CN112747461A

CN112747461A - Intelligent control heating method for steam boiler

Info

Publication number: CN112747461A
Application number: CN201911041887.8A
Authority: CN
Inventors: 王逸隆
Original assignee: Qingdao University of Science and Technology
Current assignee: Qingdao University of Science and Technology
Priority date: 2019-10-29
Filing date: 2019-10-29
Publication date: 2021-05-04

Abstract

The invention provides an intelligent control heating method for a steam boiler, wherein an electric heating device is divided into n groups, and each group is alternately not heated; the periodic frequent vibration of the elastic coil is realized. The boiler designed by the invention can improve the heating efficiency and ensure the uniform integral heating, thereby realizing good descaling and heating effects.

Description

Intelligent control heating method for steam boiler

Technical Field

The invention relates to steam generation equipment, in particular to an intermittent vibration descaling boiler.

Background

Boilers are mechanical devices that use the heat energy of fuel or other energy sources to heat water into steam. The steam generator has wide application field and is widely applied to places such as clothing factories, dry cleaning shops, restaurants, bunkers, canteens, restaurants, factories and mines, bean product factories and the like. In applicant's prior application, a new coil type electric heating coil, such as CN106123306A, was developed and studied to vibrate the elastic tube bundle due to the expansion of the fluid therein caused by heating, thereby achieving heating and descaling effects.

However, in applications where it is found that continuous heating of the electric heater results in fluid stability of the internal electric heating means, i.e. the fluid is not flowing or is flowing very little, or the flow is stable, the vibration performance of the coil is greatly reduced, and thus the efficiency of the coil for descaling and heating is affected.

In the prior application, the heating of a single electric heating device is researched, but the problem of uneven overall heating exists, for example, the heating power may have different heights along with the time.

Disclosure of Invention

The invention provides a boiler with a novel heating device for alternately heating, aiming at the defects of the boiler in the prior art. The boiler can improve the heating efficiency and ensure the integral heating to be uniform, thereby realizing good descaling and heating effects.

In order to achieve the purpose, the invention adopts the following technical scheme:

a steam boiler intelligent control heating method comprises an electric heating device and a steam drum, wherein the electric heating device is arranged in the steam drum, the steam drum comprises a water inlet pipe and a steam outlet, the electric heating device comprises a first pipe box, a second pipe box and a coil pipe, the coil pipe is communicated with the first pipe box and the second pipe box to form heating fluid closed circulation, and an electric heater is arranged in the first pipe box; filling phase-change fluid in the first channel; the number of the coil pipes is one or more, each coil pipe comprises a plurality of arc-shaped pipe bundles, the central lines of the arc-shaped pipe bundles are arcs taking the first pipe box as a concentric circle, and the end parts of the adjacent pipe bundles are communicated, so that the end parts of the pipe bundles form free ends of the pipe bundles; the electric heating device is characterized in that the electric heating device is divided into n groups, and each group is alternately not heated;

the heating power P of each electric heating device of 1 group changes regularly during one period time T as follows:

in a half period of 0-T/2, P ═ n, where n is a constant number in watts (W), i.e., the heating power remains constant;

in a half period of T/2-T, P is 0, namely the electric heating device does not heat;

the change rule of the heating power P of the other n-1 groups of electric heating devices is as follows:

in the half period of 0-T/2, P is 0, namely the electric heater does not heat;

and in the half period of T/2-T, P is equal to n, wherein n is a constant value and has the unit of watt (W), namely the heating power is kept constant.

Preferably, the steam drum is circular in cross section, the electric heating devices are multiple, one of the electric heating devices is arranged in the center of the steam drum and becomes a central electric heating device, and the other electric heating devices are distributed around the center of the steam drum and become peripheral electric heating devices.

The invention has the following advantages:

1. according to the invention, the group of electric heating devices are arranged to alternately perform no heating, so that the heating efficiency is improved, the integral heating uniformity is ensured, and the good descaling and heating effects are realized.

2. The invention designs a layout of an electric heating device with a novel structure in a steam drum, which can further improve the heating efficiency.

3. The electric heating device provided by the invention intermittently heats in a period, and can realize periodic frequent vibration of the elastic coil, so that good descaling and heating effects are realized.

4. The invention increases the heating power of the coil pipe periodically and continuously and reduces the heating power, so that the heated fluid can generate the volume which is continuously in a changing state after being heated, and the free end of the coil pipe is induced to generate vibration, thereby strengthening heat transfer.

5. The invention optimizes the optimal relationship of the parameters of the coil pipe through a large amount of experiments and numerical simulation, thereby realizing the optimal heating efficiency.

Description of the drawings:

fig. 1 is a top view of an electric heating apparatus of the present invention.

Fig. 2 is a front view of the electric heating apparatus.

Fig. 3 is a coordinate diagram of intermittent heating of the electric heating device.

Fig. 4 is a graph of the coordinates of the periodic increase and decrease in heating power of the electric heating device.

Fig. 5 is a schematic coordinate diagram of another embodiment of periodically increasing and decreasing heating power of an electric heating device.

Fig. 6 is a coordinate diagram of the linear change of the heating power of the electric heating device.

Fig. 7 is a schematic layout of an electric heating device arranged in a circular steam drum.

Fig. 8 is a schematic view of the coil configuration.

Fig. 9 is a schematic view of a drum structure.

In the figure: 1. coil pipe, 2, first pipe box, 3, free end, 4, free end, 5, water inlet pipe, 6, steam outlet, 7, free end, 8, second pipe box, 9, connecting point, 10, electric heating device, 11, steam pocket, 12 pipe bundle, 13 electric heater

Detailed Description

A boiler comprising an electric heating device 10, a steam drum 11, said electric heating device 10 being arranged in the steam drum 11, said steam drum 11 comprising a water inlet tube 5 and a steam outlet 6. The steam outlet 6 is arranged at the upper part of the steam drum.

Preferably, the steam drum is of cylindrical construction.

Fig. 1 shows a top view of an electric heating apparatus 10, as shown in fig. 1, the electric heating apparatus 10 includes a first pipe box 2, a second pipe box 8 and a coil 1, the coil 1 is communicated with the first pipe box 2 and the second pipe box 8, a fluid circulates in the first pipe box 2, the second pipe box 8 and the coil 1 in a closed manner, an electric heater 13 is arranged in the electric heating apparatus 10, the electric heater 13 is used for heating the fluid in the electric heating apparatus 10, and then the water in the steam drum is heated by the heated fluid.

As shown in fig. 1-2, an electric heater 13 is disposed in the first header tank 2; the first channel box 2 is filled with phase-change fluid; the number of the coil pipes 1 is one or more, each coil pipe 1 comprises a plurality of circular arc-shaped pipe bundles 12, the central lines of the circular arc-shaped pipe bundles 12 are circular arcs taking the first pipe box 2 as a concentric circle, the end parts of the adjacent pipe bundles 12 are communicated, and fluid forms serial flow between the first pipe box 2 and the second pipe box 8, so that the end parts of the pipe bundles form free ends 3 and 4 of the pipe bundles; the fluid is phase-change fluid, vapor-liquid phase-change liquid, the electric heating device is in data connection with the controller, and the controller controls the heating power of the electric heating device to periodically change along with the change of time.

Preferably, the first and

second headers

2 and 8 are provided along a height direction.

It has been found in research and practice that continuous power-stable heating of the electric heater results in a stable fluid formation of the internal electric heating means, i.e. the fluid is not flowing or has little fluidity, or the flow is stable, resulting in a greatly reduced vibrational performance of the coil 1, thereby affecting the efficiency of descaling and heating of the coil 1. There is therefore a need for an improvement to the electrical heating coil described above as follows.

Preferably, the heating power is a batch type heating method.

The electric heating devices are divided into two groups, and the two groups of electric heating devices heat alternately, so that the periodic frequent vibration of the elastic coil is realized.

As shown in fig. 3, the heating power P of each electric heating device of the first group varies regularly during one cycle time T as follows:

and P is 0 in the half period of T/2-T. I.e. the electric heating means do not heat.

The heating power P of the second group of single electric heating devices is changed according to the following rule:

in the half period of 0-T/2, P is 0. I.e. the electric heating means do not heat.

In a half period of T/2T, P is equal to n, wherein n is a constant value and has the unit of watt (W), namely the heating power is kept constant;

t is 50-80 minutes, wherein 4000W < n < 5000W.

Through the heating with the time variability, the fluid can be frequently evaporated, expanded and contracted in the elastic tube bundle, so that the vibration of the elastic tube bundle is continuously driven, and the heating efficiency and the descaling operation can be further realized.

By dividing the electric heating devices into two groups, the heating power and the heating efficiency of the electric heating devices can be improved as a whole.

Preferably, the number of electrical heating means in each group is the same.

Further preferably, the electric heating devices are divided into n groups, and each group is alternately not heated. During a period T, n-1 groups are heated, and 1 group is not heated.

That is, within one cycle time T, the heating power P of each electric heating device of 1 group changes regularly as follows:

in the half period of 0-T/2, P is 0. I.e. the electric heater does not heat.

In a half period of T/2-T, P ═ n, where n is a constant number in watts (W), i.e., the heating power remains constant;

preferably, the heating power of the single electric heating device is 4000W < n < 5000W

Preferably, the number of the electric heating devices in each group is the same.

Preferably, the electric heating devices are arranged into 2 groups, each electric heating device is provided with a plurality of electric heating devices, each electric heating device is independently controlled, and the number of the first group and the second group of electric heating devices which are started is periodically changed along with the change of time.

Preferably, when the operation is started, the first group of electric heating devices are all closed, the second group of electric heating devices are all started, and each group of electric heating devices is n, in a period T, one electric heating device in the first group of electric heating devices is started at intervals of T/2n until the heating devices are all started at the time of T/2n, and then one electric heating device is closed at intervals of T/2n until the heating devices are all closed at the time of T. In the second group of electric heating devices, one electric heating device is closed every T/2n until the heating devices are completely closed at T/2n, and then one electric heating device is opened every T/2n until the heating devices are completely opened at T.

Preferably, each electric heating device has the same heating power. The relationship diagram is shown in fig. 4.

By turning on and off the two groups of electric heating devices, the total heating power can be guaranteed to be the same.

Preferably, the period is 50 to 300 minutes, preferably 50 to 80 minutes.

Preferably, the pipe diameter of the first pipe box 2 is smaller than that of the second pipe box 8, and the pipe diameter of the first pipe box 2 is 0.5-0.8 times of that of the second pipe box 8. Through the pipe diameter change of first pipe case and second pipe case, can guarantee that the fluid carries out the phase transition and in the internal time of first box short, get into the coil pipe fast, fully get into the heat transfer of second box.

Preferably, the connection position 9 of the coil pipe at the first header is lower than the connection position of the second header and the coil pipe. This ensures that steam can rapidly enter the second header upwards.

Preferably, the first and second headers are provided with return lines at their bottoms to ensure that condensed fluid in the second header can enter the first line.

Preferably, the first and second headers are arranged in a height direction, the coil pipe is provided in plural numbers in the height direction of the first header, and a pipe diameter of the coil pipe is gradually reduced from top to bottom.

Preferably, the pipe diameter of the coil pipe is gradually decreased and gradually increased along the direction from the top to the bottom of the first pipe box.

The pipe diameter range through the coil pipe increases, can guarantee that more steam passes through upper portion and gets into the second box, guarantees that the distribution of steam is even in all coil pipes, further reinforces the heat transfer effect for whole vibration effect is even, and the heat transfer effect increases, further improves heat transfer effect and scale removal effect. Experiments show that better heat exchange effect and descaling effect can be achieved by adopting the structural design.

Preferably, the plurality of coils are arranged along the height direction of the first tube box, and the distance between the adjacent coils is increased from the top to the bottom.

Preferably, the distance between the coils increases along the height direction of the first header.

The interval range through the coil pipe increases, can guarantee that more steam passes through upper portion and gets into the second box, guarantees that the distribution of steam is even in all coil pipes, further reinforces the heat transfer effect for whole vibration effect is even, and the heat transfer effect increases, further improves heat transfer effect and scale removal effect. Experiments show that better heat exchange effect and descaling effect can be achieved by adopting the structural design.

Preferably, as shown in fig. 7, the steam drum is a drum with a circular cross section, and a plurality of electric heating devices are arranged in the steam drum.

Preferably, as shown in fig. 7, one of the plurality of electric heating devices disposed in the steam drum is disposed at the center of the steam drum to become a central electric heating device, and the others are distributed around the center of the steam drum to become peripheral electric heating devices. Through the structural design, the fluid in the steam pocket can fully achieve the vibration purpose, and the heat exchange effect is improved.

Preferably, the heating power of the single peripheral electric heating means is smaller than the heating power of the central electric heating means. Through the design, the center reaches higher vibration frequency to form a central vibration source, so that the periphery is influenced, and better heat transfer enhancement and descaling effects are achieved.

Preferably, on the same horizontal heat exchange section, the fluid needs to achieve uniform vibration, and uneven heat exchange distribution is avoided. It is therefore necessary to distribute the amount of heating power among the different electric heating devices reasonably. Experiments show that the heating power ratio of the central electric heating device to the peripheral tube bundle electric heating device is related to two key factors, wherein one of the two key factors is the distance between the peripheral electric heating device and the center of the steam drum (namely the distance between the circle center of the peripheral electric heating device and the circle center of the central electric heating device) and the diameter of the steam drum. Therefore, the invention optimizes the optimal proportional distribution of the pulsating flow according to a large number of numerical simulations and experiments.

Preferably, the radius of the inner wall of the steam drum is B, the center of the central electric heating device is arranged at the center of the circular section of the steam drum, the distance from the center of the peripheral electric heating device to the center of the circular section of the steam drum is S, the centers of adjacent peripheral electric heating devices are respectively connected with the center of the circular section, the included angle formed by the two connecting lines is a, the heating power of the peripheral electric heating device is W2, and the heating power of a single central electric heating device is W1, so that the following requirements are met:

W1/W2 ═ a-B ═ Ln (B/S); ln is a logarithmic function;

a, b are coefficients, wherein 1.9819 < a < 1.9823, 0.5258 < b < 0.5264;

1.25＜B/S＜2.1；

1.6＜W1/W2＜1.9。

wherein 35 DEG < A < 80 deg.

Preferably, the number of the four-side distribution is odd.

Preferably, the electric heating devices are divided into two groups, and the number of the electric heating devices in each group is the same.

Preferably, R is 1600-2400 mm, preferably 2000 mm; l is 1200-2000 mm, preferably 1700 mm; the diameter of the heat exchange tube is 12-20 mm, preferably 16 mm; the outermost diameter of the pulsating coil is 300-. The diameter of the riser is 100-116 mm, preferably 108 mm, the height of the riser is 1.82.2 m, preferably 2 m, and the spacing between adjacent pulse tubes is 65-100 mm. Preferably around 80 mm.

The total heating power is preferably 6000-14000W, and more preferably 7500W.

More preferably, a is 1.9821 and b is 0.5261.

The steam outlet is arranged in the middle of the upper wall of the steam drum.

Preferably, the box body has a circular cross section, and is provided with a plurality of electric heating devices, wherein one electric heating device is arranged at the center of the circular cross section and the other electric heating devices are distributed around the center of the circular cross section.

The coils 1 are in one or more groups, each group of coils 1 comprises a plurality of circular arc-shaped tube bundles 12, the central lines of the circular arc-shaped tube bundles 12 are circular arcs of concentric circles, and the ends of the adjacent tube bundles 12 are communicated, so that the ends of the coils 1 form tube bundle free ends 3, 4, such as the free ends 3, 4 in fig. 2.

Preferably, the heating fluid is a vapor-liquid phase-change fluid.

Preferably, the first header 2, the second header 8, and the coil 1 are all of a circular tube structure.

Preferably, the tube bundle of the coil 1 is an elastic tube bundle.

The heat exchange coefficient can be further improved by arranging the tube bundle of the coil 1 with an elastic tube bundle.

Preferably, the concentric circles are circles centered on the center of the first header 2. I.e. the tube bundle 12 of the coil 1 is arranged around the centre line of the first tube box 2.

As shown in fig. 4, the tube bundle 12 is not a complete circle, but rather leaves a mouth, thereby forming the free end of the tube bundle. The angle of the arc of the mouth part is 65-85 degrees, namely the sum of the included angles b and c in figure 8 is 65-85 degrees.

Preferably, the ends of the tube bundle on the same side are aligned in the same plane, with the extension of the ends (or the plane in which the ends lie) passing through the median line of the first tube box 2.

Further preferably, the electric heater 13 is an electric heating rod.

Preferably, the first end of the inner tube bundle of the coil 1 is connected to the first tube box 2, the second end is connected to one end of the adjacent outer tube bundle, one end of the outermost tube bundle of the coil 1 is connected to the second tube box 8, and the ends of the adjacent tube bundles are connected to form a serial structure.

The plane in which the first end is located forms an angle c of 40-50 degrees with the plane in which the centre lines of the first and

second headers

2, 8 are located.

The plane of the second end forms an angle b of 25-35 degrees with the plane of the centre lines of the first and

second headers

2, 8.

Through the design of the preferable included angle, the vibration of the free end is optimal, and therefore the heating efficiency is optimal.

As shown in fig. 8, there are 4 tube bundles of coil 1, with tube bundles A, B, C, D in communication. Of course, the number is not limited to four, and a plurality of the connecting structures are provided as required, and the specific connecting structure is the same as that in fig. 8.

The number of the coil pipes 1 is multiple, and the plurality of coil pipes 1 are respectively and independently connected with the first pipe box 2 and the second pipe box 8, that is, the plurality of coil pipes 1 are in a parallel structure.

Although the present invention has been described with reference to the preferred embodiments, it is not limited thereto. Various changes and modifications may be effected therein by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A steam boiler intelligent control heating method comprises an electric heating device and a steam drum, wherein the electric heating device is arranged in the steam drum, the steam drum comprises a water inlet pipe and a steam outlet, the electric heating device comprises a first pipe box, a second pipe box and a coil pipe, the coil pipe is communicated with the first pipe box and the second pipe box to form heating fluid closed circulation, and an electric heater is arranged in the first pipe box; filling phase-change fluid in the first channel; the number of the coil pipes is one or more, each coil pipe comprises a plurality of arc-shaped pipe bundles, the central lines of the arc-shaped pipe bundles are arcs taking the first pipe box as a concentric circle, and the end parts of the adjacent pipe bundles are communicated, so that the end parts of the pipe bundles form free ends of the pipe bundles; the electric heating device is characterized in that the electric heating device is divided into n groups, and each group is alternately not heated; the periodic frequent vibration of the elastic coil is realized;

the method comprises the following steps:

in the half period of 0-T/2, P is 0, namely the electric heater does not heat;

2. The boiler according to claim 1, wherein the steam drum is circular in cross-section and the electric heating means are plural, one of the electric heating means being arranged in the center of the steam drum as a central electric heating means and the other electric heating means being distributed around the center of the steam drum as peripheral electric heating means.

3. A boiler comprises an electric heating device and a steam drum, wherein the electric heating device is arranged in the steam drum, the steam drum comprises a water inlet pipe and a steam outlet, the electric heating device comprises a first pipe box, a second pipe box and a coil pipe, the coil pipe is communicated with the first pipe box and the second pipe box to form closed circulation of heating fluid, and an electric heater is arranged in the first pipe box; the first channel is filled with a phase-change fluid.