The compressor unit of PetroChina Urumqi Petrochemical Company's refinery (hereinafter referred to as China National Petroleum and Petrochemical Refinery) is composed of 3 Peter Brother's 4E3+BL, 2 open and 1 standby. The designed standard displacement of the compressor is (24 motor power is 2570kW. Because each machine can only meet the production needs of 70%, the compressor is normally opened, but in the actual production process, due to the compressor Using a three-to-one gas volume adjustment method, even if the process load reaches the maximum, 60% of the gas volume of one compressor is returned to the intake pipe through the regulating bypass, and these recirculated gases are compressed, which causes a very large Large energy waste; in addition, because the compressor unit does not have a step-by-step adjustment mechanism, the compressor cannot slowly increase the load, so it will inevitably impact the compressor, which also seriously affects the process stability and the compressor. Service life. In order to solve the above problems of the compressor, the hydrocracking unit of the PetroChina Uefin Petrochemical Refinery introduced the HydroCOM stepless gas volume regulation system to achieve better energy saving effect and smooth operation of the compressor.
1HydroCOM working principle and system composition 1.1 Working principle As shown in the figure, the compressor in the normal working cycle, the movement of the piston in one cylinder includes the following stages: the expansion process of the residual gas in the cylinder, the suction process of the compressor, When the suction volume reaches 100% of the cylinder volume, the gas begins to compress, and when the gas reaches the exhaust pressure, the exhaust process is performed. These four stages correspond to the curves of the middle, the ç¡·, and the square 1. However, if the compression of the gas is started at the end of the inhalation process, the intake valve remains open under the action of the external force, and the uncompressed gas in the cylinder is returned back through the intake duct, waiting for a certain point Cr ( That is, the exhaust volume required for the gas volume adjustment is removed. The gas valve is closed under the action of the pressure difference between the cylinder and the outside, and then the cylinder compresses the remaining gas, and the gas is discharged when the gas reaches the exhaust pressure, thereby achieving gas volume adjustment and energy saving. The purpose of the work. A significant advantage of this type of adjustment is that the compressor power consumption is proportional to the amount of exhaust, which effectively saves a lot of energy.
1.2 System Composition The HydroCOM stepless gas volume adjustment system mainly includes the following parts.
1.2.1 Compressor Interface Unit CIU CIU mainly undertakes the information exchange and signal conversion functions between HydroCOM system and DCS. It is an important medium for communicating HydroCOM system and user's original control system. 4, CIU basic: 1) DCS will be issued The 420 mA current signal is converted into a signal capable of controlling the opening and closing of the compressor valves at the compressor level; 2) the collected cylinder pressure, temperature, hydraulic station temperature and pressure, and various error alarm signals are converted and transmitted to the DCS system. 3) Parameter setting of the system;) Calculate the exact operating time of the actuator by accepting the flywheel position signal detected by the TDC pulse sensor.
The CIU itself does not emit or generate control signals. It acts as a signal conversion hub to convert the transmitted signals into signals that can be identified by the upper and lower links, turning the HydroCOM system into a high-speed regulation system that can accept standard current signals. The seamless connection with the original control system DCS makes the gas volume adjustment of the compressor more convenient.
1.2.2 Hydraulic Actuator HA HA is a general term for a series of direct acting components including unloading forks and solenoid valves. The hydraulic station provides the power required for the action. The CIU provides control signals and EPS power. The HA is mainly composed of the sealed chamber, the valve chamber and the electric chamber 3 shown.
The main function of the hydraulic station HU hydraulic station is to provide the actuator with the power required for the action. It pressurizes the hydraulic oil to the required pressure through all of its gear pumps (up to 200 Bar, the exact value is determined by the highest level of intake pressure regulated by the compressor). In order to ensure the stability of the oil pressure, the fuel tank of the actuator HA and the flywheel of the oil returning machine are positioned next to the flywheel of the oil returning machine to detect the real-time position of the piston in the compressor cylinder by detecting the signal transmitted through the hole on the flywheel or the bolt installed. After the conversion process of the compressor intermediate unit CIU, the comparison with the control signal values ​​transmitted from the control system is performed, and then the control signal is transmitted back to the actuator through the field bus to control the accurate opening and closing time of the intake valve. The schematic diagram of the installation location of the TDC is as shown.
1.2.5 server unit HSS computer, its main function is to set the specific parameters of the stepless gas volume adjustment system, so that the adjustment system matches the actual working condition of the compressor, and also undertakes the debugging work of the system and the fault diagnosis when the fault occurs. Features.
2.1 The basic control scheme adopts the following control scheme (see): 1) Equipped with HOERBIGER's HydroCOM stepless gas volume adjustment system on the K101A/B compressor to achieve 30% 100% continuous gas volume adjustment; 2) Unit bypass valve The control variable is the main control variable of the HydroCOM system; 3) the specific control logic diagram is as shown, the control logic diagram should be configured in the DCS, the compressor motor running state and the gas station motor running status signal are from the electrical MCC, interlocking After the motor signal of the hydraulic station is triggered, the HydroCOM system is cut off, and the gas volume adjustment of the compressor is completed by the bypass valve.
2.1.1 General Control Principles The overall control principle of the system is a combination of regulator output high selection control and split control.
The output of the 1402 and the reactor inlet pressure regulator PIC-1501 is compared, and the output signal having a large output signal value is selected as the output signal of the high-selector, that is, the bridge of the high-selector LSS is directed to the side with the larger output value, PIC1402 The control mode with the PIC1501 remains unchanged, and the output of the LSS is the valve position opening. The output value of PIC1402 and PIC1501 becomes the valve close signal after passing through the high-selector. For example, if the output of PIC1402 is 30%, it will be converted to 70% of the valve after LSS, and the actual opening of the valve of the three-in-one field is 30. %, HydroCOM and bypass regulation accept signals that are both valve closed. After LSS, HydroCOM and bypass control valves are controlled by split-range control. When HydroCOM is in automatic mode, HydroCOM will keep the compressor at 20% when the output of the high-selector is in the range of 0%20%. The load is operated, and the bypass valve corresponds to a 0% 100% degree. When the output of the high-selector is 20% 100%, the output of HydroCOM is the output value of the high-selector, and the closing degree of the bypass valve is 100%, that is, it remains closed.
For the control of the secondary and tertiary compression, the ratio is (+ 2.1.2 Interlocking logic indicates that the 101A main motor runs 20S, the HydroCOM own petrol motor runs and the manual CIU are simultaneously satisfied). Under the circumstance, HydrosCOM's CIU is allowed to be used, that is, it is activated (ena-bled).
2) After any of the following four conditions are met, the 3S interlock will be delayed to stop HydroCOM's own station, and Hydo-COM will forcibly output 100% load, and the unit will be running at full load.
The oil pressure is low (oil pressure <7.0MPa). When the interlock bypass is clicked, all interlock conditions will be cut off.
2.2 The energy-saving effect of HydroCOM system has been applied in the world by more than 300 sets. It has been widely used in China. From the perspective of data and practical application, the system does have a very low failure rate and very High maintainability. According to the compressor data letter of the PetroChina Uefin Petrochemical Refinery, the power / kW / kW power / 10,000 yuan interest rate table, the initial evaluation of the energy-saving effect of the machine after the installation of the HydroCOM system. The motor power of the K-101A/B/C compressor is 2600 kW, and the indicated power is calculated according to the shaft power of 0.85: the saved compressor indicating power = the compressor indicating power X (1 - compressor load) annual electricity saving = saving The compressor indicates the power X through estimation. The energy-saving effect of the machine after installing the HydroCOM system under different loads is shown in Table 1. The change of the compressor indicating the work with the load is as shown.
Table 1 Indicates the work of the compressor under different loads and the energy saved by the compressor load /%.824 3 Problems and analysis in the application process of the infinite gas volume adjustment system 3.1 Problems arising during the system commissioning process During the application process The K301A stepless gas volume regulation system has found leaks in the sealing chambers of the three-stage north and south actuators. During the dismantling, it was found that the packings in the three sealing rings of the sealed chamber were damaged to varying degrees, and the closer to the root, the more serious the damage (see).
Three-stage north and south sides of the actuator sealing room damage situation Three-level north and south side actuators to replace the new material of different materials, the south side of the packing using the original material filler (VITON fluoro rubber), but the filler at the thread locking ring is defective. The north side packing uses a set of packing materials of different materials (SIMRIZ perfluoroelastomer). SIM-RIZ perfluoroelastomers are much more expensive than VITON fluoroelastomers and are typically used in demanding applications where high temperatures and corrosion resistance are required. After that, the filler of the south side actuator was leaked again. The dismantling condition was similar to that shown, and then a new set of filler was replaced. The material was VITON fluororubber. After that, the third side of the actuator on the north side was leaked. The disassembly inspection found that the filler damage was the most serious in the previous damages. The fillers 1 and 2 were completely damaged (see 0), and the leakage gas was not discharged in the flare gas outlet. The room vents at the scene.
0 third-level north side actuator sealing chamber damage situation 3.2 problem analysis 1) bad working conditions, such as process gas containing corrosive medium, mechanical impurities, or three-stage cylinder pressure is high, reaching 95bar. But K301A only uses hydrogen production equipment, hydrogen The purity reaches 99.99%, contains only traces of hydrogen chloride gas, and does not contain mechanical impurities (see Table 2 for specific process media content analysis), which will not affect the sealing. The north side packing used a packing material of different materials (SIMRIZ perfluoroelastomer). The pressure of the device is up to 1000 bar, but no similar damage has occurred so far, and the K301A is damaged only after 40 days. Therefore, it should be that the packing component cannot adapt to the high pressure working condition.
Table 2 Analysis of media content of K301A process 2) Installation and fitting problems, from the lighter wear of the top seal, it is suspected that the radial force or alignment is not good when the unloading bar reciprocates up and down, which accelerates the packing. Wear and tear.
The actuator installation diagram is shown in Figure 1. From the three inspections, there are 4 fixed coupling screws between the sealing chamber and the bonnet (see 1). The disassembly tool is a special torque wrench provided by the manufacturer. The force of disassembly and assembly is 86Nm, which proves the sealing chamber and valve. The cover is not loose; b. After field measurement, the unloading rod has a diameter of 12 mm and the ovality is normal. From the feedback information of other devices using similar equipment, most of them are worn at the same time after the use of the unloading rod and the packing. The surface of the K301A three-stage unloading rod is visually clean; d. The bonnet and the valve seat are connected with the screw. (See 1), the bonnet is in contact with the valve seat, there is no loose offset, this item has no data to explain; e. The bonnet and actuator manufacturing defects cause installation and fitting problems, this inspection is difficult, it takes time and the manufacturer provides data support.
4 Conclusion This paper analyzes the practical application of HydroCOM stepless gas volume regulation system on reciprocating compressors, and draws the following conclusions.
1) The indicated power consumed by the compressor is basically proportional to the displacement. Under the control of HydroCOM, the compressor only compresses about 80% of the process demand, which can save about 20% of the indicated work compared with the previous bypass gas volume adjustment mode.
2) The HydroCOM adjustment system is used to make the pressure fluctuations in the process of starting, switching and stopping the compressor more stable, the parameters are more stable, and the control of the compressor is more reasonable. During the use of the system, attention should be paid to the influence of the compressor process conditions and the installation fit on the seal chamber to avoid the failure or wear of the filler caused by poor working conditions or improper installation, resulting in unnecessary downtime maintenance.
4) System maintenance generally only needs to replace the sealing packing of the HA, the gasket or the filter core of the oil station, etc., so the maintenance cost of the system is very low.
In summary, the HydroCOM system's gas volume adjustment function for the compressor unit of the hydrocracking plant basically meets the expected goals, achieves the expected energy saving and regulation effects, and has good maintainability.
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