SU1520343A1 - Method of measuring carbon monoxide in flue gases - Google Patents

Abstract

The invention relates to metallurgical production, specifically to control and regulation technical solutions related to thermal processes occurring in furnaces, and is intended to measure the consumption of carbon monoxide in the exhaust gases. The aim of the invention is to increase the efficiency and accuracy of measurement. To achieve this goal, according to the method, the amount of O ₂ necessary for complete burning out of CO in the air is introduced into the measuring section, the inlet and outlet temperatures T _in are measured. , T _out . the measuring section and compare these values, the flow rate and the temperature of the air supplied for the afterburning of CO are also measured, then the temperatures T _{I are} maintained equal. and T _out . the effect of CO consumption is determined by the effect on the actuator of the air supply valve and taking into account the specific heat capacity of air and the calorific value of carbon monoxide in air with air oxygen. 1 il.

Description

The invention relates to metallurgical production, more specifically, to technical solutions for control and regulation associated with thermal processes occurring in furnaces.

The aim of the invention is to increase the speed and accuracy.

The drawing shows a device that implements the proposed method.

The device comprises a furnace 1, a flue gas 2 exhaust gases from the furnace, a measuring section 3 of the flue, a sensor for exhaust gas temperature at the inlet of the measuring section 3, a sensor 5 for exhaust gas temperature at the outlet of measuring section 3, an actuator 6 for the valve 7 of the air supply pipeline, supply air temperature sensor 8, air flow sensor 9, unit 10 for calculating the flow rate of CO in the exhaust gases, air flow controller 11 and indicating device 12.

The device works as follows.

Signals from sensors 4 and 5 of the temperature Tj and Tgjix are input to the input of the controller 11 at the input and output of the measurement section 3. The output of the controller 11 maintains the equality of temperatures T in and T, and when T is exceeded,

off

over Tg he increased yu

with

four

Od

enters the air flow by opening the valve 7. The calculating unit 1b, to the inputs of which the signals of the sensors 8 are supplied,

5 and 9 air temperature T, gas temperature Tp, and flow rate (air, calculates the value of the flow rate Gj-j in WASTE gases and feeds it to the indicating device 12. The calculation is made according to the formula

P Cj (Tji,

COB

with

where, and C in are constant computations describing the specific calorific value of CO and the heat capacity of air, the values of which are specified in block 10, since the manual slack of any values presupposes the structure of the computation blocks. These parameters can also be set from the operator's console (not shown). The device implements a method for measuring the flow of CO in the waste gas coming from the furnace 1, which is based on the described thermal model of the CO burning process when air is supplied to the measurement section 3.

The model considers the process as a mechanical mixing of the gases leaving the furnace with the supplied air. At the same time, the flow rate (mass) of the mixture is equal to the sum of the flow rates of air and flue gases, the heat capacity of the mixture is equal to the sum of the heat power of the supplied air, waste gas and heat power released during their mixing, which is equal to the heat power of combustion of CO, and the specific heat the mixture is equal to the weighted average of the specific heats of air and flue gases.

Mathematically, the model is described by the following expressions:

C, Gr - ъ

G, t zlOjr-l.CjiGj. "G.

PC P. "- WP + P

With

de GO, Co, RO in

accordingly, the flow rate, specific capacity, heat capacity of the mixture of air and waste ha-55

3OBi

same parameters for air

5 0 5

0 5 0

five

0

five

G, C, P are the same parameters for waste gases.

As can be seen from the above description of the model, its simplification compared with the actual process consists in neglecting the deviation of the specific heat capacity resulting from the chemical reaction of the CO and O mixture from the weighted average (i.e., neglecting the chemical composition of the mixture). The accepted simplification is valid because the reaction involves only a relatively small part of the components and as a result of the reaction their specific heat capacity varies slightly. The energy released in the CO combustion reaction is significant and has a great influence on the state of the mixture, therefore, it is taken into account by the model.

The estimated estimate of the model error confirms the findings.

Only those that take part in the chemical reaction and cause the model to deviate from the actual process are separated from the composition of the gases. i

The error in determining the heat capacity of this component of the gases in the gas duct is found.

The specific temperature of CO is 0.25, QI is 0.22 kcal / deg “kg.

According to the chemical reaction

2CO-f- OT. 2CO + 135.2 kcal and molecular weights have that in response to 32 g of oxygen, 28 g of CO is obtained.

According to the assumption in the model, the specific heat capacity of the mechanical mixture of the corresponding amounts of CO and Oi is C 0, kcal / deg KG.

In a real process, carbon dioxide production has a heat capacity

coz OJS kcal / hail kg.

Error 20,

In order to simplify further evaluation, the errors are taken as the worst case when all the CO contained in the gases of the flue is formed as a result of burning the CO in the supplied air.

It is known that the content of C0 (reaches 20 of all gases of the flue, having an average heat capacity of 0.3 kcal / kg-deg.

51520

The source of the heat capacity of CO and gases in general and the percentage of CO in gases, it can be approximately accepted that the CO gas determines by 15% the heat capacity of the entire exhaust gas as a whole.

Then we can assume that the error of the adopted model is

- T55I

Estimation of the error shows that the model is quite suitable for practical use.

By the way the process of burning CO. The air supplied to the measuring section 3 occurs while maintaining the temperatures T at the outlet of the measuring section 3 equal to the temperature Tg at its entrance. From the point of view of the above model, it can be concluded that all the energy released due to the burning of CO spends on heating the incoming air to the temperature in the measuring section 3, since the temperature of the exhaust gases does not change. In addition, it can be concluded that all the CO from the exhaust gases is involved in combustion, since air (oxygen) is supplied with an excess, otherwise, if there is a lack of air (i.e., all its oxygen participates in the reaction with CO), the calculation shows that the released heat energy is sufficient to heat the air to a temperature of about. Consequently, in this case, the temperature n the output of the measuring section. Would be higher than the temperature at its inlet. Excess air is necessary to maintain the equality of temperatures Tg and Tsch, p, at the inlet and outlet of the measuring section 3.

Thus, knowing the initial and final temperature T, Tr (Tvud) of the supplied air, its flow rate C and heat capacity Cg, one can find out the heat capacity released in the combustion reaction of CO in the measuring section 3. But then, based on the chemical equation of this reaction, taking into account the fact that all CO from the exhaust lawn participates in it, it is easy to determine the CO flow of the exhaust gases, it is easy to determine the CO flow in the exhaust gases:

2CO 2COi + 135.2 kcal-.

five

0

five

0

five

0

with

6

&}

with

with

where - consumption (mass) C, rp / Cj

in Cg-C, (Tr - Tg), kcal / cv T |. (Tgj ,,) is the temperature at the outlet of the measuring section, degrees; the temperature of the supplied air, hail, is the specific heat value of CO, kcal / g; specific heat of air, kcal / g trad; air flow, g / s. Specific calorific value

Cso kcal / gr.

Finally, to determine C, have

T. CO

With “G“ With

with

 2.)

 6

Claims (1)

Thus, the method allows prompt and accurate determination of the CO content in the exhaust gases by simplifying the solution of the problem and the lack of technical means that control with an error (gas analyzers, extreme regulators), as well as improving operational performance. constructions of this designation by reducing their requirements for production in connection with the possibility of carrying out CO afterburning reactions at lower temperatures. Invention Formula A method for measuring carbon monoxide consumption in exhaust gases, including supplying the amount of oxygen required for complete carbon monoxide burnout into the measuring section, measuring the temperatures Tjjj and Tgj, | j of exhaust gases at the inlet and outlet of the measuring section and comparing Tj., . and (x a measurement of the flow rate Gj and the temperature Tg of the air supplied for the after-burning of carbon monoxide, characterized in that, in order to increase efficiency and accuracy, the equality temperatures T and Taikh by measuring the air supply for complete carbon burnout in carbon monoxide and taking into account the specific heat capacity of air and the calorific value of the reaction With carbon monoxide air, carbon monoxide consumption values are determined.