The calculation formula and checking conditions of the axial membrane stress σ_c in the shell side cylinder of fixed tubesheet heat exchangers are given in our country's standards GB/T 151 and JB 4732 for tube sheet calculation. The absolute value of the stress is checked according to allowable stress of the material without distinguishing whether it is tensile stress or compressive stress. Although the components of resultant force and moment V_s and M_s at the end of the shell connected with the tubesheet are obtained by solving the equations of deformation compatibility in JB 4732, the local bending stress at the end of the shell is not required to be further calculated. Aiming at the simplification of shell axial stress checking conditions in our national standards, this paper verifies the feasibility and rationality ofthe simplification through engineering examples and finite element analysis.

As the national demand for chemical materials continues to increase, the storage capacity of conventional spherical tanks can no longer meet the production turnaround needs of the device. The steel cryogenic full-containment tank has become the preferred way for chemical plants to store olefins owing to its advantages of small footprint, large storage capacity, safety and efficiency, short construction cycle and low cost.Its installation process has a significant impact on the overall construction schedule, safety and quality control management of the storage tanks.Taking the 100,000 m³ steel cryogenic full-capacity tank as an example, this paper mainly introduces the construction process of installation in regular order for the wall plate of cryogenic tanks with three-layer tank wall. It specifically describes the installation and construction technology of the outer tank wall plate, the intermediate tank wall plate and the inner tank wall plate of the trimetallic wall cryogenic storage tank. This technology can provide reference for the installation of similar storage tanks.

As an important storage facility for liquefied natural gas, large LNG storage tank has the characteristics of complex structure, special materials, high quality requirements and great difficulty in construction and so forth. In recent years, with the continuous progress of LNG storage tank design and construction technology, China began to build large LNG low-temperature storage tanks of 270,000 cubic meters. This paper highlighted the assembly and construction method of the steel vault of large LNG storage tanksof 270,000 cubic meters, and it expounded from the aspects of vault partition mode, preparation of construction measures for prefabrication and installation, temporary storage mold and hoisting of vault sheet in the tanks. In addition, it also introduced the calculation of construction stability for the prefabrication of vault sheet, temporary storage, and tank hoisting after increasing the size of the tank steel vaults in the hope of providing reference for the assembly of similar tank steel vaults.

This paper established a mathematical model for calculating the heat transfer in spherical tanks. Taking C₂ (ethylene and ethane) spherical tanks as the research object, it analyzed the heat transfer characteristics of the front and back surfaces of the spherical tanks in different seasons and at different times within one year, and proposed the design suggestions for heat insulation of spherical tanks at different construction sites. Meanwhile, the paper obtained the cold loss of ethylene and ethane in semi-refrigerated storage with different thicknesses of insulation and made energy saving suggestions accordingly.The research results are of certain guidance for cold insulation design of C₂ spherical tanks in practical projects.

In order to analyze the influence of different combinations of liningcross sections and anchors on the temperature distribution of the outer casting of the cracking furnace, this paper combined the structural characteristics of fire brick lining and established respectively the calculation models for hot-faced bricks, hot-faced and back-layered bricks, composite bricks, bricks with tie-back, bricks with tie-back and support plate. The finite element method is applied to analyze the heat transfer process of the models and the results are compared with the standard calculation results. Based on the temperature distribution of the outer casting of the furnace in the calculation results, the deviation of the calculation results between different models is summarized and the influence range of partial hot spot is analyzed. Meanwhile, suggestions for the lining heat transfer calculation during engineering are provided.

The tubular heater in the refinery unit provides heat to the process flow. The main combustion control objectives of heater include maintaining the process medium temperature at the heater outlet, ensuring no risk of combustible material accumulation in the heater and achieving safe operation and high energy efficiency. In many oversea projects, the combustion design of heaters with operation mode of balance draft and force draft adopts "fuel-air ratio control"scheme. Upon an increasing variation of heat demand, air flow increases before fuel does. On the other hand, upon a reduction of heat demand, fuel gas flow decreases before air does. This is to ensure excess air during the combustion change process in the heater and avoid insufficient oxygen supply and incomplete combustion, and reduce the safety risk due to combustible material accumulation.Compared with conventional combustion control design, the fired heaters with "fuel-air ratio control" have smaller excess air coefficient and less flue gas emissions; the thermal efficiency as well as safety have been improved;and the operating cost has been reduced. Under the goal of carbon neutrality, the "fuel-air ratio control" scheme for heaters is a feasible solution to improve fuel efficiency and reduce CO₂ emissions.

Low temperature heating furnaces with furnace chamber temperature lower than 700 ℃ in refining and chemical enterprises have problems of incomplete combustion and high content of CO and O₂ in flue gas after low nitrogen combustion transformation. To solve the above problems, low CO and low nitrogen combustion technology was developed. This technology adopts the method of fuel staging combustion and primary fuel pre-mixed combustion which can improve the intensity and temperature of the central flame, making the flame combustion more complete and stable. While reducing NO_x emissions, it can effectively reduce the CO and O₂ content in the exhaust gas, and improve the thermal efficiency and safety of the heating furnace. Taking a reforming cylinder furnace and jet fuel hydrogenation furnace of a Sinopec branch as an example, this paper presents the revamp of the heater burner using this technology. After the revamp, the heating furnace flame burning was quite stable; the CO content in the exhaust flue gas decreased from 168.2 mg/m3 and 1 308.8 mg/m3 to 24.7 mg/m³ and 6.3 mg/m³ respectively; the O₂ content in the exhaust flue gas decreased from 4.2% and 5.6% to 3.7% and 3.0% respectively. Meanwhile, the NO_x emission was far below the national emission standard. This has ensured the safe, eco-friendly and efficient operation of the heating furnace.

Corrosion of Hastelloy C-276 tube bundle of the first preheater for tail gas catalytic combustion in a petrochemical PTA plant occurred in the range of 100 to 300 mm at the tube bundle inlet after 13 years of operation. And the same corrosion phenomenon occurred again after only three and a half months of operation after replacing the tube bundle of the heat exchanger of the same material. Aiming at the above problems, the behavior of high corrosion rate of C-276 tube bundles at inlet end was studied by comparing such factors as operation time, operating conditions and changes in medium composition combining with the analysis of corrosion morphology of heat exchanger tubes, energy spectrum analysis of corrosion products and the results of velocity boundary layer analysis in the flow inlet area of heat exchanger tubes, the corrosion mechanism was determined and it was concluded that the increase of water content in the tail gas was the key factor to corrosion failure. Meanwhile, the corresponding protection suggestions were proposed according to the analysis results.

Leakage on the welded joint of tube to tubesheet occurs due to cracking in high pressure tube bundle with plug header of carbon steel air-cooled heat exchanger in wet H₂S service in refinery. Aiming at such problem, this paper carried out research and analysis in terms of material selection, tube joint hardness, welding process, post-welding heat treatment and so forth by combining the structural characteristics of the tubes and tube boxes of plug-channel air cooler. The analysis concluded that the hardness of the welded joint exceeding the standard was the main cause of cracking.In view of the above reasons, the paper proposed more practical and reliable recommended requirement to prevent wet H₂S stress corrosion cracking on the welded joint of tube to tube and the recommended requirement was implemented in enterprises. This has achieved good results.

Stress corrosion cracking (SCC) of austenitic stainless steel is a kind of corrosion failure frequently occurring during shutdown and maintenance of refining and chemical units. In recent years, with the continuous material upgrading of refining and chemical units, austenitic stainless steel is increasingly applied and the failure cases of stress corrosion cracking of austenitic stainless steel are more and more common. This paper summarized and analyzed the occurrence conditions, corrosion characteristics, development process and influencing factors of stress corrosion cracking of polysulphuric acid. It discussed the feasible protective measures against stress corrosion cracking of polysulphuric acid in refining and chemical units. The paper also analyzed and expounded several problems related to stress corrosion cracking of polysulphuric acid.

This paper presents the theoretical basis and structural characteristics of the type selection in designing oil slurry pump for catalytic cracking unit of a refining enterprise, as well as its operation after being put into use. In view of the large deviation of the operating conditions of the oil slurry pump from the design parameters, the pump was modified for localization, and the design parameters were further optimized. After the transformation, the pump has achieved good effects in energy saving and long-cycle operation. The above optimization and improvement measures are of certain significance for the type selection in designing oil slurry pumps.

Combining with the catalytic cracking unit in flue gas environmentat 700 ℃, this paper analyzed the high-temperature creep properties and high-temperature precipitation phase effects of AISI 300 series heat-resistant stainless steel. It investigated the feasibility of applying AISI 347 material. On this basis, the paper studied through testing the mechanical properties and metallurgical structure changes of AISI 347 pipeline including base metal and weld zone after different heat-preservation time at 700 ℃. The test results show that the plasticity and impact toughness of the 347 base material are better than that of the weld zone at high temperature; there are σ-phase and carbide precipitates in the base material and weld zone under long-term heating at 700 ℃ which mainly concentrate on the grain boundaries. With the increase of heating time, the material strength gradually increases, plasticity and toughness decrease, but the trend of deterioration of material properties is relatively flat. The above study indicates that AISI 347 stainless steel is the ideal material for catalytic cracking unit in flue gas environment at 700 ℃.

Compared with the US, Europe and Japan, the construction of LNG terminal in China started late, and our own technology and domestic equipment have not yet experienced the long-term operation test, which brings certain uncertainties to the long-term stable operation of the devices. Starting from the introduction of the technology development and the design scheme of the main equipment of LNG terminal in China, this paper introduces the technology characteristic and the localization process including the discharge arm, compressor, cryogenic pump, gasifier and cryogenic valves. Then it compares the actual operation of the domestic and imported equipment and concluded that most of the main parameter index of domestic equipment have reached the standards of imported products of the same type. The comparison study results indicate that the introduction, development, trial, promotion and improvement of technical research path can continue to improve the reliability and stability of domestic equipment. Such equipment has had strong quality competitiveness with the capability to ensure the long-term stable operation of the device.