Application of the most popular deodorization and

2022-08-11
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Application of deodorization and smoke removal catalyst technology in household electrical appliances

1 introduction

in Japan, there are two kinds of household electrical appliances that have been welcomed by families. One is garbage disposal, the other is fish barbecue. They have always had a stable sales market. However, many studies have shown that the odor of the living environment is directly related to the mechanism of garbage disposal to help them carry out recycling education in all parts of the United States. The lampblack and odor generated when using the fish barbecue not only affect the quality of fish barbecue, but also damage the interior decoration and air quality. In this regard, we must first determine the composition of odor and lampblack, and then reduce the content of harmful substances in the vehicle exhaust according to the principle of reducing the concentration of harmful substances, so as to achieve the purpose of curbing odor and eliminating lampblack

2 deodorization technology of waste processors

2.1 waste processors

in Japan, with the improvement of environmental protection awareness, local governments pay more attention to waste treatment. In 2002, Japan's investment in waste processors has reached 140-170 billion yen. Garbage disposal machines mainly include household and enterprise use. As an ordinary household product, garbage disposal machines mainly include microbial decomposition and drying. The so-called drying type is to stir the garbage and blow it at a temperature of 130 ℃ at the same time, so as to dry the garbage and reduce its volume. The machine can handle 0.7 kg of garbage in 1.75 hours. The volume of the treated garbage is only one seventh of the original volume, and can be used as fertilizer. Figure 1 is a cross-sectional view of the tensile machine specialized in waste treatment Jinan assaying. (see Figure 1)

2.2 odor generated in the dry garbage processor

in order to eliminate odor, it is necessary to understand the odor components generated in the garbage processor. We put a certain amount of standard waste consisting of vegetables, fruits, fish, tea, etc. into the dry waste processor for operation, and analyze the waste produced in the initial and later stages. Put 0.7kg garbage into the garbage processor for 1.75 hours. Then, the stability and reliability of the system are greatly improved by using activated carbon to collect the odor generated at the initial and late stages of treatment, and then extract the odor components with carbon disulfide. Then, the extract is put into the chromatographic separation - mass analyzer (GC-MS) for analysis by using gas chromatography (GC). The results showed that the initial components were ethanol, pyruvic acid and 2,3-dimethylpentane. The late components detected were methyl sulfide, methyl disulfide, pinene, etc., while water, carbon dioxide, limonene, acetone and other compounds always existed. It can be seen that compared with the odor of garbage, the odor emitted from the processor is more composed of high molecular weight components. This is because the garbage produces new components at 130 ℃. The olfactory threshold of methyl sulfide and methyl disulfide is very low, which is the key to eliminate odor

2.3 about the technology of eliminating the odor produced by the waste processor

deodorization technology includes direct combustion method, ozone oxidation method, adsorption method, liquid medicine cleaning method, absorption method, biological deodorization method, plasma deodorization method, catalyst oxidation method, etc. As the water content of the gas (hereinafter referred to as treatment gas) produced by the dry waste processor is more than 90% of the steam, the temperature will be 100 ℃. Therefore, ozone oxidation method, adsorption method, liquid medicine cleaning method and plasma method are not suitable for deodorization on dry garbage disposal machines. The cost of direct combustion method is very high, so considering the cost and safety, catalytic oxidation method is more suitable for odor treatment

2.3.1 research and development objectives of contact media

for the contact media of dry waste processor, there are the following requirements:

① good deodorization performance and strong durability. Among them, the deodorization performance is evaluated by the conversion of methyl sulfide. Based on this evaluation benchmark, the target of conversion rate should be above 99.5%

② it can be used in steam environment. Soot and other materials should not block the small holes of the contact media. The service temperature should be between 200~800 ℃, and the durability time should be more than 20000 hours

③ in order to shorten the garbage treatment time, the surface temperature of the contact media should have good rising characteristics

④ the cost is relatively low

2.3.2 basic composition of touch media

in accordance with the above requirements for touch media, the development of touch media is carried out. The contact medium is composed of catalyst and carrier, and the carrier is composed of basic materials and underwear layer. The surface of the underwear layer is attached with catalyst to form the contact medium

The relevant standards are expected to be published at the end of this month for comments.

since the use temperature is 200~800 ℃, manganese dioxide series and ceramic series that can only be used at 500 ℃ cannot be used here, and the catalyst that can be used at this temperature can only be a mixture of platinum and palladium. In order to prevent slagging, it is beneficial to expand the surface area. The catalyst should be attached to the underwear layer in the form of mixing with y-alumina. The basic materials of the carrier can be sintered ceramics, multilayer ceramic fibers, honeycomb metal, porous metal and various foaming objects. Considering the corrosive effect of the treated gas, processing performance and the rapid heating characteristics of the contact medium, the material is required to have good thermal conductivity and low thermal capacity, so the basic material is stainless steel plate with high temperature corrosion resistance

2.3.3 research on the shape of the contact media

after the basic composition of the contact media is decided, it is necessary to study the best shape of the catalyst. Because the shape of the contact medium has a great influence on the surface temperature rise, hole blockage and pressure loss of the contact medium. In addition, the continuous and repeated processes such as the post decomposition of exhaust gas and catalyst, and then uniform diffusion are highly related to the shape of the contact medium

① experimental method

four kinds of platinum palladium catalyst carriers were compared, including corrugated and complex catalyst carriers with the same number of particles, expansion tube catalyst carriers made of stainless steel plate, spiral catalyst carriers, etc. The volume of contact media is 94cm3. The experimental gas is 500ppm ammonia sulfide air without water vapor. The air flow is 8l/min, and the space velocity (SV: air flow/catalyst volume) is 5100h-1. The contact medium is indirectly heated by a heater

the temperature of the heater and the conversion rate of ammonia sulfide with the change of the input power of the heater are discussed below

② experimental results

a. conversion rate

the relationship between the heater temperature of various contact media and the conversion rate of ammonia sulfide is shown in Figure 2. When the conversion rate of ammonia sulfide is above 99.5%, the heater temperature is spiral, corrugated, lattice and expansion tube in the order of gradually increasing. The difference between the spiral contact medium and the expanded tubular contact medium is 35 ℃, which is due to the better heat conduction performance of the former than the latter. (see Figure 2)

from the relationship between the temperature of the heater and the surface temperature of the catalyst, in order to achieve a conversion rate of more than 99.5%, the surface temperature farthest from the heater in the spiral contact medium should also be more than 250 ℃, with an average temperature of more than 300 ℃. At this time, the surface temperature of the heater is 350 ℃. In the same conversion process, in order to obtain the same conversion rate, the surface temperature farthest from the heater is also 250 ℃, and the average temperature is above 300 ℃, so the surface temperature of the heater is 700 ℃. In addition, in the case of the same space velocity and the same surface area of the contact media carrier, regardless of the shape of the contact media, in order to obtain the same conversion, the surface temperature of the catalyst is the same

b. heating characteristics of contact media

the heat conduction of the heater to the surrounding direction. In the case of indirect heating of the contact media, the spiral contact media is the most effective. As an important factor of contact media, that is, the temperature rise characteristics of contact media, the temperature rise of spiral catalyst is the fastest, followed by the expansion tube. The surface temperature of the spiral contact medium can reach 350 ℃ within 5 minutes. Although the specific heat capacity of the expanded tube is the smallest, less than 6.7 (j/k), its thermal conductivity is bound to be poor. Although the specific heat capacity of corrugated and lattice contact media is 47 (j/k), the thermal conductivity is also poor. The specific heat capacity of the spiral contact medium is 17 (j/k), and its thermal conductivity is better than that of the expanded tubular contact medium, so the temperature rise of the contact medium is faster

c. determination of the shape of the contact medium

in order to ensure the deodorization performance, from the perspective of energy saving, the spiral contact medium should be studied emphatically according to the temperature rise characteristics

2.3.4 effect of oxidation concentration and water vapor concentration on deodorization performance

now we will study the effect of oxidation concentration and water vapor concentration on the odor components decomposed from the exhaust gas

2.3.4.1 effect of oxidation concentration

① experimental method

in order to find the condition of the worst oxidation concentration, we make the following assumptions: take the lowest treatment air volume as 0.6l/min, the maximum water vapor generation as 6g/min, and the oxidation concentration as 1.0%. Then dilute the air with nitrogen, adjust the oxidation concentration to 1.0%, add 500ppm methyl sulfide, and use such gas to calculate the conversion of methyl sulfide. The treated air flow is 6l/min. The contact medium is spiral, and the space speed is 5000h-1

② experimental results

see Figure 3 for the relationship between heater power, oxidation concentration and sulfuration methyl conversion. When the conversion is 99.5%, the power is 20W, with 25% remaining from the effect of oxidation concentration on the conversion. (see Figure 3)

2.3.4.2 effect of water vapor concentration

① experimental method

take the treated air volume as 0.6l/min, add water vapor 6g/min or 3g/min, and then add 150cm3/min (2% concentration) of methyl sulfide, and use such air as the test gas. Then when the steam is 6g/min, the concentration of methyl sulfide is 340ppm, and when the steam is 3g/min, it is 630ppm. The contact medium is spiral. When the water vapor is 3g/min, the space velocity is 5000h-1

② experimental results

experimental results are shown in Figure 3. If the conversion of methyl sulfide is more than 99.5%, the remaining power is 140W when the maximum water vapor volume is added by 6g/min. When the average amount of steam is 3g/min, the remaining power is 40W. It can be seen from the above that the influence of water vapor is much greater than that of oxidation concentration. This is because the temperature of the contact medium decreases due to the heat absorption of water vapor, and the catalyst is damaged by water vapor. (see Figure 3)

2.3.5 evaluate the deodorization performance of the catalyst according to its function

put the contact media into the actual dry waste processor, take the conversion rate of sulfuration methyl as the evaluation benchmark, and see the degree of odor reduction through experiments, so as to confirm its deodorization performance

① experimental method

put the spiral contact medium into the dry garbage disposal machine as shown in Figure 1, and the treatment gas flow is 7l/min. Compare the two situations of energizing the catalyst heater (heater temperature: 550 ℃) and not energizing it. 0.7kg standard waste is used, and the odor intensity and unhappiness degree are used for the functional evaluation project, and the average value is used for the evaluation. The function evaluation is carried out at the exhaust outlet

② experimental results

when not powered on, the odor is strong, and its intensity is 4. However, when the touch media works, the odor is significantly weakened and the intensity is reduced to 2. In addition, it is extremely unpleasant when it is not powered on, but once it is powered on, it feels much better. The evaluation based on function shows that the deodorization performance of the catalyst is good. According to the evaluation standard of machine analysis, it is appropriate to use methyl sulfide as the test gas

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