KR870001544B1 - Visbreaking process - Google Patents

Abstract

This invention relates to a process for heating residue hydrocarbon which is produced by distillation of crude petroleum. Hydrocarbon mixt. whose m.p. is more than 315 C is heated in primary low pathway and is transported through visbreaking region, and then ismixed with quenching stream to give primary step stream. This stream is separated into several kinds of hydrocarbons which have different m.p.s. These hydrocarbons are separated into quenching stream and secondary step stream. The secondary step stream is separated again to give the final product stream, and then the final stream is recovered. This process is economic and reduces heat-loss.

Description

Visbreaking Process

This figure is a simple process flow diagram to a preferred embodiment of the present invention.

The present invention relates to hydrocarbon conversion identification for use in reforming crude oil. In other words, the present invention is an improved visbreaking process, and generally relates to a heat treatment process of residual hydrocarbons produced by fractional distillation of crude oil. In particular, the present invention relates to heat exchange used in the process to minimize fuel consumption and maximize heat recovery in the process. The present invention also relates to a process for terminating a thermal cracking reaction by quenching a effluent from a non-breaking heater or a non-breaking reaction chamber with a low temperature hydrocarbon stream.

Visbreaking is a very well established industrial reforming process. Visbreaking and its associated pyrolysis processes are described on page 101 of Hydrocarbon Processing, published in May 1980. U.S. Patent Nos. 4, 169, 782 by H.L.Thompson provide a more complete process flow diagram for industrial bisbreaking processes. These documents are suitable as a technique for materials that can be used as quenching liquids mixed with the effluent of a bisbreaking heater.

The bisbreaking process is also described on page 109 of the Oil and Gas Journal (1981.4.13). This document describes, in particular, the use of a portion of the downstream of the fractionator receiving the bisbreaker effluent as a quenching stream mixed with the bisbreaker effluent. Phase 131 of the hydrocarbon treatment process, published in January 1979, describes bisbreaking. This document is suitable for the description of the technique starting from page 135 on the utility of quenching a bisbreaking heater effluent stream and other materials that can be used as a quenching stream. The process flow diagram of the bisbreaking residue shown in Figure 9 of Kirk-Othmer Encyclopedia of Chemical Technology, Vol. 15, Vol. 2, shows the various indirect heat exchangers used in the process. The flow chart is suitable for describing a technique for preferably heating the load stream by indirect heat exchange.

The present invention relates to a non-breaking process that reduces the cost and utility costs of the process. This improvement is achieved by heating the feed stream with a non-breaking heater by indirect heat exchange, which heats the stream to a higher temperature than the previous process. When the feed stream is injected into the non-breaking heater, it is at a higher temperature, so less fuel is consumed in the heater and the heater is smaller in size.

An important part of the process is the use of quenching streams with higher temperatures and higher flow rates than in conventional ratios. Even if the quenching material is at a higher temperature, using a larger amount of quenching stream can adequately reduce the temperature of the bisbreaker heater effluent.

The present invention is directed to heating a feedstream consisting of a hydrocarbon mixture having a boiling point of at least 600 ° F. (315 ° C.) by indirect heat exchange to a first substream, hereinafter referred to as a first substream; Moving the feed stream through the non-breaking band and mixing the resulting non-breaking band-out stream with a higher temperature quenching stream to obtain a first process stream; Separating a first process stream in a first separation zone into preferred hydrocarbon fractionates comprising the first downstream; Separating the first substream into the quenching stream and the second process stream after using the first substream in the indirect heat exchange; There is a feature of the method for thermally treating a hydrocarbon stream, comprising moving the second process stream to a second separation zone and recovering the product stream generated from the second separation zone.

The accompanying drawings are simple process flow diagrams for preferred embodiments of the present invention. This figure is simplified by eliminating several process equipment typically used in the present process, such as flow rate control systems, temperature and pressure control systems, pumps, and internal vessels. Preferred embodiments of the present process presented, together with the specified embodiments and embodiments thereof, do not depart from the scope of the invention.

A load stream consisting of reduced crude oil as a vacuum bottom fractionating liquid is introduced into the process via line 1 and heated by indirect heat exchange in exchanger 2. The load stream is heated again by the indirect heat exchange means 3 and moved into the visbreaking heater 4. This is accompanied by any addition reaction chamber (not shown) and the visbreaking conditions maintained in the heater, and then the non-breaking zone effluent conveyed by line 5 is mixed with the quenching stream conveyed by line 6. The temperature of the quenching stream is reduced to the temperature of the non-breaking band outlet stream below the non-breaking temperature. The mixture of these two streams is transferred via line 7 to the rectifying plate or fractionator 8.

The hydrocarbons injected into the rectification flash tower are separated into many hydrocarbon fractions with different boiling ranges. Thus, the upper vapor stream is removed via line 9. The steam stream is transferred to a suitable apparatus for separating and recovering the naphtha boiling range hydrocarbons contained in the steam stream. The lateral stream is generally removed through line 10 from the midpoint of the tower. This is a hydrocarbon mixture in the gas oil boiling range. This stream is generally cooled by indirect heat exchange, not shown, and split into fewer streams. Thus, the stream of cooled gas oil is transferred to the tower via lines 11 and 12 to facilitate separation, while the third stream is removed from the process through line 13 as a product stream. do.

The remainder of the hydrocarbon injected into the current flash tower is concentrated downstream and removed via line 14.

The undivided bottom stream is cooled by indirect heat exchange with the load stream. The flash top downstream is then divided into a quenching stream moving through line 6 and a second stream moving into a second flash band via line 15. The second flash zone 16 is operated at a lower pressure than the rectified flash tower 8. Hydrocarbons injected into the second flash zone are separated into one or more coking liquor, such as light gas oil and heavy gas oil. This is shown as the removal of the gas oil stream through line 17. The remaining partial liquid of hydrocarbon injected into the second flash zone is concentrated to the second downstream and removed via line 18. Heat is recovered from the stream by indirect heat exchange to the loadstream, and the second downstream is removed as fuel oil after mixing with an appropriate amount of cutter or cutback oil from a means not shown.

Bisbreaking refers to a hydrocarbon pyrolysis process in the form of mild pyrolysis used to reduce the viscosity and pour point of hydrocarbonaceous liquids derived from various heavy oils. Visbreaking operations are used to reduce the amount of low value residuals produced in petroleum reforming by improving a portion of the load stock with suitable fuel oil products. In addition, the bisbreaking operation is suitable for recovering low molecular weight hydrocarbons such as naphtha produced by the pyrolysis operation. The visbreaking process uses a single fractionation column as an initial separation zone or is combined with a vacuum fractionation column to recover an additional amount of off-gas or heavy gas oil.

The non-breaking operation consists of the basic steps of heating the load material to a relatively high temperature required for mild decomposition operation and maintaining the load stock at that temperature inversely proportional to the service temperature for a predetermined time. The material treated in this way is quenched to a sufficiently low temperature to terminate the pyrolysis reaction and serve as a separator.

In all these processes where the load stream has to be heated to elevated temperatures, a large amount of heat is consumed in the refractory loadstock heater. Thus, this consumption requires a significant amount of utility costs to operate the process. That is, it is an important object of the present invention to provide a non-breaking process with low utility ratio of operation by reducing fuel consumed in the non-breaking heater.

The raw material stream for the bisbreaking process is a high hydrocarbons stream, such as a top stream or vacuum reduced crude oil. Such materials are generally referred to as residual oils. Bisbreaking is also used for heavy crude oil and other hydrocarbonaceous materials. However, these various materials have a common feature that they contain heavy hydrocarbons having a boiling point of about 600 ° F. (315 ° C.) or more, as measured by suitable ASTM distillation methods. Preferably, the load torque of the non-breaking operation is when 10% has a boiling point of 500 ° F (260 ° C) or more.

The load stock for the non-breaking operation is first heated by indirect heat exchange in several heat recovery steps. This stoke is then moved to a non-breaking band, whereby a suction band or reaction chamber may be used for the process to increase the residence time of the load material heated at the desired temperature. Steam can be mixed with the feedstream to minimize coking in the heater tube of the visbreaking furnace. The nonbreaking heater and reaction chamber are maintained in a nonbreaking condition. In general, the non-breaking condition means a temperature condition of 800 ° -975 ° F (425-523 ° C.), and a temperature of 900 ° F (482 ° C.) or higher is preferable. In addition, a general bisbreaking pressure condition is 25-400 psig (172-278 kPag), and the literature describes a pressure of about 1000 psig (6895 kPag). The load stroke is preferably maintained in the non-breaking condition for about 20-65 seconds at a temperature of 900 ° F. (482 ° C.) or higher in the non-breaking band. The effluent of the bisbreaker heater is then preferably quenched with gas oil or the like to reduce the thickening by about 70-140 ° F. (39-78 ° C.). In visbreaking, it depends on the use of a soaker drum that holds for a predetermined time before quenching the hot effluent of the visbreaker heater. In this suction type bisbreaker, the heat conversion reaction is continued in the drum to reduce to the temperature required for the degree of conversion. Preferred temperature and pressure conditions vary by several factors such as the nature of the raw materials and the desired degree of pyrolysis. In addition, information on bisbreaking can be obtained from various documents such as the above-mentioned references.

In this process, the feed stream is heated to the desired bisbreaking temperature by a combination of indirect heat exchange with the hot process stream and a refractory heater. Initial heating includes the feed stream to the total substream of the first separation zone. Preferred initial heating also includes indirect heat exchange to the downstream of the second separation zone. However, the present invention heats the lower stream of the first separation zone, thereby reducing the amount of heat required in the refractory heater.

This heat exchange capability to yield higher feedstream preheat temperatures results from the use of the residual (bottom) material of the "comparative high temperature quenching" stream and the higher temperature non-flash downstream. As used herein, “relatively high temperature quenching” refers to a quenching stream having a temperature below about 300 ° F. (176 ° C.) lower than the bisbreaker effluent stream. The use of hot quenching streams requires the use of large amounts of quenching. It is preferred when the flow rate of the quenching stream exceeds the flow rate of the unquenched bisbreaker heater effluent. The hot quenching material is the bottom liquid from the separation zone so it concentrates back into the downstream when it returns to the separation zone. Thus, the flow rate of the downstream stream is increased. That is, more heat can be removed from the downstream and used to heat the feedstream without cooling more than desired. Thus, the feed stream is heated to a higher temperature, although the temperature of the downstream stream is the same as in the prior art before and after the exchange. This method of increasing the flow rate of the heat exchange medium will be the most preferred method since it limits the increase in pumping and piping costs.

Preferred embodiments of the present invention comprise heating the residual oil stock stream by indirect heat exchange to the first downstream, hereinafter referred to as the first downstream; Moving the feed stream through the visbreaking zone and then mixing the resulting bisbreaker zone effluent stream with a relatively high temperature quenching stream having a temperature of at least 600 ° F. (315 ° C.) to form a first process stream; Moving the first process stream to a first separation zone to separate the injected hydrocarbon into different boiling point milk powders comprising the first substream described above; After cooling the first rim substream by the heat exchange described above, dividing the first substream into the quenching stream and the second process stream; The second process stream can be described as a non-breaking process consisting of moving the lower pressure to a second separation zone and recovering the generated stream from the second separation zone.

In this process, the quenched effluent of the non-breaking zone is initially moved to two separate zones. These bands can be arranged in various configurations with the design of the separation band depending on the characteristics of the load stoke, the desired product and the process conditions. It is preferred when the first separation zone comprises a rectifying flash tower. The quenched effluent concentrates in the void space at the bottom of the rectification flash tower at a position slightly away from the bottom of the column. The column is operated at a bottom temperature of about 689 ° -860 ° F (365 ° -460 ° C.) and a pressure of 45-150 psig (310-1034 kpag). It is preferred when the pressure is above 650 psig (414 kpag). Here, the specific pressure is the pressure measured at the top of the separation vessel and the specific temperature is the bottom temperature of the vessel in question. The liquid phase is received below the column below the feed point and removed as a downstream. The rectification flash tower is equipped with means for adequately cooling the upper region of the column to condense an appropriate amount of liquid and result in countercurrent vapor-liquid flow. The upper rectifying region is preferably separated from the lower region by a trap-out tray. The preferred upper region contains five fractionation trays and reflux liquid is supplied from the uppermost tray. The liquid stream removed from the trap-out tray is cooled down and returned to the upper region of the higher point with two middle fractionation trays to facilitate the separation operation.

The downstream stream removed from the first separation zone is cooled with an indirect heat exchange step. This cooling is preferably accomplished by heat exchange only with the bisbreaker feedstream. It is also preferred that heat exchange be performed before the downstream stream is flashed to a lower pressure, such as the pressure of the second separation zone. After cooling, the downstream stream is moved to the second separation zone and partitioned into fractionation liquid used as quenching. The temperature of the downstream stream after heat exchange, ie the relatively high temperature of the quenching stream, should be at least about 600 ° F. (315 ° C.) and preferably at least 650 ° F. (343 ° C.). More preferably, the quenching stream is at least about 680 ° F. (360 ° C.). The flow rate of the quenching stream is set and measured by the flow rate and temperature of the bisbreaker effluent stream, the temperature of the quenching stream and the desired temperature reduction provided by the quenching.

The remaining downstream in the first split band is moved to a second split band called the second flash band. It is an empty container with an upper steam outlet, which is stored to maintain the liquid level below the supply point. The liquid is sprayed into the vessel at a central position above the feed point. The second flash band is operated at a pressure lower than the first separation band. The temperature range used in the band is about 644-752 ° F (340-400 ° C.). The pressure used in the zone is also at least 30 psig (207kpag) lower than the operating pressure in the lower region of the rectifying flash zone. The pressure range in this zone is about 0-100 psig (0-689 kpag). The design and operation of the first and second separation bands and other devices used in the present invention are not unique.

Those skilled in the art of reforming will appreciate that the apparatus and equipment of the present invention are designed with suitable process equipment. Nevertheless, examples of the technical design (calculated) operation of industrial scale units are described below for an accurate understanding of the present invention. The feedstream is 20,000 barrels (3180 m ³ ) per day downstream of the reduced crude oil.

In this embodiment, the temperature in square brackets is the temperature estimated in the prior art (low temperature) quenching system. The feedstream is introduced into the process at about 480 ° F (249 ° C) and heated to about 4550 ° F (288 ° C) by indirect heat exchange to the downstream of the second separation zone, where the downstream of the second separation zone is 650. It cools from ° F (343 ° C) to 550 ° F (288 ° C). The heated raw material is then heated again to 710 ° F. (377 ° C.) [670 ° F. (343 ° C.)] by indirect heat exchange to the downstream of the first bunker zone. The raw material is then transferred to a bisbreaker heater and heated to 925 ° F. (496 ° C.). The effluent of the bisbreaker heater is quenched to about 820 ° F. (438 ° C.) by air temperature quenching of the present invention. The quenching temperature is about 700 ° F. (371 ° C.) [550 ° F. (288 ° C.)]. In order to condense the higher temperature quenching liquid, the amount of quenching is increased to 1.45: 1 from the weight ratio of quenching to effluent of 0.65: 1 in conventional identification. Thus, the flow rate of the downstream stream increases greatly. In this embodiment, the increased temperature of the feedstock (40 ° F. or 22 ° C.) to the bisbreaker heater causes the bisbreaker to reduce the temperature of the heater and result in fuel savings of at least 10%. Although, in this embodiment, slightly increased heating of the feed stream occurred due to the use of the non-flashed hotter lower liquid from the first separation zone, the more of the total substream corresponds to the increased temperature of the quenching stream. Improved heating due to large material flow rates is important.

Claims (2)

Heating the raw material stream consisting of a hydrocarbon mixture having a boiling point of at least 600 ° F. (315 ° C.) by means of heat exchange between the streams referred to as the first downstream stream; The feed stream is moved through the non-breaking zone, and the resulting non-breaking zone effluent is mixed with a quenching stream having a relatively high temperature of 600 ° F (315 ° C.) and a flow rate greater than the flow rate of the non-breaking out stream. Forming a first process stream; Separating the first process stream of the first separation zone into a desired hydrocarbon fraction comprising the first substream above; Dividing a first substream into the quenching stream and a second process stream using a first substream phase for the indirect back exchange; Moving the second process stream to a second separation zone to recover the product stream generated from the second separation zone. The process of claim 1 wherein the feed stream is heated by indirect heat exchange with respect to the second downstream stream removed from the second separation zone prior to being heated by heat exchange with the first downstream stream.

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