Cracked Gas Compressor(CGC) fouling, Anti-fouling technologies and treating process to prevent fouling

Olefins are produced by thermal or catalytic cracking of hydrocarbons from gaseous such as ethane, propane and butane, liquefied petroleum gas, to the liquid feedstock such as light and heavy naphtha, gasoil and vacuum gas oils. The type of feedstock depends on the availability. The production process can be divided into four main sections; cracking furnaces quench sections (direct and indirect), compression units, and separation columns. The pyrolysis takes place in the tubular reactors, inside the firebox of the furnace, at high temperature, low pressure and a very short residence time. The cracked gas compressor (CGC) is the critical system in modern ethylene plants. This compressor drives gases from the crackers for downstream separation. Unsaturated hydrocarbons which formed during the cracking process are reactive species. Cracked gas contains appreciable amounts of highly reactive di-olefins and acidic compounds that are subject to oxidation and/or polymerization. Unsaturated contribute to free radical generation via thermal reaction or Dies-Alder mechanism or oxidation at the high temperatures found in the compressors, forming polymers. These polymers tend to accumulate in the compressor discharge lines, casing and after-coolers. Costs associated with CGC fouling are high, and they can increase exponentially as conditions deteriorate. Result: The reliability of CGCs remains a serious issue in spite of improvements in design and system metallurgy. Therefore, olefins plants are exploring new techniques to optimize compressor performance and run length. Many operators are discovering that chemical additives can offer attractive advantages for fouling control. Fouling in a cracked gas compressor can negatively affect plant economics. Initial efficiency loss does not increase costs signif icantly if there is adequate turbine capacity; increasing the turbine speed prevents lost production. However, once the turbine is limited, any additional loss in efficiency results in reduced throughput and a dramatic increase in the total cost of operation (TCO). In addition to energy cost and production loss, a fouled compressor may require an unscheduled shut down. Even before shutting down, a fouled machine is usually operated at higher-than-desired suction pressure, in order to maintain the desired discharge pressure. This affects unit economics; increasing the first-stage suction pressure increases the furnace pressure and lowers selectivity towards ethylene. Organic fouling in process gas compressors (PGC) is an important issue that many olefin plants must manage. When fouling occurs, PGC efficiency drops and compressor vibration increases. Minimizing fouling is critical to limiting production losses and high maintenance costs in existing or new steam crackers. The introduction of lighter feed stocks from shale gas is expected to increase the probability of fouling in PGCs. There are numerous factors to consider when managing PGC organic fouling and resulting reliability issues. Compressor wash oil (CWO) plays a vital role in assuring and improving compressor reliability. This paper provides an overview of cracked gas compressor fouling, antifouling technologies, treating process to prevent fouling and the key operating parameters. Fundamentals of cracked gas compressor fouling controls and monitoring are provided to aid in the improvement of performance. In this study, however, we discussed the problems related to the CGC fouling from the beginning to elimination in an olefin plant. With an increased understanding of the factors affecting the formation and increasing this material, we tried to eliminate or control it.

کلیدواژه ها:

Cracked Gas Compressor ، Fouling ، wash oil ، PTFE coatings