RU2200182C2 - Hydrocarbon feedstock preliminary distillation process - Google Patents

Abstract

FIELD: petroleum processing. SUBSTANCE: invention relates to processing of petroleum on lowcapacity modular installations to yield motor fuels from limited local feedstock sources. Fractionation of petroleum is performed using cyclonic phase separator and contact evaporator either to produce, in continuous mode, gasoline fraction and stripped heavy residue or to produce periodically gasoline fraction, diesel fuel, and fuel oil. Feedstock is heated in recuperative heat-exchangers and separated in phase separator into liquid and gas phases. Liquid phase in dispersed state enters, in countercurrent mode, vapor space of contact evaporator. Vapor phase is further heated to a temperature by 30-50 C superior to that of liquid phase and fed, as stripping agent, through bubble distributor into liquid phase bulk located in bottom zone of contact evaporator. Gasoline fraction is obtained by condensation of vapor phase from evaporator. To obtain diesel fuel, stripped residue is circulated through steam preheater and phase separator, which results in that diesel fuel vapors overheated in contact evaporator to 250-300 C are used to strip fuel oil (residual fraction). EFFECT: simplified hardware implementation and improved economical and environmental characteristics. 3 cl, 1 dwg

Description

 The proposed method for the primary distillation of hydrocarbon raw materials is designed to meet local needs for motor and boiler fuel in the regions of oil and gas condensate production and at pumping stations of oil pipelines in order to obtain fuel for a gas turbine pump drive.

 Modern large-tonnage distillation methods for hydrocarbons, in addition to pumps and heat exchange equipment, include tube furnaces and distillation columns. Small-tonnage primary distillation units repeat the fundamental technological solutions of similar installations of modern oil refineries. The hardware design of the distillation process is characterized by high metal consumption, requires significant capital investment [1; 2; 3].

 Given the high cost and complexity of operation of small-tonnage installations for the production of motor fuel, performed according to the technological scheme of large-capacity refineries using distillation columns and tube fired furnaces, non-traditional technological solutions for the primary distillation of hydrocarbon raw materials are developed.

 So, for example, in the USA, such plants are used for the production of diesel and gas turbine fuels from pumped oil to cover the fuel demand for the drive of pumps for main oil pipelines.

 “Typically, low-capacity refineries have a high capital cost and their operation is expensive. Such refineries are used to produce diesel and gas turbine fuels from oil pumped through the pipeline. Typically, such refineries use the same oil distillation scheme as large-capacity ones, and already the use of a distillation column alone makes such a plant uneconomical.

 Two units in Louisiana successfully tested multi-stage oil evaporators with heat supply from a circulating liquid coolant; a third such facility will be built in Texas. The capacity of each installation is 100,000 tons per year, but can be brought up to 500,000 tons per year "[4].

 New in the proposed method is the intensification of the phase separation processes of the equilibrium multicomponent hydrocarbon vapor-liquid stream. The main limitation of the intensity and depth of separation is associated with a low diffusion rate, overcome in practice by increasing the interface: decreasing the particle size of the liquid being treated, organizing a drip-jet or film flow, using sprayers, nozzles, etc.

 To intensify the separation of the vapor-liquid emulsion of the heated hydrocarbon liquid, the use of centrifugal force is proposed. So, for example, when a steam-liquid mixture stream preliminarily dispersed by heating is supplied to a curved surface at a speed of 10 m / s and a radius of curvature of 5 cm, an artificial gravity field is created that is approximately 200 times greater than Earth's gravity. In this case, rapid coagulation of the liquid with a sharp decrease in the phase separation surface prevents the reverse absorption of hydrocarbon components from the vapor phase. The rate of release of low-boiling hydrocarbons from the liquid phase is increased by heat and mass transfer of superheated vapors in a contact evaporator with a liquid.

 The closest in purpose and technical essence to the proposed method are technological schemes of small-tonnage installations for producing motor fuels from hydrocarbon raw materials in the places of its production. The disadvantage of this technology is the large range of equipment, similar to large-capacity oil refineries (refineries); equipping the installation with distillation columns and tubular fire furnaces greatly complicates operation and safety, which is compounded by the low technological availability of small-tonnage installations installed in remote raw material deposits, compared to refineries [2].

 Schematic diagram of the proposed method is presented in the attached figure and includes the following devices: collection capacity of straight-run gasoline (1); diesel (2) and boiler and furnace fuels (3); circulation pumps of the working fluid of the vacuum unit (4) and the topped residue (5); contact evaporator (6); bubbler distributor of superheated stripping vapors (7); liquid phase atomizer (8); steam heaters of liquid (9) and steam (10) phases; recuperative raw material heater (11); cyclone phase separator (12); ejector of a vacuum installation (13); regulators of level (14; 15) and temperature (16; 17); check valve (18); air condenser (19); drop eliminator (20); steam jet mixer (21); raw material heater coil (22); hot compartment (23) of the heavy residue tank (3) (boiler oil).

The diagram shows the flows:
raw material I; straight run gasoline II; diesel fuel III; boiler oil IV.

Raw material I passes through a recuperative condenser (1), gasoline fraction II vapor, then it is heated in the coil (22) of the hot compartment of the boiler-furnace fuel collection tank (3) and the steam heater (9) and enters the cyclone phase separator (12), with a regulator (15) in the contact evaporator the boiling point of the selected gasoline fraction is maintained, enters the cyclone phase separator (12). The liquid phase under pressure of single vapor through the distributor (8) is fed into the vapor space of the contact evaporator (6) in the form of small drops and jets, where due to heat and mass transfer with superheated vapors of the selected fraction, the liquid is depleted in low boiling hydrocarbons and enriched in high boiling components. In order to maintain overpressure, to eliminate the slip of the vapor phase with the liquid in the phase separator, the regulator (14) maintains a constant level. The vapor phase V from the separator (12) overheats in the steam heat exchanger 10 30-50 ^° C higher than the temperature of the liquid phase in the contact evaporator, enters the volume of the liquid phase through the bubbler distributor of stripping vapors (7) for stripping low-boiling components from the liquid, selected as target product, and condensation in the liquid phase of high-boiling components from superheated vapors in contact with it.

 According to the Institute of Hydrocarbon Raw Materials (VNIIUS, A.S. 1074891), the supply at the stage of oil separation of an uncondensed phase in an amount of 2% by weight for oil allowed to increase the yield of gasoline by 25-30%.

The vapor of the gasoline fraction is removed from the contact evaporator through a shell-and-tube condenser (11), in which it is cooled by the feedstock, and enters the collection tank of the gasoline fraction (1). The gasoline fraction is distilled off during the period of filling the evaporator with raw materials (6). When two products are obtained during the distillation process, the vapor phase and the residue are selected, for example, gas condensate distillation or the production of a gasoline fraction and topped heavy residual motor fuels from oil, the process is carried out continuously. When distilling oil with the selection of the gasoline fraction, diesel and boiler fuel, the selection of the diesel fraction is carried out by stopping the pumping of raw materials, after filling the evaporator. The topped residue is circulated by a pump (5) through a steam heater (9), a phase separator (12) with a separate supply of steam and liquid phases to the contact evaporator. Superheated vapors from the steam heater (10) (diesel fuel) are sent to stripping the residue (boiler oil). When the temperature of the residue reaches 250-300 ^o With turn on the circulation pump (4) of the vacuum-containing installation and continue stripping the residue at a residual pressure in the evaporator of 0.1-0.2 kg / cm ² . The vapors of the diesel fraction are condensed in an air condenser (19) and merged into the container (2) through the piping of the ejector (13).

 Upon reaching the normalized flash point of the residue, turn off the pump (5), stop circulating the residue through the separation compartment from the contact compartment of the evaporator (6) supplied by the jet pump (21), the active stream of which is the superheated vapor phase from the heat exchanger (10), which is also a stripping agent providing deep selection of the diesel fraction from the residue, the boiler-furnace fuel is drained into the hot compartment (23) of the tank (3), in which the coil-heat exchanger (22) is placed to heat the raw material during pitching to the evaporator (6). In order to reduce hydrocarbon emissions into the environment, the selected fuel fraction is used as the working fluid in the ejector vacuum-creating unit.

 It is known that the accuracy of separation of hydrocarbon feedstocks into fuel fractions by single evaporation is significantly lower than the separation in distillation columns. In order to increase the clarity of separation into fuel fractions, the intensive separation of the vapor-phase stream is carried out in a centrifugal field with an additional three-fold evaporation of the liquid phase by superheated vapors of the selected light fraction: upon contact of the liquid phase in the form of small droplets and jets with superheated vapors in the vapor volume of a contact evaporator, and blowing of the liquid phase By sparging small jets of superheated vapors through its volume and during stripping of the liquid in the jet mixer (21), a sufficient margin of quality is ensured for the fraction th composition derived motor fuels.

 The effectiveness of these technological methods is confirmed by the results obtained by the institutes of VNIIUS and VNIIGAZ, as well as gradual evaporation plants operating in the USA, which ensure the production of diesel and gas turbine fuel for pumping pumping stations of main gas pipelines.

The main differences of the installation:
- in the technological scheme there is no distillation column and fired tube furnace. The indicated feature of the hardware design of the process of processing hydrocarbon raw materials into motor fuel greatly simplifies the operation of the installation. The maximum effect is achieved when using this installation at remote fields and pumping stations, oil trunk pipelines, remote from the refinery;
- the absence of direct fire heating of raw materials and low working overpressure in the apparatus virtually eliminates emergency situations with the ignition of raw materials, destruction of equipment and reduces the environmental risk of release into the environment;
- low cost of processing.

 To obtain fuel fractions, a unified module with a nominal raw material productivity of 100,000 tons per year is used. The minimum and maximum productivity, respectively, are 30,000 and 120,000 tons per year.

Sources of information
1. G.A. Lastovkin et al. Refinery Handbook. 1986 year

 2. S.P. Pavlova et al. “Field processing of gas condensates and production of motor fuels. A review series. Preparation and processing of gas condensate”. Issue 3. VNIIEGAZprom. 1982 g.

 3. A. V. Frolov and others. The scheme for producing diesel fuel at the Surgut ZSK. Gas industry, 1. 1987

 4. Express information "Distillation of oil and petrochemistry", 1980. 14. VNII-ENEFTEKHIM.

Claims (3)

1. The method of distillation of hydrocarbon feedstock, including its heating, evaporation and separation into vapor and liquid phases, characterized in that the vapor phase is superheated 30-50 ^o C above the temperature of the liquid phase and fed into the lower zone of the contact evaporator in the volume of the liquid phase, as a stripping agent, the vapor phase from the contact evaporator is condensed and removed as the target product, the liquid phase is introduced into the vapor volume of the contact evaporator in the form of small drops and jets in countercurrent to the vapor phase, the gasoline fraction is distilled from the feedstock during replenishment of the contact evaporator, stopping the supply of raw materials, upon receipt of diesel fuel, the topped residue is circulated through a steam heater, a phase separator, superheated vapors of the target product (diesel fuel) are sent to evaporate the residue (boiler-furnace fuel) to the contact evaporator, when the temperature of the residue 250 is reached -300 ^o C, include a vacuum-generating unit, the remainder (boiler oil) is drained from the separation compartment of the evaporator, into which the remainder from the contact compartment of the evaporator is supplied They are driven by a jet pump with simultaneous additional stripping of the residue from the diesel fraction.  2. The method according to p. 1, characterized in that the working fluid in the ejector vacuum-generating installation is a selected fraction.  3. The method according to p. 1, characterized in that during the distillation of hydrocarbons into two target products, the technological process is carried out continuously.