VRM Grinding Additives for Mill Stability With Less Water Spray
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Solution Overview
Problem
Vertical Roller Mills (VRMs) face instability issues during cement grinding, leading to vibrations that can damage the mill and affect cement properties due to pre-hydration caused by excessive water spraying, which negatively impacts cement strength and setting times.
Innovation Solution
The use of alkanol amino acid compounds or their disodium or dipotassium salts, such as ethanol diglycine, as grinding stabilizing additives reduces the water spray requirement, minimizing pre-hydration and stabilizing the milling process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If water spray is increased to stabilize the VRM during grinding, then mill stability improves, but pre-hydration of cement increases leading to reduced cement strength and delayed setting times
Solution Approach 1:
A grinding stabilizing additive is introduced as an intermediary substance between the water spray and the cement clinker. This additive allows the water spray to stabilize the mill by reducing vibrations without directly contacting and hydrating the cement particles, thus mediating the conflict between mill stability and pre-hydration prevention
Solution Approach 2:
The patent replaces the mechanical stabilization method (direct water spray onto the grinding bed) with a chemical stabilization method (using grinding stabilizing additives). This substitution changes the mechanism from mechanical cooling and vibration damping through water to chemical modification of the grinding process through additive interaction with the mill components
2Strength
If water spray is reduced to minimize pre-hydration, then cement strength and setting times improve, but mill stability deteriorates due to increased vibrations
Solution Approach 1:
The grinding stabilizing additive serves as a mediator that enables low water spray operation. It absorbs the stabilization function, allowing water spray to be reduced to minimal levels needed only for temperature control while the additive maintains mill stability through its interaction with the grinding process
Solution Approach 2:
The patent changes the chemical parameters of the grinding system by introducing specific additives (such as carboxymethyl cellulose, sodium hexametaphosphate, or their combinations) that modify the friction and vibration characteristics of the grinding bed, enabling stable operation at reduced water spray parameters
3Object-affected harmful factors
If grinding aid is used to reduce water spray, then pre-hydration decreases improving cement properties, but additional additive complexity is introduced
Solution Approach 1:
The grinding stabilizing additive performs multiple functions simultaneously: it stabilizes the mill by reducing vibrations, enables reduced water spray operation, prevents pre-hydration of cement, and in some embodiments also acts as a grinding aid or cement additive. This multi-functionality reduces the need for separate additives for each purpose
Solution Approach 2:
The patent employs composite additive systems combining different substances (such as carboxymethyl cellulose with sodium hexametaphosphate, or various grinding aids with cement additives) that work synergistically to achieve mill stabilization and pre-hydration prevention, leveraging the complementary properties of each component
Data Source
AI summary
Method for grinding a solid in a vertical roller mill (VRM) and a cement composition prepared by the disclosed methods. A method comprises grinding a solid comprising a cement clinker under a water spray in the presence of a grinding stabilizing additive, wherein the grinding stabilizing additive comprises: (i) an alkanol amino acid compound or a disodium or dipotassium salt thereof having the structural formula:(ii) a glycol; or a mixture of (i) and (ii), wherein the water spray level is reduced by at least 5% compared to a control. Cement compositions prepared by the disclosed methods have the pre-hydration level (Wk) equal to or less than 1.5%. The values and preferred values of R1-3 are disclosed herein.