Study On An Optimal Energy-saving Control Method In Main Pipe With Several Boilers Water-feeding System

More than half of the accidents of coal-fired power plants are caused by the boiler system in the case of factory which rely on the steam generated by the boiler, therefore, ensure the safe operation of the boiler is very important. And most of the accidents in the boiler system is due to failure of drum level selection and control, the low steam drum level will cause the phenomenon such as dry pot, which will make an explosion seriously. High drum water level leads full of water in boiler, and vapor carries liquid, which affects the separation of water and steam. So select center level as the control target, at this time the boiler neither full of water nor lack of water, and the evaporation area is the largest if the drum level in the mid-line’s location, and it can save the energy. For multiple boilers system, the mutual coupling of boiler drum level control makes the control system very complicated, so this paper adopts three impulses control system for boiler liquid level control.Under the condition of the safe operation of the multiple boilers system, we can improve the economy efficient as far as possible. And the boiler water-feeding pump is an important equipment in the water-feeding system, the consumption of energy accounts for about 30% of the factory, so the space of energy saving is very large. In fact, the valve throttling losses is to be blamed mainly by the motor which is matched with water-feeding pump. This paper bases on the essence of energy-saving, and puts forward the biggest water-feeding valve opening optimal energy-saving cascade control method, then explains it. This method has the advantages of increasing the opening of the water-feeding regulator to reduce the energy consumption of water-feeding pump and doing not need to give the relationship between main pipe pressure and the steam flow rate. When the boiler’s steam flow is given, adjust the parameters of the largest water-feeding valve opening controller by genetic algorithm, then the controller calculates deviation and deviation change rate of the water-feeding regulator opening to get the main pipe pressure setting. The main pipe pressure can affect the largest water-feeding valve opening in the three impulse steam drum level control system of several boilers, and make the largest water-feeding valve opening in the three impulse steam drum level control system of several boilers reach the largest given opening so that the several boilers’ system works on the best energy-saving state. In order to enhance the anti-interference ability of main pipe pressure and make main pipe pressure quickly achieve the stable value, this paper introduces the main pipe pressure inner loop cascade control to get a better control effect.The main idea is to find out the variable speed water-feeding pump’s speed ratio and all the water-feeding pumps’ start-stop with minimum energy consumption when the pressure of the main pipe is constant. This paper uses the square of the difference between the water-feeding required and the actual water-feeding as the objective function, and takes water-feeding pump safe and efficient work as the constraint conditions. This paper employs the genetic algorithm to solve it to achieve the variable speed water-feeding pump’s optimal speed ratio and all the water-feeding pumps’ start-stop in sure of maximum valve opening, which shows that the variable speed water-feeding pump’s speed is slower under the efficient operation condition of the water-feeding pump, and the main pipe pressure is reduced greatly, at the same time the energy saving effect is remarkable.