CN113469433A - Optimization method for extraction pressure in hot-recycling adjustable steam supply mode - Google Patents

Optimization method for extraction pressure in hot-recycling adjustable steam supply mode Download PDF

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CN113469433A
CN113469433A CN202110731471.XA CN202110731471A CN113469433A CN 113469433 A CN113469433 A CN 113469433A CN 202110731471 A CN202110731471 A CN 202110731471A CN 113469433 A CN113469433 A CN 113469433A
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pressure
straight line
margin
high discharge
high exhaust
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CN113469433B (en
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马汀山
石慧
吕凯
居文平
王妍
许朋江
薛朝囡
邓佳
张建元
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Xian Thermal Power Research Institute Co Ltd
Xian Xire Energy Saving Technology Co Ltd
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Xian Thermal Power Research Institute Co Ltd
Xian Xire Energy Saving Technology Co Ltd
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    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06Q—INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES; SYSTEMS OR METHODS SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES, NOT OTHERWISE PROVIDED FOR
    • G06Q10/00—Administration; Management
    • G06Q10/04—Forecasting or optimisation specially adapted for administrative or management purposes, e.g. linear programming or "cutting stock problem"
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F17/00—Digital computing or data processing equipment or methods, specially adapted for specific functions
    • G06F17/10—Complex mathematical operations
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06Q—INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES; SYSTEMS OR METHODS SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES, NOT OTHERWISE PROVIDED FOR
    • G06Q50/00—Systems or methods specially adapted for specific business sectors, e.g. utilities or tourism
    • G06Q50/06—Electricity, gas or water supply
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E20/00—Combustion technologies with mitigation potential
    • Y02E20/14—Combined heat and power generation [CHP]

Abstract

The invention discloses a method for optimizing steam extraction pressure in a heat-re-adjustable steam supply mode, which fully considers the safety margin of a manufacturing plant for high exhaust pressure below a straight line, sets the actual operation margin of the manufacturing plant, sets the high exhaust pressure under the original heat supply working condition as straight line operation, adjusts the high exhaust pressure to operate between the straight line and the actual operation margin below the straight line, and greatly increases the operation operability and controllability of the manufacturing plant. After the optimization according to the invention, the high discharge pressure value is mostly below the straight condensation line, the high pressure cylinder efficiency is improved to a certain extent, the pressure holding degree of the heat supply valve is reduced, the opening degree is increased compared with that before the optimization, the throttling loss is reduced, the energy consumption index of the unit is reduced, and the operation economy is further improved.

Description

Optimization method for extraction pressure in hot-recycling adjustable steam supply mode
Technical Field
The invention belongs to the field of cogeneration heat supply of coal-fired generator sets, and particularly relates to an optimization method for extraction pressure in a heat-adjustable steam supply mode.
Background
In order to meet the industrial steam supply requirements of wide load, large flow and stable parameters under the background of peak shaving of the current power grid, the coal-electricity unit mostly adopts an adjustable steam extraction transformation technology, namely, an adjusting valve is additionally arranged at a certain position of steam-water thermodynamic cycle, and when the heat supply steam extraction pressure is reduced due to the external supply of large-flow steam extraction or the reduction of the electric load, the opening degree of the adjusting valve is adjusted to ensure the wide and stable steam supply pressure and steam supply load. Typical steam supply modes include heat readjustable steam extraction based on intermediate connection door parameter adjustment and intermediate exhaust adjustable steam extraction based on intermediate and low pressure communicating pipe heat supply butterfly valve parameter adjustment.
The heat-adjustable industrial steam supply mode is characterized in that a proper position is selected on a pipeline from steam from a reheater to a middle adjusting valve for punching and steam extraction, and a safety valve, a check valve, a quick-closing regulating valve, an electric stop valve and the like are sequentially additionally arranged on the steam extraction pipeline so as to realize external heat supply and steam extraction. The method has a mature technology, but the operation range of the method needs to be comprehensively influenced by the factors such as the axial thrust balance of a steam turbine, the strength of the last stages of blades of a high-pressure cylinder, the high exhaust temperature, the strength of a middle linkage gate valve rod, the actuating force of a servomotor and the like.
After the straight condensing unit is modified by heat re-adjustable steam extraction based on intermediate connection door adjustment, the heat re-steam extraction pressure can change along with the change of the steam extraction amount, and the higher the steam extraction amount is, the lower the heat re-steam extraction pressure is, and the lower the corresponding high exhaust pressure is, so that the enthalpy drop of the last stages of high-pressure movable and stationary blades is increased. If the amount of extracted steam is too large, the strength of the flow-through portion of the high pressure cylinder is increased, which affects safety. Therefore, under the steam extraction working condition, the linear relation between the main steam flow and the high exhaust pressure under the original pure condensation working condition is recommended to be maintained, and the steam extraction pressure falls on the line so as to ensure that the front-back pressure difference, the axial thrust and the like of the high-pressure blade are in the design range. The high exhaust pressure is in a pure linear one-to-one correspondence mode along with the main steam flow, and is difficult to accurately control under the double-variable constraint of frequent electric and thermal load change. In addition, the high exhaust pressure is determined by the linear relation between the flow rate of the main steam and the high exhaust pressure under the original pure condensing working condition, the safety margin of a manufacturing plant for properly adjusting the high exhaust pressure is ignored, the safety is excessively pursued, and the feasibility of optimizing the economy is ignored.
Disclosure of Invention
The invention aims to solve the problems that high exhaust pressure cannot be accurately controlled according to a pure condensation working condition in the existing heat re-adjustable industrial steam supply mode, and safety margin of a manufacturing plant for adjusting the high exhaust pressure is neglected, so that the high exhaust pressure is higher during actual industrial steam supply, the steam supply throttling loss is larger, and the operation economy is poorer.
In order to achieve the above object, the present invention comprises the steps of:
s1, determining the safe operation margin of the unit with high exhaust pressure below a straight line according to the check standard of a manufacturer;
s2, determining the lower limit of safe operation pressure of the unit at high exhaust pressure according to the safe operation margin;
s3, determining the actual operation margin of the unit under high exhaust pressure by combining the actual operation condition;
s4, determining the actual operation pressure lower limit of the unit at high exhaust pressure according to the actual operation margin;
and S5, determining the relation between the main steam flow and the high discharge pressure of the unit according to the lower limit of the safe operation pressure and the lower limit of the actual operation pressure, and drawing a pure condensation line to finish optimization.
In S2, the lower limit of the safe operating pressure of the high discharge pressure is:
Pgp＝a×Qzs+b-ΔP
wherein Q iszsAs the main steam flow, Δ P is the safe operating margin with high discharge pressure below the straight line, and a and b are coefficients.
In S3, the actual operation margin of the unit under high discharge pressure is (0.7-0.9) delta P, and the delta P is the safe operation margin of the high discharge pressure below a pure condensation line.
In S4, the lower limit of the actual operating pressure of the unit at the high discharge pressure is:
Pgp＝a×Qzs+b-(0.7-0.9)ΔP
wherein Q iszsAs the main steam flow, Δ P is the safe operating margin with high discharge pressure below the straight line, and a and b are coefficients.
The high discharge pressure practical operating minimum is:
Pgp,min＝Pgq/(1-μ)
wherein, PgqThe pressure is industrial steam supply pressure, and mu is reheater pipeline pressure loss.
High discharge pressure PgpThe determination method of (2) is as follows:
when P is presentgp>PgqAt/(1-. mu.) the high discharge pressure a.times.Qzs+b-(0.7-0.9)ΔP≤Pgp<a×Qzs+b；
When P is presentgp≤PgqAt/(1-. mu.) the high discharge pressure Pgp＝Pgq/(1-μ)。
Under the heat-adjustable industrial steam supply mode, under different main steam flow QzsWhen P isgp>PgqAt/(1-. mu.) the high discharge pressure PgpPreferably between a × Qzs+ b- (0.7-0.9) Δ P and a × QzsAny value between + b, the high exhaust pressure value area is the shaded part in the figure; when P is presentgp≤PgqAt/(1-. mu.) the high discharge pressure PgpGet Pgq/(1-μ)。
Compared with the prior art, the invention fully considers the safety margin of a manufacturing plant for the high exhaust pressure below the straight line, sets the actual operation margin as that, sets the high exhaust pressure under the original heat supply working condition as that of the straight line, adjusts the high exhaust pressure to operate between the straight line and the actual operation margin below the straight line, and greatly increases the operation operability and controllability of the high exhaust pressure. After the optimization according to the invention, the high discharge pressure value is mostly below the straight condensation line, the high pressure cylinder efficiency is improved to a certain extent, the pressure holding degree of the heat supply valve is reduced, the opening degree is increased compared with that before the optimization, the throttling loss is reduced, the energy consumption index of the unit is reduced, and the operation economy is further improved.
Drawings
FIG. 1 is a schematic view of a pure condensation line according to the present invention.
Detailed Description
The invention is further described below with reference to the accompanying drawings.
Referring to fig. 1, the present invention comprises the steps of:
s1, determining the safe operation margin of the unit with high exhaust pressure below a straight line according to the check standard of a manufacturer;
s2, determining the lower limit of safe operation pressure of the unit at high exhaust pressure according to the safe operation margin; the lower limit of the safe operation pressure of the high discharge pressure is as follows:
Pgp＝a×Qzs+b-ΔP
wherein Q iszsAs the main steam flow, Δ P is the safe operating margin with high discharge pressure below the straight line, and a and b are coefficients.
S3, determining the actual operation margin of the unit under high exhaust pressure by combining the actual operation condition; the actual operation margin of the unit under the high discharge pressure is (0.7-0.9) delta P, and the delta P is the safe operation margin of the high discharge pressure below a straight line.
S4, determining the actual operation pressure lower limit of the unit at high exhaust pressure according to the actual operation margin; the lower limit of the actual operation pressure of the unit at the high exhaust pressure is as follows:
Pgp＝a×Qzs+b-(0.7-0.9)ΔP
wherein Q iszsThe main steam flow and the delta P are high discharge pressure in the straight condensing lineA and b are coefficients.
And S5, determining the relation between the main steam flow and the high discharge pressure of the unit according to the lower limit of the safe operation pressure and the lower limit of the actual operation pressure, and drawing a pure condensation line to finish optimization.
The high discharge pressure practical operating minimum is:
Pgp,min＝Pgq/(1-μ)
wherein, PgqThe pressure is industrial steam supply pressure, and mu is reheater pipeline pressure loss.
High exhaust pressure P under optimized front heating conditiongpThe determination method comprises the following steps:
when P is presentgp>PgqAt/(1-. mu.) the high discharge pressure Pgp＝a×Qzs+b；
When P is presentgq≤PgqAt/(1-. mu.) the high discharge pressure Pgq＝Pgq/(1-μ)。
High exhaust pressure P under optimized post-heat supply conditiongqThe determination method of (2) is as follows:
when P is presentgp>PgqAt/(1-. mu.) the high discharge pressure a.times.Qzs+b-(0.7-0.9)ΔP≤Pgp<a×Qzs+b；
When P is presentgp≤PgqAt/(1-. mu.) the high discharge pressure Pgp＝Pgq/(1-μ)。
Under the heat-adjustable industrial steam supply mode, under different main steam flow QzsWhen P isgp>PgqAt/(1-. mu.) the high discharge pressure PgpPreferably between a × Qzs+ b- (0.7-0.9) Δ P and a × QzsAny value between + b, the high exhaust pressure value area is the shaded part in the figure; when P is presentgp≤PgqAt/(1-. mu.) the high discharge pressure PgpGet Pgq/(1-μ)。
Example (b):
a1000 MW unit turbine of a certain power plant is an N1000-25/600/600 type, ultra-supercritical, single-shaft, four-cylinder, four-steam-exhaust, once-intermediate-reheating and condensing turbine manufactured by Orient steam turbine Limited, and is required to bear the external steam supply parameters of 3.1MPa, 310 ℃ and 220t/h, and the steam extraction position is a heat re-pipeline.
Under the pure condensing working condition, the linear relation between the high exhaust pressure and the main steam flow is as follows: pgp＝0.0014×Qzs+0.2717. Under the heating working condition, when the high discharge pressure is determined according to the mode, the heating heat consumption rate (calculated according to the benefit electricity return method) under the working condition of the THA of the computer unit is 7297.4 kJ/kWh. After adjustment according to the invention, the maximum high discharge pressure can be adjusted as follows: pgp＝0.0014×Qzs+0.1117, heat rate of heat supply (calculated by benefit return method) at THA was as low as 7274.6kJ/kWh, which was reduced by about 22.8 kJ/kWh. The energy-saving effect is obvious.

Claims (7)

1. An optimization method for extraction pressure in a hot re-adjustable steam supply mode is characterized by comprising the following steps:
s1, determining the safe operation margin of the unit with high exhaust pressure below a straight line according to the check standard of a manufacturer;
s2, determining the lower limit of safe operation pressure of the unit at high exhaust pressure according to the safe operation margin;
s3, determining the actual operation margin of the unit under high exhaust pressure by combining the actual operation condition;
s4, determining the actual operation pressure lower limit of the unit at high exhaust pressure according to the actual operation margin;
and S5, determining the relation between the main steam flow and the high discharge pressure of the unit according to the lower limit of the safe operation pressure and the lower limit of the actual operation pressure, and drawing a pure condensation line to finish optimization.
2. The method for optimizing extraction pressure in a hot re-adjustable steam supply mode according to claim 1, wherein in S2, the lower safe operating pressure limit of the high exhaust pressure is:
Pgp＝a×Qzs+b-ΔP
wherein Q iszsAs the main steam flow, Δ P is the safe operating margin with high discharge pressure below the straight line, and a and b are coefficients.
3. The method for optimizing extraction pressure in a hot re-adjustable steam supply mode according to claim 1, wherein in S3, the actual operation margin of the unit at the high discharge pressure is (0.7-0.9) Δ P, and Δ P is the safe operation margin of the high discharge pressure below the straight line.
4. The method for optimizing extraction pressure in a hot re-adjustable steam supply mode according to claim 1, wherein in S4, the lower limit of the actual operation pressure of the unit at the high exhaust pressure is:
Pgp＝a×Qzs+b-(0.7-0.9)ΔP
wherein Q iszsAs the main steam flow, Δ P is the safe operating margin with high discharge pressure below the straight line, and a and b are coefficients.
5. The method of claim 1, wherein the minimum actual operating value of the high exhaust pressure is:
Pgp，min＝Pgq/(1-μ)
wherein, PgqThe pressure is industrial steam supply pressure, and mu is reheater pipeline pressure loss.
6. The method of claim 1, wherein the high exhaust pressure P is selected from the group consisting ofgpThe determination method of (2) is as follows:
when P is presentgp＞PgqAt/(1-. mu.) the high discharge pressure a.times.Qzs+b-(0.7-0.9)ΔP≤Pgp＜a×Qzs+b；
When P is presentgp≤PgqAt/(1-. mu.) the high discharge pressure Pgp＝Pgq/(1-μ)。
7. The method of claim 1, wherein the steam extraction pressure is optimized at different main steam flow rates Q in the heat-recoverable industrial steam supply modezsWhen P isgp＞PgqAt/(1-. mu.) the high discharge pressure PgpGet between aQzs+ b- (0.7-0.9) Δ P and a × QzsAny value between + b; when P is presentgp≤PgqAt/(1-. mu.) the high discharge pressure PgpGet Pgq/(1-μ)。
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