The term blending vessel comes up quite often on websites selling laboratory and industrial use materials and equipment. These vessels are basically tanks that are required where large scale manufacture of processed fluids – resins and curatives – such as urethanes, silicones, etc., is to be conducted. The principle of this technique is quite simple and similar to the way ink was blended back in the day. It involved pouring in measured quantities of ingredient liquids into a large tank that was designed to contain mixing facilities. The liquids were then mixed mechanically, and the product was tested again and again till the prescribed consistency of the resultant was achieved. Naturally, this required several iterations of the same process, and was thereby quite a time and energy consuming task – the larger the volume of ink required the more tedious it would be.
The method of in-tank blending just referred to was conducted in any one of two ways. Either the ingredient liquids were agitated in a tank by using moving paddles mounted on the side or bottom surface of the same tank, or were circulated through the space by means of a dispersing tube. The first technique was known as in-tank mixing, and was more suited for large volumes of liquid. The second, known as sparge mixing, was opted for when smaller amounts of liquids were required. In both cases, the attainment of the desired degree of homogenization of the composite liquid generally took time, and involved intensive and repeated testing. Also, the processes were a little subjective, as the nature of the final product would rely heavily on the initial ‘recipe’, meaning on the input proportions of the ingredient liquids. Besides, due to their dependence on test results, the liquids produced were again different in composition each time they were synthesized.
Today the technology for blending liquids has improved immensely, and this is reflected in the range of equipment available for the process. Sizes of blending vessels today cover a wide range from a gallon to about a hundred gallons. They are designed to withstand very high rates of liquid change, usually as high as 160 gallons per minute. Some of the smaller vessels cannot tolerate such high speeds though, and are accordingly calibrated for liquid change at upto 20 gallons per minute. Otherwise the shape, configuration, material, degree of insulation and automation, are all quite customizable in the blending vessels that are commercially available today.