Waste not, want not. Waste is potentially a resource. From traditional point of view, the daily waste has been regarded as worthless however from the point of view of resource efficiency, the daily wastes can be recovered and recycled and reused at every procedures of production and consumption.
Wastes can be classified into various categories based on its sources. Generally, they can be sorted into the following categories, such as municipal wastes, residential wastes, commercial wastes, industrial wastes, construction and demolition wastes, hazardous wastes and other wastes. Among them, residential waste is closely related with every citizens each day, which refers to the wastes generated by households living, including kitchen and gardens organic wastes, recyclable waste such as paper, textile, plastics, etc, and non-recyclable wastes and batteries-like hazardous waste, etc.
Moisture contentMoisture content directly influences the disposal of the wastes. Moisture content will decide whether they will be converting into compost or biogas or into solid fuel or be used as landfill stuffs. So far, there are various moisture meters available to check the waste moisture content.
Calorific valueCalorific value of wastes determines the energy value. The waste calorific value affected by moisture content and hydrogen content in it. The following steps should be carried out to determine the waste calorific value:1. Wastes should be sorted into sample fractions and be analyzed accordingly. 2. Calorific value of dried materials(shortened as CVupper) is used from known date. 3. Calorific value of dried materials be analyzed for the sample fractions. 4. Hydrogen percentage( shortened as H) is used from known date. 5. Moisture content of fractions is determined.6. Calculate for fraction calorific value( shortened as CV raw) according to the formula below:CVraw=??1-MC?*( CVupper-(2241* 9)*H)?-2441*MC.Note: 1. MC means the percentage of moisture content by weight. 2. 2241 refers to vaporization enthalpy of water, 2241 kj/kg at 25 ?.
Daily solid wastes is usually mixed with different waste components and some of which may can be produced into fuel and some of which can not be. For your reference, the following table is presented which may be revised based on local regulations or laws in each country.
As for high calorific solid wastes, briquetting is one of the ways to turn the wastes into treasure. Briquetting technology is used to densify the loose combustible materials into solid composites of different shapes and sizes with the presence of pressure and binding agents.
Generally, there are a wide range of materials that can be used to make briquettes, such as waste paper, cardboard, water hyacinth, agricultural residues, charcoal dust, and wood wastes like sawdust, etc.
1. Using fuel briquettes means to chop less firewood and less charcoal to buy, saving time and money and do contributions to ease the environment pressures.2. You will get free fuel for cook if you make your own briquettes!3. Make money by selling your briquettes!4. To make briquettes form daily wastes means the rubbish on the streets an dumps will be reduced.5.Briquettes have a durable quality, high burning efficiency and convenient to be stored and transported.
Un-favorite features of briquetting 1. Large scale briquetting equipment needs high investment while small scale briquettes production equipment is not widely applied. 2. Wet weather may lower the density of briquettes, harming briquette quality.
Generally, the briquettes are made through the following procedures:1. Raw materials preparation: mechanical fragmentation of raw materials by a crushing machines(which is up to the quality and size of the materials and the technology applied, and the procedure can be staged).2. Drying of the crushed materials when the moisture content is too high for briquettes production.3. Briquette the processed materials by using various types of briquetting machines such as the screw pressing machines, stamping pressing machines and hydraulic briquetting machines). The briquettes are made in the process of pressure agglomeration, in which the loose materials is molded into a permanent , geometrical and defined dimensions by the compaction pressure and intermolecular forces and bonds when necessary.
Briquetting densification technologiesBriquetting is one of the densification technologies for converting biomass wastes into solid and convenient fuel. Briquetting technologies can be classified in the following categories based on the mechanical features and equipment involved: piston press densification, screw press densification, roll press densification and manual presses.
The mechanical piston presses are usually applied for large scale production which ranges from 200 to 2,500 kg/ h. The mechanical press is an eccentric press in design. A continuously rotating eccentric which is connected to a plunger presses the feedstock through a conic die. In mechanical piston presses, the required counter pressure only can be adjusted by mounting a die with a different conicity. The mechanical piston press is driven by electric motor which limit the energy lost and the output in relation to power consumption is optimal. Comparing with the hydraulic press, the mechanical piston press has a longer working life and gives a better investment return.
Screw presses can compact materials with the ratio ranging from 2.5:1 to 6:1 or even more. During briquetting, the feed stocks is extruded by one or more screws through a taper die with high pressures and temperature which meld the lignin present functioned as a binder. Due to the high temperature, the out layer of the briquette is carbonized and center hole of briquette promotes combustion efficiency.
The roller presses densify the biomass material on the principle of pressure and agglomeration, where the pressure is worked between two counter-rotating rolls. The fined feedstock which is forced through the gap between the two rollers is pressed into the die holes and the densified fuel is formed. The quality of the densified fuel is closely related to the parameters of the roller presses, such as, the diameter of the rollers, the shape of the die, the gap width and the force of rollers.
The roller presses is consisted of two identical cylindrical roller, which rotate on parallel axes horizontally in opposite direction, which allows feed to be drawn in one side and densifed fuel products to be discharge out the opposite. The gap between the two rollers refers to the distance between the two rollers which is decided by many factors, such as the species of the feedstock, the size of the particles, the moisture content and the binding agent, etc. The die decides the shapes of the densified fuel products.
Manual presses are frequently used in under-developing countries. There are various types of manual presses, with the advantages of low investment and operation cost and low levels of required skills. Manual presses mold the feed stock with lower pressure with high moisture content which should be dried after shaping into briquettes. The dried briquettes has low strength and can be crumbled easily.
Briquettes fuel are usually used in boiler plants, heating plants, power stations and thermal power stations, as well as by individual customers for household use. It is also possible to use fuel briquettes in the fireplaces and conventional boilers that once use coals or woods with or without a little modification. The increase price of the conventional fuels urges the demand for the briquettes fuel and affects briquette fuel price and the briquette machines price as the increased public awareness to the environment protection.