X-ray or gamma ray systems or devices – Specific application – Diffraction – reflection – or scattering analysis
Reexamination Certificate
2001-12-19
2004-05-11
Church, Craig E. (Department: 2882)
X-ray or gamma ray systems or devices
Specific application
Diffraction, reflection, or scattering analysis
C378S071000
Reexamination Certificate
active
06735278
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method and apparatus for continuously presenting a sample from a stream of particulate material which contains crystalline substances and effectively continuously analysing the sample by X-ray diffraction (XRD). More particularly, the present invention relates to phase composition analysis of cement and cement clinker and will be described in relation to this application, however it is to be understood the invention is applicable for analysing other materials which include crystalline substances, such as for example from mineral processing streams.
BACKGROUND OF THE INVENTION
In the manufacture of cement, feedstock materials such as limestone, shale, sand and iron oxide are blended, milled and then fired in a kiln from which cement clinker is derived. The cement clinker with some additives, is then milled to produce cement. The milling, which is the final stage in manufacturing cement, is usually carried out in a ball mill, ie a rotary mill which contains a charge of steel balls. As the mill rotates the input materials (mainly cement clinker and small amounts of additives such as gypsum, limestone and sometimes fly ash) are ground and mixed to a fine state or powder.
X-ray diffraction measurements may be made on the cement clinker from the kiln, the clinker being suitably cooled and crushed to a fine powder for the measurements. Such measurements can provide information on the ratios between the different clinker phases and on the percentage of free lime. The strength of a final cement product is significantly determined by these phase ratios, and the amount of free lime is an indicator of the degree of burning in the kiln. Furthermore, the mineralogical composition can provide information regarding temperature profiles in the kiln, and indicate deviations from the optimum. Thus such X-ray diffraction measurements, if available on line, would provide information which can be used to control the kiln operation, burner adjustment and hence product quality.
X-ray diffraction measurements may also be made on the cement powder from the cement finish mill. These can provide information on the ratios of gypsum and other additives in the cement, information about crystal phases in the cement clinker, information on free lime and portlandite (prehydration) and on the degree of dehydration of the gypsum. Such ratios also affect the strength of the final cement product and the degree of gypsum dehydration affects the cement setting time. Thus, if these measurements were available on-line, information would be provided which can be used to control the milling and thus the quality of the final cement product. By way of example, the hydration states of gypsum in conjunction with the free lime and calcium aluminate content and form can be used to predict setting times. Furthermore, the finish mill operating temperature can be used to adjust the gypsum dehydration and hence control setting times. By way of further example, the mineralogical composition can be used to predict the strength development of cement product. The composition and fineness of the cement can then be adjusted to provide a target cement strength.
Heretofore to the applicant's knowledge, X-ray diffraction measurements of ex-kiln cement clinker and ex-mill cement powder have generally been laboratory based. For such measurements, a sample of the process stream, which may be taken automatically or by hand, is delivered to the laboratory where individual sample pellets, of the order of only a few grams, are prepared and presented to the XRD machine, either by hand or using robotics. The time taken for such sample preparation and measurement limits the usefulness of the information for process control. Furthermore, the extra grinding required to reduce the particle size to enable static samples to be analysed by the X-ray analysis may cause changes in the dehydration states for milled cement.
SUMMARY OF THE INVENTION
According to a first aspect, the present invention provides a method for analysing a stream of particulate material containing crystalline substances including
(i) extracting a sample flow from the stream of particulate material,
(ii) preparing the sample flow for X-ray diffraction measurements and conveying the so prepared sample flow through a measurement station,
(iii) directing an X-ray beam onto the sample flow as it passes through the measurement station and detecting diffracted X-rays over an angular range to provide a diffraction pattern,
(iv) analysing the diffraction pattern to determine a composition for crystalline substances in the sample,
(v) repeating step (iii) to provide diffraction patterns from the continuously moving sample at predetermined intervals, and
(vi) repeating step (iv) for each diffraction pattern from step (v),
whereby a series of sequential composition determinations from the sample flow are provided which represent the composition of crystalline substances in the stream of particulate material.
It will be appreciated that the above described method can provide a wide angular range diffraction pattern at short intervals from a continuously moving sample. The series of sequential composition determinations from such patterns represents the composition of the stream of particulate material substantially in real time. The series of composition determinations also gives effectively a “continuous” analysis of the stream of particulate material (the term “continuous” in this context meaning continuing discrete compositional determinations separated by short time intervals).
Preferably the diffracted X-rays of step (iii) are simultaneously detected over the angular range.
Preferably the diffraction patterns are analysed using a whole pattern analysis method, for example the Rietveld method.
Preferably step (ii) includes feeding the sample onto a continuously moving carrier and smoothing and flattening its surface and more preferably the sample is formed into a bed on the moving carrier. Preferably the carrier includes an endless groove for receiving the sample and into which the sample is preferably packed to form the bed. The preparation of the sample flow is to ensure that the sample surface is presented to the measurement station at a constant height. Following step (iii) the sample is continuously removed from the carrier prior to feeding further sample onto the carrier.
Using this invention, extra grinding of an ex-mill cement sample is not required because the moving sample presented to an X-ray diffraction machine ensures that even with larger particle sizes, a suitable number of particles can be expected to be oriented in such ways as to fulfil the Bragg condition for diffraction from every possible interplanar spacing. This improves the quality of the XRD data by improving the particle statistics. Preferably the sample is fed onto a carrier having an endless groove at a rate such that the groove is overfilled, in which case excess sample is removed from the carrier and the sample in the groove suitably presented for packing thereinto.
According to a second aspect the invention provides a method for continuously presenting a sample from a stream of particulate material containing crystalline substances for obtaining X-ray diffraction analyses of the particulate material, including
(i) extracting a sample flow from the stream of particulate material,
(ii) feeding the sample flow onto a continuously moving carrier and smoothing and flattening its surface,
(iii) continuously moving the carrier to move the sample through a station for performing X-ray diffraction measurements on said flat and smooth sample surface, and
(iv) continuously removing the sample from the carrier prior to feeding further sample flow onto the carrier.
According to a third aspect, the invention provides apparatus for analysing a stream of particulate material containing crystalline substances, including
means for extracting a sample flow from the stream of particulate material,
means for preparing the sample flow for X-ray diffraction measurements
Madsen Ian Charles
Manias Constantine George
Retallack David James
Scarlett Nicola Vivienne Yorke
Schneider Karl Edmund
Church Craig E.
FCT - Actech PTY LTD
Lerner David Littenberg Krumholz & Mentlik LLP
Yun Jurie
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