JPH0533838Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] This invention relates to a device that transports LPG (liquefied petroleum gas) from a low-temperature normal-pressure tank to a pressurized normal-temperature tank whose pressure changes. This allows the pump to always operate with the minimum amount of power even if the pressure in the side room-temperature tank changes.

[Conventional technology]

At storage bases for LPG (liquefied petroleum gas) such as propane and butane, low-temperature normal pressure tanks (hereinafter simply referred to as normal pressure tanks) with a double shell structure and equipped with insulation are used for large-volume storage. When supplying as LPG, the low-temperature LPG is sucked and pressurized with a liquid feed pump, and then transferred to a pressurized room temperature tank such as a spherical tank (hereinafter referred to simply as a room temperature tank) via a heater. These propane, butane, etc. are stored in a predetermined ratio and sent to a mixing tank, which is one of the room-temperature tanks, and the mixed and stored mixture is used, or it is used directly without mixing.

[Problem that the invention attempts to solve]

In the room-temperature tanks of such LPG storage bases,
Because it does not have an insulated structure, the internal pressure changes with changes in outside temperature, resulting in quite large pressure changes between summer and winter. For example, in the case of propane, the temperature rises to about 12Kg/ ^cm2 in the summer, while in the winter it rises to about 4Kg/ ^cm2 , and in the case of butane, it rises to about 5Kg/cm2 in the summer.
While it rises to about Kg/cm ² , it drops to about 0 Kg/cm ² in winter (all gauge pressure).

Therefore, when determining the capacity of the liquid pump, it is necessary to ensure that the discharge pressure is sufficient even in the summer when the pressure is highest.

However, if a liquid feeding pump is used that can obtain the necessary discharge pressure in the summer, the pump capacity will become excessive when the pressure inside the normal temperature tank decreases as in the winter.

Therefore, in the winter, a valve is installed on the discharge side of the liquid pump to adjust the volume, and the pumping power of the liquid pump is wasted.

In other words, the second curve representing the performance curve of the liquid pump is
As shown in the figure, assuming that the actual head in the summer when high discharge pressure is required is h, and the resistance of the pipeline etc. can be expressed by a resistance curve R, it corresponds to the intersection point A with the head curve H. The amount of liquid Q that can be pumped can be pumped, and the shaft horsepower at that time becomes point a on the diagram S.

On the other hand, if the pumping head in winter, when a low discharge pressure is sufficient, is h', the resistance of pipes, etc. increases due to throttling with a valve, and the resistance curve becomes R'' (constant chain line), resulting in the same pumping amount as in summer. When securing Q, the shaft horsepower of the liquid pump remains at point a on the diagram S, and the pump power is wasted by the amount shown by diagonal lines in the diagram.

This idea was made in view of the problems of the conventional technology, and it is possible to control the discharge pressure according to the pressure change at the supply destination, eliminate waste of pump power, and reduce operating costs. The aim is to provide a liquid device.

[Means for solving problems]

In order to solve the above problems, this idea is based on LPG
A device that pumps LPG from a normal pressure tank that stores it at low temperature and normal pressure to a room temperature tank that stores it at room temperature under pressure according to the outside temperature, sucks LPG from the normal pressure tank and pumps it to the room temperature tank where the pressure changes. A liquid sending pump, a temperature sensor that detects the atmospheric temperature near the room temperature tank on the discharge side of this liquid sending pump, and a liquid sending system that uses the detection signal from this temperature sensor to make the discharge pressure higher than the pressure in the room temperature tank. The pump is characterized by comprising a rotation speed controller that controls the rotation speed of the pump.

[Effect]

The pressure inside the room-temperature tank where LPG pressurized by the liquid feed pump is stored is determined by detecting the atmospheric temperature near the room-temperature tank, and the rotation speed controller adjusts the liquid feed pump to match the required discharge pressure based on this atmospheric temperature. The number of rotations of the liquid pump is controlled so that the liquid pump is always operated with the minimum amount of pump power necessary, thereby eliminating waste and reducing operating costs.

〔Example〕

Hereinafter, one embodiment of this invention will be described in detail based on the drawings.

FIG. 1 is a schematic diagram of an embodiment of the LPG liquid feeding device of this invention.

This LPG liquid feeding device 10 is installed at an LPG base where propane and butane are used as raw materials to produce a gas mixture thereof, or where these gases are used directly as raw materials. The raw material gases, propane and butane, are stored in normal-pressure tanks 11 and 12, each of which has a double shell structure and is equipped with an insulating material, and are kept at almost atmospheric pressure, and the evaporated gas is stored in a refrigerator or the like. It is compressed and reliquefied.

These normal pressure tanks 11 and 12 are sucked into dedicated liquid feeding pumps 13 and 14, respectively, and the heater 1
5, 16 and three-way switching valves 17, 18, the liquid is sent to normal temperature tanks 19, 20 such as spherical tanks.

These room-temperature tanks 19 and 20 are constructed as pressure-resistant containers so that propane and butane can be stored in a pressurized state, such as a pressure that corresponds to the outside temperature.

These normal temperature tanks 19 and 20 are connected to flow rate detectors 21 and 2 via three-way switching valves 17 and 18, respectively.
2 and flow rate regulating valves 23 and 24 are connected to adjust the mixed amount of propane and butane, and then stored in a spherical mixing tank 25, which is one of the room temperature tanks. The LPG mixed in the mixing tank 25 is then put into a tank truck, small tanker, or cylinder and used as fuel.

Near these normal temperature tanks 19 and 20,
A temperature detector 26 is installed to detect the outside temperature, and a detection signal is sent to each liquid pump 13,
Rotation speed controllers 27 and 28 that control the rotation speed of 14
It is now entered into .

These rotational speed controllers 27 and 28 determine the storage pressure of propane and butane in each of the room temperature tanks 19 and 20 from the outside temperature near the room temperature tanks 19 and 20, and supply the gas at a discharge pressure that is slightly higher than this storage pressure. The rotational speed of the liquid pumps 13, 14 is calculated, a control signal is output, and the power frequency of the drive motor of each liquid pump 13, 14 is changed using an inverter, etc., so that the liquid pumps 13, 14 can be rotated at a predetermined speed. Drive by numbers.

Therefore, when the outside temperature rises and the propane and butane in the room-temperature tanks 19 and 20 reach a high pressure state, as in the summer, the respective storage pressures are determined from the outside temperature detected by the temperature sensor 26, and this The rotational speed N of the liquid feed pumps 13, 14 corresponding to the discharge pressure slightly higher than the determined storage pressure is calculated, and the liquid feed pumps 13, 14 are operated accordingly.

On the other hand, when the outside temperature drops and the storage pressure of propane or butane in the room-temperature tanks 19, 20 decreases, such as in winter, it is possible to send liquid even if the discharge pressure of the liquid sending pumps 13, 14 is lowered. The storage pressure in each room temperature tank 19, 20 is determined from the outside temperature detected by the temperature sensor 26, and the rotational speed N' of the liquid feed pumps 13, 14 corresponding to the discharge pressure slightly higher than this storage pressure is calculated. and driven.

These will be explained using the performance curves of the liquid pumps 13 and 14 shown in FIG.

First, when the storage pressure in the room-temperature tanks 19, 20 is high in the summer, etc., it is necessary to increase the discharge pressure of the liquid pumps 13, 14. can be drawn as shown.

In addition, the head curve H and shaft horsepower line S when the rotational speed of the liquid pumps 13 and 14 are N are also shown in the figure, and the amount of water pumped in this case is determined from the intersection A of the resistance curve R and the head curve H. Q, and the shaft horsepower becomes a.

Next, when the storage pressure of propane or butane in the room-temperature tanks 19, 20 decreases during winter, etc., it becomes possible to lower the discharge pressure of the liquid pumps 13, 14, and the head drops to h'. If so, since the resistance of the conduit etc. does not change, it can be shown by a resistance curve R' (broken line) obtained by moving the resistance curve R in parallel.

In this case as well, the amount of pumped water Q is the same as in summer, etc.
If this is to be ensured, the intersection point X between the pumped water amount Q and the resistance curve R' is found.

Therefore, the rotation speed N' at which a head curve H' (broken line) passing through point X is obtained by lowering the rotation speed of the liquid feed pumps 13 and 14 is calculated by the rotation speed controllers 27 and 28, and the liquid is fed at this rotation speed N'. The liquid pumps 13 and 14 are operated.

Then, when this rotational speed is N', the shaft horsepower line corresponding to the head curve H' becomes S' (broken line), and when the amount of pumped water is Q, the required shaft horsepower is point b, and the pump power is It can be seen that this decreases.

In this way, the liquid sending pumps 13 and 14 are operated with the discharge pressure set to the minimum necessary level according to the pressure of the pumping destination, so there is no waste of pump power unlike when using a throttle valve, and the pumps can be operated efficiently.

In the above embodiment, a liquid feeding pump is installed in each room-temperature tank, but it is also possible to switch between using one liquid feeding pump.

Furthermore, the applicable LPG is not limited to propane and butane. Furthermore, it is applicable not only to cases where propane and butane are mixed, but also when they are used directly.

[Effect of idea]

As explained above in detail with one embodiment, according to the LPG liquid feeding device of this invention, the pressure inside the room temperature tank in which LPG pressurized by the liquid feeding pump is stored is detected by the atmospheric temperature near the room temperature tank. Based on the atmospheric temperature, we used the rotation speed controller to control the rotation speed of the liquid pump to match the required discharge pressure, so the liquid pump was always operated with the minimum power necessary. can save operating costs.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 are schematic diagrams of the configuration and explanatory diagrams of performance curves of an embodiment of the LPG liquid feeding device of this invention. 10... LPG liquid feeding device, 11, 12... Normal pressure tank, 13, 14... Liquid feeding pump, 15, 16
... Heater, 17, 18 ... Three-way switching valve, 19,
20... Normal temperature tank, 21, 22... Flow rate detector, 23, 24... Flow rate adjustment valve, 25... Mixing tank, 26... Temperature detector, 27, 28... Rotation speed controller, H, H ′……Head curve, R, R′, R″…
...Resistance curve, S, S'... Shaft horsepower line, N, N'...
Rotation speed, h, h'... Actual head, Q... Amount of water pumped.

Claims (1)

[Scope of utility model registration request] A device that pumps LPG from a normal pressure tank that stores LPG at low temperature and normal pressure to a normal temperature tank that stores it at pressurized room temperature according to the outside temperature.
A liquid pump that suctions LPG and pumps it into a room-temperature tank where the pressure changes, a temperature detector that detects the atmospheric temperature near the room-temperature tank on the discharge side of this liquid pump, and a An LPG liquid feeding device comprising a rotational speed controller that controls the rotational speed of a liquid feeding pump so that the discharge pressure is higher than the pressure in a room temperature tank.