Rolls of kraft paper stacked on a rack
Papermaking white water is repeatedly sheared and pumped around the circulation system; once micro-foam is carried with the stock to the wire section of the paper machine, pinholes and dark spots appear on the sheet, and the formation and strength of the finished paper suffer together.
Chemi Tech supplies defoamers for papermaking white water loops and stock preparation systems, drawn from the defoamer KM-1003 series. KM-1003 is a silica-free polymer system that resists both acid and alkali and withstands high temperature; it performs steadily in white water systems where the temperature runs high and the alkalinity is on the heavy side, and it can be diluted and compounded, so the addition cost stays controllable with it. Chemi Tech completes the compatibility comparison against the alkalinity, temperature and circulation ratio of the white water, and settles on the defoamer that fits for the customer.
Advantages of Chemi Tech Defoamers
Chemi Tech defoamer KM-1003 series is a silica-free polymer system whose defoaming action does not decay when the white water runs hot and alkaline; on top of that, it can be diluted and compounded, the diluted liquor stays uniform, and the addition cost is easy to control; and its knock-down and foam-suppressing actions are balanced, so the wire section of the paper machine no longer carries foam over; it is compatible with the stock system, and the formation and strength of the finished paper are not disturbed.
Industry Pain Points and Solutions
Foam in the white water loop is mostly not a matter of insufficient chemical dosage but of the hot, alkaline environment repeatedly weakening foam control; the consequence is pinholes on the sheet and a drop in the formation of the finished paper.
The first problem is the hot, alkaline circulating environment. The temperature and alkalinity of the white water system run high, ordinary defoamers fail quickly in that environment, and the foam rises again straight away. Chemi Tech's approach is to add the acid- and alkali-resistant, high-temperature-resistant KM-1003 at the white water return end, so that the agent is already working at the peak of carry-over.
The next difficulty is the continuous regeneration of micro-foam. Shear and drop at the wire section of the paper machine keep drawing air into the white water, and micro-foam has a small diameter and weak buoyancy, so standing alone hardly clears it. Chemi Tech's KM-1003 is balanced in knock-down and foam suppression, and holds down the regeneration of micro-foam continuously in the circulation section.
The last item is the addition cost. To hold foam suppression in a hot, alkaline environment, repeated top-ups are often needed, and the addition cost climbs with them. Chemi Tech compares durability against the white water circulation ratio and settles the addition level and the top-up points as one, so that unnecessary top-up frequency is reduced.
Typical Conditions and Verification
Customer: a papermaking producer in Zhejiang, for the white water loop and the stock preparation sections.
The white water at this plant came back from the loop with a thick layer of foam, the wire section of the paper machine carried foam over, pinholes and dark spots on the sheet were on the high side, and the formation of the finished paper was long constrained. The solution Chemi Tech defoamer gave for this was: against the alkalinity and temperature of the white water, KM-1003 was selected, the dosing point was set at the white water return end, and the addition level was banded by circulation ratio. After the solution was switched in, the foam in the white water thinned noticeably, pinholes on the sheet came down with it, and the formation of the finished paper returned to its normal range.
Frequently Asked Questions
Will a silica-free defoamer added to white water affect the retention of the stock or the strength of the finished paper?
The concern does need attention, since a few categories adsorb onto the fibres while knocking down foam and interfere with retention and strength. For white water systems, Chemi Tech has put KM-1003 through a compatibility comparison, and at normal addition levels retention and the strength of the finished paper are not affected. The specific addition level is set by the alkalinity of the white water and the circulation ratio, and Chemi Tech gives the recommended range after the compatibility comparison.