基于步进式加热炉数学模型的氧化烧损预测模拟

针对钢铁企业的氧化烧损问题,用数值模拟的方法进行预测分析。利用CFD流体计算软件建立了炉内流动、燃烧、辐射、钢坯导热和氧化烧损模型,流动模型采用k—ε湍流模型,燃烧采用PDF燃烧模型,辐射换热模型采用离散坐标（DO）辐射模型,热流密度做为钢坯导热的边界条件,模拟钢坯在实际工况下的结果表明,氧化铁皮的快速增长期是在钢坯入炉50～120min之间,位于加热段;在不同均热时间下,钢坯氧化率随均热时间呈线性增长。据此结论,现场操作人员可通过强化加热段加热能力的手段减少钢坯在加热段的停留时间或热装钢坯调整总的在炉时间来降低钢坯氧化烧损率以提高钢坯加热质量。     

冶金步进式加热炉钢坯加热过程全尺寸数值研究

为了深入了解冶金步进加热炉中钢坯的换热过程，以一种新型燃料分级燃烧器为核心，以某钢厂1422号线3号炉为研究背景，建立了1∶1的全尺寸加热炉模型，同时采用稳态模拟与瞬态模拟结合的方法，研究了钢坯静止在加热炉均热段时的加热过程，得到了此时钢坯的温度分布情况，结果显示：该新型研究方法能够准确地描述步进加热炉加热钢坯时的传热情况；均热段的温度比其他各段的温度约高100℃;采用均热段加热时，顶部燃烧器的高温烟气会绕到钢坯下方对下表面进行加热，使钢坯下表面升温更快；加热60 min时钢坯已经达到目标出炉温度，而且温差最小，为9.83℃,随后由于均热段的二次加热温差反而增大，最终温差为17.42℃;所述工况条件下，钢坯达到目标温度时所用的加热时间和均热时间共64 min,与实际估算的时间80 min相差16 min,基本符合实际情况。     

实验炉内钢坯传热过程及其氧化烧损的数值模拟研究

以实验加热炉为研究对象,建立三维非稳态钢坯加热过程的氧化烧损模型,并根据等效热阻法和等效质量法,将钢坯加热时氧化层的动态增长过程,转化为氧化层的当量导热系数和当量密度的动态变化过程.基于数值模拟方法,研究了实验炉内钢坯加热过程中表面氧化烧损量以及氧气浓度、所处位置的氧化层对钢坯加热过程的影响及其氧化烧损量随时间变化规律.结果表明:在钢坯加热的过程中,氧化层增大了钢坯与烟气之间的换热热阻,加热到最终温度时,换热热阻是原来的2倍,钢坯升温速率明显减小;在炉内的加热时间越长,钢坯氧化烧损逐渐增加,到一定程度之后趋于平缓;当加热到相同温度,氧气浓度从0.41％升至0.995％时,氧化烧损量从9.5 kg/m2增加到16.8 kg/m2.     

管坯加热炉数学模型

无缝钢管管坯加热炉采用转底式环形加热炉，其主要优点是金属氧化烧损小（达0．5％），单位燃烧量小（〈60kg／t），炉子有效利用系数高（约50％）。此外，可完全实现加热自动化，操作简单，人员配备少。建立了该种加热炉的数学模型，其中估计到了圆形钢坯的放置位置及不对称加热条件。利用该模型进行计算需已知的参数为：废气温度、炉子生产率、钢种、料坯尺寸、炉内料坯之间的距离、料坯入炉温度、料坯出炉断面温差限制值、料坯断面最终温度梯度。     

加热炉降低氧化烧损的实验研究

以某加热炉为研究对象,研究加热炉加热制度、炉内加热气氛对钢坯氧化烧损的影响,并依据实验结果对水钢加热炉加热制度进行合理优化,达到减少钢坯氧化烧损,降低生产成本的目的。通过本研究,加热炉钢坯氧化烧损得到了明显的控制。     

钢坯炉内加热过程数值模拟

建立了步进式加热炉内钢坯加热过程的物理模型和数学模型,并对微分方程进行离散,采用Visual Basic语言编程计算了钢坯内部温度变化情况,给出加热过程中钢坯内部各点在不同时刻的温度分布曲线,分析了人炉温度、加热时间等加热条件对加热过程钢坯温度的影响,计算结果可为钢坯加热过程的优化提供重要的参考依据。     

步进式加热炉内钢坯水冷黑印的模拟研究

采用全隐式有限差分法,建立了步进式加热炉内钢坯温度场的数值计算模型,编制了钢坯加热过程的模拟软件。分别对不同工况下的钢坯加热过程进行模拟计算,得到了滑轨结构、滑轨高度和滑轨质材等对钢坯出炉温度分布和黑印温差的影响。为消除黑印,提高钢坯加热质量提供了科学依据。     

蓄热式加热炉加热过程在线控制数学模型研究

蓄热式加热炉是一种蓄热式换热器与常规加热炉的结合体，整体结构包括炉体、蓄热室、换向系统、供风系统、排烟系统等。采用蓄热式燃烧技术，能够帮助加热炉达到更高的炉温，从而进行工业加热生产。蓄热式加热炉的优点在于能够使炉温分布均匀，根据不同需求对炉温进行调节，大大改善加热质量，提升加热产品的合格率。在全面分析蓄热式加热炉传热机理的基础上，建立了物理和数学的3D模型来描述炉内传热和加热过程。利用CFD软件对整个炉子的燃烧过程进行模拟。最后，对整个炉内的流动和温度曲线进行了深入研究，详细揭示了炉内的流动特性和温度分布规律，对蓄热式加热炉的合理设计和优化控制具有重要理论意义和实践价值。     

辊底式连续热处理炉钢坯二维传热过程数学模型的研究

以某公司拟建的辊底式连续热处理炉为研究对象,在详细分析其传热机理的基础上,针对其钢坯厚度变化较大的特点,建立了钢坯在炉内连续加热和摆动加热过程数学模型,采用数值计算方法对其进行了仿真计算,并利用设计大纲提供的数据间接验证了所建模型的正确可靠性。所开发的辊底式热处理炉计算机数值仿真系统可以动态模拟不同燃料、不同规格的钢坯在炉内的运行状况及其钢坯各典型点的温度变化规律;可以确定在不同的热处理工艺制度下、不同规格的钢坯所需要的最佳运行方式和最佳工艺制度。     

加热炉的节能控制

文章从描述钢坯内部不稳定导热的偏微分方程及相应的边界条件出发，研究了描述钢坯热状态的离散状态空间模型。每次推钢后通过计算机多次模拟钢坯在加热段和均热段内的加热过程，采用遗传算法选出最优的加热炉炉温和推钢时间。以此参数控制加热炉，从而达到提高钢坯加热质量，进而提高钢材的质量以及节能的目的。     

Transient radiative heating characteristics of slabs in a walking beam type reheating furnace

Transient radiative heating characteristics of slabs in a walking beam type reheating furnace is predicted by the finite-volume method (FVM) for radiation. The FVM can calculate the radiative intensity absorbed and emitted by hot gas as well as emitted by the wall with curvilinear geometry. The non-gray weighted sum of gray gas model (WSGGM) which is more realistic than the gray gas model is used for better accurate prediction of gas radiation. The block-off procedure is applied to the treatment of the slabs inside which intensity has no meaning. Entire domain is divided into eight sub-zones to specify temperature distribution, and each sub-zone has different temperatures and the same species composition. Temperature field of a slab is acquired by solving the transient 3D heat conduction equation. Incident radiation flux into a slab is used for the boundary condition of the heat conduction equation governing the slab temperature. The movement of the slabs is taken into account and calculation is performed during the residence time of a slab in the furnace. The slab heating characteristics is also investigated for the various slab residence times. Main interest of this study is the transient variation of the average temperature and temperature non-uniformity of the slabs.     

轧钢加热炉温度均匀性和氧化烧损的优化

某1 700线加热炉经过5年多的生产实践,存在沿板坯长度方向温度均匀性较差和氧化烧损率偏高的问题。通过出钢端斜炉底改造、更换高温区的耐热滑块、均衡南北供热负荷、合理控制炉压、调整空燃比等方案的实施,使得板坯沿长度方向温差降到30℃以下,板坯的氧化烧损率降到0.95%,很大程度上提高了加热炉的技术水平和加热质量。     

A heat transfer model for the analysis of transient heating of the slab in a direct-fired walking beam type reheating furnace

A mathematical heat transfer model for the prediction of heat flux on the slab surface and temperature distribution in the slab has been developed by considering the thermal radiation in the furnace chamber and transient heat conduction governing equations in the slab, respectively. The furnace is modeled as radiating medium with spatially varying temperature and constant absorption coefficient. The steel slabs are moved on the next fixed beam by the walking beam after being heated up through the non-firing, charging, preheating, heating, and soaking zones in the furnace. Radiative heat flux calculated from the radiative heat exchange within the furnace modeled using the FVM by considering the effect of furnace wall, slab, and combustion gases is introduced as the boundary condition of the transient conduction equation of the slab. Heat transfer characteristics and temperature behavior of the slab is investigated by changing such parameters as absorption coefficient and emissivity of the slab. Comparison with the experimental work show that the present heat transfer model works well for the prediction of thermal behavior of the slab in the reheating furnace.     

Optimum residence time analysis for a walking beam type reheating furnace

A 3D unsteady numerical simulation of a reheating furnace was performed to obtain the optimal slab residence time. Too long residence time decrease the efficiency of the reheating furnace, whereas too short residence time cannot satisfy the required heating quality of a slab. The total five cases of residence times – 6032 s, 6496 s, 6960 s, 7424 s and 7888 s – were investigated for the optimum residence time analysis with the two slab requirements, those of emission temperature and uniformity. In this study, the slab emission temperature should be in the range between 1373 K and 1573 K. The skid mark severity of an emitted slab should be lower than 50 K to satisfy the uniformity requirement. The numerical analysis was done for the identical geometry and operating condition of the reheating furnace using FLUENT. Slabs were assumed to move very quickly that it took no time for them to move next positions. The quick movements of slabs were processed with the own developed User-Defined Function program. Among the five cases of residence times, the residence time of 7427 s turned out to be most efficient.     

骨盆骨折并发动脉血栓形成一例

建立了连铸板坯直接热装加热数学模型,并用有限差分法进行求解,获得了各期加热温度分布及加热时间,此模型可用于连铸铸板坯直接热装加热制度的确定。     

Investigation of the slab heating characteristics in a reheating furnace with the formation and growth of scale on the slab surface

In this work, the development of a mathematical heat transfer model for a walking-beam type reheating furnace is described and preliminary model predictions are presented. The model can predict the heat flux distribution within the furnace and the temperature distribution in the slab throughout the reheating furnace process by considering the heat exchange between the slab and its surroundings, including the radiant heat transfer among the slabs, the skids, the hot combustion gases and the furnace wall as well as the gas convection heat transfer in the furnace. In addition, present model is designed to be able to predict the formation and growth of the scale layer on the slab in order to investigate its effect on the slab heating. A comparison is made between the predictions of the present model and the data from an in situ measurement in the furnace, and a reasonable agreement is found. The results of the present simulation show that the effect of the scale layer on the slab heating is considerable.     

热解一步反应模型在煤燃烧模拟中的验证

本文采用高温沉降炉对四种褐煤进行了高温快速热解的实验研究,考察了热解温度（1 000℃、1 100℃、1 200℃）和停留时间对热解过程的影响.得到了四种褐煤的热解动力学参数,建立了热解一步反应模型.采用FLUENT数值模拟的方法,对四种褐煤在EFCM中的燃烧过程进行了模拟.燃烧过程的热解模型采用实验所得一步反应模型,通过模拟值与实验值的对比验证了实验所得热解一步反应模型的可靠性.     

A semi-analytical method to study the temperature evolutions of a slab and a semi-infinite target for plasma immersion ion implantation

The problems of heating a slab of finite thickness and a semi-infinite target with repetitive high negative bias voltage pulses in contact with a plasma are solved by using the two-dimensional Laplace integral transform technique. The plasma is composed of a collisionless presheath and sheath on an electrically negative biased wall, which partially reflects and secondarily emits ions and electrons. The heating of the workpiece from the plasma accounting for the presheath and sheath is determined by kinetic analysis. This work proposes a semi-analytical model to calculate the temperature evolutions and the melting times of the front surface of a slab and a semi-infinite target, and provides quantitative results applicable to control the temperature evolutions and the melting times. The predicted surface temperature of the slab as a function of time is found to agree well with experimental data. The effects of dimensionless pulse parameters, including the pulse duty cycle and pulse bias voltage, on the melting time and heating rate of the front surface are obtained. The results show that the temperatures and heating rates of the front surface of the slab and target increase with pulse parameters. The melting times to initiate the melting at the front surface are strongly dependent on the pulse parameters. The heat flux transport to workpiece from plasma is important to increase the surface temperature of the workpiece when the bias voltage is switched-off for low pulse duty cycle and low pulse bias voltage. The temperature of the workpiece is underestimated when not accounting for the heating effects during the pulse-off duration for low value of pulse parameters.     

连铸连轧辊底式加热炉薄板坯的温度场计算

分析了CSP工艺中辊底式加热炉及炉中板坯的换热特性,建立了板坯换热的二维非稳态数学模型,用差分法计算出了加热炉中不同时刻板坯断面的温度场,给出了板坯在加热炉中的温度变化曲线,为优化加热炉的加热制度提供了理论依据。