1 Harm of frozen garbage

1.1 Energy consumption of melting frozen garbage

Taking garbage from a city in Heilongjiang Province as an example, at normal temperature, the moisture content of domestic garbage is 50 %, the calorific value is 5179kJ/kg; if the garbage reaches the normal temperature of 15℃ from the frozen state, it is calculated that more heat energy will be consumed; at this time, the calorific value drops to 0. Melting the ice can reduce the calorific value of the garbage by more than 4%.

1.2 Ice solidifies moisture and is difficult to seep out

Bring it to the furnace to increase heat consumption. At room temperature, after the garbage is left in the garbage bin for 5 to 7 days, the external moisture will seep out and The internal moisture is also precipitated after the biochemical reaction, and 10% to 30% of the moisture in the garbage is separated. This part is called leachate, so the heat value of the garbage can be increased, making it easier for the garbage to catch fire. This is why the grate furnace can adapt An important reason for the excessive moisture content of garbage in our country. As for frozen garbage, the moisture of the garbage is solidified inside and outside the garbage. Its melting requires heat and time. However, the heating and thawing conditions of general garbage storage facilities are very poor, which often causes frozen garbage to be directly put into the furnace, and 10% to 30% of the amount entering the furnace is Water ice not only requires heat to melt, but also needs heat to vaporize. Taking 20% ??of the general leachate output, vaporization consumes heat energy. The vaporization of this part of the leachate will again reduce the calorific value of the garbage by 10%; 2 types of energy consumption The total is reached. At this time, the calorific value of the garbage drops to, and its calorific value drops by 14%.

1.3 Influence on the combustion state in the furnace

The thermal ignition rate of the slag increases. After the frozen garbage enters the grate through the pushing device, more moisture is brought in because the garbage needs to be thawed. , the drying process of garbage not only consumes more energy, but also requires longer drying time. Under the same mechanical load of the grate, the length of the grate drying section is increased, causing the burning point of the grate to move backward; at the same time , shortening the length of the combustion section and the burnout section, reducing the normal combustion and burnout time of the garbage, causing the garbage to be burned incompletely, and increasing the thermal ignition rate of the slag. When a large amount of frozen garbage is pushed into the grate, the burning flame on the grate layer can be extinguished, which not only brings huge risks to the normal operation of the incinerator, but also brings about a series of flue gas pollution problems. .

2 Analysis of the causes and factors of the freezing of garbage into clumps

2.1 The reasons for the freezing of garbage into clumps

Waste moisture can be divided into internal moisture and external moisture 2 form. The internal moisture is distributed among the molecules of the garbage material. It is determined by the nature of the garbage itself and has nothing to do with the external environmental conditions. It is difficult to remove and often requires biochemical reactions and a long time to remove. The external moisture is also called additional moisture. Due to the natural environment Or the moisture added to the garbage by human activities. After the garbage is stored in the garbage bin for 5 to 7 days, under the gravity of the water itself and the gravity of the upper garbage, this part of the water can leak out and needs to be processed separately. Under freezing conditions, external moisture becomes the adhesive for garbage to form. However, under normal living conditions, artificial activities will not increase the external moisture too much. Although the temperature is low, due to the low moisture, the adhesive effect is small, and generally It will not cause the phenomenon of garbage clumping; however, if the garbage is placed in the open air, mixed with a large amount of ice and snow to act as an adhesive, and stored in a low-temperature environment for a long time, the garbage will not only freeze into larger ice lumps, but may even become frozen. The garbage is frozen directly on the garbage truck body and cannot be unloaded. The higher the moisture content of the garbage, the easier it is to freeze, the greater the calorific value of the garbage decreases, the greater the impact, and it may fall into a vicious cycle

2.2 Analysis of factors that produce frozen garbage

Time The time when frozen garbage occurs should be the coldest season in 1a. The freezing of garbage into ice is not only related to the outdoor temperature, but also related to the outdoor storage time. The temperature when garbage is generated indoors is generally between 10 and 20 degrees Celsius. Nowadays, every household is accustomed to wrapping garbage in small garbage bags and throwing it to outdoor garbage collection points. According to observations in a northeastern city, at -20°C, domestic garbage has not frozen into ice after 4 to 6 hours. If the outdoor garbage is collected during this period and placed in a storage room or transfer station with heating measures, the problem can be solved. , at least reduce the problem of garbage freezing into blocks.

Temperature comparison

The changes in the calculated outdoor heating temperature in major cities across the country and the conditions of the waste incineration power plants constructed and operated found that: the calculated outdoor temperature in the heating room is -20°C and below In regions and cities such as Heilongjiang and Jilin, there are currently no waste incineration power plants with grate furnaces in operation; in regions and cities where the calculated outdoor heating temperature is -15°C or above, such as Qinhuangdao, Dalian, and areas and cities south of Taiyuan , currently there are waste incineration power plants with grate furnaces, and they have been running smoothly without considering any anti-freezing measures for waste; regions and cities where the calculated outdoor temperature of the heating is -20~-15℃, mainly refer to Liaoning Province and Inner Mongolia. Some areas, such as Yingkou and Hohhot, are preparing to build waste-to-energy power plants with grate furnaces.

Therefore, it can be delineated:

① Regions and cities where the calculated outdoor heating temperature is -20°C and below, anti-freezing and thawing measures for garbage must be considered;

②Regions and cities where the calculated outdoor temperature of heating is -15℃ and above do not need to consider anti-freezing and thawing measures for garbage; ③Regions and cities where the calculated outdoor temperature of heating is between -20~-15℃ are transitional In different regions, anti-freezing and thawing measures for garbage should be considered based on local conditions.