| 摘要 |
1 A system for mixing a cement slurry, comprising a liquid material supply (101) including a device (104) for measuring the amount of liquid material supplied a solid material supply (108), a mixer including a tub (114) which receives the liquid and solid materials and includes an output (124) for delivering materials from the mixer to a delivery system, a flow meter (128) in the output (124) a computing device and a computing device, characterised in that the system further comprises a device (120) for measuring the amount of material in the mixer, the computing device receives the output from the device (120) for measuring the amount of material in the mixer and from the flow meters (104, 128) and is arranged to calculate the variation in the amount of material in the tub (114) over time, and the solid fraction of the mixture and the calculated solid fraction is used to control the relative amounts of solid and liquid material added to the mixer. 2. A system as claimed in claim 1, wherein the flow meters are selected from mass flow meters and volumetric flow meters. 3. A system as claimed in claim 2, wherein the flow meters are selected from Coriolis meters and electromagnetic meters. 4. A system as claimed in any preceding claim, wherein the mixer comprises a mixing section and a mixing tub, mixed materials being fed from the mixing section to the mixing tub, and a portion of the materials in the tub being recirculated to the mixing section. 5. A system as claimed in claim 4, wherein the device comprises a level sensor in the tub. 6. A system as claimed in claim 4, wherein the device comprises a load sensor which measures the weight of the tub. 7. A system as claimed in any of claims 4-6, wherein recirculation of material takes place upstream of the flow meter in the output. 8. A system as claimed in any preceding claim, wherein the supply of solid material comprises separate supplies of cement and dry additives, a flow meter being provided to measure the rate of flow of the dry additives. 9. A system as claimed in claim 8, wherein the supply of dry additives comprises multiple separate supplies of additives, each with its own flow meter. 10. A system as claimed in any preceding claim, wherein the liquid supply includes at least one tank. 11. A system as claimed in claim 10, wherein the device for measuring the amount of liquid supplied comprises a level sensor in the tank or a flow meter which measures the amount of liquid flowing from the tank. 12. A method for mixing a cement slurry, wherein the solid and liquid components are continuously delivered to a mixer and a cement slurry is continuously removed from the mixer for use, the method comprising measuring the flow rate of liquid components into the mixer and measuring the flow rate of the cement slurry removed from the mixer, characterized by measuring the amount of slurry in the mixer, using the measurements of flow rate and amount of slurry to calculate the solid fraction of the fluid; and controlling the delivery of cement and/or liquid components to the mixer according to the calculated solid fraction. 13. A method as claimed in claim 12 wherein the solid components are delivered to the mixer separately from cement, the method further comprising measuring the flow rate of the additives delivered to the mixer. 14. A method as claimed in claim 12 or 13, wherein the mixer includes a tub, the measurement of the amount of cement slurry in the mixer comprising a measurement of the amount of cement slurry in the tub. 15 A method as claimed in claim 14, wherein a portion of the cement slurry in the tub is recirculated into the mixer as solid and liquid components are added. 16. A method as claimed in claim 15, wherein the recirculation takes place upstream of the measurement of the flow rate of cement slurry removed from the mixer. 17. A method as claimed in any of claims 12-16, wherein liquid components are delivered for mixing from a liquid supply including at least one tank, the method further including the steps of measuring the level of liquid in the tank over time and computing displacement volume as: Sigma (V(h1n)-V (h2n)) where: V (h) is the exact volume of the tank at level (h); h1n is the start level of the n<TH> displaced tank volume; h2n is the stop level of the n<TH> displaced tank volume. |
