SI9400032A - Device for thermal cracking mixture of liquid and gaseus hydrocarbons - Google Patents

Abstract

In an apparatus for the thermal cracking of a mixture of liquid and gaseous hydrocarbons, at least one pipe (R3) for the mixture leads into a heat exchanger (W1) which is connected, if appropriate, for fluid conduction to a pipe (R4) leading out of the heat exchanger via a by-pass line with a controllable isolation valve (V1) in the through-flow, the pipe (R4), which leads out of the heat exchanger (W1) and into which at least one further pipe (D1) for superheated steam leads, leads in turn into a further heat exchanger (W2) whose outlet line (R5) leads into a downstream heat exchanger (S), if appropriate with a catalyst, whose outlet line (R6) leads into a cooling and separation device (K+A), at least one gas separator for separating off a gaseous fraction from the mixture being provided upstream of the heat exchanger (W1), as viewed in the direction of flow, and the by-pass line, being a gas line (G1) which has a controllable isolation valve (V1) in the through-flow and leads out of the gas separator (G) into a further heat exchanger (W2, S, D), in particular via the further pipe (R4). <IMAGE>

Description

(57) A device for thermal cracking of a mixture of liquid and gaseous hydrocarbons, leaving at least one pipe line (Pa) in the transmission (Wi) for the mixture, which is connected, if necessary, to the pipe line (P.4) leading from the transmission heat through a flow-controlled bypass conduit (Vi) and a conduit (R4) leading from the heat exchanger (Wi) and into which at least one further conduit (D-ι) leads superheated water vapor leads to a further heat exchanger (VV2) whose output line (R5) leads to a heat exchanger (S) connected thereto, equipped with a catalyst if necessary, leaving the heat exchanger (S) heat exchanger (R6) leads to a cooling and separation device (K + A), characterized in that at least one gas separator is provided in the downstream direction of the heat exchanger (Wi) to separate the gaseous portion from the mixture, the gas line bypass (G1), having a shut-off body (Vi) that can be regulated by flow leads from the isolator of the gauge (G) of the gases to the downstream carrier (VV2), S, D) of the topiots mainly via the downstream conduit (R4).

OMV Aktiengesellschaft

Device for thermal cracking of a mixture of liquid and gaseous hydrocarbons

The invention relates to a device for thermal cracking of a mixture of liquid and gaseous hydrocarbons in heat exchangers.

The naturally occurring hydrocarbon blends generally do not have the desired compositions, so a purely distillation preparation of petroleum products is not sufficient. Taking into account the needs, various processes for the conversion of natural petroleum products have been developed, with thermal cracking processes using and without using catalysts being of particular importance. These thermal transformations are carried out at temperatures between 600 ° C and 860 ° C, depending on the mixture of starting products and the mixture of finished products to be obtained.

In terms of maximum utilization, gaseous hydrocarbons are used in addition to liquid saturated and unsaturated, straight or branched chain hydrocarbons or cyclic or aromatic hydrocarbons. These gaseous hydrocarbons originate predominantly from the facilities for the preparation of cracking and / or treatment facilities. by plants for the production of a wide variety of product mixes. As a rule, these gaseous products are introduced into the liquid hydrocarbon inlets leading to the cracking plant. This, on the one hand, increases the breadth of use of the plant and, on the other hand, results in a significant reduction in pipelines, since it can avoid parallel pipelines running, for gaseous hydrocarbons and liquid hydrocarbons.

Hydrocarbon mixtures should generally be heated to thermal cracking temperatures in several stages. The flow rate in the individual stages, that is, in the heat exchangers, is generally calculated by volume, especially in the first stage, for the partial evaporation of liquid hydrocarbons. In the case of a very large proportion of liquid hydrocarbons, a part of them is introduced into the duct behind the heat exchanger before entering the heat exchanger in order to avoid excessive cooling, e.g. below the dew point of the heat transfer agent, e.g. flue gas. This by-pass certainly results in the pre-heating of the product mixture not being heated to the desired extent, since a small part is led through a heat exchanger.

Apparatus according to the invention for thermal cracking of a mixture of liquid and gaseous hydrocarbons, wherein at least one conduit is conduced into the heat exchanger with a mixture which, if necessary, is fluidly connected to the conduit leading from the heat exchanger via a drainage line with a shut-off body which it may be regulated by flow, and the conduit leading from the heat exchanger and into which at least one further conduit for preheated water vapor leads, in turn, to a further heat exchanger whose exit duct leads to a heat exchanger bound thereto, which is provided with a catalyst and whose outlet leads to the cooling and separation apparatus, in essence, in that, in the direction of flow in front of the heat exchanger, at least one gas extractor is provided to extract the gaseous portion from the mixture, the bypass line a gas line having a flow-regulating shut-off body from a gas separator to a further heat exchanger, p especially through a further pipe line.

By eliminating the gaseous part from the mixture of initial products before the first heat exchanger, it is possible to avoid double inlets for the liquid or liquid. gaseous outputs. It further enters into the heat exchanger a mixture which can be substantially gas free, so that a preferential heat transfer to liquid products can occur which, due to the higher specific heat of the liquids relative to the gases, can be particularly effective. The gas can be piped from the gas separator through a pipeline that leads either to a further heat exchanger or to a crack furnace. The gas line thus serves as a bypass line for the first heat exchanger, which can also regulate the temperature of the heat transfer agent, e.g. flue gas. Particularly high heat transfer can be achieved on the one hand, while avoiding excessive cooling such as flue gas and, consequently, cooling below dew point and associated corrosion.

If the gas separator is designed as a gravity separator, it is easy to remove gaseous parts from the gas-liquid mixture without great pressure loss.

Particularly effective is the separation of gas and liquid by means of a cyclone.

If the gas line from the gas separator, in the direction of flow, leads to the line exiting the heat exchanger before the further steam line, then the product mixture of liquid hydrocarbons of gaseous hydrocarbons and water vapor may already enter the further heat exchanger so that it particularly favors the reduction of the partial vapor pressure in the heat exchanger, which allows the liquid hydrocarbons to evaporate particularly rapidly and to achieve a further high heat absorption in that heat exchanger.

If the gas line from the gas separator leads to a heat exchanger connected to it, that is, to the furnace by cracking, especially to the outlet line from the further heat exchanger, a particularly high proportion of gaseous products in the mixture can also achieve a heat transfer without adverse effect in the subsequent heat exchanger. to gaseous outputs.

If a gas line from the gas separator leads to a further steam line with water vapor, a mixture of water vapor and gaseous products can be obtained which can be introduced into the supply line for the further heat exchanger.

If the gas line from the gas separator leads to a steam superheater, the gas may overheat with the steam.

If an additional bypass line to the heat exchanger is provided, in particular a flow-regulating shut-off body, where that by-pass of the gas separator branches off from the conduit leading to the heat exchanger and preferably leads to the downstream conduit after entry. gas pipelines can also control the surplus of liquid hydrocarbons without pressure overloading the heat exchanger and, if necessary, control them.

Heat exchangers can also be built as groups of heat exchangers.

The invention is further explained by means of drawings and examples.

In doing so, they show:

FIG. 1 in a schematic representation of a cracker furnace with two heat exchanger connected thereto; and FIG. 2 and 3 of the gas extractor in the schematic representation.

In the scheme of the olefin production plant presented in FIG. 1, the pipeline water 1¾ and R combine to convert liquid hydrocarbons (gasoline) or. gaseous hydrocarbons having 2 to 4 carbon atoms in the conduit R ₃ leading to the G gas separator. The liquid products are then piped to the heat exchanger Wj via the pipe line R ₃ . The gaseous products from the G gas separator flow through the gas line G _p which serves as the bypass line for the heat exchanger W ₁ into the conduit R ₄ leading from the heat exchanger. A steam line D _p also leads to this pipeline R ₄ forwarding steam from the steam superheater D. A further heat exchanger W ₂ to which pipeline R ₄ leads is connected to the crack furnace S via an outlet line R ₅ , which is connected behind the heat exchanger. From the cracking furnace S, the R ₆ pipeline leads to the K + A preparation for cooling and separation. The steam superheater, in which steam is produced, the cracker furnace as well as the heat exchangers W _x and W ₂ are made as heat exchangers on the stack of pipes, using flue gas as the medium of the carrier. A gas valve G _p may be provided in the gas conduit G ₄ , which can be controlled by flow and is closed when it is desirable to pass the entire product mixture through the conduit R ₃ to the heat exchanger W ₁ . The G ₂ gas line can also lead to the exit line R _{5 of the} heat exchanger W ₂ , or as a G ₃ gas line directly into the crack furnace. These two gas lines may have valves V ₂ and V ₃ which can be regulated during flow.

If it is desirable to further heat the gas, it can be supplied to the steam superheater D or, if necessary, to the steam generator via G ₄ .

In addition to one or more. more gas pipelines G _t to G ₄ may be provided with a further bypass line U _p which, before the heat exchanger W _t , branches off from the pipe line R ₃ and leads to the pipe line R ₄ behind the heat transfer port W ₄ . This bypass 1¾ has a valve V, which can be controlled by flow.

Through the heat exchanger W ₄ and W ₂ , as well as the steam superheater D and the cracker furnace S, flue gases are used to serve as a heat transfer medium. The flue gases, corresponding to arrow X _t, enter through the crack furnace and then arrows into the HD superheater for high-pressure steam, in which high-pressure steam may be formed which does not need to be fed to the process, as can be seen from FIG. 1. The flue gas then enters the steam superheater O in accordance with arrow X ₃ , into which the process steam is introduced in accordance with arrow Z, too. The flue gas D exits flue gas in accordance with arrow X ₄ into the heat exchanger W ₂ from which it enters, in accordance with arrow X _5, into the boiler KV of the boiler feed water, which is also not required in the process according to the invention. From this preheating KV, the flue gas in accordance with arrow X ₆ exits into the heat exchanger W _x , from which the flue gas is then led to the fireplace in accordance with arrow X ₇ . The arrangement of heat exchangers is carried out in accordance with the required heat potential, with the crack S furnace requiring the highest flue gas temperature, while the W _x heat exchanger requires flue gases with a significantly lower temperature.

The G gas extractor, schematically presented in FIG. 2, has a cylindrical tube 1 which serves as an external container. A tubular conduit R ₃ is passed into this outer vessel through which the product mixture is introduced into a liquid and gaseous state. In cylindrical tube 1, the flow velocity is greatly slowed, with the separation of the gas and liquid phases simultaneously. The liquid phase is discharged through the outlet pipe line R ₃ , while the gaseous phase is discharged through the cylindrical pipe 2, which continues into the gas line G _x , and thus, with the valve V _x open, it enters the pipe line R ₄ .

In the gas separator presented in FIG. 3, there is a cyclone, with the conduit R ₃ leading tangentially to the conical vessel 3. The product mixture moves in the form of a spiral along the outer wall of the vessel downwards, thus separating. The liquid phase is withdrawn through the bottom line R ₃ , while the gaseous phase reaches the outlet via the gas line G _x .

EXAMPLE I

The R ₃ pipeline with a nominal diameter of 80 mm produced 1,625 kg of liquid gasoline and 750 kg of gaseous hydrocarbons having 2 to 4 carbon atoms per hour. A by-pass U _r V heat exchanger W _x was provided _. The upstream product mixture had a temperature of 60 ° C. On exit, it was heated to 250 ° C. 75% by volume of the liquid and 15% by volume of the gaseous phase of the product were passed through the bypass line U _p which was not heated thereby. The product mixture was then supplied via a R ₄ pipe with a nominal diameter of 80 mm into which 1,400 kg / h of steam at 491 ° C was introduced into a W ₂ heat exchanger. The inlet product mixture was heated to 440 ° C in a W ₂ heat exchanger. The product mixture thus heated was then passed to a cracking furnace S through a R ₅ pipe with a nominal diameter of 80 mm. The cracker furnace is designed as a heat exchanger in which the mixture is further heated. A mixture with a temperature of 855 ° C stood out from the R ₆ pipe line.

EXAMPLE 2:

A product mix of 1,750 kg / h in the liquid phase and 750 kg / h in the gaseous phase was transferred to the W ₄ heat exchanger via a R ₃ pipe with a nominal diameter of 80 mm. A gas separator was provided with a gas line G _{r The} product mixture entering the heat exchanger W had a temperature of 60 ° C. On exit, it was heated to 220 ° C. 15% by volume of the gaseous phase and zero liquid phase of the product were passed through the gas line G _x and thus were not heated. The product mixture was then introduced into the W ₂ heat exchanger via a pipe line R ₄ into which 483 ° C steam and 1,300 kg / h was introduced, with a nominal diameter of 80 mm. The inlet product mixture was heated to 450 ° C in a W ₂ heat exchanger. Thus, the heated product mixture was then via pipe R _with a nominal diameter of 80 mm result in the furnace with the cracking. It was further heated in the cracker oven itself. The mixture at a temperature of 855 ° C stood out from the R ₆ pipework.

As illustrated by the comparison of Embodiments 1 and 2, by eliminating the gases in front of the W ₄ heat exchanger, a significantly better heating of the mixture to be supplied by the cracking furnace can be achieved, and further a significant cooling of the heat transfer agent at the exit of the W ₄ laptop heat so that the effect of the cracking furnace can be substantially increased at the same energy input.

For

OMV Aktiengesellschaft:

Claims (8)

1. A device for thermal cracking of a mixture of liquid and gaseous hydrocarbons, leading to a heat exchanger (W _t ) at least one conduit (R ₃ ) for the mixture, which is connected, if necessary, to the conduit (R ₄ ) leading from the transducer heat through a flow-controlled bypass conduit (V) and a conduit (R ₄ ) leading from the heat exchanger (Wj) and into which at least one further conduit leads (DJ for overheated conduit) steam leads to a further heat exchanger (W ₂ ) whose output line (R ₅ ) leads to a heat exchanger (S) connected thereto, equipped with a catalyst if necessary, the output line (R ₆ ) of the exchanger (S) leads to a cooling and separating device (K + A), characterized in that at least one gas separator is provided in the downstream direction of the heat exchanger (W _x ) to separate the gaseous portion from the mixture, the bypass gas line (G _x ) having a shut-off body (VJ, which can be regulated by flow, leads from the gas separator (G) to the downstream heat exchanger (W ₂ , S, D) mainly via the downstream conduit (R ₄ ). A device for thermal cracking of a mixture of liquid and gaseous hydrocarbons according to claim 1, characterized in that the gas separator (G) is designed as a gravity separator. 3. A device for thermal cracking of a mixture of liquid and gaseous hydrocarbons according to claim 1, characterized in that the gas separator (G) is designed as a cyclone. 4. Device for thermal cracking of liquid mixture _; and gaseous hydrocarbons according to one of Claims 1, 2 or 3, characterized in that the gas line (Gj) from the gas separator (G), in the direction of flow, leads before the further line (Dj) for the water vapor into the line (R ₄ ) exiting the heat exchanger (W _t ). Device for thermal cracking of a mixture of liquid and gaseous hydrocarbons according to one of claims 1 to 4, characterized in that the gas line (G ₂ ) from the gas separator (G) leads to a heat exchanger (S) connected thereto, in particular in the outlet conduit (R ₅ ) from a further heat exchanger (W ₂ ). Device for thermal cracking of a mixture of liquid and gaseous hydrocarbons according to one of claims 1 to 5, characterized in that the gas line (G ₂ ) from the gas separator leads to a further pipe line (Dj). Device for thermal cracking of a mixture of liquid and gaseous hydrocarbons according to one of claims 1 to 6, characterized in that the gas line (G ₄ ) from the gas separator (G) leads to a steam superheater (D). Device for thermal cracking of a mixture of liquid and gaseous hydrocarbons according to any one of claims 1 to 6, characterized in that an additional bypass line (Uj) is provided to the heat exchanger (W) which is separated from the pipeline by the gas separator (G) (R ₃ ) leading to the transmitter (WJ of heat, and preferably leading to the downstream conduit (R ₄ ) behind the gas line inlet (G ^. For OMV Aktiengesellschaft: PAT E M L J 23539-I-94 / LZ ABSTRACT Device for thermal cracking of a mixture of liquid and gaseous hydrocarbons A device for thermal cracking of a mixture of liquid and gaseous hydrocarbons, leading at least one pipe conduit (R ₃ ) to the heat exchanger (W) for the mixture, which is connected, if necessary, to the conduit (R ₄ ) leading from the heat exchanger via a bypass line with a flow-regulating shut-off body (Vj) and a conduit (R ₄ ) leading from the heat exchanger (Wj) and into which at least one further conduit (D ^ for superheated water vapor) leads, leads to a further heat exchanger (W ₂ ) whose output line (R ₅ ) leads to a heat exchanger (S) connected thereto, equipped with a catalyst if necessary, with the heat exchanger (S) heat exchanger (R _fi ) into a cooling and separating device (K + A), characterized in that at least one gas separator is provided in the direction of the flow in front of the heat exchanger (W) to separate the gaseous portion from the mixture, the bypass gas line (Gj) being has a shut-off body (V) that can be regulated after the flow leads from the isol gases (G) gases into the downstream heat exchanger (W ₂ , S, D) mainly through the downstream conduit (R ₄ ).