Analysis of the quick corrosion of blast furnaces’gas pipes after the installation of dry-type de-dusting equipment and discussion about measures

Compared with the traditional wet-type de-dusting technology ,the dry-type de-dusting technology is considered to be environmentally friendly and energy-saving. However, the pipes carrying the de-dusted blast fiLrnace gas （BFG） tends to be corrosive more quickly and seriously. In order to investigate the reasons for the quick corrosion, the gas pipes and auxiliary bellows installed in Baosteel＇ s newly built BFG dry-type de-dusting system are studied. The corrosive properties of the condensed water, such as the pH value, are measured and analyzed. Meanwhile, various factors that may influence the corrosion rate of the pipes are studied by experiment. On the basis of the investigation and research, the causes of corrosion and leakage on the pipes are discovered. It is the process of dry de-dusting that is responsible ,to a large extent, for the quick corrosion of the pipes. The equipment of spray tower is introduced and its effects are then discussed. This tower is designed to eliminate most of chloridion and neutralized the acid by spraying the alkaline water to the dedusted gas flow. The practical operation shows that the tower helps to lessen the corrosiveness of the dry de-dusted gas effectively. The last part of this study analyzes the possible impacts of the dry-type de-dusting process of the newly built blast furnace （BF） on the main BFG piping which has been in the state of being corroded for years by estimating its potential corrosion rate, and some suggestions on maintenance are given as well.

Application of a finite element method to stress distribution in buried patch repaired polyethylene gas pipes

Advantages of polyethylene pipes over traditional steel or metal pipes have increased industry interest in the use of polyethylene(PE)pipelines for underground applications and especially in gas distribution networks.In this study,finite element analysis is used to calculate the stress distribution in a patch repaired defective gas pipe under internal pressure.The pipe is assumed to be buried at a depth of 125 cm.The material is assumed to be medium density PE80B,where the patch material was selected from high density polyethylene(HDPE).During the loading process,the seasonal pipe temperature changes,surcharge loads,soil column weight,and soil-pipe interaction were included in the analysis.Four types of patch arrangements were selected to repair the damaged pipe.The shape of the defect hole was deemed as circular or elliptic.With respect to elliptic defects,various minor to major diameter ratios,a/b,were selected to simulate a circular to a crack shaped defect.Based on the results,the semi-circular and saddle fusion patches decrease the peak von Mises stress in the pipe by almost the same amount.However,the minimum peak von Mises stress in the patch corresponds to the saddle fusion repair arrangement.Based on the results,with respect to a saddle fusion repair,when the shape of the defect approaches a crack,the peak von Mises stress in the pipe almost doubles and exceeds the pipe allowable stress for a working life of 50 years.With respect to higher values of a/b,the stress level in the patch repaired pipe is significantly below its limiting value for the same life expectancy.

Propagation of sound in pipes with gas flow of high temperature

In this paper, propagation of sound in pipes under the influence of a gas flow of high temperature is investigated . The analysis in the paper is based on the fundamental equations of fluid mechanics . Approximate formulas of the variation of parameters, such as the static tempera -ture, the local velocity of sound , the flow speed and the Mach number, with distance are obtained . The four parameters transmision matix which determines the acoustical character of the pipe is derived and discussed . The acoustical character of a pulsating gas heater is investigated experimentally and theoretically . The theoretical values of the resonant frequencies of the device are in good agreement with the experimental results.

Application of the finite element method for evaluating the stress distribution in buried damaged polyethylene gas pipes

During the loading process,buried gas pipes can experience severe stresses due to soil-structure interaction,the presence of traffic load,the soil’s column weight,daily and/or seasonal temperature changes and uniform internal pressure.In this research,the finite element method is employed to evaluate the behavior of buried Medium Density Polyethylene(MDPE)pipes which have been subjected to damage at the pipe crown.The modeled pipe damage ranges from a very small circular hole to a large circular hole and elliptic holes with various minor to major diameter ratios,a/b,to simulate circular to crack-shaped defects.The computer simulation and stress analyses were performed using the ANSYS software finite element package.The stress distribution around the defect was determined under the aforementioned mechanical and thermal loading conditions.Then,the maximum values of Von Mises stresses in the damaged buried PE pipes,which were evaluated by finite element solution,were compared with their corresponding reduced strength for safe operation with a life expectancy of fifty years.Based on the results,the maximum Von Mises stress values in the defective buried polyethylene gas pipeline are significantly above the pipe strength limit at 35℃.The previously mentioned stress values increase with the following factors:temperature increase,increase in circular hole diameter and decrease in elliptic hole diameter ratio(a/b).The maximum stress in the damaged PE pipe is due to the simultaneous loading effects of soil column weight,internal pressure,vehicle wheel load and pipe temperature increase.Additionally,the novel finite element models and stress plots for the buried damaged pipe and the pipe material allowable strength will be used to investigate the correct repair method for the damaged gas pipeline and to choose the best patch arrangement which will assure a safe repair.