The way the implementation process of the fischer-tropsch synthesis (options) and the selection method of the stationary structure of the solvent in the reactor slurry

 

(57) Abstract:

The invention relates to the field of chemical technology and can be used for the synthesis of marginal and unsaturated hydrocarbons with a preliminary separation of multicomponent, multiphase mixtures at the outlet of the reactor at a fraction of the desired composition, the formation of liquid stationary reaction medium, optimization of the Fischer-Tropsch process. In a reactor containing a liquid solvent with suspended therein a catalyst, and served WITH H2return of the condensed products of the synthesis reactor, and the temperature in the reflux condenser or a change in the share of condensed reaction products are returned to the reactor in amounts not exceeding the total number of condensable products from the reactor outlet, change the composition is returned to the reactor condensate. To maintain a stationary part of the solvent regulate the amount and the composition is returned to the reactor liquid products of the reaction. 3 c.p. f-crystals, 1 tab., 3 Il.

The invention relates to the field of chemical technology and can be used for the synthesis of marginal and unsaturated hydrocarbons with a preliminary separation by MegaCom the lines of the reaction medium, optimization of the Fischer-Tropsch process.

Currently proven and probable reserves of natural gas significantly exceed the reserves of oil, so the creation of new, complex technologies of processing of synthesis gas into liquid fuel, the synthesis of olefins and paraffins is highly relevant task in the world, including Russia. In addition, the only effective way to obtain heavy paraffins, as well as the main process of obtaining hydrocarbon fuels from natural gas remains a process of the Fischer-Tropsch synthesis.

Modern methods of creating new technologies and ways of implementation processes based on the principles of mathematical modeling. To do this, using modern knowledge of the physico-chemical foundations of process (base catalysis, kinetic regularities of complex reactions, thermodynamics of phase transformations), are computational analogues of technological schemes and processes to effectively carry out the optimization of technology at the design stage, to choose the most effective ways and means to implement the process.

A key element of technology for hydrocarbon fuels in the process Viseu, therefore, specifies the main elements of the technology for production of synthesis gas. A complex mixture of products obtained in the reactor, in turn, determines the selection of key process steps that must be followed for the reactor block.

Currently in industry for the synthesis of CFT uses several types of catalytic reactors and methods of the implementation process. In recent years, an increasing attention is paid to the way the implementation process in the reactor with a three-phase suspended layer, the so-called process in slurry reactor, especially since, as the advantages of this method became apparent when its industrial implementation on the plant SASOL-II. (Satterfield, C. N. , Huff, G. A. Usefulness of a slurry-type Fischer-Tropsch reactor for processing synthesis gas of low hydrogen - carbon monoxide ratios. Can. Jour. Chem. Eng., 1982,v 60, N 1, p. 159-162; Lang X., Akgerman, A., D. B. Bukur Steady state Fischer-Tropsch synthesis in supercritical propane. Ind. Eng. Chem. Res. 1995,v. 34, N 1, P. 72-77; Jager B., R. Espinosa. Advances in low temperature Fischer-Tropsch synthesis. Catalysis Today 23 (1995) 17-28).

A known method of forming solvent liquid products of FT synthesis in slurry reactor, we adopted as analogue (Lang X., A. Akgerman, D. B. Bukur Steady state Fischer-Tropsch synthesis in supercritical propane. Ind. Eng. Chem. Res. 1995, v. 34, N 1, P. 72-77; Jager B., R. Espinosa. Advances in low temperature Fischer-Tropsch wells, IL, 1954, 516; The Fischer-Tropsch and related syntheses. Storch H" Golambic N., Anderson R. New York - London, 1951); Saxena S. C. Bubble column reactors and Fischer - Tropsch synthesis. Catal. Rev. -Sci. Eng v 37, N 2, P. 227-309, 1995).

The way the implementation process of the Fischer-Tropsch synthesis in a reactor of this type is to supply the source of synthesis gas in the volume of liquid reaction products in the solvent (hereinafter - solvent) in which the suspended catalyst. The original synthesis gas in the form of bubbles passes through the suspension, where it reacts on the catalyst with the formation of light and heavy hydrocarbons and water. Heavy hydrocarbons, mainly remain in the liquid phase and removed from the reactor together with a solvent and a catalyst in an amount to provide a constant level of solvent in the reactor. Light and part of the heavy hydrocarbons, unreacted gases and water are carried away by the outgoing gas from the reactor, proceed in the separation device. For the separation of the formed light hydrocarbons of motor fuel, diesel and heavy fractions, for the Department of water applied complex technological complex.

There is a method of implementation of the process and formation of solvent in the reactor Fischer-Tropsch process, we adopted for the prototype (D. B. Bukur, S. A. Patel, X. Lang. Fixed bed, belonging to the class of three-phase reactors - gas-liquid-solid catalyst. In this reactor finely-divided catalyst suspended in the liquid phase, the catalyst particles are maintained in fluidized condition by mixing the liquid phase of the gas bubbles and stirrer. Gas-vapor phase, containing unreacted CO and H2with saturated vapors of the reaction products leave the reactor and enters the condenser where it is condensed high-boiling reaction by-products when the temperature of the condenser is returned to slurry reactor.

The disadvantages of the prototype include the following.

1. The number returned in the reactor condensate is not regulated, depends on the temperature of the condenser, the reaction rate.

2. The stationary part of the solvent is formed only by the choice of the initial composition of the solvent, temperature or pressure in the reactor, but since the temperature and pressure in gas-liquid systems - mutually dependent parameters, control can only be one of them, and then only in a narrow range of its changes.

The invention solves the task of creating a way of pre-separation of the reaction products Centerenergo composition of the solvent.

Task pre-separation solved: regulation fraction is returned to the reactor condensed products (reflux) in the amount not exceeding the total number of condensable products from the output of the reactor; the changing composition of the returned condensate.

The task of forming a stationary part of the solvent provides the desired selectivity and productivity of the target hydrocarbon fraction, is solved by choosing the number and composition returned to the reactor liquid product.

In Fig.1 presents a schematic diagram illustrating methods of separation and composition of solvent in the reaction of the Fischer-Tropsch synthesis. Here the synthesis gas stream 0_G, with a given ratio of CO/H2served in the synthesis reactor (block B1). Here comes the return flow of condensate 3_L obtained in column (block B2), after separation of the water.

The flow of gas 1_G after the reactor is fed to the cooling in the reflux condenser. Here, when the temperature of the dephlegmator (T2) is the condensation of a part of the synthesis product. The composition of the formed condensate is rigidly connected phase equilibrium with the temperature. Obrazovavsheesya its second part, stream 4_L, serves for further processing. The ratio of flow of reflux 3_L to flow 34_L ask coefficient . This option, as the temperature of the dephlegmator T2that changes the composition of the condensate, are the control parameters of the process.

In the synthesis conditions, at temperatures 530-550 K entering the reactor dry synthesis gas is continuously saturated hydrocarbon vapors which leave the reactor together with the gaseous reaction products. As a result, when a large evaporation, stream 1_L can become negative, which is equivalent to a continuous decrease of the volume of the liquid solvent in the reactor. The reflux stream compensates for the entrainment of the liquid phase from the reactor and provides a stationary liquid phase in the reactor.

The table lists the process parameters, which were calculated and the obtained samples. Parameters such as temperature, pressure, space velocity, the ratio of H2/CO in the feed gas constant support.

The invention is illustrated by the following examples.

Example 1. As a source of solvent in the reactor using octacosane (C28H58) with a melting point 334,3 K, the boiling temperature of 610 K

In Fig. 2(a,b) shows the distribution of hydrocarbon fractions in the output streams, respectively, when =1 and =0.5 in. When =1 we form two facing the target stream from the reactor: the fluid flow (1 L) and the flow of gas after a dephlegmator (2-G). If 1 > > 0, the number of output streams is three, since the previous two is part of the flow (4 L), not returned to the reactor.

We consider the case = 1, Fig. 2a. In upcoming threads there is a clear separation of the spectra for light and heavy fractions. Thus, in contrast to open-circuit, reflux provides the ability to get separation into light and heavy hydrocarbon fraction.

In the case of < 1, Fig.2b as mentioned above, select three fractions of semi-products from the reactor divided into light, medium and heavy hydrocarbons. Thus, the number of reflux significantly affect the process of separating hydrocarbon products of the synthesis faction.

Example 2. Vary the composition of the return of the condensed products by changing the temperature in the reflux condenser, which carried out the condensation of the gas leaving the reactor. In Fig. 2b, 3 (a,b) shows the distribution of hydrocarbon fractions in the output streams 2-G, 4-L the changing composition of the condensate as a result of increasing the temperature of the reflux condenser, the separation becomes more clear, spectra of light and heavy hydrocarbon fractions further diverge in different directions. Thus, by varying the composition of the condensate is returned to the reactor, affect the degree of separation of the products at the reactor outlet of the Fischer-Tropsch synthesis.

Example 3. To select a stationary part of the solvent in slurry reactor Fischer-Tropsch synthesis regulate the composition and the proportion of liquid hydrocarbons returned to the reactor. Since the fractional composition of the output stream 1-L of the reactor corresponds to the fractional composition of the solvent, from Fig. 2(a, b) and 3 (a,b) indicate that the regulation of the proportion of liquid hydrocarbons and component composition is returned to the reactor liquid hydrocarbons leads to a change in the composition of the solvent.

As can be seen from the examples, the proposed method allows the separation of the reaction products of the Fischer-Tropsch synthesis at the exit of the reactor for several hydrocarbon fractions, forming a stationary part of the solvent.

1. The way the implementation process of the Fischer-Tropsch synthesis in slurry reactor, comprising feeding into a reactor containing a liquid solvent with suspended therein a catalyst, gases, CO and moderadamente change the composition of the returned condensate.

2. The way the implementation process of the Fischer-Tropsch synthesis in slurry reactor, comprising feeding into a reactor containing a liquid solvent with suspended therein a catalyst, gases, CO and hydrogen, the return of the condensed products of synthesis in a reactor, characterized in that the proportion of condensed reaction products are returned to the reactor, change in the amount not exceeding the total number of condensable products from the output of the reactor, which leads to changes in the composition is returned to the reactor condensate.

3. The selection method of stationary fractional composition of the solvent in slurry reactor Fischer-Tropsch synthesis, which in return condensable products of synthesis, characterized in that regulate the composition is returned to the reactor, the liquid reaction products and regulate the proportion returned to the reactor liquid products of the reaction in an amount necessary to maintain a stationary part of the solvent.

 

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