This paper analyzes the reasons why the conventional buoyancy level Liugong system can not measure the tributary syngas and cold cross pressure liquid level, and details the successful use of the interpolated capacitive high pressure liquid level transmitter for synthesizing the high pressure liquid level. Practical experience and its benefits. 2 Reasons The level detection in high pressure vessels such as ammonia separators and cold exchangers in the ammonia production of our plant, and the liquid level detection device designed and installed in the conventional way using a communication tube type (float level gauge, etc.) cannot work properly. The phenomenon, according to the survey, is widespread at small chemical fertilizer plants. The reason for this phenomenon is that high-pressure gas-liquid separators such as ammonia and cold cross are not simply empty-tube containers, and the working pressure is as high as 32 MPa, and all of them are equipped with separate internals with different types of channels, and these high-pressure containers The outer simplification adopts multi-layer coil welding, and it is not allowed to open the hole in the cylinder. Therefore, the gas-phase and liquid-phase reserved interfaces installed as liquid level detection instruments are all opened on the forged high-pressure vessel and the lower head, that is, the gas-phase interface is on the upper head and the liquid-phase interface is on the lower head. 4 Implementation Results Our factory has built-in capacitor-type high pressure liquid level transmitters for ammonia synthesis and cold liquid level monitoring and control systems that have been put into operation since September 2009 and have been in operation for more than two years. Practice has shown that the project has achieved significant results. , Produce significant benefits, according to statistics, directly create benefits 800,000 yuan. (2) The ammonia and cold liquid level measurement of this system is accurate, and automatic ammonia release or manual manual ammonia release under the condition of the detection of the niobium is realized, and the manual manual ammonia release under the liquid level-free display condition is eliminated. To achieve safe production. Dredging Excavator,Dredging Equipment,River Dredging Machinery,Small Dredging Equipment Binzhou Jinyi Equipment Co.,Ltd , http://www.jyexcavator.cn
1 The original status of the system more than ten years ago, according to the traditional general design and conventional selection, our factory had installed a liquid ammonia level measurement and control system for ammonia synthesis and cold delivery. The level gauge used the UTQ-1 1 3 pneumatic high pressure buoy liquid level adjustment transmitter of Shanghai Automation Instrument Factory No. 5, and the control valve adopted z MBs-32o KDg6c=0.1, together with the pneumatic adjustment recorder and the sub-wire board to compose the composition. Section ammonia, cold high pressure measurement and control system (Figure 1). In order to facilitate maintenance and repair, a total of 7 DglO high-pressure valves, 2 standard tees, 1 elbow, 15 pairs of high-pressure flanges, 48 ​​high-pressure bolts, 90 high-pressure nuts, and sm towel 24 are used for each system. tube. In order to extend the service life of the high-pressure control valve and ensure the adjustment effect, two high-pressure control valve series solutions are adopted. The entire system is cumbersome, the installation volume is large, the site is cluttered, and each system investment is also more than 1500 yuan (a few years ago price). However, after the installation of these two systems, due to the inaccurate detection of the liquid level, they have not been put into use normally. 
As we all know, after the high-pressure medium flows through the equipment, due to the influence of the equipment resistance, a pressure difference will occur at the equipment import and export. The pressure difference is related to the equipment structure, flow cross section, medium flow and other factors, and changes with the change of the medium flow. Taking the ammonia separator of our factory as an example, the medium enters the container and flows through the separation internals to perform gas-liquid separation. The ammonia content of liquid ammonia exists at the bottom of the product to be discharged, and the gas is drawn from the outlet at the upper end of the container to the next-stage device. . The ammonia and cold liquid level detection interfaces (liquid phase and gas phase) of our plant are located on both sides of the separation section. The pressure difference generated by the separation section also acts on the gas-liquid interface of the liquid level gauge. According to measurements, the pressure difference in the separation section can reach several meters to ten meters of water at full load. With the ammonia, cold cross equipment structure and the media inlet position and the flow direction in the separation section, there may be two situations: one is the pressure side of the pressure difference in the separation section acts on the liquid level above and the negative pressure side acts on At the gas level interface of the liquid level gauge, at this time, the gas phase and liquid phase of the liquid level gauge lead to the positive stack of the pressure difference between the actual liquid level in the container and the separation section. The measurement range of the general buoy level transmission instrument is only within 1 meter. Therefore, as long as the bottom of the container is slightly liquid, it will quickly fill the communication tube of the external level gauge (buoy) under the pressure differential, so that the level gauge Display full level. Unless the liquid level in the container is completely emptied, the external float level meter always displays full scale regardless of changes in the liquid level. In another case, the differential pressure of the internal part acts on the gas-phase interface of the gauge, the negative pressure acts on the liquid level above the container, and the differential pressure of the internal part overlaps with the magnitude of the liquid level. Due to the pressure difference of the internal parts, regardless of the change of the liquid level in the container, even if the liquid level is filled with the container or even with liquid, the level gauge will always show zero. Our factory's original ammonia, cold AC pneumatic float level measurement system is not allowed, still belongs to the former type.
3Improvement measures To achieve energy saving and consumption reduction as soon as possible, our factory is determined to reform the automatic control system for synthetic ammonia and cold liquid level detection. UYB-320C built-in capacitive high-pressure level transmitter adopting “Fertilizer Industry†and “Little Nitrogen Fertilizer†by the editorial department is directly inserted into the equipment from ammonia liquid and cold liquid phase liquid hole to detect its liquid level. The plasma dual-beam digital display (with upper and lower limit alarms) shows the change of the liquid level, and the upper and lower limit alarms of the liquid level and the valve position of the regulating valve are self-adjusted by a simple electronic regulator. Because the original pneumatic high-pressure control valve was never used after it was installed, it is planned to use it temporarily for the purpose of saving investment. Our factory uses minor repairs, less than half a day, two sets of liquid level meter all installed. After commissioning and driving, the liquid level detection part works normally and is put into operation to realize ammonia discharge operation under liquid level indication. After the automatic control system was debugged, it was found that the original pneumatic control valve jumped heavily inside the BS. Although the two valves installed in the cold cross series were all closed, their flow capacity was also selected to be very small, but the liquid level was still very difficult. To mention it, it is difficult to adapt the regulating valve to meet the need of automatic control of high pressure liquid level. Even so, the amount of running air has been significantly reduced compared with manual ammonia discharge, and the CH4 content in the circulating gas has also increased. Our factory quickly purchased two new special automatic ammonia discharge valves for replacement. They were used for automatic ammonia release in ammonia and cold transfer systems. The liquid level automatic control was quickly transferred to normal, and finally resolved me in a short time. The key to the production of this plant is to realize automatic control of synthetic ammonia and cold cross pressure level measurement. 
(1) After the high pressure liquid level detection automatic control system is put into use, the effect is significant (see table). The content of CH' in circulating gas is obviously increased. Our plant is heavy oil gasification, which has been increased from 4% to 6% before installation of the level gauge to 11% to 14%, effectively reducing the effective system of gas venting and leakage in the synthesis system. 
(3) The application of liquid level automatic control system has freed the operator from frequent manual adjustments, greatly reducing the labor intensity of the workers and stabilizing the operation. The catalyst temperature of the synthesis tower is stable and almost a straight line.
(4) The level gauge is extremely easy to install, and the structure is very light, with a total weight of less than kg, with a flange, 3 bolts, and 3 nuts. The liquid level measurement and control system works reliably and stably. Our plant has not been repaired since it was put into operation for 2 years.