Certain aspects of natural gas liquid fractionation plant waste heat conversion to power using Kalina Cycle can be implemented as a system. The system includes a waste heat recovery heat exchanger configured to heat a buffer fluid stream by exchange with a heat source in a natural gas liquid fractionation plant. The system includes a Kalina cycle energy conversion system, which includes one or more first energy conversion heat exchangers configured to heat a working fluid by exchange with the heated buffer fluid stream, a separator configured to receive the heated working fluid and to output a vapor stream of the working fluid and the liquid stream of the working fluid, and a turbine and a generator, wherein the turbine and generator are configured to generate power by expansion of the vapor stream of the working fluid.

Certain aspects of natural gas liquid fractionation plant cooling capacity and potable water generation using integrated vapor compression-ejector cycle and modified multi-effect distillation system can be implemented as a system. The system includes a waste heat recovery heat exchanger network thermally coupled to multiple heat sources of a Natural Gas Liquid (NGL) fractionation plant. The heat exchanger network is configured to recover at least a portion of heat generated at the multiple heat sources. The system includes a first sub-system thermally coupled to the waste heat recovery heat exchanger to receive at least a first portion of heat recovered by the heat exchanger network. The first sub-system is configured to perform one or more operations using at least the first portion of heat recovered by the heat exchanger network.

A gaseous fraction leaving overhead from a fractionation column of a catalytic cracking unit (FCC) is fractionated using a unit for the conversion of ethylene into propylene, in order to upgrade the ethylene contained in the fuel gas.

Certain aspects of a natural gas liquid fractionation plant waste heat conversion to potable water using modified multi-effect distillation system can be implemented as a system that includes a waste heat recovery heat exchanger network thermally coupled to multiple heat sources of a Natural Gas Liquid (NGL) fractionation plant. The heat exchanger network is configured to recover at least a portion of heat generated at the multiple heat sources. The system includes a sub-system thermally coupled to the waste heat recovery heat exchanger network to receive at least a portion of heat recovered by the heat exchanger network. The sub-system is configured to perform one or more operations using at least the portion of heat recovered by the heat exchanger network.

Selective recovery of C2 to C4 hydrocarbons is achieved through the use of a converging-diverging nozzle, or de Laval nozzle. The vapor stream comprising C2 to C4 hydrocarbons is fed into an inlet of a de Laval nozzle having a throat. The vapor stream may have an initial temperature of between 0 C. and 100 C., and an initial pressure of between 200 psig and 500 psig. In the de Laval nozzle, the vapor stream expands after passing through the throat of the de Laval nozzle, producing a vapor stream having reduced temperature and pressure. Then, C2 to C4 hydrocarbons condense from the reduced-temperature vapor stream as liquid droplets, which may be recovered. Fractionation of C2 to C4 hydrocarbons by means of a de Laval nozzle is possible; the technique allows selective recovery of a stream enriched in propene from a mixture of propane and propene.

A process for producing liquefied natural gas and liquid carbon dioxide from a natural gas feed gas comprising at least the following steps: Separation of a natural gas feed gas into a CO.sub.2-enriched gas stream and a natural gas stream; Cooling of said natural gas in a heat exchanger; Purification of the in step 1 from compounds containing at least six carbon atoms; At least partial condensation of said gas stream resulting from step 3 to form a two-phase stream; Separation of said two-phase stream resulting from step 4 to form a gas stream and a liquid stream; Condensation of the gas stream resulting from step 5 to form a liquefied gas containing less than 5 ppm by volume of compounds containing at least six carbon atoms; Liquefaction of the CO.sub.2-enriched gas stream resulting from step 1 with a portion of the liquid stream resulting from step 5.

A method for cryogenically separating a natural gas supply stream into a gas containing the most volatile compounds of the supply stream, and a liquid product containing the heaviest compounds at least including the following. Introducing an at least partially condensed stream into an absorption column at an introduction stage in the lower part of said absorption column, thus producing, at the top, a gaseous stream that contains the most volatile compounds and, the bottom, a liquid product. Introducing the liquid product into a fractionation column in order to obtain, in the bottom of the fractionation column, a liquid product that contains the heaviest compounds of the supply stream and, at the top of the fractionation column, a distillate that is at least partially condensed in a second heat exchanger system

A method of cryogenically separating a natural gas supply stream into a gas which contains the most volatile compounds of the supply stream, and a liquid product which contains the heaviest compounds of the supply stream, including the following steps: at least partially condensing a natural gas supply stream in a first heat exchanger system; introducing the liquid product into a fractionation column in order to obtain, in the bottom of the fractionation column, a liquid produce that contains the heaviest compounds of the supply stream and, at the top of the fractionation column, a distillate that is at least partially condensed; introducing, at a stage in the upper part of the absorption column, the gaseous phase of the condensed distillate as a supply stream for the absorption column; where the distillate is condensed in a bath-type vaporizer-condenser installed in a casing mounted on the fractionation column.

A process for simultaneously producing treated natural gas and a propane-rich stream from a feed gas comprising methane, ethane and hydrocarbons having more than three carbon atoms.

Methods and systems for treating a compressed gas stream. The compressed gas stream is cooled and liquids are removed therefrom to form a dry gas stream, which is chilled in a first heat exchanger. Liquids are separated therefrom, thereby producing a cold vapor stream and a liquids stream. A first part of the cold vapor stream is expanded to produce a cold two-phase fluid stream, and a second part of the cold vapor stream is cooled to form a cooled reflux stream. Various streams are fed into a separation column to produce a cold fuel gas stream and a low temperature liquids stream. The second part of the cold vapor stream is cooled by the cold fuel gas stream, which becomes a warmed fuel gas stream that is compressed and used with the low-temperature liquids stream to chill the dry gas stream and to cool the compressed gas stream.