Low Pressure CO2 Fire Suppression System for Coal Fired Power Plant

1.Fire Extinguishing System General Description
   Its feature is that the liquid form of carbon dioxide extinguishing agent storages in the low-temperature vessel with insulation structure, making the temperature of carbon dioxide in storage tank maintain at -18 °C ~-20°C and the pressure at 2.07MPa of liquid form by refrigerating unit. When there is fire, it delivers the liquid carbondioxide to the fire scene by series of controlling and executing organizations to carry out automatic extinguishing. 
  2.Composition of Fire Extinguishing System
   Low-pressure carbon dioxide fire extinguishing system mainly consists of storage facilities, device controller, distributor gear, pipe network, nozzle, automatic detection system and automatic control system.
Storage facilities is the all equipments connecting the inlet of servicing valve, including storage vessel (storage tank), refrigerating unit, safety valve, the filling inlet of extinguish agent, liquid level transmitter and pressure transmitter;
Distribution system, pipe network, and nozzle is all equipments connecting the outlet of examination valve, including electromagnetic driving apparatus, total control valve, selector valve, signal feedback device, pipeline and accessories, nozzle etc.
Automatic control system refers to the electrical control parts such as fire extinguishing controller, terminal box, the lamp of discharging gas and emergency start/deadline box etc.
Device controller is the dedicated equipment controlled by storage device and refrigerator unit.
   This sample doesn't provide the introduction of automatic detection systems and other interlocking equipments. Please make reference to product samples or related information of fire detection equipment manufacturers for these parts.
3. Working principle diagram    
                         Fig.1 the working principle diagram of low-pressure carbon dioxide fire extinguishing system
4. Operation Principle and Working Procedure
     When a protection area firing, fire automatic detection system know the firing and transmit fire signal to the low-pressure fire extinguishing controller, after lapsing time 0 second to 30 second, the controller send out  driving instruction (when multi-zone, increasing the number of terminal boxes). The electromagnetic driving device of controlling the selector valve of the protection area and the electromagnetic driving device of controlling the total control valve are opened successively or simultaneously, corresponding selector valves and total control valves was opened. The extinguish agent in storage tank start to send out at the pre-set time through the system components such as total control valve, selector valve, pipe network, nozzle and then pre-set time is up, electromagnetic driving device controlling total control valves close automatically. After delaying enough time, the electromagnetic driving device of controlling selector valves close. Total control valves and selector valves automatically close one after another because of losing the effect of driving gas so that the system stop discharging extinguish agent. This procedure achieves the function of automatic fire fighting.
    When the automatic detection system breaks down or the people find firing before the system, the emergency start button installed on the door of protection area or on the controller control panel shall be pushed to actuate system and then manually achieve the function of fire fighting. When the fire control cabinet cannot provide the electromagnetic driving device with power supply of 24V, the mechanical measure can be adopted by switching the handle of electromagnetic driving device of control selector valve and total control valve to actuate the system so that achieving the function of mechanical emergency fire fighting.   
     Fig. 2 The working procedure of low-pressure carbon dioxide fire extinguishing system

5. Storage Device
  Storage device is pressure vessel of storing the liquid carbon dioxide fire extinguish agent. This storage device includes bladder, external protection layer, thermal insulation layer and cooling equipment. Bladder is manufactured by adopting the low-temperature resistant materials and the form of insulation layer is the polyurethane foam and its advantages are short manufacturing period, relatively low cost, good quality of insulation and little influence from environment. 
                                                              Storage device parameter table





Low-pressure carbon dioxide storage device controller of ZEZK type
1.General Description
      Low-pressure carbon dioxide storage device controller of ZEZK type, device controller for short as follow, is the product that our company develops according to the standard of GB1957-2013 'Low-pressure Carbon Dioxide Fire Extinguishing System and Components', and uses with the carbon dioxide storage device of our company. The controller is the product of integrating strong and weak electricity, adopting the touch screen LCD technical of PLC (Programmable Logic Controller) and HMI (Human Machine Interface). ZE is the code number of the product, and ZK is on behalf of Device Controller that can drive the refrigerator unit of 2.6kilowatt to 8kilowatt. A set of storage device is equipped with a set of device controller, which can control two sets of refrigerator units, and main refrigerator unit and standby refrigerator unit can alternately operate automatically. Direct-current power source has the full-automatic charging circuit of standby direct-current power source. Controller is used in indoors. Storage device equipment room shall be well ventilated, needing supply the power source of 380V, 50H and reliable protective grounding.
  The controller output the power source of DC24 to the pressure transmitters and liquid level transmitters. The pressure transmitter and the liquid level transmitter output the current signals of 4-20mA to the sampling port of PLC. Outputting is the process that PLC automatically controls the intermediate relay to lower the temperature in the low-pressure carbon dioxide storage device by the alternating current power supply provided through AC contactor to refrigerator unit so that remains the pressure in the storage device at the level of 1.9MPa~2.1MPa. Controller can manually operate the button to control the actuating and stopping of the refrigerator unit under the manual work
2.Low-pressure and High-pressure Alarming Functions
  Controller receives the pressure signal of 4-20mA coming from the storage device pressure transmitter. 4mA corresponds to 0MPa; 20mA corresponds to 4MPa. The high-pressure and low-pressure alarm sound and optical signal show the exact pressure value.
High-pressure alarm pressure: 2.2MPa±0.05MPa
Low-pressure alarm pressure: 1.8MPa±0.05MPa.
3.The Alarm Function of High Liquid Level and Low Liquid Level
Controller receives the liquid level signals of 4-20mA coming from storage device liquid level transmitter. 4mA corresponding to 0kMPa and 20mA corresponding to 20kPa can have the alarm sound and optional signal of high liquid level and low liquid level and show the exact value of liquid level.
4.The Function of Pressure Controlling of Storage Device 
  Controller has manual operating methods and automatic operating method.
When the power supply of alternating current is normal and PLC operates normally, the controller receives the signals coming from the storage device pressure transmitter; controlling the power supply circuit of refrigerator unit.