Mechanism of sludge carbonization

Author: Taida machine       Release time:2016-08-18
Reading guidance:1. Composition of sludge Dry matters in sludge are mainly composed of two parts, organic matters and inorganic matters. Organic part of a major source in activated sludge microorganisms, in addition to
Mechanism of sludge carbonization

Mechanism of sludge carbonization
1. Composition of sludge
Dry matters in sludge are mainly composed of two parts, organic matters and inorganic matters. Organic part of a major source in activated sludge microorganisms, in addition to the outside and a large number of difficult to biochemical treatment of organic matter, but decreased. Microorganisms are composed of protein, fat, carbohydrates, such as Tianjin a sewage processing plant sludge organic compounds of carbon and water accounting for 49.27%; fat 10.29%, protein accounted for 40.14%.
2. Lytic response of organic water
Carbohydrate, fat, and protein can be hydrolyzed under certain conditions:
Carbohydrate, water and monosaccharide
Fat, water, glycerol and higher fatty acid;
Protein, water and amino;
Chlorinated compounds in alkaline conditions can be hydrolyzed, for example:
In addition, the study showed that in addition to the dissolution of organic matter, when heated to a certain temperature, the inorganic part of the material will also be dissolved in aqueous solution.
3. Carbonization process of sludge
A. Description of reaction process
   Sludge material mostly exists in the form of microorganisms, microbial cell wall and cell membrane is mainly composed of lipid and protein substances. Sludge is heated, when the proper temperature is reached, composition of cell wall and cell membrane lipid and protein hydrolysis, the cell begins to rupture, intracellular organic matter spread to the outside of the cell, water from the cells from. At this time, 80% moisture content of sludge began to change into a liquid, sludge into the mud.
   The organic matter from intracellular diffusion into the water are not dissolved in the water, just a portion of the dissolved, dissolved the portion of the organic matter occurred hydrolysis reaction, such as fat hydrolysis into glycerol and fatty acids; carbohydrates hydrolyzed into small molecular polysaccharide and monosaccharide; protein hydrolyzed into peptides, amino acid. Due to hydrolysis reaction and dissolved organic matter quality decreases, the original is not dissolved organic matter can dissolve again a part. The longer reaction time, solid part of the less.
B. The quality of sludge will be changed after carbonization
   Due to the dissolution of organic matter, hydrolysis, microbial cell structure is destroyed, sludge particles become smaller, bound water, capillary water condition no longer exists, the viscosity of the sludge variable small, increase the flow of the sludge. Proteins, carbohydrates by macromolecular compound variable for small molecular monomer, molecular quantity is small. It also helps to on the viscosity of the system is reduced.
   With the change of the sludge characteristics, carbide slurry after routine dehydration, moisture can be reached 40% below and in the general stacking conditions, sludge easily air dried, sludge water rate may be further reduced to 10% to 20%.
C. Reduce the production of harmful gas
   Under high temperature and high pressure, amino acids may also be degraded, for example, the amino acids produced by hydrolysis of proteins will continue to react to produce volatile fatty acids, CO2, NH3.
   Fatty acid produced by hydrolysis of fatty acids and amino acid reaction of fatty acids produced by the reaction of fatty acids:
   Due to the occurrence of the above reaction, after treatment, the sludge will produce a small amount of gas, the quality of dry matter will become smaller. The reaction to produce the gas is generally dominated by CO2, accounting for more than 90%.
D. Elimination of organic chlorinated compound
   In a strong alkaline environment, the organic chloride contained in the sludge can also be hydrolyzed, and the chlorine element exists in the form of the ionic state, and can be discharged with the supernatant liquid, so that the content of chlorine in the carbide can be reduced.
E. Thermal value of carbonization
   Because there is only a small fraction of organic matter dissolved in the raw sludge dry matter. The hydrolysis reaction occurs and the CO2 does not take away the energy. The organic matter is the maximum retention. The reaction of carbide has a high calorific value.
After carbonization, the sludge can be burned directly without adding any auxiliary fuel, and the reduction of chloride ions in the incineration process will not produce dioxin, which will not cause pollution to the atmosphere.
4. The influence caused by temperature and pressure to carbonization of sludge
    Organic matter in water solubility generally with increasing temperature increased. Therefore, the higher the temperature cell cracked more granular sludge in water solubility is. Cells under the greater damage. For example 170 DEG C and heated for 30 min, cells structure will be damaged, sludge particles by the original larger cells become smaller cells; 190 DEG C heated for 30 min, granular sludge will become smaller.
The higher reaction temperature of carbonization is, longer the time will be; less sludge production will be.  
After times’ of tests, the best reaction temperature is 260 degree centigrade; reaction time is 10 to 15 minutes.
 Due to the sludge turbid carbonation process, sludge is always in under high temperature and high pressure, there is no evaporation process, therefore Bigan of consumption needs to lower 1 / 4 to 1 / 5. At the same time, due to carbonation is in fully confined conditions of the cleavage reaction, maximally retains the sludge can be used to. This is carbonized sludge why can direct combustion.
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Mechanism of sludge carbonization
Mechanism of sludge carbonization

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