U.S. patent application number 13/379806 was filed with the patent office on 2012-07-05 for method and system for cleaning of and heat recovery from hot gases.
This patent application is currently assigned to DALL ENERGY HOLDING APS. Invention is credited to Jens Dall Bentzen.
Application Number | 20120167461 13/379806 |
Document ID | / |
Family ID | 41682470 |
Filed Date | 2012-07-05 |
United States Patent
Application |
20120167461 |
Kind Code |
A1 |
Bentzen; Jens Dall |
July 5, 2012 |
METHOD AND SYSTEM FOR CLEANING OF AND HEAT RECOVERY FROM HOT
GASES
Abstract
Exhaust gas, produced in a thermal reactor (1) that is fed with
solid fuel can be cooled and in a gas cooler (4) which produce a
condensate that is further cooled in a condensate cooler (7) which
produce energy. By using air moisturizing and particle separation
technology the exhaust gas and the excess condensate can be clean
and the energy efficiency of the plant can be increased. The method
can be used for a broad spectrum of fuels and conversion
technologies.
Inventors: |
Bentzen; Jens Dall;
(Birkerod, DK) |
Assignee: |
DALL ENERGY HOLDING APS
Birkerod
DK
|
Family ID: |
41682470 |
Appl. No.: |
13/379806 |
Filed: |
June 25, 2010 |
PCT Filed: |
June 25, 2010 |
PCT NO: |
PCT/DK2010/050164 |
371 Date: |
February 7, 2012 |
Current U.S.
Class: |
48/61 ;
48/197R |
Current CPC
Class: |
C10K 1/06 20130101; F23J
15/022 20130101; C10J 2300/0973 20130101; C10K 1/02 20130101; F23J
15/04 20130101; B01D 2247/04 20130101; C10J 2300/0976 20130101;
C10J 3/86 20130101; C10K 1/101 20130101; F23J 2219/70 20130101;
Y02E 20/30 20130101; Y02P 20/124 20151101; Y02P 70/10 20151101;
C10J 2300/0956 20130101; F01K 13/00 20130101; Y02E 20/363 20130101;
Y02P 20/50 20151101; C10J 2300/169 20130101; F23J 15/06 20130101;
F22B 37/008 20130101; B01D 47/00 20130101; Y02P 20/57 20151101;
C10J 3/84 20130101; C10J 2300/1884 20130101; Y02P 20/10 20151101;
F23J 15/027 20130101; Y02P 70/34 20151101; F23J 2219/40
20130101 |
Class at
Publication: |
48/61 ;
48/197.R |
International
Class: |
C10J 3/48 20060101
C10J003/48 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 26, 2009 |
DK |
PA 2009 00795 |
Claims
1. A thermal plant comprising a thermal reactor in which a chemical
process takes place during which process solid fuels reacts with
oxygen to produce an exhaust gas comprising hot flue gas and/or a
burnable gas a gas cooler cooling the exhaust gas to a temperature
below the dew point of the water present in the exhaust gas thereby
producing a condensate; an exhaust gas heat exchanger arranged
upstream of the gas cooler for extracting heat from the exhaust
gas, a condensate cooler cooling the condensate to extract energy
from the condensate wherein the thermal plant further comprises a
particle separation system for separating particles from a stream
of particles, said particles being produced in a thermal reactor,
the stream of particles is the water condensate produced from the
exhaust gas from the thermal reactor, the particle separation
system being adapted to produce a first stream of water having a
first content of particles, the first stream is produced
continuously or batch-wise, a second stream of water having a
second content of particles, wherein the ratio between the second
stream of water and the first stream of water when measured in m3/h
is larger than 5, the content (kg/m3) of particles in the first
stream is larger than the content (kg/m3) of particles in the
second stream of water, the condensate cooler being arranged to
cool the condensate of the second stream of water and, wherein the
plant further comprises: a feeding means provided for feeding at
least fraction of the first stream of water to ash produced in a
thermal reactor, to a fuel for a thermal reactor, to a filter
and/or to a disposal output.
2-23. (canceled)
24. The thermal plant according to claim 1, wherein the stream of
particles is a water condensate produced from the exhaust gas from
a thermal reactor and wherein the separation system comprises a
hydro cyclone.
25. The thermal plant according to claim 1, further comprising a
connection leading at least a fraction of the second stream of
water to a moisturizing system moisturizing air used in the thermal
reactor of the thermal plant.
26. The thermal plant according to claim 1, wherein 10% or more of
the first stream of water is fed to the fuel.
27. The thermal plant according to claim 1, wherein 10% or more of
the first stream of water is fed to the ash.
28. The thermal plant according to claim 1, wherein the first
stream of water is divided into two streams one being fed to ash
and one being fed to fuel.
29. The thermal plant according to claim 1, further comprising a
recirculation loop for recirculating the second stream of water
produced by the particle separation system back to the particle
separation system.
30. The thermal plant according to claim 29, wherein the
recirculation loop comprises a filter for filtering out from the
second stream of water a third stream of water having a smaller
content of particles (kg/m3) than the second stream of water.
31. The thermal plant according to claim 29, wherein the
recirculation loop comprises a heat exchanger for cooling the
second stream of water.
32. The thermal plant according to claim 29, wherein the
recirculation loop comprises a connection for feeding a fraction of
the second stream of water to a air moisturizing system for
moisturizing air to be used in a thermal reactor.
33. The thermal plant according to claim 32, wherein the connection
for feeding a fraction of the second stream of water to an air
moisturizing system is arranged downstream of the heat
exchanger.
34. The thermal plant according to claim 32, wherein the connection
for feeding a fraction of the second stream of water to an air
moisturizing system is arranged upstream of the heat exchanger.
35. A thermal plant comprising: a thermal reactor in which a
chemical process takes place during which process solid fuels
reacts with oxygen to produce an exhaust gas comprising hot flue
gas and/or a burnable gas a gas cooler cooling the exhaust gas to a
temperature below the dew point of the water present in the exhaust
gas thereby producing a condensate; a condensate cooler cooling the
condensate to extract energy from the condensate an air moisturizer
being adapted to produce a first and a second stream of moisturized
air, wherein the first stream of moisturised air has a higher
absolute water content, measured in kg H2O per m3 dry air, than the
water content of the second stream of moisturised air, and the
first stream of moisturised air is introduced into a thermal
reactor and used in the chemical reactions in the fuel, and the
second stream of moisturised air is introduced into a thermal
reactor and used in chemical reactions in gasses produced by
heating a fuel.
36. The thermal plant according to claim 35, wherein the water
content in the first stream of moisturized air is at least larger
than 50% than the water content in the second stream of moisturized
air.
37. The thermal plant according to claim 35, wherein the amount (kg
dry air) of the first stream of moisturized air is smaller than the
amount (kg dry air) of second stream of moisturized air.
38. The thermal plant according to claim 35, wherein the air
moisturizer comprises two air scrubbers.
39. The thermal plant according to claim 38, wherein two air
scrubbers are arranged in series; the first stream of moisturized
air is a fraction of moisturized air leaving a first air scrubber
and the remaining fraction of the moisturized air is feed into a
second air scrubber for further moisturization so as to provide the
second stream of moisturized air.
40. The thermal plant according to claim 38, wherein two air
scrubbers are arranged in parallel receiving air to be moisturized
from the same air source and, wherein the first and second streams
of moisturized air each are produced by one air scrubber only.
41. The thermal plant according to claim 35, wherein the air
moisturizer is arranged to cool gas produced in a thermal reactor
by utilizing at least the second stream of moisturized air.
42. The thermal plant according claim 35, wherein the thermal plant
comprises: a thermal reactor in which a chemical process takes
place during which process solid fuels reacts with oxygen to
produce an exhaust gas comprising hot flue gas and/or a burnable
gas a gas cooler cooling the exhaust gas to a temperature below the
dew point of the water present in the exhaust gas thereby producing
a condensate; an exhaust gas heat exchanger arranged upstream of
the gas cooler for extracting heat from the exhaust gas, a
condensate cooler cooling the condensate to extract energy from the
condensate wherein the thermal plant further comprises a particle
separation system for separating particles from a stream of
particles, said particles being produced in a thermal reactor, the
stream of particles is the water condensate produced from the
exhaust gas from the thermal reactor, the particle separation
system being adapted to produce a first stream of water having a
first content of particles, the first stream is produced
continuously or batch-wise, a second stream of water having a
second content of particles, wherein the ratio between the second
stream of water and the first stream of water when measured in m3/h
is larger than 5, the content (kg/m3) of particles in the first
stream is larger than the content (kg/m3) of particles in the
second stream of water, the condensate cooler being arranged to
cool the condensate of the second stream of water and, wherein the
plant further comprises: a feeding means provided for feeding at
least fraction of the first stream of water to ash produced in a
thermal reactor, to a fuel for a thermal reactor, to a filter
and/or to a disposal output.
43. A thermal plant comprising: a thermal reactor in which a
chemical process takes place during which process solid fuels
reacts with oxygen to produce an exhaust gas comprising a burnable
gas a gasification system for gasification of fuels, the
gasification system comprising a thermal reactor producing a
burnable gas, a gas cooler cooling the produced burnable gas to a
temperature below the dew point of the water present in the gas
thereby producing a water condensate by condensing water vapor
present in the produced burnable gas, a condensate cooler cooling
the condensate to extract energy from the condensate, a
moisturizing system adapted to moisturize air to be used in the
thermal reactor during conversion of fuel into a burnable gas,
feeding the moisturized air into the thermal reactor, and,
preferably, for cooling the condensate further in relation to the
cooling performed by the condensate cooler, and feeding the cooled
condensate to the gas cooler.
44. A thermal plant according to claim 43, wherein the thermal
plant comprises: a thermal reactor in which a chemical process
takes place during which process solid fuels reacts with oxygen to
produce an exhaust gas comprising hot flue gas and/or a burnable
gas a gas cooler cooling the exhaust gas to a temperature below the
dew point of the water present in the exhaust gas thereby producing
a condensate; an exhaust gas heat exchanger arranged upstream of
the gas cooler for extracting heat from the exhaust gas, a
condensate cooler cooling the condensate to extract energy from the
condensate wherein the thermal plant further comprises a particle
separation system for separating particles from a stream of
particles, said particles being produced in a thermal reactor, the
stream of particles is the water condensate produced from the
exhaust gas from the thermal reactor, the particle separation
system being adapted to produce a first stream of water having a
first content of particles, the first stream is produced
continuously or batch-wise, a second stream of water having a
second content of particles, wherein the ratio between the second
stream of water and the first stream of water when measured in m3/h
is larger than 5, the content (kg/m3) of particles in the first
stream is larger than the content (kg/m3) of particles in the
second stream of water, the condensate cooler being arranged to
cool the condensate of the second stream of water and, wherein the
plant further comprises: a feeding means provided for feeding at
least fraction of the first stream of water to ash produced in a
thermal reactor, to a fuel for a thermal reactor, to a filter
and/or to a disposal output, such as a sewer, a chemical treatment
facility and/or to the thermal reactor.
45. A method for cooling produced gas from a solid fuel gasifier
and for moisturizing the air for the gasifier, the gasifier being
of a thermal plant comprising: a thermal reactor in which a
chemical process takes place during which process solid fuels
reacts with oxygen to produce an exhaust gas comprising hot flue
gas and/or a burnable gas a gas cooler cooling the exhaust gas to a
temperature below the dew point of the water present in the exhaust
gas thereby producing a condensate; an exhaust gas heat exchanger
arranged upstream of the gas cooler for extracting heat from the
exhaust gas, a condensate cooler cooling the condensate to extract
energy from the condensate wherein the thermal plant further
comprises a particle separation system for separating particles
from a stream of particles, said particles being produced in a
thermal reactor, the stream of particles is the water condensate
produced from the exhaust gas from the thermal reactor, the
particle separation system being adapted to produce a first stream
of water having a first content of particles, the first stream is
produced continuously or batch-wise, a second stream of water
having a second content of particles, wherein the ratio between the
second stream of water and the first stream of water when measured
in m3/h is larger than 5, the content (kg/m3) of particles in the
first stream is larger than the content (kg/m3) of particles in the
second stream of water, the condensate cooler being arranged to
cool the condensate of the second stream of water and, wherein the
plant further comprises: feeding means provided for feeding at
least fraction of the first stream of water to ash produced in a
thermal reactor, to a fuel for a thermal reactor, to a filter
and/or to a disposal output, such as a sewer, a chemical treatment
facility and/or to the thermal reactor. the method comprising
feeding gas from the gasifier through a gas cooling system supplied
with cold water from the air moisturiser, and feeding the
gasification air through an air moisturiser supplied with warm
water from a gas cooling system.
Description
[0001] This invention relates inter alia to a method and a system
for cleaning of and heat recovery from hot gases, e.g. flue gas,
produced in a thermal reactor, or--more specific--using water to
cool and clean gases, released by thermal conversion (gasification
or combustion) of fuels e.g. biomass, waste, coal, oils, gases or
mixtures of these, by having three process steps: [0002] Removal of
contaminants (particles, salts, acids etc.) from gas in a water
based scrubber; [0003] Removal of contaminants of the scrubber
water by use of centrifuges and/or hydro cyclones; [0004] Heat
recovery of the energy obtained in the scrubber water.
[0005] Furthermore, the invention relates to methods and systems
for [0006] Moisturizing the air for a thermal reactor in two
moisturisers [0007] Removal of particles in the scrubber water
[0008] Recirculation of particles from the scrubber to the fuel
system.
[0009] In an overall perspective, the invention may be seen as
relating to handle particles in water which particles originates
from e.g. a flue gas and has due to condensation of water vapours
in the gas which occur when the gas is cooled to below the water
dew point of the gas. Such approach contains the particles in water
but leads to considerations as to how to dispose the water. The
present invention seeks to at least mitigate these problems in
particularly in relation to a desire that the water needs to be
cleaned before being discharged.
[0010] Further the invention may be seen as relating to converting
solid fuel into gas by moisturizing the air/oxygen used in then
thermal reactor as by moisturing the air slagging of ash and
formation of NOx is reduced.
BACKGROUND OF THE INVENTION
[0011] The present invention relates in certain aspect to systems
and methods to make a clean gas by use of simple and cheap
scrubbers and cyclones, and further to recover energy from the hot
gas in a very efficient way.
[0012] Moisturising of air is known from e.g. PCT/DK2006/050049
disclosing that heat can be recovered from hot gas produced in a
thermal reactor by injecting water into the gas at one or more
injection zones in such an amount and in such a way that the gas
temperature due to water evaporation is reduced to below
400.degree. C., preferably below 300.degree. C., possibly below
150-200.degree. C., and the gas dew point becomes at least
60.degree. C., preferably at least 70.degree. C., possibly 80 or
85.degree. C. The gas can then be led through a condensing heat
exchanger unit, where at least some of the gas contents of water
vapour are condensed, and the condensing heat can be utilized for
heating of a stream of fluid, mainly water.
[0013] Furthermore, U.S. Pat. No. 4036606 A discloses a method and
apparatus for cleaning gases, especially those generated by the
pressurized gasification of coal, to remove impurities therefrom,
especially tar, dust and salts, in which the gases are washed with
a liquid, preferably water, in a scrubbing unit and the wash liquid
is cleaned to yield a major clean liquid stream which is recycled
by a circulating means to the scrubbing unit and a minor impurities
concentrate stream from which the impurities are removed, in a
separator unit. Preferably the wash liquid is cleaned using a
plurality of hydrocyclones which may be arranged in series or in
parallel. Optionally the liquid recovered from the impurities
concentrate stream is returned to the scrubbing unit, although if
the quantity of this liquid is equal to the quantity of liquid
required for the de-salting of the wash liquid, no recovered liquid
is returned to the scrubbing unit.
[0014] In addition WO 2008/004070 A1 discloses a method of
controlling an apparatus for generating electric power and
apparatus for use in said method, the apparatus comprising a
gasifier for biomass material, such as waste, wood chips, straw,
etc., sais gasifier being of the shaft and updraft fized bed type,
which from the top is charged with the raw material for
gasification and into the bottom of which gasifying agent is
introduced, and a gas engine driving an electrical generator for
producing electrical power, sais gas engine being driven by the
fuel gas from the gasifier. By supplying the produced fuel gas
directly from the gasifier to the gas engine and controlling the
production of the fuel gas in the gasifier in order to maintain a
constant electrical output power, the necessity of using a gas
holder between the gasifier and the gas engine is avoided.
THE INVENTION, DEFINITIONS AND ELABORATIONS
[0015] The present invention references and makes use of a number
of units, methods, concepts and the like. Although these are
believed to have been used in a manner being ordinary to a skilled
person, some of those are elaborated below.
[0016] Stream of particles is preferably used to mean a flow of
particles. A stream of particles comprise typically but not
exclusively a mix of a fluid (gas or liquid) and particles
typically being solid particles and the fluid may in such cases be
seen as a fluid carrying the particles along. Examples of streams
of particles are a water condensate containing particles and
produced e.g. from exhaust gas in which cases the fluid is on
liquid phase or an exhaust gas containing particles in which case
the fluid is on gas phase.
[0017] Stream of water is typically used to mean a flow of liquid
water. The stream of water may contain other constituents than H2O
and even contain particles.
[0018] Stream of moisturised air is typically used to mean a flow
of air or oxygen in gas phase that has being moisturised. The
stream of moisturised air may contain other constituents than air,
oxygen and water and even contain particles.
[0019] Condensate cooler is typically used to mean a device being
adapted to extract energy from a condensate produced by a gas
cooler. Examples of condensate coolers applicable in connection
with the present invention are heat exchangers such as shell and
tube or plate heat exchangers. In some cases can the gas cooler and
the condensate cooler be integrated in one unit, where a warm dry
gas enter the cooler and a cool gas and a condensate exit the
cooler.
[0020] Particle separator may be referred to as a particle
separation system and vice versa. Particle separation system in its
broadest scope is used to indicate that a particle separator may
comprises a number of elements at different positions in a
plant.
[0021] Particles such as solid particles and water-soluble
particles are transferred from the gas to the water condensate
while the gas is cooled below the water dew point. In the particle
separation system two fraction of water condensate are produced:
One water fraction with a high load of particles and one water
fraction with a lower load. The particle separation system can be
integrated in one reactor such as the bottom of a scrubber with
condensate, where the high load particle stream is collected by
gravity in the bottom of the scrubber and the lower load particle
stream leave the scrubber at a higher level.
[0022] The particle separation system can also consist of several
reactors, such as a quench which have a high load of particles in
the exit water, followed by a scrubber which have low load of
particles in the exit water.
[0023] Also separation devises such as hydrocyclones, filters etc.
can be used to separate the particle load into a dirty and a clean
stream of water.
[0024] The dirty stream of water, can be added to the fuel, or it
can be used to moisturize the ash or can be cleaned somewhere. The
cleaner stream of water can be used for energy purpose such as
cooled in a heat exchanger and/or used for moisturizing air for the
thermal reactor.
[0025] Energy plants: Energy plants provide electricity, steam, hot
water, cooling for domestic and industrial purposes.
[0026] District heating/Hot Water Systems: The hot water can be
used for heating purposes, e.g. in houses, apartment houses,
offices, in industries etc. and for domestic water. Installations
for such purposes are produced in very different sizes, approx. 1
kW-250 MW input effect.
[0027] The water is usually heated in a closed circuit and led to a
point of consumption, after which the water is returned to the heat
production unit after release of the thermal energy. When the water
leaves the production unit (supply), the water temperature usually
is 60-90.degree. C. The temperature of the water returning to the
heat-production unit after cooling at the consumer (return) is
about 30-50.degree. C.
[0028] With the technological development and the attention to
energy savings, there has been a tendency to reduce the supply and
return temperatures, as the heat loss from the distribution pipes
is reduced in that way.
[0029] the hot water can be produced close to the required
locations or be sent to the consumer via a district heating
network.
[0030] Thermal reactors for solid fuels: Energy plants are often
based on at thermal reactor (combustion or gasification) where fuel
is decomposed by reacting with oxygen and thus releasing a hot gas
containing N2, CO2 water vapours and in case of combustion O2.
[0031] Further smaller amounts of CO, NOx and other gases can be in
the hot gas. By use of solid fuels such as coal, wastes, biomass
etc. particles and other substances including alkali metals (Na,
Ka), Chlorine, Potassium, Silica etc. may be released with the hot
gas.
[0032] Two fractions of solids: Often the main amount of particles
is removed from the thermal reactor as bottom ash, and only a
smaller fraction is released with the hot gas. This fraction is
captured in a filter system, so energy plants using solid fuels
normally have at least two fractions of solids to get rid of:
Solids from thermal reactor and solids from filter system.
Different types of thermal reactors can be used. Most common is
moving-bed and Fluid-bed reactors.
[0033] Conversion of solids and volatiles: Most reactors are
originally designed for conversion of coal. Fresh solid fuel such
as biomass or wastes has very different properties compared to
coal. Especially the content of volatiles and water can be higher
in biomass and wastes. In coal, the volatile content is normally
below 30%, whereas for biomass and wastes the volatile content is
normally above 65% (dry ash free weight basis).
[0034] When the volatile content is high in a fuel the conversion
process is often divided into two: [0035] Conversion of the solids
[0036] Conversion of the gas (volatiles)
[0037] Air for thermal reactors for solid fuels: In a combustion
reactor air is often supplied different places: [0038] Air for
conversion of the solids is often named primary air [0039] Air for
conversion of the volatiles is named secondary and tertiary
air.
[0040] Some thermal reactors use moisturised air. Moisturised air
give certain advantages in the thermal reactor. For the solid
conversion moisturised air results in better gasification
properties: (Steam-Carbon reactions) and moisturised air lowers the
temperature and hereby prevents ash sintering. For gas combustion
moisturised air result in lower NOx and slagging as temperature is
reduced.
[0041] Gasifiers: A gasifier converts solid fuel into a gaseous
fuel, which can be used for chemicals and/or used in a power
machine such as internal combustion gas engine or turbines. In some
cases i.e. internal combustion engines, a cold gas is desired. The
colder the gas is the higher is the energy content pr. volume and
thus the more power can a given engine produce. The restriction to
cool the gas is normally: [0042] The temperature of the return
water of the district heating network [0043] Outdoor air, and in
this case the heat energy of the gas is wasted.
[0044] Fuel flexibility: The content and the composition of the ash
can be very different for coal and biomass/wastes. It is a wish of
many plant owners to be able to use various types of fuels. But
thermal reactors have restrictions on the type of fuel to be used.
These restrictions typically relate to: [0045] Particle size [0046]
Heating value of fuel [0047] Type and amount of inorganic
components.
[0048] Heating value of fuel: The heating value of the fuel is
strongly affected by the water content of the fuel, thus a specific
thermal reactor seldom can use both dry and wet fuel.
[0049] Gas cooler is typically used to reduce the temperature of
the gas. A gas cooler can be a dry gas cooler when cooling the gas
to a temperature above the water dew point, or the gas cooler can
be a wet gas cooler, when the gas is cooled to a temperature below
the dew point of water present in the gas. Examples of gas coolers
applicable in connection with the present invention are: Shell and
tube coolers, radiation coolers, evaporative coolers, quench,
scrubbers.
[0050] According to certain aspects of the invention, the hot gas
produced in the thermal reactor is cooled in one or several gas
coolers. When the gas contain water vapours and have a water dew
point above the exit temperature of the gas cooler, then
evaporative energy of the water vapours will heat up the gas
cooler. This heat can be transferred to e.g. district heating
water. In such cases the gas cooler will produce a condensate that
needs to be disposed.
[0051] Impurities such as particles, salts, etc. in the condensate
from a gas from a thermal production unit fired with solid fuel
will normally need to be removed before disposal into the
environment.
[0052] There are special material requirements to gas coolers with
condensation. Glasfiber, plastics, glass, high grade steels,
ceramics are typical suitable materials.
[0053] Gas cleaning: Due to environmental concern impurities of the
gas may or should be removed. Common cleaning technologies are:
[0054] Cyclones [0055] Bag house filter [0056] Electrostatic filter
[0057] Scrubber
[0058] Especially bag filters and electrostatic filters are very
effective towards particulate filtration, whereas cyclones and
scrubbers typically are less effective, but also normally
cheaper.
[0059] Scrubbers: It is well known, that hot gases can be cooled
from high temperatures (100.degree. C.-1000.degree. C.) to below
100.degree. C. by injection of water into the gas. Such systems are
normally called scrubbers.
[0060] It is also well known that the injected water will collect
(absorb) some of the pollutants, e.g. acids, particulates etc.,
from the hot gas. Some scrubbers are designed to have a high
efficiency regarding removal of contaminants.
[0061] It is well known that the cleaner the scrubber water is, the
more efficient is the scrubber as scrubber water with a high load
of contaminants can pollute the gas with contaminants from the
scrubber water. There are basically two possibilities of getting
clean water for the scrubber: [0062] Use fresh clean water [0063]
Reuse scrubber water that is cleaned before reuse.
[0064] The scrubber water circulating is normally not filtered or
cleaned in any way. In some cases the scrubber water can be
neutralised e.g. with NaOH or lime. Normally, only the excess
water, the produced condensate, is cleaned before it is
disposed.
[0065] When scrubber water is not regularly cleaned, the particle
and salt content may become rather high, and the scrubber water may
cause re-entrainment of contaminants into the gas.
[0066] Energy recovery of scrubber water: It is well known to
recover energy of the circulating scrubber water i.e. to pre heat
district heating water. When scrubber water is loaded with
particles the scrubber-district heating heat exchanger may have a
short lifetime as coarse particles erode the heat exchanger.
[0067] Quench: In some cases a quench is prior to the main
scrubber. Such a quench can be installed in order to protect the
following scrubber from too high temperatures. The water from the
quench is typically lead to the main scrubber and mixed with the
water herein.
[0068] Treatment of excess scrubber water: The flow of excess water
is a much smaller than the flow of the circulating scrubber water.
Excess water (condensate) is normally cleaned before disposal.
There are several methods known clean the excess scrubber water,
including: [0069] Gravity sedimentation operations [0070]
Filters
[0071] Separation technologies for high flow of water: From other
industries other water separation technologies are used. Such
technologies can be: [0072] Ceramic membrane filters [0073]
Hydrocyclones
[0074] Ceramic membrane filters: In a ceramic membrane filter a
high flow of water with contaminants is flowing through the
membrane. A small fraction of water is diffusing through the
membrane and thus leaves the filter cleaned. The particulates and
other impurities leave the filter with the main water flow. Such
"filter principle" is not used in condensing scrubbers, as
particles and other impurities are not separated from the
system.
[0075] Hydro cyclones: Hydro cyclones can be used to make a low
stream (about 5-20%) of particle loaded water fraction and a high
stream (80-95%) of cleaner water fraction. Hydro cyclones are not
used in condensing scrubbers as the water fractions with the high
particle load needs further filtration, and therefore are the
hydrocylone not cost efficient.
[0076] Emissions: Energy plants using solid fuels meet certain
emission regulations, which are constantly being tightened.
Typically particle emission, CO, NOx is regulated but also SO2,
Chlorine, Dioxine, Heavy metals, furans can be regulated. There are
different standards of measure emissions. In some particle emission
standards salts are measured as particle emission. i.e. Danish
standard MEL-02.
[0077] Air moisturisers: Air moisturisers can be used in connection
with condensing scrubbers. Air moisturisers result in several
advantages including higher energy out-put in condensing unit and
better combustion/gasification properties in the thermal reactor:
[0078] Better producer gas (H2 content) [0079] Slagging [0080]
Agglomeration [0081] NOx
DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS THEREOF
[0082] The present invention provides inter alia an improved method
and an improved system or installation for thermal conversion of
solid fuels into energy, hereof at least part of the energy as hot
water.
[0083] In a first aspect the present invention relates to a thermal
plant comprising [0084] a thermal reactor in which a chemical
process takes place during which process solid fuels reacts with
oxygen to produce an exhaust gas comprising hot flue gas and/or a
burnable gas [0085] a gas cooler cooling the exhaust gas to a
temperature below the dew point of the water present in the exhaust
gas thereby producing a condensate; [0086] a condensate cooler
cooling the condensate to extract energy from the condensate.
[0087] The present invention further relates inter alia to a
particle separation system of a a thermal plant according to the
invention into which particle separator a stream of fluid (gas
and/or liquid) which contain particles enters and where at least
two streams of water are produced with different amount of water,
where the stream with the smallest amount of water have the highest
load of particles.
[0088] The present invention further relates inter alia to an air
moisturizing system of a thermal plant according to the invention ,
the moisturising system being adapted to produce a first and a
second stream of moisturised air, wherein moisturise the first
stream of moisturised air has a higher absolute water content,
measured in kg H2O per m3 dry air, than the water content of the
second stream of moisturised air.
[0089] The present invention further relates inter alia to a
gasification system for gasification of fuels of a thermal plant
according to the invention, the gasification system comprising
[0090] a thermal reactor producing a burnable gas [0091] a gas
cooler cooling the produced burnable gas and producing a water
condensate by condensing water vapour present in the produced
burnable gas [0092] a condensate cooler cooling the condensate
[0093] a moisturising system adapted to [0094] moisturise air to be
used in the thermal reactor during conversion of fuel into a
burnable gas [0095] feeding the moisturised air into the thermal
reactor and, preferably for cooling the condensate further in
relation to the cooling performed by the condensate cooler; thereby
preferably providing a system being adapted to produce a cold and
burnable gas having a temperature being lower than the temperature
obtained if the air is not moisturised.
[0096] Please note, that in the present context the term air is
preferably used in the sense of atmospheric air and in general an
oxygen containing gas, and even a gas consisting mainly of oxygen
such 99.9%.
[0097] The invention may in some aspect and preferred embodiments
make use of number of device and some of such device and their use
is further disclosed in the following. Further embodiments and
aspects are presented in the claims as well.
[0098] Hydro Cyclone
[0099] In accordance with the present invention one or several
hydro cyclones may be placed upstream to the heat exchanger which
cools the condensate from the quench and/or the gas scrubber.
Hereby the lifetime of the heat exchanger will be extended
considerably and the cleaning efficiency of the scrubber will be
increased.
[0100] The collected particles may be lead to the ash and or to the
fuel and/or to somewhere else, e.g. a disposal site.
[0101] The Double Air Moisturisers
[0102] In accordance with the invention a double air moisturisers
may be used, preferably in a configuration where: [0103] a main air
moisturiser may be used for the main air flow and [0104] a booster
air moisturiser may used for a minor airflow.
[0105] When primary air for the solid fuel conversion is used as
gasification agent a high load of water vapours is a great
advantage in order to prevent slagging and in order to enhance H2
production in the gasifier.
[0106] Membrane Filters
[0107] In accordance with the invention a high flow membrane filter
may be used to clean the excess condensate produced in the system
before it is being disposed into the environment. The particles may
preferably be circulated to the ash and/or the fuel and/or disposed
other places.
[0108] Quench, Condensing Gas Cooler and Air Moisturiser
[0109] In accordance with the present invention a Quench with a
dirty water outlet, a condensing gas cooler with a clean warm water
outlet and an air moisturiser may advantageously be used.
[0110] The quench may collect the most particles, salts and acids.
The quench water may be disposed of the scrubber system to the
fuel/ash/other place.
[0111] The warm water of the condensing gas cooler may be cooled in
a heat exchanger which produces heat that can be utilised. The gas
will be cooled by cold water from an air moisturiser.
[0112] The present invention may provide clean water for the gas
cooler and air moisturiser and a clean cold gas of the gas
cooler.
[0113] The Air Moisturizing System Combined with a Gasifier
[0114] In accordance with the invention an air moisturizing system
may be connected to a gasification system. In this way the produced
gas will be cooled and thus have an increased heating value pr.
volume. This may result in a high power output of a power machine.
A further advantage with such system may be that moisturised air is
well suited for gasification process as steam-carbon reactions
produce hydrogen.
[0115] A further advantage of such system may be that the overall
system efficiency can be improved as more heat may be produced in
connection with the condensing gas cooler, as the gasification air
is moisturised.
[0116] Cheap, Simple and Compact
[0117] As indicated above, various aspects of the present invention
may offer a number of advantages compared to state-of-the-art
combustion technologies. It could therefore be expected that
various aspects of the invention will be expensive and complicated.
However, the simplicity and the compactness of the system may be
seen as a main advantage of the invention.
[0118] Pressure of System
[0119] Typically, the pressure in various components of the
invention may preferably be atmospheric pressure, although various
aspects of the invention may be designed for both pressures being
above and/or below atmospheric pressure.
[0120] Materials
[0121] Typically, various components of the invention such as the
thermal reactor may be built of high-temperature materials such as
bricks and insulation blocs inside, preferably comprising a steel
vessel with insulation on its outside.
[0122] Other parts of the components of the invention such as the
water treatment part and the gas coolers may be built of plastics,
glasfiber, glass, stainless steel.
[0123] In the following the present invention and particular
preferred embodiment thereof will be further disclosed in
connection with the accompanying drawings in which:
[0124] FIG. 1 shows a schematically an embodiment of a system for
cleaning of and heat recovery from hot gas.
[0125] FIG. 2 shows a similar embodiment to the one shown in FIG. 1
but where the gas cooler has been replaced with a particle
separator such as a scrubber.
[0126] FIG. 3a shows a more detailed overview over the embodiment
of an air moisturiser means.
[0127] FIG. 3b shows an embodiment wherein two moisturiser units
are serial connected to each other.
[0128] FIG. 3c shows a further embodiment wherein two moisturiser
units are parallel connected to each other having a common or
separate air or oxygen inlets.
[0129] FIG. 4 shows inter alia an embodiment of a preferable
particle separator in more details.
[0130] FIG. 5 shows a schematically overview over one of the
preferred embodiments where a thermal gasifier is used as a thermal
reactor.
[0131] FIG. 6 shows a full schematic overview over an embodiment of
the invention where the invented system for cleaning and heat
recovery is used.
[0132] FIG. 7 shows schematically a preferred embodiment of a plant
according to the present invention.
[0133] FIG. 8 shows a preferred embodiment according to the present
invention, including a venturi scrubber.
[0134] FIG. 9 shows a preferred embodiment according to the present
invention in which solid fuel is converted into energy.
[0135] FIG. 10 together with tables I and II shows energy balances
and gas compositions for embodiments of plants according to the
present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0136] In the figures, various elements are depicted by use of
dotted lines. The use of such dotted lines to indicate that the
element in question is optionally or it position is optionally.
[0137] FIG. 1 shows schematically an embodiment of a system for
cleaning of and heat recovery from hot gas. This embodiment
comprises a thermal reactor (1) wherein fuel is burned or gasified.
The thermal reactor (1) has one fuel inlet (2) connected to a fuel
feeder (not shown) and one or a plurality of air inlets (3) feeding
air or pure oxygen into the thermal reactor (1). If needed, the air
or oxygen could be moisturised by the air passing through an air
moisturiser connected before the air inlets (3) of the thermal
reactor (1). The exhaust gas from the thermal reactor (1) is led
through a channel from the thermal reactor (1) to a gas cooler (4).
An exhaust gas heat exchanger unit (5) could be, as an option,
connected to the channel between the outlet of the thermal reactor
and the inlet of the gas cooler (4). The gas cooler (4) receives
hot exhaust gas and delivers cooled exhaust gas to an optional heat
extracting means (6), typically being a heat exchanger and
condensate to a condensate cooler unit (7) which is adapted to
extract energy. The cooled condensate delivered from the condensate
cooler (7) may either be fed to a sewer or be re-used in the
process.
[0138] FIG. 2 shows a similar embodiment to the one shown in FIG. 1
but where the gas cooler (4) of FIG. 1 has been replaced with--or
is constituted by--a particle separator (8) such as scrubbers
and/or hydro cyclones. Hot exhaust gas from the thermal reactor (1)
is delivered to the inlet of the particle separator (8). The
particle separator (8) has at least two outlets (O1, O2) for
respectively a first stream (9) and a second stream (10) of water
with particles as will be disclosed further below. As indicated,
the system according to FIG. 2 comprises hydro cyclone and/or as
scrubbers and no flue gas leaves the hydro cyclone and/or
scrubbers.
[0139] One outlet (O1) is used for the first stream (9) to feed a
small amount of water with a high content of particles and salt
back to the thermal reactor (1). This first stream can be fed
either directly to the thermal reactor (1) or via one or a
plurality of air moisturiser(s) (not shown in FIG. 2). This first
stream (9) could also, if needed, be fed directly to a sewer. The
second stream (10) has a relatively larger water volume and
contains relatively fewer particles and has a relatively lower salt
concentration compared to the first stream (9). A filtering (11) is
connected to the second stream (10) as shown in FIG. 2 and has two
outlets, one that could be used, if needed, to tap highly cleaned
water out of the system and one that distributes the rest of the
second stream (10) to the particle separator (8). A variety of
optional elements may advantageously be applied to the second
stream (10) such as outlets to air moisturisers and/or heat
exchangers. The second stream (10) will be cooled while passing
through various elements to a phase and temperature suitable for
the particle separator (8). In FIG. 2, the condensate coolers are
indicated by dotted lines and numeral 7. It is indicated that a
condensate cooler (7) may be left out or arranged upstream or
downstream of the filter (11).
[0140] FIG. 3a shows a more detailed overview over the embodiment
of an air moisturiser (12) producing a 1st and a 2nd stream of
moisturised air. The air moisturiser (12) has a plurality of inlets
and outlets where at least one is an air inlet (13) and one is an
inlet delivering water (14) from either, depending on the
configuration, a gas cooler means or a particle separator's first
or second stream (9, 10). Depending on the configuration of the
preferred embodiment, the water may pass through a condensate
cooler (7) before entering the air moisturiser to recover energy of
the condensate and to obtain the right (in the sense of desired)
phase and temperature. The condensate cooler (7) may be left out as
indicated by the dotted line showing a connection from the particle
separator to the moisturiser (12).
[0141] FIG. 3b shows an embodiment wherein two moisturiser (12) are
serially connected to each other. Air or pure oxygen is delivered
to the first moisturiser (15) wherein the delivered air or oxygen
is moisturised using water or steam. Moisturised air or oxygen is
transferred from the first moisturiser means (15) into a channel
from which moisturised air or oxygen is extracted from to be
delivered as the 1st stream of moisturised air connected to a
thermal reactor (1). The remaining air or oxygen is delivered to a
second moisturiser (16) in which air or oxygen is further
moisturised using water or steam. An outlet from the second
moisturiser (16) delivers a 2nd stream of moisturised air or oxygen
to an inlet of the thermal reactor (1).
[0142] FIG. 3c shows a further embodiment wherein two moisturiser
means (12) are parallelly connected to each other having a common
air or oxygen intake point. Each moisturiser (17, 18) is
moisturizing air using water or steam and delivers moisturised air
or oxygen to separate air streams (1st and 2nd stream of
moisturised air) fed to the inlets on the thermal reactor (1).
[0143] FIG. 4 shows a preferred embodiment of a particle separator
(8) in more details. Here the particle separator is a part of a
scrubber (19) spraying the exhaust gas with clean re-used scrubber
water. The spraying could be done at one stage or at a plurality of
stages depending on the configuration. From the scrubber (19)
cleaned and cooled gas is delivered but also water will be
delivered using, in this configuration, two different outlets (O1,
O2). Outlet (O2) is supplying used and unclean water into the
second stream (10). The particle separation is established by
arranging the outlet (O2) above the bottom of the scrubber (19)
below the water surface in the scrubber (19) and by arranging the
outlet (O1) at the bottom of the scrubber (19). The separation is
due to a sedimentation of the particles in the water present in the
scrubber (19) resulting in that the concentration of particles in
the water increases towards the bottom of the scrubber (19).
Accordingly, the particle separator comprises the outlets (O1, O2)
arranged at two different levels relatively to the water surface in
the scrubber (19). Here the water will pass through a filtering
system (11) such as a membrane filter that could, if needed,
deliver very clean water into a third stream of water. Clean
filtered water will continue from the filtering means towards, in
this embodiment, a heat exchanger (20) that cools the water and
delivers energy before the water is re-used in the scrubber (19).
Some water could occasionally be extracted into the first stream
(9). It is noted that the filter (11) may left out (similarly for
e.g. FIG. 2).
[0144] FIG. 5 shows schematically an overview over one of the
preferred embodiments of the invention in which a thermal gasifier
(21) is used as a thermal reactor (1). The exhaust gas from the
thermal gasifier (21) is fed to unit (22) being a cooler and/or
filter and/or cyclone where the exhaust gas is cooled and some of
the particles are separated out. The unit (22) is downstream
connected with a particle separator such as a gas scrubber (23). In
the gas scrubber (23), the gas may be cooled and cleaned in one or
in a plurality of stages using water, hence leading to cold clean
gas leaving the system at position (24) in FIG. 5. The water used
to cool and clean the gas is collected at the bottom of the
scrubber (23) from where it is delivered to a unit (25), preferably
in the form of a cyclone, to be separated into a first and second
stream ? (9, 10) of water in the same way as previously described.
Accordingly, the particle separator in the embodiment of FIG. 5 is
the cyclone (25). A condensate cooler (7) is arranged in the second
stream of water.
[0145] The water of the second stream (10) will, after being
cleaned in the unit 25 and cooled, be used in the scrubber (23).
The water of the second stream could optionally also be used to
pre-cool the gas before the gas enters the scrubber for example by
using a quench (29). The water of the second stream (26) could
optionally also be used in an air moisturiser (27) that could be
connected to the thermal gasifier (21). The water collected at the
bottom of the air moisturiser (27) could optionally be used at a
second injection point (28) in the scrubber (23). All temperatures
stated in the schematically flow scheme of FIG. 5 are typically
temperatures in such a system but are not intended as limiting the
scope of the patent since other temperatures could be used
depending on the system.
[0146] FIG. 6 shows a full schematic overview over a preferred
embodiment of the invention where the invented system for cleaning
and heat recovery is used. In this embodiment a feed system
comprising a fuel storage (30) and a fuel feeder (31) is feeding
fuel to a thermal reactor (1) comprising a furnace (32). To the
furnace (32) are two inlets connected feeding moisturised air or
oxygen to the furnace (32). The moisturised air is distributed both
at the bottom (33) of the furnace and above the point of fuel
feeding (34). At the bottom of the furnace is an outlet (44) for
taking out ash into for example a forest, fields or to deposits.
The moisturised air or oxygen comes from a moisturizing system
comprising two air moisturisers (35, 36), working using the same
principles as a scrubber. These two air moisturisers (35, 36) are
serially connected. Here the main moisturiser (35) distributes
moisturised air both to the air inlet (34) above the feeding inlet
at the furnace (32) and to an air moisturizing booster (36) which
further moisturises the air before being injected at a position in
the bottom (33) of the furnace (32).
[0147] Thus, the temperature of the fuel in the thermal reactor is
reduced and hereby production of slagging and NOx is reduced and
the temperature of the gas combustion is reduced hereby thermal NOx
formation is reduced. Air or oxygen is fed into the main
moisturiser (35) at position (35a).
[0148] Hot exhaust gas created in the furnace (32) will go through
a heat exchanger (37) that is connected to an energy extraction
device (38) which could produce both or either of electric energy
and energy for district heating. The hot gas will then continue
into the scrubber system where it first enters the quench (39)
where water from the air moisturiser booster (36) is used to cool
down the exhaust gas before entering the scrubber (40). The
remaining part of the scrubber water will be collected together
with particles and salts at the bottom of the quench (39). These
particles will be sent back to the fuel storage (30) to be feed
back into the thermal reactor and leave the thermal reactor as
bottom ash.
[0149] The cooled and cleaner exhaust gas will then continue into
the scrubber (40) where water will added to the gas at two
different positions thus cooling the gas. At the first position
(41) it is with water from the air moisturiser booster (36) and
condensate from the condensate cooler (46) and at the second
position (42) it is with colder water from the main air moisturiser
(35). The clean and cooled gas will then be fed to a chimney
(45).
[0150] As described above, the exit of the quench (39) is a dirty
small stream (first stream of water) and the exit of the scrubber
(40) is a cleaner and larger stream (second stream of water).
[0151] The second stream of water from the scrubber (40) is split
into a smaller stream going to the booster moisturised (36) and a
larger stream going into the heat exchanger (46) for extracting
energy which can be used for district heater. Water exiting the
booster moisturizer 36) is mixed with water from the heat exchanger
46 in point (47). This stream is downstream divided into a stream
going to the main air moisturiser from after which it is filtered
in (43) and fed back to the scrubber (40) at position 42, and two
streams: one feeding water into the quench (39) and one feeding
water into the scrubber (40) at position (41).
[0152] In FIG. 7, the particle separation is performed by the
quench with hydro cyclone and the scrubber in combination. The
hydrocyclone delivers the first stream of water (indicated by "High
amounts of salts . . . Small amount of water . . . " in FIG. 7).
The second stream of water is extracted upstream of the condensate
cooler (7) (indicated by "Small amounts of Salts . . . High amounts
of water" in FIG. 7)
[0153] FIG. 7 shows schematically a thermal reactor that is
supplied with fuel, air or oxygen and/or water and/or steam. The
hot gases are transported in a channel to the scrubber. One or
several components may advantageously be arranged between the
thermal reactor and the scrubber, e.g. heat exchangers, filters,
cyclones, inlet for moisturising agent, such as water, water
collecting device etc. One or several agents, such as lime,
activated carbon etc., may advantageously be added to the dry gas
before the scrubber. In connection with the embodiment shown in
FIG. 7 and the invention in general, the following measures may
advantageously be invoked: [0154] The scrubber is preferably
oriented vertically, but may also be horizontal or with oblique
orientation. [0155] One or several agents, such as NaOH, lime,
activated carbon etc. may advantageously be added to the scrubber
water. [0156] One or more hydrocyclones or centrifuges, in which
the scrubber water is separated into two streams, may be included
to provide: A dirty stream, containing most particles, and a clean
stream. [0157] The clean stream is led to a heat exchanger, in
which the scrubber water is cooled. [0158] The cooled and cleaned
scrubber water is used in the scrubber to clean and cool the gas.
[0159] Excess water can be removed in a droplet separator before
the gas is led to the atmosphere or used in a process.
[0160] FIG. 8 shows a preferred embodiment according to the present
invention including a venture scrubber.
[0161] FIG. 9 shows a preferred embodiment according to the present
invention in which solid fuel is converted into energy in a clean
and efficient system. A condensate cooler is indicated by numeral
(7). The system comprising inter alia a feeder and thermal reactor,
which components have been disclosed in further details herein and
some, further, disclosures to some of the components that may be
applicable to this and other aspects and embodiment of the present
invention are presented below:
[0162] Feeder and Thermal Reactor
[0163] In the bottom part, the solid fuel is converted into a
burnable gas and fine ash. The solid conversion is an updraft
gasification process: In the top layer, the fuel is dried and
devolatized (pyrolysis). In the lower part, moisturised air from
the booster air moisturiser is reacting with the carbon in a
gasification process. By having a high moist content in the air the
tendency of slagging is reduced and hereby the thermal reactor may
use various types of fuel, including low cost ash rich fuels.
[0164] Gas from gasification zone is combusted in the top section.
The gas combustion (flow, temperatures, emissions etc) is very
stable. This is due to the operating concept of the oven.
[0165] The design is based on fuel with a low heating value
resulting in an adiabatic temperature of 1000-1150.degree. C., with
an oxygen content in the flue gas of 4-7% (dry basis).
[0166] When the heating value increases, condensate preferably from
a low temperature cooler, may be added to the fuel.
[0167] High Temperature Cooling
[0168] A high temperature cooler, when present, may cool to
200.degree. C.-600.degree. C., preferably 300.degree. C.
-400.degree. C. Thereby the cooler may become very compact and low
temperature corrosion may be avoided. Due to the water addition to
the fuel the steam content of the gas is high and therefore the gas
has good radiation properties, which contribute to a compact
design.
[0169] Use of Heat from a High Temperature Cooler
[0170] A high temperature cooler can produce hot water, steam or
thermal oil. Several products may possible be produced by the high
temperature cooler including: [0171] Power by using an ORC (Organic
rankine cycle) system which could be driven by thermal oil or hot
water, by using a steam turbine or steam engine, stirling engines
or other [0172] Cooling by using absorption chillers [0173] Clean
water by de-salting water [0174] Steam for industrial or heating
purposes
[0175] Quench
[0176] In a quench the gas is cooled by water injection preferably
to below 100.degree. C. and particles, salts, acids etc. is
collected in the bottom. The amount of water to the quench is
regulated by the temperature of the furnace as the water from the
bottom of the quench is used to regulate the temperature of the
furnace. As particles and salts of the quench and the rest of the
scrubber system are collected here and send to the fuel, then there
is no particle outlet of the scrubber system. All particles leave
the system as bottom ash from the thermal reactor.
[0177] Two Stage Flue Gas Scrubber
[0178] Preferably a system may comprise two packed bed scrubbers
enclosed in a single vessel, where the flue gas is preliminary
dehumidified and cooled in the lower section and finally further
dehumidified and cooled in the upper section.
[0179] High Temperature Flue Gas Cooling
[0180] A nominal flue gas flow is slightly above 1 kg/s (dry gas
flow rate) at 78.degree. C. fully saturated. The flue gas may be
treated with counter flow cooler water entering at 50.degree. C. in
the packed bed having a diameter of 1200 mm and a height of 1400 mm
and the water is distributed from a grid of nozzles located above
the packing. The packing used is 25 mm propylene PALL RINGS
(HOSTALEN PPH material).
[0181] The cool water may be obtained from a air moisturiser
booster and the water exit of a Low Temperature Flue Gas Scrubber
located at the top of the assembly. The hot water discharge is
transferred to an air moisturiser booster.
[0182] A High Temperature Flue Gas scrubber is anticipated to
operate essentially linearly for capacities down to about 10%
nominal capacity and the gas side pressure drop closely approximate
a square root law.
[0183] Low Temperature Flue Gas Cooling
[0184] The preliminary cooled flue gas is further cooled and
dehumidified in counter flow with water supplied from the Main Air
Moisturiser discharge in a packed bed having a diameter of 1200 mm
and a height of 1200 mm. The water is distributed from a grid of 26
nozzles located above the packing. The packing used is 25 mm
propylene PALL RINGS (HOSTALEN PPH material). To limit entrained
water mist a droplet separator (200 mm demister pad) is placed
above the water distributor.
[0185] The Low Temperature Flue Gas scrubber is anticipated to
operate essentially linearly for capacities down to about 10%
nominal capacity and the air side pressure drop closely approximate
a square root law.
[0186] Air Moisturisers In order to provide the primary air with a
high load of water vapors to the thermal reactor a double air
moisturiser system is utilised.
[0187] Main Air Moisturiser
[0188] The nominal total air requirement is 1 kg/s (dry air flow
rate) at 20.degree. C. The air is treated with counter flow water
entering at 50.degree. C. in packed bed having a diameter of 1200
mm and a height of 1800 mm and the water is distributed from a grid
of 21 nozzles located above the packing. The packing used is 16 mm
propylene PALL RINGS (HOSTALEN PPH material). To limit entrained
water mist a droplet separator (100 mm demister pad) is placed
above the water distributor.
[0189] The hot water is obtained from the flue gas scrubber and the
cool water discharge is transferred for final flue gas cooling in
that scrubber with a part discharged to the drain.
[0190] The main air moisturiser is anticipated to operate
essentially linearly for capacities down to about 10% nominal
capacity and the air side pressure drop closely approximate a
square root law.
[0191] Air Moisturiser Booster
[0192] About 20% of the moisturised air from the main scrubber is
further moisturised in the booster scrubber for use as primary
combustion air--or gasification agent--while the remaining air is
used as secondary air in the furnace for burning the combustible
gases from the integrated updraft gasifier. The air is treated with
counter flow water entering at 67.degree. C. in packed bed having a
diameter of 600 mm and a height of 1800 mm and the water is
distributed from a grid of 9 nozzles located above the packing. The
packing used is 16 mm propylene PALL RINGS (HOSTALEN PPH material).
To limit entrained water mist a droplet separator (100 mm demister
pad) is placed above the water distributor.
[0193] The hot water is obtained from the high temperature part of
the flue gas scrubber and the cool water discharge at 50.degree. C.
is transferred for initial (high temperature) flue gas cooling in
that scrubber and also in the main moisturiser.
[0194] The booster air moisturiser is anticipated to operate
essentially linearly for capacities down to about 10% nominal
capacity and the air side pressure drop closely approximate a
square root law.
[0195] Water System
[0196] As described above, the water system for the moisturizing
scrubbers is closely coupled to the flue gas cooling and
dehumidification system. [0197] The (25.degree. C.) cool exit water
from the main air moisturiser is used partly for the final cooling
of the flue gas and partly discharged to the drain as excess
condensate. [0198] The (50.degree. C.) cool exit water from the
booster air moisturiser is used partly for the initial cooling of
the flue gas and partly for the water supply to the main air
moisturiser.
[0199] Therefore, both moisturisers are equipped with pumps
(nominal 5,5 m.sup.3/h for the main scrubber pump and 3,3 m.sup.3/h
for the booster scrubber pump).
[0200] Cleaning of Produced Condensate and Removal of Particles
[0201] Due to the effective cooling of the flue gas the system
produce a condensate that shall be disposed. The condensate that
circulates between the flue gas scrubber and the air moisturisers
is relatively clean, due to the pre-cleaning in the quench, but not
necessarily being clean enough to be disposed. A membrane filter is
placed on the scrubber water circuit in which about 5-15% of the
water is cleaned over the filter and disposed, while the rest of
the water and the particles is circulated to flue gas scrubber,
thereafter to the air moisturiser, thereafter to the quench and
thereafter to the fuel and hereby are the particles removed from
the system.
[0202] A number of measures may in accordance with the present
invention be included in various aspect and embodiments of the
invention. Many of these are disclosed above and some are presented
in the listing below: [0203] A chemical agent may be added to the
scrubber water to increase the efficiency of the hydrocyclone.
[0204] A chemical agent may be added to the scrubber water to
increase the efficiency of removal of contaminants of the gas.
[0205] Energy from the heat exchanger may advantageously be used
for district heating. [0206] The process is preferably operated so
that the temperature of the gas before the scrubber is preferably
more that 200.degree. C. [0207] At least one hydro cyclone and/or
one or more centrifuges may preferably be arranged upstream the
heat exchanger. [0208] A preferred embodiment of a system for
cooling and cleaning gases, may advantageously comprise [0209] a
thermal reactor which converts solid fuel into a hot gas [0210] an
inlet duct for the gas to at least one scrubber [0211] at least one
pump to circulate the scrubber water [0212] at least one hydro
cyclone and/or a centrifuge [0213] at least one heat exchanger that
cools the scrubber water.
[0214] Such a system may preferably comprise means [0215] for
controlling the pH level of the scrubber water [0216] for adding a
chemical agent to the scrubber water so the particles will
agglomerate and/or [0217] for adding a chemical agent to the gas to
remove contaminants of the gas.
[0218] Finally, FIG. 10 together with the below tables I and II
shows energy balances and gas compositions for preferred
embodiments of a plant according to the present invention. Gas
compositions pertaining to fuel moistures other than shown in table
I and II may be estimated by interpolation/extrapolation. It is
noted that FIG. 10 correspond to the embodiment shown in FIG. 6.
Reference signs used in FIG. 10 refers to tables I and II.
TABLE-US-00001 TABLE I Fuel Moisture 53% 50% 40% 30% 20% 10% WATER
SYSTEM ('C.) (kg/s) ('C.) (kg/s) ('C.) (kg/s) ('C.) (kg/s) ('C.)
(kg/s) ('C.) (kg/s) Flue Gas Quencher W7 INLET 49.0 0.2417 49.0
0.2488 49.0 0.2660 49.0 0.2765 49.0 0.2829 49.0 0.2869 W4 EXIT 79.8
0.0000 79.3 0.0068 78.2 0.0233 77.3 0.0330 76.5 0.0388 75.9 0.0421
Warm Flue Scrubber W8 INLET 49.0 8.0766 49.0 7.9722 49.0 7.6807
49.0 7.4552 49.0 7.2751 49.0 7.1283 NN FROM ABOVE 49.0 1.4594 49.0
1.5029 49.0 1.6216 49.0 1.7098 49.0 1.7777 49.0 1.8312 W7 TO
QUENCHER 49.0 0.2417 49.0 0.2488 49.0 0.2660 49.0 0.2765 49.0
0.2829 49.0 0.2869 W3 EXIT 76.8 9.7427 76.3 9.6642 75.2 9.4457 74.3
9.2760 73.5 9.1403 72.9 9.0291 Cool Flue Scrubber W12 INLET 23.0
1.4022 23.0 1.4440 23.0 1.5582 23.0 1.6429 23.0 1.7082 23.0 1.7596
NN TO BELOW 49.0 1.4594 49.0 1.5029 49.0 1.6216 49.0 1.7098 49.0
1.7777 49.0 1.8312 Warm Air Scrubber W13 INLET 76.8 0.6644 76.3
0.6851 75.2 0.7463 74.3 0.7979 73.5 0.8419 72.9 0.8800 W2 EXIT 49.0
0.6368 49.0 0.6570 49.0 0.7170 49.0 0.7677 49.0 0.8110 49.0 0.8485
Cool Air Scrubber W2 FROM BOOSTER 49.0 0.6368 49.0 0.6570 49.0
0.7170 49.0 0.7677 49.0 0.8110 49.0 0.8485 W9 FROM MAIN 49.0 1.0016
49.0 1.0072 49.0 1.0186 49.0 1.0229 49.0 1.0232 49.0 1.0210 W1 EXIT
23.0 1.5794 23.0 1.6043 23.0 1.6732 23.0 1.7261 23.0 1.7681 23.0
1.8022 Misc'l Lines W5 TO DISTR. HEAT 76.8 9.0783 76.3 8.9791 75.2
8.6993 74.3 8.4782 73.5 8.2984 72.9 8.1491 W6 TO MAIN 49.0 9.0782
49.0 8.9794 49.0 8.6994 49.0 8.4781 49.0 8.2983 49.0 8.1493 W10
WARM DRAIN 49.0 0.0001 49.0 0.0000 49.0 0.0000 49.0 0.0000 49.0
0.0000 49.0 0.0000 W11 COOL DRAIN 23.0 0.1772 23.0 0.1603 23.0
0.1150 23.0 0.0832 23.0 0.0599 23.0 0.0425 HEAT RECOVERY KJ KJ KJ
KJ KJ KJ ORC CYCLE 1329.8 1330.0 1330.3 1330.5 1330.7 1330.9
DISTRICT HEATING 1054.4 1027.3 952.9 896.2 851.5 815.4 FUEL LCV
INPUT 2000.0 2000.0 2000.0 2000.0 2000.0 2000.0 EFFICIENCY (%)
119.2 117.9 114.2 111.3 109.1 107.3
TABLE-US-00002 TABLE II H2O O2 N2 CO2 g GAS SYSTEM ('C.) (kg/s) vol
% vol % vol % vol % H2O/kg GAS SYSTEM when fuel moisture is 50%:
AIR A1 20.0 1.0775 0.90 20.79 78.21 0.10 5.67 A2 44.0 1.1374 8.98
19.09 71.83 0.09 61.59 A3 44.0 0.9100 8.98 19.09 71.83 0.09 61.59
A4 44.0 0.2275 8.98 19.09 71.83 0.09 61.59 A5 64.0 0.2556 23.59
16.03 60.30 0.08 192.66 FLUE F1 1050.0 1.4376 31.96 3.33 54.25
10.46 275.92 F2 400.0 1.4376 31.96 3.33 54.25 10.46 275.92 F3 79.3
1.6797 45.52 2.66 43.44 8.38 490.76 F4 41.3 1.1828 7.81 4.51 73.50
14.17 49.79 GAS SYSTEM when fuel moisture is 10% AIR A1 20.0 1.2104
0.90 20.79 78.21 0.10 5.67 A2 44.0 1.2778 8.98 19.09 71.83 0.09
61.59 A3 44.0 1.0222 8.98 19.09 71.83 0.09 61.59 A4 44.0 0.2556
8.98 19.09 71.83 0.09 61.59 A5 64.0 0.2871 23.59 16.03 60.30 0.08
192.66 FLUE F1 1050.0 1.5067 24.48 3.69 60.22 11.61 190.40 F2 400.0
1.5067 24.48 3.69 60.22 11.61 190.40 F3 75.9 1.7515 39.52 2.96
48.23 9.30 383.79 F4 39.8 1.3233 7.19 4.54 74.00 14.27 45.53
* * * * *