RU2837182C1 - Flare burner for low-calorific gases - Google Patents

Abstract

FIELD: combustion apparatus.

SUBSTANCE: present invention relates to flare units intended for combustion of low-calorific gases (biogas, landfill gases, blast-furnace gases, etc.). Flare unit contains a cup from heat-resistant material filled with metal with high heat conductivity, inside which vertical cylindrical channels are made with tubes from heat-resistant material inserted into them, mixer located at the inlet to the vertical cylindrical channels, including the low-calorie gas supply channels, high-calorific gas supply channels and air supply channels into each of the vertical cylindrical channels, wherein electric ignition plugs are installed inside or at the outlet of several tubes of vertical cylindrical channels, wherein said mixer comprises low-calorie gas feed pipe, high-calorie gas feed pipe and air feed pipe.

EFFECT: increased degree of utilization and efficiency of gas neutralization.

2 cl, 1 dwg

Description

Field of technology to which the invention relates

The present invention relates to flare installations and methods intended for burning low-calorific gases (biogases, landfill gases, blast furnace gases, etc.).

State of the art

A feature of low-calorie gases is their high content of inert gases (for example, nitrogen) and CO2, which leads to a decrease in the calorific value of the gas and the impossibility of combustion in conventional flare burners.

One of the ways to ensure their combustion is to preheat the air supplied to the burner, as well as the gas itself, to a temperature of 500-700 C.

A burner for burning low-calorie gases in a porous ceramic material or in a space filled with ceramic balls is known (RU2125204C1, 20.01.1999). The burner comprises a body including a combustion chamber with an inlet for feeding a gas-air mixture as fuel and an outlet for exhaust gases, wherein the combustion chamber is filled with a porous material, the porosity of which changes along the combustion chamber in such a way that the size of the pores in the direction of the flow of the gas-air mixture increases in such a way that on the boundary surface or in a certain zone of the porous material for the size of the pores and thus for the propagation of the flame, a critical Peclet coefficient is formed, at which a flame can arise, below which the flame is suppressed.

A flare burner is known (RU2619666C2, 17.05.2017), which comprises a cylindrical body with a branch pipe for the ignition and flame control device of the pilot burner, an annular gas manifold installed coaxially in the cavity of the body and protected by a screen with replaceable nozzles, the axes of the tube channels of which are directed at an acute angle to the plane of the burner axis, a gas supply pipeline, an adjustable air duct formed by the central opening of the annular gas manifold and a controlled swirler in it, in the cylindrical body, at the location of the ignition branch pipe, an additional branch pipe is installed, connected to the control nozzle, the body of which is connected by a tube through a needle valve to the annular gas manifold and the gas supply pipeline, and at the outlet from the end opening of the body of the control nozzle, located in the additional branch pipe, a flame control sensor is installed, which does not respond to the flame of the pilot burner, wherein on the side surface of the body of the control nozzle there are Air injection holes and a rotary damper are installed.

The disadvantages of these devices are the complexity of the design, large dimensions, due to the need to pump a mixture of air and gas through them at a low speed, usually not exceeding several meters per second, low degree of utilization and efficiency of gas neutralization.

Disclosure of the essence of the invention

The technical challenge is to create a simple and reliable flare burner that ensures a high degree of utilization and efficiency of gas neutralization.

The technical result consists in increasing the degree of utilization and efficiency of gas neutralization.

The technical result is achieved due to the fact that the flare burner contains a glass made of heat-resistant material filled with metal with high thermal conductivity, inside which vertical cylindrical channels are made with tubes made of heat-resistant material inserted into them, a mixer located at the entrance to the vertical cylindrical channels, including channels for supplying low-calorie gas, channels for supplying high-calorie gas and channels for supplying air into each of the vertical cylindrical channels, wherein electric ignition plugs are installed inside or at the exit of several tubes of the vertical cylindrical channels, and the mixer contains a branch pipe for supplying low-calorie gas, a branch pipe for supplying high-calorie gas and an air supply branch pipe.

In addition, vertical cylindrical channels are made with a diameter of 2-15 mm.

Brief description of the drawings

Fig. 1 - Scheme of a torch burner, side view in section.

The following elements are indicated on the figure:

1 - a glass made of heat-resistant material;

2 - metal with high thermal conductivity;

3 - vertical cylindrical channels with tubes inserted into them made of heat-resistant material for burning high-calorie gas;

4 - mixer;

5 - channels for supplying high-calorie gas;

6 - air supply channels;

7 - electric ignition spark plugs;

8 - low-calorie gas supply pipe;

9 - high-calorie gas supply pipe;

10 - air supply pipe;

11 - channels for supplying low-calorie gas.

Implementation of the invention

The claimed solution can be used in high-temperature flare units and is designed to reduce the negative impact of landfill gas from solid municipal waste landfills and low-pressure associated petroleum gas at fields on the environment by thermally neutralizing these gases and decomposing them into simpler substances. Accordingly, it can be used at solid municipal waste landfills and oil and gas fields in various regions, regardless of the climatic, geological, hydrological and other characteristics of the area. When burning landfill and associated petroleum gas, the following participate in the reaction: carbon monoxide, hydrogen sulfide, ammonia, methane, phenol, formaldehyde, toluene, xylene, ethylbenzene, benzene, mercaptan, nitrogen and oxygen. During the reactions, carbon dioxide, water, chlorine, sulfur dioxide are formed, and nitrogen and oxygen remain, which are not required for the reaction.

The claimed flare burner (Fig. 1) includes a cup (1) made of a heat-resistant material filled with a metal (2) with high thermal conductivity, vertical cylindrical channels (3) with a diameter of 2-15 mm with tubes made of a heat-resistant material inserted into them for burning high-calorific gas, located inside the metal, a mixer (4) for feeding air or gas into the channels, located at the entrance to the channels (3), including channels for feeding low-calorific gas (11), channels for feeding high-calorific gas (5) and channels for feeding air (6) into each of the channels (3), electric ignition plugs (7) located inside or at the outlet of several tubes of the channels (3), wherein in the lower part of the burner, in the mixer, a branch pipe (8) for feeding low-calorific gas, a branch pipe (9) for feeding high-calorific gas and a branch pipe (10) for feeding air are made, wherein one or more channels (3) are intended for feeding high-calorific gas into them gas. Low-calorie gas is supplied to the burner through the low-calorie gas supply pipe 8. High-calorie gas is supplied to the burner through the high-calorie gas supply pipe 9. Air is supplied through the air supply pipe 10.

The number of channels and, accordingly, the number of tubes depends on the gas flow rate supplied for combustion. Their number is calculated based on the condition of ensuring a turbulent flow regime of the gas and air mixture inside the tubes. A turbulent flow regime is necessary for normal heat transfer from the hot walls of the tube to the mixture of low-calorie gas and air inside the tube. To ensure a turbulent flow regime in the tube, the Reynolds number, which characterizes the ratio of inertial forces to viscous forces in the flow of liquid or gas, must be greater than 2300. R e = ρ v L / μ, where ρ is the density of the gas and air mixture, μ is the dynamic viscosity coefficient of the gas and air mixture, v is the characteristic flow velocity, and L is the tube diameter. The density of the low-calorie gas and air mixture is calculated based on the content of various components in the low-pressure gas and air. To do this, the molecular weight of the mixture is first calculated, and then the density of the mixture is calculated using the Clapeyron-Mendelev equation. The Clapeyron-Mendeleev equation for this case is written as: P=rRT/w, where P is the mixture pressure, r is the mixture density, T is the mixture temperature, and w is the mixture molecular weight. For normal combustion of low-calorie gas, it is desirable to select an air-to-gas ratio close to the calculated stoichiometric mixture (a mixture of oxidizer (oxygen) and fuel (combustible components of low-calorie gas), in which there is exactly as much oxygen as is necessary for complete oxidation of the fuel). For example, with a mixture density in a tube of 1 kg/m3, a tube diameter of 10 mm, and a dynamic viscosity of the mixture of 10 ^-5 Ns/m2, the turbulent flow regime is realized at a speed greater than 2.3 m/s. Since the Reynolds number value Re=2300 for the transition of a laminar flow to a turbulent one is a boundary value, therefore it is desirable for maintaining a stable turbulent flow in the tubes that the flow velocity at least twice exceeds the boundary value of the velocity. Thus, in the case under consideration, a minimum flow rate of a gas and air mixture of Q=rvS=1.3 kg/hour can be pumped through one tube, where S is the cross-section of the tube. The length of the tubes and the maximum flow rate will depend on the temperature of the tube wall, due to the number of tubes with high-calorie high-calorie gas burning inside them, as well as on the length of the tubes. Due to the need to ensure the installation of ignition plugs in each tube with high-calorie gas, the number of tubes with high-calorie gas must be minimized, the optimal number of such tubes usually does not exceed 10 pieces. They are arranged in such a way as to ensure, if possible, uniform heating of all the tubes, for example, one tube with a high-calorific gas is placed on the axis of the glass, and the remaining tubes are evenly arranged on a circle with the center on the axis of the glass, the radius of the circle is calculated using special programs for calculating heat transfer in bodies taking into account the energy supply.

For one of the tested burner variants, with a mixture flow rate of air and low-calorie gas of 500 m3/hour, as a result of optimization modeling of heat flows in the proposed burner in the software package using the finite element method, the following burner configuration was obtained: the tube diameter was 15 mm, their number was 40 pieces, the length of the tubes was 1500 mm, 8 similar tubes for high-calorie gas were additionally installed. The wall temperature of the tubes with high-calorie gas was 1000 ° C. Natural methane with a content of 99% methane, 1% ethane, 1% nitrogen mol was selected as the high-calorie gas. Gas with a content of 20% methane, 40% carbon dioxide, nitrogen, 40% mol was used as the low-calorie gas. The combustion temperature of the low-calorie gas was 900° C. For stable combustion of the low-calorie gas, as shown by the simulation of the combustion process of a stoichiometric gas mixture, it is necessary to preheat the low-calorie gas to a temperature of 300° C. Preheating is necessary because an insufficient amount of heat is released during combustion of the low-calorie gas, and this heat is not enough to maintain stable combustion in cases where the gas and air mixture is not preheated. When reducing the proportion of combustible gases in the low-calorie gas, it is necessary to increase its preheating temperature accordingly. However, for each composition of the low-calorie gas, it is necessary to determine the required level of its preheating, since, for example, with the presented gas composition, preheating the gas above 400° C will lead to an increase in NOx compounds in the burner exhaust gases. Modeling of low-calorie gas combustion and determining the required preheating temperature can be carried out in software packages such as HYSYS, ANSYS, etc. Usually the minimum length of the tubes is approximately 100 calibers in diameter. For the burner in question, low-calorie gas is a gas with a content of combustible substances of the alkane series of no more than 20%. High-calorie gas is a gas with a content of combustible substances of the alkane series of more than 70%.

The method of burning low-calorie gases using the said flare burner and, accordingly, its operation is as follows.

Before starting the torch, high-calorific gas enters the burner through the corresponding branch pipe, which enters several tubes made of heat-resistant material through the air mixer. Ignition plugs ignite and further burn the mixture of air and high-calorific gas in these tubes. The heat released during combustion of the high-calorific gas is used to warm up the entire burner structure to a temperature of 600-900°C. After reaching this temperature (determined by a temperature sensor built into a metal with high thermal conductivity), low-pressure gas is supplied to the burner, which mixes with air in the mixer and is directed into vertical cylindrical channels. When passing through the channels, the mixture of air and low-calorific gas heats up to a temperature of 300 - 600°C and ignites inside the tubes. The heat released during combustion of the low-pressure gas is transferred by means of a metal with high thermal conductivity to the low-calorific gas entering through the channel. After the burner reaches the calculated combustion mode, the supply of high-calorific gas stops.

The claimed solution, implemented in the above manner, is simple and reliable, ensuring a high degree of utilization and efficiency of gas neutralization.

Claims (2)

1. A flare burner characterized in that it contains a cup made of a heat-resistant material filled with a metal with high thermal conductivity, inside which vertical cylindrical channels are made with tubes made of a heat-resistant material inserted into them, a mixer located at the entrance to the vertical cylindrical channels, including channels for supplying low-calorie gas, channels for supplying high-calorie gas and channels for supplying air into each of the vertical cylindrical channels, wherein electric ignition plugs are installed inside or at the exit of several tubes of the vertical cylindrical channels, while in the lower part of the burner the mixer contains a low-calorie gas supply pipe, a high-calorie gas supply pipe and an air supply pipe. 2. A flare burner according to item 1, characterized in that the vertical cylindrical channels are made with a diameter of 2-15 mm.