The compressor location is generally at the mezzanine and driven by a steam turbine. Due to this, the H 2 recycle compressors normally have 6–12 stages, run at high speeds like a steam turbine, or both. Low molecular weights are difficult to compress and have little pressure rise or volume reduction per stage. The compressor gas is mainly H 2 with a low molecular weight. By pulling the barrel out of the compressor casing and lifting off the top half of the inner barrel, all compressor internals are accessible for inspection. The balancing piston seal, shaft end and inter-stage seals are also contained in the main casing. The compressor is typically a centrifugal type based on the API 617 design and consists of a vertically split main casing, which houses the rotor, inlet guide vanes, diaphragms and intake/discharge walls. Working around H 2 compressors, especially reciprocating gas compressors, requires knowledge, understanding and experience. Detecting a burning H 2 leak may require a flame detector, and a leak can be hazardous. Pure H 2-oxygen flames emit ultraviolet light, and high-oxygen mixes are nearly invisible to the naked eye. The H 2 auto-ignition temperature-the temperature of spontaneous ignition in the air-is 500☌ (932☏). A spark, heat or sunlight can trigger explosive reactions. H 2 gas forms explosive mixtures with air at concentrations from 4%–74% and with chlorine at 5%–95%.

H 2 gas is colorless, odorless and highly flammable.

Another check valve is required downstream of the anti-surge valve. Typically, two check valves are placed close to the injection point to prevent reverse liquid flow towards the pump. Consider the pump shutoff pressure when designing the compressor to prevent surging. 1 shows a liquid feedstock sent to the heater by a charge pump, normally a centrifugal pump. Ensuring the reactions are carried out completely.įIG.Preventing coke formation as the feedstock is heated to the reaction temperature.Lowering the heater and feed effluent exchanger tube wall temperatures by increasing the flow through the equipment.Absorbing some of the heat of reaction, minimizing the catalyst bed temperatures.The large quantity of H 2 gas recycled from the separator to the reactor has the following purposes: Make-up gas (Point C) supplied by a separate reciprocating gas compressor replaces the H 2 consumed. The primary duty of the recycle gas compressor is to move the feedstock (Point A) through a fired heater, reactor, reactor feed effluent exchanger, air and trim cooler, separator and finally, the compressor’s suction. 1 shows a typical sketch of the hydrotreating process in oil refineries, upgraders and petrochemical plants. Some hydrocracking and thermal cracking reactions may take place in the hydrotreating process.

The hydrotreating process reduces mercaptan, sulfur, metal content, nitrogen, oxygen, organic halides (chlorides and bromides), olefins and aromatic components of the feedstock while enhancing the cetane/octane number in oil refining and the density and smoke point of the product. This article will explain the hydrotreating process and address compressor fouling, which impacts the recycle gas compressor’s performance and reliability, based on the author’s experience working in large oil refineries, petrochemical plants and upgrader plants. Stress corrosion cracking, possibly combined with high cycle fatigue, causes impeller and rotor failures. The risk of fouling is high in recycle gas compressors due to chemical injection and reactions in the reactor. Depending on the licensor, the number and configuration of the equipment may be different however, the process is very similar. The hydrotreating process is similar in oil refineries and petrochemical plants like aromatic plants and upgraders. H 2 recycle compressors are used with oil refinery processing equipment, including hydrocrackers, hydrotreaters, platformers and isomerization units.

Gas compressor