Optimization method for steam extraction pressure under adjustable steam supply mode of medium-low pressure communicating pipe
阅读说明：本技术 一种中低压连通管可调供汽方式下抽汽压力的寻优方法 (Optimization method for steam extraction pressure under adjustable steam supply mode of medium-low pressure communicating pipe ) 是由 马汀山 石慧 吕凯 居文平 王妍 许朋江 薛朝囡 邓佳 张建元 于 2021-06-29 设计创作，主要内容包括：本发明公开了一种中低压连通管可调供汽方式下抽汽压力的寻优方法,本发明充分考虑制造厂对中排压力在纯凝线以下的安全裕,设定其实际运行裕度,将原本供热工况下中排压力设定为纯凝线运行,调整为在纯凝线和纯凝线以下实际运行裕度之间运行,中排压力从原来的“线”延伸至“面”,大大增加了其运行可操作性和可控性。按照本发明优化后,中排压力值多在纯凝线以下,在一定程度上提升了中压缸效率,且供热蝶阀憋压程度下降,其开度较优化前增大,节流损失下降,机组能耗指标下降,进一步提高了运行经济性。(The invention discloses an optimization method for steam extraction pressure under an adjustable steam supply mode of a medium-low pressure communicating pipe, which fully considers the safety margin of the medium-pressure discharge pressure below a straight line in a manufacturing plant, sets the actual operation margin, sets the medium-pressure discharge pressure under the original heat supply working condition as the straight line operation, adjusts the medium-pressure discharge 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 medium-pressure discharge pressure. After the optimization according to the invention, the middle exhaust pressure value is mostly below the straight line, the efficiency of the middle pressure cylinder is improved to a certain extent, the pressure holding degree of the heat supply butterfly 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.)
1. A method for optimizing the extraction pressure of a medium-low pressure communicating pipe in an adjustable steam supply mode is characterized by comprising the following steps:
s1, determining the safe operation margin of the pressure discharge in the unit below the straight line according to the factory check standard;
s2, determining the lower limit of safe operation pressure of the unit when the unit is at the middle exhaust pressure according to the safe operation margin;
s3, determining the actual operation margin of the unit under the medium discharge pressure by combining the actual operation condition;
s4, determining the actual operation pressure lower limit of the unit when the unit is at the middle exhaust pressure according to the actual operation margin;
and S5, determining the relation between the reheat steam flow and the medium exhaust 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 optimization method for the extraction pressure in the medium-low pressure communicating pipe in the adjustable steam supply mode according to claim 1, wherein in S2, the lower limit of the safe operation pressure of the medium discharge pressure is as follows:
Pzp＝a×Qrs+b-ΔP
wherein Q isrsFor the re-steam flow, Δ P is the safe operating margin for the intermediate discharge pressure below the straight line, and a and b are coefficients.
3. The method for optimizing the extraction pressure in the medium-low pressure communicating pipe adjustable steam supply mode according to claim 1, wherein in S3, the actual operation margin of the unit at the medium discharge pressure is (0.7-0.9) delta P, and delta P is the safe operation margin of the medium discharge pressure below the straight line.
4. The optimization method for the extraction pressure in the medium-low pressure communicating pipe in the adjustable steam supply mode according to claim 1, wherein in S4, the lower limit of the actual operation pressure of the unit in the medium-discharge pressure is as follows:
Pzp＝a×Qrs+b-(0.7-0.9)ΔP
wherein Q isrsFor reheat steam flow, Δ P is the safe operating margin for mid-discharge pressure below the straight line, and a and b are coefficients.
5. The method for optimizing the extraction pressure of a medium-low pressure communicating pipe in an adjustable steam supply mode according to claim 1, wherein the medium discharge pressure PzpThe determination method of (2) is as follows:
when P is presentzp＞PgqAt medium discharge pressure a × Qrs+b-(0.7-0.9)ΔP≤Pzp＜a×Qrs+b；
When P is presentzp≤PgqAt intermediate discharge pressure Pzp＝Pgq。
6. The method for optimizing the extraction pressure in the medium-low pressure communicating pipe adjustable steam supply mode according to claim 1, wherein the medium-low pressure communicating pipe is used for optimizing the extraction pressure in the industrial steam supply mode with different reheat steam flow rates QrsLower, PzpWhen > PgqAt intermediate discharge pressure PzpIs taken to be between a × Qrs+ b- (0.7-0.9) Δ P and a × QrsAny value between + b; when P is presentzp≤PgqAt intermediate discharge pressure PzpGet Pgq。
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 steam extraction pressure in a medium-low pressure communicating pipe 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 medium-discharge adjustable industrial steam supply mode based on medium-low pressure communicating pipe heat supply butterfly valve parameter adjustment is to select a proper position on the medium-low pressure communicating pipe to punch and extract steam, and a safety valve, a check valve, a quick-closing regulating valve, an electric stop valve and the like are sequentially additionally arranged on a 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 the steam turbine, the strength of the last stage of blades of the intermediate pressure cylinder, the intermediate exhaust temperature, the strength of the valve rod of the heat supply butterfly valve, the execution force of the servomotor and the like.
After the straight condensing unit is reformed by middle-exhaust adjustable steam extraction based on the parameter adjustment of a middle-low pressure communicating pipe heat supply butterfly valve, the middle-exhaust steam extraction pressure can change along with the change of the steam extraction amount, and the larger the steam extraction amount is, the lower the middle-exhaust steam extraction pressure is, so that the enthalpy drop of the middle-pressure last stages of moving and stationary blades is increased. If the steam extraction amount is too large, the strength of the through-flow part of the intermediate pressure cylinder is increased, and the safety is affected. Therefore, under the steam extraction working condition, the linear relation between the reheat steam flow and the middle 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 medium-pressure blade are in the design range. The pure linear one-to-one correspondence mode of the medium discharge pressure along with the reheat steam flow is difficult to accurately control under the double-variable constraint of frequent electric and thermal load change. In addition, the intermediate discharge pressure is determined by the linear relation of the reheat steam flow rate and the intermediate discharge pressure under the original pure condensing working condition, the safety margin that the intermediate discharge pressure can be properly adjusted in a manufacturing plant 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 the medium-pressure exhaust pressure cannot be accurately controlled according to the pure condensation working condition under the existing adjustable industrial steam supply mode of a medium-low pressure communicating pipe, and the safety margin that the medium-pressure exhaust pressure can be adjusted down in a manufacturing plant is ignored, so that the medium-pressure exhaust pressure is higher during the actual industrial steam supply, the steam supply throttling loss is larger, and the operation economy is poorer, and provides an optimization method for the steam extraction pressure under the adjustable steam supply mode of the medium-low pressure communicating pipe.
In order to achieve the above object, the present invention comprises the steps of:
s1, determining the safe operation margin of the pressure discharge in the unit below the straight line according to the factory check standard;
s2, determining the lower limit of safe operation pressure of the unit when the unit is at the middle exhaust pressure according to the safe operation margin;
s3, determining the actual operation margin of the unit under the medium discharge pressure by combining the actual operation condition;
s4, determining the actual operation pressure lower limit of the unit when the unit is at the middle exhaust pressure according to the actual operation margin;
and S5, determining the relation between the reheat steam flow and the medium exhaust 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 operation pressure of the medium discharge pressure is:
Pzp＝a×Qrs+b-ΔP
wherein Q isrsFor the re-steam flow, Δ P is the safe operating margin for the intermediate discharge pressure below the straight line, and a and b are coefficients.
In S3, the actual operation margin of the unit at the middle discharge pressure is (0.7-0.9) delta P, and the delta P is the safe operation margin of the middle discharge pressure below the pure condensation line.
In S4, the lower limit of the actual operating pressure of the unit at the medium discharge pressure is:
Pzp＝a×Qrs+b-(0.7-0.9)ΔP
wherein Q isrsFor reheat steam flow, Δ P is the safe operating margin for mid-discharge pressure below the straight line, and a and b are coefficients.
Middle exhaust pressure PzpThe determination method of (2) is as follows:
when P is presentzp＞PgqAt medium discharge pressure a × Qrs+b-(0.7-0.9)ΔP≤Pzp＜a×Qrs+b；
When P is presentzp≤PgqAt intermediate discharge pressure Pzp＝Pgq。
Under the condition of adjustable industrial steam supply mode of medium-low pressure communicating pipe, at different reheat steam flow rates QrsLower, PzpWhen > PgqAt intermediate discharge pressure PzpIs taken to be between a × Qrs+ b- (0.7-0.9) Δ P and a × QrsAny value between + b; when P is presentzp≤PgqAt intermediate discharge pressure PzpGet Pgq。
Compared with the prior art, the invention fully considers the safety margin of the center exhaust pressure below the straight line in the manufacturing plant, sets the actual operation margin, sets the middle exhaust pressure under the original heat supply working condition as the straight line operation, adjusts the middle 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 middle exhaust pressure. After the optimization according to the invention, the middle exhaust pressure value is mostly below the straight line, the efficiency of the middle pressure cylinder is improved to a certain extent, the pressure holding degree of the heat supply butterfly 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 pure condensed line of 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 pressure discharge in the unit below the straight line according to the factory check standard;
s2, determining the lower limit of safe operation pressure of the unit when the unit is at the middle exhaust pressure according to the safe operation margin; the lower limit of the safe operation pressure of the middle discharge pressure is as follows:
Pzp＝a×Qrs+b-ΔP
wherein Q isrsFor the re-steam flow, Δ P is the safe operating margin for the intermediate discharge pressure below the straight line, and a and b are coefficients.
S3, determining the actual operation margin of the unit under the medium discharge pressure by combining the actual operation condition; the actual operation margin of the unit at the middle discharge pressure is (0.7-0.9) delta P, and the delta P is the safe operation margin of the middle discharge pressure below a straight line.
S4, determining the actual operation pressure lower limit of the unit when the unit is at the middle exhaust pressure according to the actual operation margin; the lower limit of the actual operation pressure of the unit at the middle exhaust pressure is as follows:
Pzp＝a×Qrs+b-(0.7-0.9)ΔP
wherein Q isrsFor reheat steam flow, Δ P is the safe operating margin for mid-discharge pressure below the straight line, and a and b are coefficients.
And S5, determining the relation between the reheat steam flow and the medium exhaust 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.
Industrial steam supply pressure PgqUnder the condition of optimizing front heat supply, the middle exhaust pressure PzpThe determination method comprises the following steps:
when P is presentzp＞PgqAt intermediate discharge pressure Pzp＝a×Qrs+b；
When P is presentzp≤PgqAt intermediate discharge pressure Pzp＝Pgq。
Under the condition of optimized heat supply, the middle discharge pressure PzpThe determination method of (2) is as follows:
when P is presentzp＞PgqAt medium discharge pressure a × Qrs+b-(0.7-0.9)ΔP≤Pzp＜a×Qrs+b；
When P is presentzp≤PgqAt intermediate discharge pressure Pzp＝Pgq。
Under the condition of adjustable industrial steam supply mode of medium-low pressure communicating pipe, at different reheat steam flow rates QrsLower, PzpWhen > PgqAt intermediate discharge pressure PzpIs taken to be between a × Qrs+ b- (0.7-0.9) Δ P and a × QrsAny value between + b; when P is presentzp≤PgqAt intermediate discharge pressure PzpGet Pgq。
Example (b):
a steam turbine of a 330MW unit of a certain power plant is an N330-16.67/537/537 type, subcritical, single-shaft, two-cylinder, two-steam-exhaust, once-intermediate reheating and condensing steam turbine manufactured by Orient steam turbine Limited, and is required to bear the external steam supply parameters of 0.8MPa, 240 ℃ and 100t/h, and the steam extraction position is a medium-low pressure communicating pipe.
Under the pure condensing condition, the linear relation between the middle exhaust pressure and the reheat steam flow is as follows: pzp＝0.00099×Qrs+0.0187. Under the heating working condition, when the medium 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 7637.8 kJ/kWh. After adjustment according to the invention, the maximum medium discharge pressure can be adjusted as follows: pzp＝0.00099×QrsAnd (4) 0.061, the heat consumption rate of the heat supply under the THA working condition (calculated according to a benefit return method) is as low as 7597.9kJ/kWh, and the reduction is about 39.9 kJ/kWh. The energy-saving effect is obvious.
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