In alumina and chemical production, evaporators are core critical equipment, and their operational standardization directly affects production efficiency, equipment lifespan, and operating costs. Many enterprises tend to fall into the "either extreme" misunderstanding when starting evaporators—either blindly overproduce to plant hidden dangers or be overly conservative to cause capacity waste. Today, combining frontline research experience, let's talk about the correct way to start evaporators.

Misunderstanding 1: Blind Overproduction, More Loss Than Gain

It has been emphasized repeatedly before that evaporator startup must be operated stably. Especially when the equipment is clean and has the best heat exchange effect, blind overproduction must be avoided. At this time, the heat exchange efficiency of the equipment is maximized, which seems to greatly increase output, but there are multiple hidden risks behind it:

? Caustic Carryover in Secondary Steam: Overproduction will lead to a sudden increase in steam volume, exceeding the system capacity, which is very likely to cause caustic carryover in subsequent secondary steam, affecting the quality of subsequent processes and causing material loss.

? Excessively High Material Temperature in the First Effect: Excessively pursuing output will forcibly increase the material temperature in the first effect, breaking the system's heat balance and affecting the overall evaporation effect and process stability.

? Accelerated Scaling and Equipment Lifespan Reduction: Under overproduction conditions, the flow and reaction state of materials in the heat exchange tubes are abnormal, and the scaling speed will be significantly accelerated, directly shortening the pickling cycle. Frequent pickling not only increases labor and chemical costs but also continuously corrodes equipment, greatly reducing equipment service life.

Misunderstanding 2: Overly Conservative, Capacity Waste

Contrary to blind overproduction, some enterprises have gone to the other extreme—deliberately reducing capacity to pursue an excessively long cleaning cycle, resulting in insufficient equipment output. During a previous survey of a top domestic alumina enterprise, such a problem was found.

The enterprise has extremely strict management requirements for evaporators, clearly stipulating that the cleaning cycle must be more than half a year. To meet this indicator, evaporation workshops deliberately reduce the steam volume and material temperature of the first effect during startup and dare not operate the equipment at full load. The final result is that the enterprise's evaporators generally fail to reach full capacity, with serious capacity shortage.

What's more noteworthy is that the enterprise previously used diasporite for production and later switched to gibbsite process. The evaporator area is already sufficient, but the equipment efficiency cannot be fully exerted due to conservative operation. When asked why they dared not increase production, the relevant person in charge said that the equipment needs to be pickled every two to three months under full capacity, which does not meet the company's requirement of "cleaning every six months".

In fact, it is a completely normal industry standard to clean evaporators every two to three months. Forcibly pursuing a cleaning cycle of more than half a year is essentially exchanging capacity for "superficial equipment longevity", which instead causes hidden losses such as low production efficiency and high cost allocation.

Correct Principle: Reach Full Capacity Without Overproduction, Balance Is Key

The core principle of evaporator startup is:Reach full capacity without overproduction, and maintain a reasonable cleaning cycle.

On the one hand, it is necessary to make the equipment reach the designed capacity to avoid capacity waste and ensure the efficient operation of the production process. Deliberately reducing production to extend the cleaning cycle will not only affect the overall production plan but also lead to an increase in unit product energy consumption and labor costs, which is more loss than gain.

On the other hand, resolutely put an end to large-scale overproduction, strictly operate in accordance with the designed parameters of the equipment to maintain the stability of the system's heat balance and material flow. At the same time, accept the normal cleaning cycle of two to three months, and find a balance between capacity and equipment lifespan through standardized pickling operations and optimized process parameters.

Typical Case: 9-Year-Old Evaporator Tubes Unreplaced, Confirming the Balance Principle

An amazing case was also found during the survey: a set of seven-effect evaporators provided by us for the alumina enterprise has been in operation for 9 years, and not a single heat exchange tube has been replaced. This case fully shows that there is no need to maintain equipment by "reducing capacity and long-term low-load operation". As long as we adhere to standardized operations and maintain a reasonable cleaning cycle, we can achieve the dual goals of long equipment lifespan and efficient operation.

Behind the 9-year unreplaced tubes is the strict implementation of the principle of "reaching full capacity without overproduction", the precise control of process parameters, and a deep understanding of equipment operation and maintenance laws—equipment lifespan is never obtained by "saving use", but guarded by "standardized use".

Conclusion

Evaporator operation is no trivial matter, and extreme operations will inevitably lead to losses. Whether it is blind overproduction pursuing short-term benefits or overly conservative operation sacrificing capacity, it will eventually lead to production imbalance and cost increase. Only by adhering to the core principle of "reaching full capacity without overproduction and reasonable cleaning" and avoiding extreme detours can evaporators not only output efficiently but also operate stably for a long time, escorting production.