CN111926606B - Online monitoring method for energy efficiency of drying part of paper machine - Google Patents
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Abstract
The invention discloses an online monitoring method of energy efficiency of a drying part of a paper machine, which establishes a paper temperature (T) of a monitoring part of the drying part through conservation of materials and energy in the drying process p ) And humidity (u), monitoring the temperature (T) of the pocket air at the site a ) And Humidity (AH) a ) The method is characterized in that the method is an unknown quantity quaternary partial differential equation set process model, then process data which is easy to collect in real time in the actual papermaking drying production process is used as known quantity, initial value and boundary condition, the quaternary partial differential equation set process model established by the method is solved to obtain real-time data of key process parameters of the papermaking drying part, and then energy efficiency of the papermaking machine drying part is calculated and obtained, so that the online monitoring of the energy efficiency of the paper drying process is realized, black box operation is avoided, the running condition of the papermaking machine drying part can be accurately mastered, and the method has important significance in guiding production adjustment and realizing energy conservation and emission reduction.
Description
Technical Field
The invention relates to an online monitoring method for energy efficiency of a drying part of a paper machine, and belongs to the technical field of paper industry.
Background
Papermaking is an energy-intensive industry, and belongs to one of four world high-energy-consumption industries. In China, the energy consumption of the paper industry is the first energy consumption of the light industry, and the energy-saving task is urgent. The drying part is the process with the highest energy consumption of the paper machine, and accounts for about 60% of the total energy consumption of the paper machine, and is the focus of energy-saving work in the paper industry. The drying part is a complex system which relates to the mutual coupling of multiple materials (steam, air, paper and the like), multiple processes (heat transfer process and mass transfer process), and the complex mechanism is that the operation state of the drying part needs to be comprehensively monitored to better help enterprises to realize more efficient production management.
The existing information system of enterprises can only realize partial monitoring functions on the drying part, such as DCS (Distributed Control System ) can monitor the steam state of the drying part, the ventilation and exhaust state of the gas hood and the like; QCS (Quality Control System ) can monitor quantitative and moisture information as the paper leaves the dryer section. The system does not monitor the key process parameters of the paper, such as the surface temperature of each drying cylinder, the paper temperature and humidity at the outlet of the drying cylinder, the air temperature and humidity of the bag area of the drying cylinder and other process personnel concerned in the running process of the drying part, and the drying capacity and energy efficiency indexes of the management personnel, such as the output of the drying cylinder, the steam unit consumption of the drying part, the heat efficiency of the drying part, the electric unit consumption of a ventilation and waste heat recovery subsystem, the heat recovery efficiency of the ventilation and waste heat recovery subsystem and the like. There are two main reasons: (1) The paper is dried in a drying part, which is a continuous high-speed movement process under the high-temperature and high-humidity environment, and some parameters are difficult to measure, and the sensor is quite expensive; (2) The dryer section is a relatively compact system, limited by installation space, and some parameters are not measured.
Therefore, the dryer section paper drying process is often referred to in the industry as a "black box" process, and the production regulation is based on human experience, and the energy efficiency level is generally low, so that the dryer section paper drying process has great energy saving potential. The drying process of the drying part is realized through the drying cylinder of the drying part, so that the energy efficiency of the drying part of the paper machine is monitored on line, the black box is visible, and the method has important significance in guiding production adjustment and realizing energy conservation and emission reduction.
Disclosure of Invention
The invention aims to solve the problem that the paper drying process of a drying part of a paper machine is difficult to monitor on line, and provides an on-line monitoring method for the energy efficiency of the drying part of the paper machine.
The invention adopts the following technical scheme to solve the technical problems:
an on-line monitoring method for energy efficiency of a drying part of a paper machine comprises the following steps:
(1) Real-time on-line acquisition of paper machine speed V and paper forming ration BW o Moisture W of paper o Collecting the humidity u of paper at the inlet of the drying part on line in real time 0 And temperature T p,0 Air supply quantity m of each drying cylinder of real-time online collection ventilation and waste heat recovery subsystem a,sup,i Temperature T of air supply a,sup,i Absolute humidity AH of supply air a,atm,i Data, and collecting steam pressure of each drying cylinder of steam condensate subsystem on line in real timeP s,i Data, real-time online acquisition of the amount of steam consumed per unit time ṁ by the steam-condensate subsystem s,SCS And enthalpy H of consumption of steam s,SCS Data, ṁ of steam consumption per unit time of air heating module in ventilation and waste heat recovery subsystem is collected online in real time s,AH And enthalpy H of consumption of steam s,AH Data, wherein i represents a cylinder number;
(2) Based on the conservation of materials and energy in the drying process of the paper in the drying part, a process model is established, wherein the process model is based on the temperature T of the paper p And humidity u, temperature T of bag air a And absolute humidity AH a For the unknown quantity and the quaternary partial differential equation system taking the data acquired in the step (1) as the known quantity, the temperature T of the paper at the outlet of each drying cylinder key process parameter drying cylinder of the drying part is realized by solving the equation system p,i And humidity u i Temperature T of air in dryer pocket a,i And absolute humidity AH a,i Wherein i represents the cylinder number;
(3) The following formula is used:
T c,i = {T s,i /[(1/α s-c )+(d c,i /k c,i )]+θ i h c-p T p,i +(1-θ i )h c-a T a,i }/{1/[(1/α s-c )+(d c,i /k c,i )]+θ i h c-p +(1-θ i )h c-a } （1）
T c,i = [θ i h c-p T p,i +(1-θ i )h c-a T a,i ]/[θ i h c-p +(1-θ i )h c-a ] （2）
calculating to obtain the surface temperature T of each drying cylinder c,i The formula (1) is a calculation formula of a heated drying cylinder, the formula (2) is a calculation formula of a non-heated drying cylinder, the on-line real-time monitoring of the surface temperature of each drying cylinder key process parameter of the drying part is realized,
wherein T is s,i Representing the temperature of steam in a dryer, and using T s,i = [3816.44/(23.1934-lnP s,i )]-a 227.03 calculation of the number of points,
wherein i represents dryer plaitingNumber, θ i Represents the cylinder wrap angle coefficient, alpha, numbered i s-c Represents the condensing heat transfer coefficient, d c,i Represents the dryer wall thickness, k, numbered i c,i Represents the heat conductivity of the dryer wall, h, numbered i c-p Represents the contact heat transfer coefficient between the drying cylinder and the paper, h c-a T represents the convection heat transfer coefficient between the drying cylinder and the air in the bag area a,i The air temperature of the drying cylinder bag area with the number i is represented by T p,i Representing the paper temperature at the dryer numbered i;
(4) The following formula is used:
R CN,i = 60·V·BW 0 ·(1-W 0 /100)·(u i-1 -u i )/(θ i πD c,i )
calculating and obtaining the output R of each drying cylinder CN,i Realizes the on-line real-time monitoring of the output index of each drying cylinder of the drying part,
wherein i represents the number of the drying cylinder, u i Represents the paper humidity at the outlet of a dryer with dryer number i, u i-1 Represents the paper humidity at the outlet of a dryer with the dryer number i-1, and u is when i is 1 i-1 I.e. u 0 ，D c,i Represents the diameter, theta, of the ith dryer cylinder i A dryer wrap angle coefficient with the number i;
(5) The following formula is used:
SSC p = 60(ṁ s,SCS +ṁ s,AH )/(V·BW 0 ·B)
calculating to obtain steam unit consumption SSC of drying part p Realizes the online real-time monitoring of the steam unit consumption of the drying part,
wherein B represents the width of the paper machine;
(6) The following formula is used:
ΔH ev,i =46.544292(1/φ-1)[(u i-1 +u i )/2] 1.0585 [(T p,i-1 +T p,i )/2+273.15] 2 +[2504.7-2.4789(T p,i-1 +T p,i )/2]×10 3
calculating the average evaporation heat delta H of the water evaporation of the drying cylinder with the number i ev,i ，
Wherein, phi=1-exp { -47.58[ (u) i-1 +u i )/2] 1.877 -0.10085[(T p,i-1 +T p,i )/2][(u i-1 +u i )/2] 1.0585 }；
(7) The following formula is used:
HEE = [Σ
(θ i πD c,i R CN,i ΔH ev,i /3600)/(ṁ s,SCS H s,SCS +ṁ s,AH H s,AH )]×100%
the thermal efficiency HEE of the drying part is obtained through calculation, the on-line real-time monitoring of the thermal efficiency of the drying part is realized,
wherein N represents the number of drying cylinders, i represents the number of drying cylinders, D c,i Represents the diameter, θ, of a dryer with the number i i The cylinder wrap angle coefficient is denoted by number i.
The process model of the quaternary partial differential equation set is as follows:
wherein m is ev,a = {exp[23.1934-3819.44/(T p +227.03)]·[1-exp(-47.58u 1.877 -0.10085T p
u 1.0585 )]-exp[23.1934-3819.44/(T a +227.03)]}/(T a +273.15)，ΔH ev = 46.544292·u 1.0585 ·
(T p +273.15) 2 ·{1/[1-exp(-47.58u 1.877 -0.10085T p u 1.0585 )]-1}+(2504.7- 2.4789T p )·10 3 ；
Δ 1 And delta 2 For the coefficient related to the drying surface, delta if the drying surface at the monitoring point consists of cylinder-paper-wire-air 1 = FRF、Δ 2 =1, Δ if the drying surface at the monitoring point consists of cylinder-dry wire-paper-air or cylinder-paper-air 1 = 1、Δ 2 =1, if the dry surface at the monitoring pointConsisting of air-paper-dry wire-air delta 1 = 1+FRF、Δ 2 =2, Δ if the dry face at the monitoring point consists of air-paper-air 1 = 2、Δ 2 =2, frf represents the dry-net influencing factor; r is R p And R is s R is the coefficient related to heat supply when the paper directly receives heat from steam supply p = h s-p (3816.44/(23.1934-lnP s )-227.03-T p ) Otherwise R p 0, R when the bag air directly receives heat from the steam supply s = h s-a (3816.44/(23.1934-lnP s )-227.03- T a ) Otherwise R s Is 0;
u represents the paper humidity, T p Indicating paper temperature, AH a Indicating absolute humidity of air in bag area T a The air temperature of the bag area is represented, and t represents time;
C p,dp the specific heat value 1423.5J/(kg. DEG C) of the absolute dry paper is shown, C a The specific heat value of the absolute dry air is 1010J/(kg. DEG C), C v The specific heat value of water vapor is 1880J/(kg. DEG C.), and gamma 0 Represents the latent heat of vaporization of water at 0℃under normal atmospheric pressure at a constant value of 2501000J/kg, C p,w = 0.0139(T p /℃) 2 -1.3129 (T p Heat per degree centigrade) +4206.1 for water, Ɛ for air distribution coefficient of ventilator to corresponding dryer group air supply, m a,sup Represents the air supply quantity L of the ventilation and waste heat recovery subsystem y Indicating the width of the paper machine, h s-p Represents the convective heat transfer coefficient between steam and paper, h s-a Represents the convective heat transfer coefficient between steam and pocket air, h p-a Representing the convective heat transfer coefficient between the paper and pocket air, R v The gas constant is 461.5J/(kg. DEG C.), K p-a Representing the sheet-air contact surface to flow coefficient.
The invention has the beneficial effects that: the method has the advantages that the process data which are easy to collect in real time in the actual papermaking drying production process are used as the known quantity, the initial value and the boundary condition, the real-time data of key process parameters of the papermaking drying part are obtained by solving the quaternary partial differential equation set process model established by the method, and then the energy efficiency of the papermaking drying part is obtained by calculation, so that the online monitoring of the energy efficiency of the paper drying process is realized, the black box operation is avoided, the running condition of the papermaking drying part can be accurately mastered, and the method has important significance in guiding production adjustment and realizing energy conservation and emission reduction.
Drawings
Dryer structure and partition diagram of fig. 1
FIG. 2 single-hanging upper-exhaust heat-supply dryer Phase1 drying interface paper infinitesimal material conservation analysis chart
FIG. 3 is a diagram showing the analysis of the infinitesimal energy conservation of paper at the Phase1 drying interface of a single-hanging upper-exhaust heat-supplying dryer
FIG. 4 is a diagram showing air infinitesimal mass conservation analysis in a bag region of a Phase1 drying interface of a single-hanging upper-exhaust heat supply dryer
FIG. 5 analysis chart of air infinitesimal energy conservation in bag region of Phase1 drying interface of single-hanging upper-exhaust heat supply drying cylinder
FIG. 6 embodiment dryer section block diagram
FIG. 7 sheet moisture
FIG. 8 paper temperature
FIG. 9 bag air humidity
FIG. 10 bag air temperature
FIG. 11 dryer surface temperature
FIG. 12 dryer output
Detailed Description
In order that the above-recited objects, features and advantages of the present invention will become more apparent, a more particular description of the invention will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, however, the present invention may be embodied in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete. The present invention may be embodied in many other forms than described herein and similarly modified by those skilled in the art without departing from the spirit of the invention, so that the invention is not limited to the specific embodiments disclosed below. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
An on-line monitoring method for energy efficiency of a drying part of a paper machine comprises the following steps:
(1) Real-time on-line acquisition of paper machine speed V and paper forming ration BW o Moisture W of paper o Collecting the humidity u of paper at the inlet of the drying part on line in real time 0 And temperature T p,0 Air supply quantity m of each drying cylinder of real-time online collection ventilation and waste heat recovery subsystem a,sup,i Temperature T of air supply a,sup,i Absolute humidity AH of supply air a,atm,i Data, and collecting steam pressure of each drying cylinder of steam condensate subsystem on line in real timeP s,i Data, real-time online acquisition of the amount of steam consumed per unit time ṁ by the steam-condensate subsystem s,SCS And enthalpy H of consumption of steam s,SCS Data, ṁ of steam consumption per unit time of air heating module in ventilation and waste heat recovery subsystem is collected online in real time s,AH And enthalpy H of consumption of steam s,AH Data, wherein i represents a cylinder number;
(2) Based on the conservation of materials and energy in the drying process of the paper in the drying part, a process model is established, wherein the process model is based on the temperature T of the paper p And humidity u, temperature T of bag air a And absolute humidity AH a For the unknown quantity and the quaternary partial differential equation system taking the data acquired in the step (1) as the known quantity, the temperature T of the paper at the outlet of each drying cylinder key process parameter drying cylinder of the drying part is realized by solving the equation system p,i And humidity u i Temperature T of air in dryer pocket a,i And absolute humidity AH a,i Wherein i represents the cylinder number;
(3) The following formula is used:
T c,i = {T s,i /[(1/α s-c )+(d c,i /k c,i )]+θ i h c-p T p,i +(1-θ i )h c-a T a,i }/{1/[(1/α s-c )+(d c,i /k c,i )]+θ i h c-p +(1-θ i )h c-a } （1）
T c,i = [θ i h c-p T p,i +(1-θ i )h c-a T a,i ]/[θ i h c-p +(1-θ i )h c-a ] （2）
calculating to obtain the surface temperature T of each drying cylinder c,i The formula (1) is a calculation formula of a heated drying cylinder, the formula (2) is a calculation formula of a non-heated drying cylinder, the on-line real-time monitoring of the surface temperature of each drying cylinder key process parameter of the drying part is realized,
wherein T is s,i Representing the temperature of steam in a dryer, and using T s,i = [3816.44/(23.1934-lnP s,i )]-a 227.03 calculation of the number of points,
wherein i represents the cylinder number, θ i Represents the cylinder wrap angle coefficient, alpha, numbered i s-c Represents the condensing heat transfer coefficient, d c,i Represents the dryer wall thickness, k, numbered i c,i Represents the heat conductivity of the dryer wall, h, numbered i c-p Represents the contact heat transfer coefficient between the drying cylinder and the paper, h c-a T represents the convection heat transfer coefficient between the drying cylinder and the air in the bag area a,i The air temperature of the drying cylinder bag area with the number i is represented by T p,i Representing the dryer pocket paper temperature numbered i;
(4) The following formula is used:
R CN,i = 60·V·BW 0 ·(1-W 0 /100)·(u i-1 -u i )/(θ i πD c,i )
calculating and obtaining the output R of each drying cylinder CN,i Realizes the on-line real-time monitoring of the output index of each drying cylinder of the drying part,
wherein i represents the number of the drying cylinder, u i Represents the paper humidity at the outlet of a dryer with dryer number i, u i-1 Represents the paper humidity at the outlet of a dryer with the dryer number i-1, and u is when i is 1 i-1 I.e. u 0 ，D c,i Represents the diameter, theta, of the ith dryer cylinder i A dryer wrap angle coefficient with the number i;
(5) The following formula is used:
SSC p = 60(ṁ s,SCS +ṁ s,AH )/(V·BW 0 ·B)
calculating to obtain steam unit consumption SSC of drying part p Realizing on-line real-time monitoring of the steam unit consumption of the drying part, wherein B represents the width of the paper machine;
(6) The following formula is used:
ΔH ev,i =46.544292(1/φ-1)[(u i-1 +u i )/2] 1.0585 [(T p,i-1 +T p,i )/2+273.15] 2 +[2504.7-2.4789(T p,i-1 +T p,i )/2]×10 3
calculating the average evaporation heat delta H of the water evaporation of the drying cylinder with the number i ev,i ，
Wherein, phi=1-exp { -47.58[ (u) i-1 +u i )/2] 1.877 -0.10085[(T p,i-1 +T p,i )/2][(u i-1 +u i )/2] 1.0585 }；
(7) The following formula is used:
HEE = [Σ
(θ i πD c,i R CN,i ΔH ev,i /3600)/(ṁ s,SCS H s,SCS +ṁ s,AH H s,AH )]×100%
the thermal efficiency HEE of the drying part is obtained through calculation, the on-line real-time monitoring of the thermal efficiency of the drying part is realized,
wherein N represents the number of drying cylinders, i represents the number of drying cylinders, D c,i Represents the diameter, θ, of a dryer with the number i i The cylinder wrap angle coefficient is denoted by number i.
The quaternary partial differential equation set process model is as follows:
wherein m is ev,a = {exp[23.1934-3819.44/(T p +227.03)]·[1-exp(-47.58u 1.877 -0.10085T p u 1.0585 )]-exp[23.1934- 3819.44/(T a +227.03)]}/(T a +273.15)，ΔH ev = 46.544292·u 1.0585 ·
(T p +273.15) 2 ·{1/[1-exp(-47.58u 1.877 -0.10085T p u 1.0585 )]-1}+(2504.7-2.4789T p )·10 3 ；
Δ 1 And delta 2 For the coefficient related to the drying surface, delta if the drying surface at the monitoring point consists of cylinder-paper-wire-air 1 = FRF、Δ 2 =1, Δ if the drying surface at the monitoring point consists of cylinder-dry wire-paper-air or cylinder-paper-air 1 = 1、Δ 2 =1, Δ if the dry face at the monitoring point consists of air-paper-dry wire-air 1 = 1+FRF、Δ 2 =2, Δ if the dry face at the monitoring point consists of air-paper-air 1 = 2、Δ 2 =2, frf represents the dry-net influencing factor; r is R p And R is s R is the coefficient related to heat supply when the paper directly receives heat from steam supply p = h s-p (3816.44/(23.1934-lnP s )-227.03-T p ) Otherwise R p 0, R when the bag air directly receives heat from the steam supply s = h s-a (3816.44/(23.1934-lnP s )- 227.03-T a ) Otherwise R s Is 0;
u represents the paper humidity, T p Indicating paper temperature, AH a Representing absolute humidity of air in bag area, T a The air temperature of the bag area is represented, and t represents time;
C p,dp the specific heat value 1423.5J/(kg. DEG C) of the absolute dry paper is shown, C a The specific heat value of the absolute dry air is 1010J/(kg. DEG C), C v The specific heat value of water vapor is 1880J/(kg. DEG C.), and gamma 0 Represents the latent heat of vaporization of water at 0℃under normal atmospheric pressure at a constant value of 2501000J/kg, C p,w = 0.0139(T p /℃) 2 -1.3129 (T p Heat per degree centigrade) +4206.1 for water, Ɛ for air distribution coefficient of ventilator to corresponding dryer group air supply, m a,sup Represents the air supply quantity L of the ventilation and waste heat recovery subsystem y Indicating the width of the paper machine, h s-p Represents the convective heat transfer coefficient between steam and paper, h s-a Represents the convective heat transfer coefficient between steam and pocket air, h p-a Representing the convective heat transfer coefficient between the paper and pocket air, R v The gas constant is 461.5J/(kg. DEG C.), K p-a Representing the sheet-air contact surface to flow coefficient.
The dryer section of a paper machine consists of cylinders, which are typically arranged in a single-wire or double-wire configuration (as shown in fig. 1-a). The single-hanging structure only uses one dry net, paper is tightly attached to the dry net to move together, and the upper and lower rows of drying cylinders of the double-hanging structure respectively use different dry nets. The drying interface of the paper sheet during drying in the cylinders is different according to the arrangement and mounting position of the cylinders (table 1), and the cylinders can be subdivided into different drying zones according to the drying interface (as shown in fig. 1-b and 1-c).
Table 1 analysis of drying interfaces of different cylinders
(a)Description: c-drying cylinder; p-paper; f, drying the net; a-air
Thus, the cylinders can be divided into 6 general categories, namely: (1) a single-hanging upper-row heat supply drying cylinder (comprising 2 drying areas), (2) a single-hanging upper-row non-heat supply drying cylinder (comprising 2 drying areas), (3) a single-hanging lower-row heat supply drying cylinder (comprising 2 drying areas), (4) a single-hanging lower-row non-heat supply drying cylinder (comprising 2 drying areas), (5) a double-hanging heat supply drying cylinder (comprising 4 drying areas), (6) a double-hanging non-heat supply drying cylinder (comprising 4 drying areas).
Establishing paper machine dryer section material flow and usually with cylinders as separate unitsAn energy flow process model. For the phase1 drying area of a single-hanging upper-row heat supply dryer, delta 1 = FRF，Δ 2 =1，R p = h s-p (3816.44/(23.1934- lnP s )-227.03-T p )，R s = h s-a (3816.44/(23.1934- lnP s )-227.03-T a ) The method comprises the steps of carrying out a first treatment on the surface of the phase2 drying zone delta 1 = 1+FRF，Δ 2 = 2，R p = 0，R s = h s-a (3816.44/(23.1934-lnP s )-227.03-T a ). For a phase1 drying area of a single-hanging upper-row non-heating dryer, delta 1 = FRF，Δ 2 =1，R p = 0，R s =0; phase2 drying zone delta 1 = 1+FRF，Δ 2 = 2，R p = 0，R s =0. For the phase1 drying area of a single-hanging lower-discharging heat supply dryer, delta 1 = 1，Δ 2 =1，R p = h s-p (3816.44/(23.1934-lnP s )-227.03-T p )，R s = h s-a (3816.44/ (23.1934-lnP s )-227.03-T a ) The method comprises the steps of carrying out a first treatment on the surface of the phase2 drying zone delta 1 = 1+FRF，Δ 2 = 2，R p = 0，R s = h s-a (3816.44/(23.1934-lnP s )-227.03-T a ). For a phase1 drying area of a single-hanging lower-row non-heating dryer, delta 1 = 1，Δ 2 =1，R p = 0，R s =0; phase2 drying zone delta 1 = 1+FRF，Δ 2 = 2，R p = 0，R s =0. For the phase1 and phase3 drying zones of a double-hung heat supply dryer, delta 1 = 1，Δ 2 =1，R p = h s-p (3816.44/ (23.1934-lnP s )-227.03-T p )，R s = h s-a (3816.44/(23.1934- lnP s )-227.03-T a ) The method comprises the steps of carrying out a first treatment on the surface of the phase2 drying zone, delta 1 = FRF，Δ 2 =1，R p = h s-p (3816.44/ (23.1934-lnP s )-227.03-T p )，R s = h s-a (3816.44/(23.1934- lnP s )-227.03-T a ) The method comprises the steps of carrying out a first treatment on the surface of the phase4 drying zone, delta 1 = 2，Δ 2 = 2，R p = 0，R s = h s-a (3816.44/(23.1934-lnP s )-227.03-T a ). For double hangingPhase1 and phase3 drying zones, delta, of a heated dryer 1 = 1，Δ 2 =1，R p = 0，R s =0; phase2 drying zone, delta 1 = FRF，Δ 2 =1，R p = 0，R s =0; phase4 drying zone, delta 1 = 2，Δ 2 = 2，R p = 0，R s = 0。
The following describes the establishment of a process model by taking a single-hanging upper-exhaust heat supply dryer Phase1 drying interface as an example:
(1) Conservation of paper element mass
Taking any tiny unit of paper in the running direction of the paper in a Phase1 drying interface, wherein the length is
The shaded surface represents the surface of the paper covered by the dry wire. As shown in fig. 2, the water mass conservation in the paper microelements, namely the water change rate of the paper microelements = the mass of water brought into the microelements by the paper in unit time-the mass of water brought out of the microelements by the paper in unit time-the mass of water evaporated by the paper in unit time, namely dm w /dt = ṁ dp u| x0 - ṁ dp u| x0+Δx - ṁ ev,f L y Δx, ṁ therein dp Represents the absolute dry mass per unit time passing through the paper primordia, available formula ṁ dp = G dp L y V/60 calculation.
Wherein u represents the paper moisture, m w Represents the quality of water in paper microelements ṁ ev,f Represents the evaporation rate of water on the surface of the paper covered by the dry net, G dp Indicating absolute dry basis of paper, L y The web width is indicated, and V is the speed of the machine.
Assuming steady operation of the machine, i.e. dm w With/dt=0, the above two formulas can be simplified as: du/dx= -60 ṁ ev,f / G dp V。
Since dx=vdt/60, t represents the drying time, then: du/dt= - ṁ ev,f /G dp 。
(2) Paper infinitesimal energy conservation
As shown in fig. 3, by the conservation of paper infinitesimal energy,namely the energy change rate of the paper micro-element = the energy of the paper brought into the micro-element in unit time-the energy of the paper brought out of the micro-element in unit time + the heat absorbed by the paper micro-element to the outside in unit time-the heat released by the paper micro-element to the outside in unit time-the heat taken away by the evaporation of the water of the paper in unit time, namely d (m) p C p,p T p )/dt = (ṁ p C p,p T p )| x0 - (ṁ p C p,p T p ) | x0+Δx + (Q s-p - Q p-f-a -ṁ ev,f ΔH ev )L y Δx。
Wherein T is p Represents the paper temperature, m p Representing paper quality in a infinitesimal ṁ p Representing the mass of passing paper units per unit time, C p,p Represents the specific heat of paper, Q s-p Represents the micro-element absorption of heat transferred from steam, Q p-f-a Represents the heat transfer rate between the surface of the paper microelements coated by the dry net and the air, ṁ ev,f Represents the evaporation rate of water from the surface of the paper covered by the dry wire, ΔH ev Represents the heat of evaporation, L y Represent the breadth, ṁ dp Representing absolute dry mass of paper passing through primordial in unit time, C p,dp The specific heat value 1423.5J/(kg ℃) of the absolute dry paper and C p,w Specific heat of water is temperature dependent.
Assuming steady operation of the machine, i.e. d (m p C p,p T p ) If/dt=0, the energy conservation equation can be reduced to: d (ṁ) p C p, p T p )/dx = (Q s-p -Q p-f-a - ṁ ev,f ΔH ev )L y 。
Due to ṁ p Usable ṁ p = ṁ dp (1+u) calculation, C p,p Usable C p,p = (C p,dp +uC p,w ) Calculation of/(1+u), ṁ dp Usable ṁ dp = G dp L y V/60 calculation, so d (ṁ) p C p,p T p )/dx = G dp L y (V/60)d((C p,dp + uC p,w )T p )/dx。C p,dp Take on a fixed value, i.e. d ((C) p,dp )/dx = 0, so the above formula can be further simplified to d (ṁ) p C p,p T p ) /dx = G dp L y (V/60)[C p,dp (dT p /dx)+d(uC p,w T p )/dx]. The derivative formula is utilized to obtain: d (uC) p,w T p )/dx = -(C p,w T p ṁ ev,f )/[G dp (V/60)]+ [uT p (dC p,w /dT p ) + uC p,w ](dT p /dx), d (ṁ) p C p,p T p )/dx = -L y C p,w T p ṁ ev,f + G dp L y (V/60)[C p,dp + uT p (dC p,w /dT p ) + uC p,w ](dT p /dx)。
so-L y C p,w T p ṁ ev,f + G dp L y (V/60)[C p,dp + uT p (dC p,w /dT p ) + uC p,w ](dT p /dx) = (Q s-p - Q p-f-a -ṁ ev,f ΔH ev )L y I.e. dT p /dx = [Q s-p -Q p-f-a -ṁ ev,f (ΔH ev -C p,w T p )]/{G dp (V/60)[uT p (dC p,w / dT p )+C p,dp + uC p,w ]}。
Since dx= (V/60) dt, t represents the drying time, the above formula can also be expressed as: dT (dT) p /dt = [Q s-p -Q p-f-a -ṁ ev,f (ΔH ev - C p,w T p )]/{G dp [ uT p (dC p,w /dT p ) +C p,dp + uC p,w ]}。
(3) Bag region air infinitesimal mass conservation analysis
Taking the air microelements corresponding to the paper microelements as a research object, as shown in figure 4, the moisture mass conservation in the air microelements, namely the moisture change rate of the air microelements = the mass of water brought into the microelements by the air in unit time-the mass of water brought out of the microelements by the air in unit time + the mass of water evaporated by the paper microelements in unit time, namely d (m) da AH a )/dt = ṁ da AH a | x0 -ṁ da AH a | x0+Δx +ṁ ev,f L y Δx。
In AH of a Represents the absolute humidity of air, m da Represents the mass of absolute dry air in the infinitesimal ṁ ev,f Represents the evaporation rate of water on the surface of paper covered by a dry wire, ṁ da Represents absolute dry air mass per unit time passing through infinitesimal, L y Representing the breadth.
Assuming steady operation of the machine, i.e. d (m da AH a ) /dt=0, the above formula can be reduced to: dAH a /dx = ṁ ev,f L y / ṁ da 。
Assuming that the pocket supply air is all over the surface, ṁ da = G da L y (V/60)= ṁ sup ，ṁ sup Indicating the air supply rate of the bag area G da The absolute air quantity passing through the paper surface per unit area is shown. Then: dAH a /dx = ṁ ev,f /G da (V/60)。
Since dx= (V/60) dt, t represents the drying time, the above formula can also be expressed as: dAH a /dt = ṁ ev,f /G da 。
(4) Bag region air infinitesimal energy conservation analysis
Air microcell energy conservation was analyzed as shown in fig. 5. The conservation of energy of air microelements, namely the energy change rate of the air microelements = the energy of air brought into the microelements in unit time-the energy of air brought out of the microelements in unit time + the heat absorbed by the air microelements in unit time to the outside-the heat released by the air microelements in unit time to the outside + the heat of the water vapor evaporated from paper in unit time, namely d (m) da H a )/dt = ṁ da H a | x0 -ṁ da H a | x0+Δx +(Q s-a + Q p-f-a +ṁ ev,f ΔH ev )L y Δx。
Wherein m is da Represents absolute dry air quality in infinitesimal, H a Representing the enthalpy of humid air, Q s-a Represents the air element absorbs the heat transferred from the steam, Q p-f-a Representation ofThe air microelements absorb heat, delta H, transferred from the surface of the paper covered by the dry mesh ev Represents the heat of evaporation, L y Representing the breadth.
Assuming steady operation of the machine, i.e. d (m da H a ) /dt=0, the above formula can be simplified as: dH (dH) a /dx = (Q s-a +Q p-f-a + ṁ ev,f ΔH ev )/G da (V/60)。
H a The calculation can be made by the following formula: h a = (C a +C v x a )T a +γ 0 AH a ，C a The specific heat of the absolute dry air is 1010J/kg, C v Represents the specific heat value 1080J/kg and gamma of steam 0 Represents the latent heat of vaporization of water at 0℃under normal atmospheric pressure at a value of 2501000J/kg. dH therefore a /dx = (C a +C v AH a )(dT a /dx) + (C v T a +γ 0 ) (dAH a /dx) = (C a +C v AH a )(dT a /dx) + (C v T a +γ 0 )ṁ ev,f /G da (V/60)。
Therefore (C) a +C v AH a )(dT a /dx) + (C v T a +γ 0 )ṁ ev,f /G da (V/60) = (Q s-a -Q p-f-a +ṁ ev,f ΔH ev )/ G da (V/60), dT a /dx = {Q s-a +Q p-f-a +ṁ ev,f [ΔH ev -(C v T a +γ 0 )]}/[G da (V/60)(C a +C v AH a )]。
Since dx= (V/60) dt, t represents the drying time, the above formula can also be expressed as: dT (dT) a /dt = {Q s-a + Q p-f-a +ṁ ev,f [ΔH ev -(C v T a +γ 0 )]}/[G da (C a +C v AH a )]。
In summary, the mathematical model of the single-hang upper exhaust heat-supplying dryer Phase1 drying interface can be expressed as a quaternary partial differential equation set, as follows:
wherein u represents the humidity of the paper, T p Indicating paper temperature, AH a Indicating absolute humidity of air in bag area T a The air temperature of the bag area is represented, t represents time, and C p,dp The specific heat value 1423.5J/(kg ℃) of the absolute dry paper and C p,w = 0.0139(T p /℃) 2 -1.3129(T p Heat of water in relation to temperature, C is represented by/. Degree.C) +4206.1 a The specific heat of the absolute dry air is 1010J/kg, C v Represents the specific heat value 1080J/kg and gamma of steam 0 Represents the latent heat of vaporization of water at 0℃under normal atmospheric pressure at a value of 2501000J/kg.
G dp The absolute dry basis of the paper is indicated. Quantitative BW of paper which can be collected 0 And water content W 0 Data estimation, G dp = BW 0 (1-W 0 /100)。
G da Represents the absolute dry air supply quantity passing through the unit area paper surface, and the collected air supply quantity m of the air supply machine can be used a,sup Humidity AH of air supply a And vehicle speed V estimation, G da = 60Ɛm a,sup /[BV(1+AH a )]Ɛ shows the distribution coefficient of the air quantity of the ventilator to the corresponding drying cylinder group, Ɛ is 0-1, and B shows the width of the paper machine.
ṁ ev,a Indicating the rate of evaporation of water from the surface of the paper in direct contact with air, ṁ can be used ev,a = K p-a (P vp -P va )/ [R v (T a +273.15)]And (5) estimating. R is R v The gas constant is 461.5J/(kg. DEG C.), T a Is the air temperature of the bag region, K p-a Is the sheet-air contact surface to sheet coefficient of flow. Partial pressure of water vapor P on paper surface vp Can be controlled by the paper temperature T p And humidity u estimation, P vp = exp[23.1934-3819.44/(T p +227.03)]·[1-exp(-47.58u 1.877 - 0.10085T p u 1.0585 )]. Partial pressure of air and water vapor P in bag region va Can be controlled by the air temperature T of the bag region a Estimating P va = exp(23.1934-3819.44/(T p + 227.03))。ṁ ev,f Representing the rate of evaporation of water from the surface of the paper covered by the dry wire, the rate of evaporation of water ṁ from the surface of the paper that can be used directly in contact with air ev,a Estimation ṁ ev,f =FRF· ṁ ev,a FRF is a dry net influence factor, and takes a value of 0.3-0.5.
Q s-p Indicating the heat flux of the paper absorbed by the steam, the usable steam temperature T s And paper temperature T p Estimating Q s-p = h s-p (T s -T p )，h s-p Representing the convective heat transfer coefficient between the steam and the paper. Q (Q) s-a Indicating the temperature T of the available steam when the air in the bag absorbs the heat flux from the steam s And pocket air temperature T a Estimating Q s-a = h s-a (T s -T a )，h s-a Representing the convective heat transfer coefficient between the vapor and the pocket air. Q (Q) p-a Representing the heat flux of the paper directly transferred to the air by the air contact surface, Q p-f-a The heat transfer flux between the surface of the paper covered by the dry net and the air can be represented by the paper temperature T p And pocket air temperature T a Estimating Q p-a = Q p-f-a =h p-a (T p -T a )，h p-a Representing the convective heat transfer coefficient between the paper and the pocket air.
ΔH ev Indicating heat of evaporation, usable sheet temperature T p And humidity u estimation, ΔH ev = ΔH sorp + ΔH lat . Wherein DeltaH sorp =461.52 [(1-φ)/φ]0.10085u 1.0585 (T p +273.15) 2 ，ΔH lat = (2504.7- 2.4789 T p )·10 3 。φ =1-exp(-47.58u 1.877 -0.10085T p u 1.0585 )。
And (3) introducing an estimation formula of the variables in the equation set into the equation set to obtain a quaternary partial differential equation set consisting of the available variables to be solved, the online measurable variables and the constants, wherein the quaternary partial differential equation set comprises the following specific steps of:
wherein m is ev,a = {exp[23.1934-3819.44/(T p +227.03)]·[1-exp(-47.58u 1.877 -0.10085T p u 1.0585 )]-exp[23.1934-3819.44/(T a +227.03)]}/(T a +273.15)，ΔH ev = 46.544292·u 1.0585 ·
(T p +273.15) 2 ·{1/[1-exp(-47.58u 1.877 -0.10085T p u 1.0585 )]-1}+(2504.7-2.4789T p )·10 3 ，
R p = h s-p (3816.44/(23.1934-lnP s )-227.03-T p )，R s = h s-a (3816.44/(23.1934-lnP s )- 227.03-T a )；
FRF represents dry net influence factor, u represents paper humidity, T p Indicating paper temperature, AH a Indicating absolute humidity of air in bag area T a The air temperature of the bag area is represented, and t represents time;
C p,dp the specific heat value 1423.5J/(kg. DEG C) of the absolute dry paper is shown, C a The specific heat value of the absolute dry air is 1010J/(kg. DEG C), C v The specific heat value of water vapor is 1880J/(kg. DEG C.), and gamma 0 Represents the latent heat of vaporization of water at 0℃under normal atmospheric pressure at a constant value of 2501000J/kg, C p,w = 0.0139(T p /℃) 2 -1.3129 (T p Heat per degree centigrade) +4206.1 for water, Ɛ for air distribution coefficient of ventilator to corresponding dryer group air supply, m a,sup Represents the air supply quantity L of the ventilation and waste heat recovery subsystem y Indicating the width of the paper machine, h s-p Represents the convective heat transfer coefficient between steam and paper, h s-a Represents the convective heat transfer coefficient between steam and pocket air, h p-a Representing the convective heat transfer coefficient between the paper and pocket air, R v The gas constant is 461.5J/(kg. DEG C.), K p-a Representing the sheet-air contact surface to flow coefficient.
Mathematical models of different drying interfaces of other types of cylinders are equally available.
An on-line monitoring method of the papermachine's dryer section energy efficiency of the present application is described further below with reference to specific embodiments.
Examples
The test object is a paper machine dryer section for producing corrugated paper, the design capacity is 10 ten thousand tons/year, the design speed is 500m/min, the breadth is 4m, and the main production ration is 105-145 g/m 2 Corrugated paper. The paper machine employs a double-row multiple-cylinder dryer section, a total of 48 cylinders (see FIG. 6 for details), each cylinder 1.5m in diameter equipped with a spoiler bar and a fixed siphon. The steam condensate subsystem adopts typical three-section pressure reduction, a dryer # 23 to a dryer #48 is a main steam section (I section), a dryer # 10 to a dryer # 22 is an intermediate steam section (II section), and a dryer # 1 to a dryer #9 are wet section steam sections (III section). The ventilation and waste heat recovery subsystem adopts a closed gas hood.
The types of cylinders are shown in the following table:
on-line collecting paper machine speed V and paper-forming quantitative BW o Moisture W of paper o On-line collecting humidity u of paper at inlet of monitoring part 0 And temperature T p,0 Air supply quantity m of ventilation and waste heat recovery subsystem at on-line acquisition monitoring part a,sup Temperature T of air supply a,sup Absolute humidity AH of supply air a,atm Data, on-line acquisition and monitoring of steam pressure P of steam condensate subsystem at part s Data.
The values of the real-time acquisition variables at a certain moment are recorded as shown in the following table.
Ɛ shows the distribution coefficient of the air quantity of the ventilator to the corresponding drying cylinder group, and the fixed value 0.0208 is taken; l (L) y Representing the width of the paper machine, taking fixed values of 4m and h s-p The convection heat transfer coefficient between the steam and the paper is expressed, and the fixed value is 1000W/(m) 2 ℃)；h s-a Indicating that the steam and bag area are emptyThe convection heat transfer coefficient between gases is set to be 20W/(m) 2 ℃)；h p-a The convection heat transfer coefficient between the paper and the air in the bag area is represented, and the fixed value is 30W/(m) 2 ℃)；R v The gas constant is 461.5J/(kg. DEG C.), K p-a The convective mass transfer system of the paper-air contact surface is shown, and the fixed value is 0.02m/s.
The paper complies with the law of conservation of materials and energy in the drying process of the drying part, 6 types of different drying cylinders (a single hanging upper row heating drying cylinder, a single hanging lower row heating drying cylinder, a single hanging upper row non-heating drying cylinder, a single hanging lower row non-heating drying cylinder, a double hanging heating drying cylinder and a double hanging non-heating drying cylinder) are established based on the law, and the paper temperature T at the monitoring point of the drying part is set up p And the humidity u and the temperature T of air in the bag area at the monitoring point a And absolute humidity AH a And (3) a process model of a quaternary partial differential equation set with unknown quantity, and sequentially combining 48 dryer process models into a process model of a dryer section.
Paper moisture u at dryer section inlet 0 And temperature T p,0 Air supply temperature T of ventilation and waste heat recovery subsystem at 1 st drying cylinder a,sup Absolute humidity AH of supply air a,atm At the initial value, the steam pressure P of the steam condensate subsystem at the 1 st drying cylinder s,1 As boundary conditions, a quaternary partial differential equation system of a 1 st drying interface of a 1 st drying cylinder is numerically solved by adopting a range-Kutta method, so that the paper temperature T at the outlet of the 1 st drying interface of the 1 st drying cylinder can be obtained in real time p,1 And humidity mu 1 And temperature T of air in bag region at 1 st drying interface a,1 And absolute humidity AH a ,1 Data.
Then the solved paper humidity mu at the outlet of the 1 st drying interface 1 And temperature T p,1 And the air supply temperature T of the ventilation and waste heat recovery subsystem at the 2 nd drying interface dryer a,sup Absolute humidity AH of supply air a,atm At the initial value, the steam pressure P of the steam condensate subsystem at the dryer with the 2 nd drying interface s,2 The 2 nd drying can be obtained in real time by adopting a quaternary partial differential equation system of the 2 nd drying interface which is numerically solved by a Runge-Kutta method as a boundary conditionPaper temperature T at interface outlet p,2 And humidity mu 2 And the temperature T of the air in the bag area at the 2 nd drying interface a,2 And absolute humidity AH a,2 Data. Similarly, the paper temperature T at the exit position of each drying interface at that time p And humidity μ and temperature T of pocket air a And humidity AH a Can be obtained by real-time calculation, thereby realizing on-line monitoring. The temperature and humidity curves of the paper at different drying cylinders and the temperature and humidity curves of the air in the bag area are drawn based on the calculated data obtained at the drying interface where the drying cylinder is in direct contact with the paper or the drying net, and are shown in fig. 7, 8, 9 and 10 in detail.
Temperature T of paper by portable equipment p And humidity μ and temperature T of pocket air a And absolute humidity AH a And carrying out online measurement on the data, and verifying the accuracy of an online monitoring method. Because of the limitation of the test space, the measurement difficulty is high, and only part of the positions of the drying cylinders are tested. The actual test result is very close to the online monitoring result, and the online monitoring method is accurate and reliable.
Using formula R CN,i = 60·V·BW 0 ·(1-W 0 /100)·(u i-1 -u i )/(θ i πD c,i ) Calculating and obtaining the output R of each drying cylinder CN,i The on-line real-time monitoring of the output index of each drying cylinder of the drying part is realized, and the result is shown in figure 12;
using the formula SSC p = 60(ṁ s,SCS +ṁ s,AH )/(V·BW 0 B) calculating the steam unit consumption SSC of the drying section p Realizing the online real-time monitoring of the steam unit consumption of the drying part and utilizing the formula delta H ev,i =46.544292(1/φ-1) [(u i-1 +u i )/2] 1.0585 [(T p,i-1 +T p,i )/2+273.15] 2 +[2504.7-2.4789 (T p,i-1 +T p,i )/2]×10 3 Calculating to obtain average evaporation of water evaporation of drying cylinder with number iHeat ΔH ev,i Wherein, phi=1-exp { -47.58[ (u) i-1 +u i ) /2] 1.877 -0.10085[(T p,i-1 +T p,i )/2][(u i-1 +u i )/2] 1.0585 -a }; reuse formula hee= [ Σ ]
(θ i πD c,i R CN,i ΔH ev,i /3600)/(ṁ s,SCS H s,SCS +ṁ s,AH H s,AH )]And (5) calculating to obtain the heat efficiency HEE of the drying part by 100%, and realizing online real-time monitoring of the heat efficiency of the drying part.
The results are shown in the following table
| Energy efficiency index | Steam unit consumption SSC p （kg/kg） | Heat efficiency of drying section HEE (%) |
| Numerical value | 1.41 | 56 |
From the analysis of the result of energy efficiency index monitoring, the steam unit consumption of the production line of the embodiment is 1.41kg/kg, which is equivalent to 184.71kgce/t paper of standard coal, and the advanced level of the national standard of the energy consumption limit of the pulping and papermaking unit product is reached (GB 1825-2015).
From the process technological parameter monitoring analysis, the embodiment production line has the space for further energy conservation and consumption reduction:
(1) As can be seen from the dryer output curve (fig. 12), the last 8 dryer of the example line hardly evaporates water, and can therefore be closed, saving steam consumption. The same phenomenon can be seen from the paper moisture curve (fig. 7), with little change in paper moisture at the dryer positions 40 and beyond.
(2) As can be seen from the paper humidity curve (fig. 7), the moisture content of the paper at the outlet of the drying part of the production line of the embodiment is close to 0, and the excessive drying phenomenon occurs, so that excessive evaporation of moisture can cause brittleness of the paper and decrease of physical properties besides energy waste.
(3) In the embodiment, the drying cylinders 16, 23, 28, 34, 41, 42 and 43 have lower bag temperature, which is related to reasons such as steam leakage and the like, and the drying cylinders should be maintained as soon as possible, otherwise, the dripping phenomenon is easily caused, and the overall heat efficiency of the drying part is affected.
The above is only a specific embodiment of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent substitutions or modifications made on the basis of the present invention to achieve substantially the same technical effects are included in the scope of the present invention.
The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description. The above examples illustrate only a few embodiments of the invention, which are described in detail and are not to be construed as limiting the scope of the invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention. Accordingly, the scope of protection of the present invention is to be determined by the appended claims.
Claims (2)
1. An online monitoring method for energy efficiency of a drying part of a paper machine is characterized by comprising the following steps:
(1) Real-time on-line acquisition of paper machine speed V and paper forming ration BW o Moisture W of paper o Collecting the humidity u of paper at the inlet of the drying part on line in real time 0 And temperature T p,0 Air supply quantity m of each drying cylinder of real-time online collection ventilation and waste heat recovery subsystem a,sup,i Temperature T of air supply a,sup,i Absolute humidity AH of supply air a,atm,i Data, and collecting steam pressure of each drying cylinder of steam condensate subsystem on line in real timeP s,i Data, real-time online acquisition of the amount of steam consumed per unit time ṁ by the steam-condensate subsystem s,SCS And enthalpy H of consumption of steam s,SCS Data, ṁ of steam consumption per unit time of air heating module in ventilation and waste heat recovery subsystem is collected online in real time s,AH And enthalpy H of consumption of steam s,AH Data, wherein i represents a cylinder number;
(2) Based on the conservation of materials and energy in the drying process of the paper in the drying part, a process model is established, wherein the process model is based on the temperature T of the paper p And humidity u, temperature T of bag air a And absolute humidity AH a For the unknown quantity and the quaternary partial differential equation system taking the data acquired in the step (1) as the known quantity, the temperature T of the paper at the outlet of each drying cylinder key process parameter drying cylinder of the drying part is realized by solving the equation system p,i And humidity u i Temperature T of air in dryer pocket a,i And absolute humidity AH a,i Wherein i represents the cylinder number;
(3) The following formula is used:
T c,i = {T s,i /[(1/α s-c )+(d c,i /k c,i )]+θ i h c-p T p,i +(1-θ i )h c-a T a,i }/{1/[(1/α s-c )+(d c,i /k c,i )]+θ i h c-p +(1-θ i )h c-a } （1）
T c,i = [θ i h c-p T p,i +(1-θ i )h c-a T a,i ]/[θ i h c-p +(1-θ i )h c-a ] （2）
each of the calculated resultsSurface temperature T of individual drying cylinders c,i The formula (1) is a calculation formula of a heated drying cylinder, the formula (2) is a calculation formula of a non-heated drying cylinder, the on-line real-time monitoring of the surface temperature of each drying cylinder key process parameter of the drying part is realized,
wherein T is s,i Representing the temperature of steam in a dryer, and using T s,i = [3816.44/(23.1934-lnP s,i )]-a 227.03 calculation of the number of points,
wherein i represents the cylinder number, θ i Represents the cylinder wrap angle coefficient, alpha, numbered i s-c Represents the condensing heat transfer coefficient, d c,i Represents the dryer wall thickness, k, numbered i c,i Represents the heat conductivity of the dryer wall, h, numbered i c-p Represents the contact heat transfer coefficient between the drying cylinder and the paper, h c-a T represents the convection heat transfer coefficient between the drying cylinder and the air in the bag area a,i The air temperature of the drying cylinder bag area with the number i is represented by T p,i Representing the paper temperature at the dryer numbered i;
(4) The following formula is used:
R CN,i = 60·V·BW 0 ·(1-W 0 /100)·(u i-1 -u i )/(θ i πD c,i )
calculating and obtaining the output R of each drying cylinder CN,i Realizes the on-line real-time monitoring of the output index of each drying cylinder of the drying part,
wherein i represents the number of the drying cylinder, u i Represents the paper humidity at the outlet of a dryer with dryer number i, u i-1 Represents the paper humidity at the outlet of a dryer with the dryer number i-1, and u is when i is 1 i-1 I.e. u 0 ，D c,i Represents the diameter, theta, of the ith dryer cylinder i A dryer wrap angle coefficient with the number i;
(5) The following formula is used:
SSC p = 60(ṁ s,SCS +ṁ s,AH )/(V·BW 0 ·B)
calculating to obtain steam unit consumption SSC of drying part p Realizes the online real-time monitoring of the steam unit consumption of the drying part,
wherein B represents the width of the paper machine;
(6) The following formula is used:
ΔH ev,i =46.544292(1/φ-1)[(u i-1 +u i )/2] 1.0585 [(T p,i-1 +T p,i )/2+273.15] 2 +[2504.7-2.4789(T p,i-1 +T p,i )/2]×10 3
calculating the average evaporation heat delta H of the water evaporation of the drying cylinder with the number i ev,i ，
Wherein, phi=1-exp { -47.58[ (u) i-1 +u i )/2] 1.877 -0.10085[(T p,i-1 +T p,i )/2][(u i-1 +u i )/2] 1.0585 }；
(7) The following formula is used:
HEE = [Σ 
(θ i πD c,i R CN,i ΔH ev,i /3600)/(ṁ s,SCS H s,SCS +ṁ s,AH H s,AH )]×100%
the thermal efficiency HEE of the drying part is obtained through calculation, the on-line real-time monitoring of the thermal efficiency of the drying part is realized,
wherein N represents the number of drying cylinders, i represents the number of drying cylinders, D c,i Represents the diameter, θ, of a dryer with the number i i The cylinder wrap angle coefficient is denoted by number i.
2. An on-line monitoring method of energy efficiency of a dryer section of a paper machine as in claim 1, wherein said quaternary partial differential equation set process model is as follows:
wherein m is ev,a = {exp[23.1934-3819.44/(T p +227.03)]·[1-exp(-47.58u 1.877 -0.10085T p
u 1.0585 )]-exp[23.1934- 3819.44/(T a +227.03)]}/(T a +273.15)，ΔH ev = 46.544292·u 1.0585 ·
(T p +273.15) 2 ·{1/[1-exp(-47.58u 1.877 -0.10085T p u 1.0585 )]-1}+(2504.7- 2.4789T p )·10 3 ；
Δ 1 And delta 2 For the coefficient related to the drying surface, delta if the drying surface at the monitoring point consists of cylinder-paper-wire-air 1 = FRF、Δ 2 =1, Δ if the drying surface at the monitoring point consists of cylinder-dry wire-paper-air or cylinder-paper-air 1 = 1、Δ 2 =1, Δ if the dry face at the monitoring point consists of air-paper-dry wire-air 1 = 1+FRF、Δ 2 =2, Δ if the dry face at the monitoring point consists of air-paper-air 1 = 2、Δ 2 =2, frf represents the dry-net influencing factor; r is R p And R is s R is the coefficient related to heat supply when the paper directly receives heat from steam supply p = h s-p (3816.44/(23.1934-lnP s )-227.03-T p ) Otherwise R p 0, R when the bag air directly receives heat from the steam supply s = h s-a (3816.44/(23.1934-lnP s )- 227.03-T a ) Otherwise R s Is 0;
u represents the paper humidity, T p Indicating paper temperature, AH a Indicating absolute humidity of air in bag area T a The air temperature of the bag area is represented, and t represents time;
C p,dp the specific heat value 1423.5J/(kg. DEG C) of the absolute dry paper is shown, C a The specific heat value of the absolute dry air is 1010J/(kg. DEG C), C v The specific heat value of water vapor is 1880J/(kg. DEG C.), and gamma 0 Represents the latent heat of vaporization of water at 0℃under normal atmospheric pressure at a constant value of 2501000J/kg, C p,w = 0.0139(T p /℃) 2 -1.3129 (T p Heat per degree centigrade) +4206.1 for water, Ɛ for air distribution coefficient of ventilator to corresponding dryer group air supply, m a,sup Represents the air supply quantity L of the ventilation and waste heat recovery subsystem y Representing the width of the paper machine，h s-p Represents the convective heat transfer coefficient between steam and paper, h s-a Represents the convective heat transfer coefficient between steam and pocket air, h p-a Representing the convective heat transfer coefficient between the paper and pocket air, R v The gas constant is 461.5J/(kg. DEG C.), K p-a Representing the sheet-air contact surface to flow coefficient.
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Application publication date: 20201113 Assignee: ZHEJIANG ZHEFENG NEW MATERIAL Co.,Ltd. Assignor: QUZHOU University Contract record no.: X2024980000752 Denomination of invention: An online monitoring method for energy efficiency in the drying section of paper machines Granted publication date: 20230602 License type: Common License Record date: 20240115 |