JPH0526477Y2 - - Google Patents

Description

[Detailed description of the invention] Purpose of the invention (industrial application field) The present invention is a primary air supply device for combustion equipment, especially a combustion equipment installed between a rotary kiln and a cement raw material calciner on the upstream side thereof. It relates to a device for supplying primary air to a device.

(Prior art) In recent years, as one of the cement firing methods, a rotary kiln and a preheater (usually abbreviated as SP) have been developed to increase the firing capacity of a rotary kiln of the same size compared to the conventional suspension preheater (usually abbreviated as SP) method. A separate calcining furnace and combustion device are interposed between the preheating machine and the heat required for calcining to be separately supplied to increase the calcining rate of the raw materials to over 85%. In a rotary kiln, a New Suspension Preheater (NSP) method was developed to carry out a calcining reaction with a small amount of remaining calcination and heat (November 1973, published by the Japan Industrial Furnace Association, Industrial Heating) Vol.15, No.6, P.12-20).

In this NSP method, the decarboxylation reaction (hereinafter referred to as calcination reaction) process, which requires most of the heat consumed during the firing of cement raw materials, is carried out in an extremely thermally efficient calcining furnace with its own heat source. As shown in Figure 3, in order to reduce the heat consumption of the entire plant,
Air after cooling the clinker, which was conventionally exhausted, is used as combustion air for the calcining burner 101. Since the air after cooling the clinker is fresh air at a relatively high temperature of 600 to 800°C, it can be used as combustion air for the calcining burner 101 as it is. However, since blowers generally cannot withstand high temperatures, they are usually used to pressurize relatively low-temperature air below 200°C, and it is not practical to pressurize and force-feed relatively high-temperature air of 600 to 800°C. It is said to be extremely difficult. Therefore, the combustion device 101 of the conventional calcining furnace 102 for a cement rotary kiln uses induced draft to combine waste gas from the rotary kiln 103 with air supplied from a clinker box 104 downstream of the kiln via a secondary air duct 105. The air is mixed with suction and used as secondary air. The primary air is supplied by increasing the pressure of outside air using a blower 106.

(Problem that the invention aims to solve) However, even if relatively high-temperature secondary air is used, a large amount of outside air at a low temperature of about 20°C is used as primary air, so the stability of fires is reduced. This makes it difficult to use low-quality pulverized coal, and the combustion temperature inevitably decreases.

Therefore, an object of the present invention is to provide a primary air supply device capable of supplying relatively high-temperature primary air, thereby improving combustibility and increasing combustion temperature.

Structure of the Invention (Means for Solving Problems) In order to achieve the above object, the primary air supply device of the present invention supplies secondary air to the cement raw material calcining furnace together with the waste gas of the rotary kiln. A part of the air after heat exchange inside the clinker box is sucked using the ejection speed ejected from the ejector, and is supplied as primary air to the combustion device of the cement raw material calciner.

(Example) Hereinafter, the configuration of our school proposal will be explained in detail based on an example shown in the drawings.

As shown in FIG. 2, the cement firing plant in which the present invention has been implemented is equipped with a cement raw material calcination furnace 2 on the upstream side of a rotary kiln 1 and a clinker box 3 on the downstream side. The furnace 2 and clinker box 3 are connected by a secondary air duct 4, and part of the air in the clinker box 3 used for cooling the clinker is supplied to the kiln burner 5 as secondary air, and part of it is used for calcination of cement raw material. Furnace combustion device (hereinafter also referred to as calcination burner) 6
The air is supplied as secondary air and primary air. Incidentally, the reference numeral 10 in the figure is a blower that forces outside air into the clinker box 3 to cool the clinker.

The secondary air duct 4 is usually provided with a dust collector such as a cyclone 11 installed in the middle to remove clinker particles contained in the air before supplying the air. It is also possible to vertically bend the duct 4 to collect clinker particles contained in the air in the valleys by gravity.

The cement raw material calcination furnace 2 supplies the amount of heat required for calcination from the calcination burner 6 to calcinate the cement raw material and perform a decarboxylation reaction. Typical methods of the cement raw material calcining furnace 2 include an air flow type, a whirlpool type, a jet type, a fluidized bed type, and a combination of these types, and the method is selected as appropriate depending on the purpose etc. . The calcining furnace 2 is connected on the upstream side to a group of cyclones (not shown) in the latter stage, and is provided so as to discharge carbon dioxide separated from the cement raw material in the calcining reaction process to the outside of the system. In addition, on the downstream side of the cement raw material calcining furnace 2,
The secondary air duct 4 and the upstream side of the rotary kiln 1 are connected to each other, and the combined gas of the kiln waste gas supplied through these and the air after cooling the clinker is burned as secondary air for cement raw material calcination. A plurality of furnace combustion devices and calcining burners 6 are installed.

A primary air supply device 7 that supplies primary air to the calcining burner 6 connects the calcining burner 6 and the secondary air duct 4 via an ejector 8.
By increasing the pressure of outside air and blowing it out, a part of the secondary air flowing through the secondary air duct 4 is sucked and supplied as primary air. The ejector 8 is
It does not need to have a special structure, and a known structure can be used.Although not shown, it usually consists of a combination of an ejection nozzle and a bench lily-shaped suction pipe, and uses the ejection speed of the fluid to blow around the nozzle. It has a mechanism to suck in gas. This ejector 8
A blower 9 is connected to the nozzle so that outside air can be pressurized and blown out at room temperature, while a secondary air doubt 4 is connected around the bench lily-shaped suction pipe so as to open around the nozzle, and the suction A pipe discharge port is connected to a calcining burner 6. Therefore, when the outside air is pressurized and blown in by the blower 9, the secondary air from the clinker box 3 in the secondary air duct 4 is sucked and fed under pressure to the calcining burner 6.

The calcining burner 6 includes all burners that burn heavy oil, gas, pulverized coal, or a mixture thereof as fuel, but burners that use heavy oil or pulverized coal as fuel are usually employed.

According to the primary air supply device configured as described above, when outside air pressurized by the blower 9 is injected into the nozzle of the ejector 8, air at a temperature of 600 to 800°C flowing inside the secondary air duct 4 is sent from the nozzle at high speed. It is sucked in and mixed with the blown outside air to a temperature of 500 to 600℃.
The hot air is supplied to the calcining burner 6 as primary air. By supplying primary air at a relatively high temperature (500 to 600° C.), the amount of primary air used can be reduced compared to the case where only outside air is used, for example, less than half the amount of conventional air used.

Effects of the Invention As is clear from the above explanation, the primary air supply device of the present invention is capable of supplying air after heat exchange in the clinker box that is supplied as secondary air to the cement raw material calcining furnace together with the waste gas of the rotary kiln. A portion of the air is sucked in using the high-speed outside air flow ejected into the ejector and supplied as primary air to the combustion equipment of the cement raw material calciner. 600℃), making it easy to supply high-pressure primary air, significantly reducing the amount of primary air used compared to using only outside air, making fires more stable, and raising the combustion temperature to prevent calcination reactions. This makes it possible to increase the calcination rate and facilitate the use of low-grade fuel.

[Brief explanation of the drawing]

FIG. 1 is a principle diagram showing an embodiment of the primary air supply device of the present invention, and FIG. 2 is a schematic diagram of the entire cement firing plant. FIG. 3 is an explanatory diagram showing an example of a conventional NSP calcining furnace. 1...Rotary kiln, 2...Cement raw material calcination furnace, 3...Clinker box, 4...Secondary air duct, 6...Calcination burner (combustion device), 7...
Primary air supply device, 8... Ejector, 9... Blower.

Claims (1)

[Scope of utility model registration request] The suction pipe side of the ejector is connected to a secondary air duct which connects the clinker box and the cement raw material calcining furnace and supplies the air after heat exchange in the clinker box as secondary air, and also communicates with the nozzle of the ejector. connecting a blower, and further connecting a discharge port of the ejector and a combustion device of a cement raw material calciner;
A cement raw material characterized by blowing outside air pressurized to a relatively high pressure into an ejector, sucking in a part of the secondary air supplied from a clinker box, and supplying it as primary air to a combustion device of a cement raw material calciner. Primary air supply device for combustion equipment for calciner.