RU2606298C1 - Exhaust system - Google Patents

Abstract

FIELD: gas industry; technological processes.

SUBSTANCE: invention relates to systems for removing nitrogen oxides from gases and may be used for cleaning exhaust gases of gas turbine engines, for example, gas pumping units, gas-turbine power plants. Exhaust system includes a gas duct with a device for feeding a reducing agent, spacer, diffuser and exhaust pipe, having a selective catalytic reduction catalyst. At inlet and outlet of spacer there is a grid with cells in form of channels. Diffuser is equipped with longitudinal plates attached by their ribs to inner surface of diffuser and form with each other and with walls of diffuser conical gas channels with opening angle of 7–10 degrees. Grids can be arranged with increasing number of cells in area of maximum speed of exhaust gases.

EFFECT: invention provides aerodynamic uniform flow of exhaust gases at inlet of selective catalytic reduction catalyst.

1 cl, 4 dwg

Description

The invention relates to systems for cleaning gases from nitrogen oxides and can be used for cleaning exhaust gases of gas turbine engines (GTE), for example, gas pumping units, gas turbine power plants.

In many countries of the world, legislative norms have been adopted on the maximum permissible content of certain substances in the exhaust gases generated during the operation of a gas turbine engine. This is mainly about substances whose release into the environment is undesirable. One of these substances is nitric oxide (NO _x ), whose share in the exhaust gases should not exceed the legislatively established maximum permissible values. Reducing the content of nitrogen oxides in the exhaust gases of a gas turbine engine due to changes in the internal structure of the engine is possible only within limited limits, which often do not satisfy the legislatively established maximum permissible values. This creates the need to use additional methods to reduce the value of NO _x in the exhaust gases of a gas turbine engine.

One such method is a method for selective catalytic reduction (SCR) of nitrogen oxides. SLE is represented by chemical processes for the reduction of nitrogen oxides with a reducing gas to its simplest components. The final reaction product is safe components - water vapor and nitrogen.

Known RF patent No. 2424042 "Method for the selective catalytic reduction of nitrogen oxides in the exhaust gases generated by the operation of the internal combustion engine, and the exhaust system (exhaust)", where the exhaust system has a selective catalytic reduction catalyst (SCR catalyst), a device for supply of at least one of the following reagents (hereinafter referred to as UPR)

a) reducing agent (ammonia);

b) the precursor of the reducing agent (urea solution).

The essence of the method is that a reducing agent (reducing agent), which can be used as a solution of urea or ammonia, is injected with the help of the exhaust gas into the exhaust stream to the SCR catalyst. When a gas passes through an SCR catalyst, reduction reactions occur with varying degrees of intensity, as a result of which nitrogen oxides pass into molecular nitrogen. The feed rate and flow rate of the reducing agent are determined by the concentration of NO _x at the outlet of the turbine engine.

Known RF patent No. 2208184 "Gas pumping station" in which the gas exhaust path (exhaust system) includes a duct, diffuser, adapter (spacer), exhaust pipe.

A useful model is also known (RF patent No. 45474) "System of exhaust and heat recovery of exhaust gases of gas turbine plants", which is the closest analogue of the invention. The exhaust system directly includes: a flue, an adapter (spacer), a heat recovery unit, the flow part of which is made in the form of a diffuser (diffuser), a chimney (exhaust pipe).

Hot exhaust gases from the engine through the gas duct, passing through the spacer and diffuser, enter the exhaust pipe, at the outlet of which they are emitted into the atmosphere.

The installation of UPR in the flue and SCR catalyst in the exhaust pipe of the exhaust system specified in the prototype, allows you to implement the method of selective catalytic reduction for purification of exhaust gases of gas turbine engines from NOx.

In this case, the disadvantage of this utility model is that this exhaust system does not ensure the effective operation of the SLE method, because due to the design features of the flow part of the exhaust system (turns, sharp expansions / contractions), the required aerodynamic flow uniformity over the cross-section of the SCR catalyst is not provided, which is the most important condition for its effective operation, and is also a requirement of STO 70238424.13.040.40.001-2008 for installations purification of flue gases from nitrogen oxides using selective catalytic reduction (SCR) technology.

The objective of the invention is to provide improved cleaning of exhaust gases of a gas turbine engine by increasing the efficiency of applying the SLE method.

The technical result is to ensure aerodynamic uniformity of the exhaust gas flow at the inlet to the SCR catalyst by introducing additional structural elements into the flow part of the exhaust system elements (diffuser and spacer).

The technical result is achieved by the fact that in the exhaust system, including a gas duct with a reagent-reducing agent supply, a spacer, a diffuser and an exhaust pipe containing a selective catalytic reduction catalyst, gratings with cells in the form of channels are installed at the inlet and outlet of the spacer, and the diffuser is equipped with longitudinal plates fastened by their ribs with the inner surface of the diffuser and forming conical gas channels with an opening angle of 7-10 degrees between themselves and with the walls of the diffuser.

It is possible to perform gratings with cells in the form of channels with an increase in the number of cells in the region of the maximum exhaust gas velocities generated during the operation of the gas turbine engine.

The installation of gratings with cells in the form of channels at the inlet and outlet of the spacer according to experimental data makes it possible to align the exhaust gas parameters at the inlet to the diffuser, namely, the exhaust gas flow rate due to the resistance created by the gratings and the unidirectional exhaust gas flow (without return flows) per counting the shape of the cells in the form of channels.

An increase in the number of cells in the region of maximum exhaust gas velocities creates an increased resistance to exhaust gas flow in this region, which additionally causes the exhaust gases to be distributed more evenly over the surface of the grilles.

The supply of the diffuser with longitudinal plates, fastened by ribs with its inner surface of the diffuser and forming conical gas channels with an opening angle of 7-10 degrees between themselves and with the walls of the diffuser, eliminates the formation of new vortices (eliminated after the exhaust gases passed through the spacer, at the input and output of which gratings with cells in the form of channels) in the exhaust gas flow and will ensure aerodynamic flow uniformity over the cross-section of the SCR catalyst at the inlet.

The opening angle of conical channels of 7-10 degrees is due to the fact that when the opening angle is less than 7 degrees, the increased number of longitudinal plates creates additional resistance in the gas path of the exhaust system, and the opening angle of more than 10 degrees does not guarantee the elimination of the formation of new vortices in the exhaust gas flow and ensuring aerodynamic uniform flow across the cross section at the entrance to the SCR catalyst.

The invention is illustrated in FIG. 1, FIG. 2, FIG. 3 and FIG. four.

In FIG. 1 shows a longitudinal section through an exhaust system.

In FIG. 2 is a top view of a spacer with grilles installed at its inlet and outlet.

In FIG. 3 shows a side view of a spacer with grilles installed at its input and output.

In FIG. 4 - isometry of a spacer with grilles installed at its input and output.

An exhaust system including a gas duct 1 with a device for supplying a reagent-reducing agent 2, a spacer 3, a diffuser 4, and an exhaust pipe 5 containing a selective catalytic reduction catalyst 6, while gratings 7 with cells in the form of channels 8 are installed at the inlet and outlet of the spacer 3, and the diffuser 4 is equipped with longitudinal plates 9, fastened by ribs with the inner surface of the diffuser 4 and forming conical gas channels 10 with an opening angle of 7-10 degrees between themselves and with the walls of the diffuser 4. In this case, the gratings 7 with cells in the form of channels 8 are made with an increase in the number of cells in the region of maximum exhaust gas velocities 11.

The device operates as follows.

The exhaust gases from the gas turbine engine enter the exhaust duct 1 of the exhaust system, at the inlet of which the reagent-reducing agent is injected with the reagent-reducing agent feed device 2. After that, the gas stream mixed with the reducing reagent enters into the spacer 3, at the inlet and outlet of which there are grilles 7 with cells in the form of channels 8. Then a uniform unidirectional gas stream enters the diffuser 4, provided with longitudinal plates 9, fastened by ribs with the inner surface of the diffuser and forming between themselves and from the walls The diffuser has conical gas channels 10 with an opening angle of 7-10 degrees, after which it enters the SCR catalyst 6 installed in the exhaust pipe 5.

Thus, the present invention provides aerodynamic uniformity of the flow of exhaust gases at the entrance to the SCR catalyst.

Claims (2)

1. The exhaust system, including a gas duct with a device for supplying a reagent-reducing agent, a spacer, a diffuser and an exhaust pipe containing a selective catalytic reduction catalyst, characterized in that gratings with cells in the form of channels are installed at the inlet and outlet of the spacer, and the diffuser is equipped with longitudinal plates fastened by their ribs to the inner surface of the diffuser and forming conical gas channels with an opening angle of 7-10 degrees between themselves and with the walls of the diffuser. 2. The exhaust system according to claim 1, characterized in that the grilles are made with an increase in the number of cells in the region of maximum exhaust gas velocities.

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