JPS58193013A - Desulfurization performed in solid fuel combustion furnace - Google Patents

Abstract

PURPOSE:To efficiently desulfurize exhaust gas after combustion of solid fuel containing dust in high concentration, by feeding desulfurizing agent to the primary combustion zone of reducing atmosphere formed on the upstream side of the secondary combustion air feeding port. CONSTITUTION:The mixture of pulverized coal and fuel transfer air is fed into a furnace from a burner 7. Then, the primary combustion air is fed into the furnace from a wind box 8 to make the air ratio below 1.0. In addition, practically theoretical secondary combustion air is fed into the furnace from a nozzle 9. As a result, the secondary combustion zone b is formed on the downstream side of the nozzle 9, while the primary combustion zone a is formed on the upstream side of the nozzle 9. The primary combustion zone a is in the reducing atmosphere in the temperature of 900-1,300 deg.C, so that it provides the furnace with the optimum condition to perform desulfurization. Then, a desulfurizing agent is fed into the furnace from a nozzle 10, and desulfurization in the furnace is taken place effectively.

Description

[Detailed description of the invention] This invention relates to an in-furnace desulfurization method in a solid combustion furnace.

Sulfur oxides (hereinafter referred to as SOX) generated when sulfur-containing fuel is burned are a substance that causes pollution, so there is a need for a method to effectively remove them. A technology has been proposed or put into practical use. However, all of these methods target liquefied or gaseous fuels, so if they are applied to desulfurizing exhaust gas that contains a large amount of dust, such as exhaust gas from a solid combustion furnace, they may cause furnace clogging due to dust or a decrease in the desulfurization rate. This led to problems such as As a solution to this problem, a dry in-furnace desulfurization method has been proposed in which a solid SOx absorbent such as limestone or slaked lime hedromite is directly injected into the furnace. However, in this method, the absorbent is directly supplied into the high-temperature oxidizing atmosphere, so S
Ox absorption is poor, and as a result, a large amount of absorbent is required.

The present inventors investigated the cause of the low efficiency of conventional in-furnace desulfurization and obtained the following findings. In other words, when the atmosphere inside a normal furnace is an oxidizing atmosphere but the oxygen concentration is very low, 1 to 5% or less, 9 o
At a temperature of about o℃, Na2O+SO2+ 1/'202 → Na2SO4m
m a l1lCaO+SO2+1/202 →Ca
SO4* 11 @ +21 reaction is difficult to occur. On the other hand, in a reducing atmosphere, Na2O + H2S - *Na2S + H2O11 in the high temperature range of 900-1300℃
@ @ (31CaO+H2S −+ CaS +H2
0* 11 @ (4) CaO+CO8-+CaS+
CO2@ @ −[51CaSO4+4CO−+Ca
S +4CO2@ @ -+61Na20 +SO2+
It was found that sulfides such as 3C-+NazS +3CO...[7] are mainly produced, and sulfides such as Na2S s OaS are more stable than sulfates such as Na2SO4 and CaSO4. Therefore, in order to increase the amount of CaS produced, the reaction formula [31[41+51 +61 (7+
All we have to do is shift the equilibrium of 900 to the right.
H2S is a reducing gas in the temperature range of ~1300℃
It can be seen that it is better to increase the concentration of gases such as , CO8, and Co, and to supply a desulfurizing agent to the reduction region.

This invention has been made based on the above knowledge, and an object of the present invention is to provide a desulfurization method that can efficiently desulfurize even when applied to solid fuel combustion exhaust gas containing a high concentration of dust. With the goal.

In the following explanation, the air ratio refers to the ratio of the actual amount of air to the theoretical amount of air required for combustion, and in the front-back direction, the left side is the front, and the right side is This side will be referred to as the rear side.

The desulfurization method according to the present invention is a two-stage combustion method in which combustion air is divided into two parts and supplied into the furnace. It is characterized by supplying an agent.

In the air two-stage combustion method, powdered fuel and air for transporting the fuel are supplied into the furnace from a burner installed on the front wall.
Combustion air is divided into two parts and supplied into the furnace to form a primary combustion zone with a reducing atmosphere upstream from the secondary combustion air supply port, and a primary combustion zone with a reducing atmosphere downstream from the supply port. This is a combustion method that forms a secondary combustion zone.

The desulfurization agent is supplied to the secondary combustion zone through a desulfurization agent supply port provided in the furnace wall between the primary combustion air supply port and the secondary air supply port.

Pulverized coal, which is made by pulverizing coal, is often used as a fuel. In addition, as a desulfurizing agent, Na2(1'03, CaCO
3. Alkali such as Ca(OH)2 and dolomite are often used.

First, the structure of the combustion furnace used in this invention will be explained.

In Fig. 1, (1) is a furnace body consisting of a cylindrical peripheral wall (2) having a heat absorption jacket, a front wall (3) and a rear wall (4) provided at both ends thereof, and (5) is a front wall. Inside (3)
It has an opening in the center and a primary combustion air supply port (6) projecting forward. (7) is the primary air supply port for combustion (
6) is a burner placed in the center facing the furnace, from which a mixture of pulverized coal and air for fuel transportation is supplied. (8)
is a wind box provided in the front of the front wall (3), which communicates with the inside of the furnace via the primary combustion air supply port (6). (9) is a plurality of secondary air nozzles for combustion provided slightly toward the rear wall from the center of the length of the peripheral wall (2), and aOI is a secondary air nozzle for combustion provided on the upstream side of the secondary air nozzle (9) for peripheral wall (2). A plurality of desulfurizing agent nozzles, 01) provided in the peripheral wall (2) are flues provided at the rear end of the peripheral wall (2).

In the combustion furnace having the above structure, a mixture of pulverized coal and fuel transporting air is supplied from the burner (7) into the furnace. Primary air for combustion is supplied from the colander box (8) into the furnace, and the air ratio is kept below 1.0.

Also, a substantially stoichiometric amount of combustion 2 is supplied from the nozzle (9) into the furnace.
Next, supply air. As a result, a primary combustion zone (a) is formed upstream of the nozzle (9), and the nozzle (9)
A secondary combustion zone (b) is formed further downstream. Since the primary combustion zone (IL) is a reducing atmosphere with a temperature of 900 to 1300°C, it has optimal conditions for in-furnace desulfurization.

Therefore, a desulfurizing agent is supplied into the furnace from the nozzle C1O to effectively perform desulfurization in the furnace.

FIG. 2 shows a modification of the combustion furnace. This furnace (2)
is a box-shaped large vertical furnace, and a primary air supply port for combustion and a burner (241) and a wind box (c) of the same structure as the combustion furnace shown in Fig. 1 are installed at the lower end of the front wall (2). A mixture of pulverized coal and air for fuel transportation is supplied from the burner, and primary air for combustion is supplied from the wind box (c).A secondary air nozzle for combustion is installed on the front wall above the burner. An example is provided in which a desulfurizing agent nozzle is provided on the front wall (A) between the nozzle and the burner.In this case as well, a reducing atmosphere is provided upstream of the secondary combustion air nozzle (A). A primary combustion zone (0) is formed, and a secondary combustion zone (d) is formed downstream of the nozzle (to).At that point, a desulfurizing agent is added to the primary combustion zone (c) with the help of the nozzle. supply

Figure 3 shows the desulfurization method in the two-stage air combustion method and the desulfurization method in the single-stage combustion method according to the present invention, with an oxygen concentration of 3%, CaO/SO2, and Na2O/80.
2 shows the relationship between furnace temperature and desulfurization rate at each equivalent ratio of 4. As is clear from the figure, according to the desulfurization method of the present invention, the desulfurization rate can be significantly improved.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of a combustion furnace showing an embodiment of the present invention, FIG. 2 is a vertical cross-sectional view of the front part of the furnace showing a modified example, and FIG. 3 is a graph showing the relationship between furnace temperature and desulfurization rate. It is. End of July 72, 1980 Mr. Kazuo Wakasugi, Commissioner of the Patent Office, The Life of Liao Case, Patent Application No. 76, No. 2 of 1980
Title of the invention In-furnace desulfurization method in a solid combustion furnace 3 Relationship with the case of the person making the amendment Patent applicant 11 Address 1-6-14 Edobori, Nishi-ku, Osaka Name 9 Name (511) Hitachi Zosen Corporation 4th representative Director
Non-human 4 persons 5 Date of amendment order Showa year month month 6
Number of inventions increased by amendment 7 Subject of amendment Column 8 for detailed explanation of the invention in the specification Supplement i1. contents of

Claims (2)

[Claims] (1) In the air two-stage combustion method where combustion air is divided into two and supplied into the furnace, a desulfurizing agent is supplied to the primary combustion zone of the reducing atmosphere formed upstream from the secondary combustion air supply port. An in-furnace desulfurization method in a solid combustion furnace characterized by: (2) The method according to claim 1, wherein the temperature range of the primary combustion zone is 900 to 1300°C.