保定空压机设备销售公司

Maintenance and maintenance of plastic dryer

1. 干燥温度

1. drying temperature

热量是打开水分子和吸湿聚合物之间合力的关键。当高于某一温度时，水分子和聚合物链间的引力会大大降低，水汽就被干燥的空气带走。

Heat is the key to the resultant force between water molecules and hygroscopic polymers. When the temperature is higher than a certain temperature, the attraction between the water molecule and the polymer chain will be greatly reduced, and the water vapor will be carried away by the dry air.

2. 露点

2. dew point

在干燥器中，首先除去湿空气，使之含有很低的残留水分(露点)。然后，通过加热空气来降低它的相对湿度。这时，干空气的蒸汽压力较低。通过加热，颗粒内部的水分子摆脱了键合力束缚，向颗粒周围的空气扩散。

In the dryer, the wet air is first removed to contain very low residual moisture (dew point). Then, the relative humidity is reduced by heating the air. At this point, the steam pressure of dry air is low. By heating, the water molecules inside the particles get rid of the binding force and diffuse to the air around the particles.

3. 时间

3. time

在颗粒周围的空气中，热量的吸收和水分子向颗粒表面扩散需要一定的时间。因此，树脂供应商应详细说明一种物料在适当的温度和露点下得到有效干燥所必须花费的时间。

It takes time for the absorption of heat and diffusion of water molecules to the surface of particles around the particles. Therefore, suppliers of resins should specify the time required for effective drying of a material at suitable temperature and dew point.

4. 气流

4. air flow

干燥的热空气将热量传递给干燥料仓中的颗粒，除去颗粒表面的湿气，然后把湿气送回干燥器里。因此，必须有足够的气流将树脂加热到干燥温度，并且将这个温度维持一定的时间。

The dry hot air passes heat to the particles in the drying bin, removes the moisture on the surface of the particles, and sends the moisture back to the dryer. Therefore, there must be enough airflow to heat the resin to the drying temperature and maintain the temperature for a certain time.

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Two

解决塑料颗粒干燥不良的措施

Measures to solve the bad drying of plastic particles

1. 干燥器状况

1. desiccator condition

检查干燥器时，特别要注意空气过滤器和软管。被堵塞的过滤器或压扁的软管会降低气流，从而影响干燥器的运行.

Special attention should be paid to air filters and hoses when checking desiccator. The blockage filter or flattened hose will reduce the airflow and affect the drier operation.

损坏的过滤器会污染干燥剂， 抑制它的吸湿能力；破裂的软管可能将潮湿的环境空气引入干燥气流中，引起干燥剂过早地吸湿和高露点；保温措施不良的软管和干燥料仓也会影响干燥温度。

The damaged filter pollutes the desiccant and inhibits its moisture absorption; the broken hose may introduce moist ambient air into the dry air, causing the desiccant to hygroscopic and high dew point too early, and the poor thermal insulation hose and dry silo will also affect the drying temperature.

2. 干燥气路

2. dry gas road

在干燥气路中，应当在料仓入口处检测干燥温度，以便补偿干燥器在软管中的热损失。料仓入口处的空气温度低，可能是由于控制器的调节不当和缺少保温层，或者是加热器元件、加热器电流接触器、热电偶或控制器出现了故障。

In dry gas path, the drying temperature should be detected at the entrance of the silo to compensate for the heat loss of the dryer in the hose. The air temperature at the entrance of the silo is low, which may be due to the improper control of the controller and the lack of insulation, or the failure of the heater element, the heater current contactor, the thermocouple, or the controller.

此外，监测整个干燥过程中各处的干燥温度、观察干燥剂更换时的温度波动情况也很重要。

In addition, monitoring the drying temperature throughout the drying process and observing the temperature fluctuations during desiccant replacement are also important.

如果物料从干燥器出来后没有得到适当的干燥，则应检查干燥料仓是否有足够大的空间以提供充分有效的干燥时间。有效的干燥时间是指颗粒实际暴露在适当的干燥温度和露点中的时间。如果颗粒在料仓中的停留时间不够， 就得不到适当的干燥。

If the material is not properly dried after the dryer is out of the dryer, it should be checked to see if there is enough space in the dry silo to provide sufficient and effective drying time. Effective drying time refers to the time when the particles are exposed to the appropriate drying temperature and dew point. If the particle is not enough in the silo, it will not get the proper drying.

所以，应注意颗粒料或破碎料的大小和形状，它们会影响干燥料的堆积密度和停留时间。

Therefore, attention should be paid to the size and shape of pellets or crushed materials, which will affect the bulk density and residence time of dry materials.

一条扭折的软管或一个堵塞的过滤器都能限制气流，影响干燥器的性能。所以，如果检查干燥器没有发现这类问题时， 则无法判断气流是否充足。

A twisted hose or a clogged filter can restrict airflow and affect the performance of the dryer. Therefore, if the dryer does not detect such problems, it is impossible to determine whether the air flow is adequate.

在此，有一个快捷、简便、准确的方法可以检测干燥器气流是否充足，即测量物料在干燥料仓内的垂直温度曲线。

Here, a quick, simple and accurate method can be used to detect the adequacy of the air flow in the dryer, that is, to measure the vertical temperature curve of the material in the drying bin.

回流空气过滤器可以防止丝状物料污染干燥剂，影响它的吸湿性能。这些过滤器必须保持清洁以便保证足够的气流。

The reflux air filter can prevent filamentous material from polluting the desiccant and affect its hygroscopic performance. These filters must be kept clean to ensure adequate airflow.

要时常检测干燥器的回流空气温度。当回流空气温度高时，可能说明对于该生产率，干燥器尺寸过大，或者物料进入干燥料仓时的温度高，例如，PET已经在干燥前发生了结晶，或者仅仅只是某些物料（如PET）的干燥温度高于正常的温度范围。

The reflux air temperature of the dryer should be measured at times. When the temperature of the reflux air is high, it may be explained that the size of the drier is too large or the temperature is high when the material enters the dry silo. For example, the PET has crystallized before drying, or only some material (such as PET) has a higher drying temperature than the normal temperature range.

为了防止回流空气温度变高，只要在回流气路上安装一台换热器，就能确保干燥剂能有效地除去干燥空气中的湿气。

In order to prevent the reflux air temperature to be higher, just install a heat exchanger on the reflow road to ensure that the drier can effectively remove the moisture in the dry air.

3. 干燥剂的再生和冷却

The regeneration and cooling of 3. desiccant

干燥剂的吸湿能力是有限的，因此它吸附的湿气必须通过再生被清除。其过程是：当环境空气被吸入后，通过一个过滤器进入鼓风机，然后被送入一组加热器。加热后的空气通过干燥剂床。

The moisture absorption capacity of desiccant is limited, so its moisture must be removed by regeneration. The process is: when the ambient air is inhaled, it enters a blower through a filter and is sent to a set of heaters. The heated air passes through the drier bed.

当干燥剂的温度上升时，释放出吸附的湿气。当热空气吸收水汽达到饱和后，就被排入大气。高温再生干燥剂返回干燥环路前必须冷却，才能恢复干燥剂的吸湿功能。

When the temperature of the desiccant rises, the moisture adsorbed is released. When hot air absorbs water vapor, it is released into the atmosphere. The high temperature regenerative desiccant must be cooled before returning to the drying loop, so that the moisture absorption function of the desiccant can be restored.

露点读数能帮助发现一些问题，所以应当监测整个干燥过程中的干燥空气露点值。干燥器正常运行时的露点读数应当是20℃～50℃范围内的一条直线，当然，更换干燥剂而引起的小波动是正常的。

Dew point reading can help find some problems, so the dew point value of dry air in the whole drying process should be monitored. When the dryer is running normally, the dew point reading should be a straight line in the range of 20 to 50 degrees. Of course, the small fluctuation caused by replacement of desiccant is normal.

如果干燥器运转正常，则干空气入口处的露点至少应比回流空气出口处的露点低30℃。

If the dryer works normally, the dew point at the dry air inlet should be at least 30 degrees below the dew point at the return air outlet.

另一方面，干燥剂更换后，露点立刻出现峰值，表明干燥剂放入前冷却不充分，使它不能很好地吸附湿气，冷却之后干燥剂的露点会降到正常标准。如果干燥剂冷却不当，将导致温度出现峰值，温度骤变会降低干燥剂对离聚物、无定形聚酯和某些尼龙牌号等热敏材料的干燥能力。

On the other hand, after the desiccant is replaced, the dew point immediately peaks, indicating that the desiccant is not sufficiently cooled before the desiccant is put in, so that it can not absorb the moisture well. After cooling, the dew point of the desiccant will fall to the normal standard. If the desiccant is not cooled properly, the temperature will peak, and the sudden change of temperature will reduce the drying ability of the desiccant to the thermosensitive materials such as the ionomer, the amorphous polyester and some nylon grades.

如果干燥剂床更换后露点读数正常，但是在干燥剂的干燥周期结束前露点快速地上升，说明环境空气可能进入了闭合气路，引起干燥剂过早吸湿。

If the desiccant bed is replaced, the dew point readings are normal, but the dew point quickly rises before the drying period of the desiccant, indicating that the ambient air may enter the closed gas path and cause the desiccant to hygroscopic prematurely.

另一种可能是干燥剂再生不完全或被污染。如果露点读数和回流空气露点读数接近，表明再生气路完全失效或干燥剂受到了严重污染.

Another possibility is that the regeneration of desiccant is incomplete or contaminated. If the dew point reading is close to the return air dew point reading, it indicates that the regeneration gas path is completely invalid or the desiccant has been seriously polluted.