CZ2006176A3 - Burning of wet stillage in order to environmental friendly produce heat and electric power for distillery own consumption - Google Patents

Abstract

Wet stillage burning in the form of a paste with a dry matter content of 30-33% is carried out in a fluidized bed steam boiler or a special grate, which produces steam to drive a counter-pressure steam turbine with a generator to generate electricity and supply lower steam steam for the technological process of the main process. In the boiler, it is burned as an auxiliary fuel for start-up and natural gas and possibly also for biogas. The wet paste in the form of a paste at a temperature of up to 100 degC may, depending on the type of the main process technology, be only the skimmed residue from the distillation or the skimmed residue from the distillation mixed with the syrup from the evaporation station.

Description

The present invention relates to a new technology for processing by-products from bioethanol production in grain distilleries. At the same time, the invention is concerned with the production of heat and electricity from biomass.

BACKGROUND OF THE INVENTION

So far, the following methods of utilizing solid grain residues after distillation of stillage have been known in the field of the production of alcohol (bioethanol) from cereals based on the distillation of a fermented mixture of cereals, water and additives.

after drying to 90% dry matter content, they are added as a volumetric component to livestock feed mixtures after drying to 70 to 90% dry matter content are burned in boilers and improve the distillery's energy balance

Drying of stillage presents at least three problems to bioethanol producers.

The first problem is the high energy consumption for the drying process and thus increased operating costs.

The second problem is that the dried stillage is in the form of dust, which is explosive under certain conditions. This means some restrictions for manufacturers, as they have to incur additional costs to ensure increased safety measures.

The third problem is the relatively high investment cost of acquiring the drying technology. The use of dried stillage for addition to compound feed has recently been limited by the saturation of the market with this commodity.

SUMMARY OF THE INVENTION

We, as energy equipment specialists, have considered how the current recovery of dried stillage is energy disadvantageous and we have come to the essence of our invention based on the combustion of wet stillage in the form of paste with a dry matter content of 30-33% in a specially designed fluidized bed steam boiler. bed or a special grate that produces superheated steam for driving a back-pressure steam turbine with a generator to generate electricity and supply steam of lower parameters for technological use in the main process. The boiler is burned as an auxiliary fuel for start-up and natural gas and possibly also biogas, if the technology includes a wastewater treatment plant with its production.

The wet paste in the form of a paste with a temperature of up to 100 ° C, according to the type of process of the main process, can either be only the centrifugation residue or the centrifugation residue mixed with the syrup from the evaporation station.

This method saves the costs of construction and operation of equipment for drying and subsequent handling of stillage.

This idea is original and will provide bioethanol producers, in addition to saving on investment costs, also providing an advantage in the production of heat and electricity for technology, since it is a combined production from biomass that is subsidized by the state.

Ing. Miloslav Pavelka

Ing. Mojmír Pouchlý \

March 2006

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Size of the energy center

Bioethanol producers were supposed to produce and deliver 400,000 hectoliters of bioethanol per year. We used this basic data for the first designs of the combustion plant. Given that manufacturers are no longer limited in production capacity, our proposals had to be expanded to outputs of up to 1,000,000 hectoliters of bioethanol per year. Below 400,000 hectoliters per year, there is a problem with return on investment and above 1,000,000 hectoliters per year is the problem of transporting raw material from a long distance. However, it is still possible to use our technology beyond these limits.

There are several types of bioethanol production from cereals, and we have focused on the one where, after distillation of the cereal yeast, a by-product of stillage is produced in addition to the main alcohol product.

The material balance for a production unit of 400,000 hectoliters of alcohol per year shows that about 45 tons / h of grain produces about 45 hels / h of pure alcohol and about 39 tons / h of liquid stillage. These stillages are centrifuged to produce about 17 t / h of wet stillage in the form of a paste containing about 33% dry matter and waste water, from which up to 500 Nm ³ / h of biogas can be produced in a sewage treatment plant. This unit consumes approx. 24 t / h of steam at 3.5 bar, 150 ° C and an electrical power input of 4.3 MW to operate at rated power.

The material balance for the production unit of 1 000 000 hl of alcohol per year shows that about 120 t / h of grain produces about 120 hl / h of pure alcohol and about 100 t / h of liquid stillage. These stillages are centrifuged to produce about 40 t / h of wet stillage in the form of a paste containing about 33% solids and waste water, from which up to 1200 Nm ³ / h of biogas can be produced in a sewage treatment plant. This unit consumes approx. 65 t / h of steam at 3.5 bar, 150 ° C and an electrical power input of 8 MW to operate on rated parameters.

For units with outputs between the above limits, material balances can be extrapolated with relatively good accuracy. For units outside these limits, it is necessary to proceed on a case-by-case basis.

Description of the power center equipment

The project assumes the use of heat from stillage with minimal losses and that all stillage from the main process, which includes grain milling, liquefaction, fermentation, distillation and dehydration (see bioethanol production scheme) will be brought after centrifugation and possibly mixed with evaporation syrup in the form of a paste containing about 33% dry matter to the boiler room. The stillage thus prepared will be burned in a boiler with either a fluidized bed or a special grate. All steam produced from the boiler is fed to the turbine.

The boiler is self-supporting, membrane-type with natural water circulation, designed to always burn off combustible substances and distribute harmful compounds.

The energy from the stillage does not cover all the distillery needs and therefore two gas burners are used in the space above the fluidized bed to achieve the required heat input and at the same time to ignite the boiler. Gas burners burn natural gas especially when the distillery is started and after the operation has stabilized, biogas produced, for example, in a sewage treatment plant.

The boiler can also burn other types of fuels such as brown coarse coal dust, biomass of other properties (wood chips, shredded bark, sawdust), bone meal, shredded production waste, etc.

Steam of 55 bar (g), 450 ° C emerges from the boiler and is led to the inlet to the back-pressure steam turbine. When steam passes through the turbine, electricity is generated which covers a substantial part of the distillery's own consumption. At the same time, the extraction steam with the parameters 7 bar (g), 260 ° C and the backpressure steam with the parameters slightly above the steam saturation limits of 3.5 bar (g) and 150 ° C emerges from the turbine. These vapors cover all the requirements of the technological part of the distillery for heat supply.

Ing. Miloslav Pavelka

Ing. Mojmír Pouchlý

March 2006 «· · · * * * * * * * * * *

All equipment will comply with standards, regulations and regulations for the operation of power equipment. As the auxiliary equipment is part of the bioethanol production plant, the power center project has been designed so that its operation is semi-automatic and requires minimal service and maintenance.

The estimated operating time of the energy center is 8,400 hours per year.

Examples of equipment operating parameters

Main fuel

It changes

Calorific value Qj ^r (at 20% humidity) Water content W _t ^r max.

Ash content A ^d max.

Sulfur content Nitrogen content Ν ^ΛιΓ Auxiliary fuel

Distillery

Boiler output: nominal Steam pressure: rated

Steam temperature: nominal at supply water temperature:

Amount of burned guarantee fuel spirit alcohol stillage paste

15.0 MJ / kg 68 % 3.0 % 0.09 % 1.0 % earth gas biogas (> 80% methane) 400 1 000 thousand hl / year 26.5 65.0 t / h 55 55 bar 450 450 Noc: 2 ° C 105.0 105.0 ° c 17 40 t / h

Efficiency approx. 82.0%

Emissions: (max. Values according to Government Order 352 of 3.7.2002)

NO _X 650 mg / Nm ³ WHAT 650 mg / Nm ³ CO ₂ 2500 mg / Nm ³ Solids 250 mg / Nm ³ Organic substances 50 mg / Nm ³

Emission values refer to dry flue gas, oxygen content of 11% and combustion of guarantee fuel. Flue gas temperature after boiler is informative 160 ° C

Turbine power rating 2.54 6.5 MW Nominal inlet steam pressure 54 54 bar Nominal inlet steam temperature 445 445 Noc: 2 ° C Nominal steam flow rate 24 65 t / h Vapor pressure in sampling 7 7 bar Steam temperature at sampling 260 260 Noc: 2 ° C Steam flow from sampling 2.4 5 t / h Vapor pressure at outlet 3.5 3.5 bar Steam outlet temperature 200 200 Noc: 2 ° C Steam flow from outlet 21.6 60 t / h Generator speed 1500 1 / min. Generator voltage 6.3 kV Distillery electric power consumption 4.3 8 MW Must be delivered from the network 1.76 1.5

The heat consumption of the distillery is fully covered by the supplied steam

Ing. Miloslav Pavelka

Ing. Mojmír Pouchlý

March 2006

PV · '

Claims (8)

A method for producing saturated or superheated steam, characterized in that in a fluidized bed boiler wet grain stillage from bioethanol production in the form of a paste with a dry matter content of about 33% is burned. 2. A method of producing saturated or superheated steam, characterized in that in a grate-fired boiler, the wet grain stillage from bioethanol production in the form of a paste with a dry matter content of about 33% is burned. 3. A method of producing saturated or superheated steam, characterized in that in a fluidized bed boiler wet grain stillage from bioethanol production with a dry matter content of about 33% is combined with the combustion of natural gas or biogas or in combination with both. 4. A method of producing saturated or superheated steam, characterized in that in a grate-fired boiler, wet grain stillage from bioethanol production with a dry matter content of about 33% in combination with the combustion of natural gas or biogas or in combination with both. 5. A method for obtaining fuel for boilers, characterized in that wet cereal stillage from bioethanol production with a dry matter content of up to 33% to be incinerated is taken directly from the centrifuge. 6. A method for obtaining fuel for boilers, characterized in that the wet grain stillage from bioethanol production with a dry matter content of up to 33% for combustion is a mixture of grain stillage from a centrifuge and syrup from an evaporator unit with a dry matter content of about 33%. 7. Boiler capacity, characterized in that the amount of steam produced in the boiler for burning either grain stillage from bioethanol production with a dry matter content of about 33% alone, or in combination with combustion of natural gas or biogas or both, will be after passing through a steam turbine to cover the entire heat consumption of the bioethanol distillery. 8. Combined heat and power generation by burning wet grain stillage in the form of a paste with a dry matter content of 30-33% in a specially designed fluidized bed steam boiler or special grate.