SU1710117A1 - Reaction element of heterogeneous catalytic reactor - Google Patents

Abstract

The invention relates to devices for carrying out heterogeneous catalytic reactions, in particular catalytic steam reforming of natural gas, can be used in heterogeneous catalytic processes with significant thermal effect in fixed bed reactors and allows to intensify heat and mass transfer from the wall. reaction tube. For this, the metal mesh of the reaction element is made up of a series of successive mesh layers with an increment from the inner layer to the outer mesh pitch so that the mesh spacing of the outer mesh layer is 2-6 mesh cells of each subsequent inner layer. 3 ill. The invention relates to devices for carrying out heterogeneous catalytic reactions, in particular, catalytic steam reforming of natural gas, and can be used in heterogeneous catalytic processes with a significant thermal effect in fixed bed reactors. The reaction element, known as Raschig rings with an outer diameter of 15 mm, an inner diameter of 7 mm, a height of 15 mm, made of alumina with nickel-containing components and promoting additives. It is used in the form of a fixed bed of packing packed in reaction tubes, with external heat supply through the wall. The reaction elements in the form of cylinders, balls, seats, etc. are also known. The gas mixture fed into the pipes reacts on the surface of the fixed catalyst bed, the resulting gas is removed from the reactor. The disadvantages of this type of packing are relatively low porosity of the fixed layer ( with the exception of the near-wall zone), high hydraulic resistance, unevenness of the velocity field over the cross section of the reactor, low thermal conductivity of the packing material and, therefore, low effective heat conduction the uniformity of the layer, the difficult process of heat transfer, the unevenness of the temperature field over the cross section of the reactor, the low overall selectivity of the process and the low specific productivity. The reaction element of the heterogeneous catalytic reactor with a fixed catalyst bed is the closest to the technical essence and effect achieved. x || oi • ^ > &

Description

In the form of a metal mesh tube mounted on a mandrel coaxially with the reaction tube.

At the ends of the metal mesh tube, outer rings are fixed, between which a fabric catalyst is wound.

However, the known reaction element is characterized by insufficient heat and mass transfer from the reaction tube, due to the fact that in the case of catalyst winding in several layers, the carrier layers of the catalytically active component (mesh, fabric, etc.) are additional diffusion and thermal resistance, which leads to underloading catalyst and reduce the yield of the target product.

The aim of the invention is to intensify heat and mass transfer from the wall of the reaction tube.

In the reaction element, made in the form of a metal mesh tube mounted on a mandrel coaxially with the reaction tube, the metal mesh tube is made up of a series of successive layers of the mesh with a catalytically active layer and an increment from the inner layer to the outer cell step so that the mesh pitch of the outer layer the grid is 2-6 steps of cells of each subsequent inner layer.

A comparative analysis with a known element allows us to conclude that the proposed reaction element of a heterogeneous-catalytic reactor differs from the well-known one in that the metal mesh tube is made up of a number of consecutive grid layers with a catalytically active coating and an increasing step from the inner layer to the outer cell in such a way that the step the cells of the outer layer of the grid is 2-6 cells of each subsequent inner layer.

It has been experimentally proven that the choice of the step of the cells of the outer layer, which is less than 2 steps of the cells of each subsequent inner layer, leads to a decrease in the convective washing of all subsequent inner layers, reducing the availability of the catalytic surface of all subsequent layers, reducing the fraction of the radiant component of the heat flux from the wall of the reaction tube to deep layers of the grid with a catalytically active coating due to overlapping of the inner grid of the outer one. Increasing the pitch of the cells of the outer layer of the grid (more than 6) with respect to the pitch of the cells of each subsequent inner layer leads to

reducing the proportion of the catalytically active surface on each subsequent layer of the grid and reducing the efficiency of deposition of the catalytically active component on the grid with a large cell size. In addition, it is possible to increase the hydraulic resistance on the rougher surface of the cell.

Figure 1 shows the reaction tube with the reaction element, a longitudinal section; figure 2 shows the reaction element: in FIG. 3, layers of the grids of the reaction element.

The reaction element is made in the form of a metal mesh tube 1 installed in the reaction tube 2. The metal mesh tube 1 is assembled from a series of consecutive wound on the mandrel 3 layers 4 and 5 of the mesh, and the pitch of the cells from the inner layer 4 to the outer layer 5 increases in this way such that the ratio of the mesh pitch of the outer layer of the mesh to the pitch of the cells of each subsequent inner layer is 2-6. The mandrel can act as a reaction element with a catalytically active coating, or it can be made in the form of a catalytically active tube, for example, assembled from rings, catalyst granules, etc.

Teterogenecatalytic reactor with a reaction element works as follows.

The initial vapor-gas mixture enters the reaction tube 2 and enters into a conversion reaction on a fixed catalytically active layer deposited on the grids of the reaction element 1. The reaction elements 1 are loaded into the reaction tube 2 in an amount necessary for the required degree of completion of the conversion reaction. The reaction of steam reforming of natural gas is carried out by supplying thermal energy through the wall of the reaction tube 2. Due to the fact that the reaction element is made of a set of grids with high thermal conductivity, temperature gradients over the catalyst layer are minimal despite the high endothermicity of the reaction. Ensuring the required pitch of the grids of which the reaction element is made allows good achievement of the good accessibility of the catalytic surface of the convective and radiant components of the heat flux, as well as the flow of reagents, while the degree of irradiation of each subsequent layer of the reaction element mesh is rather high and is 55 60 % of free surface. This leads to the fact that the temperature of the inner layers of the grids of the reaction element practically does not differ from the temperature of the outer layer.

Claims (1)

Formula and sampling The reaction element is heterogeneous. a catalytic reactor with a fixed catalyst bed, made in the form of a metal mesh tube mounted on a mandrel coaxial to the reaction pipe, characterized in that, in order to intensify heat and mass transfer from the wall of the reaction pipe, the metal mesh tube is composed of a series of successive layers with a catalytically active layer and increasing from the inner layer to the outer step of the cells, and the step of the cells of the Outer layer of the grid is 2 to 6 steps of the cells of each subsequent inner layer. FIG. 1 FIG. g