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Abstract

Ñîäåðæàíèå

INTRODUCTION

Determination of efficiency of use of fuel and energy resources (TER) in the production of thermal energy by burning fossil fuels (to consider the most common fuel for boilers – natural gas) - a very important task.

To assess the effectiveness of any technical system, a generalized physical indicator – the efficiency factor (efficiency) of the system is used, the physical meaning of which is the ratio of the value of the received useful work (energy) to the spent work (energy).

The coefficient of efficiency (efficiency) of the boiler unit is defined as the ratio of the useful heat that went to the production of steam (or hot water), to the available heat (the heat which has arrived in the boiler unit). In practice, not all the useful heat generated by the boiler, sent to consumers. Part of the heat is spent on their own needs. Depending on this, the efficiency of the unit is distinguished by the generated heat (Gross efficiency) and the efficiency of the unit for heat released to the consumer (net efficiency). Efficiency gross boiler unit characterizes the degree of its technical perfection and efficiency of the net commercial profitability.

Gross efficiency of boiler unit ηáð, %, can be determined by direct balance method or reverse balance method. Efficiency by direct balance equation it is used mainly in the preparation of statements for a single period (decade, month), and the efficiency of the inverse balance equation-in the test boiler unit. Determination of the efficiency of the reverse balance is much more accurate, since the error in the measurement of heat loss is less than when determination of fuel consumption, especially when burning solid fuel.

1 DESCRIPTION OF THE METHODS OF THERMAL CALCULATIONS

The method of determining the efficiency of a large number of boilers, this is due to the fact that some scientists suggest using generalized characteristics fuel or by direct measurements only. From methods of thermal calculations it is possible to allocate a method of the given characteristics of fuel, founded by S. Ya. Kornitsky and generalized method M. B. Ravich, methodology of heat engineering calculations according to the above characteristics fuel Y. V. Pekker.

2 THE CALCULATION OF THE EFFICIENCY OF THE BOILER DKVR-6,5/13

When analyzing the influence of the content of the natural gas efficiency of the boiler DKVR-6,5/13 in the base composition of the gas taken Yamburg natural gas deposits, the composition of which coincides with the composition of the gas regime map of the boiler.

The main document defining the order of operation of the boiler unit is the regime map which is made by the organization having on that the authority, after conducting regime-up testing. In accordance with the "rules of operation of thermal power plants" frequency carrying out such tests for gas boilers is 3 years.

According to the data, which are given in the regime map of the boiler, namely the gas pressure in front of the burners and the consumption of natural gas for the corresponding modes operation of the boiler, we find efficiency.

2.1 EFFICIENCY CALCULATION BY DIRECT METHOD

2.2 CALCULATION OF EFFICIENCY ACCORDING TO THE METHODS GIVEN CHARACTERISTICS OF PECKER

Drawing up the heat balance of the boiler is to establish equality between the amount of heat received in the unit, called the available heat Qðð , and the amount of useful heat used Q1 and heat loss Q2, Q3, Q4, Q5, Q6. On the basis of the heat balance calculated efficiency and the required flow rate of fuel.

The efficiency of the boiler (gross) in the opposite balance the formula:

(ηáð)=100-(q2+q3+q4+q5+q6), %

where q2 – losses of heat with leaving gases; q3 –heat loss in the boiler with chemical underburning; q4 – heat loss in the boiler from mechanical incompleteness of fuel combustion; q5 – the loss of heat from the external cooling; q6 – the loss of physical heat of slag.

Average heat loss dataq3, q4 given in the normative method of thermal calculation according to the formulas (1.19-1.20), toll heat's q2, q5, q6 determine the calculation, and the results will be summarized in table 2.4.

Table 2.4-Calculation of efficiency by the method of the given characteristics of the Pekker

Table 2.5-Efficiency based on the higher calorific value of natural gas (inverse balance method)

2.3 EFFICIENCY ON THE BASIS OF GROSS CALORIFIC VALUE OF NATURAL GAS (INVERSE BALANCE))

Evaluation of the efficiency of the boiler installation requires the determination of heat loss and efficiency. on the basis of higher heat of combustion Qðð natural gas (reverse balance method) by the formula

(ηáð)=100-q2â-q3â-q5â, %

Numerical value of the efficiency of the boiler plant gross (ηáð), heat loss of fuel with exhaust gases - q2â , loss of fuel heat due to chemical incompleteness of combustion - q3â, heat loss of fuel to the environment -q5â , you can define through their known values determined on the basis of the lower calorific value of natural gas Qíð.

3 PROCESSING OF RESULTS

When determining the actual efficiency of the boiler by the reverse method, we obtain a graph of the efficiency of the lower combustion heat shown in figure 3.1. In calculations by this method, the efficiency is more affected by the heat of combustion.

Figure 3.1 - Dependence of boiler efficiency determined by the inverse method of the heat of combustion.

When calculating the efficiency according to the methods given characteristics of Pechera on the efficiency of the impact of loss of heat in the boiler with the chemical incomplete combustion q3. Therefore, the dependences are constructed taking into account this factor in figure 3.2.

Figure 3.2-Dependence of boiler efficiency on losses with chemical underburning.

When calculating efficiency . on the basis of the higher heat of combustion of natural gas (the method of reverse balance) the result is affected by the heat loss of fuel exhaust gases and loss of fuel heat due to chemical incompleteness of combustion. This dependence is shown in figure 3.3.

Figure 3.3 – Dependence of boiler efficiency from the loss of chemical incomplete burning and leaving gases.

Calculating the efficiency of the boiler by different methods, the result is presented as a dependence of the boiler efficiency of the lower heat of combustion of natural gas in figure 3.4.

Figure 3.4-Dependence of boiler efficiency on losses.

CONCLUSION

We have calculated by different methods and got different results, this is the result of the fact that the error has not been canceled, and of course every scientist of the drafters of these methods have introduced something of their own new, something neglected, something rounded. Boiler unit gross efficiency (ηáð), %, can be determined by direct balance method or reverse balance method. The efficiency of the direct balance equation is used primarily in the preparation of reporting for a separate period (decade, month), and the efficiency of the inverse balance equation — when testing boiler units. Determination of the efficiency of the reverse balance is much more accurate, since the error in the measurement of heat loss is less than in the determination of fuel consumption.

Thus, the use of different methods of determining the efficiency of boilers allows in each case to take into account the influence of the main determining factors of the combustion process and determine emissions into the environment.

REFERENCES

  1. Thermal calculation of boilers (standard method). - St. Petersburg, 1998. - 259p.
  2. Ravich M. B. Simplified methodology of thermal engineering calculations. - Moscow: publishing house "Science", 1966. - 416 p.
  3. Graduated from J. L. Thermal calculations given the characteristics of the fuel. - Moscow: Energy, 1977. - 256 p.
  4. Thermal calculation of boilers (Standard method) [Text]. - Third edition, revised and supplemented.// Under the editorship of S. N. Movchan, A. A. Abryutina, G. M. Kagan, V. S. Nazarenko. – Saint Petersburg: RAO "UES of Russia", JSC VTI, JSC NPO CKTI, 1998. - 299 p.: ID.