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Although of plastic grain dry it is a relatively simple procedure, but, below some circumstances, grain is cannot by out and out dry.
The factor that affects dry result has:
Dry temperature:
Quantity of heat is dozen of boiled water element and moisture absorption polymer between the key of join forces. When temperature of prep above some, the gravitation between water element and polymer catenary can be reduced greatly, lunt is taken away by dry air.
Dew point:
In desiccator, above all eliminate moist air, make contain very low remain moisture content (dew point) . Next, through heating air reduces its relative humidity. At this moment, pressure of dry airy vapour is inferior. Through heating, the water element of grain interior cast off bond force to manacle, diffuse to the air all round grain.
Time:
In the air all round grain, caloric is absorbed and water element diffuses to grain surface the time with proper need. Accordingly, colophony supplier should define the time that a kind of stock gets effective and dry place must be cost below proper temperature and dew point.
Air current:
Dry hot air delivers quantity of heat the grain in dry makings storehouse, the damp of eliminate grain surface, remand damp next in desiccator. Accordingly, must enough air current heats colophony dry temperature, and keep this temperature proper time.
Should appear when dry and bad problem, answer to discover a problem from face of the following tripartite:
1, desiccator state
When checking desiccator, should notice inhaler and tube particularly. The tube of the filter that is jammed or squash can reduce air current, affect desiccator thereby move;
The filter of attaint can pollute desiccative, control its moisture absorption capacity; Cracked tube may introduce humid ambient air in dry air current, cause desiccative premature moisture absorption and high dew point; The tube with heat preservation undesirable measure and dry makings storehouse also can affect dry temperature.
2, dry gas district
In dry gas district, ought to in makings storehouse entry point detects dry temperature, so that compensate desiccator,the loss is heated up mediumly in tube. The air temperature that expects the entrance is in the storehouse is low, because the adjustment of controller is undeserved,the likelihood is and lack heat-insulation layer, or contactor of heater component, heater, thermocouple or controller appeared breakdown. In addition, in monitoring whole and dry process everywhere the dry temperature, temperature when observing desiccative changes is fluctuant the condition is very fundamental also.
If stock comes out from desiccator hind did not get proper dry, should check dry makings storehouse to whether have enough large space in order to provide sufficient and significant dry time. Significant dry time is to show grain reveals the time in proper dry temperature and dew point actually. If grain is in,expect the retention period in the storehouse is insufficient, have to be less than proper dry. So, should notice the size of grain makings or broken makings and appearance, they can affect the accumulation density of dry makings and retention period.
One twists the hose that change or a filter that jam can restrict air current, affect the performance of desiccator. So, when if check desiccator,discovering this kind of problem, cannot judge air current enough. Here, a quick, handy, accurate method can detect desiccator air current is enough, measure stock namely the perpendicular temperature curve inside dry makings storehouse.
The dry time that assumes stock supplier is recommended is 4h, handle ability 100lb/h(1lb=0.4536Kg) . Should decide desiccator air current is enough, can measure the temperature curve inside dry makings storehouse, here, want the temperature that special attention is in in 4h(400lb) . If the 400lb inside dry makings storehouse expects the temperature of a place reached set value, can think throughput is enough so.
If there are 1h, 2h or the stock that 3h handles to get heating adequately only in dry makings storehouse, explain throughput cannot finish the stock that books yield to fall heat and dry. Heat insufficient likelihood makes clear, to this productivity, dry makings storehouse is too small, or air current jams as a result of filter or the circumstance such as tube attaint is restricted. Tolerance also can appear greatly too problem, not only wasteful the sources of energy, and bring about circumfluence air temperature tall, destroy the function of desiccative.
Circumfluence inhaler can prevent filiform stock to pollute desiccative, affect its moisture absorption performance. So that assure enough air current,these filter must keep clean.
Come out from desiccator top when dry air when, had released major quantity of heat. It is when desiccative temperature when limits of 120oF ～ 150oF, most desiccator is OK and efficient the job. If answer empty to enrage overheat of desiccate dry agent, can reduce its adsorptive capacity to the damp in dry air.
Should detect constantly the circumfluence air temperature of desiccator. When circumfluence air temperature is high, the likelihood explains to this productivity, desiccator size is too large, or the temperature when stock enters dry makings storehouse is high, for example, PET has been in dry before produced crystallization, perhaps be certain stock only merely (be like PET) the temperature limits with dry temperature normal prep above. Become tall to prevent circumfluence air temperature, should enrage the installation on the road in circumfluence only a heat exchanger, can ensure desiccative can be effective ground eliminate is dry the damp in air.
3, the second birth of desiccative and refrigeration
The moisture absorption ability of desiccative is finite, because its adsorptive this damp must pass second birth,be kept clear of. Its process is: When ambient air by inspiratory hind, enter air-blower through a filter, be sent a group of heater next. The air after heating passes desiccative bed. When the temperature of desiccative rises, release adsorptive damp. After hot air absorbs lunt to reach saturation, with respect to the air that be emited into. Before desiccative of high temperature second birth returns dry annulus way, must cool, ability restores the moisture absorption function of desiccative.
Dew point reading can help discovery a few problems, ought to monitor the cost of dry air dew point in whole and dry process so. The dew point reading when desiccator moves normally ought to be limits of 20oF ～ 50oF a inside linear, of course, change desiccative and the small wave motion that cause is normal. If desiccator movement is normal, the dew point low 30oF that the dew point that entrance of dry air is in should compare circumfluence air exit at least.
On the other hand, after desiccative changes, dew point appears immediately peak value, the refrigeration before showing desiccative is put is inadequate, make it cannot well adsorptive damp, the dew point of desiccative can fall after refrigeration normal level. If desiccative is cooling undeserved, will cause temperature occurrence peak value, temperature changes suddenly can reduce desiccative to get together to leaving content, amorphous polyester and certain nylon brand the drying capability that waits for heat quick material.
If desiccative bed changes hind dew point reading is normal, but before the dry cycle of desiccative ends dew point apace rises, the likelihood entered demonstrative ambient air to close gas district, cause desiccative premature moisture absorption. Another kind may be desiccative second birth not complete or by pollution. If dew point reading and reading of circumfluence air dew point are adjacent, show second birth enrages complete invalidation or desiccative got be polluted badly.
