The invention discloses a low temperature sludge drying process, which relates to the field of sludge drying technology. The process steps are as follows: the wet sludge is crushed, extruded into a belt-type drying box, exchanged with heat-drying circulating air, converted into dry sludge, and the hot dry circulating air becomes wet. The low-temperature circulating air and the wet low-temperature circulating air are sucked into the heat pump through the circulating fan and blown from the circulating fan into the intermediate heat exchanger to exchange heat with the evaporating air to further reduce the temperature. The air exits from the intermediate heat exchanger and passes through the water-cooled pre-cooled cold plate. The tube lowers the temperature again, and after the wind passes the evaporator to evaporate, the condensate water is precipitated, and the evaporating air passes through the intercooler and the heat pump return air to exchange heat. After the air temperature is increased, it enters the condenser, and after the temperature rises, it turns into hot dry air. Sludge oven cycle treatment. The invention has low energy consumption, no secondary pollution, low drying temperature, high safety, high degree of automation and reduced sludge drying cost.

Claims

1. Low-temperature sludge drying process, characterized in that the process steps are as follows: (1) The wet sludge with a moisture content of 60% to 80% is crushed and extruded into a belt-type drying oven;

(2) The wet sludge in the belt-type sludge drying oven is exchanged with the hot dry circulation air to be converted into dry sludge with a moisture content of 30% or less, and the hot dry circulation air turns into a wet low-temperature cycle. air;

(3) Wet low-temperature circulating air is sucked into the heat pump through the circulating fan, and is blown from the circulating fan into the intermediate heat exchanger to exchange heat with the evaporating air to further reduce the temperature;

(4) After cooling, the low-temperature circulating air exits from the intermediate heat exchanger, passes through the water-cooled precooling coil and then lowers the temperature;

(5) The air from the water-cooled pre-cooled coil passes through the evaporator to evaporate, and the temperature drops below the dew point, so that the condensed water is precipitated;

(6) The evaporating air passes through the intercooler and the heat pump return air to exchange heat, and the air temperature is increased to enter the condenser;

(7) The circulating air, which has been heated up by the condenser and then heated up, turns into hot, dry circulating air and enters the belt-type sludge drying oven for cyclic processing.

2. The low-temperature sludge drying process according to claim 1, wherein the temperature of the hot drying cycle air is 60-70° C. and the humidity is lower than 20%, and is treated by a belt-type drying oven. After entering the heat pump, the wet low-temperature circulating air temperature is 50-60°C and the humidity is more than 50%.

Instructions

Low temperature sludge drying process

Technical field

The invention relates to the technical field of sludge drying, in particular to a low-temperature sludge drying process.

Background technique

Sludge drying is an intermediate process necessary for sludge treatment, from direct application to direct incineration, from dry application to incineration after drying, until the most recent post-drying gasification, basically affirming the desiccation as a The importance of the necessary intermediate process. There are two main reasons: economicality, whether it is the reduction of transportation and disposal, or the reduction of energy consumption; the necessary conditions for sanitation and agricultural use. The final disposal method of sludge drying is the choice of national conditions. Landfill is undoubtedly unacceptable. This is not only due to the high value of land, but mainly from the perspective of energy and biomass energy resources. The state requires to reduce and limit the landfilling of sludge.

At present, sludge dewatering in most industries only uses mechanically-extruded sludge dewatering, such as belt filter presses, plate and frame filter presses, stacking screw machines, and centrifugal dewatering machines. After dehydration, the moisture content of the sludge is 70%. -90% or so; the option of incineration as a means of disposal, the heat of the sludge itself is not sufficient to maintain its heat demand, so the economical nature of this type of sludge for subsequent storage, transportation and incineration is poor, which is causing the current sludge disposal The important reason for the high cost is that the requirement for drying, weight reduction and capacity reduction of the sludge of the enterprise is increasing rapidly.

At present, the domestic sludge drying process and technology are continuously developing, and the main energy sources used are mainly direct heating, ie steam, flue gas exhaust, electric heating, etc. are used to heat the sludge above 100°C to make the sludge's water content. It becomes water vapor discharge; this type of drying device has the following problems:

(1) High energy consumption: The energy requirement is 620 calories per liter of evaporation, and the direct heating drying equipment deals with the trademark claiming that the system's thermal energy requirement is 800-850 calories.

(2) Bring secondary pollution: Sludge and polluted tail gas need to be treated again to meet the standard emission.

(3) The high drying temperature brings about the problem of drying safety: The problems of explosion, toxicity and the like of substances that may be volatilized out of the sludge during the high-temperature drying of the sludge flow are difficult to avoid.

Based on this, it is particularly necessary to design a low temperature sludge drying process.

Summary of the Invention

In view of the existing deficiencies in the prior art, the present invention aims to provide a low-temperature sludge drying process, which has low energy consumption, no secondary pollution, low drying temperature, high safety, and a high degree of automation in drying, greatly reducing The cost of sludge drying is easy to use.

In order to achieve the above object, the present invention is achieved through the following technical solution: a low-temperature sludge drying process, the process steps of which are: (1) After the moisture sludge containing 60% to 80% moisture content is crushed and extruded Into the belt sludge drying box;

(2) The wet sludge in the belt-type sludge drying oven is exchanged with the hot dry circulation air to be converted into dry sludge with a moisture content of 30% or less, and the hot dry circulation air turns into a wet low-temperature cycle. air;

(3) Wet low-temperature circulating air is sucked into the heat pump through the circulating fan, and is blown from the circulating fan into the intermediate heat exchanger to exchange heat with the evaporating air to further reduce the temperature;

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