Development of a new simulation model of utility b

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Development of a new simulation model for utility boiler furnace

classification number: tk224 document identification code: a

article number: (2000) the development of the simulation model

of a new power plant boiler furnacewei tie Zheng

(North China Electric University, Baoding 0711, what are the advantages of rubber fatigue testing machine 003, China) ABSTRACT:During the course of developing the emulator train for the boiler unit of power plant, the l of the boiler furnace is one of the models that are most important, most involved, and most difficult to debug. Mainly according to The thermo-dynamical calculation standard method of the boiler unit, and at the same time doing some modification refering to some literatures, the author developed a new zero dimension dynamic emulation model of power plant boiler furnace. This model can be commonly used, and has well debugging capability. It has high precision, and can work steadily. Being applied in the emulator train for several years, it obtained good results.

KEYWORDS:simulation; model; Emulatortrain ▲ 1 Introduction in the development process of boiler unit simulation training machine in thermal power station, the boiler furnace simulation mathematical model is one of the most important, complex and difficult to debug models. Originally, some furnace simulation mathematical models came from some relatively simple empirical formulas, and some models came from the simplification of the numerical calculation results of a certain (or some) furnace steady-state three-dimensional heat transfer process. Therefore, there are some problems in the accuracy, versatility and convenience of debugging of the models. In this paper, a new zero dimensional dynamic Rockwell hardness experimental schematic simulation model of utility boiler furnace is developed based on the method introduced in the "standard method for thermal calculation of boiler units" issued by the Soviet Union in 1973, and some amendments are made with reference to some documents. It has good versatility, simple debugging, high simulation accuracy and stable operation. After several years of application in the simulation training machine, its use effect is good. 2. The simulation of the substances accumulated in the furnace and the substances at the inlet and outlet regards the furnace as the volume of a lumped parameter. When the boiler is cold, air composed of oxygen, nitrogen and steam is accumulated inside, and its pressure is the ambient pressure. After the boiler is ignited, the carbon dioxide, sulfur dioxide, steam and ash in solid state produced by fuel combustion are increased. Under special circumstances, such as when the furnace temperature is too low, pulverized coal cannot be burned at all, or have you ever known about its loading? Well, if there is no excess oxygen in the furnace but continues to feed excess pulverized coal into the furnace (assuming that there will be pulverized coal in the furnace that has no chemical reaction at all)

it is assumed that the fuel oil fed from the burner can burn in the presence of oxygen (considering the mechanical incomplete combustion loss) without extinguishing the fire. The pulverized coal Fed can burn stably when it meets certain conditions, otherwise it will produce fire extinguishing and deflagration. The conditions are as follows

(1) under the condition of normal air supply, the boiler does not extinguish the fire (if one of the following conditions is met)

① fuel oil is used to support combustion

② the amount of pulverized coal burned reaches a relatively high value

③ the furnace temperature reaches a relatively high value T1

(2) the following conditions must be met at the same time to produce deflagration

① the temperature in the furnace reaches a medium high value T2

② there is excess oxygen in the furnace

③ the concentration of pulverized coal accumulated in the furnace is within a combustible range

when the furnace deflagration conditions are met and there is sufficient oxygen, all pulverized coal accumulated in the furnace deflagration (combustion within a calculation interval); If the oxygen in the furnace is insufficient to supply all the accumulated pulverized coal for deflagration, a certain amount of pulverized coal will be deflagration according to the amount of oxygen. When the fuel ignition conditions are met, the fuel entering the furnace will immediately react with the incoming hot air and the excess oxygen in the original furnace. The combustion products produced are evenly mixed with the flue gas accumulated in the furnace. The average flue gas composition in the furnace is the composition of the flue gas discharged from the furnace. After one calculation, the number of moles of various components of the flue gas accumulated in the furnace is memorized for the next calculation. 3 Simulation of furnace pressure when the number of moles of various flue gas components in the furnace and the flue gas temperature in the furnace are known, the current furnace pressure is calculated by using the state equation of ideal gas [2] or by using the recursive formula of the state equation of ideal gas. The recurrence formula of the equation of state of ideal gas is as follows (1), where p is the furnace pressure, MPa; T is the flue gas temperature in the furnace, K; R is the gas constant; M is the total number of moles of various gases in the furnace; V is the furnace volume, m3; Footmark 1 and footmark 2 represent the values of time 1 and time 2 respectively; Δ M and Δ T is the increment of this variable in the calculation time step. 4 Simulation of heat transfer in the furnace the simulation of heat transfer in the furnace is the most important part of the furnace simulation model. It is divided into two parts according to the working state: the heat exchange between the flame and the water wall when there is fuel burning in the furnace; There is no heat exchange between the hot flue gas accumulated during fuel combustion in the furnace and the water-cooled wall. The following describes the simulation in two cases

4.1 simulation of heat exchange between flame and water wall when there is fuel burning in the furnace

firstly, calculate the flue gas temperature at the outlet of the furnace; Then, according to the flue gas temperature at the furnace outlet and the flue gas composition at the furnace outlet, the total enthalpy of flue gas output from the furnace outlet in a calculation time interval is calculated; At the same time, calculate the total heat brought into the furnace by the fuel and the thermal state acceptance response countermeasure air in a calculation time interval; Then, according to the ash and dirt wall temperature of the water wall

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