CN-116793527-B - Method for determining SNCR optimal temperature window position of biomass vibrating grate boiler

CN116793527BCN 116793527 BCN116793527 BCN 116793527BCN-116793527-B

Abstract

The invention discloses a method for determining an SNCR optimal temperature window position of a biomass vibration grate boiler. The method at least comprises the following steps of collecting the smoke temperature dynamic data of preset different height positions in the furnace, collecting the smoke temperature dynamic data of different positions of preset horizontal sections in the furnace, and judging the dynamic positions of the temperature windows of the full load and the full hearth through established smoke temperature dynamic characteristic parameters. According to the invention, by establishing the SNCR temperature window smoke temperature dynamic characteristic parameters, the smoke temperatures at different positions of the full hearth under full load are continuously monitored and dynamically analyzed, and the dynamic position of the SNCR temperature window is determined.

Inventors

XIA WENJING
HE CHANGZHENG
JIANG WENHAO

Assignees

中冶华天工程技术有限公司
南京博沃科技发展有限公司
中冶华天南京工程技术有限公司

Dates

Publication Date: 20260505
Application Date: 20230526

Claims (2)

1. The method for determining the SNCR optimal temperature window position of the biomass vibrating grate boiler is characterized by comprising the following steps of: the method comprises the steps of dynamically monitoring the smoke temperature of a full hearth under typical load, and continuously collecting the smoke temperature dynamic data of different height positions in the furnace; The method comprises the steps of continuously collecting dynamic smoke temperature data of different positions of horizontal sections at each height position in a furnace through dynamic monitoring of the smoke temperature of the whole section under typical load; Judging the dynamic position of a full-load and full-hearth temperature window through the established smoke temperature dynamic characteristic parameters; The smoke temperature dynamic characteristic parameters comprise a temperature window relative smoke temperature L and a temperature window smoke temperature coincidence degree O t , wherein the calculation formula and the judgment conditions are as follows: L= (t a -T l ）/（T h -T l ) ×100 units:% T a is the average value of smoke temperature of a horizontal section continuously monitored at a certain height position of the boiler, and is C; T l is the lower limit of the SNCR temperature window, and 850 ℃ is taken; t h is the upper limit of the SNCR temperature window, and is 1100 ℃; When t a <T l , L is less than 0%, the average value of the smoke temperature is lower than the lower limit of the temperature window and is not in the temperature window; When t a >T h , L is more than 100%, the average value of the smoke temperature is higher than the upper limit of the temperature window and is not in the temperature window; When T l <t a < T h is set, L is between 0% and 100%, the smoke temperature average value is within the temperature window, and the boiler position is considered as the actual optional position of the SNCR temperature window; O t = n t /NX 100 in% When the initial value of T l < t i <T h ,n t = n t + 1,n t is 0; t i is the smoke temperature of the ith horizontal section monitored at equal time intervals continuously at a certain height position of the boiler during the test, wherein the smoke temperature is equal to or less than C, and N is 0<i; N is the total number of points of the smoke temperature data monitored at a certain position of the boiler continuously and at equal time intervals during the test period; n t is the number of points of the continuous equal-time interval monitoring smoke temperature data in the SNCR temperature window; When O t > 80%, the boiler position is considered as the actual optional position of the SNCR temperature window; The smoke temperature dynamic characteristic parameters also comprise a super Wen Rongyu theta, a calculation formula and a judging condition: θ=t am -t a , units °c T am is a smoke Wen Chaowen alarm value, T am =T hh -δ a /2, and the unit is DEG C; T hh is the over-temperature limit value of the denitration reaction, and is T hh =T h +50; when θ >0 ℃, the boiler position is considered as the actual selectable position of the SNCR temperature window.
2. The method for determining the SNCR optimal temperature window position of the biomass vibration grate boiler according to claim 1, wherein the smoke temperature dynamic characteristic parameter further comprises a calculation formula of a mean value delta a of the maximum smoke temperature deviation of the section, wherein the calculation formula is as follows: Delta a = average ( δ 1 , δ 2 , δ 3 , δ 4 , δ i ..the above-mentioned group), units: degree C Δi is the maximum smoke temperature deviation of the horizontal section of the ith time point monitored at a certain height position at continuous equal time intervals, and the number of the section arrangement measurement points is not less than 4 points.

Description

Method for determining SNCR optimal temperature window position of biomass vibrating grate boiler Technical field: the invention relates to a method for determining a dynamic position of an SNCR temperature window of a biomass boiler. The background technology is as follows: Biomass energy is the energy that a living organism converts solar energy obtained into chemical energy through photosynthesis and stores in a biomass, and is derived from photosynthesis of plants, carbon dioxide generated by combustion thereof is substantially equal to carbon dioxide absorbed, thus realizing zero emission of carbon. Biomass boilers take biomass energy as fuel, wherein the biomass direct-fired power generation technology adopting the vibrating grate high-temperature high-pressure boiler is a mature advanced technology practiced in foreign countries for many years, and is listed as a global popularization project by united nations. The vibrating grate is a grate which periodically adds fuel and discharges ash slag in a vibrating mode, is quite suitable for burning biomass fuel, and also presents periodic fluctuation in combustion in the furnace, NOX generation and flue gas temperature due to the vibration of the grate. SNCR denitration technology is the first choice of biomass boiler control NOX emission. The technology is that under the action of no catalyst, a reducing agent (10% -40% urea solution or 10% -25% ammonia water) is sprayed into a furnace through an atomization spraying system, and nitrogen oxides in smoke are reduced into harmless nitrogen and water. This technique can reduce ammonia leakage and escape under suitable temperature conditions to ensure ideal denitration efficiency, and a suitable temperature interval for SNCR denitration reaction is referred to as a "temperature window". When the reaction temperature is lower than the lower limit of the temperature window, the reaction time is longer than the residence time of the flue gas in the furnace, the denitration reaction rate is reduced, the denitration efficiency is linearly reduced, the denitration reaction rate is increased along with the increase of the reaction temperature, the denitration efficiency is linearly increased, but when the temperature is increased to the high temperature, NH 3 is oxidized into NOx, and the denitration efficiency is linearly reduced, as shown in figure 1. Since the advent of SNCR denitration technology, many researchers have studied the reaction mechanism, experimental characteristics, influence factors, and the like in detail at home and abroad. It is widely considered that main factors influencing SNCR denitration effect include reaction temperature, reaction time, ammonia nitrogen molar ratio, reducing agent injection position and the like. According to different operation conditions of the reducing agent and the SNCR, the optimal temperature window of the SNCR denitration reaction usually occurs between 850 and 1100 ℃, and if the temperature is too high or too low, the utilization rate of the reducing agent and the denitration efficiency are reduced. In practical engineering application, the temperature of the hearth can be changed along with the change of various factors such as boiler load, fuel source, heat exchange efficiency of the furnace and a heating surface, and the like, so that the position of an optimal temperature window for denitration reaction can be moved along with the change, and the injection position of the reducing agent is fixed, so that the denitration efficiency kept higher for a long time has certain difficulty [6]. For vibrating grate boilers, the above problems are compounded by periodic vibration of the grate, as the smoke temperature and NOX generation in the boiler also exhibit periodic fluctuations in the order of minutes, and the position of the optimum temperature window for the denitration reaction is dynamically changed. In addition, the mixing uniformity of the existing reducing agent and the flue gas is poor, so that the denitration efficiency of the furnace is obviously affected, and the national flue gas emission index can be up to standard only by simply improving the ammonia nitrogen molar ratio (increasing the consumption of the reducing agent). At present, a biomass vibrating grate boiler according to the requirements of an ultralow emission standard generally has a series of problems of high urea consumption, obvious exhaust ammonia escape, ammonium bisulfate sedimentation, rising of boiler smoke resistance, limitation of boiler load and the like. Therefore, aiming at the SNCR denitration system widely applied to the biomass vibration grate boiler, the injection position of the reducing agent is overlapped with the position of the optimal temperature window to the greatest extent, the injection position is ensured to meet the requirement of uniform mixing of the reducing agent and the flue gas as far as possible, a test method of the dynamic position of the optimal temp