Application of Needle Blanket in Petrochemical Industry

1 Foreword As a leader in modern industry, the petrochemical industry is full of thermal equipment. In the country, more and more attention is paid to energy conservation, work, background, lower, thermal equipment, energy conservation, more and more become one of the important links of energy conservation and work in petrochemical enterprises. In order to make the operation of thermal equipment safe and reduce heat loss, achieve the purpose of saving energy and reducing product costs, it is necessary to keep thermal equipment warm according to different requirements and specifications. Therefore, through long-term research and exploration, Hebei Duofu Technology Co., Ltd. has developed a new type of thermal insulation and energy-saving material – ceramic fiber-coated aluminum foil blanket (referred to as aluminum foil blanket), and has been put into large-scale production.

The material is a combination product that uses special equipment and special adhesives to form a ceramic fiber blanket and metal aluminum foil into a single structure. It has the characteristics of weight, light weight, good thermal insulation effect, high compactness, corrosion resistance, good thermal shock resistance, vertical and horizontal, tensile resistance, strength, large, convenient construction and maintenance, etc. It is especially suitable for thermal insulation and energy saving effect requirements, demanding, high temperature, thermal engineering, equipment, and heating pipes. Main specifications: width 300mm, 610mm, 1220mm, length, 3600mm, 7200mm, fiber blanket, thickness, 20mm, 30mm, 50mm, aluminum foil thickness, 0.047mm, 0.2mm, the specific size can also be customized according to user requirements.

2 Insulation mechanism of aluminum foil-clad needle-punched blanket products

In general, thermal equipment heat dissipation methods mainly include conduction, convection, and radiation, while aluminum foil blankets, with their unique structure, weaken the three heat dissipation pathways and reduce heat loss.

2.1 Weakening of conduction and heat dissipation

Heat source Heat first passes through the fiber blanket, conducts heat dissipation, and can only proceed in the direction of the fiber rod, while the fibers of the ceramic fiber blanket are intertwined

In addition, the porosity of ceramic fiber blankets is 93%, and the porosity of fibers is 80%. Point contact, point contact and high porosity further weaken the conduction of heat and increase the thermal resistance of conduction and heat dissipation.

2.2 Weakening of convective heat dissipation

Ceramic fiber blankets have a high porosity, and the gas is divided into many small pores that are almost stationary, while the pressure in the dispersed pores is constant. Together with the solid fibers, the air pressure will form a dense solid shield (forming a shielded air pressure), which hinders the intrusion of hot air flow and weakens heat dissipation. At the same time, due to the compactness and directness of aluminum foil, it hinders the convection of gas.

2.3 Weakening of radiation and heat dissipation

Ceramic fiber itself is white, smooth, reflective, body, plus aluminum foil with specular reflection ability, which can effectively reduce heat radiation.

Application of Ceramic Fiber Aluminum Foil Clad Needle Blanket

3 ● 1 Heating furnace lining, insulation layer When the heating furnace lining is made of ceramic fiber lining, composite structure, aluminum foil blanket is usually used for insulation in the insulation layer to improve the fiber lining, anti-corrosion, energy saving and consumption reduction, etc., comprehensive performance, in, use, to note the following aspects of the definition conditions:

① Except for the forced flue gas flow, the smoke pipe, air duct and furnace bottom, all other areas of the heating furnace can use fiber lining.

② The operating temperature of any layer of fiber lining must be higher than this, and the calculated temperature of the layer heating surface must be above 260 ° C. ③ When the fuel, the sulfur content exceeds 10 μg/g, the furnace lining is used, the fiber dimension, the condensation, the furnace, the wall steel plate, the hot surface, should be painted, a layer, anti-corrosion, coating, the coating is suitable for 177 ℃ environment; when the fuel, the sulfur content exceeds 500 μg/g, should be set, gas barrier aluminum foil or stainless steel foil, gas barrier layer should be located in the operating conditions, at least, higher than the calculation, the dew point is above 56 ℃, the part, at the barrier, gas layer, edge, should be lapped , The edge of the lining and the piercing part should be sealed to prevent corrosive gases from passing through the lining to dew, corrode steel plates and anchors.

④ When the content of fuel, medium and heavy metal, exceeds 100μg/g, all heating furnace linings shall not be made of soft fiber materials, but shall be made of fiber amorphous materials (prefabricated blocks) or other heavy insulation materials.

⑤ When the pressure on the lining is greater than 0.8MPa, no fiber lining shall be used. (6) The convection section equipped with soot blowers, steam, spray guns, and washing equipment shall not use fiber lining.

3.2 External insulation of steam pipelines

3.2.1 Insulation structure

Insulation structure: first layer, ceramic porcelain, fiber dimension, blanket, second layer, covered with aluminum foil needle punched blanket (aluminum foil facing the steel pipe), third layer of aluminum foil blanket (aluminum foil facing inward), and then according to the design, add up in turn, each layer with flat steel, with bundling, its bundling, spacing, not more than 300mm, finally, with 0.5mm thick, black iron cover, brush, anti-rust paint.

3.2.2 Thermal insulation entity simulation

In order to accurately judge, maintain temperature, structure, whether or not, rationally, a solid simulation device for pipeline insulation was established. The simulated pipeline for transporting steam is a stainless steel pipe with a length of 1200mm, an outer diameter of 108mm, and a wall thickness of 4mm. Inside the stainless steel pipe, an aluminum oxide, ceramic pipe, and ceramic pipe with an outer diameter of 45mm are evenly wound on the outside. Electrical resistance wire, the maximum heating power is 3KW. In the middle of the steel pipe, the outer surface is wrapped with aluminum foil, and the measuring end of a thermocouple is wrapped close to it. The thermocouple is connected to an artificial intelligence industrial regulator to control the temperature of the outer surface of the steel pipe. In addition, four 0.5mm thermocouples are installed in the middle and ± 100mm from the center of the stainless steel pipe to understand the temperature distribution of the pipe wall. The heat dissipation of the simulated pipeline is measured by a WY-2 heat flow meter buried under the surface insulation fiber, and the temperature of each point on the surface is measured by a surface thermometer, and then calculated according to the provisions of GB 50264-1997.

To ensure that the heat conduction in the measurement area is one-dimensional heat conduction in the direction of the pipe diameter is the key to the successful simulation of the heat transfer pipeline of this device. To this end, the stainless steel tube is placed on a lightweight refractory brick with a very low thermal conductivity, and the ends of the steel tube are insulated with a 300mm thick fiber blanket. Under the condition that the surface temperature is 430 ° C and the thickness of the fiber blanket (density 128Kg/m3) is 108mm, the maximum temperature difference of the simulated tube in the range of ± 100mm in the center is 10 ° C. The radial temperature layer is 35 times that of the axial temperature layer, which shows that the model of one-dimensional radial heat transfer is established. In fact, in order to improve the experimental accuracy, the value range of all experiments is further reduced to the range of ± 25mm. In the experiment, when the heat flow value measured by the heat flow meter is stable, the results are shown in Table 1.

表 1    实体模拟 实验 结 果

Note: ① Composite structure: 72mm fiber blanket + 0.4mm aluminum foil + 62mm fiber blanket; ② Composite structure: 72mm fiber blanket + 0.4mm aluminum foil + 36mm fiber blanket.

As can be seen from Table 1, the results of the computer simulation are very close to the experimental results, indicating that the computer simulation and the thermophysical performance test results of the square method and thermal insulation materials are accurate, and these methods and data can be used for further research. From this, it can also be seen that the surface temperature of the insulation layer, the addition of aluminum foil, and the other, the condensation, unchanged (fiber blanket, thickness, 134mm, 108mm), respectively, decreased by 1.75 ° C and 0.5 ° C, which can reduce the heat loss by about 5%, and also make the surface temperature more uniform. This is mainly due to the addition of aluminum foil to the insulation layer, which hinders the insulation layer. Under the action of buoyancy, the medium-hot gas flows to the top, thus causing the temperature of the upper part of the insulation layer to decrease. The uniformity of the temperature is improved and the heat dissipation is reduced.

Adding an aluminum foil layer to the insulation layer can prevent hot gas from spreading upward in the insulation, thus making the surface temperature of the insulation structure uniform, and reducing heat dissipation by about 5%. Its contribution is roughly equivalent to adding another 10mm insulation layer to the 150mm thick insulation layer. Therefore, the insulation material can save about 4.5 yuan/m2 in cost, and also effectively reduce the volume of the pipeline.

4 Engineering application examples

From the perspective of “replacing oil with coal” to bring huge economic benefits, the petrochemical company has built a new, 480mm medium-pressure steam pipeline from the thermal power plant to the refinery. The steam temperature output from the thermal power plant is 435 ° C, and the required steam temperature to the handover point is 400 ° C, the flow rate is 100t/h, and the pressure is 3.6Mpa. Due to the requirements of the refinery, the temperature is very high. According to past experience, the use of ceramic fiber blanket products for temperature insulation is not enough to meet the requirements. After research and analysis, it was finally decided to use a new type of thermal insulation structure with aluminum foil needle punched blanket.

The pipeline was installed in October 2000 and put into use as scheduled. The actual effect was very satisfactory, fully meeting the design requirements and meeting the production needs. In December 2003 and November 2006, tests were carried out respectively. The test results are shown in Table 2.

Table 2 Qilu Petrochemical Application Test Results

A petrochemical newly built from a thermal power plant to Celanese Industrial Park, a 500mm medium-pressure steam pipeline, the steam output from the thermal power plant, the temperature is 430 ° C, the pressure is 4.3Mpa; the other end of the pipeline, the outlet temperature is 390 ° C, the pressure is 3.9Mpa, the pipeline length is 6000m, and the steam flow is 80~ 160t. Since it was officially put into use on November 8, 2006, the operation effect has been very good. On March 12, 2007, the test was conducted, and the test results are shown in Table 3.

Table 3 Test results of a petrochemical application

5 Conclusion

The application of the new thermal insulation structure of ceramic fiber aluminized foil needled blanket not only has remarkable effects in energy saving, consumption reduction, cost reduction and production increase, but also optimizes the equipment process to a certain extent and improves the overall equipment structure, bringing inestimable tangible and intangible benefits to manufacturers. After the medium-pressure steam pipeline from a certain thermal power plant to an oil refinery adopts this structure, the medium-pressure steam pipelines from a certain thermal power plant to a certain ethylene plant, the medium-pressure steam pipeline of a certain petrochemical ethylene plant, the medium-pressure steam pipeline of a certain company’s ethylene plant, and the medium-pressure steam pipeline in the southern chemical industry park and other projects have successively adopted the thermal insulation structure of ceramic fiber aluminized foil needled blanket products and achieved good application effects.