JPH01502038A - Dryer differential pressure control device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Dryer differential pressure control device The present invention controls the differential pressure between the steam input line and the output line of a web dryer. This relates to a control device for More particularly, the present invention provides a drying section steam input line for a paper machine. The invention relates to a control device for controlling such differential pressure between the in and output lines.

Description of prior art In paper making machines, the formed web passes through the paper drying section immediately after passing through the press section. pass The darning drying section contains multiple heated rotating cylinders that dry the web as desired. A wet paper web is passed over it to obtain the desired dryness. Even more clearly In the conventional drying section, the wet web is heated with steam in a super steel drying cylinder. It is passed around the outside of the The steam used to heat these dry cylinders is It enters the dryer through a hollow journal by means of a rotating seal, and the dryer outer shell or circle It condenses inside the cylinder. Steam condenses on the inner surface of the dryer's rotating cylinder, causing The condensed water is removed by a siphon assembly. However, the rotating cylinder is dry. Web speeds of 5.08 m/sec to 6°1 m/sec, which are not uncommon in the If the dryer is operated at high speed, the condensed water will not collect at the bottom of the dryer, but rather dry. It is thrown around the inner surface of the machine's cylinder or shell by centrifugal force.

This property of condensed water inside the dryer enclosure is known in the art as the "fringing phenomenon." It is known as TAPPI 1958. by R, E, White. vo It is fully described in the paper published in lume 41° No. 2.

The dryer enclosure is not exposed to “live steam” when surrounded by condensate. , a layer of condensed water that impedes conduction from live steam to the surface of the dryer envelope and nearby paper web. insulated from live steam by Such insulation attenuates the drying effect; This resistance to heat conduction reduces the thickness of the condensate layer within the dryer envelope. Can be kept more minimal.

Accumulation of non-condensable vapor inside the dryer envelope is due to the cross-mechanical aspect of the dryer's drying characteristics. This may increase the heterogeneity along the direction. This problem is caused by TAPPI, volume 46. No. 9. Published in 1963 and stated by R.B. Hurm. . Such accumulation or accumulation of non-condensable vapors or gases is not condensed. Some of the steam, or water vapor, is continuously discharged from the dryer shell along with condensed water. can be kept to a minimum by This uncondensed vapor or vapor stream may entrain non-condensable gases and prevent accumulation of such gases within the dryer envelope.

Moreover, such steam flow reduces the differential pressure between the input and output steam lines in the dryer shell. Although it has a beneficial secondary effect, such a pressure differential is not necessary to drain the condensate. It will be done. The low-density vapor stream entrains high-density condensate water and mixes with the high-density condensate water to produce A two-phase mixture is formed which is qualitatively less dense than the condensed water. Comparison of steam and condensed water This mixture, which has a relatively low density, is discharged against the centrifugal force created by the rotation of the dryer shell. The differential pressure required for is relatively reduced. Moreover, this steam flow requires low pressure steam. It can be used in other dryer enclosures in the required drying section. Alternatively, such a vapor flow Of course, the condition is that the differential pressure across the dryer shell is not very large. The same dryer shell has its pressure increased or added for reuse. It's fine.

A further consideration regarding condensate discharge is the requirement for operational stability. fruit As a practical problem, if the outer tip of the siphon pipe, which is close to the condensed water, gets into the condensed water. If it is submerged further, the fastest condensate drain can be stopped. Admitted. In this case, the dryer will be filled with condensed water, so the drying speed will be decreases and the load on the dryer drive increases proportionately. These problems are Da's Pu1p & Paper Magazine, volume 65. No , 14.1964 by T. A. Gardner, and more specifically 19 TAPPI Technical Information published in 1983.

n5heets, highlighted and discussed in Tl5O14-60.

From the foregoing it can be seen that several goals are being pursued with condensate drainage systems. The first of these goals is to at least dry the dryer so that it does not flood. The objective is to discharge condensed water at a rate equal to the rate of condensed water formation within the machine envelope.

It is then condensed so that the rate of heat transfer from the "live steam" to the paper web is as high as possible. One objective is to keep the layer of condensed water as thin as possible. The third is drying speed Non-condensable gases are evacuated so that improved cross-machine uniformity can be achieved. It is to remove it. Fourth, while maintaining stable operation of this system, Achieve condensate removal from the dryer envelope while using the minimum differential pressure required. That's true.

Many methods have been proposed in an attempt to achieve the four objectives mentioned above, and Suggestions are rPaper Machtne Steam & Condensate In the TAPPI publication entitled Systems J, H.P. Fishw. ick. In addition, these basic concepts are transferred to Cardnet. U.S. Patent No. 4,447°964 to JustuS and U.S. Patent No. 2.869 to JustuS. , No. 248. Moreover, TAPPI, v.

lume 62. No. 11. By Perrault published in 1979. The paper teaches the above points and is also published by TAPPI. 1984in Engineering Conference Jumpeter on page 347 of edings (1984 Journal of the Society of Engineering). The paper also relates to the above-mentioned points.

The foregoing patents and other disclosures discuss and accomplish the foregoing purposes. Although we have proposed a system to achieve this, these conventional methods and devices All suffered from unique control problems. Each of the above systems is Although it can be adjusted to operate in an acceptable manner under certain conditions, sometimes For changes necessitated by system malfunctions or changes in machine operating conditions. , both in direction and magnitude they cannot correspond.

As an example of the powerlessness of these conventional proposals, rPaper Machine Steam And Condensate SystemsJ (Figure 1) Conventional differential pressure control, as outlined in are doing. However, if the machine operating speed, steam pressure and condensate flow rate change, The required set point changes when Set point as shown in Figure 2 Because the change in pressure is a complex function of the variables listed above, machine operators often The set point will be set to the highest value required to meet a wide range of operating conditions. . Setting the differential pressure set point to the highest value in this way results in inefficient operation. bring about change. Moreover, such systems can also be affected by their ease of filling with water. be tormented. Additionally, if one of the siphons in the dryer's family floods, Proper control action should be to open the valve slightly in one attempt to drain water from the dryer. Despite this, the steam flow control valve is slightly closed due to its fixed differential pressure set point. It will probably end up.

Flow rate of U.S. Patent No. 2°869.248 to Justus shown in FIG. The control concept is to measure and control the amount of steam flow discharged with condensed water. The latter of the aforementioned problems is avoided. Then one of the dryers started filling up with water. If so, the control valve will open slightly. However, this system operating only at one fixed set point, which may not be appropriate for the operating conditions. .

In the aforementioned paper by Jumpeter, the system depicted in Figure 4 The microprocessor is used to adjust the set point based on the condensate flow from the separation tank. I am using sa. This control device is set continuously until the condensate flow is reduced. The set point is determined by decreasing the points.

However, this kind of approach is not recommended when driving near or near a stable operating point. This results in placing the dryer underneath. In many high-speed dryers, the dryer fills with water. Condensate flow will not be reduced until the differential pressure is lowered. Once something like this happened If this occurs, the dryer may be flooded even if the differential pressure is subsequently increased. It will not be possible to recover from this.

According to the present invention, what is the optimal differential pressure for stable and efficient operation of the dryer section? By recognizing the importance of parameters that indicate whether The aforementioned deficiencies of the various proposals are overcome. This method requires at least the operating speed of the machine and condensation rate. However, this method generally In addition, the set points should be adjusted in case of sheet damage (see sheet damage). Signals from detectors can also be used as input.

In addition to using the aforementioned parameters that describe the operating characteristics of this system as human values, , the proposed system provides a set point signal for the steam flow momentum reservoir. This para The meter ensures stable and efficient operation of the emissions system, as described below. It is important to make sure that The momentum of this steam flow is the product of the specific gravity of the steam flow and the steam flow velocity. It is proportional to the product of the power. This parameter is a differential pressure that is a mass flow rate or a volumetric flow rate. is provided as an output parameter instead of . Normal driving recognized by the present invention The optimum differential pressure for the It may be set somewhat higher than the pressure. For those occasional malfunctions, condensed water This includes increased flow, small differential pressure fluctuations, and increased operating speed. Actually, it is 0.14 It has been proven appropriate to apply a differential pressure of 1 bar.

The above method is similar to the system described in the aforementioned paper by Jumpeter. does not require frequent adjustment of set points or consequential responses. mentioned in the previous proposal. As shown in Figure 2, such control action often results in a minimum Guides operation to unstable areas near differential pressure. Rather, the system is shown in Figure 2. The experimentally measured relationships such as Use to adjust to a point. This system according to the invention has a steam outlet and low loss This is further enhanced by the use of a small radial siphon pump with a vortex flow meter. Ru. Regarding the enhancement of this effect, the requirement for low pressure drop also increases the size of the radial pipe. It is recognized that this can be achieved with less steam flow. Traditionally, when implementing It was customary to take advantage of the increased dimensions of radial pipes. However, Figure 2 As shown by the top curve, the sensitivity of the vapor flow to differential pressure increases and If the machine is operated at a stable differential pressure, the steam flow will generally be too high. Ru. That is, the minimum differential pressure increases by approximately Q, 14 bar. The present invention When the dimensions of the tube are reduced, the increase in minimum differential pressure is relatively small, while the evaporation It takes advantage of the fact that airflow sensitivity reduction is extremely significant. maximize momentum Approximately 0. ．． Controlling the differential pressure to a value higher than 14 bar and using a small radial pipe The use of There is no such thing. Therefore, the valves, condensers, and connecting pipes are small enough to be made smaller. The system continues to operate under stable conditions even when the differential pressure is low.

In accordance with the above aspects of the invention, the operation of the evacuation system is as described in the aforementioned Justus patent. Further stabilization is achieved by the use of a steam outlet as described in . The present invention is unstable Although the operation of the dryer is controlled away from the point, the use of a steam outlet is Guarantees that the dryer can recover even from major stem failures. For example, also If the differential pressure can be reduced to zero even for a short period of time, the tip of the siphon The ends will be submerged in condensate. With conventional differential pressure control, centrifugal The dryer may be full of water because the differential pressure set point is inadequate to remove condensate against the force. It will remain as it was. In the system by Jumpeter mentioned above, the difference is The pressure increases until the controller recognizes that its increase no longer results in an increase in condensate flow. It will be increased by the controller only until the However, Perrau The flow control system described by lt and U.S. Patent No. 2 to Justus. No. 869.248 states that the differential pressure must be increased to satisfy the steam flow set point only. I will try hard. However, in high-speed machines, it is difficult to save the remaining dryer from flooding. Although the differential pressure is insufficient, only some dryers in the dryer department are not flooded. The required flow rate will also be obtained. In the system according to the invention Similarly, the steam flow momentum set point is increased by increasing the differential pressure to obtain a flow rate of only the set point. Let's make it big. At the same time, the differential pressure required to drain a flooded dryer is Exhaust condensate with additional steam flow entering through a steam outlet located above the water level It is reduced by decreasing the specific gravity of. In addition, the system Therefore, automatically increase the set point. The combined effect of these three actions is It should provide a range of operational stability that was previously unattainable.

A third feature associated with the system according to the invention is the use of low loss instruments. So These low-loss meters are simple orifice flowmeters with a small restriction or May include a vortex meter. The former is used in this field and is based on the momentum of the steam flow. Gives a directly proportional pressure drop. The pressure drop is measured and used as an input to the controller. can be used. Although such orifice flow meters are commercially available, The resulting signal is often processed to provide a volumetric or gravimetric flow rate. Main departure By definition, the vortex shedding frequency frequency is rather used as a direct input to the control device. is proposed here. This frequency is also related to the momentum of the steam flow.

Such a device can be used as part of a control system without introducing pressure losses. Therefore, it is meaningful.

Another feature of the invention is the method of selecting a set point for the flow rate of the steam stream. Note By deep testing, we can establish a set of curves similar to those shown in Figure 2. . The set point for desired operation is determined by operating speed, dryer pressure, condensation rate, and size. First, place it at the position where the differential pressure is minimum for the given conditions with the dimensions of the phone. It can be determined by

As mentioned above, this value is approximately 0.14 bar to allow for small malfunctions during operation. The increment of is added. The steam flow rate corresponding to this differential pressure is then taken as the set point. It is used to calculate the momentum of the steam flow used.

These series of calculations can be performed for siphons of any shape. and then the value of that momentum set point is a function of the condensing load for each operating speed. Plotted as a number. The controller then uses the curve in Figure 2 to The measured condensing rate and operating speed are used as inputs to calculate the set point for the use Some typical curves of this type are shown in FIG. Sometimes like this The set point determined by the procedure is required for proper venting of non-condensable gases. It has been recognized that there may be cases where a steam volumetric flow rate less than the specified value is provided.

Therefore, a certain volumetric flow rate is established as a minimum limit, and this minimum limit is always satisfied. It is recommended that controls be used to check and ensure that good.

The main object of the present invention is to overcome the aforementioned deficiencies of prior art proposals and to improve web drying technology. for removing condensate from the rotating cylinder of a paper dryer, which can make a meaningful contribution to the technology. An object of the present invention is to provide a method and apparatus.

Another object of the invention is to directly control the kinetic flow rate of uncondensed steam. The differential pressure across the heated dryer is determined by the operating speed of the dryer and the condensate flow rate. The objective is to provide a method for indirectly controlling the

Another object of the invention is to keep the differential pressure between the input and output lines as low as possible. The operating speed should be kept low and at the same time prevent condensate from filling the dryer. The control signals generated by the sensor and the condensation rate sensor, respectively, The web dryer evaporators are compared by the controller to determine the proper ratio settings. It is an object of the present invention to provide a control device for controlling the differential pressure between the air inlet and outlet air lines.

Other objects of the invention will be apparent to those skilled in the art from the disclosure of the drawings, description and appended claims. will soon become obvious.

Summary of the invention The present invention controls the differential pressure between the steam input line and the output line of a web dryer. The invention relates to a method and a control device for.

This device selectively controls the flow of steam, condensed water, and non-condensable gases out of the dryer. A selectively controllable output valve located within the dryer output line to including. selectively controlling the operation of the output valve between its fully open setting and its fully open setting; Therefore, an output valve actuating means is arranged adjacent to the output valve. dryer rotation speed and generate a first control signal proportional to the sensed rotational speed of the dryer. For this purpose, an operating speed sensing means is located close to the dryer. layer of condensed water senses the rate at which the Condensation rate sensing means are provided for generating two control signals. The control means , respectively generated by the operating speed sensing means and the condensing speed sensing means. said output valve actuating means to selectively energize said output valve actuating means in response to a control signal from said output valve actuating means; connected to means. At the same time the differential pressure between the input and output lines is kept as low as possible. The maximum ratio setting of the output valve is set to prevent condensed water from filling the dryer. The signals from the operating speed sensing means and the condensing speed sensing means are used to determine the The control means are arranged for comparison.

In a more specific embodiment of the invention, the control device senses the pressure of the steam entering the dryer. and to generate a third control signal proportional to that sensed input line pressure. , including an input steam pressure sensing means disposed proximate said steam input line. Before Said third control signal from the input steam pressure sensing means further controls the optimum ratio setting of the output valve. is compared by said control means to determine.

The controller also includes a fourth control that senses web breakage and indicates such web breakage. sheet breakage sensing means placed in close proximity to the web to generate a signal; include. The fourth control signal from the breakage sensor is activated when such web breakage occurs. The optimal ratio settings of the output valves are further determined to prevent excessive waste of steam flow when are compared by the controller in such a way that the

In addition, the controller controls the output to sense the momentum of the steam flow exiting the dryer. including vapor flow sensing means disposed in the line. The steam flow sensing means A fifth control signal is generated that is proportional to the momentum of the flow. Such a fifth signal is To ensure stable and efficient operation of this system for discharging condensed water from compared by the control means to further determine the optimum ratio setting of the output valve. Ru.

The controller includes an operator placed in the output line to measure the momentum of the steam flow. Includes a refice flow meter means. The orifice flow meter is directly proportional to the momentum of the steam flow. It has a flow restriction passage to provide a pressure drop. Moreover, the momentum of the steam flow is A vapor flow sensing means is connected across said passageway for sensing.

In a particular embodiment of the invention, the control means is a microprocessor and the dryer includes radial siphon means located within the dryer. The aforementioned siphon The tube has an inner diameter of 2°29 cm or less.

As set forth below, specific embodiments of the invention are set forth in the accompanying drawings and the brief description. Although described, such presented embodiments of the invention merely refer to the apparatus and embodiments according to the invention. and are given only as an example of how the method may be implemented. Without departing from the spirit and scope of the invention as defined in the appended claims. It will be appreciated by those skilled in the art that numerous variations on this basic concept may be used. Will.

Moreover, although the invention has been described with particular application to the drying section of a papermaking machine, However, the present invention as defined by the appended claims may be modified from any suitable material. It is also intended for application in control systems for web drying of materials. will be recognized.

Brief description of the drawing FIG. 1 shows the paper machine Steam as described above. &　Condensate　H,P,Fishwick in SystemsJ 1 is a block diagram of a conventional proposal for conventional differential pressure control as outlined by .

FIG. 2 is a graph showing the differential pressure of the dryer versus steam flow rate.

FIG. 3 shows the above-mentioned U.S. Patent No. 2.869.248 to Justus. The concept of flow control is shown schematically in FIG.

Figure 4 shows Jumpeter's discussion on page 347 of the aforementioned TAPPI 1984. Figure 1 shows the prior disclosure by Jumpeter taught by the text.

Figure 5 illustrates a typical curve using a given siphon geometry and shows the flow of steam. It is a graph showing condensation speed with respect to momentum.

FIG. 6 is a schematic diagram of a control device according to the invention.

Figure 7 is similar to that shown in Figure 6, except that there is a backup manual operation. Overview of equipment coupled with conventional differential pressure and/or flow control systems for This is a schematic diagram.

Like reference numbers are used to refer to like parts throughout the various views in these drawings. has been done.

Below is a list of abbreviations used throughout the various figures in each drawing, along with their meanings: It is.

Figure 1 dpc...differential pressure controller pc...pressure controller Δp (steam) differential pressure dpt...Differential pressure converter pcv...pressure control valve dpcv...differential pressure control valve vb...vacuum bleed port vc...vacuum capacitor vcv...vacuum control valve lc...Liquid level controller vr...vacuum container vac...vacuum pump S...Separator lcv...liquid level control valve ep...Condensed water pump vp...vacuum pump Figure 3 frc...Flow rate recorder and controller prC...pressure recorder and controller dpt...Differential pressure transmitter pt...pressure transmitter Figure 4 pc...pressure controller dp...differential pressure Figure 7 p...(steam) pressure μp...Microprocessor (computer) PC...Pressure controller dp...(steam) differential pressure r/c...Recorder and controller sht bk... Seat damage Description of the preferred embodiment Figures 1, 3 and 4 are for controlling the discharge of condensed water outside the dryer enclosure. 1 shows various control devices according to the prior art.

Figure 2 is used to adjust the siphon system to its most stable and effective operating point. This shows the graph shown below.

Figure 5 shows the input of the measured condensing speed and operating speed to calculate the desired set point. FIG.

FIG. 6 shows one particular embodiment of the invention, which includes a steam input line or is a web dryer 16 indicated generally by steam supply line 12 and numeral 14. generally indicated at 10 for controlling the differential pressure between the output line of the The control device is shown. The apparatus 10 includes a flow of steam from the supply ladder 20 into the dryer 16. An input control valve 1 disposed in the steam input line 12 to selectively control the Contains 8. Selectively controlling the outflow of steam, condensed water, and incompressible gas from the dryer 16 A selectively controllable output valve 22 is provided in the output line 14 of the dryer 16 to control the It is located.

The operation of the input valve 18 is selected between its fully open and fully open settings according to the pressure controller 26. Input valve actuation means 24 is located adjacent to input valve 18 for selective control. Ru. To selectively control the operation of the output valve 22 between its fully open and fully open settings. , an output valve actuation means 28 is located adjacent the output valve 22. Dryer 16 times a first control signal that senses a rotational speed and is proportional to the sensed rotational speed of the dryer 16; The operating speed sensing means 30 is arranged close to the dryer 16 in order to generate Ru. sensing the rate of accumulation of the condensed water layer in the dryer 16; The condensate rate sensing means 32 is connected to the condensate pump for generating a proportional second control signal. 34 and the condensate return line 36.

A control device, generally designated 38, is provided between the input and output lines. The differential pressure of The control means 38 receives signals from the speed sensing means 30 and the condensing speed sensing means 32 so as to The speed sensing actuated in response to a control signal generated by means 30 and condensation rate sensing means 32; connected to the output valve actuation means 28 such that the means 28 can be selectively energized; .

As shown in FIG. 6, the control device 10 has an input valve 18 and a dryer 16 thereon. Sense the vapor pressure between the input valve 18 and the dryer 16 and compare it to the sensed pressure between the input valve 18 and the dryer 16 It also includes input vapor pressure sensing means 40 for generating an exemplary third control signal. input Said third control signal from the vapor pressure sensing means 40 is adapted to further optimize the ratio of the output valve 22. A comparison is made by the control means 38 to determine the settings.

In addition to the aforementioned sensing means, the control device 10 additionally includes sensing means for web breaks. a fourth control signal indicative of a break in the web; It also includes sheet breakage sensing means 42. The fourth control signal from the damage sensor 42 is Determining even more optimal ratio settings for the output valve 22 in case such web breakage occurs. The comparison is made by control means 38 to prevent excessive waste of steam flow.

The controller 10 is provided therewith for sensing the momentum of the steam flow exiting the dryer 16. It also includes a vapor flow sensing means 44 disposed between the separation tank 46 and the output valve 22. include. The vapor flow sensing means 44 generates a fifth control signal proportional to the momentum of the vapor flow. let This fifth signal is used to secure the system for removing condensed water from inside the dryer 16. In order to ensure constant and efficient operation, the output valve 22 is set to an even more optimal ratio. are compared by the control means 38 to determine.

FIG. 7 shows one alternative embodiment in which the controller filOA is 43A located in the output line 14A to measure the momentum of the steam flow The orifice flow meter means shown generally in FIG. Orifice flow meter 43 A includes a flow restriction passage 45A to create a pressure drop that is directly proportional to momentum. nothing. The steam flow sensing means 44A straddles the passage 45A to sense the momentum of the steam flow. It is connected.

In the presented embodiment of the invention, the control means 38 is a microprocessor; The dryer 16 is shown in FIG. 6 located within the dryer 16 to remove condensed water therefrom. It includes radial siphon means 48, shown schematically. The siphon means 48 includes two ．． Includes a siphon tube with an internal diameter of less than 29 cm.

As shown in FIG. 6, the control means 38, which may be a microprocessor, comprises: Machine speed manual power 50, condensate flow rate manual power 52, input line pressure manual power 54, and broken human power 5 6 and a steam flow input 58. The output of controller 38 is then Control the flow rate of the steam flow which will be sensed again for feedback control Therefore, it has at least one set point. The control means 38 includes a condensate flow rate control unit 52 and Obtain machine speed input 50. Additionally, the controller may have a vapor pressure input 54. stomach. Moreover, the steam flow control set point is a value that is proportional to the momentum of the steam flow. its settings The value corresponds to a minimum differential pressure of 0.07 bar to 0.21 bar and 0.1 Preferably it is 4 bar. This system 10 is installed in the siphon of the dryer. a radial siphon tube 48 having an inner diameter of less than 2.29 cm; use.

In the presented embodiment of the invention, the flow ffi sensing instrument 44 is a vortex instrument; The system may be used for condensable vapors other than water vapor. The control means output 62 is Thermal compressor valves in the conventional heat compressor system of valves and Figure 7 and may provide set points for both. The control means include a suitable volume of non-condensable gas. It may be set to maintain a certain volumetric flow rate as a minimum value that can guarantee the discharge of gas.

The set point value for steam flow momentum decreases with increasing condensate flow rate and mechanical operation. It will increase as the rolling speed increases.

As shown in Figure 7, this system includes a conventional A differential pressure control system and/or a flow control system may be combined.

In order to operate this system normally with an appropriate differential pressure, it is necessary to Must be set somewhat higher than the minimum differential pressure to accommodate occasional malfunctions. . Experience has shown that an applied differential pressure of approximately 0.14 bar is suitable. ing. The operation of this system is based on the small radial siphon tube and vaporizer as described above. This is further enhanced by the use of air outlets and low-loss fan flow meters. Low loss under pressure Loss can be achieved by increasing the size of the radial vibrator or by reducing the steam flow. can be done. The present invention shows that when the dimensions of the radial vibe are reduced, the increase in the minimum differential pressure is The reduction in sensitivity in vapor flow, on the other hand, is said to be relatively small and quite significant. Take advantage of the fact that to a value that can raise the differential pressure by approximately 0.14 bar above its minimum value. By controlling the momentum and also by using a small radial vibrator Therefore, the steam flow does not change significantly during malfunctions during machine operation. So As a result, the valves, capacitors, and connecting valves are smaller and smaller for customization. Therefore, this system continues to operate in a stable state even when the differential pressure is small.

The use of a steam outlet allows the dryer to recover from even major system failures. guaranteed. To increase the set point flow rate, the set point of steam flow momentum is similarly automatically increases the set point due to a decrease in system condensate flow. Good morning. In addition, the differential pressure required to discharge from the flooded dryer is at the same time , emissions due to an additional steam flow entering from a steam outlet located above the condensate layer. reduced by increased susceptibility of condensate. Synthesis of these three effects The effect should be to provide a range of operational stability that was hitherto unattainable.

By providing a simple orifice flow meter with a small restriction on the vortex meter, the pressure The force drop can be measured and used as an input to the controller.

Set points for desired operation are determined by operating speed, dryer pressure, condensation rate, and siphon dimensions. is determined by first placing it at the point of minimum differential pressure for the given conditions. It can be done. Allow some increment to this value to accommodate minor malfunctions during operation. Usually 0.14 bar is added. The steam flow rate corresponding to this differential pressure is then set. The point is used to calculate the momentum of the steam flow.

The present invention uses each of the aforementioned parameters as input to a controller that sequentially calculates the appropriate set point. This system uses a configuration similar to that described in the proposals of the prior art. There is no need for frequent adjustment of fixed points or monitoring of the resulting response.

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Claims (1)

[Claims] In order to selectively control the flow of steam, condensed water, and non-condensable gas to the outside of the dryer, a selectively controllable output valve located in the output line of the dryer; said output valve to selectively control the operation of the valve between its fully open and fully closed settings. an output valve operating means disposed adjacent to the dryer; said for generating a first control signal proportional to said sensed rotational speed of said dryer; Operating speed sensing means located close to the dryer and detecting condensed water in the dryer. sensing the rate at which the layer accumulates and generating a second control signal proportional to the sensed rate of accumulation; a condensation rate sensing means for producing a differential pressure between the input line and said output line; is kept as low as possible while preventing the condensate from filling the dryer. the signal obtained from the continuous rotation speed sensing means and the condensation speed sensing means so that The control means compares the operating speed sensing means and the condensation speed sensing means. selectively energizing the actuating means in response to the control signals respectively generated by said control means operably connected to said output actuating means in order to for controlling the differential pressure between the steam input line and the output line of the web dryer, including Control device.