SU887910A1 - Method of automatic control of raw mixture calcinging process in rotary furnace - Google Patents

Description

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The invention relates to the field of automatic control of heat treatment processes of bulk technological materials, in particular, automation of the burning process of various raw materials, such as apatite, clinker, expanded clay, in rotary kilns, and can be used in the chemical, metallurgical and cement industries.

A known method of automatic control is based on the change in the fuel supply according to the temperature of the material in the furnace and the amount of entrained dust in the dust collecting device 1.

However, this method of automatic regulation is based on the use of signals related to the qualitative characteristics of the finished product by empirical dependencies, and does not take into account some of the effects on changes in the mesh mode of the rotary kiln on the quality of the finished product.

Another method is known to automatically control the process of burning the raw mix in a rotary kiln, including measuring the gas-fuel supply and changing the gas-fuel flow rate, measuring the raw mix supply and changing the raw mixture flow rate, stabilizing the gas-fuel pressure and stabilizing the vacuum at the cold end of the furnace 2. A device that implements this method has a circuit for automatic stabilization of the flow rate of the raw mix, a circuit for stabilizing the vacuum in the cold end of the furnace according to the flue gas temperature and content oxygen in the flue gases, the gas pressure stabilization circuit supplied to the nozzle. The main control loop is to supply the fuel in the calcination zone from the thermoelectric thermometer installed in the self-cleaning pocket, in the sintering zone from the radiation pyrometer, oxygen content in exhaust gases and fuel consumption. .

In this automatic control scheme, the main measuring transducers are a thermoelectric thermometer installed in a self-cleaning 3 Pocket and a radiation pyrometer. As the operating experience of these devices shows, on. rotary kilns, their readings are often not unambiguously related to the temperature of the material, since a thermoelectric thermometer cover sometimes sticks to a layer of material, forming an additional heat insulating casing, and the radiation sensor installed in the hot furnace head is greatly affected the dustiness of the torch and the aggressiveness (in the production of mineral fertilizers) of the environment, in addition, the regulation of the negative impact of this $ scheme is aimed at changing fuel consumption, which leads to a change in thermal go mode of the entire unit. The purpose of the invention is to improve the quality of regulation of the firing process. This is achieved in that in the method of automatic control of the roasting process of the raw mix in a rotary kiln, which includes measuring the supply of gas-yielding and changing the flow rate of the gas-fuel, measuring the supply of the raw mix and changing the flow rate of the raw mix, stabilizing the vacuum at the cold end furnaces, additionally measure the flue gas temperature, the oxygen content in the first gases leaving, the heat flux density and are calculated on the basis of the heat balance equation from the measured flow rates raw material mixture, gas leaving temperature and heat flux density, the required flow rate of the raw mix, whereby the raw mix flow rate is varied by deviating the required raw mix flow rate from its current value, and the fuel gas flow rate is changed depending on the flow rate fuel gas, taking into account the measured vacuum in the cold end of the furnace and the oxygen content in the exhaust gases. The essence of the method lies in the fact that the change in the feed of the raw material mixture is carried out according to the results of comparing the current value of the raw material consumption with the required value of the raw material consumption obtained by calculating the simplified heat balance of the furnace: Qfl-GLH-n-n-Ca-t2-Ca ( l-cCLo) to-.о where GB is the consumption of gas-toshshva; QH - working heat of gas-fuel combustion; Gm - raw material consumption; ik is the required final enthalpy of the goth product; JQ is the initial enthalpy of the raw mix; Qn is the density of heat losses by the pet's body to the environment; RP - the area of the outer surface of the furnace body; t2 is the temperature of flue gases; heat capacity of flue gases; Of - excess air ratio; LO is the theoretically necessary amount of air for complete combustion of 1 m of gas-fuel. The drawing shows the implementation of the proposed method. The gas-blowing 2 and raw 3 mixtures are supplied to the rotary kiln 1, and gases 4 are released from it. The pressure of the gas-jaw in front of the regulator 5 is stabilized by means of a direct-action regulator, which includes a gas pressure measuring transducer 6, a regulating unit 7 with the actuator and the regulator 8. The vacuum in the cold end of the furnace is maintained at the level set by the regulator 9, which receives the signal from the dilution measuring transmitter 10 and acts as a Dymo guide apparatus The heat load of the furnace is maintained at the level set by the regulator 12, which receives the main signal from the measuring transducer 13 of the gas flow and the correction signals from the measuring converters 14 and 10, respectively, of the oxygen content in the exhaust gases and the vacuum in the cold end of the furnace. The flow rate 15 of the raw material mixture is maintained in accordance with the heat balance of the furnace with the help of the regulator 16. Signals from the transducer 13 of the gas flow multiplied by a constant factor 17, a fair QH, from the transducer 18 of the flue gas temperature t, multiplied in block 19, at a value of 13 the consumption of gaseous fuel G and by a constant factor of € 2 (1 + aLo) from the measuring transducer 15 of the raw material consumption, the mixture Gm from the functional unit 20 that performs the operation of the determinant. nor the average heat flux as the product of the half-sum of signals from the converters 21 and 22 of the heat flux density, and a constant coefficient R c, equal to the area of the outer surface of the furnace. The regulator 16 acts on the regulator 23 of the feed mixture. Using the method of automatic control of the roasting of the raw meal through a rotary kiln provides, in comparison with existing methods, the following advantages:

Claims (1)

Claim A method for automatically controlling the process of burning the raw material mixture in a rotary kiln, including measuring the supply of gas fuel and changing the flow rate of gas-fuel, measuring the flow of the raw mixture and changing the flow rate of the raw mix, stabilizing the pressure of the gas-fuel and stabilizing the cutter at the cold end of the furnace, characterized in that, in order to improve the quality of regulation, the temperature of the flue gases, the oxygen content in the flue gases, the heat flux density are additionally measured and calculated on the basis of the equation the heat balance according to the measured gas and raw material flow rates, the temperature of the exhaust gases and the density of the heat 1E flow, the required flow rate of the raw material mixture, and the change in the flow rate of the raw material mixture is carried out by deviating the required value of the flow rate of the raw material mixture from its current value, and the change in gas consumption IS fuel is carried out depending from gas-fuel consumption, taking into account the measured vacuum in the cold end of the furnace and the oxygen content in the exhaust gases.