RU2324108C1 - Mode of operation of a vertical prismatic furnace - Google Patents

Abstract

FIELD: heat and power engineering.

SUBSTANCE: basis of the method is to increase the combustion quality and operational reliability by exclusion of temperature irregularity in active burning zones to exclude slugging and increase heat absorption on the heating surfaces when the burner block is started. During this method, when all burning blocks are operational, the blocks are directed tangentially to a conditional circle. The fuel-air mixture is release through burner 2 in furnace 1. When burner 2 is switched off in one of the corners of furnace 1, the burners of the operating block are directed tangentially to a conditional circle, whose diameter can be determined by the relation d_n=(0.257-0.0825·n)·a_m, d_n - diameter of the conditional circle, tangent to which an n^th working burner is directed; n - the number of the burning block, counting from the switched off burner in the direction of the gas direction; a_m - depth of the combustion chamber.

EFFECT: use of thermal power station steam boilers in furnaces during lignite slug combustion.

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Description

The invention relates to a power system and can be used in the furnaces of steam boilers of thermal power plants when burning brown coal slag.

A known method of operation of a steam generator (AS USSR No. 901731, class F23C 5/00, 1980) with multi-tier burners located, in which to eliminate temperature irregularities, the fuel consumption through the burners of each tier is increased from tier to tier in the direction from top to bottom. This method allows to reduce only the thermal unevenness in height, when the maximum gas temperature recorded in the region of the upper tier of the burner decreases due to an increase in thermal stress in the lower tiers, after a corresponding redistribution of fuel. However, the temperature unevenness caused by the shutdown of part of the burners of each tier is maintained, which causes slagging and reduces the reliability of operation.

The closest in technical essence to the proposed method is the method of operation of a vertical prismatic firebox of square cross section with a multi-tiered block angular arrangement of the burners with a tangentially circumferential direction, in which to eliminate the temperature irregularities that occur when the burner unit is turned off, the amount of recirculation gases distributed to each burner unit , is determined depending on the location of the disabled unit (AS USSR No. 1703913, class. F23C 9/08, 1992). The disadvantage of this method is that such a distribution leads to an increased local supply of recirculation gases (for example, the amount of recirculation gases supplied to the fourth burner unit, starting from the flue gas disconnected in the direction of travel, exceeds 25% of their total consumption). This causes the torch to ballast this burner with low-temperature combustion products and leads to disruptions in the fuel combustion process and an increase in heat loss with mechanical underburning. In addition, in this method, the violation of the tangential aerodynamics of the burner jets caused by the shutdown of the burner block is not eliminated, namely, that the burner jets deviate from predetermined motion paths, some of which are located in dangerously close to the furnace screens, while others, on the contrary, deviate to the center fireboxes. Moreover, the location of the most and least heat-stressed sections in the volume and on the surface of the walls of the combustion chamber depends on the location of the disconnected burner block. The displacement of the high-temperature combustion core due to this shutdown leads to the fact that some screen heating surfaces are slagged (towards which the torch has shifted), and in other screens the thermal perception decreases (from which the torch has moved away to the center of the combustion chamber).

The basis of the invention is the task of improving the quality of combustion and operational reliability by eliminating temperature unevenness in the active combustion zone to prevent slagging and to increase the thermal perception of screen heating surfaces when the burner unit is turned off.

This is achieved by the fact that in the method of operation of a vertical prismatic furnace with an angular multi-tiered block arrangement of the burners by guiding the last tangentially circumferential circle when the burner block is turned off (by shutting down the burner block we mean stopping the flow of the fuel-air mixture through this block into the furnace), the burners in the working blocks are sent tangentially conditional circles, the diameters of which are set in accordance with the dependence:

d _n = (0.257-0.0825N) a _m ,

where d _n is the diameter of the conditional circle tangentially directed by the nth working burner block;

n is the number of the burner block, starting from the next one, which is switched off during the movement of gases;

and _m is the depth of the combustion chamber.

In the course of the experimental studies, it was found that the distinctive feature of the operation of a vertical prismatic furnace with an angular multi-tiered block arrangement of burners by directing the latter tangentially circumferential circumference is the deviation of the burner jets from the geometric axis directed tangentially to the conventional circle with a diameter of 0.1a _m , where and _m is the furnace depth. When you turn off the burners of one block, the high-temperature core of the torch is shifted from the center of the furnace towards the idle block, which is shown in figure 1, which shows a horizontal section of a vertical prismatic furnace in plan. Such a bias gives a doubly negative effect. Firstly, the approach of the torch to the screens contributes to their intensive slagging, and, secondly, the removal of the torch from opposite screens reduces their thermal perception. In addition, the experimental results showed that at any angle of rotation of the burners α≥52 ° the rotational motion is unstable, as a result of which a secondary effect occurs - the precession of the axis of rotation of the flow core around the geometric axis of the vertical channel. On the other hand, setting the angle of rotation of the burners α <45 ° for fireboxes of square section with an angular tangential arrangement of the burners can lead to a violation of the rotational motion due to the possible impact of adjacent burner jets.

Thus, the optimum angle of rotation of the burners of a tangentially conventional circle lies within 45 ° <α≤52 °. A change in the angle of rotation of the burners causes a corresponding change in the diameter of the conditional circle tangentially to which the burners are directed. Therefore, by varying the rotation angle of each working burner block depending on the position of the disconnected block, which corresponds to their direction along the tangent to circles of different diameters, it is possible to reduce the consequences of the deviation of the burner jets from predetermined paths and to reduce the temperature unevenness in the sections of the furnace.

Figure 2 shows a boiler with a vertical shielded prismatic firebox, in which the proposed method is implemented; figure 3 is a section aa in figure 2.

The steam boiler contains a vertical prismatic firebox 1 with burners 2 installed in each corner in a semi-block fashion, which are oriented tangentially to the conditional circle.

The method of operation of a vertical prismatic furnace is as follows. During operation of all burner units, the air-fuel mixture is fed through them into the furnace. When the burner block is turned off in one of the corners of the combustion chamber (by turning off the burner block it means stopping the flow of the fuel-air mixture through this block into the furnace), the burners in the working blocks are sent tangentially to conventional circles whose diameters are set in accordance with the dependence

d _n = (0.257-0.0825N) a _m ,

where d _n is the diameter of the conditional circle tangentially directed by the nth working burner block;

n is the number of the burner block, starting from the next one, which is switched off during the movement of gases;

a _m is the depth of the combustion chamber.

When the burner unit is turned off, the total fuel and air flow to the furnace remains the same as in the case of operation of all burner units and is distributed in equal amounts to the operating units. The indicated change in the direction of the burners of different blocks, when one of them is turned off, allows you to equalize the temperature difference in the sections of the combustion chamber. So the difference in the values of the density of the incident radiation flux at one height level in the center of the screens is not more than 10 kW / m ² . A similar value is obtained during operation of all burner blocks.

An example of a specific implementation of the proposed method of operation of a prismatic furnace equipped with a tangential angular block multi-tiered arrangement of burners can be the furnace chamber of the E-500 boiler of Krasnoyarsk CHP-2.

During operation of all burner blocks, they are directed tangentially to a conventional circle with a diameter equal to 1.1 m (the depth of the furnace is 11 m). When you turn off one burner block, the direction of the working blocks is changed according to the presented dependence.

The burners of the first block, counting from the flue gas disconnected in the direction of travel, direct a tangentially conventional circle with a diameter of 1.9 m.

The burners of the second unit, counting from the flue gas disconnected in the direction of travel, direct a tangentially conventional circle with a diameter of 1.0 m.

The burners of the third block, counting from the flue gas disconnected in the direction of travel, direct a tangentially conventional circle with a diameter of 0.1 m.

Thus, the proposed technical solution allows to achieve the objective of the invention to improve the quality of combustion and operational reliability by eliminating temperature irregularities in the volume of the combustion chamber, thereby reducing the slagging intensity and increasing the thermal perception of the screen surfaces at the places of approaching and removing the torch, while reducing the number of shutdowns of the boiler to razlakovka.

Claims (1)

The method of operation of a vertical prismatic furnace with an angular multi-tiered block arrangement of burners by directing the latter tangentially to a circumferential circle, characterized in that when the burner block is turned off, the burners in the working blocks are directed tangentially to conventional circles, the diameters of which are set in accordance with the dependence d _n = (0.257-0.0825N) a _m , where d _n is the diameter of the conditional circle tangentially directed by the nth working burner block; n is the number of the burner block, starting from the next one, which is switched off during the movement of gases; a _m is the depth of the combustion chamber.

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