Because all pores of the straw are exploded and water can penetrate into the straw, it also renders access for those microorganisms and enzymes that are digesting the straw into biogas.
This ensures a relatively quick and effective digestion in the biogas plant.
You will get efficient and thoughtful service from Tiantai.
The direct feeding of dry briquettes into bioreactors does not impact the hydraulic capacity of the biogas plant. It is unnecessary to suspend the briquettes in raw manure or digested manure under severe stirring or such before adding to reactors. No extra tanks fitted with stirrers are needed.
In the case of a briquetting plant being installed at the biogas plant and briquettes being added directly when produced, process heat is also added to the reactors, i.e., the kinetic energy dissipated into the straw is recycled into reactors. The electric power used is recycled as heat into the biogas process.
Also, the straw briquettes do not pass heat exchangers and possible clogging here is avoided.
The compressed straw is emptied for atmospheric air, notably free nitrogen and oxygen, and air is therefore not added to the biogas, when using straw briquettes. This is highly advantageous, when the biogas is upgraded to natural gas quality.
Local circumstances and conditions will determine if it is advantageous to develop local satellite stations for local collection and processing of straw into briquettes before storing and transportation to one or more biogas plants.
Briquetting uses very little energy and no water for the pre-treatment. The electrical power use of app. 75 kWh per tons straw is mainly reused as heat in the biogas reactor if the processing plant is placed at the biogas plant.
Conventional pre-treatment of straw before a biogas or bioethanol process such as steam explosion at 180-200°C and 30-40 % dry matter is a highly water and energy demanding process, which also impacts the hydraulic capacity of the biogas plant negatively.
Straw inevitably contains gravel, soil or sand, or other impurities. A straw line removes all impurities before the briquetting. The mechanical press is not exposed for this wear and tear and the impurities are not imported into the biogas facility.
Briquetted straw gives rise to high and stable biogas yields.
Straw generally contains 18-19 MJ/kg dry matter primary energy corresponding to app. 500 Nm3 methane per tons straw dry matter.
The straw composition is 60-70 % cellulose and hemicellulose, 15-20 % lignin, other organics (5-10 %) and minerals (app. 5 %). Normally, it is the bulk of cellulose and hemicellulose, which, after briquetting, is digested into biogas, while lignin is largely un-digested.
With briquetting, biogas yields of app. 250 Nm3 methane per tons straw can be achieved increasing to app. 300 Nm3 methane per tons under optimal conditions.
A hydraulic retention time of 30-40 days at thermophilic temperatures are needed to achieve these yields. The highest yields can be achieved with addition of potassium lye during briquetting.
The quantity of straw, which can be added to a manure based biogas plants ' the organic loading rate ' is equally important. It is clearly demonstrated that 10 % straw briquettes relatively to the liquid manure can be added without any difficulties. See a comparison below:
Biogas yields using dry straw; increased production
Pre-treatment Methane yield
(m3 methane/tons straw) *Estimated max quantity to be added manure plants
(in % of slurry) Increased yield per tons slurry (in Nm3 methane)
Shredded straw 200 1-2 % 2-4 10-20
Other mechanical processing of straw 225 2-6 % 5,5-13,5 27,5-67,5
Briquetted straw 250 8-12 % 20-30 100-150
Briquetted straw with catalyzer 300 10-12 % 30-36 150-180
Several manure based biogas plants, if not most plants, are at the brink of ammonia inhibition. In any case it is virtually impossible to add significant quantities of nitrogen containing wastes such as poultry manure.
Straw briquettes help alleviating ammonia inhibition and stabilize the digestion process. An increased yield of slurry is achieved when co-digested with straw briquettes.
Mechanical briquetting of straw for biogas purposes is the most tested, documented, and safest technology of using straw for biogas purposes.
If you want to learn more, please visit our website Straw Briquetting Machine.
We are proud to offer this cost effective solution for industrial utilization of straw for biogas.
In Kinetic BioFuel A/S we are proud of our technology and company, and enjoy our work.
Biomass is recognized as an efficient and an environmentally friendly alternative to fossil fuels. Densification of biomass is an important element in trading and handling biomass, as densified fuel offers logistical advantages, and becomes a commodity ensuring high energy content and homogenous quality. Within densification, pellets are best known, but briquetting offers many alternative advantages.Traditionally, briquetting technology was established for developing countries to produce briquettes of local residues, for use in household cooking stoves and restaurants. Later, as the capacities of the machines increased,
briquettes were used in industrial boilers to create heat, steam and power for industry and power plants. Within the past 20 years, briquetting has also found its way to households in industrialized countries as consumer logs for wood-burning stoves and fireplaces.
In recent years, as the focus on renewable energy has grown, the applications for briquettes have grown concurrently, as have different technologies and new applications.
Briquetting Technologies
Briquetting technologies include mechanical briquetting presses, hydraulic briquetting presses and screw presses; it is important that customers select the best technology for their applications.
Mechanical
The mechanical briquetting press is built like an eccentric press, and has a very simple design. A constantly rotating eccentric, connected to a piston, presses the raw material
through a conical die system, where the briquettes are being formed. Large flywheels secure a very quiet and balanced operation. The press operates with 270 strokes per minute. The briquettes are cooled and hardened in a cooling line, which also serves as transportation of the briquettes. The presses work fully automatic, resulting in a smooth operation with very little maintenance and service. The robust design ensures a long life span and the presses can operate up to 7,000 to 8,000 hours per year.
C.F. Nielsen has more than 70 years' experience with briquetting machines and, over the years, has developed new equipment and increased capacities, so that the range is now
from 200 kilograms per hour (kg/h) up to 5.000 kg/h per machine. The briquettes can be produced in sizes from a diameter of 50 millimeters (mm) to 120 mm, and in square
form from 55 mm by 55 mm to 100 mm by 100 mm. Other shapes can also be produced.
The main advantage of a mechanical briquetting press is that the press can be used both for consumer logs and industrial briquettes for boilers. Industrial briquettes can either be made as short pucks, at random lengths or cut to a defined length. Further advantages are high capacity, low production costs, and multiple densities.Hydraulic Presses
In a hydraulic press, the raw material is pressed into a precompression chamber by a dosing screw. In the chamber, the exact amount of material is precompressed. The main piston transfers the raw material into the die that forms the briquette into its final state and required density.
The compressionprocess of a hydraulic press is relatively slow. The compression cycle can be between six and 25 cycles per minute, depending on the amount loaded or the density of the briquettes. Hydraulic briquetting
presses were traditionally small, with capacities from 50 kg/h up to 200 kg/h. Briquettes were round, with a diameter of 50 mm to 75 mm.
However, today, hydraulic briquettes can be made in primarily rectangular forms with a capacity up to 1.5 tons per hour. The traditional size is 150 by 60 mm, but bigger briquettes can be made.
C.F. Nielsen's BPH-Quattro briquetting press, a hydraulic press has a capacity of up to 600 kg/h. The briquetting press is a self-contained unit, with a small dosing bin, PLC control panel and the briquetting press. The press can produce briquettes with a high density due to a large main motor and cylinder. The rectangular briquette is a uniformsized briquette that is easy to store. The briquettes have a lower density slightly below 1, which gives a shorter burn. The press can produce good briquettes from mixed materials of larger particles, and is very compact. The briquettes are typically used as consumer briquettes for fireplaces and wood-burning stoves.
Please note that this hydraulic briquetting machine is no longer offered by C.F. Nielsen. We refer to our new sister company RUF Briquetting Systems.
Screw presses
In an extruder briquetting press, the raw material is fed into a chamber by a feeding screw. The raw material is compressed by a compression screw into the conical die and extension die. The compression screws are conical in shape. The screw operates with approximately 800 revolutions per minute, and during the process high heat'up to 300 degrees Celsius' is being generated in a combination of friction and heating of the die system.
The BP Shimada Screw Press has capacities up to 500 kg/h. The press is a self-contained unit with a small bin, PLC control panel, smoke hood and saw. The screw press is a machine for high-quality briquettes with a very high density. The machine is a more delicate press, requiring very homogenous raw material with very fine particles (between 2 and 6 mm) and the moisture content between 6 and 8 percent. If these requirements are met, the machine will produce state-of-the-art briquettes that will burn longer than all other alternatives. The briquettes are typically used as consumer briquettes or logs for fireplaces and wood-burning stoves.
Today, briquetting is obtaining renewed attention. A briquetting machine is more simple and easier to operate, which opens new possibilities in new markets such as Africa, Asia and Latin America. Furthermore, briquetting presses can handle a larger range of raw material such larger particles, waste with higher ash content and special raw materials. Some examples of these applications include the following.
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