Study on cost reducing
of solution and dosing plant
two chamber pendulum type
three chamber flow-through type
By: Alltech Dosieranlagen GmbH
November 28, 2000
Study by Alltech Dosieranlagen GmbH to exhaust the cost-reducing potentials when using two-chamber pendulum type plants in comparison with the three-chamber preparation plants. 阿尔泰克计量设备有限公司就两箱摆式加药装置和三箱加药装置在降低溶液制备成本可能性方面进行了研究。
High operating costs make the search for means and ways to reduce the prices inevitable. 高运行费用使寻找降低价格的方式和手段之研究不可避免。
Increased costs involved with waste disposal, higher costs involved with the supply of drinking water and that of flocculent are just a few examples, which mean increased operation costs for the user of dewatering and flocculent plants. The question is becoming more and more urgent: Where can we find ways and means to reduce those costs. 增加的成本费用包括废物的处理，饮用水以及絮凝剂的供应。这仅仅是若干方面。这些方面对于排水和絮凝剂装置的用户来说，就是运行成本的增加。我们在哪里才能找到降低这些成本的方法呢？这一问题变得越来越迫切。
The study carried out by Alltech Dosieranlagen GmbH answers this question. It shows potential to save on drinking water, auxiliary flocculent products and costs for maintenance, when two-chamber pendulum-type flocculent preparation plants are used.
Object of the study and structure of the survey
Object of the study were the different types of plants produced by a number of manufacturers. All those plants were tested at their individual sites under normal working conditions. For the operation of these plants were used liquid as well as powder flocculent found in different categories on the market.
The tests and the test results have been limited on fully automatic, continuously operating preparation plants and covered the following 2 types of plants:
1). Three-chamber preparation plants (flow-through system)
2). Two-chamber plants (preparation in batches)
Both types of plants are adequate for continuous operation.
1. Preparation plants with a flow-through system
1.1. How does a flow-through plant works, and what kind of problems could occur?
Flow-through plants are mostly designed as three-chamber plants. The method for constructing the tanks may be different but the principle remains the same:
1.1.1 In the make-up chamber auxiliary flocculent is poured in with water.
An important factor here is the intensive dispersion of auxiliary flocculent through solution water before it comes in make-up chamber. Otherwise conglomerates cannot be dissolved by the agitator.
1.1.2 In the next step, newly added solution presses the prepared solution in the ageing the next step, newly added solution presses the prepared solution in the ageing chamberscolved by the be different but the princhamber. 接下来，新加入的溶液会压在熟化箱里的溶液上。
Prior to this phase, the agitator mixes the solution contained in the make-up chamber. In this chamber, we could not detect a definite retention period. Un-matured products were quickly swirled by the agitator and compressed to overflow. 在这一阶段之前，搅拌器搅拌制备箱中的溶液。在制备箱中，我们检测不到确切的存留时间。没有熟化的溶液很快被搅拌机搅拌并压到溢流端。
1.1.3 Afterward, “matured”(!) solution contained in the ageing chamber is compressed in the same manner into the dosing chamber.
Due to the fact that an agitator to homogenize the solution is placed also in the ageing chamber, we will face the same kind of problems as for the make-up chamber. Here also, we could not detect a definite retention period although the agitator of the ageing chamber will be stopped when new solution is poured in.
1.1.4 Some manufacturers have a third agitator installed in the dosing chamber, from where the ready-to-use solution is metered.
When an agitator should be mounted in the dosing chamber, please not that the quality of the solution becomes lower! It will have a longer ageing period avoid having the solution mixed in the dosing chamber.
Test with different types of diffusers built in the chambers were negative and no distinct improvement in the characteristics of the plant were achieved.
1.2 Result of the survey with regard to the flow-through plants
On all flow-through plants and after adding dye to auxiliary flocculent, we have obtained following results in respect of the maturing period:
The maturing period in flow-through plants has nominal capacity of 8-10 minutes at the maximum.
After this period, the already dyed solution flows into the dosing conduit. We could detect non-diluted powdery residues in the micro-filters.
1.3 The effect this has on “paper Industry” as example
For Paper-making machines as well as for staining cloth from filter-presses, the above mentioned mis-performance can have negative results. You will have paper of low quality (wrong batch) and the filtering cake will stick onto the clothes of the filter press. No doubt the filter-tissue will have a shorter life-time. Another negative aspect is that non-matured solution which has no flocculating effect and is thrown away together with the dewater sludge.
Considering the size/capacity ratio, a flow-through plant becomes advantageous only then, when the solution does not flow directly in the process but has enough time to mature (in dosing conduit or in a storage tank).
If the solution should flow directly into the process, we advise against using a flow-through plant. This negative result is even higher, when the make-up concentration is high. The reason is that, when the make-up concentration is high, so is the viscosity of the solution. The agitators can no longer homogenize the solution contained in the chamber. At the same time, the newly poured solution with low viscosity will look for the easiest way to get into the next chamber. In this way, a flow-through channel is formed from the input point up to the discharge point.
This short-circuit-flow will not use the full volume of the chamber. With the result, the ageing period will be further reduced. You can disregard this result only when the output is low (in relation to the 1/2 of the chamber volume) and by low make-up concentration (0.05%~0.1%).
2. Two-chamber plants (Operation by batches)
2.1 How does a two-chamber plant function?
With the two-chamber plant, make-up is done in batches and allows a continuous discharge. The two-chamber plants can be divided into two groups.
In type 1, each chamber has a definite function. One chamber is used for preparation and the other chamber for metering the product. In the first chamber the solution is prepared and matured which then flow into the dosing chamber or can be pumped by means of a transfer pump.
Type 2 is a two-chamber pendulum plant, such as the CONTINUFLOC system of Alltech Dosieranlagen GmbH (see flowsheet on page 8). In one of the chamber the make-up process will start and left to mature, whereas the matured solution in the other chamber can be discharged at the same time. The discharging of one of the chambers is finished, the discharge can be switched over to the chamber in which the solution is matured. Thus the plant had a continuous discharge. When the discharge of one chamber is finished, the pendulum filling distribution channel can switch from the full chamber to the empty one automatically and start the filling of powder and solution water. Thus the plant can have a continuous preparation.
In the case of two-chamber pendulum type plants, it is essential to have an intensive dispersion prior to pouring in the solution!
In two-chamber make-up plant, a high make-up concentration should cause no problem, because there is no risk of a short-circuit-flow.
2.2 Result of the survey on two-chamber plants
When a two-chamber plant is functioning as detailed in the layout plan, then the quality of the solution is perfect because the maturing time has been reached.
Necessary condition for respecting the maturing time is: Tank should be large enough to corresponding to the discharge capacity; for plants where transfusing should be done, the period of transfusing should be added to the maturing time. When all these conditions are met, then the maturing time can be adhered to.
Please not: when the make-up concentration is high, the transfusing time will increase. 请注意：如果制备浓度提高，溶液的输送时间会相应延长。
Advantages of the two-chamber pendulum type plant compared to plants necessitating transfusing are:
The Plant has small dimension and yet give the same output
(thus to save the space)
Transfuse pumps will become redundant and are not high in size
2.3 Conditions when the maturing time is adhered to?
Quantity of flocculent calculated during the planning time or in the laboratory study will corresponding with the quantity actually required if the maturing time is adhere to. 在试验策划期间以及在实验室研究阶段计算出的絮凝剂量和熟化时间所需的量完全相同。
We could not detect negative effects on the other remaining equipment.
The results of the tests mentioned above highlight the advantages of the two-chamber plants against the flow-through plants when following conditions are met. Among all the two-chamber plants the best alternatives are offered by the two-chamber pendulum type plants with the best solution quality.
With regard to the costs involved with operating the plant, here are some results: With identical processes you will have upto 20% saving on flocculent when you use a two-chamber pendulum type Continufloc plant instead of a three-chamber flow-through plant. With the three-chamber flow-through plant, you will throw away 20% of the auxiliary flocculent.
A further advantages of the two-chamber pendulum type CONTINUFLOC plant is the saving on quantity of drinking water. For the preparation process, you will still use drinking water, but for the post-dilution, you can use cleaned swage water. For the two-chamber plants, you will use less drinking water, because the make-up concentration can be higher. For example, if you select a 0.5% make-up concentration instead of 0.1%, you will reduce the consumption of drinking water by 80%.
The high percentage in make-up concentration will further mean a smaller tank and thereby saving in space.
Minimum wear and low maintenance costs speak also for the advantages of a two-chamber plant.
PS：Enclosed the folowsheet of Alltech two-chamber pendulum-type solution and dosing plant Continufloc
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