1 In recent years, with the continuous development of small nitrogen fertilizer plants, the scale has been continuously expanded. This type of machine has been gradually replaced by other models and abandoned. How to transform and utilize this batch of old machines that will be eliminated soon? It is undoubtedly an important way to tap the potential of small nitrogen fertilizers, and to save energy and increase efficiency.

Based on several successful reforms of the machine, this paper studies and discusses how to use the L3 3- 17/320 nitrogen-hydrogen compressor to tap the potential.

2 L3 3- 17/ 320 nitrogen hydrogen compressor parameters

For the convenience of explanation, the relevant parameters and structure diagram of the L3 3- 17/320 compressor are given.

3 implementation of the principle of transformation

Modification shall be carried out in accordance with the principle of maximally utilizing the original L3 3- 17/320 compressor transmission components, motors, fuselage, cylinders, pistons, etc., in order to minimize the cost of retrofitting.

The original machine is equipped with TDK320-12 synchronous motor, its power is 320kW, the speed is 500r/min, and the investment cost is almost half of the original unit. Therefore, it is meaningful to make full use of the motor after the transformation. That is to say, the shaft power of the modified machine should not be too large (the motor can not be dragged) or too small ((large horse-drawn car), the running cost is too high), about 270kW is appropriate. Therefore, the following thermal and dynamic calculations are based on the motor's speed of 500r/min.

In the process of implementing the transformation, the cylinder diameter of each stage of the modified machine should be as close as possible to the cylinder diameter of the relevant stage of the original machine, so as to ensure that the working parts (cylinder, piston, etc.) of the original machine are not greatly modified. Make full use of it under the premise.

In determining the number of stages of the modified machine and the suction and exhaust pressures of the various stages, it should be considered that the resulting gas force should meet the strength requirements of the working and transmission parts to ensure safe operation of the machine. Although the nominal piston force of the original machine is 33000N, each component has a large strength margin, and the maximum piston force of the modified machine column can still meet the requirements when the maximum piston force is less than 40,000N.

In addition to meeting various thermal and strength indicators, the transformation process should also have good dynamic performance to ensure the smoothness of the machine after the transformation.

4 Research and discussion on the transformation plan

According to the above-mentioned transformation principle, it is quite difficult to modify the maximum exhaust pressure (ie, 32 MPa) of the original machine. Therefore, in the research and discussion of the following modification plan, the original machine will not be considered. Class cylinders, and retain the original machine's fuselage and motor layout unchanged, only propose some modifications to the first five cylinders.

Option 1: The original machine is transformed into a single-stage compressor, that is, the cylinders on the fuselage are removed, and the cylinders of the four original machines are respectively installed in the original column of the original machine, - flat-column, -%-parallel and - The corresponding position of the flat-column, thus transforming it into a single-stage four-cylinder double-acting double-L four-row type compressor, the structure of which is shown in the figure 1 column.

Option 2: The original machine is transformed into a secondary compressor, and the transformation plan is similar to the solution 1. The difference is that the original machine-flat-column cylinder is changed to the - flat-column cylinder and installed in the corresponding four-row cylinder of the original machine. Location. The balance chamber in the modified-flat-column cylinder is vented to atmospheric pressure regardless of the stage suction pressure. The structure diagram is shown in Table 2, No. 2 column.

Option 3: The original machine is transformed into a secondary compressor. The transformation plan is similar to the schemes 1 and 2. The difference is that the original machine - % - parallel cylinder is changed to - parallel cylinder and installed in the original machine four columns The corresponding position of the cylinder. After the transformation, the balance chamber in the parallel cylinder is also the same as the scheme 2, regardless of the level of the suction pressure, and the atmospheric pressure is applied. See the serial number 3 column for a schematic diagram of its structure.

Option 4: Convert the original machine into a three-stage compressor, that is, keep the vertical column-flat-column and horizontal column of the low-pressure side of the original machine-%-level column and change it to - flat-flat 2 columns and - flat columns. The balance chamber 1 and the balance chamber are the corresponding balance chambers in the original machine-flat-, -%-parallel, and the atmospheric pressure is applied, and the balance chamber 2 is transformed from the stage cylinder in the original machine-flat-column (demolition) The suction and exhaust valves can be directly connected to a certain stage of suction pressure. The vertical column and horizontal column of the high pressure side are removed, and the double column and the four column structure form with the same arrangement of the cylinders on both sides are transformed into a structural diagram. See column 4 of the serial number.

Option 5: The original machine is transformed into a three-stage compressor, that is, the vertical column of the high-pressure side of the original machine is removed, and the horizontal column-flat-column is replaced by the vertical column-flat-column of the low-pressure side of the original machine, wherein the balance chamber is introduced into the atmosphere. The pressure is changed to the double L four-column structure with the same arrangement of the cylinders on both sides similar to the scheme 4, and the structure diagram is shown in the column of the serial number.

Scheme 6: Reconstructing the original machine into a four-stage compressor, that is, retaining the vertical column-flat-column and horizontal column of the low-pressure side of the original machine-----column changing it to -flat-and--parallel, where-flat - The balance chamber of the column is connected to the atmospheric pressure. - The balance chamber of the %-series can be fed into a certain stage of suction pressure according to the balance of the piston force. The vertical column and the horizontal column of the high pressure side are removed, and the two sides are also transformed into two sides. The cylinders are arranged in exactly the same double L four-column structure. For the structure diagram, see the column number 6.

According to the principle of transformation, when the total indicated power is 240kW + Ni + 280kW and the maximum piston force p + 40kN in the column is the constraint condition, the suction and exhaust pressures and displacements of the above six reform schemes are calculated after repeated calculations. The range of indicated power and piston force is as shown. If the process parameters of the modified target machine, such as suction, exhaust pressure, and exhaust volume, are in the range, it is expected that the L3 3- 17/320 hydrogen-nitrogen compressor can be used to achieve better results.

5 transformation examples

5. 1 known parameters

A fertilizer plant needs a compressor in the new dimethyl ether production process. The process parameters are as follows:

Suction pressure ps 0. 45MPa (gauge pressure) exhaust pressure pd 7. 0MPa (gauge pressure) suction temperature ts + 30, displacement V d 2300m 3 / h (normal pressure, 20, state. Inhalation state Ps = 0 55MPa, ts = 30, 7 35m 3 /min) Gas composition CO 20% H 2 50% remaining N 2, CH 4, CO 2 30%

It is now decided to retrofit the L3 3- 17/ 320 hydrogen-nitrogen compressor that has been eliminated from the plant to meet production needs.

5. Determination of 2 series and pressure ratios at various levels

According to the known process conditions, the modification scheme shown in the serial number 4 can be adopted, that is, the number of stages is three. The suction and discharge pressures and pressure ratios of the various stages are calculated from known conditions.

If the mechanical efficiency m = 0, the transmission efficiency c = 1 0, then the motor power N e = 267 3kW, the motor with the original power of 320kW will have a power reserve of 19 7%, slightly running. The suspicion of the big horse car is the shortcoming of this plan.

5. 3 piston force calculation

In order to improve the balance of the piston force of each column, according to the scheme structure shown in No. 4, the volume of the cylinder in the original machine is changed into the balance volume, and the stage suction pressure of the machine (0 55MPa) is introduced, and the original machine - The balance volume on the interstage and -stage cylinders remains and is exposed to atmospheric pressure. According to this structure, the piston forces of each column are calculated as shown.

The horizontal column (--flat) on the side of the shaft piston force p. = 39 43kN, larger than the original design value of 33000N (3 3 tons). For safety reasons, the cylinders, pistons, piston rods and transmission parts (crankshaft, connecting rod, crosshead) have been checked for strength, and all the calculations have been met. In addition, since the pressure difference between the horizontal column-level cylinder and the stage-balance chamber of the machine after the transformation is larger than that before the modification, a piston ring is added to the 155 piston body of the -stage differential piston, respectively, in the 115 piston body. Two piston rings are added to ensure the gas tightness.

5. 4 tangential force balance

Due to the large changes in the operating conditions of the original machine after the transformation, the balance of the tangential force of the original machine is inevitably destroyed. To ensure the smooth operation of the machine after the transformation, it is necessary to balance the new tangential force.

According to the dynamic calculation, for each side, when the vertical column (-flat 1-flat 2) rotates in the direction of the leading horizontal column (--flat) 90/, the maximum energy change amount Lmax of the machine has a small value. Also from the power calculation, L max is the smallest (L max = 1906 Nm) when the crank angles of the two sides are 190/ in the direction of rotation shown. Considering the actual situation and feasibility of the connection between the motor and the machine coupling, the crank angle of the two sides is 180/, and L max = 2160Nm. If the rotation unevenness is 80, then GD 2 = 2490Nm, less than The flywheel moment of the original matching motor TDK320-12 meets the requirements.

In addition to the above-mentioned transformation measures, other parts or structures such as gas valves, packing seals, pistons, etc., can be used to meet the requirements of the machine after the transformation, so it can be used without modification.

6 conclusion

L3. 3- 17/ 320 Nitrogen and Hydrogen Compressor has a large possession in China's small nitrogen fertilizer plant. How to transform these eliminated models for other purposes is the current small nitrogen fertilizer plant reconstruction potential, energy saving and efficiency An important way.

L3. 3- 17/ 320 compressor original design pressure range is wide, cylinder structure and diameter types are more, the transmission member's strength safety margin is large, adapt to a wide range, only need to invest a small cost to modify it slightly It can be used in other production processes. After a lot of repeated calculations, this paper gives several reconstruction schemes that can be expected to get a satisfactory structure, and illustrates the specific implementation method of the transformation by an example, which can be used as a reference for manufacturers with such transformation wishes and interests. .

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