KR820000012B1 - Method for the combustion of waste gases - Google Patents

Abstract

The combination burner consists of a main swirl burner in which gases of very low calorific value such as industrial waste gases can be burned and a secondary burner for ignition and support of the main burner in which fuels with high calorific value such as natural gas or fuel oil can be burned. The flame of the secondary burner will have stability, ignition capability and invulnerability to quenching even in open contact with the swirling waste gas and even when the composition of the waste gas becomes temporarily insufficient to sustain combustion.

Description

Waste gas combustion method

1 is a longitudinal sectional view illustrating a preferred embodiment of the present invention.

2 is a cross-sectional view taken along the line 2-2 of FIG.

3 is a cross-sectional view taken along the line 3-3 of FIG.

4 is a cross-sectional view taken along the line 4-4 of FIG.

5 is a cross-sectional view illustrating a suitable example of the present invention in which a fire chamber of a carbon black particle drum dryer is combined.

The present invention relates to the combustion of industrial waste gases having a relatively low calorific value and includes, but is not limited to, the combustion of waste gases produced in a carbon black plant. Calorie recovery (energy management) or removal of air pollution is the object of the present invention. The lack of natural gas and rising prices have motivated the combustion of these low-heated waste gases to be effective in opening up combustion systems that can meet the need for natural gas or other energy from oil shortages. Cyclone or rotary flow combustors are constructed in a cylindrical combustion chamber with a limited outlet and in the front wall of the combustor, with a vortex burner installed coaxially with the combustion chamber to induce waste gas and air to flow into the combustion chamber. . In certain types of combustors, gas motion is characterized by rotational flow through the entire combustion chamber and extensive axial backflow within the first section occupying about one third of the combustion chamber length. Within this section, the hot combustion products are recycled and mixed with the incoming waste gases and air and raised to temperatures sufficient to maintain above their ignition temperatures. The remaining two-thirds section of the combustion chamber is used for complete combustion of the waste gas.

In various studies on vortex injection, a method of inducing vortex injection into the front wall of a closed cylindrical furnace has been proposed as a device for improving combustion control and control.

In the research paper described below, it is described that it is good to set the ratio between the outlet diameter of the burner chamber and the combustion chamber diameter to 1/4 or more, which is a characteristic feature of the apparatus used in the present invention.

1. Aerodynamic Study of Combustion Space

… Tepro Enerotica 1967.

2. Observation of the Vortex Jet Flow in a Narrow Cylindrical Combustion Chamber

… International Flame Research Bulletin Chapter 4

One object of the present invention is to open a burner which is smaller and cheaper than a combustor consisting of a burner assembly and a large combustion chamber, but is not limited to this, for example in rotary kilns or drums used to dry wet particles for producing carbon black. Many such burners are placed on the walls of an existing room that provide the necessary heat.

In this application, only the ignition section of the combustion chamber consists of a sealed fire-resistant lined cylinder, but combustion is carried out in a dry kiln firebox outside of the cylinder.

In the present application, combustion is required to be maintained at a temperature higher than the temperature generated by waste gas in the low calorific range. That is, 36 to 44 BTU / SCF is required.

Here, the burner array not only provides heat for maintaining the ignition and combustion of the waste gas, but is also required for the carbon black particles when there is no waste gas or when the waste gas has a small amount of heat so that it cannot sustain combustion by itself. In order to provide sufficient heat to the drying drum for drying it is necessary to combine it with an auxiliary burner using natural gas propane oil. Such burners should also be equipped with an ignition flame that uses an auxiliary gas or liquid fuel to ignite inside the burner assembly and to prevent explosions from entering the firebox unburned. The requirement for this auxiliary burner is to have the ability to maintain combustion at high bottoms and vice versa at very low loads, i.e. a large amount of waste gas stream which is difficult to burn is combusted by open contact with the flame. Ability and the ability to ignite them with a ignition flame. The ignition flame should not be affected by the quenched flow at all. Without this ability, there is a risk of explosion during the whole working of the drying drum. It is very important that the burner be fully enclosed within the waste gas burner or extend slightly outwardly and coaxially from the waste gas burner assembly to meet the requirements for design simplicity and dimension limits. The basic problem for realizing these objectives is the proper design and location of the auxiliary gas or oil burner, so that the secondary gas flames are not extinguished.

Conventionally, one or more gas burners have been installed on the burner neck or on top of the combustion chamber to successfully ignite the waste gas. However, this installation does not serve low-level waste gas or, even in small quantities, must be very carefully adjusted for high-quality waste gas growth.

In addition, such an installation does not give a reliable ignition flame. An alternative solution is to have a flame assist burner coaxial with and on top of the waste gas vortex chamber. The auxiliary flame must have a stable source and have an ignition point at the upstream burner inlet of the waste gas vortex chamber, and the auxiliary flame extends across the vortex chamber without colliding with the vortex chamber casing without protection. It must be passed. Acquiring a narrow flame shape of the auxiliary flame within the required stability and dimensional limits will again require gas motion due to vortices. However, this vortex, which is associated with the vortex of the waste gas burner, forms an opposite flow in the center, so that the waste gas penetrates into the source of the secondary flame and extinguishes the secondary flame. If the auxiliary burner is operated in a straight stream, that is, in a non-vortex flow, the flame is too long and in fact, part of the flame is extinguished when it is rapidly cooled by waste gas.

The present invention solves these problems and realizes these objects by employing two different Swirl Numbers (defined later). In other words, the high swell number ("S") is in the range of about 1.5 to 3.0 for low calorific waste gas, and the low swell number is in the range of about 0.25 to 0.50 in the auxiliary fuel burner. Is installed coaxially upstream of the waste gas vortex chamber. The use of a low swell in the auxiliary burner provides a flame which is strongly stabilized at the source by the short backflow zone, but has an outward flow of sufficient strength to form a barrier to the backflow vortex of the waste gas vortex chamber at the outlet of the auxiliary burner. . The result is a fairly stable and capable of igniting under all adverse conditions caused by strongly swirling waste gases. The combustion of waste gas with less than 50 BTU / ft ^{3 of} heat can be successfully performed by a relatively small burner arrangement in which the mixture of waste gas and air is induced to vortex and then flow in a vortex action along a restricted passage. As it enters the short cylindrical combustion chamber. A burner with a heat dissipation rate of 1,500,000 BTU / hour has been developed in such a way that it can be installed in a plurality of firebox walls used to provide a salt for the carbon black wet particle drying drum, which protrudes out of the firebox wall. The length does not exceed 2.5ft (75cm) and the length extending into the firebox is limited to 3ft (90cm).

With reference to FIGS. 1 to 3, the waste gas and air mixture enters the filling chamber 1 through the pipe 2, and before entering the vortex zone 4, the waste gas vortex generator, ie the vortex apparatus 3. Vortex occurs at high speed. This vortex gas-air mixture first enters the combustion chamber through the restriction 8 and then expands and ignites in the cylindrical combustion zone 5 defined by the combustion chamber 7 lined with refractory material. The connection between the restricted inlet 8 and the full width of the combustion chamber 5 can be arbitrarily inclined as shown in FIG. As an alternative, the waste gas and air may be allowed to enter the vortex zone 4 separately without premixing.

The high temperature required to first ignite the waste gas is supplied by an auxiliary burner. The fuel used for this burner flows through the pipe 9 into the combustion zone 10 regulated by a tubing 11 lined with refractory material. The flame of this auxiliary burner, later referred to as an auxiliary flame, is formed and stabilized in the zone 10. The hot combustion products pass narrowly through the vortex zone 4 to provide sufficient mixing with the waste gas in the restricted zone 8; The heat exchange takes place The tub 11 has a length sufficient to further protect the secondary flame and sparks outside the zone 4 which may cause overheating of the metal part of the waste gas vortex generator 3. It extends into the vortex zone 4 to reduce the expansion of the bulge, which also limits the axial dimension.

The auxiliary fuel may be natural gas or oil. The special design of the auxiliary burner end at the end of the fuel pipe 9 is not very strictly regulated. The air for combustion of the auxiliary fuel enters the filling chamber between the burner tube 11 and the housing 12 by the pipe 13 (FIG. 3), causes the vortex movement by the vortex wing 14, and then the restriction part ( Enter zone 10 via 16). First ignition pilot (not shown) of the auxiliary fuel is inserted into the passage 15 as appropriate.

As described above, an important feature of the present invention is the use of a low vortex in the combustion zone 10 of the auxiliary burner and a high vortex in the vortex zone 4. The swell number "S" in zone 10 should be about 0.25 to 0.50, and the swell number in zone 4 should be about 1.5 to 3.0, with about 1.8 to 2.4 being suitable.

The swell number "S" is used as a dimensionless variable to define and control the aerodynamic behavior of the various zones of the combined burner. In this application, this ratio is used as the force on the central axis of each momentum multiplied by the exit radius by the axial outward thrust. In the case of the waste gas vortex generator, the molecular value is determined by the tangential suction speed provided by the vortex device 3 and also by the radius of the circle whose diameter is the distance between the gravity centers of the suction ports. The denominator value is determined by the axial discharge rate through the limiter 8 and the radius of the limiter. These values in the auxiliary burner are each determined by the angular momentum given by the vortex vanes 14 and the outlet flow through the limiter 16 and its radius.

5 is a simplified illustration of a preferred embodiment of the present invention installed in the firebox of a cylindrical rotary drum dryer for drying wet carbon black particles. In commercial carbon black plants, multiple combustors are installed for each drum dryer.

EXAMPLE

In one tire-reinforced carbon black plant, one drum dryer was equipped with eight combustors as shown.

The auxiliary fuel (natural gas) burner pipe 9 is fitted at the downstream end, and the gas is discharged through six holes 1/8 "in diameter radially drilled near the downstream end of the pipe.

Each burner was designed to burn 30,000 to 36,000 cubic feet per hour of waste gas having the composition shown in Table 1.

TABLE 1

Table 2 is a list of representative examples of operating conditions of each combustor.

TABLE 2

The description of the preferred embodiment of the present invention will remind those of skill in the art of various changes. Accordingly, the foregoing description and embodiments are not to be considered limiting, and all changes and modifications in accordance with the described principles are intended to be included within the scope of the appended claims. For example, the specific arrangement or size of the combustor may vary depending on the composition and amount of waste gas being combusted, the type of auxiliary fuel used, and the amount of heat sharing required per burner.

Claims (1)

A method of combusting low-calorie industrial waste gases, characterized in that the gas and air mixture is burned by employing a swell number of about 1.5 to 3.0 so that combustion is caused by the combustion of auxiliary fuel employing a swell number of 0.25 to 0.50. Low calorie waste gas combustion method.

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