JPH0117968B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a device for pneumatically transporting powder and granular materials, which allows the amount of transport discharge from a pressurized tank to be adjusted over a wide range.

Various methods and devices have been proposed for transporting powder particles at a constant flow rate under various conditions and at desired set flow rates.

A known method is to increase or decrease the amount of discharge by increasing or decreasing the booster flow rate, but this method cannot be applied when the transport pipe is short and the efficiency becomes extremely poor if the adjustment range is widened. In addition, various conditions or restrictions may apply.

To solve this problem, for example, Japanese Patent Application Laid-Open No. 58-100021
(Japanese Patent Application No. 56-199410), the pressure in the transport pipe near the supply end is 20 to 40% of the differential pressure between the pressurized tank pressure and the supply end pressure.
By installing a fixed resistance (orifice) that causes a pressure loss and applying the limit orifice principle before and after the resistance, we propose a method for transporting a constant flow rate at a set flow rate regardless of fluctuations in the supply end pressure.

Although this solution achieves its purpose in a certain flow rate range, it generates an excessive pressure difference, resulting in a lot of energy loss, and the restriction ratio that satisfies the limit condition becomes too small, which may lead to blockage depending on the nature of the powder. This has the disadvantage that it is easy to cause

The present invention solves the above-mentioned drawbacks and provides an apparatus that can adjust the amount of powder discharged over a wider range.

The present invention provides a throttle ratio of 1/1.2 at a position relatively upstream of the transport pipe and downstream from the booster gas supply point.
By inserting a ~1/3 throttle tube, a relatively small pressure loss (10 ² ~ 10 ³ mm) is generated in this part, and this loss can be varied over a wide range with a slight change in the booster gas volume. Therefore, even if the tank pressure is constant, the discharge amount can be changed over a wide range, and even if the piping is short, it can be effectively adjusted by adjusting the booster amount, and since the loss is small, energy consumption is low and it is economical. .

Next, the principle of the present invention will be explained.

The piping pressure drop ΔP of the solid-gas two-phase flow is expressed as ΔP=ΔPa+ΔPs, where ΔPa is the pressure drop due to gas and ΔPs is the pressure drop caused by the powder. Then,
There is a relationship between ΔPs and the tank weight reduction rate, that is, the amount of powder discharged per hour dw/dt: ΔPs=f(dw/dt).

Assuming that ΔP is equal to the internal pressure Pt of the pressurized tank, since ΔPa≪ΔPs, Pt∞ΔPs=f(dw/dt), which represents the basis of internal pressure control.

Now, if the constrictor tube 6 is installed in the transport pipe as shown in Fig. 1, △Pa≪△Ps no longer holds, and △Pa≒
g(Q). However, Q is the transport gas flow rate.
Substituting this into the previous equation, Pt = const (constant) = g (Q) + f (dw / dt) ∴f (dw / dt) = const - g (Q) dw / dt = const' - g' (Q) That is, when the aperture ratio of the throttle tube 6 is increased, the change in the transport gas flow rate Q due to the change in △Pa becomes larger, and the adjustment range of dw/dt to the change in Q within a certain range becomes larger as shown in Fig. 2, and the responsiveness increases. It also improves significantly. Furthermore, since the throttle tube is provided in a portion where the powder flow is thin, there is an advantage that wear is reduced.

The inventive device will be explained below.

FIG. 1 shows an embodiment of the present invention, in which 1 is a pressurized tank, 2 is a charging valve, 3 is a fluidized bed, and 3a is a fluidized bed chamber. Reference numeral 4 designates one or more extraction pipes that open above the fluidized bed, and 6, which is connected to the transport pipe 5 via a discharge valve 18 that operates to open and close, represents a throttle pipe inserted in the transport pipe. It is installed in the downstream area of the pipe. Note that the throttling ratio of the throttle tube to the transport pipe varies depending on the supply end pressure or the range of the powder supply amount, but usually it is 1/1.2 to 1/2 when the transport pipe diameter is 1.
It is generally preferable to set it in the third place range.

Pressurized gas from a pressurized gas supply source (not shown) is divided and supplied from the supply line 7 to the pressurizing line 7a and the booster line 7b.

The pressurized gas supplied to the fluidized bed chamber 3a is controlled at a fixed value via a control valve 10 controlled by a pressure regulator 11, and is supplied to the booster line 7.
The booster gas supplied to b is adjusted by adjusting the setting value of the flow rate controller 13 that operates the flow rate control valve 9 based on the weight detector 15 that detects the amount of powder and granule discharged from the pressurized tank 1. It changes depending on the dw/dt output of the device 14, and is supplied at a flow rate adjusted according to dw/dt.

8 is a flow rate detector, 12 is a ratio setter, 16 is a pressurizing valve, 17 is a booster valve, and 19 is a booster branch pipe.

In the above device, when changing the supply amount to the supply end of the transport pipe, by changing the set value of the discharge amount controller 14, the booster flow rate Q changes immediately, and the discharge amount and therefore the amount changes as shown in Fig. 2B. The amount of supply is changed.

The response time in the device of the present invention is approximately 5 seconds to 15 seconds.
The response time of conventional internal pressure control is 30 seconds to 5 minutes, which is much faster than the response time of conventional internal pressure control, which is 30 seconds to 5 minutes. For this reason, high pressure (0.5 to 20 Kg/cm ² G) such as steel production injection system and pulverized coal combustion system, etc.
Even at the high temperature (1500°C) supply end, it is now possible to safely and easily change the setting of the supply amount during supply.

In the past, when changing the dw/dt setting, a mechanical variable throttle was inserted in the middle of the extraction pipe in order to speed up the apparent response, but this is completely unnecessary in the present invention.

In addition, even when the device of the present invention is supplied through multiple transport pipes, there is little mutual interference between the transport pipes, and it is also possible to stop the supply from one of these pipes, so when it is necessary to drastically change the supply amount. For example, the booster supply of one of the parallel transport pipes can be stopped and the supply amount can be increased or decreased using only the remaining one, greatly expanding the supply amount variable range of the entire device.

Further, the flow rate Q of the booster gas can be adjusted not by the flow rate control valve (9) but by using the booster branch pipes 19 corresponding to the solid extraction pipes 4, as shown in FIG.
It is also possible to control the flow rate regulating valve 21 provided in the pressurized tank 1 based on the amount of powder and granular material discharged from the pressurized tank 1 in the same manner as in the embodiment shown in FIG. In addition, in Figure 3,
20 is a flow rate detector, 22 is a ratio setter, 23 is a flow rate controller, and 24 is a booster branch valve.

[Brief explanation of drawings]

Figure 1 is a schematic configuration diagram of the device of the present invention, Figure 2A is a graph showing the relationship between the change in the internal pressure of the pressurized tank and the discharge amount, and Figures 2 and B are graphs showing the relationship between the transport gas flow rate and the discharge amount. , FIG. 3 is a schematic diagram showing another embodiment of the device of the present invention. 1 is a pressurized tank, 3 is a fluidized bed, 4 is an extraction pipe, 5
is the transport pipe, 6 is the throttle pipe, 7b is the booster line,
9 and 21 are flow control valves, and 11 is a pressure regulator.

Claims (1)

[Claims] 1. At least one extraction pipe is open and disposed above the fluidized bed in the pressurized tank, and the pressure inside the tank is controlled to be constant, and the transport pipe connected to the extraction pipe is connected to the pressure tank. In a powder transport device in which booster gas whose flow rate is adjusted according to a reduction signal is supplied, a throttle pipe with a throttle ratio of 1/1.2 to 1/3 is provided at a position downstream from the booster supply position to the transport pipe. A gas transport device that allows easy adjustment of the amount of powder and granular material discharged.