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Biomass Thermo Electric Power Station

Posted in Engineering & Technology

Power : 2 up to 10 MW
Burning Fuel : rice-husk

Brief Introduction about Biomass

The biomass power stations are plants to generate electricity using biomass as fuel, which is composed of animal origin (flour, fat, poultry droppings) or vegetable (agricultural waste, wood chips, rice-husk, mill waste, dead trees, dry leaves). The advantage of using biomass for power production are summarized as follows:
1. The biomass in contrast to fossil fuels are a renewable energy source and as such is not subject to depletion
2. Biomass is cheaper than fossil fuels
3. If the biomass of plant origin in the external environment a place equal to the amount of CO2 that plants and trees from which they have absorbed for photosynthesis during growth
4. In addition to the electric energy, the plant will supply heated water to be used by industrial utilization or house heating and steam to be used in agro / industrial workshop, to prepare partially boiled food
5. The electric power plants can be built near end users, and can be connected directly to low-medium voltage grid

The heart of the system is the reverse flame boiler, it means that the chamber of combustion is placed under the floor where it is stacked “fuel”. Since the combustion takes place slowly (as the fuel approaches the grid) is progressive and controllable. This means that the power supplied from the boiler is stable and high performance of the order of 90%.

Biomass Gasification System Concept and Efficiency

The production of 1 KW of power requires only 1.30~1.85kg of rice-husks, wood dust or crop stalks as fuel. The water used in the cooling system of this process can be recycled after undergoing a dissolved air flotation treatment and thereby having no harmful effects to the ecological system and the environment. Self power consumption of this systems is low with percentages ranging between 5~8% of the generated total power. This project is an ideal solution for regions where there are large quantities of biomass waste resources, farms, nearby forests etc.

The feasibility of such power station will give a high ROI (Return of Investments) in a short period of time. The reasoning to this high ROI is due to the cost of the fuel being negligible near zero, only work labour, drying and grinding has to be considered. In most other power stations, fuel cost corresponds to approximately 60-75% of power selling price, in our case, there is a saving of approximately 70% compared with other forms of power stations. The technology of producing power by gasification of biomass is easy to operate, simple and economical in maintenances and service, has no high pressure steam, no turbines and it is easy to start-up and run the standard combustion generator. The power station requires a small land area to operate. It is environmental friendly, simple to install, and it can gasify most kinds of agricultural and forestry biomass.

We hereby recommend the biomass fluid-bed gasification furnace and gas purifying equipment with good performance and cheap price. They can make rice-husk, wood chips, coconut fiber, dast, saw dust and crop stalks gasified into clean biomass gas fuel. The furnace can reliably work with simply automatic operation. After ignition, 10 minutes later, the biomass gas shall be produced after purifying/cleaning and cooling treatment, which can be supplied to the specially manufactured biomass gas internal combustion engine for electric power generation to meet both for the needs of customers' own use and selling surplus electric power through connecting into a power grid. However, customers such as factories can be still connected with the national power grid for their power supply is not enough, therefore, the quality and reliability of the energy are entirely the same as that supplied through the power grid. In its early stage, gasification furnace was fixed bed type, by utilizing the incomplete combustion of biomass fuel in the furnace to produce biomass gas due to lacking of oxygen. In recent years, the application of fluid-bed combustion technology makes the gasification furnace have still higher energy conversion efficiency together with simple, stable and reliable operation of the furnace. Besides, the thermal value of biomass gas has greatly been raised, reaching up to 5.0~6.3 MJ/Nm (1,200~1,500 Kcal/Nm).

The discarded biomass fuel shall be pirolysised and gasified at high temperature in the furnace and change into biomass gas which can be used after cleaning and cooling treatment as clean gas fuel of internal combustion engine for electric power generation or for supplying urban residents as gas used as household fuel, or for supplying gas to the boilers of rice mills and timber processing mills as well as hot air furnace combustion to produce steam or hot air.

The gasification furnace manufactured by using the company's patent technology has been equipped with a tar cracking apparatus, which is capable of making the gas-phase tar in the biomass gas split to the gas fuel with lower molecular weight, while by providing specially designed dust removing and tar-removing equipment outside the furnace, by adopting multi mode methods have been adopted to strictly purify the biomass gas. This furnace is also equipped with perfect operation parameter monitoring instruments of operational, together with centralized control and remote operation to meet the requirements of the internal combustion engine for fuel quality.

The gas output of the furnace has been already serialized and can meet the demand of gas supply for 200~2,000 KW electric Power generation. For the customers who need pre-treatment of biomass fuel crushing and drying, we can provide corresponding complete sets of equipment and we also can select and match auxiliary machines, and affiliated apparatus for gasifying and purifying system equipment depending on specific situations, such as water treatment in order to ensure the safe and economical operation. This internal combustion engine is designed and manufactured in accordance with the special requirements for biomass gas, by adopting the most ideal compressed ratio and the structure of single body mixer outside the generator set and equipped with the reliable explosion proof apparatus and the electric ignition system without contacts, the hydraulic governing system with excellent performance and the perfect lubricating and cooling systems, thus making this generator set have features of simple structure, solidity and long life, complete protection, stable performance, reliable and easy operation and convenient maintenance.

The associated generator is manufactured by using the Siemens Company's excitation technology without carbon brush, with excellent performance. For the capacity, sufficient considerations have been given to the tropical wet and hot climate condition to ensure long term reliable operation. The control panel associated with the generator unit is equipped with various monitoring and control instruments and measuring instruments as well as reliable automatic air circuit breaker. On the panel, you can directly make remote operation to control the generator voltage, power factor and rotating speed (frequency and the load during parallel operation). The control panel is also equipped with over-current, under-voltage and inverse power relay protection devices to meet the requirements for both single unit or parallel operation). The control panel is also equipped with over-current, under-voltage and inverse power replay protection devices to meet the requirements for both single unit or parallel operation. If a customer needs multi-unit operation or operation connecting into a power grid, we can supply special synchronous connection panel for safe parallel operation.

In order to realize highly efficient biomass pirolysis gasification to meet the needs of fluidized burning in furnace, for some discarded biomass fuel such as crop straw, pruned fruit tree branch, twig timber, chip from timber processing factory etc, they must be broken up and desiccation processed. Among the equipments, for which to be used for broken-up, crushing, desiccation, drying, transportation etc. can be supplied as per the customers' real needs.

Scheme of a 5MW Plant

The plant (cycle type: Rankine) is made by a steam generator with integrated oven for the combustion of rice husk to produce about 23,100 kg/h steam (at 45 bar pressure and 450°C), that will be processed by a steam turbine generator to generate 5,000 KW.

We notice following sections:

Storage of rice husk - will be performed outdoors under canopy forecourt to the boiler, where there are adequate drainage to channel the rain water. From here, the husk is sent to feed the boiler.

Boiler feed system - consists of 2 storage tanks protected from the elements with an extraction system by a tape that brings rice-husk directly to the boiler. The tanks are sized to ensure continuous operation of the system.

Boiler - the transport system will load the hopper distribution of husk in the boiler. The burning will take place on a moving grid blanks with alternating motion to adjust the advancement of “fuel” along the combustion chamber and thus optimize the combustion of the product.

Turbine and generator - the steam produced by boiler feeds a steam turbine generator capable of delivering a power of 5 MW.

Exhaust fumes into the atmosphere - the fumes from the boiler will be sent to a filter system before being downloaded to the chimney.

Cooling system - the steam leaving the turbine will be cooled with fresh water taken by a river or lake nearby. This water will never come in touch with burned husk and/or steam, therefore don’t require filter treatment.

Auxiliaries
- The system of water demineralization
- The compression system and dehumidification
- The extraction, storage and bagging of the ashes after husk is burned
- The electrical workshop of Low-Medium Voltage
- The control panels
- The monitoring station of the stack emissions
- In addition to the facilities and logistics (weighting station, control room, changing rooms and toilets).

Fuel Consumption and Thermal Power Input

The fuel for the boiler is made by rice-husk with a total consumption of 6 T / h

Heating value for fuel of 3,300 kcal / kg

Power feed into the boiler fuel is equal to thermal 23,000 KW

Thermal Power and Electricity

The Rankine cycle plant is designed to generate 5,000 KW of power measured at the terminals of the alternator of the steam turbine. The general service facility, or the auxiliary power generation (pumps, fans, control system, etc..) require the use of electricity for an amount corresponding to the average power of 500 KW. The figures above result yields the following mechanism:

• Gross electrical efficiency = 5,000 / 23,000 = 21.7%
• Net electrical efficiency = 4,500 / 23,000 = 19.5%

The plant is planned in continuous operation 24 hours / day

• Maximum gross electricity production = 38,000 MWh
• Maximum NET power production = 34,200 MWh

RANKINE CYCLE

General Outline of the System

The Electric Power Station here illustrated is a standard Electric Power Station of 5 MW using rice-husk as burning fuel. The Electric Power Station dimension of 5 MW is the optimal solution to meet targets of flexibility and simplicity and is the most economical solution for the Environment where the Electric Power Station shall be located.

A single Power Station could be interesting for agro industrial compounds of medium size (100.000 - 200.000 peoples), very far way from Big Electric National Power Stations very difficult to be reached by Electric National Network, and where the rice is the main farming. Into these rural areas, the number of Standard Electric Power Station to be installed shall be able to meet the local necessity. Their localisation will be distributed into the territory in a strategic way in order to make easy the connection to whole the compound.

Why Choosing Small Electric Power Stations

The Electric Power Station will supply energy to the agro industrial compound, by the mean of local Electric Network easier to built up and with cheaper cost then transportation of Electric Energy using an Electric National Network.

The Electric Power Station is feed by a fuel that does not create pollution in the environment and the production cost per Kwh are much cheaper then the cost of Electric Energy brought to the compound by the Electric National Network.

Consequently, the agro industrial compound shall have the following several advantages:
1. To have paid back the rice-husk waste, presently sold out with very low profit. In fact, the rice-husk will become the main burning source of the installed Electric Power Station
2. To have the supply of energy at low cost
3. To sell out the hash (Chrystal Silicon) remaining from the combustion of the rice-husk, to Steelworks Makers, at a very interesting price. (The package of the Chrystal Silicon hash will be made automatically inside the same Electric Power Station structures).
4. To avoid the necessity to get ride the rice waste.

The standard Electric Power Station of 5 MW of this treatise, is building-up in a modular system which can be easily duplicated to cover bigger need of power.

More Advantage of Electric Power Stations

The 5 KW Electric Power Station installed into an agro/industrial compound typology as above described, in addition to the Electric Energy, can also supply:
1. Over heated water to be used by industrial utilisation or house heating
2. Over heated water to be used by cooling system, suitable for food preserving industry or air conditioning
3. Steam to be used, between other, in agro/industrial workshop, to prepare partially boiled rice

5 KW Electric Power Stations Areas

The system herewith described, will be covering a total area of 6.500 sqm, distributed as follow:
- 1.000 sqm, assigned to the Central Building which will contain, whole the Fittings and Fixtures which require a roofed space to work well as:
Steam turbine
Demineralisation fixture
Air compressed and air treatment fixture
Whole the electrical and electromagnetic equipments

- 2.500 sqm, assigned to the fixtures which require to be installed outdoor as:
The biomass of rice-husk burner.
The filters to capture the hash.
The condenser to transform the steam into warm water

- 2.000 sqm, assigned to the biomass temporary warehouse, to be stocked before transportation to the burner.

- The rest of the area shall be used for interconnection of the system, parking areas, gardens

What described above represent the Standard Type of Electric Power Station that should be utilised by End Users located in proper Rural and Industrial Areas. The Specific Type of Electric Power Stations, shall be designed taking into account the Local Environmental real data of the chosen Rural and Industrial Areas.

Input - Output Scheme

The following table summarizes the annual flow of material into and out of the plant. The costs are calculated on the basis of a year expected in 7600 h / year:

Biomass (rice-husk) - The husk of rice needed to feed the boiler is equal to 6 T / h, corresponding to 45,600 T per year.

Water - The water consumption of the plant is derived primarily from the need to supplement the losses in the circuit. Assumption of a quantity of 8,000 m3.

Natural Gas - There is a natural gas consumption to feed the pilot flame in the boiler during start-stop system. The production cycle is continuous and does not require frequent stops, except in cases of routine maintenance stops.

Urea in water solution - The consumption of urea in solution at 33%, needed for operation of the non-catalytic reduction of nitrogen oxides is 310 T / year.

Hydrated Lime - The hydrated lime, used for the neutralization of acid gases, is about 25 T / year.

Activated Carbon - The consumption of carbon, used to remove any volatile metals, is 10 T / year.

Ash - The ashes are mined along the way, from the combustion chamber until the filter. It is about the 20% of the rice-husk burned and represent an important product (mostly silicon dioxide) thanks to high insulating properties. It is 9,100 T / year.

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