 2014. Estimates of the annual savings were approximately 3,000 megawatt hours, including a safety margin, which has meanwhile been confirmed. This corresponds to a reduction in energy consumption of 22 percent. In the overall assessment of all the savings, however, we will have to consider the installation costs for the project, and probably a minor increase in maintenance costs for the compressor.
The improved control performance also produced remarkable advantages because Unipetrol of late is varying throughput through the ammonia plant more strongly than in the past, which was more difficult to do with stepped control. Now, the final pressure of the compressor is more stable and the "surges" that they were experiencing with the stepped capacity control system are gone.
In the future, the downstream turbo compressor will be operated more closely to its pump limit, further increasing efficiency. Air Products also appreciates the faster control behavior with eHydroCOM: the process now is more flexible, and the operator is able to respond based on production demand.