A control method for improving waste heat utilization amount of a waste heat boiler

Abstract

A control method for improving the waste heat utilization of a waste heat boiler, belonging to the field of waste heat boiler automatic control technology, includes the following steps: Step S01: The upper and lower limits of the controlled variable, the upper and lower limits of the control variable, and the upper and lower limits of the control variable increment are used by the main controller of the waste heat boiler to calculate the increase or decrease value of the waste heat regulating valve; Step S02: The waste heat optimization controller determines the remaining waste heat and increases the waste heat utilization rate by maximizing the opening of the waste heat regulating valve; Step S03: The waste heat regulating valve outputs an incremental value OUT every cycle. ΔV1 (k) Increase the step size; Step S04: The mixed heat controller controls the waste heat regulating valve V1 and the cold air regulating valve V2. This invention can increase the utilization of waste heat from the waste heat boiler, enabling more recovered heat to be obtained while maintaining a stable production process, thereby improving economic efficiency.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of automatic control of waste heat boiler, and particularly relates to a control method for improving waste heat utilization of waste heat boiler. BACKGROUND

[0002] The waste heat boiler refers to a boiler using waste heat in exhaust gas in various industrial production processes as heat to heat water to a certain temperature or convert water into low-pressure steam or medium-pressure steam. A common waste heat boiler, such as a cement kiln waste heat boiler, has a schematic diagram as shown in Figure 1 The boiler uses waste heat at a kiln head of a cement rotary kiln as a heat source to heat water into low-pressure steam and medium-pressure steam for use in a factory. Generally, within the design range of process waste heat boiler, the more waste heat obtained by the waste heat boiler, the more steam produced. The conventional control adopts a constant value control, the main purpose of which is to overcome disturbance, and in order to stabilize and ensure safe production, process variables of the waste heat boiler, such as drum pressure and steam pressure, are often controlled in a relatively 'conservative' range, which cannot maximize the utilization of waste heat, thus causing the waste heat boiler to be unable to maximize the utilization of waste heat, and further leading to energy waste. SUMMARY

[0003] Based on the above technical problem, the present application provides a control method for improving waste heat utilization rate of waste heat boiler, which comprises a waste heat boiler main controller, a waste heat optimization controller, a furnace temperature observer and a mixed heat controller. The method improves waste heat recovery amount of the waste heat boiler and increases economic benefits of the waste heat boiler under the premise of ensuring stability of drum pressure and main steam pressure.

[0004] To achieve the above technical purpose, the technical solution provided by the present application is as follows:

[0005] A control method for improving waste heat utilization amount of waste heat boiler, comprising the following steps:

[0006] Step S01: The waste heat boiler main controller selects drum pressure PT01 or main steam pressure PT02 as a controlled variable, selects a waste heat adjusting valve V1 as a control variable, sets upper and lower limits of the controlled variable, upper and lower limits of the control variable and upper and lower limits of an increment of the control variable, and calculates an increment or decrement of the waste heat adjusting valve V1 by using a model predictive control algorithm;

[0007] Step S02: The waste heat optimization controller judges a waste heat surplus according to a current opening degree of the waste heat adjusting valve V1 at an inlet of a furnace of the waste heat boiler and a current opening degree of a cold air adjusting valve V2 at the inlet of the furnace of the waste heat boiler, and continuously increases waste heat utilization rate by maximizing the opening degree of the waste heat adjusting valve V1 when the drum pressure PT01 and the main steam pressure PT02 are within the controlled upper and lower limits;

[0008] Step S03: The furnace temperature observer controls the waste heat regulating valve to output an incremental value OUT per cycle according to whether the furnace temperature TT02 is within the operating range ΔV1 (k) is the maximum incremental step SPEED1.

[0009] Step S04: The mixed heat controller controls the waste heat regulating valve V1 and the cold air regulating valve V2 simultaneously according to the main steam pressure PT02, the main steam flow FT01, the kiln head temperature TT01 and the furnace temperature TT02.

[0010] Further, the incremental / decremental value of the waste heat regulating valve V1 calculated in the step S01 is calculated by using a model predictive control algorithm M , and the control algorithm is as follows:

[0011]

[0012] s.t.

[0013]

[0014] u M (k) = u M (k-1) + Δu M (k)

[0015]

[0016] u min ≤ u M ≤ u m a x

[0017] Δu min ≤ Δu M (k) ≤ Δu m a x

[0018] wherein J represents a target function, w is a set value vector, is a predicted value, Q is an error weight coefficient matrix, u M is a control input, Δu M is a control input increment, R is a control weight coefficient matrix, is a predicted initial value, A is a dynamic matrix, y min and y max represent lower and upper limits of the controlled variable, u min and u max represent lower and upper limits of the control variable, Δu min and Δu max represent lower and upper limits of the control variable increment.

[0019] Further, the method of determining the remaining amount of waste heat in step S02 is as follows:

[0020] (1) The waste heat regulating valve V1 is not fully open;

[0021] (2) The opening degree of the cold air regulating valve V2 is less than the upper limit value of control;

[0022] (3) The value of the steam drum pressure PT01 is less than the upper limit value of control;

[0023] (4) The main steam flow FT01 does not reach the preset target value;

[0024] When the above conditions are met, the waste heat optimization controller outputs every 30 minutes according to the following algorithm:

[0025] IN set = 5 * (PT01 ENGH - PT01.PV) (Formula 2)

[0026]

[0027] Where IN set represents the incremental target value of the waste heat regulating valve, PT01.PV represents the measured value of the steam drum pressure, PT01 ENGH represents the upper limit value of the controlled steam drum pressure, OUT ΔV1 represents the incremental value of the waste heat regulating valve per cycle, T represents the time constant, k represents the current cycle, and k-1 represents the previous cycle.

[0028] Further, the specific method of step S03 is as follows:

[0029] According to the constraint upper limit TT02 ENGH of the furnace temperature TT02, the absolute value of the difference between the measured value TT02.PV and the measured value TT02.PV is ΔE TT02 , and OUT ΔV1 (k) is calculated using the following formula:

[0030] SPEED1 = min(ΔE TT02 / TT02 ENGH , SPEED 1max ) (Formula 4)

[0031] Where SPEED1 represents the maximum value of OUT ΔV1 (k) per step, and SPEED 1max is a preset value, with the maximum value of SPEED1 being SPEED 1max .

[0032] Further, the specific steps of step S04 are as follows:

[0033] (1) mixed heat controller increases or decreases the value of the waste heat adjusting valve according to the value calculated by the waste heat boiler main controller, and the output increment value OUT of the waste heat adjusting valve calculated by the waste heat optimization controller every period ΔV1 (k) and the output increment value OUT of the waste heat adjusting valve calculated by the furnace temperature observer every period ΔV1 (k) is the maximum increase step SPEED1, and the opening of the waste heat adjusting valve V1 is controlled;

[0034] OUT V1 (k) = OUT V1 (k-1) + Au M + OUT ΔV1 (k) (formula 5)

[0035] Wherein, OUT V1 represents the output value of V1 every period, Au M is the output value calculated in step S01, OUT ΔV1 is the output value calculated in step S02, the maximum value is SPEED1, and k represents the current period and k-1 represents the last period.

[0036] (2) the cold air valve V2 adopts single loop PID control furnace temperature TT02, and the kiln head temperature TT01 is used as feedforward, so that when the TT01 changes, the cold air valve V2 and the waste heat adjusting valve V1 can be adjusted in time, so as to overcome the influence of heat source disturbance on the waste heat boiler in time.

[0037] Compared with the prior art, the advantages and beneficial effects of the present application are as follows:

[0038] (1) the waste heat boiler main controller increases the constraint, and the controller finds the optimal value in the constraint, so that the control is safer and more stable.

[0039] (2) when the system is stable, the opening of the waste heat adjusting valve is continuously maximized, so that the waste heat recovery rate of the waste heat boiler is greatly improved.

[0040] The present application provides a control method for improving the waste heat utilization amount of a waste heat boiler, which can stabilize production and effectively improve the waste heat recovery amount of the waste heat boiler, so that the economic benefit of the waste heat boiler is further improved. Under the premise of ensuring the stability of the steam drum pressure and the main steam pressure, the waste heat recovery amount of the waste heat boiler is improved, the waste heat boiler is controlled to be "card edge", and greater economic benefit is obtained. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 is the production process intention of the waste heat boiler;

[0042] Figure 2 is the controller block diagram of the present application;

[0043] Figure 3The flowchart of the control method for improving waste heat utilization of a waste heat boiler. DETAILED DESCRIPTION

[0044] The specific implementation process of the present application will be specifically described below in combination with the drawings of the present application. Obviously, the described implementation process is only a part of examples of the present application, but not all examples.

[0045] The present application provides a control method for improving waste heat utilization of a waste heat boiler, as shown in the figure, comprising the following steps: Figures 2-3

[0046] Step S01: The waste heat boiler main controller selects the drum pressure PT01 or the main steam pressure PT02 as the controlled variable, and the waste heat regulating valve V1 as the control variable, and sets the upper and lower limits of the controlled variable, the upper and lower limits of the control variable and the upper and lower limits of the control variable increment, and calculates the increment and decrement of the waste heat regulating valve V1 by using the model predictive control algorithm.

[0047] The increment and decrement of the waste heat regulating valve V1 calculated in the step S01 is the increment and decrement Δu M (k) of the waste heat regulating valve V1 calculated by using the model predictive control algorithm, and the control algorithm is as follows:

[0048]

[0049] s.t.

[0050]

[0051] u M (k)=u M (k-1)+Δu M (k)

[0052]

[0053] u min ≤u M ≤u m a x

[0054] Δu min ≤Δu M (k)≤Δu m a x

[0055] Wherein, J represents the objective function, w is the set value vector, is the predicted value, Q is the error weight coefficient matrix, u M is the control input, Δu M is the control input increment, R is the control weight coefficient matrix,​ To predict the initial value, A is a dynamic matrix, y min and y max represent the lower and upper limits of the controlled variable, u min and u max represent the lower and upper limits of the control variable, Δu min and Δu max represent the lower and upper limits of the control variable increment.

[0056] Step S02: The waste heat optimization controller determines the waste heat surplus according to the current opening of the waste heat boiler furnace inlet waste heat regulating valve V1 and the current opening of the waste heat boiler furnace inlet cold air regulating valve V2, and when the drum pressure PT01 and the main steam pressure PT02 are within the controlled upper and lower limits, the waste heat utilization rate is continuously increased by maximizing the opening of the waste heat regulating valve V1.

[0057] The method for determining the waste heat surplus in the step S02 is as follows:

[0058] (1) The waste heat regulating valve V1 is not fully opened;

[0059] (2) The opening of the cold air regulating valve V2 is less than the control upper limit value;

[0060] (3) The value of the drum pressure PT01 is less than the controlled upper limit value;

[0061] (4) The main steam flow FT01 does not reach the preset target value;

[0062] When the above conditions are met, the waste heat optimization controller outputs every 30 minutes according to the following algorithm:

[0063] IN set = 5 * (PT01 ENGH - PT01.PV) (Formula 2)

[0064]

[0065] Where, IN set represents the waste heat regulating valve increment target value, PT01.PV represents the measured value of the drum pressure, PT01 ENGH represents the controlled upper limit value of the drum pressure, OUT ΔV1 represents the waste heat regulating valve output increment value per cycle, T represents the time constant, k represents the current cycle, and k-1 represents the previous cycle.

[0066] Step S03: The furnace temperature observer controls the maximum increase step SPEED1 of the waste heat regulating valve output increment value OUT ΔV1 (k) per cycle according to whether the furnace temperature TT02 is within the operating range.

[0067] The specific method of the step S03 is as follows:

[0068] According to the constraint upper limit TT02 of the furnace temperature TT02 ENGH The absolute value of the difference between the measured value TT02.PV and the calculated value TT02 is ΔE TT02 OUT is calculated using the following formula ΔV1 (k) maximum increase step:

[0069] SPEED1 = min(ΔE TT02 / TT02 ENGH , SPEED 1max ) (Formula 4)

[0070] In the formula, SPEED1 represents the maximum value of OUT ΔV1 (k) each step output; SPEED 1max is a preset value, and the maximum value of SPEED1 is SPEED 1max .

[0071] Step S04: The mixed heat controller controls the waste heat regulating valve V1 and the cold air regulating valve V2 according to the main steam pressure PT02, the main steam flow FT01, the kiln head temperature TT01, and the furnace temperature TT02.

[0072] The specific steps of the step S04 are as follows:

[0073] (1) The mixed heat controller controls the opening of the waste heat regulating valve V1 according to the increase / decrease value of the waste heat regulating valve calculated by the waste heat boiler main controller, the OUT ΔV1 (k) value of the waste heat regulating valve calculated by the waste heat optimization controller, and the maximum increase step SPEED1 of the OUT ΔV1 (k) value of the waste heat regulating valve calculated by the furnace temperature observer.

[0074] OUT V1 (k) = OUT V1 (k-1) + Δu M + OUT ΔV1 (k) (Formula 5)

[0075] In the formula, OUT V1 represents the OUT value of the waste heat regulating valve in each cycle, Δu M is the output value calculated in step S01, OUT ΔV1 is the output value calculated in step S02, the maximum value is SPEED1, k represents the current cycle, and k-1 represents the previous cycle.

[0076] (2) The cold air valve V2 uses single loop PID control furnace temperature TT02, kiln head temperature TT01 as feed forward, when TT01 changes, timely adjust the cold air valve V2 and waste heat regulating valve V1, for timely overcome the influence of heat source disturbance on the waste heat boiler.

[0077] The method uses the waste heat boiler main controller to control the drum pressure or the main steam pressure, stabilizes the production process, uses the waste heat optimization controller to continuously maximize the waste heat regulating valve opening degree according to the residual amount of the waste heat regulating valve and the cold air regulating valve, uses the furnace temperature observer to control the waste heat regulating valve lifting speed, and finally uses the mixed heat controller to perform final output control on the waste heat regulating valve and the cold air regulating valve. Through the method, the waste heat utilization amount of the waste heat boiler can be improved, more recovered heat can be obtained under the premise of stable production process, and economic benefits can be improved.

[0078] Embodiment 1

[0079] In the waste heat boiler production process, the drum pressure and the main steam pressure are important process variables, and the variable directly affects the waste heat demand of the waste heat boiler. Therefore, the application provides a waste heat boiler waste heat utilization amount control method, which can stabilize production and effectively improve the waste heat recovery amount of the waste heat boiler, and further improves the economic benefits of the waste heat boiler. Under the premise of ensuring the stability of the drum pressure and the main steam pressure, the waste heat recovery amount of the waste heat boiler is improved, the waste heat boiler is controlled, greater economic benefits are obtained, and the waste heat utilization amount of the waste heat boiler is improved.

[0080] Step S01: The waste heat boiler main controller selects the drum pressure PT01 or the main steam pressure PT02 as a controlled variable, selects the waste heat regulating valve V1 as a control variable, sets the upper and lower limits of the controlled variable, the upper and lower limits of the control variable, and the upper and lower limits of the control variable increment, and calculates the increase and decrease values of the waste heat regulating valve by using model predictive control.

[0081] The following historical data are obtained from the DCS system.

[0082] Waste heat regulating valve V1 and drum pressure PT01 related data:

[0083] V1＝[28,28,28,28,28,28,28,28,28,28,28,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,28,28,28,28,28,28,28,28,28…………],

[0084] T2＝[1.0657,1.0696,1.0674,1.0528,1.0602,1.0533,1.0569,1.0652,1.0598,1.0691,1.0561,1.0669,1.0559,1.0724,1.0539,1.0680,1.0667,1.0585,1.0551,1.0715,1.0635,1.0549,1.0689,1.0585,1.0584,1.0648,1.0624,1.0700,1.0712,1.0702,1.0639,1.0612,1.0723,1.0651,1.0581,1.0586,1.0557,1.0673,1.0724,1.0654,1.0580,1.0734,1.0601,1.0578,1.0699,1.0655,1.0618,1.0731,1.0596,1.0721,1.0691,1.0642,1.0711,1.0720,1.0611,1.0614,1.0564,1.0725,1.0618,1.0585,1.0669,1.0734,1.0745,1.0594,1.0573,1.0734,1.0651,1.0712,1.0687,1.0550,1.0722,1.0687,1.0667,1.0711,1.0638,1.0626,1.0707,1.0646,1.0752,1.0671,1.0696,1.0708,1.0739,1.0752,1.0728,1.0616,1.0745,1.0747,1.0619,1.0708,1.0729,1.0627,1.0699,1.0719,1.0837,1.0685,1.0686,1.0755,1.0851,1.0847,1.0684,1.0842,1.0734,1.0844,1.0870,1.0823,1.0710,1.0866,1.0791,1.0725,1.0800,1.0890,1.0903,1.0856,1.0716,1.0765,1.0800,1.0766,1.0800,1.0767,1.0927,1.0771,1.0856,1.0831,1.0919,1.0793,1.0924,1.0909,1.0894,1.0931,1.0942,1.0841,1.0927,1.0822,1.0813,1.0823,1.0912,1.0845,1.0847,1.0820,1.0977,1.0951,1.0865,1.0834,1.0907,1.1001,1.0842,1.0838,1.0998,1.0853,1.0956,1.0963,1.0899,1.0952,1.0889,1.0879,1.0981,1.0999,1.1014,1.1037,1.0985,1.0924,1.1022,1.1020,1.1037,1.0941,1.0949,1.1043,1.0917,1.1003,1.1077,1.0947,1.0999,1.1005,1.0968,1.0920,1.0942,1.1112,1.0998,1.1127,1.1056,1.1021,1.0960,1.1052,1.1098,1.1043,1.1142,1.1081,1.0975,1.1061,1.1047,1.1096,1.1014,1.0997,1.1021,1.1084,1.1041,1.1020,1.1159,1.1114,1.1144,1.1145,1.1083,1.1182,1.1207,1.1154,1.1145,1.1174,1.1022,1.1181,1.1181,1.1161,1.1146,1.1161,1.1135,1.1083,1.1184,1.1110,1.1222,1.1103,1.1067,1.1111,1.1083,1.1109,1.1125,1.1205,1.1139,1.1255,1.1102,1.1093,1.1278,1.1211,1.1199,1.1137,1.1168,1.1182,1.1206,1.1182,1.1256,1.1146,1.1188,1.1138,1.1209,1.1175,1.1196,1.1280,1.1134,1.1282,1.1286,1.1197,1.1198,1.1238,1.1306,1.1240,1.1320,1.1267,1.1205,1.1163,1.1249,1.1197,1.1219,1.1329,1.1365,1.1335,1.1367,1.1212,1.1206,1.1330,1.1377,1.1377,1.1326,1.1251,1.1371,1.1202,1.1275,1.1405,1.1287,1.1253,1.1350,1.1328,1.1257,1.1282,1.1358,1.1337,1.1401,1.1235,1.1294,1.1436,1.1253,1.1342,1.1367,1.1410,1.1341,1.1429,1.1329,1.1366,1.1394,1.1392,1.1312,1.1321,1.1274,1.1439,1.1342,1.1360,1.1376,1.1323,1.1411,1.1375,1.1394,1.1298,1.1431,1.1427,1.1407,1.1372,1.1358,1.1314,1.1387,1.1402,1.1503,1.1479,1.1344,1.1490,1.1355,1.1435,1.1453,1.1335,1.1503,1.1485,1.1462,1.1429,1.1475,1.1473,1.1536,1.1516,1.1507,1.1367,1.1475,1.1411,1.1389,1.1536,1.1543,1.1454,1.1499,1.1466,1.1467,1.1491,1.1487,1.1570,1.1579,1.1497,1.1559,1.1430,1.1404,1.1469,1.1512,1.1402,1.1502,1.1586,1.1591,1.1551,1.1503,1.1585,1.1493,1.1607,1.1432,1.1593,1.1530,1.1464,1.1486,1.1493,1.1550,1.1466,1.1529,1.1612,1.1506,1.1572,1.1577,1.1567,1.1570,1.1502,1.1497,1.1634,1.1472,1.1498,1.1646,1.1650,1.1636,1.1604,1.1608,1.1608,1.1552,1.1559,1.1591,1.1608,1.1675,1.1550,1.1548,1.1656,1.1610,1.1651,1.1498,1.1626,1.1694,1.1575,1.1536,1.1629,1.1546,1.1680,1.1588,1.1643,1.1661,1.1617,1.1598,1.1593,1.1543,1.1657,1.1662,1.1531,1.1576,1.1725,1.1692,1.1601,1.1554,1.1635,1.1735,1.1607,1.1650,1.1565,1.1.1704, 1.1582, 1.1689, 1.1645, 1.1638, 1.1600, 1.1724, 1.1563, 1.1668, 1.1655, 1.1665, 1.1703, 1.1736, 1.1582, 1.1709, 1.1622, 1.1689, 1.1758, 1.1730, 1.1760, 1.1760, 1.1763, 1.1635, 1.1671, 1.1761, 1.1794, 1.1719, 1.1777, 1.1761, 1.1785, 1.1663, 1.1624, 1.1738, 1.1804, 1.1652, 1.1629, 1.1669, 1.1715, 1.1763, 1.1623, 1.1662, 1.1777, 1.1818, 1.1785, 1.1766, 1.1742, 1.1765, 1.1741, 1.1739, 1.1675, 1.1690, 1.1642, 1.1785, 1.1685, 1.1777, 1.1808, 1.1833, 1.1764, 1.1811, 1.1852, 1.1736, 1.1810, 1.1789, 1.1717, 1.1750, 1.1845, 1.1744, 1.1865, 1.1699, 1.1717, 1.1748, 1.1730, 1.1827, 1.1746, 1.1783, 1.1714, 1.1827, 1.1690, 1.1753, 1.1738, 1.1754, 1.1847, 1.1744, 1.1753, 1.1871, 1.1772, 1.1752, 1.1735, 1.1781, 1.1760, 1.1707………].

[0085] The mathematical model between the waste heat regulating valve and the drum pressure is obtained by using the "ARX" model identification method: y(t) - 0.1991*y(t-1) - 0.2671*y(t-2) - 0.2657*y(t-3) - 9.2639*y(t-4) = 0.0009281*u(t) + 0.0007*u(t-1) - 0.0002288*u(t-2) + 0.0006186*u(t-3)

[0086] -0.0009281*u(t-1) + 0.0007*u(t-2) - 0.0002288*u(t-3) + 0.0006186*u(t-4)

[0087] After a step response is applied to the model, the dynamic matrix is obtained:

[0088] A＝[0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.001055,0.001116,0.001177,0.001237,0.001297,0.001358,0.001418,0.001478,0.001538,0.001598,0.001657,0.001717,0.001776,0.001836,0.001895,0.001955,0.002014,0.002073,0.002132,0.002191,0.002249,0.002308,0.002367,0.002425,0.002484,0.002542,0.002600,0.002658,0.002716,0.002774,0.002832,0.002890,0.002947,0.003005,0.003062,0.003120,0.003177,0.003234,0.003291,0.003348,0.003405,0.003462,0.003519,0.003575,0.003632,0.003688,0.003745,0.003801,0.003857,0.003913,0.003969,0.004025,0.004081,0.004137,0.004192,0.004248,0.004303,0.004359,0.004414,0.004469,0.004524,0.004579,0.004634,0.004689,0.004744,0.004798,0.004853,0.004907,0.004962,0.005016,0.005070,0.005124,0.005178,0.005232,0.005286,0.005340,0.005394,0.005447,0.005501,0.005554,0.005608,0.005661,0.005714,0.005767,0.005820,0.005873,0.005926,0.005979,0.006031,0.006084,0.006136,0.006189,0.006241,0.006293,0.006345,0.006397,0.006449,0.006501,0.006553,0.006605,0.006656,0.006708,0.006759,0.006811,0.006862,0.006913,0.006964,0.007015,0.007066,0.007117,0.007168,0.007219,0.007269,0.007320,0.007371,0.007421,0.007471,0.007521,0.007572,0.007622,0.007672,0.007722,0.007771,0.007821,0.007871,0.007920,0.007970,0.008019,0.008069,0.008118,0.008167,0.008216,0.008265,0.008314,0.008363,0.008412,0.008461,0.008509,0.008558,0.008606,0.008655,0.008703,0.008751,0.008799,0.008847,0.008895,0.008943,0.008991,0.009039,0.009087,0.009134,0.009182,0.009229,0.009277,0.009324,0.009371,0.009418,0.009466,0.009513,0.009559,0.009606,0.009653,0.009700,0.009746,0.009793,0.009839,0.009886,0.009932,0.009978,0.010025,0.010071,0.010117,0.010163,0.010209,0.010254,0.010300,0.010346,0.010391,0.010437,0.010482,0.010528,0.010573,0.010618,0.010663,0.010708,0.010753,0.010798,0.010843,0.010888,0.010933,0.010977,0.011022,0.011066,0.011111,0.011155,0.011199,0.011243,0.011288,0.011332,0.011376,0.011420,0.011463,0.011507,0.011551,0.011594,0.011638,0.011682,0.011725,0.011768,0.011812,0.011855,0.011898,0.011941,0.011984,0.012027,0.012070,0.012113,0.012155,0.012198,0.012241,0.012283,0.012325,0.012368,0.012410,0.012452,0.012495,0.012537,0.012579,0.012621,0.012663,0.012704,0.012746,0.012788,0.012829,0.012871,0.012913,0.012954,0.012995,0.013037,0.013078,0.013119,0.013160,0.013201,0.013242,0.013283,0.013324,0.013365,0.013405,0.013446,0.013486,0.013527,0.013567,0.013608,0.013648,0.013688,0.013728,0.013769,0.013809,0.013849,0.013888,0.013928,0.013968,0.014008,0.014047,0.014087,0.014127,0.014166,0.014205,0.014245,0.014284,0.014323,0.014362,0.014401,0.014440,0.014479,0.014518,0.014557,0.014596,0.014635,0.014673,0.014712,0.014750,0.014789,0.014827,0.014865,0.014904,0.014942,0.014980,0.015018,0.015056,0.015094,0.015132,0.015170,0.015208,0.015245,0.015283,0.015321,0.015358,0.015396,0.015433,0.015470,0.015508,0.015545,0.015582,0.015619,0.015656,0.015693,0.015730,0.015767,0.015804,0.015840,0.015877,0.015914,0.015950,0.015987,0.016023,0.016060,0.016096,0.016132,0.016168,0.016205,0.016241,0.016277,0.016313,0.016349,0.016385,0.016420,0.016456,0.016492,0.016527,0.016563,0.016598,0.016634,0.016669,0.016705,0.016740,0.016775,0.016810,0.016846,0.016881,0.016916,0.016951,0.016985,0.017020,0.017055,0.017090,0.017124,0.017159,0.017194,0.017228,0.017262,0.017297,0.017331,0.017365,0.017400,0.017434,0.017468,0.017502,0.017536,0.017570,0.017604,0.017638,0.017671,0.017705,0.017739,0.017772,0.017806,0.017839,0.017873,0.017906,0.017940,0.017973,0.018006,0.018039,0.018073,0.018106,0.018139,0.018172,0.018204,0.018237,0.018270,0.018303,0.018336,0.018368,0.018401,0.018433,0.018466,0.018498,0.018531,0.018563,0.018595,0.018628,0.018660,0.018692,0.018724,0.018756,0.018788,0.018820,0.018852,0.018883,0.018915,0.018947,0.018979,0.019010,0.019042,0.019073,0.019105,0.019136,0.019167,0.019199,0.019230,0.019261,0.019292,0.019323,0.019354, 0.019385, 0.019416, 0.019447, 0.019478, 0.019509, 0.019540, 0.019570, 0.019601, 0.019632, 0.019662, 0.019693, 0.019723, 0.019754, 0.019784, 0.019814, 0.019844, 0.019875, 0.019905, 0.019935, 0.019965, 0.019995, 0.020025, 0.020055, 0.020085, 0.020115, 0.020144, 0.020174, 0.020204, 0.020233, 0.020263, 0.020292, 0.020322, 0.020351, 0.020381, 0.020410, 0.020439, 0.020469, 0.020498, 0.020527, 0.020556, 0.020585, 0.020614, 0.020643, 0.020672, 0.020701, 0.020730, 0.020758, 0.020787, 0.020816, 0.020844, 0.020873, 0.020902, 0.020930, 0.020959, 0.020987, 0.021015, 0.021044, 0.021072, 0.021100, 0.021128, 0.021156, 0.021184, 0.021212, 0.021240, 0.021268, 0.021296, 0.021324, 0.021352, 0.021380, 0.021407, 0.021435, 0.021463, 0.021490, 0.021518, 0.021545, 0.021573…………].

[0089] At the same time, the other parameters of the waste heat boiler main controller are as follows: the lower limit u min of the waste heat regulating valve control is 20, the upper limit u max of the waste heat regulating valve control is 40, the lower limit Δu min of the waste heat regulating valve control increment is -0.1, the upper limit Δu max of the waste heat regulating valve control increment is 0.1, the lower limit y min of the controlled steam drum pressure is 0.95 MPa, the upper limit y max of the controlled steam drum pressure is 1.2 MPa, the current value y of the steam drum pressure is 1.11 MPa, and the default coefficients of Q and M are 1.

[0090] The dynamic matrix A, the lower limit u min, control variable upper limit u max , control variable lower limit y min , control variable upper limit y max , control variable increment lower limit Δu min , control variable increment upper limit Δu max Substitute "Formula 1", using quadratic programming to calculate Δu M , when the current measured value of the drum pressure PT01 is within the control upper and lower limits Δu M = 0.

[0091] Step S02: The waste heat optimization controller determines the amount of waste heat remaining according to the current opening of the waste heat boiler furnace inlet waste heat regulating valve V1 and the current opening of the waste heat boiler furnace inlet cold air regulating valve V2, and when the drum pressure PT01 and the main steam pressure PT02 are within the control upper and lower limits, the waste heat utilization rate is continuously increased by maximizing the opening of the waste heat regulating valve V1.

[0092] It is known that the current opening of the waste heat regulating valve V1 is 23 (the valve is fully open at 100), the cold air regulating valve opening is 56 (the valve is fully open at 100), the drum pressure PT01 measured value is 1.11 MPa, the drum pressure PT01 control upper limit value is PT01 ENGH = 1.2 MPa, and the main steam flow FT01 measured value is 8.9 t / h, and the main steam flow FT01 target value is 11 t / h.

[0093] Since the waste heat regulating valve V1 is not fully open, the cold air regulating valve opening is less than the control upper limit value, the drum pressure value is less than the control upper limit value, and the main steam flow is not at the preset target value, there is an amount of waste heat remaining.

[0094] Set the time constant T to 600 s, the waste heat optimization controller calculation period is 30 minutes, and the output is calculated according to "Formula 2" and "Formula 3":

[0095] IN set = 5 * (PT01 ENGH - PT01.PV) = 5 * (1.2 - 1.11) = 0.45

[0096]

[0097] OUT ΔV1 can be calculated:

[0098] [0.0007, 0.0015, 0.0022, 0.0030, 0.0037, 0.0045, 0.0052, 0.0060……]

[0099] Step S03: The furnace temperature observer controls the output increment value OUT of the waste heat regulating valve according to whether the furnace temperature TT02 is within the operating rangeΔV1 The maximum increase step SPEED1 of (k).

[0100] Given the upper limit TT02 of the constraint of the current furnace temperature TT02 ENGH = 420 °C, the measured value TT02.PV = 415 °C, then TT02 ENGH The absolute value of the difference from TT02.PV is ΔE TT02 = 5 °C, set SPEED 1max = 0.5, calculate OUT according to "Formula 4" ΔV1 The maximum increase step of (k):

[0101] SPEED1 = min(ΔE TT02 / TT02 ENGH , SPEED 1max ) = min(5 / 420, 0.5) = 0.0119

[0102] Step S04: The mixed heat controller controls the waste heat regulating valve V1 and the cold air regulating valve V2 simultaneously based on the main steam pressure PT02, the main steam flow FT01, the kiln head temperature TT01, and the furnace temperature TT02.

[0103] (1) The mixed heat controller controls the opening of the waste heat regulating valve V1 according to the waste heat increase value calculated by the waste heat boiler main controller, the waste heat increase value calculated by the waste heat optimization controller, and the waste heat increase and decrease rate calculated by the furnace temperature observer.

[0104] The output of the mixed heat controller is:

[0105] Calculation in the first control cycle

[0106] Given that the current opening of the waste heat regulating valve V1 is 32, the drum pressure PT01 = 1.11 MPa is within the controlled upper and lower limits, and the calculated value of the waste heat boiler main controller in step S01 is Δu M [[ID=四十]]= 0, the calculated value of the waste heat optimization controller in step S02 is OUT ΔV1 (k) = 0.0007, from step S03, it can be seen that 0.0007 < SPEED1, then OUT ΔV1 (k) = 0.0007, from "Formula 5", it can be obtained that: OUT V1 (k) = OUT V1 (k - 1) + Δu M + OUT ΔV1 (k) = 32 + 0 + 0.0007 = 32.0007

[0107] Calculation in the second control cycle

[0108] The current waste heat regulating valve V1 opening degree is known as 32.0007, the drum pressure PT01 = 1.11 MPa is within the controlled upper and lower limits, the step S01 waste heat boiler main controller calculated value is Δu M = 0, the step S02 waste heat optimization controller calculated value is OUT ΔV1 (k) = 0.0015, and 0.0015 < SPEED1, so OUT ΔV1 (k) = 0.0015, and according to "Formula 5", OUT V1 (k) = OUT V1 (k-1) + Δu M + OUT ΔV1 (k) = 32.0007 + 0 + 0.0015 = 32.0022

[0109] The third control cycle is calculated

[0110] The current waste heat regulating valve V1 opening degree is known as 32.0022, the drum pressure PT01 = 1.11 MPa is within the controlled upper and lower limits, the step S01 waste heat boiler main controller calculated value is Δu M = 0, the step S02 waste heat optimization controller calculated value is OUT ΔV1 (k) = 0.0022, and 0.0022 < SPEED1, so OUT ΔV1 (k) = 0.0022, and according to "Formula 5", OUT V1 (k) = OUT V1 (k-1) + Δu M + OUT ΔV1 (k) = 32.0022 + 0 + 0.0022 = 32.0044

[0111] …

[0112] (2) The cold air valve V2 adopts single loop PID control furnace temperature TT02. The kiln head temperature TT01 is used as a feedforward, when TT01 changes, the cold air valve V2 and the waste heat regulating valve V1 are adjusted in time, so as to overcome the influence of heat source disturbance on the waste heat boiler in time.

[0113] As can be seen from the above embodiment, when the drum pressure PT01 is greater than the controlled lower limit and less than the controlled upper limit, Δu M = 0, if the waste heat optimization controller is not set, the waste heat regulating valve V1 remains unchanged, and if the waste heat optimization controller is set, the waste heat regulating valve V1 opening degree can be gradually increased according to the method of step S02, the waste heat recovery amount of the waste heat boiler is increased, and the economic benefit of the waste heat boiler is increased.

[0114] Although the embodiments of the present application have been shown and described above, it is to be understood that the above-described embodiments are merely exemplary, and are not to be construed as limiting the present application, and that modifications, substitutions, replacements and variations of the above-described embodiments can be made by those skilled in the art within the scope of the present application.

Claims

1. A control method for increasing the amount of waste heat utilization of a waste heat boiler, characterized by, The method comprises the following steps: Step S01: The waste heat boiler main controller selects the drum pressure PT01 or the main steam pressure PT02 as the controlled variable, and the waste heat regulating valve V1 as the control variable, sets the upper and lower limits of the controlled variable, the upper and lower limits of the control variable and the upper and lower limits of the control variable increment, and calculates the increment or decrement of the waste heat regulating valve V1 by using the model predictive control algorithm; Step S02: The waste heat optimization controller judges the waste heat surplus according to the current opening degree of the waste heat regulating valve V1 at the waste heat boiler furnace inlet and the current opening degree of the cold air regulating valve V2 at the waste heat boiler furnace inlet, and continuously increases the waste heat utilization rate by maximizing the opening degree of the waste heat regulating valve V1 when the drum pressure PT01 and the main steam pressure PT02 are within the controlled upper and lower limits; Step S03: The hearth temperature observer controls the waste heat adjusting valve to output an incremental value OUT per cycle according to whether the hearth temperature TT02 is within the operating range ΔV1 (k) the maximum incremental step SPEED1 Step S04: The mixed heat controller controls the waste heat regulating valve V1 and the cold air regulating valve V2 according to the main steam pressure PT02, the main steam flow FT01, the kiln head temperature TT01 and the furnace temperature TT02.

2. The control method of claim 1, wherein The step S01 calculates the increase / decrease value of the waste heat regulating valve V1 using a model predictive control algorithm M The control algorithm is as follows: where J represents an objective function, w is a set value vector, is a predicted value, Q is an error weight coefficient matrix, and u M is a control input, Δu M is a control input increment, R is a control weight coefficient matrix, is a predicted initial value, A is a dynamic matrix, and y min and y max represent lower and upper limits of a controlled variable, u min and u max represent lower and upper limits of a control variable, Δu min and Δu max represent lower and upper limits of a control variable increment.

3. The control method of claim 1, wherein The method for judging the waste heat surplus in the step S02 is as follows: (1) The waste heat regulating valve V1 is not fully opened; (2) The opening degree of the cold air regulating valve V2 is less than the control upper limit value; (3) The drum pressure PT01 value is less than the controlled upper limit value; (4) The main steam flow FT01 does not reach the preset target value; When the above conditions are met, the waste heat optimization controller outputs every 30 minutes according to the following algorithm: IN set = 5 * (PT01 ENGH - PT01.PV) (Equation 2) wherein IN set represents the exhaust heat control valve increment target value, PT01.PV represents the drum pressure measurement value, PT01 ENGH represents the drum pressure controlled upper limit value, OUT ΔV1 represents the exhaust heat control valve output increment value per cycle, T represents the time constant, k represents the current cycle, and k-1 represents the previous cycle.

4. The control method of claim 1, wherein The specific method of the step S03 is as follows: According to the constraint upper limit TT02 of the furnace temperature TT02 ENGH The absolute value of the difference between the measured value TT02.PV and the setpoint value TT02.SP is ΔE TT02 OUT is calculated using the following formula ΔV1 (k) maximum increase step SPEED1 = min(ΔE TT02 / TT02 ENGH ,SPEED 1max ) (Equation 4) wherein SPEED1 represents the OUT ΔV1 (k) the maximum value of the output of each step; SPEED 1max is a predetermined value, and the maximum value of SPEED1 is SPEED 1max .

5. The control method of claim 1, wherein the control method is characterized by: The specific steps of the step S04 are as follows: (1) The mixed heat controller controls the opening of the waste heat regulating valve V1 according to the increase / decrease value of the waste heat regulating valve calculated by the main controller of the waste heat boiler, the output increment value OUT of the waste heat regulating valve calculated by the waste heat optimization controller, the maximum increase step SPEED1 of (k) and the furnace temperature observer ΔV1 (k) The output increment value OUT of the waste heat regulating valve calculated by the furnace temperature observer ΔV1 (k) The maximum increase step SPEED1 of (k) controls the opening of the waste heat regulating valve V1; OUT V1 (k) = OUT V1 (k - 1) + Au M + OUT ΔV1 (k) (Equation 5) where OUT V1 represents the output value of V1 per cycle, Δu M is the output value calculated in step S01, OUT ΔV1 is the output value calculated in step S02, the maximum value is SPEED1, and k represents the current cycle and k-1 represents the previous cycle (2) The cold air valve V2 adopts single-loop PID control of the furnace temperature TT02, and the kiln head temperature TT01 is used as feedforward, so that when TT01 changes, the cold air valve V2 and the waste heat regulating valve V1 can be adjusted in time to overcome the influence of heat source disturbance on the waste heat boiler.

Images