大型高凝原油储罐的节能途径

随着我国的经济不断地发展,我国的石油储备战略规模也在逐步地扩展,为了扩大我国的石油战略储备,需要增加大型高凝原油储罐的数量。由于浮顶罐在储存石油的过程中会产生极大的热量,因此,原油会在浮顶罐的罐顶与内壁不断的凝结成为原油,凝结的原油严重影响原油储罐的使用,也造成了极大的原油损失。为了减少浮顶罐和蒸汽对原油的消耗,及时让原油降温,有效对其进行储蓄和输送,就需要计算出最佳的运送时间和储存温度。为了在加热油罐的时间中保证所需的温度和热量,就需要合理控制蒸汽和压力。针对如何对大型高凝原油储罐进行有效的节能提出了一些意见,根据一些计算,合理地对原油进行运送,达到节能的目的。     

双盘式浮顶储罐罐顶传热系数的计算分析

本文运用传热学基本原理,在归纳总结出双盘浮顶传热系数计算方法的基础上,结合现场数据,研究对比了单双盘浮顶传热系数范围和变化规律的不同,并分析了环境温度、风速和储罐容积对双盘浮顶罐罐顶传热系数的影响。     

基于红外测温的双盘式浮顶储油罐散热损失分布规律研究

采用红外热像仪、表面温度计等对双盘式浮顶储油罐的表面温度场进行测试。结果表明:罐顶表面温度呈轴对称分布,径向温度梯度远高于周向,且距离罐中心越远,表面温度越高。油蒸汽挥发导致浮顶和罐壁间的一二次密封处散热损失明显升高,使其成为罐顶表面温度最高的区域。浮舱隔板、桁架和椽子等结构形成了热桥,使局部位置的表面温度升高,增大了罐顶的散热损失。罐壁周向表面温度梯度低于轴向,并且受油温影响较大,在罐壁保温结构的结合部位、局部保温结构破损位置的表面温度较高,散热损失较大。基于表面温度法,结合环境温度和风速测试结果,采用强迫对流换热关联式计算得到储罐不同部位的散热损失。结果表明:对于双盘式浮顶储油罐,罐顶散热损失最大,约占储罐总散热损失的67%,罐壁散热损失约占25%,罐底散热损失约占8%。     

大型熔盐储罐罐顶非线性屈曲分析

本文利用ANSYS Workbench软件对某大型熔盐储罐罐顶网壳进行了非线性屈曲分析,并参考《空间网格结构技术规程》对其进行了刚度和稳定性的校核,为类似大型储罐罐顶稳定性设计提供一定参考。     

大港油田储罐保温现状及太空隔热涂料的应用

通过对液体隔热保温涂料的应用和分析,优选出了一种新型太空隔热保温涂料,并在储罐保温中推广应用。新型太空隔热涂料综合了涂料和保温材料的双重特性,具有传热系数低、反射率高、整体密封性好和防腐等特点,其在油田储罐保温中的应用,改变了传统的保温模式,避免了因保温材料吸水造成的保温效果下降和外壁腐蚀等问题,同时解决了浮顶罐罐顶不能保温的问题,为浮顶罐罐顶保温提供了一条有效的途径。     

固定顶储罐原油蒸发损耗的计算方法

为了保障油田安全生产运行,减少油品损失,对固定顶储油罐的蒸发损耗量进行计算具有重要意义.本文总结了固定顶储罐的大、小呼吸损耗及通风损耗的产生机理,以瓦廖夫斯基-契尔尼金公式为基础,给出了不同类型的蒸发损耗计算方法.对某油田原油处理站的三座储罐进行应用分析,计算结果与测试结果平均相对误差为16.62％.指出可通过溶解气量系数进行修正,以满足现场对原油蒸发损耗计算的要求,为油田企业掌握固定顶储罐蒸发损耗量提供技术支持.     

大型储罐用钢板SPV4902焊接裂纹的分析及处理

2005年9月，某石油储备基地300×10 4m2原油储罐建造工程开工，当地锅检所对全部储罐现场制造安装进行了监督检验。2006年5月，锅检所对施工单位已完成自检的T101、T103、T105、T106和T201等5台10×104 m3双盘浮顶储罐纵环焊缝进行第三方无损检测抽查时，     

内浮顶油罐浅析

内浮顶罐是近几年发展起来的，有一部分是新建的，有一部分是利用立式圆柱形拱顶油罐，在罐中加建内浮盘而改建的，内浮顶罐有钢板、铝板制成的，也有用玻璃纤维增强聚脂及环氧物、硬泡沫、塑料或各种复合材料建造的。浮顶结构有隔仓式、浮船式、浮盘式等多种。１内浮顶罐...     

浮顶油罐太阳能相变维温系统运行特性分析

为解决浮顶油罐维温加热能耗大、运行成本高问题,建立了浮顶油罐太阳能相变维温系统仿真模型。基于TRNSYS平台研究其运行特性,分析系统中相变储热箱蓄放热效率、原油静储热负荷以及原油供热量占比等指标,并与其他供热系统对比经济效益。结果表明：建立的浮顶油罐太阳能相变维温系统分析模型平均偏差为5.6%;4～12月份浮顶油罐太阳能相变维温系统满足原油静储需求;相比太阳能维温系统和锅炉系统,太阳能相变维温系统可节省年总投资费用6.9%和40%。     

炼油厂废气的排放与防治

炼油厂生产过程中会产生大量废气,如不加以治理,会给环境带来严重危害。以某石化企业为例,对炼油厂生产过程中产生的工艺废气、燃烧烟气等进行统计分析。炼油厂的废气来源通常包括有组织排放源、无组织排放源和火炬排放烟气等。为使废气污染物达标排放,治理措施主要有:燃料气脱硫、催化烟气旋风分离、重整装置再生尾气处理、硫磺回收装置、减少烃类排放、减少恶臭气体排放、锅炉废气治理设施等。其中,减少烃类排放主要包括原油及轻油采用浮顶罐储存、设置气柜回收燃料气、常减压装置"三顶"气回收、油气回收装置等;减少恶臭气体排放主要包括含硫污水密闭输送、储罐恶臭气体处理等。炼油厂除了对传统的SO_2、NO_x、烟尘等常规污染物排放源进行监测外,还要加强对非甲烷总烃、VOCs、TSP等排放源进行监测,并对特征污染物的无组织排放进行监控。     

Research on the variation law of heating temperature field and the effective energy utilization rate of a steam coil for the floating roof tank

ABSTRACT

As per the way of heat transfer and its main characteristics for oil tank, the theoretical model of steam coil heating in large oil storage tanks was established. The Visual Basic language was applied for calculating the temperature field of crude oil in the heating process by the trial method procedure, and the variation law of temperature field and the energy effective utilization rate of oil tank could be obtained. Results show that the temperature of crude oil and the energy effective utilization rate became higher with the increase of the ambient temperature, steam pressure, and the reduction of storage liquid level. The temperature of crude oil near the steam coil became higher with the increase of steam pressure. The oil temperature at the tank outlet presented periodic change, which was affected simultaneously by the steam pressure and the ambient temperature.     

Thermal analysis of solar thermal energy storage in a molten-salt thermocline

A comprehensive, two-temperature model is developed to investigate energy storage in a molten-salt thermocline. The commercially available molten salt HITEC is considered for illustration with quartzite rocks as the filler. Heat transfer between the molten salt and quartzite rock is represented by an interstitial heat transfer coefficient. Volume-averaged mass and momentum equations are employed, with the Brinkman-Forchheimer extension to the Darcy law used to model the porous-medium resistance. The governing equations are solved using a finite-volume approach. The model is first validated against experiments from the literature and then used to systematically study the discharge behavior of thermocline thermal storage system. Thermal characteristics including temperature profiles and discharge efficiency are explored. Guidelines are developed for designing solar thermocline systems. The discharge efficiency is found to be improved at small Reynolds numbers and larger tank heights. The filler particle size strongly influences the interstitial heat transfer rate, and thus the discharge efficiency.     

Role of heat pipes in improving the hydrogen charging rate in a metal hydride storage tank

Metal hydrides can store hydrogen at high volumetric efficiencies. As the process of charging hydrogen into a metal powder to form its hydride is exothermic, the heat released must be removed quickly to maintain a rapid charging rate. An effective heat removal method is to incorporate a heat exchanger such as a heat pipe within the metal hydride bed. In this paper, we describe a two-dimensional numerical study to predict the transient heat and mass transfer in a cylindrical metal hydride tank embedded with one or more heat pipes. Results from a parametric study of hydrogen storage efficiency are presented as a function of storage tank size, water jacket temperature and its convective heat transfer coefficient, and heat pipe radius and its convective heat transfer coefficient. The effect of enhancing the thermal conductivity of the metal hydride by adding aluminum foam is also investigated. The study reveals that the cooling water jacket temperature and the heat pipe's heat transfer coefficient are most influential in determining the heat removal rate. The addition of aluminum foam reduces the filling time as expected. For larger tanks, more than one heat pipe is necessary for rapid charging. It was found that using more heat pipes of smaller radii is better than using fewer heat pipes with larger radii. The optimal distribution of multiple heat pipes was also determined and it is shown that their relative position within the tank scales with the tank size.     

Experimental volumetric heat transfer characteristics between oil and glass pebbles in a small glass tube storage

A small glass tube containing oil and glass pebbles is constructed to evaluate rapidly the volumetric heat transfer characteristics during charging. An electrical hot-plate in thermal contact with a steel spiral coil is used to charge the oil/pebble-bed storage under different average charging flow rates. The heat transfer characteristics are presented in terms of the average temperature of the oil, the average temperature of the pebbles, the average charging power and the volumetric heat transfer coefficient. The results reveal that an increase in the average charging flow rate results in a linear increase in the volumetric heat transfer coefficient. An expression for the correlation between the superficial mass flow velocity, the average pebble diameter and the volumetric heat transfer coefficient is also formulated.     

Performance analysis of a direct-contact thermal energy storage-solidification

Performance of a direct-contact latent heat energy storage during discharging process has been investigated. The storage medium used is sodium thiosulphate pentahydrate of which the melting temperature is 48°C and the heat exchanging fluid is heat transfer oil. An empirical expression to evaluate the volumetric heat transfer coefficient has been carried out. A lumped analysis is also found to be quite suitable to analyze the temperature of the storage medium and its solid fraction including the temperature of the oil leaving the storage. The results agree well with those of the experiments.     

Experimental investigation on a combined sensible and latent heat storage system integrated with constant/varying (solar) heat sources

The objective of the present work is to investigate experimentally the thermal behavior of a packed bed of combined sensible and latent heat thermal energy storage (TES) unit. A TES unit is designed, constructed and integrated with constant temperature bath/solar collector to study the performance of the storage unit. The TES unit contains paraffin as phase change material (PCM) filled in spherical capsules, which are packed in an insulated cylindrical storage tank. The water used as heat transfer fluid (HTF) to transfer heat from the constant temperature bath/solar collector to the TES tank also acts as sensible heat storage (SHS) material. Charging experiments are carried out at constant and varying (solar energy) inlet fluid temperatures to examine the effects of inlet fluid temperature and flow rate of HTF on the performance of the storage unit. Discharging experiments are carried out by both continuous and batchwise processes to recover the stored heat. The significance of time wise variation of HTF and PCM temperatures during charging and discharging processes is discussed in detail and the performance parameters such as instantaneous heat stored and cumulative heat stored are also studied. The performance of the present system is compared with that of the conventional SHS system. It is found from the discharging experiments that the combined storage system employing batchwise discharging of hot water from the TES tank is best suited for applications where the requirement is intermittent.     

An irreversible-thermodynamic model for solar-powered absorption cooling systems

The ideal three-heat-reservoir cycle with constant internal irreversibilities and external heat transfer irreversibilities is used to model the absorption refrigeration machine of a solar operated absorption cooling system. Analytical expressions are obtained for the variation of the entropy transfer with storage tank temperature and the variation of the coefficient of performance (COP) with the cooling capacity of the plant. These expressions give the operating points for the maximum cooling capacity and the maximum COP. The results for ideal irreversible cycles are compared with those obtained by detailed simulation of the absorption cooling system. The effect of internal and external irreversibilities on the second-law efficiency of the plant is examined. The ideal cycles that include internal and external irreversibilities are found to give realistic limits and trends for the cooling capacity and the COP of solar powered absorption cooling systems.     

Numerical analysis of heat and mass transfer during absorption of hydrogen in metal hydride based hydrogen storage tanks

In this paper, hydriding in a cylindrical metal hydride hydrogen storage tank containing HWT5800 (Ti_0.98Zr_0.02V_0.43Fe_0.09Cr_0.05Mn_1.5) is numerically studied with a two-dimensional mathematical model. The heat and mass transfer of this model is computed by finite difference method. The effects of supply pressure, cooling fluid temperature, overall heat transfer coefficient and height to the radius ratio of the tank (H/R) on the hydriding in the hydrogen storage tank are studied. It is found that hydride formation initially takes place uniformly all over the bed and hydriding processes take place at a slower rate at the core region. Supply pressure, cooling fluid temperature and overall heat transfer coefficient play significant roles during the absorption of hydrogen. At the H/R = 2 both maximum bed temperature and the average bed temperature are the highest, and the hydride bed takes the longest time to saturate.     

Thermal behavior of curved roof buildings exposed to solar radiation and wind flow for various orientations

In this study air flow, solar radiation and heat transfer from a two dimensional curved roof with north-south and east-west faced are determined and results are compared with flat roof for the same size and orientation. Comparison are performed for their corresponding roof surface temperature, and heat flow for several roof rim angles and also for various wind flow velocities, as well as for different wind directions. Turbulence is modeled by RNG k–ε method and solar radiation distribution over the roof is determined based on an appropriate model applicable to hot arid regions of Iran. Solar radiation is calculated based on the summation of beam and diffuse radiation and ground reflected radiation. For certain inside roof temperature, over all heat transfer to the building is determined with day time for various wind flows and arc shapes and results are compared with flat roof. It was found that various wind flow condition over the vaulted roof makes substantial difference on the convection heat transfer coefficient and finally on the rate of heat transfer to the building with respect to flat roof. Based on heat transfer simulation, roof temperature, heat transfer convection coefficient and heat flow though the vault for different roof arrangement and flat roofs have been determined and advantages of specific vault orientation and wind direction are specified.