JPS6348997B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a dryer for a paper machine, and is related to Patent No. 938365, and is further developed and relates to a method of using the same, combining a constant reduction valve and a flow rate detector. , a condensate discharge technique intended for a method related to a volumetric condensate discharge flow control system. (Prior Art) The steam supply and drain discharge system for the dryer of a paper machine has traditionally been based on a differential pressure control system. In other words, it was a flow Lucascade differential pressure control system that mainly controlled the differential pressure between the steam header pressure and the drain header pressure, or between the high pressure group steam header pressure and the next pressure group. (Problems to be Solved by the Invention) The differential pressure control system, which is a steam supply drain discharge method for the dryer of a conventional paper machine, controls the differential pressure between the steam header pressure and the drain header pressure, or between the high pressure group steam header pressure and the next pressure group. The system is based on the Blows Lucascade differential pressure control system, which is based on the fluid pressure and its It changes greatly depending on the gas-liquid mixing ratio. In other words, if the vapor pressure is high, the differential pressure will be large when seeking the same flow rate. As the volume ratio increases with respect to gas, the specific volume of the mixed fluid increases, and when the same flow rate is sought, the differential pressure decreases. Therefore, the fluid in the drain changes accordingly, and even if the differential pressure is set in accordance with the papermaking speed of the papermaking conditions, there are many cases where a completely different gas-liquid mixed two-phase flow results. Therefore, not only was it not possible to obtain the same blow-through flow rate, but there was often a risk that the drain would not be properly discharged. Also, most of the differential pressure was used as a large friction loss pressure due to the high flow rate of the mixed flow of condensate and steam. (Means for Solving the Problems) The present invention provides a flow rate detector and a constant reduction valve between the next pressure group steam supply pipe for the recovered steam sent to the next pressure group and the air discharge side of the steam water separator. By installing them in combination, a constant flow rate can be obtained for the piping system.The structure is such that the gas-liquid mixed fluid discharged from one or more rotating pressure vessels is separated by a separator, and the steam is separated by a separator. When mixed with new steam in the next pressure group or used alone, the constant reduction valve 1
4. Also, a valve similar to this is used to reduce the pressure, and a flow rate detector 15 connected to this is used to reduce the pressure in proportion to the inverse ratio of the flow rate.
This drain discharge method mainly uses volumetric flow by adjusting the opening degree of the drain and keeping the set flow rate constant. (Function) According to the present invention, the same flow rate can be maintained almost unaffected by changes in pressure and changes in the air/water mixing ratio. Therefore, this ensures that the drain discharge is almost reliably maintained even when the machine speed changes or the amount of drain generated changes. However, if the set flow rate given to the flow rate detector 15 of that pipe cannot be obtained, it is because there is not enough pressure difference between the high pressure group and the next pressure group to generate the flow rate, so the high pressure group is more The set flow rate is achieved by increasing the pressure or by increasing the next pressure group to a lower pressure. If the differential pressure between the high pressure group and the next pressure group is greater than the velocity relative pressure for obtaining the set flow rate, the excess differential pressure will automatically become a pressure loss by the opening degree of the constant reduction valve 14. This means that a constant flow rate can be maintained. (Example) An example of the present invention will be described based on the drawings. Steam from the steam header 1 of the dryer of the paper machine passes through the steam branch pipe 2 to the dryer 5, and then to the rotary joint 3.
The steam is released into the dryer 5 from the injection port 4 via. The steam that gives heat to the wet paper and dries it becomes condensate, and the generated condensate passes through the shower 6.
It mixes with steam to form a mist flow, passes through the drain horizontal pipe 7, drain branch pipe 8, and drains into the drain header 9.
are collected from each single cylinder dryer. Next, the drain passes through the drain conduit 10 to the flushing tank 11, where the pressure loss is re-evaporated, and the drain is discharged through the drain outlet 12. Steam, which is a combination of Brostle steam and reevaporation, enters the constant reduction valve 14 through the steam outlet 13, receives the necessary pressure reduction under the opening control, passes through the flow rate detector 15, reaches a constant flow rate, and then flows into the recovery steam pipe 16. leading to. There, this recovered steam is mixed with fresh steam and supplied to the next pressure group. Regarding the instrumentation shown in FIG. 4, the frequency at which Karman vortices occur due to the flow velocity of the flow velocity detector 15 is passed through the vortex flow rate converter 17, and the converted electrical signal is transmitted through the signal cable 20 to the indicating controller 19. reach. There, the signal is converted into pressurized air, passes through the instrumentation conduit 21, and reaches the opening degree conversion piston drive section of the constant reduction valve 14, where it is checked whether the commanded flow rate matches the set flow rate. To further explain the characteristics of the drain discharge according to the present invention using paper drying as an example, ordinary multi-barrel dryers are classified into high pressure groups, low pressure groups, medium pressure groups, and high pressure groups according to the direction of paper travel. The steam is then passed through the high pressure group, intermediate pressure group, and low pressure group in series, and the remaining steam enters the condenser at the end of the low pressure group. During this time, the shortage of steam is supplied by mixing new steam with recovered steam by a replenishment valve. From the steam inlet of the high pressure group,
The section up to the steam inlet of the intermediate pressure group will be explained in detail, and the rest will be omitted since they are almost the same. First, steam is supplied to the steam header 1 shown in Figure 1 under the required pressure, and then to the individual dryers 5 shown in Figure 2.
The steam passes through the steam branch pipe 2 and is supplied from the injection port 4 to the interior of the rotating pressure vessel of the dryer 5 via the rotary joint 3. The dryer 5 dries the paper and radiates heat, so that a portion of the steam condenses and becomes drain. Drainage accumulates on the inner wall of the dryer 5 and increases the amount of water, resulting in a circular ring shape or a pond shape depending on the circumferential speed. The condensate, which has been sufficiently affected by centrifugal force, flows towards a lower pressure area and enters the shower 6 together with the steam. Depending on the steam to condensate volume ratio and the blow-through steam velocity, this two-phase flow becomes a mist flow. As a result, it reaches the center of the dryer 5 against the centrifugal force, passes through the drain horizontal pipe 7, and then goes through the drain branch pipe 8.
through the individual dryers 5 to the drain header 9.
collected from. Next, the drain passes through the drain conduit 10 in FIG. 1, where the pressure loss is re-evaporated, and the steam expands in volume and reaches the flushing tank 11 in FIG. 3. It collides with the water surface of the drain in the flushing tank 11, and the steam is is reversed, and the drain water droplets sink into the drain water surface and form a drain pool. The fluid separates the condensate into a single phase stream of steam and enters the regulating valve 14 via the steam outlet 13. The constant reduction valve 14 introduces this steam into a valve seat having multiple holes, and by sliding this valve, the opening degree is adjusted by moving the sliding valve. decide. The outer periphery of the valve seat has a multi-layered disc with high and low resistance, and steam passes through this radially, causing pressure loss due to diffusion, compression, and friction loss, leaving only the velocity-equivalent pressure, which remains constant. It exits the reducing valve 14 and enters the flow rate detector 15. The flow velocity detector 15 shown in FIG. 4 is a vortex flowmeter, and one of its main components is to place an obstacle perpendicular to the flow of fluid in the pipe, thereby generating Karman vortices alternately. Since the flow velocity is linearly proportional to the vortex generation frequency, the flow velocity can be detected. An electrical signal representing the vortex generation frequency is passed through the vortex flow rate converter 17, and is then sent via a signal cable 20 to an indicating controller 19. There, the signal is converted to compressed air and passed through the instrumentation conduit 21.
The flow reaches the opening degree conversion piston drive unit of the constant reduction valve 14, and it is checked whether the commanded flow rate matches the set flow rate. However, if the indicated flow rate does not match the set flow rate, this may be due to excessive or insufficient pressure, or some kind of malfunction. By fixing it, things can be normalized. When the indicated flow rate approximates the set flow rate, it reaches the recovery steam pipe 16, where fresh steam is mixed with the steam supply for the next pressure group (in this case, the intermediate pressure group), and reaches the steam header of the intermediate pressure group, where it reaches the high pressure group. will be processed in the same way as , but will be omitted as it is redundant. Table 1 shows a comparison of the numerical values of each part of the conventional constant differential pressure method and the operational papermaking method of the present invention. In addition, Table 2 shows a comparison of the actual values of each part of the conventional constant differential pressure method and the paper break paper making method of the present invention in the case where the paper breaks for some reason during paper making.

【table】

【table】

【table】

[Table] Table 1 shows that when the conventional constant differential pressure method and the constant flow rate method of the present invention are compared, the blow-through of the present invention is reduced by about half, and as a result, the flow rate of the drain system is also reduced by half. , wasteful release of steam can be reduced. Table 2 also shows that when comparing the conventional constant differential pressure method and the constant flow rate method of the present invention, the amount of steam released during paper breakage is approximately 1 It turns out that /4 is sufficient. (Effects of the Invention) According to the present invention, unlike conventional differential pressure control systems, the flow rate is constant, so changes in pressure,
Almost unaffected by changes in air/water mixing ratio,
It is possible to maintain the same flow speed. Therefore, as a result, drain discharge can be almost reliably maintained without worrying about changes in the machine speed, changes in the amount of drain generated, etc. Furthermore, compared to the conventional constant differential pressure system, the present invention reduces the blow-through by about half, as is clear from Table 1, and as a result, the flow rate of the drain system is also reduced by half, so wasteful release of steam can be reduced. There is a benefit of greater steam savings and therefore smaller equipment.
Furthermore, as shown in Table 2, the amount of steam released when paper breaks for some reason during papermaking is sufficient to be about 1/4, which contributes to energy conservation. It is.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, and FIG. 1 is a flow control system diagram of the present invention;
Figure 2 is a partially cutaway front view of the same dryer section.
Figures 3 and 4 are diagrams of the flow control system of the same essential parts, Figure 5 is a front view of the flow velocity detector used in the present invention, Figure 6 is a side view of the flow velocity detector of Figure 5, and Figure 7 The figure is a front view of the overflow converter used in the present invention, and FIG. 8 is a side view of the overflow converter of FIG. 7. 1 is a steam header, 2 is a steam branch pipe, 3 is a rotating joint, 4 is an injection port, 5 is a dryer, 6 is a shoe,
7 is a drain horizontal pipe, 8 is a drain branch pipe, 9 is a drain header, 10 is a drain conduit, 11 is a flushing tank, 12 is a drain outlet, 13 is a steam outlet,
14 is a constant reduction valve, 15 is a flow rate detector, 16 is a recovery steam pipe, 17 is a vortex flow rate converter, 19 is an indicating controller,
20 is a signal cable, and 21 is an instrumentation conduit.

Claims (1)

[Claims] 1 The gas-liquid mixed fluid discharged from one or more rotating pressure vessels is separated by a separator, and when the steam is mixed with new steam in the next pressure group or used alone, a constant pressure reduction flow control valve or similar device is used. By reducing the pressure using a valve and using a flow rate detector connected to this, the opening of the reduction valve is adjusted in proportion to the inverse ratio of the flow rate, and the set flow rate is always maintained constant. , a drain discharge method based on volumetric flow.