Establishing Of Dynamic Measurement Method Of Fouling Thermal Resistance And Synthesis And Application Of Scale Inhibitor Based On PESA

Boilers,as a sealed device for exporting heat energy to the outside world,play a vital role in industrial production,such as power generation,heating and steam supply,and in the lives of residents.However,in order to prevent serious accidents caused by corrosion,the boiler operating environment is required to maintain a pH above 10,which makes boilers,especially hot water boilers(feed and replenishment water control is poor)during operation is prone to scale problems,the formation of a layer of scale on the heat transfer surface will greatly increase energy consumption and seriously reduce the efficiency of the boiler.Therefore,it is important to evaluate the degree of boiler scaling and develop excellent boiler scale inhibitors to save water,save energy,protect the environment and ensure the efficient and stable operation of industrial equipment.At present,the evaluation methods of boiler scale mainly include scale weight method and scale layer thickness measurement method,both of which can only be evaluated after the boiler is shut down,so it is not possible to realize the real-time evaluation of boiler scale level.In order to solve this problem,this paper refers to the method of fouling thermal resistance of heat transfer equipment of industrial circulating cooling water system and establishes a method to evaluate the degree of boiler fouling in real time by measuring the fouling thermal resistance at the heat transfer interface.A simple boiler simulated heat transfer device is designed,a heat transfer model is established and the deposition of fouling during heat transfer is measured by fouling thermal resistance method under different water quality.The results show that:the fouling thermal resistance of the heater heat transfer surface increases with the heating time,and finally reaches the deposition-desorption equilibrium,and the calculated fouling thermal resistance is 7.24×10-3 m2·K/W.After that,the fouling thermal resistance is in the reciprocal cycle of rising and falling,not in a large increase.However,according to the boiler standard requirements,when the thermal resistance of the dirt exceeds 8.4×10-4 m2·K/W,then the boiler scale is serious,has reached the cleaning requirements.It can thus be seen that the simulator simulates the boiler fouling process well and that the fouling thermal resistance method is suitable for the evaluation of boiler fouling.To verify the application of the fouling thermal resistance method in a real boiler system,this paper monitors the fouling behavior of a small electric heating boiler by measuring the change in wall temperature of the heating tube.The change in thermal resistance of the fouling with increasing and decreasing temperature is plotted to evaluate the change in thermal resistance of the fouling under different experimental conditions(pH,hardness).it's show that the fitted curve can characterize the change of fouling deposition with heating time and is consistent with the monitoring results of the simulated device,which promotes boiler scaling when the water pH is maintained at about 10.The thermal resistance method has the advantages of non-invasive,simple operation and real-time measurement compared to the traditional boiler scale measurement method.In order to solve the problem of boiler scaling caused by boiler feed water pH>10,it is necessary to add scale inhibitors,the use of chelating,dispersion of scale inhibitors to retard the formation of scale layer deposition.Polyepoxysuccinic acid(PESA)and its derivatives have received extensive attention in boiler scale inhibition due to their non-toxic,non-hazardous,environmentally friendly,degradable and excellent scale inhibition properties in boilers.In this paper,PESA was modified with L-cystine to synthesize a new type of polyepoxysuccinic acid derivative(L-Cystine-PESA).The molecular s of the new derivative was charactered,and the scale inhibition,dispersion degradation properties were investigated.The results show that the calci carbonate scale resistance can reach 96.85%and calcium phosphate scale resistance is 86.67%at the dosage of 12mg/L,both are improved compared w the commercial grade PESA;and the dispersion of iron oxide performance is improved by nearly 20%compared with PESA.A terpolymeric scale inhibitor(LC-T-PESA)was synthesized by introducing L-cysteine and taurine into the molecular chain of polyepoxysuccinic acid.The scale inhibiting performance was best when the PESA:LC:T mass ratio was 8:1:1.At a dosage of 10 mg/L,the calcium carbonate scale resistance can be 96.98%.The synthetic L-Cystine-PESA and LC-T-PESA were subjected to fouling thermal resistance experiments by fouling thermal resistance method using a simulation device,and the fouling resistance was 58.30%and 68.75%at 10 mg/L,respectively.The measured scale inhibition rate is about 30%lower than that measured by the calcium carbonate deposition method.This is because the experimental time of the scale thermal resistance method is longer and the concentration of scale-forming ions in the experimental system continues to increase with time.The results show that the scale thermal resistance method can be used to evaluate the scale performance of boiler scale inhibitors,and the experimental process and device design are more in line with the boiler's scaling behavior than the traditional calcium carbonate deposition method,which is theoretically more reference value for the performance evaluation of scale inhibitors in boilers.