降低农用碳酸氢铵含水量的方法探讨

该文分析了影响农用碳酸氢铵含水量的各种因素 ,从生产实际和经济效益的角度出发 ,提出用合适的添加剂和简易的干燥设备降低碳酸氢铵的含水量     

碳酸氢铵产品的组份与含氮,含水量的关系

本文就国内外对碳酸氢铵产品以含氮,含水量定级及计算中的不合理性进行了分析,通过分析并推导出计算碳酸氢铵产品中NH_4HCO_3、(NH_4) _2CO_3百分含量的公式。从而可计算出在含氮量或含水量确定、不同NH_3/CO_2摩尔比时碳酸氢铵产品各组成含量。文中所列数据,可作为判断含氮、含水量测定结果是否匹配的参考。     

一种提高碳酸氢铵肥效的添加剂的研究

为解决碳酸氢铵易分解、含水量高、易结块、提高其肥效的问题,目前普遍在碳酸氢铵生产过程中采用添加剂。本文对碳酸氢铵添加剂十五烷基磺酰氯合成过程中的影响因素及其使用中存在的问题进行了研究和分析。     

碳酸氢铵分解性能及其施肥方法探讨

为了探讨碳酸氢铵分解性能和施用方法,采用盐酸吸收氨的方法考察了温度和含水量对碳酸氢铵分解率和分解速率的影响。实验表明30℃以上分解速率和分解率明显提高,低含水量和干燥的环境能明显降低分解速率和分解率。采用大数据分析了我国气温变化和土壤温度垂直分布状况。根据试验与分析结果,结合玉米和小麦根系分布规律,得出结论:对于小麦和玉米,碳酸氢铵宜施肥于土壤温度低于30℃的20～40cm土壤层。     

含水碳酸氢铵的粒度对其分解活化能的影响

<正> 前言碳酸氢铵是我国当前最常用的氮肥之一。工业上生产的碳酸氢铵总含有一定的游离水,这些游离水的存在会促进碳酸氢铵的分解和结块,所以近年来人们对含水碳酸氢铵热分解的规律进行了一些研究。在此基础上,本文进一步用DTA法研究了一定含水量的碳酸氢铵的粒度对其分解活化能的影响。由于含水碳酸氢铵的分解过程服从园柱形对称的相界反应动力学方程: 2[1-(1-α)~(1/2)]=Kt[1] 所以我们对其DTA曲线采用了H.E.Kissinger的方法来处理,从不同升温速率的DTA曲线来求分解活化能。实验结果表明,含水量一定时,碳酸氢铵分解的活化能将随粒度的减小而减小,基本上是一线性关系。     

LCS系列碳酸氢铵定量包装机的运用

0 前言 无锡中阳包装技术有限公司（以下简称中阳包装公司）对碳酸氢铵包装机进行了长期的研究和实验,彻底解决了由于碳酸氢铵含水量大、流动性差、腐蚀性强、容易架桥结拱等严重影响包装的技术难点,经多次技术改进后,研制出的LCS系列碳酸氢铵包装机达到了包装速度快、精度高、稳定性好的技术要求。目前,该系列包装机已在碳酸氢铵、氯化铵（湿铵）、湿钾肥等包装中广泛应用,得到了用户的一致好评。     

D—AS碳铵添加剂性能与使用研究

本文重点介绍了Ｄ－ＡＳ碳铵添加剂性能，添加机理及其在农用碳酸氢铵生产中的使用，证明该产品能防止碳铵在生产中结块，降低碳铵产品的含水量，减轻工人的劳动强度，延长设备使用寿命，减少环境的污染，从而提高碳酸氢铵的质量和档次。     

沸腾层干燥碳酸氢铵的研究

一、前言碳酸氢铵是一种适用于各种士壤性能的良好氮肥,且在氨加工的技术经济上有很大的优越性。但化学稳定性较差,温度稍高即行分解。分解速度随湿盐含水量的增加而显著增高。为满足农业对氮肥目益增长的需要,改进碳酸氢铵稳定性的研究,具有重要意义。改进碳酸氢铵稳定性的方法,国内外都作了很多研究。但从工艺要求来看,考虑物料廉价易得、过程简单,一般说来还是采用干燥方法为宜。在各种干燥方法中,烟道室干燥装置生产强度低,氨损失大。气流干燥法国内已应用于生产,     

碳酸氢铵除油、除添加剂和提纯的工业技术

由于碳酸氢铵在生产过程中需加入磺酸盐类等助剂促进晶核形成、改善碳酸氢铵晶型、提高碳酸氢铵晶体和母液的分离度,从而来解决或降低碳酸氢铵结块的难题。但这些助剂的加入,给后续工业使用造成影响,应用范围也受限。将工业碳酸氢铵通过打浆洗涤、离心分离、气流干燥、母液除油除添加剂等组合技术,获得符合食品添加剂要求的碳酸氢铵。该技术成功应用于工业化生产,解决了高纯度碳酸氢铵供应紧张的局面,并提高了碳酸氢铵生产企业的经济效益。     

不同添加剂对碳酸氢铵分解性能的影响

考查了无机添加剂(硫酸镁和氯化钠)和有机添加剂(十二烷基磺酸钠和大豆油)对碳酸氢铵分解性能的影响。实验结果表明:无机添加剂抑制了碳酸氢铵前期的分解速率,但并不能降低碳酸氢铵累积分解率;有机添加剂对碳酸氢铵的分解具有较好的抑制效果。     

基于经验模态分解方法的纸张水分控制

针对于纸张水分信号的大时滞特性和噪声成分的非平稳特性所造成的水分控制系统控制效果差的问题,利用经验模态方法将水分信号分解为反映水分噪声信号结构的内在模态函数和反映水分信号总体变化趋势的趋势分量,滤除内在模态函数,并采用大林算法对趋势分量进行控制以克服水分控制系统中的大滞后环节.生产实践表明:该方法的控制效果优于PID算法或模糊控制算法.     

褐煤干燥后水分复吸的实验研究

空气湿度是产生复吸的重要条件,湿度越高复吸的程度越高;自然条件下,温度越高复吸速度越快;产物粒度越小复吸速度和复吸程度越大。深度干燥煤的复吸水主要发生在煤堆表面。研究了高温烟气干燥褐煤的水分复吸性能,结果表明,在6％～11％的全水含量范围内,干燥煤复吸后水分升高幅度基本一致。在此全水范围内干燥煤全水高低不会影响复吸结果。     

NONDESTRUCTIVE MEASUREMENT OF MOISTURE DIFFUSION COEFFICIENT IN WOOD DRYING

The computer tomography(CT image of wood was analyzed to estimate the moisture content from CT number. Comparing moisture contents, densities and CT numbers, moisture distributions were nondestructively determined by CT numbers detected with the scanner.

By periodically measuring CT images of the same cross section of specimens in drying, change of moisture distribution was computed. The coefficients of moisture movement at given positions inside the specimen were directly calculated from Fick's Law with known values of moisture content change, distance and drying time.

The diffiion coeficient was described as a function of various driving forces of moisture content, partial vapor pressure and chemical potential of moisture in wood. The results were comparable to data in the literature. Furthermore, it is shown that diffusion coefficients based on moisture content varies as a curve with the maximum value at about 15% m.c. during drying, and that the moisture content is actually adaptable to the driving force for moisture movement in wood because of capability over wide moisture content range.     

Modelling Cyclic Moisture Uptake in an Epoxy Adhesive

This paper presents a methodology for predicting moisture concentration in an epoxy adhesive under cyclic moisture absorption-desorption conditions. The diffusion characteristics of the adhesive were determined by gravimetric experiments under cyclic moisture conditions and the dependence of diffusion coefficient and saturated mass uptake on moisture history was determined. Non-Fickian moisture absorption was observed during absorption cycles while moisture desorption remained Fickian. The diffusion coefficient and saturated moisture content showed variation with absorption-desorption cycling. A finite element-based methodology incorporating moisture history was developed to predict the cyclic moisture concentration. A comparison is made between the new modelling methodology and a similar method that neglects the moisture history dependence. It was seen that the concentration predictions based on non-history dependent diffusion characteristics resulted in over-prediction of the moisture concentration in cyclic conditioning of adhesive joints. The proposed method serves as the first step in the formulation of a general methodology to predict the moisture dependent degradation and failure in adhesives.     

MODELING OF ROUGH RICE DRYING IN THIN VERTICAL COLUMNS

ABSTRACT

The solution of classical diffusion equation based on the assumption of average moisture diffusion coefficient did not adequately represent natural convection drying of rough rice in thin vertical columns exposed on both sides to hot air. Instantaneous moisture diffusivity coefficients determined from experimental drying curves decreased continuously with an increase in exposure duration and were linearly related to moisture ratio. The proponionality constant which was called apparent moisture diffusion coefficient was distinctly related to air temperature, relative humidity, and initial moisture content of rough rice. The modified moisture diffusion model using the instantaneous moisture diffusion coefficient was found to best represent the moisture removal from bulk rough rice.     

MODELING OF ROUGH RICE DRYING IN THIN VERTICAL COLUMNS

The solution of classical diffusion equation based on the assumption of average moisture diffusion coefficient did not adequately represent natural convection drying of rough rice in thin vertical columns exposed on both sides to hot air. Instantaneous moisture diffusivity coefficients determined from experimental drying curves decreased continuously with an increase in exposure duration and were linearly related to moisture ratio. The proponionality constant which was called apparent moisture diffusion coefficient was distinctly related to air temperature, relative humidity, and initial moisture content of rough rice. The modified moisture diffusion model using the instantaneous moisture diffusion coefficient was found to best represent the moisture removal from bulk rough rice.     

Effect of moisture content on mechanical properties,thermal and structural stability and extrudate texture of poly(vinyl chloride)/wood sawdust composites

Mechanical properties and thermal and structural changes of poly(vinyl chloride) (PVC)/wood sawdust composites were assessed with respect to the effect of moisture content, varying from 0.33 to 3.00 % by weight in the composite, for three different wood sawdust contents. The swell ratio and texture characteristics of the composite extrudates were also evaluated. Unique explanations were given to describe changes in the composite properties in terms of molecular interactions between PVC, cellulosic sawdust and moisture, such as dipole–dipole interactions, interfacial defects and bonding, fibre swelling, and moisture evaporation. The results suggest that at low moisture content the tensile modulus decreased and elongation at break of the composites increased with moisture content, the effect being reversed for high moisture content. Tensile strength decreased with increasing moisture content up to 1–2 %, and then unexpectedly increased at higher moisture contents. The effect of moisture content on flexural properties of the composite was similar to that on tensile properties. Impact strength of the composites was considerably improved with moisture content at low sawdust contents (16.7 wt%), and was independent of the moisture content at higher sawdust contents (28.6 and 37.5 wt%). A decrease in decomposition temperature with an increase in polyene content was evidenced with increasing moisture content, while the glass transition temperature did not change with varying moisture content. The extrudate swell ratio increased with the shear rate but remained unaffected by moisture content. The bubbling and peeling‐off in the composite extrudate occurred as a result of the evaporation of water molecules and the application of a high shear rate. Copyright © 2004 Society of Chemical Industry     

NONDESTRUCTIVE MEASUREMENT OF MOISTURE DIFFUSION COEFFICIENT IN WOOD DRYING

ABSTRACT

The computer tomography(CT image of wood was analyzed to estimate the moisture content from CT number. Comparing moisture contents, densities and CT numbers, moisture distributions were nondestructively determined by CT numbers detected with the scanner.

By periodically measuring CT images of the same cross section of specimens in drying, change of moisture distribution was computed. The coefficients of moisture movement at given positions inside the specimen were directly calculated from Fick's Law with known values of moisture content change, distance and drying time.

The diffiion coeficient was described as a function of various driving forces of moisture content, partial vapor pressure and chemical potential of moisture in wood. The results were comparable to data in the literature. Furthermore, it is shown that diffusion coefficients based on moisture content varies as a curve with the maximum value at about 15% m.c. during drying, and that the moisture content is actually adaptable to the driving force for moisture movement in wood because of capability over wide moisture content range.     

Kiln-drying optimization for quality pacific coast hemlock timber

The pacific coast hemlock or “hem-fir” is a dominant species mix in British Columbia that is difficult to kiln-dry; hence, many mills are quite conservative with their drying schedules. Furthermore, mills tend to dry hem-fir with no green moisture content presorting, thus promoting high moisture differences within and between dried timbers. In this study, application of green chain moisture-based sorting, coupled with a modified drying schedule, was considered to be a potential way to improve drying times, moisture content spreads, and lumber quality. Modified schedules coupled to three-group green moisture content presorting, i.e., mixed, low, and high, were compared to a standard industrial one. To evaluate the process and product quality, final moisture content variation between and within lumbers, drying rates, warp, surface and internal checks, shrinkage, and casehardening were assessed. Data analysis revealed that there was no significant difference between the drying runs in terms of final moisture content variation, except in the high initial moisture content group. In regard to the sorting, high initial moisture content sorting helped to reduce the final moisture content variation. In particular, the modified schedule, when there was a high initial moisture content sorting, did improve the uniformity of final moisture content in comparison to the industrial one.     

环保型聚碳酸亚丙酯复合调湿材料的性能研究

以溶液共混法将聚碳酸亚丙酯(PPC)、木质素、沸石、硅藻土制得复合材料,测试复合材料的吸放湿性能。结果表明:无机调湿材料吸放湿速度快,但湿容量小;有机调湿材料吸放湿速度中等或较慢,但湿容量大。而通过复合无机与有机调湿材料料,可以得到吸放湿速度快且湿容量大的调湿材料。