Research On Heat Transfer And Structural Characteristics Of Non-stick Coating Heat Exchanger For Coke Oven Bridge Tube

The recovery of sensible heat from raw coke oven gas is currently a major problem in the coking industry.At present,the raw gas sensible heat recovery technology is mainly concentrated in the riser,and the riser waste heat recovery technology only recovers the sensible heat of the raw gas above 500℃;at the same time,the raw gas after cooling has a large amount of tar at the riser outlet and the bridge pipe entrance Precipitation,causing pipeline blockage,affecting production.This paper proposes a new type of bridge tube heat exchanger,and by coating nano-coating to solve the problem of bridge tube raw gas sticking and clogging and waste heat recovery.In this paper,a combination of numerical simulation and experimental research is used to study the heat transfer characteristics of the nano non-stick coating bridge tube heat exchanger during a coking cycle and the temperature change law of the inner wall surface,and analyze its comprehensive performance.The main work content is as follows :1.Design and build a simulated coke oven raw gas waste heat recovery system experimental platform,adopt a similar structure,make a bridge tube heat exchange device model,and conduct gas-water heat transfer experiments to obtain heat transfer at 400℃,500℃,and 600℃ The coefficient varies with water flow and air flow,providing experimental data verification for subsequent numerical simulation work.A numerical model of the riser pipe and bridge pipe of the coke oven was established,and the accuracy of the model was verified by the experimental results and field surveys.Numerical simulation adopts turbulence model,radiation model,energy equation,discrete equivalence model,and selects SIMPLEC algorithm.The average temperature of the raw coke oven gas at the outlet of the riser pipe(inlet of the bridge pipe)in the five time periods(1h,4h,7h,14 h,17h)in a coking cycle is obtained,which are 612.84℃ and 626.70℃ respectively.645.11°C,678.56°C,480.44°C.2.Three different structures(outer straight fin type,spiral coil type,and embedded spiral fin type)bridge tube heat transfer device are studied.The numerical simulation results show that:(1)With the progress of the coking process,the average temperature of the heat exchanger wall shows a gradual rise,rising to the highest at14 h,and dropping to the lowest at the end of coking;(2)The temperature fluctuation range of the inner wall surface of the three kinds of bridge tube heat exchange devices are 137℃～317℃,133.6℃～297℃,122.12℃～247.32℃,and the best working temperature of the nano non-stick coating combined with raw gas is 120 ℃～300℃,the maximum difference of the wall temperature of the three types of heat exchangers is 100.23℃,94.32℃,87.13℃.The coating application conditions of the embedded spiral fin-tube heat exchanger are the best;(3)The comprehensive heat exchange performance of the heat exchange device gradually decreases with the progress of the coking time.The order of the comprehensive heat exchange performance is the built-in spiral fin structure,the spiral coil type,and the outer straight fin type;For the spiral fin of the helical fin sleeve,when the number of spiral fin turns is 5,the comprehensive heat transfer performance is the best.