Title of Invention	"SYSTEM FOR AUTOMATIC CONTROL OF NEGATIVE PRESSURE IN FURNACE AND OF FLUE GAS TEMPERATURE"
Abstract	The method and system for automatic control of vacuum with simultaneous control of temperature difference of waste gases in channels with electrofliters, lies in that, the control of temperature difference of waste gases influences adjustment devices of ventilator courses, which are also influenced by vacuum control in the combustion furnace.

Full Text

The subject of the invention is the system for automatic control of negative pressure in furnace chamber and of whste gastemperaturcs wherein waslt gas is hereinof descrition as flue gas following the rotational air heater, applied in the power boiler, which is, particularly equipped, with three channels carrying away flue gas and which works with three flue gas fans and contains the subsystem of automatic control of, negative pressure in the furnace chamber and subsystem of controlling a load of the flue gas fans connected with it. The known and applied in power industry a system of controlling of negative pressure in the furnace chamber of the power boiler contains a negative pressure sensor in the furnace chamber, which is connected with the controller with three way or continuous output. The said three way controller manages the steering devices of the flue gas fans, transmitting identical signals to each executive system of the steering device. The differences in the load of fans occurring during adjustment of individual flue gas fans are equaled using manual control. In case of the controller with continuous output the control is carried out through the executive controller with the feedback from the location of the fan baffles of flue gas fans. From German patent description No DD-PS 13132 there is known the system of controlling of negative pressure in the furnace chamber with singular flue gas channel, in which there is housed a flap of flue gas damper and an axial-flow blower. A negative pressure is controlled in the furnace chamber and in the whole scope of the boiler load so as to be constant and equaled to 30 kPa. by means of changing the setting of said flap and controlling the blower power, depending on the parameters measured in the furnace chamber and in the flue gas channel. Next, from German patent description No DE 34 02 787 A1 there is known a heating boiler fueled with solid fuel, equipped with a singular flue gas channel and a system of controlling a heating power of the boiler. In the flue gas channel there is housed a flue gas fan with a number of rotations regulated depending on the temperature in the input of the boiler and/or depending on the temperature of flue gas. In this description the regulation of said heating power or the temperature of said flue gas is effected through a regulation of the quantity of exhausted flue gas. During sucking off of said flue gas the negative pressure is produced in the furnace chamber, which enables a suction of primary and secondary air and a regulation of gas flow intensity through the furnace chamber. The drawback of the system of controlling the negative pressure in the furnace chamber of the boiler, so far known and applied in the power industry, is the inability or at least hindrance in maintaining uniform flow of flue gas in the boiler, in its lateral cross-sections. The consequence is the non-attainment of maximum attainable thermal efficiency of the boiler. The phenomenon of non-uniform flow of flue gas is indicated by the temperature difference of the flue gas in the individual channels, through which the flue gases are sucked off by means of flue gas fans. The said temperature differences are the result of the differences in efficiency of individual flue gas fans. The efficiency of flue gas fans is controlled by means of the known automatic control system of negative pressure in the furnace chamber, whereas the fans are controlled simultaneously by means of said controller with the three way output. This is caused by the adjustment of the steering devices of the flue gas fans by means of the executive systems connected with said devices. This system appears to be imperfect, as it is unable to adjust all flue gas fans to the same level of the efficiency, which leads to the temperature difference of flue gases in the individual channels, through which the flue gases are being sucked off by means of flue gas fans. This is caused, by the fact, that the executive systems, used for adjusting steering devices of individual flue gas fans, make an opening and an closing of said devices solely dependent on the duration of the controlling impulses acting on the controller. Meanwhile, the output location of the steering devices, before changing the dimension of their opening provided by the action of the control system, and different starting and coasting times of servo-motors shifting said devices which are caused by different internal resistances and mechanical clearances of executive devices transmitting the same impulses to each fan from a common controller, cause irregularities of the efficiency of individual fans which changes with the duration. This requires a constant manual correction of the settings, in the controlling systems of individual flue gas fans. This is a discontinuous and imprecise control. Next, the system known from German description No DD-PS 13 132 controls only negative pressure in the furnace chamber. However, in the system known from German description No DE 34 02 787 A1 the negative pressure is not controlled in the furnace chamber of the boiler but only the intensity of the gas flow passing through the furnace chamber which causes uncontrolled fluctuations of pressure in the furnace chamber of the boiler. The purpose of the invention is the system for automatic control of negative pressure in the furnace chamber with simultaneous control of difference temperatures of flue gases in the power boiler provided with three flue gas channels and with the same number of flue gas fans, whereas said system by controlling the efficiency of said fans will ensure an uniformity of combustion processes in the lateral cross-section of the furnace chamber of the boiler. This purpose was achieved fey the fact, that the negative pressure controller, in the furnace chamber, together with the temperature controller which equalizes the temperatures of flue gas in the output -channels automatically acts on set means. The system according to the invention, has temperature sensors in ail flue gas channels, whereas the first and the third sensor located respectively in the first and in the third flue gas channels of two border flue gas fans are connected with the inputs of the temperature controller. The station for setting the value of temperature difference of flue gas flowing in the first and in, the third flue gas channel is also connected with the input of the temperature controller The output of the temperature controller is connected through the adders with . the first and the third flue gas flow executive controller of the border flue gas fans. The output of the negative pressure controller in the furnace chamber is also connected with the adders. Whereas the inputs of the negative pressure controller are connected with the negative pressure sensor and the station for setting negative pressure. The inputs of the second temperature controller linked with the middle flue gas fan are connected with the second temperature, sensor in the middle flue gas channel of the middle flue gas fan and with the first and the third temperature sensor through the averaging-adder as well as with the station for setting the value of temperature difference of flue gas. Each flue gas flow executive controller has a feedback of active power of the engine actuating the flue gas fan through the power transducers of said fans. The subject of the invention as an-embodiment js^hown-in'trje figure: ail-a block diagram of the system.. The power boiler is equipped with three channeis'Kl,K2 and K3 carrying , out flue gas In each , the first, the second, the third flue gas channel K1, K2, K3 there is housed one of three flue. gas fans W1 W2, W3 in the furnace chamber of the boiler, not shown in the figure, there is installed the negative pressure sensor Ph, which is connected with the input of the negative pressure Accordingly, there is provided a system for automatic control of negative pressure in furnace chamber and of flue gas temperature, coprising flue gas sensors, temperature controllers and subsystem of negative pressure control in the furnace chamber and subsystem of controlling load of three flue gas fans characterized in that, the first and the third temperature sensor situated, respectively, in the first and in the third flue gas channel of the border first and third flue gas fans, are connected with the inputs of the first temperature controller and the input of said controller is also connected with the station setting the value of temperature difference of flue gas flowing in the first and in the third flue gas channel and the output of the first temperature controller is connected through adders with the first and the third flue gas flow executive controllers of the border first and third flue gas fans, and the output of the negative pressure controller in the furnace chamber is also connected with the adders and the inputs of said negative pressure controller are connected with the negative pressure sensor and with a station of setting negative pressure, whereas the inputs of the second temperature controller connected with the middle second flue gas fan are connected with the second temperature sensor in the middle second flue gas channel of the middle second flue gas fan and with the first and the third temperature sensor through the averaging adder, as well as with the station setting the temperature difference, and each flue gas flow executive controller of each flue gas fan has a feedback of active power of the engine actuating the flue gas fans through the power transducers of these fans. controller Rph. The station for setting negative pressure Phz is connected with the input of second negative pressure controller Rph. The output of the negative pressure controller Rph is connected with the first and the third flue gas flow executive controller Rc1 and Rc3 of the border first and third flue gas fans WC1 and WC3, whereas these connections are made through the adders S1 and S3 assigned to the first and the third flue gas flow executive controllers Rc1 and Rc3 respectively. One of three temperature sensors T1,T2,T3 is located in each the first, the second and the third flue gas channel K1.K2 and K3 between the first, the second and the third flue gas fans WC1, WC2, WC3 and electro-filters , not shown in the figure. The first and the third temperature sensors T1. and T3. located respectively, in the border first, and third flue gas channels K1 and K3 are connected with the inputs of the first temperature controller Rtl,3 connected with the border first and third flue gas fans WC1 and WC3. The input of the first temperature controller Rtl.3 is also connected with the station for Setting the value of temperature difference At of flue gas in the border first and third flue gas channels K1 and K3. The output of the first temperature controller Rtl,3 is connected with the adders S1. and S3. the outputs of which are connected respectively with the inputs of the first and the third executive controllers Rc1 and Rc3 of flue gas flow. The outputs of this first and the third flue gas flow executive controllers Rc1 and Rc3 are connected with the first and the third executive devices UW1 and UW3 of the firsthand the third flue gas fans WC1 and WC3 which open or close the steering devices of said flue gas fans WC1 and WC3. The engine power of the first and the third flue gas fans WC1 and WC3 is measured by means of the power transducers M, which are connected with the inputs of the first and of the third flue gas flow executive controllers Rc1 and Rc3 forming a feedback of power engines actuating'the first and the third flue gas fans WC1 and WC3.' In the middle second flue gas channel K2 there is placed the second temperature sensor T2.which is connected with the input of the second temperature controller Rt2 connected with the middle second flue gas fan WC2 housed in the middle second flue gas channel K2. The second input of the second temperature controller Rt2 is also connected with the first and the third temperature sensors T1 and T3 located in the border first and third flue gas channels Kl and K3. The first and the third temperature sensors T1 and T3 are connected with the second temperature controller Rt2 through the averaging adder S2. The input of the second temperature controller Rt2 is connected with the station for setting the value of temperature difference Atr of flue gas. The output of the second temperature controller Rt2 is connected with the input of the second flue gas flow executive controller Rc2 whereas the output of said executive controller Rc2 is connected with the input of the second executive device UW2, connected with the steering device of the middle flue gas fan WC2. In the drive of the middle second flue gas fan WC2 there is located the power transducer M connected with the input of the second flue gas flow executive controller Rc2 having a feedback of active power of engine actuating the middle second flue gas fan WC2. Flue gas fans WC1, WC2 and WC3 of the power boiler connected, respectively, with the flue gas channels K1.K2 and K3 create the negative pressure in the furnace chamber of the boiler. When the negative pressure in f •' the furnace chamber is higher than the pre-set negative pressure, then the negative pressure controller Rph causes a decrease of efficiency of two border first and third flue gas fans WC1 and WC3 as long as said negative pressure is equaled to the pre-set negative pressure. Simultaneously, the negative pressure controller Rph together with the first temperature controller Rtl.3, in which a temperature difference of flue gas in the border flue gas channels K1 and K3 is compared with the pre-set temperature difference of flue gas, automatically act on set means of the border first and third flue gas fans WC1 and WC3 . The station for setting negative pressure Phz, defines the negative pressure, which should exist in the furnace chamber of the boiler. The signal from said station Phz is transmitted to the input of the negative pressure controller Rph. The second input of the negative pressure controller Rph is provided with feedback signal sent by the negative pressure sensor. Ph. The negative pressure controller Rph compares the signal from said station Phz with the signal from the negative pressure sensor Ph. If the negative pressure in the furnace chamber of the boiler is lower than the pre-set negative pressure, then the negative pressure controller Rph simultaneously transmits a signal to the adders S1 and S3. The outputs of the adders S1 and S3 transmit the same signals simultaneously to the first and the third flue gas flow executive controller Rc1 and Rc3 increasing the efficiencies of the flue gas fans WC1 and WC3, that means a bigger opening of the first and the second executive devices UW1 and UW3. So, the first and the third flue gas fans WC1 and WC3 will start to suck more flue gases from the furnace chamber in the unit of time, thus causing an absolute pressure to be decreased in the furnace chamber; it means that the negative pressure will increase to the value pre-set in the station Phz. If the negative pressure in the furnace chamber will be bigger than the pre-set value in the station Phz, then the negative pressure controller Rph will cause a decrease of the efficiency of the first and the third flue gas fans WC1 and WC3. until the negative pressure equals to the pre-set value: An action of the negative pressure controller Rph does not exclude the existence of an inequality of flue gases flow in the boiler. This is prevented by a subsystem for automatic control of temperature difference of flue gases in the individual channels K1. K2 and K3. The station for setting the value of temperature difference At defines the allowed temperature difference of flue gases in the first and the second flue gases channels K1 and K2. The signal from the station for setting the value of the temperature difference At is transmitted onto the input of the first temperature controller Rtl,3. Simultaneously, the indications of the first and the third temperature sensor T1 and T3 are transmitted onto the inputs of the first temperature controller Rtl,3. In the first temperature controller Rtl,3 the temperature difference in the border channels K1 and K3 is compared with the pre-set temperature defined in the station for setting the value of the temperature difference At. When said difference is bigger than the pre-set value, the first temperature controller Rtl.3 transmits the signal simultaneously to the adders S1 and S3. Said signal reaches the negative input of the adder S1 and the positive input of the adder S3. Such connection makes that the first and the third flue gases flow executive controllers Rc1 or Rc3 increase the efficiency of this flue gas fan, which sucks flue gases from that channel, where the temperature is lower, and decrease, by the same value, the efficiency of this fan in the channel, where the temperature of flue gases is higher. The increase or decrease of the efficiencies of the first and the third flue gas fans WC1 and WC3 is performed by increasing or decreasing the opening of the first or the third executive device UW1 or UW3 of the first or the third flue gas fan WC1 or WC3, respectively. However it can happen, that the signal ,for example, from the first flue gases flow executive controller Rc1 cause an action of the first executive device UW1. but clearances, internal resistances and so forth, will not cause sufficient opening or closing of the steering device of the first flue gas fan WC1. Therefore the applied system uses an active power of engine of the first, the second and the third flue gas fans WC1. WC2. WC3 as signal of feedback and the power transducer M transmits a quantity signal of power received by the drive of the first flue gas fan WC1 to the first executive controller Rc1; This power is proportional to the efficiency of the first flue gas fan WC1. So, if for example, the first flue gas fan WC1 has to increase the efficiency, but the steering device will not be sufficiently opened, then the supplied power will be smaller than the power sufficient to its increased efficiency. When the signal from the power transducer M reaching the first executive controller Rc1 will indicate such difference, then said controller Rc1 will transmit the signal of bigger opening of the steering apparatus of the first flue gas fan WC1 to the first executive device UW1. A principle was assumed, that the temperature of flue gases in the middle second channel K2 should not differ from the average temperature of flue gases in the border first and third channel K1_ and K3. by the value pre-set in the station for setting the value of temperature difference Atr. For this purpose, the inputs of the second temperature controller Rt2, connected with the second flue gas fan WC2 in the middle second channel K2, are joined with the second temperature sensor T2 located in the middle channel K2 and the averaging adder S2. Said averaging adder S2 has its inputs connected with the first and the third temperature sensors T1 and T3 measuring the temperature in the border channels K1 and K3. Said adder S2 averages the signals from the first and third temperature sensors T1 and T3 and transmits the signal to the second temperature controller Rt2, where the difference between indications of the second temperature sensor T2 and the average temperature of the first and third sensor T1 and T3 indications, is determined. Said difference is compared with the temperature defined in the station for setting the value of temperature difference Atr. and depending on the result, the second temperature controller Rt2 transmits the signal to the second flue gases flow executive controller Rc2 for increasing, decreasing or maintaining the efficiency of the middle second flue gas fan WC2 unchanged. From the second temperature controller Rt2; further elements of the system controlling the efficiency of the middle second flue gas fan WC2 are identical with elements of the system of automatic control of the border first and third flue gas fans WC1 and WC3. WE CLAIM:- 1.A system for automatic control of negative pressure in furnace chamber and of flue gas temperature, comption singg sensors, temperature controllers and subsystem of negative pressure control in the furnace chamber and subsystem of controlling load of three flue gas fans characterized in that, the first and the third temperature sensor (T1, T3) situated, respectively, in the first and in the third flue gas channel-(K1, K3) of the border first and third flue gas fans (WC1. WC3). are connected with the inputs of the first -temperature controller (Rtl.3) and the input of said controller (Rtl,3) is also connected with the station setting the value of temperature difference (t) of flue gas flowing in the first and in the third flue gas channel (K1, K3) and the output of the first temperature controller (RtL3) is connected through adders (S1. 8-3) with'the first and the third flue gas flow executive controllers (Rc1, Rc3) of the border first and third flue gas fans (WC1, WC3), and the output of the negative pressure . controller (Rph) in the furnace chamber is also connected with the adders (S1, S3) and the inputs of said negative pressure controller (Rph) are connected with the negative pressure sensor (Ph) and with a station of setting negative pressure (friz), whereas the inputs of the -second temperature controllerTRt2) connected with the middle second flue gas fan (WC2) are connected with the second temperature sensor (T2) in the middle second flue gas channel (K2) of the middle second flue gas fan (WC2) and .with the firsthand 'the third temperature sensor (T1 ,T3) through the averaging adder (S2), as well as with the station setting the temperature difference (Atr). and each ffue gas. flow executive controller (Rc1. Rc2, Rc3) of each-, flue gas fan -(WC1, WC2; WC3) has a feedback of active power of the engine actuating the flue gas fan's (WC1, WC2. WC3) through the power transducers' (M) of these fans. 2. A system for automatic control negative pressure in furnace .chamber and of flue gas temperature, substantially as herein described with reference to the accompanying drawings.

Documents:

1195-del-1997-abstract.pdf

1195-del-1997-claims.pdf

1195-del-1997-correspondence-others.pdf

1195-del-1997-correspondence-po.pdf

1195-del-1997-description (complete).pdf

1195-del-1997-drawings.pdf

1195-del-1997-form-1.pdf

1195-del-1997-form-13.pdf

1195-del-1997-form-19.pdf

1195-del-1997-form-2.pdf

1195-del-1997-form-3.pdf

1195-del-1997-form-4.pdf

1195-del-1997-gpa.pdf

1195-del-1997-petition-137.pdf

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