制粒工艺过程的水分控制课件

影响颗粒稳定度的因素 调制 20 环模 15 粉碎粒度 20 配方/原料 40 冷却 5% 蒸汽调制的基本作用 * 热水分交换使饲料原料软化，淀粉糊化 ，促进粉料颗粒在压粒过程中紧密结合， 提高颗粒饲料的稳定度，减少含粉量。 * 降低制粒电耗，提高产量，延长环模寿命 ，减少因摩擦生热导致的有效营养成分损 失。 淀粉糊化程度取决于：温度、水分与时间 制粒前的常规蒸汽调制，淀粉糊化度的提 高一般不超过五个百分数单位 压粒过程摩擦生热导致的淀粉糊化无助于 提高颗粒稳定度 蒸汽调制的基本作用 调制料温、制粒升温与淀粉糊化的关系 蒸汽调制的基本作用 高水分、长时间蒸汽调制，如湿法挤压 膨化的预调制过程，可使淀粉糊化度提 高约 20个百分数单位。 蒸汽调制的关键 蒸汽质量：什么是蒸汽质量？如何得到 高质量蒸汽 根据饲料类型和调制时间长短正确设定 调制气压 原料与成品水分控制 蒸汽调制过程的热交换 蒸汽热量的组成：表观热与潜热 潜热-物料升温的主要热量来源: 每凝结一个百分数单位的优质蒸汽，物料温 度大约上升 15 0C 蒸汽表 蒸汽质量 蒸汽表 overover 蒸汽质量 湿蒸汽蒸汽中含液态水, 热量低，易堵 塞模孔 蒸汽质量可用气态水在蒸汽中的百分数来 表示 测定蒸汽质量的方法 过热蒸汽或不饱和蒸汽 判定过热蒸汽的方法 理想的蒸汽：100饱和蒸汽 蒸汽质量的计算 蒸汽质量% =(W2xT2-W1xT1)/(W2-W1)-Hf/Hfgx100% W1=注入蒸汽前水重 W2=注入蒸汽前水重 T1=注入蒸汽前水温 T2=注入蒸汽前水温 Hf=测试压力下的表观热(查蒸汽表) Hfg=测试压力下的潜热(查蒸汽表) 蒸汽表 overover 蒸汽系统主要设备的选择与设定 锅炉 输汽管道内径的确定 汽水分离器 疏水阀 减压(稳压)器 流量控制阀 锅炉的选择与设置 Boiler Selection and Layout 燃料的选择要全面考虑供气稳定性、人工、燃料 价格及环境等因素 Fuel Type 锅炉的功率或供气量要留有余地 Boiler Size: Leave sufficient room 尽可能缩短锅炉与用汽设施之间的距离 Location of the boiler: close to the pellet mill ID (cm) = W x 3.53 v/30 W=蒸汽流量 (Steam flow),kg/min v=给定气压下的比体积 (Specific volume under given steam pressure),m3/kg (查表 ) 30 = 最大流速 (allowed steam flow velocity),m/s 输汽管道内径的确定 Sizing the Pipe 气水分离器 Steam Separator 根据机械原理将蒸汽中的水滴与蒸气分 开以得到优质蒸汽. Using a mechanical advice to remove water drip- lets from the steam and obtain high quality steam. 好的气水分离器可移走98%的水滴. Good separator can remove more than 98% of the water drip-lets 其功能为将凝积水(在进入调制器前)从 蒸汽系统中排出. To remove water condensate out of the steam system (before the steam going into the conditioner). 疏水阀应不时启闭使一定压力下的凝积 水移到常压的回收系统且不丢失蒸気. It must periodically open and close to allow the pressurized condensate to be removed in to an atmospheric condensate return system without losing steam. 疏水阀 Check Valve 只有气压稳定才能使气流稳定,从而保证制粒过 程稳定. Steady pressure is critical for smooth steam flow and hence smooth pelleting operation. 减压有助于提高蒸汽质量. Pressure reduction helps improving steam quality. 减压(稳压)器的主要参数:流量、调压范围及控 制的稳定性(可用变异系数度量). Parameters for consideration: Maximum flow (kg/hour), pressure range, pressure stability (expressed as CV%). 减压(稳压)器 Steam Pressure Reducer-Regulator 控制进入调制器的蒸汽流量.只有物料流量与蒸 汽流量同步控制才能实现稳定的制粒作业. It meters the steam flow going into the conditioning chamber- an important device for operator 调制器操作与流量应是线性关系. A linear response is required between control valve and steam flow. 一般的控制阀的操作与实际流量不是线性关系. The gate valve is non-linear - at half opening, small changes in setting results large steam flow variation. 流量控制阀 Steam Flow Control Valve 减压、分水、气压控制三合一 A separator - trap - pressure regulator “three in one”device. 流量控制阀在自动和手动控制条件下均与 流量呈线性关系. Linear steam flow control valves for both manual and automatic control system - Cospect Valve 蒸汽调制系统参数的设定 Parameter Settings in Steam Conditioning 考虑因素：调制时间、蒸汽质量、饲料配方. Factors to be considered: Retention time, steam quality and formulation/ingredients. 对于一般饲料配方，应在不塞机的前提下，尽 可能提高料温. In general, mash temperature should be conditioned “as high as possible” before reaching the “chock point”. 减压前后的压力比 Pressure Ratio before after Pressure Reducing Valve - 减压可使蒸汽中的水滴挥发. 减压幅度过大,在蒸 汽质量好时,可形成过热 (不饱和)蒸汽. Pressure reduction helps water drip lets flash off but may also produce a supper-heated steam if the pressure drop is too much and the steam quality already very high. 一般推荐: 3.5-4:1 General Recommendation: 3-4 to 1 进入调制室的蒸汽压力设定 Steam Pressure Setting before Conditioner 调制时间短，蒸汽质量好，宜采用低蒸汽压 (1.5 -0.5 kg /cm2 或 更 低)， 以争取热 交换时间(并降低能耗). Low pressure (0.5-1.5 kg/cm2) is preferred if retention time is short (20 sec or less). 调制时间长，可采用较高蒸汽压力。 Higher pressure works well (2-4 kg/cm2) if retention time is long (40 sec or more). 关键在于有足够时间完成热交换-释放潜热. The key is to give sufficient time for heat transfer - releasing latent heat. 调制温度700C 以控制水分避免塞机 Keep mash temperature700C to avoid moisture increase caused stickiness 可考虑采用较高蒸汽压力甚至过热蒸汽 Higher steam pressure - low steam flow, or supper heated steam may help 高乳清粉乳猪料蒸汽参数的设定 Steam Setting for High Whey Diet 延长调制时间有助于水分进入并软化粉料以提 高颗粒质量 Extended retention time helps moisture penetration and softens particles for better pellets. 调制时间测定(Measuring mean retention time): MRT (Sec.) = (3600xW)/(1000xP) where, W = 调制器内水分校正的物料量, kg Moisture adjusted mash weight in conditioner, kg P = 产量, MT/h Production rate, MT/h 蒸汽调制时间 Retention Time 蒸汽调制时间 Retention Time 延长常规调制器调制时间的简易办法:通过调节 浆片角度提高物料在调制器内的充满度. Extending Retention Time by Adjusting Pitch Angle 夹层(间接)蒸器的作用 The role of indirect steam . Extending Retention Time by Adjusting Pitch Angle Mash fill before adjustment thermomet er Conditioner Paddle Pitch Adjustment (Top View) Mash Fill after Adjustment 延长调制时间的设备 多层调制器 可变仰角调制器 熟化调制器 Ripenner DDC 制粒过程的自动控制 料流控制 蒸汽流控制 料温反馈控制，电流反馈控制 常规蒸汽调制的局限性 Limits to Traditional Steam Conditioning 高水分、低温原料限制料温升高。 Can not achieve high mash temperature when ingredient moisture is high and temperature is low. 解决途径：烘干-预热？投入机械能? 加压调制 ? Solution: Drying ? Pre-heating ? Mechanical energy input ? Pressurizing? Whats New ? - For Better Pellets - 制粒工艺过程的水分控制 控制关键点 调制前粉料水分: 水分低于12%在混合物机 加水(一般不超过一个百分点) 调制后水分可通过料温上升估测 成品水分: 通过冷却时间料层高度调节 以电容为基础的快速水分测定器： 不需样品粉碎 不需称量 测定误差不超过0.5百分数单位 手工操作系统，六秒中得结果,电脑自 动监测系统，每秒20个以上读数 关键设备 制粒问题解难案例 Pelleting Trouble Shooting- Case by Case Analyses 例 1(广东,1985) Case 1 (Guangdong) 问题: 产量偏低,环模寿命低 Problem: low production rate., die wearing to fast 现场观察: 进入调制器蒸汽压: 2.7kg/cm2, On-site observation: Steam pressure at conditioner 2.7 kg/cm2 问题所在?如何解决? Solution? 例 2 (美国,1990) Case 2 (US-1990) 问题: 兔颗粒质量差,含粉多.Problem: poor pellet quality in a rabbit diet. 现场观察: 未发现明显异常. 与工人座谈得知唯 一改变是粉碎玉米由厂外带加工. No significant problem found in pelleting operation. Only changes recently made was corn meal supplied from toll- milling by an outside contractor. 问题所在?如何解决? Solution? 例 3 (美国,1994) Case 3 (US-1994) 问题: 料温上不去,颗粒质量差,含粉多,产量低 Problem: Low mash temperature, poor pellet quality, low production rate. 现场观察: 给汽打滑, 减压前-后蒸汽压: 6.5-2.7, 手可握住疏水阀后水管. On site observation: surging when adding steam; steam pressure at boiler: 6.5 kg/cm, after conditioner: 2.7 kg; hands can hold on pipe after check valve. 问题所在?如何解决? Solution? 例