Constant pressure method in biomass boiler heating system in heating system: In high-temperature hot water supply system, because the water temperature is higher than the saturation temperature of water under normal pressure, the pressure in the system should be higher than the saturation pressure of the corresponding water supply temperature. In this way, hot water vaporization and water shock can be avoided. Water is a non-condensable fluid. Once leaked, the pressure will drop. On the contrary, water heating will shrink the volume. If the pressure cannot be stabilized, the equipment in the heating system will be destroyed. Therefore, in order to avoid decompression vaporization and contraction and pressure increase, the high-temperature hot water system must stabilize the pressure in the system, which is constant pressure. There are several ways of constant pressure for hot water heating systems:
1) Using elevated water tank constant pressure method
The constant pressure point in this way is set at the inlet of the hot water circulation pump or the main trunk line of the return water. The installation is only an overhead water tank. Its simple structure, stable and reliable work can stabilize the system pressure, and it can meet the overflow and Replenishment request. In such a system, the height of the water tank device must satisfy the request to not vaporize a very high point in the system. Therefore, the device position is high. This constant pressure method is suitable for low-temperature water heating systems with a small heating range.
2) Constant pressure method using make-up water pump
When the pressure of the heating system is high, the use of an elevated water tank cannot guarantee the pressure required by the system. At this time, a constant pressure method of the make-up water pump should be used. This constant pressure method is widely used in the heating system of Soviet hot water boilers. The make-up water pump constant pressure has two modes: continuous water supply and constant pressure and intermittent water supply and constant pressure. The installation of the biomass boiler in constant pressure mode consists of a make-up water tank, a make-up water pump, a pressure conditioner, and the like. When the system is operating normally, the pressure conditioner adjusts the make-up water pump to make up water continuously and make it conform to the leakage of the system, so as to maintain the stability of the system pressure. When the circulating water pump is stopped, the shut-off valve in front of the pressure conditioner can be closed. The make-up pump continues to replenish water to maintain the static pressure required by the system. This constant pressure method does not need to shrink the water tank, so the equipment cost is low. In addition, the make-up water pump replenishes and sets the pressure, the power of the pump is not large, and the operating cost is small. Therefore, this method is quite common in hot water heating systems in China. The big drawback of this constant pressure method is that if the system suddenly loses power, the make-up water pump will lose its constant pressure effect.
In order to avoid water shortage and vaporization of the boiler at this time, a pressure water assisted installation is adopted in the system. When the circulating water pump is running, the circulating water will not be poured into the pressure rising system due to the water assisted installation. When the power supply is stopped and the circulating water pump and make-up water pump are stopped, the pressure water supply system is immediately put into operation, the check valve is automatically opened, and the pressure water will flow through the hot water boiler and be discharged from the gas collection tank, thereby preventing the furnace chamber. The excess heat caused the water to evaporate. At the same time, the main valve of the supply and return water pipes should be closed to isolate the heat source from the heat network. The continuous water supply constant pressure of the biomass boiler make-up water pump is controlled by the electric contact pressure gauge. The inlet pressure of the circulating water pump can be maintained within a certain range. When the pressure is lower than this range, the electric contact pressure gauge operates and the make-up water pump motor circuit is connected. When the make-up water pump runs, make-up water, and the inlet pressure of the hot water circulation pump rises and exceeds a certain range, the pressure gauge of the hot water boiler is to cut off the power supply to the make-up water pump and stop the make-up water pump. In this reciprocating action, the make-up water pump continuously replenishes water and maintains the system pressure within a certain range. In this way, the constant pressure of the system is more energy-efficient than continuous water replenishment due to continuous water replenishment, but its conditioning and constant-pressure quality are worse than continuous water replenishment. There are also shortcomings such as large pressure fluctuations, frequent contact with the pressure gauge and easy damage.