New technology for waste heat recovery in calcined kilns in the production of titanium dioxide powder

China Paint Online News Information: The kiln is a large energy consumption in the production of titanium dioxide, its energy consumption accounts for about 20% of the total energy consumption of titanium dioxide production, but also the thermal energy utilization rate is not high one of the chemical operating units. In the 1980s, the Ministry of Chemical Industry organized the Ministry of Chemical Industry Paint Research Institute, the third design institute and part of the titanium dioxide powder factory, in Zhenjiang, a 1600-unit kiln (heat source for light diesel, lining 15 cm refrater-resistant brick, partial titanium acid leaf filter dehydration, product for sharp titanium type) in the field for nearly a week of testing, resulting in a ton of product energy consumption of 1423.6 kJ (340×104 kca), of which partial titanium acid moisture evaporation accounted for 30.84 percent of energy consumption, kiln cooling accounted for 39.53 percent, flue gas took away 22.44 percent of the heat (smoke temperature of about 250 degrees C), finished products took away heat accounted for 6.94 percent, the first three accounted for 92.81 percent of total energy consumption. Recently, Shandong Hospital to an annual output of 40,000 tons of the kiln (using natural gas heating, diaphragm pressure filter dehydration, flue gas temperature of about 380 degrees C, the product is still sharp titanium type×) according to the above-mentioned 80's test results, re-conversion The results are as: tons of product energy consumption of 1034.4 kJ, partial titanium acid moisture evaporation accounted for 20.1%, kiln cooling accounted for 24.97 percent, flue gas took away 39.58 percent of the heat, the finished product took away 7.85 percent of the heat. The utilization rate of thermal energy has been significantly improved, but the first three still account for 84.65 percent, while the heat of flue gas and finished products take away more heat than the 80's 1600 small kilns, which is mainly due to the current operation process tail temperature high (380 to 400 degrees C), the output is large.Exhaust gas (smoke) residual heat utilization In recent years, exhaust exhaust residual heat utilization is very common in the industry, the most used is the smoke by high temperature electric dust removal, and then used for waste acid concentration pre-concentration, heat energy utilization rate is better. There are several enterprises through the introduction of foreign technology, flue gas by high temperature electric dust removal, part of the return to the kiln head to do secondary heat wind use, can reduce the consumption of natural gas, the remaining flue gas and then supply waste acid pre-concentration, the above two methods of flue gas residual heat utilization rate can be more than 50%. There are enterprises directly into the flue gas residual heat boiler, producing 0.8 MPa steam for use in the system, but the direct use of flue gas is more difficult to operate, preferably through thermal exchange of thermal oil and then used in the residual heat boiler, the operation is relatively stable. The simplest and least expensive way is to use secondary water washing as cooling water in the high hills of electric de-fog, while reducing the flue gas temperature while the waste water is heated for washing, of course, the heat utilization rate of this method is also relatively low.measures to reduce the cooling of kilns, Ti-Cons of Germany has introduced that in a kiln of 3200×55,000, lined with a layer of 152 mm insulation brick and a layer of 1 The 52 mm refrailable brick reduces heat loss on the surface of the kiln housing by approximately 126×104 kJ (30.1×104 kcal), equivalent to a 25% reduction in heat loss. At present, domestic qualified enterprises have changed the original single-layer refrater-resistant brick design to double-layer brick (one layer of refrater-resistant brick, one layer of insulation brick), according to the size of the kiln body is different, some use 150 mm refrailable brick , 150 mm refraoric brick or 150 mm refraoric brick , 50 mm thermal brick, there is a significant effect of reducing the cooling of the kiln body.In the 1980s, Shanghai, Nanjing and other places of titanium dioxide factory has learned from steel mill steel furnace insulation measures, in the kiln and refractable brick lined with a layer of aluminum silicate fiber insulation felt, its insulation effect is very obvious, people standing under the kiln can hardly feel too much radiation heat, and even touch the shell with their hands, after the insulation felt is too soft, after long-term operation of the kiln fire-resistant brick displacement and abandoned. If the problem of insulation felt and brick fixation can be solved, this method can greatly reduce the thermal loss of kiln body.products take away the heat recovery calcination after the temperature of titanium dioxide as high as 800 degrees, the heat taken away accounted for 7% to 8% of the total energy consumption of calcination, but also can not be underestimated, before the domestic titanium-white enterprises cooling kilns are mostly water-cooled, because the internal design of the cooling cylinder is unreasonable, heat exchange effect is not good, most factory water has not been recycled. After the introduction of Eastern European technology in the 1990s, the cooling kiln almost completely changed to air-cooled, cold air and hot material heat exchange can rise to about 90 degrees C, return to the kiln for a wind use. However, from a thermodynamic point of view, residual heat recovery is not complete, natural gas as an example to do fuel only about 38% of the heat, gas as fuel also only 54%, it is recommended that in the future to air-cooled and water-cooled at the same time, heated cooling water can be washed and used.
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