LT6433B - Catalytic polluted gas treatment device and method - Google Patents

Abstract

This invention relates to gas cleaning devices and methods, specifically to catalytic gas treatment devices, which are intended for gas purification from nitrogen oxides and carbon monoxide by using catalysts, created by plasma spraying method. The aim of the invention to improve the construction of the device, to extend the exploitation capabilities and to increase the cleaning efficiency. Catalytic gas treatment device has two purification stages, consisting of two interconnected channels, equipped with catalysts. First catalyst is used for gas purification from nitrogen oxides. During this process, a lack of oxygen is maintained by combustion camera, which is located before the first channel. The second catalyst is intended for cleaning gas from carbon monoxide, which generates during the first stage, by adding additional oxygen to the channel. Both catalysts has cylindrical shape, in which the rolled up corrugated catalytic foil is placed. Foil is covered by various metal oxides, even hardly melting, or zeolites. Both catalysts are covered by electric heating elements to maintain high temperature (550-650 oC).

Description

FIELD OF INVENTION

The present invention relates to a plant for the treatment of contaminated gas and to a process for the purification of contaminated gas from nitric oxides and carbon monoxide by the use of plasma sprayed catalysts.

TECHNICAL LEVEL

Catalytic treatment of contaminated gases and the process can be used in virtually all power plants which carry out heat generation and fuel combustion processes which release large quantities of pollutants such as nitrogen oxides and carbon monoxide into the environment. A catalytic cleaner for polluted gases is a cost-effective and environmentally friendly device for reducing pollutant emissions to air.

A major disadvantage of catalytic treatment plants for the reduction of nitrogen oxides and carbon monoxide in the flue gas is that the degree of conversion of carbon monoxide and nitrogen oxides depends on the amount of oxygen in the combustion products and the temperature, e.g. carbon monoxide reduction occurs at elevated oxygen concentrations and increases with increasing combustion product temperature and oxygen concentration, whereas nitrogen oxide concentration does not decrease but increases with combustion product temperature and oxygen concentration. In order to solve this problem, the design of the catalytic purifier for the contaminated gas needs to be modified, i.e. an additional oxygen delivery mechanism should be provided.

The working principle of the present invention is directly dependent on specific catalysts. The preparation of catalysts is based on the process of producing catalytic coatings by forming molten materials on the substrate (Lithuanian Patent No. LT4869B). One of the most widely used coatings forming methods in industry and research is plasma spraying. Plasma spraying, among other heat treatment methods, ensures high coating rates and the ability to form coatings of various materials. Coatings consist of oxides of metals (even heavy metals) and zeolite. Plasma spray catalysts are characterized by high cleaning efficiency and economy.

The prototype of the present invention is a catalytic purification reactor for contaminated gas (Russian Patent Application No. RU2194570). The invention relates to the purification of contaminated gases from nitrogen oxides and organic impurities, the device comprising a housing with inlet and outlet ports. The internal volume of the reactor partition is divided into two chambers, on which a layer of an inert nozzle with catalysts is placed on a special lattice, between which are arranged electric heating elements. The baffle is located between the upper and lower chambers, which are interconnected by a vertical pipe-mixer. The catalyst layers and inert nozzles are preheated to 280-380 ° C prior to purification. The cold scrubbed gas passes through the catalyst and inert nozzle layers in the first chamber. At the same time, the gas is heated to a temperature of 280-380 [deg.] C., at which the rate of the selective purification reaction is sufficiently high. The contaminated gas flow through the spray manifold is fed to a substance (reducer) which is mixed in a mixer. The reaction mixture enters the catalyst bed in a second chamber for purification from nitrogen oxides. The heat of the reacted mixture is absorbed by the nozzle. The mixture is removed to the atmosphere via a side nozzle.

The main disadvantage of the described prototype is that the cleaning reaction requires a reagent (reductant) which requires constant addition and which requires qualified service and maintenance. It has been observed that the unit does not provide thermal insulation which results in significant heat loss to the environment. In addition, NO and _X produce large quantities of CO in industry and energy, which must be reduced by supplying additional oxygen to a system that is not present in the prototype. Also, the temperature of 280-380 ° C is too low and must be raised to ensure high cleaning efficiency.

THE SUBSTANCE OF THE INVENTION

The object of the present invention is to improve the design and method of a contaminated gas purification plant so that not only the concentration of nitrogen oxides in the exhaust gas but also the concentration of carbon monoxide can be reduced.

The design and method of the advanced catalytic treatment plant for contaminated gas allows the reduction of nitrogen oxide and carbon monoxide concentrations. The unit has two stages consisting of two sequentially interconnected channels in which the catalysts are mounted. The purification principle is based on the conversion of nitric oxides in the first catalyst, which maintains the oxygen deficiency conditions achieved with the gas combustion chamber, and the conversion of carbon monoxide in the second catalyst, which increases the oxygen concentration to a certain extent through the oxygen supply port. The channels are equipped with plasma sprayed catalysts, which are of high efficiency and economy compared to analogues. Experimentally it has been found that high efficiency of cleaning of contaminated gas from NO _X and CO is achieved when the temperature of combustion products in the ducts is very high. At a temperature of 550-650 ° C in a catalytic scrubber supported by electric heating elements, the surface of the catalytic coatings from which the catalysts are made becomes chemically active and the conversion of pollutants occurs through complex chemical reactions. The unit is provided with an automatic control unit that regulates the temperatures and oxygen concentration in the unit's ducts and determines the cleaning efficiency of the system. The unit also automatically optimizes the operation of the entire system, maintains or modifies the required conditions for the conversion of pollutants to increase cleaning efficiency.

DESCRIPTION OF THE DRAWINGS FIG. a longitudinal sectional view of a catalytic gas purifier of the present invention;

Fig. a cross-sectional view of a cylindrical catalyst with corrugated foil wrapped therein.

DETAILED DESCRIPTION OF THE INVENTION

The catalytic gas purifier consists of a polluted gas supply duct 1, an oxygen deficiency combustion chamber 2, a combustion gas inlet 3, a pollutant concentration sensor 4, a temperature sensor 5, a catalytic gas purifier housing 6, first channel 7, for For reducing NO _X concentration, cylindrical catalyst 8 for reducing NO _X , electric heating element 9 of first channel, thermal wool layer 10, gas channel 11, second channel 12 for reducing CO concentration, additional oxygen supply nozzle 13, second cylindrical catalyst 14, for CO reduction, second channel electric heating element 15, purified gas concentration sensor 16, exhaust fan 17, purified gas duct 18, automatic control unit 19, corrugated foil 20, housed inside cylindrical catalysts 8 and 14.

Principle of device operation

The stream of contaminated gas enters the first catalytic channel of the gas treatment plant

7 to reduce NO _X concentrations. The duct is fitted with a cylindrical catalyst 8 for reducing the concentration of NO _X , which is composed of a series of corrugated foils 20 wrapped therein, coated with plasma oxides and oxides of various metals (including heavy metals). A gas concentration sensor 4 is provided to measure the gas concentration before purification, and the gas temperature is measured by a temperature sensor 5. Sensors 4 and 5 are connected to a control unit 19 which automatically determines the concentration and temperature of the incoming gas. The contaminated gas stream oxygen concentration is relatively low, namely 0.05 to 0.1% by the conduit 7 takes place _NOX purification and also involves CO. Such oxygen deficiency conditions are achieved by passing a contaminated gas stream through the gas combustion chamber 2, additionally by supplying combustion gas through the conduit 3. After the first stage of purification of the contaminated gas, the pollutant stream through the gas passage 11 from the first passage 7 to the second passage 12 is provided with a second cylindrical catalyst 14 for reducing CO concentration produced using the same materials and technologies as the first catalyst 8. designed to reduce NO _x concentration. In order to ensure the purification of CO in the system, an additional oxygen supply nozzle 13 is used and the oxygen concentration is increased to 0.60.7%. Oxygen is supplied to the system according to the concentrations set in the automatic control unit 19. The purified gas is removed to the atmosphere by means of an exhaust fan 17 through a purified gas duct 18 and its concentration is measured by a gas concentration sensor 16. The processed data is displayed on the screen of the automatic control unit 19. Because effective cleaning can only be achieved at high temperatures of 550-650 ° C combustion products, the temperature is controlled by first and second 12-channel electric heating elements 9 and 15. The elements are connected to an automatic control unit 19 and controlled by the unit. temperature modes. The automatic control unit 19 optimizes the operation of the entire cleaning system. At low cleaning efficiency due to various factors, e.g. If the oxygen concentration is inadequate or the system temperature is too low, the unit automatically increases or decreases the required parameters to ensure an increase in cleaning efficiency and maintain its high level. In order to reduce heat loss to the environment, the catalytic gas treatment unit is insulated with a layer of thermal insulation wool 10.

Claims (8)

DEFINITION OF INVENTION 1. A catalytic gas purifier having a contaminated gas supply duct, a gas exhaust fan, a housing with a catalyst insulating material, to purify the gas duct, characterized in that it has two contaminated gas purification steps consisting of two interconnected channels ( 7) and (12) comprising cylindrical catalysts (8) and (14), wherein the first catalyst (8) is for purifying contaminated gas from nitrogen oxides (NO _X ) while maintaining oxygen deficiency and the second catalyst (14) is for contaminated gas. purification from the carbon monoxide (CO) formed in the first step by supplying additional oxygen. 2. A device according to claim 1, characterized in that the cylindrical catalysts (8) and (14) are formed by depositing inside them corrugated foils (20) coated with oxides of various metals, including heavy metals, zeolite. 3. Apparatus according to claim 2, characterized in that the cylindrical catalysts (8), (14) are coated with electric heating elements (9) (15) which maintain a temperature of 550-650 ° C therein. 4. Apparatus according to claim 1, characterized in that a gas combustion chamber (2) is provided in front of the first conduit (7) with a combustion gas inlet (3) for increasing the oxygen deficiency in the first conduit (7). 5. Apparatus according to claim 1, characterized in that a second conduit (12) is provided with a nozzle (13) for supplying additional oxygen. 6. A method for purifying contaminated gas, comprising the step of purifying the contaminated gas from nitrogen oxides (NO _X ) and carbon monoxide (CO), comprising two stages of purifying the contaminated gas, wherein in the first step the first conduit (7) oxides (NO _X ), maintaining oxygen deficiency and, in a second step, purifying contaminated gas in the second passage (12) from the carbon monoxide (CO) formed during the first step by providing additional oxygen to the system. 7. The method of claim 6, wherein the oxygen concentration in the first pass is reduced to 0.05-0.1%. 8. The method of claim 6, wherein the oxygen concentration in the second passage is increased to 0.6-0.7%.