CN85101357A - The control method of heater of coal-burning boiler - Google Patents

Abstract

The present invention relates to a kind of control method that is used for air heater in the coal-burning boiler system.This system comprises that the heating primary air is to dry coal dust and it is imported the heater of boiler, and the waste gas that the use boiler is discharged is as thermal source, mode with heat exchange heats time air-flow with combusting coal fines, above-mentioned air heater comprises primary air heater and time flow type calorifier that is installed in parallel, by air exhauster waste gas is sent into two air heaters from boiler, its exhaust gas flow is controlled respectively by air door separately, the primary air of heating and cold air mix to obtain the proper temperature of oven dry and transportation coal dust, the air door opening of absorption cold air will keep the low value near 0, keep the cold air flow low, simultaneously, the air door of control primary air heater obtains above-mentioned suitable temperature.

Description

The control method of heater of coal-burning boiler

What the present invention relates to is a kind of control method of coal-burning boiler air heater, particularly controls the method for the air heater of coal-fired powder boiler, and purpose is to improve device efficiency.

It is in common knowledge that coal-burning boiler just becomes people in the past, and entered practical existing very long history., owing to much all have a firing machine in these boilers, the burner that needs the combustion ash to handle be difficult to control, or the like, the use of coal-burning boiler has just been abandoned, and in the past in some times, replacing, to become what generally use be oil burning boiler.But under the oil shock worldwide, coal-burning boiler has caused people's attention in recent years again.Therefore, the boiler of much having planned, having designed and built now all is a firing coal dust.

Pulverized coal firing boiler is a kind of like this boiler: the coal dust in the burning of the burner hearth of pulverized coal firing boiler is the coal dust of pulverizing through pulverizer in advance.So it has characteristics, there are not coal ash and control easily.What pulverized coal firing boiler was different with other fire coal or oil burning boiler is exactly except using combustion air, and it also will deliver to boiler to coal dust from pulverizer with the air stream of delivering coal.So, their feeders quantitatively just have two, an air supply system that provides the air stream of delivering coal, be commonly referred to as " primary air air supply system " (the air-flow here is called as " primary air "), the air supply system that another provides combustion air is commonly referred to as " inferior air-flow air supply system " (the air-flow here is called as " inferior air-flow ").By the way, thermal current after the heating and normal pressure air-flow are the supply boilers.Reason is as follows: supply with boiler as cold airflow being used as combustion gas, will can't carry out efficient burning because of too cool in the stove.In addition, in order to use the primary air pulverized coal conveying, just the coal dust water content must be reduced to zero in the hope of efficient burning.Hot blast is to be produced by the air heater of installing for the heat exchange that realizes between atmospheric air and the boiler waste gas.

United States Patent (USP) 3,246,635 disclose a kind of pulverized coal firing boiler that has air supply system, as shown in Figure 5, import pulverizers 25 by air flow regulating damper 26 and 34 respectively at the air (cold air) of the first order with at partial air (hot gas) in the air heater 9., and regulate with the method for controlling cold airflow damper and thermal current damper 26 and 34 opening amounts in case temperature is too high sets off an explosion by temperature monitoring 60 these machine internal temperatures of monitoring according to predetermined temperature.

According to known example, the temperature in the pulverizer is controlled on the predetermined value with the method for regulating main thermal current and main cold airflow mixed proportion.But the coal water content has very big difference because of coal kind difference, when with the high coal of water content, pulverizes built-in temperature and reduces, and like this, the operation operation just is in main thermal current damper all opens, and main cold airflow damper then is in complete closing state.In this case, in order to solve the problem of high-moisture coal as early as possible, the air heater volume just must be enough big, to improve main hot stream temperature.On the other hand, when using the low water content coal, the operation operation just is in main cold airflow damper almost all opens, and main thermal current damper then is in complete closing state.In this case, it is interior temperature required to be cooled to adapt to pulverizer again again after the heating of air heater via.So the heat exchange ratio in the heater is just very low and uneconomical.

Consider that the problems referred to above the objective of the invention is to provide for coal-burning type boiler the method for a control air heater, just can obtain required primary air temperature and realize high heat exchange rate thereby can accomplish not enlarge heater power.

The method for controlling heater that provided of invention is exactly that the cold airflow damper that keeps sucking cold air almost completely cuts out and limits cold air flow, at this moment regulates the heater air flow regulating damper again to obtain to mix the necessary temp of back primary air.

Like this, the cold air flow of suction reduces to minimum degree and the exhaust gas flow that enters heater has increased.So, just can obtain required primary air temperature without enlarging heater power.In addition, rate of heat exchange also can improve in the heater.Also can effectively utilize the heat in the waste gas in other words.

Shown in Figure 1 is to be applicable to associated especially part in air heater system of the present invention and the coal-fired powder boiler; The embodiment that shown in Figure 2 is according to air heater control method proposed by the invention just regulates temperature in the pulverizer with the control air flow regulating damper; Fig. 3 is a curve map, introduce to adopt obtainable invention effect behind the schematic diagram shown in Figure 2; That shown in Figure 4 is another embodiment of invention; Fig. 5 then is the chart that expression has the I/O of function generator 110 features shown in Figure 4.

At first be to describe one one according to Fig. 1 to be applicable to coal-fired powder boiler of the present invention below.A boiler 3 that is used for heat power station is arranged in Fig. 1, and its required hot gas all improves its efficiency of combustion by waste gas (gas after the burning) heating that air heater 1 and 2 uses boiler 3 to discharge.Need pre-heated air to have two kinds, a kind of is coal, as coal dust, is transported to the primary air of boiler 3, and another kind is the inferior air-flow that is used to burn coal.Primary air and time air-flow all depended on pressure pressure fan 4 pressurize respectively from the outside and send into heater 1 and 2.After coming out from forced fan 4, primary air A ₁Just with time air current A ₂Shunting is quickened to enter primary air heater 1(hereinafter to be referred as " main flow AH " by primary air pressure fan 5), be heated as heated air stream A1h at this by waste gas.Then, primary air A1h mixes by hot gas damper 6 and cold airflow A1C.Cold airflow A1C through cold air damper 7 from outer suction.Mixed airflow through mixing hot blast A1h and cold wind A1C has just had a specific temperature and has passed through pulverizer 8.Like this, it just can dry coal dust, simultaneously also with its input boiler 3.At this moment mixed airflow temperature, just primary air is by temperature monitoring 11 monitorings, by control main flow AH ₁Air flow regulating damper 17 keep its specific temperature.Cold wind temperature, the temperature of main flow AH outlet, the temperature of pulverizer outlet are respectively by temperature monitoring 10,9 and 12 monitorings.For the primary air that makes the pulverizer input fully plays the effect that coal dust is heated in oven dry, the gateway temperature of pulverizer 8 must be a definite temperature.Such as routinely, in order to keep the specified temp of pulverizer 8 outlets, the mode of taking to control is one that closes in hot gas damper 6 and the cold air damper 7, opens another.In the air-flow of sending by forced fan 4, inferior air current A ₂At inferior flow type calorifier 2(hereinafter to be referred as " inferior stream AH ") in by waste gas heating and input boiler 3.

On the other hand, the waste gas G that is discharged by boiler 3 is divided into two strands through electric dust suction gas 13.One air-flow G ₁Be admitted to " main flow AH ₁".Waste gas G ₁Behind the heating primary air, extract out by air exhauster 15, discharge from chimney 16 by air flow regulating damper 17.

Be divided into another strand air-flow in the waste gas of two strands of air-flows, G ₂Send into " inferior stream AH ₂" heating time air current A ₂Then, this strand air-flow passes air flow regulating damper 14, is extracted out by air exhauster 15, discharges from chimney 16 by the equipment of desulfurizer 18 and so on.In a word, two or more pulverizer system will be installed in parallel.With reference now to Fig. 2, an embodiment of this invention is described.Symbol A represents the control system of air flow regulating damper 14 and 17 among the figure.Symbol B represents the control system of air flow regulating damper 6 and 7.In addition, reference number 6 expression thermal current dampers, reference number 7 expression cold airflow dampers, on the other hand, reference number 17 expression time air flow regulating dampers, reference number 14 expression time air flow regulating dampers.

The control system of air flow regulating damper now is described, the delivery outlet temperature of pulverizer 8 is by temperature monitoring 12 monitorings among Fig. 1, and the temperature difference between delivery outlet temperature and constant temperature device 24 predetermined temperatures is calculated by subtrahend device 25.Proportional integral instrument 26 is advanced in the difference input that calculates, and just becomes to start the command signal of air flow regulating damper 6 and 7 through special arithmetical operation at this.When the installation of cold airflow damper 7 and thermal current damper 6 should be able to make Dang Yimen open, another door was just closed.For this reason, the command signal of being sent by proportional integral instrument 26 just is transformed into command signal reverse open command once by function generator 27, imports thermal current damper 6 again.43 and 44 is auto-manual selectors, can select for use proportional integral instrument 26 to send instruction and also can select the manual command that does not mark among the figure for use.

According to this air flow regulating damper control system, control operation is such, and when pulverizer delivery outlet temperature was higher than the temperature that incubator reserves in advance, cold airflow damper 7 was opened, and thermal current damper 6 cuts out.And when the pulverizer delivery outlet was lower than former fixed temperature, thermal current damper 6 was opened, and cold airflow damper 7 cuts out.Because atmospheric air is cooled again after through air heater 1 heating, the result has reduced heat energy efficiency but in the previous case.And under latter event, when the coal water content is high, need to enlarge the specification of heater again inevitably.

In view of the foregoing, purpose of the present invention will as far as possible often be opened air flow regulating damper 6 and 7 exactly, thereby regulates the temperature of air flow regulating damper from control pulverizer 8 delivery outlets.For this reason, the signal that cold airflow damper 7 is opened in order is imported into subtrahend device 31, subtracted by enabling signal predetermined in the setting device 32 that opens the door, this enabling signal and air flow regulating damper 7 be closing state corresponding (such as extent of opening is approximately 10%) almost.Like this, just obtain a difference, through the specific computing of proportional integral instrument 33, operation result is input to control system A again, and primary air damper 17 and inferior air flow regulating damper 14 are opened in system's control thus.Illustrate now and control the mode that primary air damper 17 is opened.What proportional integral instrument 33 was exported is a signal, and expression is exported the desired value that will reach by the exhaust outlet temperature monitoring 9 of primary air heater.In other words, when cold airflow damper 7 is opened when big, this desired value will diminish (just, desired value will become the value that primary air heater exhaust outlet temperature is reduced).The difference of the output valve of the output valve of proportional integral instrument 33 and temperature monitoring 9 again by proportional integral instrument 23 calculation process, becomes the instruction that starts primary air damper 17 after being calculated by subtrahend device 22.Notice that here 41 is auto-manual selectors.Because the extent of opening of primary air damper 17 is controlled by aforesaid way, so when the output valve of proportional integral instrument 33 during greater than the output valve of temperature monitoring 9, the opening of primary air damper 17 will increase, thereby cause primary air heater exhaust outlet temperature rising (that is: the output valve of temperature monitoring 9).In addition, when the output valve of proportional integral instrument 33 during less than the output valve of temperature monitoring 9, the opening of primary air damper 17 just diminishes, and causes that primary air heater delivery outlet temperature reduces.The result, when the temperature (output valve of temperature monitoring 12) of pulverizer 8 exhaust outlets is higher than the output valve of temperature setting device 24 and the therefore more substantial cold air of needs, and the opening of cold airflow damper 7 is greater than 10% o'clock, the output valve of proportional integral instrument 33 just is less than the output valve of temperature monitoring 9, thereby reduces the opening of primary air damper 17.As a result, the output temperature of primary air heater reduces, and therefore the opening of cold airflow damper 7 has also reduced.On the contrary, when the more substantial hot blast of needs and the opening of cold airflow damper 7 less than 10% the time, 33 output valve is then greater than 9 output valve.As a result, the opening of increase of the opening of primary air damper 17 and cold airflow damper 7 also increases.Therefore, the opening of cold airflow damper 7 always remains on about 10%.The exhaust outlet temperature that is to say pulverizer is mainly controlled by the primary air damper.

Here it should be noted, consider,,, also should leave some leeway in order to adapt to various different situations though wish always cold airflow damper 7 to cut out fully from the heat exchanger effectiveness aspect.

In the embodiment of Fig. 2, further control time air flow regulating damper 14 is obtained a certain openings amount the same with primary air damper 17 openings.In other words, the difference of the actual aperture of primary air damper 17 and 34 output valves of opening setting device is calculated by subtrahend device 35 and passing ratio integrator 36 and auto-manual selector 42 input time air flow regulating dampers 14.Control device A adds dress because of following reason.Be exactly to regulate from boiler to primary air AH ₁With inferior air current A H ₂Exhaust gas flow on, the load of forced fan 15 is pressed AH ₁Perhaps AH ₂The breather line difference very big difference is arranged.So in above-mentioned concrete form, this more or less leaves the present invention, the measure that is provided is just reduced to minimum to the load of forced fan 15 and is avoided strengthening the power of this pressure fan.Flow is worn to direct ratio in the load of forced fan 15 and the exhaust piping.Inferior air current A H ₂With primary air AH ₁Relatively, AH ₂The loss of exhaust piping flow account for major part, so increase cartridge controller A with a time air current A H ₂In loss reduce to minimum degree.

For this reason, controller A installs, inferior air current A H ₂The opening of damper 14 just can be regulated so that air flow regulating damper 17 is almost keeping 100% open mode (all opening).More particularly, opening except being subjected to the necessary temperature effect of primary air of primary air AH1 air flow regulating damper 17 also entered primary air AH ₁The influence of exhaust gas flow.Therefore, by regulating time air current A H ₂The opening of air flow regulating damper 14, enter primary air AH ₁Exhaust gas flow just can be controlled to keep primary air AH ₁Air flow regulating damper 17 reach almost 100% open.Do like this, just may make to account for most air current A H of whole flow losses ₂The loss of exhaust steam passage flow reduces to minimum degree.

With reference to figure 2 explanation the problems referred to above, the prodefined opening of primary air damper 17 is decided to be opening 80%, promptly almost all opens, and this is stored up into opening setting device 34.Deduct the actual aperture value of air flow regulating damper 17 with 35 li predetermined openings of subtrahend device 80%, the difference that draws is again through the arithmetical operation of proportional integral instrument 36, thereby draws the open order of time air flow regulating damper 14.In other words, when the opening amount of primary air damper 17 less than 80% the time, inferior air flow regulating damper 14 will be opened to reduce by primary air AH ₁Exhaust gas flow, regulate primary air damper 17 thus and make its opening amount increase to 80%.On the contrary, when the opening amount of primary air damper 17 greater than 80% the time, 14 of inferior air flow regulating dampers are closed to increase by primary air AH ₁Exhaust gas flow, regulate primary air damper 17 thus and make its opening amount reduce to 80%.

Below with reference to Fig. 3 the advantage that adjusting time air flow regulating damper 14 is brought is described.If inferior air flow regulating damper 14 remains on the fixing opening amount and regulates primary air damper 17, that will have following inconvenience.If this occurs, such as, because the water content of coal increases, primary air then needs more heat, and primary air damper 17 must all be opened, shown in Fig. 3 curve (1), the coal supply amount is also less relatively, and (this and generator load are directly proportional, if this coal-burning boiler is a generator), when load continues to increase, but can't obtain necessary heat.

As a time air current A H ₂The narrower of waste gas siphunculus choosing just can overcome this shortcoming, by primary air AH ₁Exhaust gas flow necessarily just can increase, in high load region, the problems referred to above also can solve, shown in the curve among Fig. 3 (2).But this situation causes in low load region, primary air AH ₁In rate of heat exchange reduce.

But, if inferior air flow regulating damper 14 is regulated like that by the foregoing description, adjusting so in this case just makes primary air damper 17 remain on 80% the opening amount shown in the numeral among Fig. 3 (3), promptly all open, even this not only can obtain the necessary heat of primary air in high load region, and be in order to prevent at low load region primary air AH ₁The reduction of interior rate of heat exchange.Simultaneously, also can be inferior air current A H ₂Waste gas siphunculus flow loss on one side reduces to minimum degree, flow loss of waste gas siphunculus and primary air AH here ₁Comparing on one side accounts for major part.

Here be noted that primary air damper 17 all not open and just be transferred to 80% opening amount that its reason is to allow some leeway to adjusting.Just the function that depends on pulverized coal flow flux (X) in the predetermined value of 22 li adjustings of subtrahend device primary air air door, 17 openings.

In addition, in the concrete form of Fig. 2, the opening amount that the control system B of primary air damper regulates air- flow air door 6 and 7 by the temperature output valve that feedback air themperature monitor 12 is measured in the outlet of pulverizer 8.But this adjusting can certainly be implemented by the output valve of temperature monitoring (not indicating) in the feedback pulverizer.

Also have, in the embodiment of Fig. 2, pulverizer delivery outlet temperature or built-in temperature are to regulate the air-flow air door according to the gas flow temperature instruction of feedback to remain unchanged., but when controlling, open circuit also can obtain the sample effect when air flow regulating damper, and as described below.

Shown in Figure 4 is an alternative embodiment of the invention.At first, the frame mode of air flow regulating damper control system B and Fig. 2 is the same, and in other words, air flow regulating damper 6 and 7 adjusting all will make the delivery outlet temperature of pulverizer remain unchanged.In air flow regulating damper control system A, 100 expression load command source, or main steam flow command source, or the command source of the gas flow of from these instructions, drawing, function generator of 110 expressions, it sends the instruction of regulating air-flow air door opening according to load instruction or main steam flow instruction (or gas flow instruction), is adjusted in the exhaust gas flow of time flow type calorifier exhaust outlet; One automatic one manual selector of 42 expressions; 14 are illustrated in the air flow regulating damper that time flow type calorifier delivery outlet is regulated exhaust gas flow.Fig. 5 between the two relation below mode has shown by way of example, i.e. the relation of load (main steam flow) and opening amount, this opening amount is that the said flow damper open order that function generator 110 sends among Fig. 4 is peculiar.The air flow regulating damper open order that function generator 110 sends can correspondingly be regulated air-flow air door 14 according to load or main steam flow (or gas flow) by automatic end in automatic-manual selector 42.Therefore and the rate of heat exchange that increases is regulated so when load increased, the exhaust gas flow of input primary air heater 1 was also along with.This is with regard to having compensated pulverizer delivery outlet temperature and reducing that thereby the temperature that makes the pulverizer delivery outlet remains on a particular value and constant.

As mentioned above, according to the present invention, because temperature is regulated by the flow through exhaust gas flow of air heater of control in the pulverizer, so air heater need not extended volume still can keep efficient heat exchange.

Claims (5)

1, the control method of air heater in a kind of coal-burning boiler system, this system comprises: boiler, produce the air heater of thermal current by heat exchange between this boiler waste gas and the atmospheric air, pulverize coal-fired and use above-mentioned thermal current oven dry coal dust that above-mentioned air heater produces and with its pulverizer of importing above-mentioned boiler, it is characterized in that: the temperature control of this pulverizer delivery outlet is to be undertaken by the flow that adjusting enters the above-mentioned waste gas of above-mentioned air heater.

2, the method that is proposed according to claim 1, also comprise the blender that mixes the above-mentioned thermal current that cold air and above-mentioned boiler produced in the said system, it is characterized in that: coal dust is to arrive above-mentioned boiler by the air flow delivery that enters above-mentioned pulverizer internal diameter blender mixing; The mixed proportion of above-mentioned cold and hot air stream in above-mentioned blender regulated according to above-mentioned pulverizer delivery outlet temperature; Above-mentioned exhaust gas flow in above-mentioned air heater is regulated according to above-mentioned mixed proportion.

3, the method that is proposed according to claim 2 is characterized in that: above-mentioned blender is to be made of thermal current damper and cold airflow damper, and each air door all can be controlled by the air mass flow of air door separately.

4, the method that is proposed according to claim 1, also include the blender of the thermal current mixing that cold air and above-mentioned boiler are produced in the said system, it is characterized in that: coal dust is to arrive above-mentioned boiler by entering the air flow delivery of mixing through blender in the above-mentioned pulverizer; The mixed proportion of above-mentioned cold and hot air stream in above-mentioned blender regulated according to above-mentioned pulverizer delivery outlet temperature; Above-mentioned exhaust gas flow in above-mentioned air heater is according to the Load Regulation of above-mentioned boiler.

5, the method that is proposed according to claim 4 is characterized in that: above-mentioned blender is to be made of thermal current damper and cold airflow damper, and each air door all can be controlled by the air mass flow of air door separately.

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