JPS59131695A - Production of inert gas for mill - Google Patents

Abstract

PURPOSE:An inert gas of high temperature and high humidity is converted into low temperature and low humidity, then the resultant is heated at a specific temperature to high temperature and low humidity, thus producing the titled gas which enable safe crushing of high humidity and explosive coal and stabilized drying, conveying and classification. CONSTITUTION:For example, the exhaust gas from the boiler 3 is used as an inert gas of high temperature and high humidity, sent through the pipe 46 to the gas cooler 6 where the gas is cooled and dehydrated. The low temperature and low humidity inert gas is heated with the heater 9 so that the gas temperature becomes higher than the dew point of the inert gas measured after the outlet of the 10 to prepare a gas of light temperature and low humidity. The resultant inert gas is sent to the mill where it is used in crushing, drying, conveying and classification of the coal fed from the hopper 12.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing inert gas for mills for crushing, drying, feeding and recovering coal.

In general, inert gas is used as a heat source for drying, feeding, and recovering coal during dry pulverization.

In recent years, pulverized coal has been used as an alternative fuel by pulverizing coal for the purpose of saving oil. In many cases, the powder is pulverized and dried by blowing it through a so-called inert gas mill where the temperature is usually 15 degrees or lower.

As the inert gas, combustion exhaust gas from boilers, cement kilns, etc. is most often used, but in this case there are the following problems.

(1) Inert gas contains a large amount of moisture generated by the combustion reaction, and combined with the moisture still generated from the coal, the relative humidity in the inert gas becomes extremely high, which reduces the grinding and drying performance of the mill. descend.

(2) As mentioned above, if the relative humidity is high, a slight drop in temperature after the mill exit will cause it to drop below the dew point, causing the pulverized coal to adhere to pipes, dust collectors, etc. during feeding and separation after pulverization. This may cause problems such as explosions.

The present invention has been made in view of the above circumstances, and includes:
Safely crushes coal with high moisture content and the risk of explosion.
Another object of the present invention is to provide a method for producing inert gas for a mill that provides stable pulverization, drying, feeding, and fractionation performance.

In order to meet the second objective, the present invention is based on an inert gas production method in which coal is pulverized in a mill to produce pulverized coal, which is then dried and fed while being separated and recovered. The high-temperature, high-humidity inert gas is cooled and dehumidified in a gas cooler to produce a low-temperature, low-humidity inert gas, and then the inert gas is heated by a heater so that the temperature of the inert gas after the mill outlet is equal to or higher than the detected dew point temperature of the inert gas. The mission is to send it to the mill as a high-temperature, low-humidity inert gas.

An embodiment of the present invention will be described below with reference to the drawings.

The drawing shows an example in which the combustion exhaust gas of a boiler is used as inert gas for the mill.The combustion air sent to the boiler (3) via the combustion air supply pipe (2) by the blower (I) has a concentration of 0□. The combustion exhaust gas becomes about 4 cm and is discharged from the inert gas pipe (4a).

The amount of exhaust gas, ie, the amount of inert gas, is adjusted by an air volume adjustment valve (5). The properties of the inert gas at the boiler outlet vary depending on the combustion conditions, the humidity of the combustion air, and the type of fuel, but are approximately 02a degrees 3 to 4%, temperature 200 to 500 degrees Celsius, humidity 80 to 160 gr water/INm' gas.

The inert gas whose air volume is adjusted is the inert gas pipe (4b)
is sent to the gas cooler, where the cooling medium inlet pipe (7
It is cooled to below 300C by the cooling water or cooling gas circulating between a) and the cooling medium outlet pipe (7b), and the humidity is below 40 gr water/INm'.

This low-temperature drying gas passes through an inert gas pipe C4C), is throttled by a valve (8), and is sent to a heater (9)K, after the mill exit.

is reheated to a temperature above the dew point in a mill (10
).

First, the raw coal supplied in a fixed amount from the coal feeder hopper (12) to the coal feeder (IIIK) is fed into the mill (10) K, where it is pulverized in an atmosphere of the above-mentioned inert gas to become pulverized coal of the desired particle size. This pulverized coal is carried by the high-temperature, low-humidity inert gas sent from the heater (9) to the mill (10) via the inert gas pipe (4d) to the pulverized coal pipe (14).
d) The pulverized coal is sent to Zyclo7α6), where it is centrifuged and those below the required particle size are sent to the pulverized coal hopper (■
5) and the particles below the required particle size are transferred to the pulverized coal pipe (14b).
) 4, the coal is collected by the bag filter α group, and the pulverized coal hopper (1!9 tc of falling coal and the exhaust pipe α9) separates it into 9 parts to be sent to the next process 8.

The dew point of the inert gas after the mill exit is monitored with a dew point meter (I7) installed at the outlet of the cyclone (16) or bag filter α8), and the temperature of the inert gas is monitored with an inert gas thermometer installed at the same position as above. has been done.

By the way, as mentioned above, it is necessary to maintain the temperature at or above the dew point after the mill exit.

If the temperature of the inert gas falls below the dew point, pulverized coal will adhere to the pulverized coal pipes (14a), (14b), cyclone Q6) and bag filter 08), causing trouble.

Since the present invention is configured as described above, the dew point temperature after the mill outlet is constantly monitored, and the heater is set to a temperature higher than t'L, that is, about 10°C higher than the dew point temperature. (
Control can be performed by adjusting the opening degree of valve (9) and valve (8).

Be careful, in order to keep the inert gas above the dew point temperature,
After the mill exit 1], the inert gas is heated to a high temperature (e.g. 100℃
), the pulverized coal may catch fire or explode, which is not desirable from a safety standpoint. The present invention has the above-mentioned structure, and since the moisture in the inert gas at the mill inlet is considerably removed by the gas cooler (6) and lowered, the dew point temperature after the mill outlet is lowered, resulting in 7 Even if the mill outlet temperature is maintained at a relatively low temperature (60°C to 80°C2), pulverized coal does not adhere to the pulverized coal pipes (4a), (14b'), etc., so it is safe. play.

[Brief explanation of drawings]

Figure Id is a flow diagram illustrating an embodiment of the present invention. ■...Blower, 2...Combustion air supply pipe, 3...Boiler, 4a, 4b, 4C, 4d-inert gas pipe, 5...Air volume adjustment valve, 6...Gas cooler, 7a...Cooling medium inlet pipe, 7b...Cooling medium outlet pipe, 8...Valve, 9...Heater,
10... Mil, 11... MF, +, 2 machines, 12... Coal feeding hopper, 13... Inert gas thermometer, 14a, z
b...Pulverized coal pipe, 15...Pulverized coal hopper, 16...
Zycro/, 17... Dew point meter, 18... Bag filter,
19...Exhaust pipe.

Claims (1)

[Claims] In a method for producing inert gas, in which pulverized coal is pulverized in a coal T-mill, the pulverized coal is fed while drying, and then separated and recovered, high-temperature, high-humidity inert gas is cooled and dehumidified in a gas cooler to produce low-temperature, low-humidity inert gas. A method for producing inert gas for a mill, which comprises heating the inert gas with a heater so that the temperature of the inert gas after the mill outlet is equal to or higher than the detected dew point temperature of the inert gas, and sending the inert gas to the mill as a high temperature and low humidity inert gas.