One aspect relates to a process for the preparation of a quartz glass body, including providing a silicon dioxide granulate, wherein the silicon dioxide granulate was made from pyrogenic silicon dioxide powder and the silicon dioxide granulate has a BET surface area in a range from 20 to 40 m.sup.2/g, making a glass melt out of silicon dioxide granulate in an oven and making a quartz glass body out of at least part of the glass melt. The oven has at least a first and a further chamber connected to one another via a passage. The temperature in the first chamber is lower than the temperature in the further chambers. On aspect relates to a quartz glass body which is obtainable by this process. One aspect relates to a light guide, an illuminant and a formed body, which are each obtainable by further processing of the quartz glass body.

Methods and systems for treating mined sand to remove an impurity in accordance with the disclosure. An example method mined sand provides mined sand containing the impurity, contacting the mined sand with an aqueous treatment fluid comprising an ethoxylated alcohol and a sulfonic acid derivative, and drying the mined sand; wherein at least a portion of the impurity is removed from the dried mined sand after contact of the mined sand with the aqueous treatment fluid.

One aspect relates to a process for the preparation of a quartz glass body. The process includes providing silicon dioxide particles, making a glass melt out of the silicon dioxide particles in an oven and making a quartz glass body out of at least part of the glass melt. The oven has a gas outlet through which gas is removed from the oven, wherein the dew point of the gas on exiting the oven through the gas outlet is less than 0° C. One aspect further relates to a quartz glass body which is obtainable by this process. One aspect further relates to a light guide, an illuminant and a formed body, which are each obtainable by further processing of the quartz glass body.

Methods and systems for treating mined sand to remove an impurity in accordance with the disclosure. An example method mined sand provides mined sand containing the impurity, contacting the mined sand with an aqueous treatment fluid comprising an ethoxylated alcohol and a sulfonic acid derivative, and drying the mined sand; wherein at least a portion of the impurity is removed from the dried mined sand after contact of the mined sand with the aqueous treatment fluid.

A method for preparing quartz glass with low content of hydroxyl and high purity, includes providing silica powders including hydroxyl groups. The silica powders are dehydroxylated, which includes drying the silica powders at a first temperature, heating the silica powders up to a second temperature and introducing a first oxidizing gas including halogen gas, thereby obtaining first dehydroxylated powders, and heating the first dehydroxylated powders up to a third temperature and introducing a second oxidizing gas including oxygen or ozone, thereby obtaining second dehydroxylated powders. The second dehydroxylated powders are heated up to a fourth temperature to obtain a vitrified body. The vitrified body is cooled to obtain the quartz glass with low content of hydroxyl and high purity. The quartz glass prepared by the above method has low content of hydroxyl and high purity. A quartz glass with low content of hydroxyl and high purity is also provided.

In a known method for treating pourable, inorganic grain, a heated rotary tube is used that rotates about an axis of rotation and surrounds a treatment chamber that is divided into a plurality of treatment zones by means of separating elements. The grain is supplied to the treatment chamber at a grain inlet side and is transported, in a grain transport direction, to a grain outlet side and is exposed to a treatment gas in the process. In order, proceeding herefrom, to allow for reliable and reproducible thermal treatment of pourable inorganic grain, in particular SiO.sub.2 grain in the rotary kiln, in a manner having low and effective consumption of treatment gas, it is proposed for spent treatment gas to be suctioned out of a reaction zone of the treatment chamber, by a gas manifold that rotates about the longitudinal axis thereof.

An apparatus for the wet attrition of particulate material comprising an attrition scrubber; a dewatering screen comprising a deck and a sump beneath the deck, the dewatering screen being mounted upstream of the attrition scrubber whereby oversize material from a downstream end of the deck of the dewatering screen passes into the attrition scrubber; and a hydrocyclone wherein an underflow, containing a coarser fraction of the feed slurry, passes out of a lower outlet of the hydrocylone while an overflow, containing a finer fraction of the feed slurry and most of the water, passes out of an outlet at the upper end of the hydrocyclone, a pump being provided for pumping material from the sump of the dewatering screen to the inlet of the hydrocyclone, wherein the underflow from the hydrocyclone is passed into the attrition scrubber.

A method of separating heavy mineral particles, such as zircon, monazites, xenotime etc., from a sample of quartz crystal powder, comprises the steps of: a. conditioning the quartz powder suspected of containing heavy mineral particles as an aqueous pulp using a froth-flotation agent; b. subjecting the conditioned pulp to froth flotation to obtain a tailing; c. combining the tailing with an aqueous solution having a density greater than that of quartz and less than that of a heavy mineral which it is desired to separate; and d. centrifuging the combination. The separated heavy mineral crystals can then be characterized using a micro-analysis technique.

One aspect relates to a process for the preparation of a quartz glass body. The process includes providing a silicon dioxide granulate from a pyrogenically produced silicon dioxide powder, making a glass melt out of silicon dioxide granulate, and making a quartz glass body out of at least part of the glass melt. The size of the quartz glass body is reduced to obtain a quartz glass grain. The quartz glass body is processed to make a preform and an opaque quartz glass body is made from the preform. One aspect further relates to an opaque quartz glass body which is obtainable by this process. One aspect further relates to a reactor and an arrangement, which are each obtainable by further processing of the opaque quartz glass body.

One aspect relates to a process for the preparation of a quartz glass body. The process includes providing a silicon dioxide granulate I prepared from a pyrogenically produced silicon dioxide powder, treating the silicon dioxide granulate I with a reactant at a temperature in a range from 1000 to 1300° C., and making a glass melt out of the silicon dioxide granulate. A quartz glass body is made out of at least a part of the glass melt. Furthermore, one aspect relates to a quartz glass body obtainable by this process. Furthermore, one aspect relates to a light guide, an illuminant, and a formed body, each of which is obtainable by further processing of the quartz glass body. One aspect additionally relates to a process for the preparation of a silicon dioxide granulate II.