Control Model Research Of Regenerative Heating Furnace

Reheating furnace is a key segment between rolling and casting. It supplies slabs with specified heating quality to rolling line according to rolling rhythm and saves energy as much as possible.How to save energy and reduce pollutants becomes an important subject due to energy deficiency, increasing energy demand and strict discharge standard home and abroad. The appearance of regenerative reheating furnace meets the demand, which adopts a new waste heat recovery technology named high temperature air combustion. The new technology preheats the air or gas or both to raise the theoretic combustion temperature through storing enthalpy from high temperature waste gas.Compared with tradition reheating furnace, regenerative reheating furnace has its advantages, such as high technological temperature, recycling more energy from waste gas, less NOx pollutants of low oxygen combustion, high thermal efficiency; however it has some disadvantages such as preheat segment control problem, over-temperature of furnace entry segment which may cause the burning break of heat exchanger pipe and failure time. Waste out of regenerator may also become over-temperature and cause damage of reversing valve. Because reheating furnace is a nonlinear, multivariable and large inertia system, control become complicated. Control of regenerative reheating furnace is more complicated. Frequent actions of reversing valve not only cause flame width of regenerative reheating furnace hard to control in different load and discrete of furnace temperature regulate but also wear of reversing valve and short lifespan.The contents of this thesis are as follows: The first part is to build slab temperature differential model and find its solution in algorithm form for furnace temperature optimization. The thesis use Hook-Jeeve local algorithm method to find a set of local satisfactory solutions through taking heating quality and fuel integration as performance index while taking heating rate and temperature difference of adjacent segment as constraints. The second part is to build energy balance mathematic model of regenerative reheating model using segment energy equation based on new characteristics of regenerative furnace and theory of reheating furnace. Besides, particular models of preheat segment and furnace tail segment are derived to research on control segment and non-control segment in this part. The third part is to build regenerator process model using energy balance between micro-unit regenerator and gas according to classic thermal theory and heat transfer theory. Simulation of regenerator working process and optimization of exchange period and gas flow are both based on the model. The last part is to build model of yield and heating quality based on the research of contradiction of yield and heating quality through tacking temperatures and furnace segments as parameters while taking yield and heating quality as goals. The emphases of the thesis are building models of energy balance of regenerative reheating furnace and regenerator according to their mechanisms and do some control research simulation. The first purpose is to supply some basic understanding of mechanism about operation of regenerative reheating furnace, guide temperature setting, fuel supply, waste gas discharge and exchanging period. The second purpose is to find in what circumstances regenerative reheating furnace is energy saving and how to excavate the energy saving potential. The third purpose is how to avoid the discrete of furnace temperature regulate and over-temperature positive feedback in such a complicated industrial process system.