The invention relates to a process for the steam cracking of a feedstock composed of at least 80% by weight, in particular of at least 90% by weight, of ethane, the process comprising a steam cracking of the feedstock in a furnace (2), then a quenching of the pyrolysis products, then a compression operation, then a series of successive operations on the products resulting from the quenching, the said series of operations comprising a washing operation, followed by a drying operation and at least one compression operation, and finally a fractionation by cryogenic distillation. A selective hydrogenation operation, followed by a catalytic conversion operation, will be inserted into the said process, after the drying operation and before the fractionation, in order to partially convert the ethylene predominantly into propylene.

A process for recovery of C.sub.2 and C.sub.3 components in an on-purpose propylene production system includes utilizing a packed rectifier with a countercurrent stream to strip C.sub.2 and C.sub.3 components from a combined de-ethanizer overhead lights vapor and cracked gas vapor stream.

A method of separating hydrocarbons containing three or more carbon atoms from an off-gas stream is provided. This method includes separating a light ends stream from a fractionator, thereby producing a stream rich in hydrocarbons containing three or more carbon atoms, and a stream lean in hydrocarbons containing three or more carbon atoms, separating the stream lean in hydrocarbons containing three or more carbon atoms in a membrane unit, thereby producing a permeate stream enriched in hydrocarbons containing three or more carbon atoms and a retentate stream, and separating the stream rich in hydrocarbons containing three or more carbon atoms in one or more separation columns, thereby producing one or more streams selected from the group consisting of a propylene stream, a propane stream, a butane stream, a light cat naptha stream, and a heavy cat naptha stream.

A process and an apparatus are disclosed for the recovery of components from a hydrocarbon gas stream which is divided into first and second streams. The first stream is cooled, expanded to lower pressure, and supplied to a fractionation tower. The second stream is cooled and separated into vapor and liquid streams. The vapor stream is divided into two portions. A first portion is cooled, expanded to tower pressure, and supplied to the tower at an upper mid-column feed position. The second portion and the liquid stream are expanded to tower pressure and supplied to the tower. After heating, compressing, and cooling, a portion of the tower overhead vapor is cooled, expanded, and supplied to the tower at the top feed position. The quantities and temperatures of the feeds to the tower maintain the overhead temperature of the tower whereby the major portion of the desired components is recovered.

A process and plant for natural gas liquids (NGL) recovery includes a main heat exchanger, a cold gas/liquid separator, a separation or distillation column, and an overhead gas heat exchanger. A pressurized residue gas generated from an overhead gas stream removed the top of the separation or distillation column is expanded and used as a cooling medium in the overhead gas heat exchanger and the main heat exchanger. The expanded residue gas, used as a cooling medium, is then compressed up to a pressure to be combined with the overhead stream from the separation or distillation column.

Systems and methods for separating one or more olefins are provided. In one or more embodiments, the method for separating one or more olefins can include separating at least a portion of one or more C.sub.3 and heavier hydrocarbons from a hydrocarbon containing C.sub.1 to C.sub.20 hydrocarbons to provide a first mixture that can include methane, ethane, ethylene, and/or acetylene. At least a portion of the first mixture can be hydrogenated to convert at least a portion of the acetylene to ethane and ethylene. At least a portion of the methane can be separated from the hydrogenated mixture to provide a second mixture that can include ethane and ethylene. At least a portion of the ethylene can be separated from the second mixture to provide a first product that can include at least 95 mol % ethylene and a second product that can include at least 95 mol % ethane.

Certain aspects of a natural gas liquid fractionation plant waste heat conversion to power using Organic Rankine Cycle can be implemented as a system. The system includes a heating fluid circuit thermally coupled to multiple heat sources of a natural gas liquid (NGL) fractionation plant. The system includes a power generation system that includes an organic Rankine cycle (ORC), which includes (i) a working fluid that is thermally coupled to the heating fluid circuit to heat the working fluid, and (ii) an expander configured to generate electrical power from the heated working fluid. The system includes a control system configured to actuate a set of control valves to selectively thermally couple the heating fluid circuit to at least a portion of the multiple heat sources of the NGL fractionation plant.

One or more specific embodiments disclosed herein includes a method for separating hydrogen from an olefin hydrocarbon rich compressed effluent vapor stream, employing a single heat exchanger, multiple gas-liquid separators, multiple expander/compressor sets, and a rectifier attached to a liquid product drum.

Certain aspects of natural gas liquid fractionation plant waste heat conversion to simultaneous power, cooling and potable water using integrated mono-refrigerant triple cycle and modified MED system can be implemented as a system that includes two heating fluid circuits thermally coupled to multiple heat sources of a NGL fractionation plant. An integrated triple cycle system, which includes an organic Rankine cycle (ORC), a refrigeration cycle and an ejector refrigeration cycle, is thermally coupled to the first heating fluid circuit. A MED system, configured to produce potable water, thermally coupled to the second heating fluid circuit. The system includes a control system configured to actuate control valves to selectively thermally couple the heating fluid circuits to portions of the heat sources of the NGL fractionation plant.

Embodiments of apparatuses and methods for reforming of hydrocarbons including recovery of products are provided. In one example, a method comprises separating a reforming-zone effluent into a net gas phase stream and a liquid phase hydrocarbon stream. The net gas phase stream is separated for forming an H.sub.2-rich stream and a first liquid phase hydrocarbon stream. The H.sub.2-rich stream may be contacted with an adsorbent to form an H.sub.2-ultra rich stream and a gas stream. C.sub.3/C.sub.4 hydrocarbons are absorbed from the gas stream with the liquid phase hydrocarbon stream. The gas stream may be contacted with an H.sub.2/hydrocarbon separation membrane to separate the PSA tail gas stream and form an H.sub.2-rich permeate stream and an H.sub.2 depleted non-permeate residue stream.