Monday, April 1, 2013

Biomass plant design

The traditional way of generating electricity from biomass is in most cases based on the direct combustion and the production of steam, which drives a steam turbine, like it is in coal power plants. This technology is now very sophisticated and allows the use of several types of starting materials. Its disadvantage is that it requires relatively high investment costs per unit of output, the overall production efficiency is low, and also provides opportunities for further improvement.

Producing electricity by biomass gasification is a new method. Rather than direct combustion of biomass, gasification process is utilized and the subsequent burning of the gas in the gas turbine. The advantage of this technology is much higher efficiency, because in gasification to 65-70% of the energy contained in the biomass is converted into combustible gas. Investment costs for the construction of gas turbines are relatively low and there are also significant opportunities to improve technology. Although the method provides several advantages gasification is not yet sufficiently developed for it to be able to be used widely.
Plants with biomass gasification consists of the following components:

  •   Apparatus for transport and fuel
  •   Gasification reactor vessel
  •   Gas cleaning and mixing system
  •   Turbine respectively. combustion engine

What is biomass

Biomass is plant or animal organic material suitable for industrial and energy use. In terms of energy productin, plant biomass - phytomass is very important. Everything growing in the fields or woods is chemically preserver solar energy.

Biomass for energy occurs mainly as waste in industrial, construction, forestry, agricultural and livestock production as well as residential municipal waste. Wood and wood waste can be used directly in boilers for heating the heat carrier heating system and hot water or steam. Wood waste can be compressed and briquetted. The agricultural and livestock production creates large quantities of waste such as straw. Biomass can be used not only for heating but also for gasification and combustion in gas cogeneration units for power generation. Liquid and gaseous forms of biomass (ethanol, methanol, wood gas, biogas) can also be used to power motor vehicles. Its use reduces dependence on countries from primary sources imported from abroad reduces the burden on the environment, contributing to the reduction of CO2 emissions, reducing emissions from burning fossil fuels, to better appreciate domestic raw materials and so on. The great advantage of biomass is that it is renewed annually at a purposeful cultivation can be almost inexhaustible source of raw materials and energy.

All the fossil fuels that we consume today (coal, oil, natural gas) are essentially ancient biomass, which is changed by pressure, temperature and chemical reactions to these concentrated sources of energy. However, the process takes millions of years, so we consider these non-renewable fuels. Fossil fuels affects the environment by burning them in the atmosphere of the receiving agents that are millions of years old "preserved" under the surface. Unlike the burning of fresh biomass in terms of greenhouse gas neutral. The combustion of biomass, the oxygen from the air combines with the carbon in plant and generates carbon dioxide and water, and carbon dioxide is a substance of the new entry biomass.

Due to the different forms of biomass varies the energy it contains. Energy content of dry product (moisture content 15 to 20%) is around 14 Completely dry biomass may therefore be in terms of energy content compared to coal, which has a calorific value of 10 to 20 MJ. kg-1 in brown coal and about 30 for black coal. At the time of collection, however, biomass contains significant amounts of water, ranging from 8 to 20% for straw, 30 to 60% in fresh wood, while for coal is about 2 to 12%. Chemical composition of biomass, however, makes it a much more environmentally friendly fuel as coal. Biomass in comparison has lower sulfur coal. The ash content in the burn is also lower than in the case of coal, the ash also does not contain toxic metals.

Sunday, May 23, 2010

4 phases of methanogenesis

The biogas is a major product of biogas plant. Most is burned in the cogeneration unit and receives the electrical energy and heat.

The biogas is generated by the bacterial activity without access to air. The Fermentation involves different types of microorganisms.

We can divide whol process into 4 phases:

1. Hydrolysis - in the environment is still oxygen in the air. Polymeric organic compounds (polysaccharides, fats, proteins) are broken down into simpler monomers - alcohols and fatty acids, releasing hydrogen (H2) and carbon dioxide (CO2).
2. Acidogenesis - consumes the remaining oxygen in the air and creates the anaerobic environment (without oxygen). This phase is made by viable microorganisms in the environment with or without oxygen. This creates higher organic acids.
3. Acetogenesis - with help of bacteria are more organic acids and alcohols transformed to acetic acid, H2 and CO2.
4. Methanogenesis - final stage of degradation process. Bacteria are strictly capable of life only in an environment without access to air, acetic acid decomposes into methane (CH4) and CO2. Some strains produce methane from CO2 and H2. This final phase is about five times slower than the previous three phases, so the size of the fermenter must be adapted to dosage of starting materials.

The resulting biogas is essentially a mixture of methane and CO2, which contains impurities such as N2, H2S, NH3, H2O:

NameChem. formula%
Carbon dioxideCO225-55%

The most problematic chemical is hydrogen sulfide (H2S), because if it is in a quantity over 0.1% it is corrosive to engines and technological equipment. Ammonia (NH3) is a source of odors. The presence of CO2 in the biogas is a benefit if the biogas is burned in cogeneration, CO2 acts as if the anti-knock in internal combustion engines.

Thursday, May 20, 2010

Heating in winter

How to make energy-independent house with the advent of winter each year, beginning each survey as it could save on heating as they easily survive the winter to reduce heating costs in the ever-increasing prices for energy? Of course, this question makes me not sleep. While the ideas may be enough and perhaps those that would be feasible, yet their implementation is needed funds and also some significant level of skill. And there is the question - can I make it?

In general, the answer is very simple. Put some solar collectors - but for the winter? So we can build a wind power plant - or large or small hydroelectric power plant, ... Such responses are interesting, but they can't save energy. First we need to say location where the house is situated. Where we want to build own power. We do not have any house in the valley, which is enough water in winter and freezes. Not everybody can build a wind turbine - because the neighbors would say. The sun is not much, even though they live on in the winter and sunny days.  

One suggestion, a little fantasy is a small construction equipment, which is based on wood gas or biogas. The skilled engineers / turner, welder, etc... for them it is not a problem to produce wood gas generator. And such a generator can make electricity from the combustion gas. There is a big problem, because it is not a classic addition gasifier as we know from cars. So the output we will have are electricity, and the residual heat - it will put a relatively large reservoir. From here we can provide heat for house and hot water. And the generator can reduce consumption of electricity from the grid.

Biogas - first try

My first attempt was in the PET bottle, but it did not last a higher pressure of biogas and PET bottle exploded. Luckily it happened outside in the garden, not inside the apartment. Advised that pressure in the generator is obviously great, so I made a mini generator instead of a glass container with a lid on the thread. The lid was metal, so I drilled a hole into it and solder copper tube. Generator shoul  be able to stand on the lid, I used more cork stopper that I stuck to the lid. I bent the tube and pushed into the cut PET bottles. Hole I thoroughly sealed with silicone adhesive. PET bottles I tested the water and made a tight fit. I poured water and made into small jars, which went to freely insert snip PET bottles. It was a matter of collecting bottle to leave no air. Methane is lighter as the air and mixed with air is highly explosive. Never light first developed biogas! May contain air and lit an explosion!

What is it feeds.

On the first attempt, I gathered poultry manure, which I have filled one-third liter PET bottles. I also added the same amount of cut grass. Everything was poured by rain water about 1.2 liters. All shake thoroughly and put in a warm place. Already in few hours it begins to ferment and develop its own gas. Once again highlights the danger of explosion during the first ignition of gas. We can use this PET project aj base for a large generator, but several times each day we should to free excess pressure in the bottle. Otherwise,thread PET bottles may explode. Large generator will be feed from kitchen waste, potato peelings, food leftovers but also if the old paper cut or picked into small pieces. Furthermore, all the waste of plant origin!

Pitfalls of anaerobic digestion

Gas appliances are designed for the combustion gases under constant conditions, is fed into the burner air (oxygen), in the case of methane (CH4) ratio of about 8 cubic meters of air per 1 m3 of gas. This design ensures the correct ratio of the burner of the appliance (stove, heater, or boiler), but also requires a constant pressure of gas (methane at about 200 mm water column).

Homemade appliances often lack the very important aspect - safety relief valve, which prevents the rise of pressure above the safe level. Therefore, described the explosion ....

The pressure required will ensure open hose, connected to a tank of gas (ie gas holder) and submerged under water 200 mm deep .. hose would work well as a safety valve - blows away the excess gas into the atmosphere.

Several years ago I had seen a description of a small gas works, designed for the use of natives in Africa, performance was perhaps 3-5 m3/day. More energy-efficient than wood burning in the primitive fireplace.

Gas could be implemented as a plastic bag, and could be inappropriate to restrict the oxygen in the gas at the rotting process.

ATTENTION! ATTENTION! gas is very dangerous medium, ATTENTION!

Wednesday, May 19, 2010

Disadvantages of anaerobic digestion

What can be better than have your own gas station? There is enough grass or other manure. Cows on pasuture are walking gas stations...But

note of any significant hazards lay experimenting with fuel gases. Gas is extremely dangerous, mainly because the next molecule compounds that burns (CH4), are located in close proximity oxidant molecule (O2). Combustion of such mixtures is a blast. 

It will take place in a split second, immediately raise the temperature of flue gas (gas formula PV = Rt), this leads to a large increase in volume or pressure in an enclosed space and the destruction of the structures. Such an explosion destroyed bridges, cut up houses, maim and kill people. Therefore, all gas equipment must be operated in accordance with applicable regulations. Equipment subject to regular checks and reviews, without them it is their operation illegal and punishable.
When somebody wants to experiment, whether they do so somewhere in the open, not in an apartment house or perhaps the basement!