In the manufacturing process of solid spheres, it is known to feed crushed glass particulate raw materials in a carrier gas stream to a combustion chamber where the glass particulate stream is heated by a flame, thereby causing the crushed glass to become spherical particles. Similarly, for the manufacture of foam spheres, it is known to provide a small spherical raw material to the combustion chamber. In the combustion chamber, due to the action of the flame, these small spheres are heated and transformed into foam glass spheres. Such a raw material is usually made by spray-drying a solution (e.g., a solution mainly composed of sodium silicate solution and also containing a foaming agent (e.g., urea)).
The way the raw material is heated is crucial to the quality and yield of the formed spheres, especially when those spheres are to be made into foam glass spheres. At the same time, the economy of the production process is also important. Rapid heating is beneficial to the formation of spherical particles and/or vitrification of the raw material, which requires good thermal contact between the flame and the raw material. In order to obtain a product of uniform quality, it is important that the spheres produced by this production method should be uniformly processed in the combustion chamber, and it is also important to reduce the tendency of solid materials to bond and/or adhere to the side walls of the combustion chamber, which may be caused by excessive heating during the transformation of the raw material into spheres.
One object of the present invention is to help meet at least some of the above requirements.
In this method, the raw material is subjected to the action of a flame in the combustion chamber, causing the raw material to be heated and formed into the glass spheres, after which the spheres are removed from the combustion chamber. It is characterized in that the raw material supplied to the combustion chamber is dispersed in a carrier gas stream, which is a mixture including fuel gas and oxygen supplied to the flame in the combustion chamber, and inert gas is also supplied to the combustion chamber to maintain a gas stream that flows along and around the flame trajectory to form a gas ring.
Ensuring uniform and good processing of the raw material to increase the yield of high-quality spheres obtained. Due to the method of supplying the raw material and gas to the combustion chamber, each unformed sphere is completely surrounded by a stable flame, causing them to be rapidly heated within the gas ring, which transfers additional kinetic energy to the raw material and spheres to facilitate the collection and transport of the processed spheres out of the combustion chamber, while keeping the spheres in a sufficiently dispersed state to avoid the spheres bonding or adhering to the side walls of the combustion chamber. A more important advantage of the method employed in the present invention is that it has been found that the side walls of the combustion chamber are cooler than in other cases during the effective sphere-making process, which is beneficial for improving the economy of thermal processing and helps to extend the effective working life of the combustion chamber.
In a preferred embodiment of the present invention, the gas ring is formed by air supplied to the combustion chamber, which is advantageous for improving economy and convenience, and provides a favorable stabilizing factor due to the presence of nitrogen. The gas ring provides a highly efficient screen to prevent glass or vitrifiable materials from colliding with the side walls of the combustion chamber. Similarly, the additional oxygen in the air provided promotes complete combustion of the fuel gas, further improving fuel economy. For similar reasons, it is preferable that the supplementary oxygen in the inert gas ensures that the oxygen in the combustion chamber exceeds the amount required to maintain complete combustion of the fuel.