1 compressor boost transformation
1.1 The process basis of compressor boosting reform Under the certain conditions of petroleum gas composition, only the condensation end temperature and pressure affect the yield of light hydrocarbons. From the condensing pressure, temperature and yield correlation diagram, it can be seen that the higher the condensation pressure, the higher the yield under the condition that the condensation end temperature is constant.
In the 7.5×104 Nm 3 /d light hydrocarbon recovery unit of Shengkou Oilfield Hekou Gas Station, except for the design pressure of the dryer is 1.0MPa, other process equipment (tower, separator, heat exchanger * Feng Dacheng, male, 1967 7 Yuesheng, engineer. Dongying City, 257200. etc.) The minimum design pressure is higher than 1.8MPa, which provides the basis for equipment flow for boosting. The rated working current of the original compressor motor is 353A. The normal working current before the boosting transformation is only 280A. The motor power is still relatively rich, which provides power guarantee for improving the working pressure (compressor exhaust pressure). This will reduce investment in equipment retrofits and increase efficiency.
1.2 Determination of key parameters of compressor transformation
1.2.1 The pressure at each level is determined by the condensation pressure of the hydrocarbon, the temperature and the yield <3>. Combined with the current status of the device, the working pressure (compressor discharge pressure) is initially set to 1.6 MPa (gauge pressure). In the case where the first inlet pressure is 0.05 MPa (table), considering the setting of the dryer between the stages, the pressure drop of 0.05 MPa is reserved, and the pressure-renovation of the 384L-28/0.5-8 type LPG compressor is basically the basic. According to the principle of balance, the first-order compression ratio is 3.47, the second-order compression ratio is 3.62, the first-stage exhaust pressure is 0.42 MPa (table), and the second-stage intake pressure is 0.37 MPa (table).
1.2.2 Compressor displacement
When the exhaust pressure and compression ratio of the two stages of the compressor increase, the volume coefficient v=1-(1 /m -1) of the original cylinder will increase with the compression ratio when the relative clearance and the variable index m are constant. And decrease. At the same time, the pressure coefficient P, the temperature coefficient T, and the leakage coefficient 1 all change a little, and the exhaust volume will decrease after the compressor is boosted. Considering that the increase of exhaust pressure will increase the piston force, the compressor power will also increase. In order to ensure that the motor power is not overloaded and the compressor body can still be used, the compressor displacement can be reduced by reducing the bore diameter. Reduced to 20Nm 3 /min, in order to achieve the technical transformation of the original structure as much as possible, while meeting the requirements of the compressed gas volume of light hydrocarbon plants.
1.3 Compressor heat and power calculation
Under the conditions of first and second stage exhaust pressure and displacement, the compressor after boosting reform can be calculated by thermal calculation: first stage exhaust temperature Td1=72.2°C, secondary exhaust temperature Td2=108.6°C above temperature Both meet the design requirements of the LPG compressor exhaust temperature ≯140 °C.
Determine the cylinder diameter of each stage, the first cylinder diameter D1=360mm, the secondary cylinder diameter D2=200mm, the piston rod diameter of the two-stage piston is d1=d2= 45mm. The original motor power is 160kW, and the motor power reserve ratio after boosting is 22.4%. The power reserve rate is in the range of 5% to 15%, so the original motor is available.
1.4 Compressor power and structural calculation
The maximum piston force of the boosted compressor is 43080N, and the maximum piston force before boosting is 38270N, an increase of 12.5%. As the cylinder diameters of all levels become smaller, the piston size decreases, and the inertia force and inertia moment of each stage change. . Through the calculation of the power of the boosted compressor and the design calculation of the crankshaft, connecting rod, piston and fuselage, it is determined that the original compressor only needs to replace one or two cylinder components, and the remaining components can be utilized, so that the cost of technical transformation is greatly increased. reduce. In the technical transformation, the traditional steel annular valve cast iron gas valve was changed to SFIII plastic mesh valve steel valve, which improved the life of the valve and reduced the maintenance workload.
2 compressor boosting effect
The technical parameters after the compressor transformation are shown in Table 2.
After three months of stable operation, the compressor pressure and temperature reached the boost design requirements. The maximum working current of the motor was 320A and the highest power was 124kW, which was close to and less than the designed shaft power. This indicates that the compressor transformation was successful. of.
After the compressor was upgraded, the secondary exhaust pressure was doubled, which increased the C+3 yield of the light hydrocarbon unit from 75% to 95%, and the output increased by 5 tons/day. According to the average market price of 2,000 yuan / ton of light hydrocarbons, after deducting new energy consumption and cost, the annual increase of 2.6 million yuan, the cost of transformation (350,000 yuan, including cylinder component replacement, process changes and process equipment inspection, etc.) only 45 All the days have been recovered and good economic benefits have been achieved.
In short, the 4L-28/0.5-8 LPG compressor can be upgraded into a 4L-20/0.5-16 LPG compressor, which is a low-pressure compressor transformation in the light hydrocarbon industry, improving product yield and reducing tons. Hydrocarbon costs provide an experience that can be referenced.
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