JPS6249097B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for desulfurization in a 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 liquid or gaseous fuels, so when applied to the desulfurization of exhaust gas that contains a large amount of dust, such as exhaust gas from a solid combustion furnace, the desulfurization equipment may be clogged with dust or desulfurization may occur. This led to problems such as a decline in the rate. As a solution to this problem, a dry in-furnace desulfurization method was proposed in which a solid Ca-containing SOx absorbent such as calcium carbonate (limestone), slaked lime, or dolomite is directly injected into the furnace. However, since this method directly supplies the absorbent into a high-temperature oxidizing atmosphere, the reaction rate of Ca is extremely low at less than 15%, making it difficult to put it into practical use.

The present invention was made in view of the above points, and an object of the present invention is to provide a combustion furnace desulfurization method with an extremely high desulfurization rate.

The desulfurization method according to this invention uses HCl gas at a temperature of 150
It is characterized by allowing the Ca-containing SOx absorbent to absorb the SOx at a temperature in the range of ~500°C, and supplying the same absorbent into the furnace at an internal temperature of 900 to 1300°C.

In HCl gas absorption into Ca-containing SOx absorbent,
If the temperature is below 150°C, low-temperature corrosion of the absorbent supply pipe and other parts will occur, whereas if the temperature is above 500°C, high-temperature corrosion will occur. Therefore, the above temperature is limited to a range of 150 to 500°C. Adjustment of this temperature range is achieved by heating the Ca-containing SOx absorbent or heating the HCl gas. As the fuel, solid fuel such as pulverized coal, which is obtained by pulverizing coal, is often used, but this is not limiting.

If the temperature inside the furnace is below 900℃, the SOx absorption reaction will take a long time or it will not be practical. When the temperature inside the furnace exceeds 1300℃, the reaction rate of Ca decreases. Therefore, the temperature inside the furnace is limited to 900 to 1300℃, and the particularly suitable temperature is
The temperature is 1000-1200℃. CaCO ₃ , Ca(OH) ₂ , dolomite, and the like are often used as Ca-containing SOx absorbents.

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

In the horizontal cylindrical furnace shown in FIG. 1, numeral 1 denotes a furnace body consisting of a cylindrical peripheral wall 2, a front wall 3 and a rear wall 4 provided at both ends thereof, and is covered with a water jacket for absorbing heat. 5 is an opening made in the center of the front wall 3, and has a front protrusion 6 for supplying secondary air. Reference numeral 7 denotes a burner arranged in the center of the front protrusion 6 facing inward of the furnace, from which a mixture of pulverized coal and primary air for fuel transportation is supplied. Reference numeral 8 denotes a wind box provided on the front side of the front wall 3, which communicates with the inside of the furnace through an opening 5. Reference numeral 9 denotes an absorbent supply pipe arranged from the center of the length of the peripheral wall 2 to the axial center of the furnace, and has a nozzle 10 facing the burner at its tip. Reference numeral 11 denotes a blower for transporting the absorbent, to which the base end of the absorbent supply pipe 9 is connected. 12 is an absorbent supply feeder provided in the supply pipe 9; 13 is a heater provided in the absorbent supply pipe 9 between the blower 11 and the feeder 12; and 14 is an absorbent supply feeder provided between the feeder 12 and the furnace main body 1. This is an HCl gas supply pipe connected to pipe 9.

FIG. 2 shows a modification of the combustion furnace, in which the heater 13 is installed in the HCl gas supply pipe 14.

FIG. 3 shows a second variant of the combustion furnace. This furnace 21 is a box-shaped large vertical furnace, which is also covered with a water jacket, and has a secondary air supply port for combustion at the lower end of the front wall 22, which has the same structure as that of the combustion furnace shown in FIG. 23, a burner 24, and a wind box 25 are provided, and a mixture of pulverized coal and primary air for fuel transportation is supplied from the burner 24. Also Kazebako 2
An absorbent supply pipe 26 is disposed on the front wall 22 above 5, and the supply pipe 26 includes a blower 27 at the base end, a heater 28, an absorbent supply feeder 29, and an HCl gas supply pipe 26, as in the case of FIG. A supply pipe 30 is provided.

Experiment 1 A horizontal cylindrical furnace (inner diameter 1.5 m, length 7
m), pulverized coal (200 m) is transferred from burner 7 into the furnace.
Kg/h) and primary air were supplied, and secondary air was further supplied into the furnace from the wind box 8 to carry out combustion. The oxygen concentration in the exhaust gas is 4.5%, and SO ₂ before desulfurization
The concentration of was 900ppm.

On the other hand, CaCO ₃ is supplied as an SOx absorbent from the absorbent supply feeder 12 into the furnace at a ratio of Ca/S (equivalent ratio) = 3.0 at a temperature in the range of 150 to 500°C, and HCl gas is supplied on the CaCO ₃ supply path. was supplied and absorbed into CaCO ₃ (in-furnace reaction time 1.7-2
seconds). The furnace temperature was adjusted to a predetermined value in the range of 800 to 1400℃, and the Ca reaction rate (CaSO ₄ /
CaCO ₃ ) was measured. The above operation was also repeated without supplying HCl gas. The results of these experiments are summarized in the fourth
As shown in the figure. As is clear from the figure, the SOx absorbent showed high reactivity at the furnace temperature of 900 to 1300°C, especially at 1000 to 1200°C.

Experiment 2 Next, the temperature inside the furnace was adjusted to 1000℃, and the SOx absorbent was adjusted to a predetermined value in the range of Ca/S (equivalence ratio) = 1 to 4 and supplied (reaction time = 2 seconds). The conditions were the same as in Experiment 1, and the Ca reaction rate at each Ca/S value was measured. The above operation was also repeated without supplying HCl gas. The results of these experiments are shown in FIG. As is clear from the figure, a higher Ca reaction rate was shown when HCl gas was supplied than when it was not supplied.

As described above, according to the desulfurization method of this invention,
Since HCl gas is absorbed into the Ca-containing SOx absorbent within a predetermined temperature range, corrosion of the absorbent supply pipe due to HCl gas can be avoided. Furthermore, the desulfurization rate is determined by the temperature
The temperature is extremely high at 900-1300°C, and the reaction time is sufficient on the order of seconds.

[Brief explanation of the drawing]

Figures 1, 2, and 3 are vertical cross-sectional views showing the combustion furnace, Figure 4 is a graph showing the relationship between furnace temperature and Ca reaction rate, and Figure 5 is a graph showing the relationship between Ca/S equivalence ratio and Ca reaction. It is a graph showing the relationship between rates. 7, 24... Burner, 9, 26... Absorbent supply pipe, 14, 30... HCl gas supply pipe.

Claims (1)

[Claims] 1 HCl gas containing Ca at a temperature range of 150 to 500℃
A combustion furnace desulfurization method characterized by absorbing SOx in an absorbent and supplying the absorbent into the furnace at a furnace temperature in the range of 900 to 1300°C.