coated ball and paste ball of Phenomenon and treatment in cement grinding?

"coated ball" and "Paste Ball" is a common abnormal phenomenon in the cement milling operation.

First, "coated" and "paste" Definition of difference:

"coated ball": When the internal temperature is high, the ventilation quantity decreases correspondingly, and the grinding resistance increases correspondingly. Under the impact of the grinding body, the material can be carried on the charge, adsorbed on the grinding body, the lining plate and the bulkhead plate, and the fine material itself will be adsorbed by the different charge and form a small flake. This phenomenon is called "coated Ball". The higher the temperature in the mill, the finer the material is, the more serious the "ball" phenomenon.

"Paste Ball" is also called "Paste Mill": When the material water is large, the grinding temperature is low, the material is under the impact of the grinding body, adhesion in the grinding body, liner and bulkhead board, the mill ventilation volume is reduced, the grinding resistance increases, this phenomenon is generally called "Paste Ball". The larger the material moisture, the lower the temperature in the mill, the more serious the "paste ball" phenomenon.

Easy to distinguish between the two, in general, the temperature is high caused by the "ball", the water caused by the "paste ball."

Two, "coated" and "paste" the same place:

After the "coated ball" and "Paste Ball" happened, the same is the grinding body is wrapped in material, the lining board adsorbed a layer of material. In either case, the buffering effect is aggravated, the grinding sound is low, the grate gap between the bulkhead plate and the discharging grate is blocked by material, the feed quantity is forced to decrease, the fineness of the product is thickened (but the specific surface area is increased), and the current of the mill and the grinding hoist is decreased.

III. "coated ball" and "Paste Ball" processing method

1 the root cause of the "coated ball" is that the temperature in the mill is too high, and the reasons for the high temperature in the mill are as follows:

(1) The temperature of the grinding material is too high

(2) Bad ventilation in the mill

(3) Too little feed, or grinding machine under the condition of stop feeding for a long time

(4) The grinding body gradation is unreasonable, resulting in the increase of the temperature in the grinding. The size of grinding body is too large or the grinding capacity of the mill is uneven, which leads to excessive loading in the rear of the mill.

To deal with "bag ball", you must not use the method of reducing or stopping feeding, as with "full grinding". Otherwise, the grinding inside temperature is higher, "the ball" phenomenon is more serious. The method of handling the ball is as follows:

(1) Take measures to reduce the internal temperature of the mill, such as improving the internal ventilation, strengthening the water of the cylinder, reducing the temperature of the grinding materials.

(2) Adding the appropriate amount of dry slag, dry slag and other grinding materials to the cement mill.

(3) Adding a proper amount of grinding aid. such as the addition of 0.2% of the cement production of triethanolamine (concentration 30%), or paper pulp waste liquid (condensed to 1.2 ~ 2.0 waves of the United States), or 1.5 waves of the United States pulp waste liquid and triethanolamine mixture (triethanolamine for the mixture of 1/10). A few hours after adding the grinding aid, the mill can return to normal production.

(4) "Reduce the big and small", optimize the grinding body gradation. "coated ball" if the grinding capacity of the mill silos is uneven, then the appropriate amount of the ball should be removed or increased before the ball; if the ball diameter is too large, the ball should be replaced with a small amount of the ball and the ball should be graded again if necessary.

(5) The use of internal spray cooling system, because atomized water evaporation into steam absorption of a large number of heat, thereby effectively reducing the grinding temperature. At the same time, because the water vapor can eliminate static electricity, to avoid the cement adsorption and adhesion of the plate, so, the use of internal spray cooling system can fundamentally eliminate the "ball" phenomenon.

(6) To ensure the quality of the premise, increase the feeding capacity, increase the cyclic load.

2 in-mill temperature rise

After the "coated ball" on the mill grinding efficiency and cement quality of the adverse effects of the following aspects:

(1) The grinding efficiency of the mill is decreased, which is caused by the decrease of the grinding property of the material as the temperature increases. At the same time, due to the increase of temperature, fine dust is easy to be attracted by electrostatic attraction, resulting in sticky ball phenomenon, also reduces the grinding efficiency of the mill. Experiments show that the grinding material temperature exceeds 50 ℃, the mill output will be affected, more than 80 ℃, and the output of cement mill can be reduced to $number.

(2) The increase in the internal temperature will also cause gypsum (CASO4·2H20) dehydration into a half water gypsum (CASO4·1/2H20) or even produce some anhydrous gypsum. (CaSO4), causing cement to leave the coagulation. It is generally believed that gypsum dehydration into a half water temperature is 100℃-110℃.

(3) The increase in the temperature of the mill, but also the mechanical parts of the mill caused by adverse effects, such as the sliding shoe bearing temperature rise, lubrication decline, and even the sliding shoe bearing burnout, but also to speed up bag-type dust collector bag aging.

3 The root cause of the "paste ball" is the temperature drop in the mill, which leads to the following main reasons:

(1) The moisture of the mixture is large

(2) The gap between the bulkhead board or the grate plate is blocked by the poor ventilation in the mill

(3) Temperature drop, material temperature is low

(4) The feeding operation is not standard

In the boot feeding, especially when the temperature is low, to wait until a certain temperature rise of the cement can be used, feed volume is large to small, grinding tail fan throttle opening recommended to 5% or so to increase, until the grinding tail to improve the mechanical and electrical flow is significantly higher, at this point the grinding inside completely unobstructed, and then open the fly ash feeding Group, feeding process is strictly prohibited. Pulse feeding ".

Processing "Paste Ball", and seemingly deal with "full mill", in the detection of grinding cement temperature and gas temperature is low, timely reduction of feeding or increase ventilation, regular cleaning grate seam, increase the effective ventilation area can fundamentally eliminate the cement mill "paste ball" phenomenon. Otherwise, the grinding temperature is lower, "paste ball" phenomenon is more serious, grinding tail out of the material less, cement miller condition will be worse.

source:https://www.asxsa.co.za/

Author：jacker