[0001] The system object of the patent consists, in its basic version, of a probe or probes
and in a variety of openings, that by its special characteristics, allow the accomplishment
of measurements or characterisations in high temperature areas (nearness of the burners,
or any other area of the interior of the furnace of industrial boilers). These local
measurements intend to optimise the operation of each burner, allowing the global
improvement of parameters like combustion efficiency, loss on ignition, polluting
agents formation and slagging processes.
[0002] The small holes are drilled through the membranes which join the water tubes making
up the water walls of these type of facilities, making feasible the mentioned local
measurements with no need to undertake substantial modifications in the boiler. The
probe is designed taking into account the limitation entailed by the membranes width
(typically around 20 mm) and, therefore, the openings carried out on them.
[0003] Additionally, the subject of this patent is the fully automated version of the described
system, that allows the continuous characterisation and monitoring of boiler combustion
conditions.
[0004] These systems are equally applicable to optimisation of industrial furnaces, through
the adjustment of their burners by means of measuring in areas of high temperatures.
BACKGROUND OF THE INVENTION
* Sector of the Technique
[0005] Industrial furnaces are facilities where the fuel (pulverised coal, fueloil, gasoil,
gas, etc) is injected into the combustion chamber through burners tips, where it reaches
the ignition point and bums to produce heat. This heat is transmitted to the water
that circulates through the pipes that make up the boiler walls, and to other heat
exchanging equipment, producing steam at high pressure and temperature. The energy
of this steam may have a use in several industrial operations or it may be recovered
as mechanical energy in a turbine, with the posibility to be subsequently transformed
into electric energy by means of an alternator connected to the turbine.
[0006] The performance and generation of pollutants in industrial boilers depends largely
on the correct distribution of fuel and air in the furnace, and so the existence of
critical areas with an inappropriate air/fuel ratio will negatively affect these extremely
important parameters. In the same way, in the specific case of coal, these imbalances
may generate substoichiometric areas in which the fusion point of the ash is reduced,
facilitating its accumulation on the boiler tubes (slagging). This phenomenon gives
rise to important heat transfer losses, and can cause problems which make it necessary
to shut down the facility, with the consequent loss of production.
[0007] These imbalances between the proportions of air and fuel are also very problematic
for the burners used in the furnaces of any type of industrial process, affecting
their energetic performance, as well as the quality of the products and byproducts
obtained from them.
* State of the Art:
[0008] In industrial furnaces, mainly at thermal power stations, the use of systems for
the analysis of combustion gases located at the boiler outlet is frequent. These systems
are used for adjusting and controlling the overall combustion process. Thus, the determination
of parameters such as the oxygen and carbon monoxide at the boiler outlet, allows
the identification of the correct development of the combustion.
[0009] However, the optimisation of the process using these values has certain limitations,
even when the analysis of gases is carried out at a large number of points uniformly
distributed among the boiler outlets. These limitations, with respect to the distance
from the actual combustion area, the evolution of the flame, and the degree of mixing
of the gases in the measurement area, do not allow effective characterisation of each
individual burner performance, and therefore do not permit optimisation of the overall
combustion process.
[0010] In the current state of the art, different available equips are commercialised by
numerous companies (Storm Technologies, ESA, IFRF, etc), which allow direct determinations
inside the furnace (water-cooled probes, suction pyrometers, high speed thermocouples,
etc). However, these pieces of equipment are designed to measure through the boiler
inspection ports, which are several centimetres in size and located only at certain
points on the furnace.
[0011] Therefore, this type of measurement inside the furnace is not representative enough,
since it is restricted to the areas where direct access is available through the inspection
ports originally installed. This restriction exists because it would require important
structural modifications to the design of the boiler tube layout to make more openings
of this type (over 20 mm in size, and normally around 100 mm).
[0012] Other approaches attempt the characterisation of combustion processes consisting
of systems based on sensors located on the boiler walls. These sensors measure the
signals of different wavelengths produced by the combustion process itself. They can
be divided into Passive Systems, which determine some property of the flames generated
(such as flame detectors, infrared pyrometers, cameras or heat flow sensors located
in the tubes); and Active Systems, which characterise the signals generated by emitters
located in other areas of the boiler, that are attenuated or modified during their
transmission through the furnace (for example, systems based on acoustic principles).
[0013] Examples of these industrial applications based on sensors or "wall" or "contour"
measurement systems are collected in numerous patents, as for example, US 4555800,
US 3824391, US 4176369, DE 3224500, US 5794549, EP 0802372, DE 4328629 and US 4756684
(passive systems) and WO 9710473 (active systems), that are in any case indirect measurements
of the real combustion process, since they are based on determinations taken at the
edge of the furnace.
[0014] These facts justify the little information available about the real development of
the combustion processes as far as their representativeness in the boilers of industrial
size is concerned.
[0015] These limitations in the knowledge of the local combustion conditions are equally
extrapolable to the furnaces of any type of industrial process.
DESCRIPTION OF THE INVENTION
[0016] This invention involves a system which allows measurements to be taken in any area
of the interior of the furnace of industrial boilers, specially near the burners.
Some examples of this type of measurement are the evaluation of local levels of gas
concentrations, temperatures, heat flows, and even image capture, in these areas of
high temperature and very limited access in boilers of traditional design. The aim
of these measurements is to identify the combustion conditions at any particular point
inside the boilers, in order to be able to optimise heat rate, consumption of auxiliaries,
and generation of pollutants and slagging.
[0017] This local information makes it possible to consider the unit as a collection of
small virtual units, each made up of a single burner. The targeted adjustment of each
of these smaller units results in overall optimisation of the boiler.
[0018] In order to meet these goals, the system allows these measurements to be made through
small openings made in the membranes which join the tubes making up the water walls
of the boiler. The width of these openings (around 14 mm) is limited by the width
of the membranes themselves (around 20 mm), while the height is unlimited, due to
the geometry of the membranes.
[0019] This new concept for measurement inside the furnace of industrial boilers, makes
it possible to place the openings in any location required, without being limited
to those inspection ports included in the original design of the boiler, and permits
the direct measurement of combustion conditions inside the furnace. In this way, it
is possible to take measurements at the level of each burner in the boiler, without
any significant structural modifications to the unit. In order to access the inside
of the furnace, for the extraction of samples or the insertion of sensors, a water-cooled
probe either made of or covered by ceramic material, has been specially designed for
insertion through these openings, which additionally is able to withstand the high
temperatures (1400 - 1700 °C) in these areas of the furnace.
[0020] An optional upgrade to the system allows automatic operation by means of the following:
motorization of the probe (insertion - extraction, lateral movement); a system of
continuous treatment and analysis of the gas samples collected or of the data provided
by the sensors inserted into the furnace by the probe; a cleaning system using a compressed
air counterflow which guarantees the autonomy of the system between measurements;
advanced monitoring software which, in addition to controlling the operation of the
entire automated system and the correct processing of the results obtained, provides
operational recommendations to the operator of the plant. These recommendations are
based on results and the experience in the optimisation of this process.
[0021] The invention described is applicable, to the optimisation of any type of burner,
for example those in industrial furnaces.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] For a better understanding of every description contained in this report, some drawings
are supplied only to serve as accomplishment examples of some system variants.
[0023] Thus, Figure 1 presents a schematic drawing of the system in its basic version, where
the sampling probe (1) is introduced through the opening (2) inside the furnace boiler
(3). This small opening (2) is made in the membrane (4) which join the tubes (5) making
up the water walls of the boiler, close to a facility burner.
[0024] Figure 2 represents a probe longitudinal section (1) in its cooled and gas sampling
variant; the outer socket (6) of entrance and exit of the coolant fluid and its circulation
once inside the probe is shown. Also, the sample aspiration conduct can be observed
(7). Figure 3 presents a front view and a cross section of the opening (2) made in
the membrane (4) between the tubes (5), for the sampling probe variant (1) shown in
Figure 2 (cooled and for gas sampling).
[0025] Figure 4 presents a schematic drawing of an automated system version, specifically
its variant for gas sampling, in which the sampling probes displacement can only be
of insertion-extraction (a sampling probe by orifice), or with additional lateral
displacement (a sampling probe for several orifices). Figure 5 shows the schematic
drawing of the required elements for this variant.
DESCRIPTION OF A FAVOURITE ACCOMPLISHMENT
[0026] The access openings (2) are distributed throughout the boiler close to each burner.
The detail of one of these openings, for the variant of cooled and gas sampling probes
variant, appears in Figure 3, where its geometry can be appreciated (two semicircles
of 7 mm radius joined by a square of 14 mm side).
[0027] The water cooled probe is specially designed to support the high existing temperatures
in this zone (between 1400 and 1700°C) and to accede to the interior of the boiler
through the described orifices.
[0028] In its cooled gas sampling variant (Figure 2), a tube of rectangular section can
be used for its construction (14 x 12 mm sides and 1 mm thick) and two half tubes
(7 mm radius and 1 mm thickness) welded as shown in the figure Section A-a. In this
same section the three resulting cameras can be appreciated (8, 9, 10) through which
the refrigeration fluid, for example, water, flows. Out of these, the chamber in the
middle (9) is crossed by a 6 mm diameter tube through which the gas sample is extracted
to be analysed. These elements are assembled at the probes end by means of two half
cones and two triangular plates, according to what is observed in the detail of the
probes end (Figure 2). In the opposite end an outer socket is arranged (6) allowing
the exit and entrance of the refrigeration fluid and of the sample collection tube.
[0029] Summarising, the route described by the cooling fluid is as follows: it enters through
the orifice (11) into the A chamber socket (12), flowing then into the two sampling
probe outer chamber (8) and (10). After reaching the end of the sampling probe the
fluid returns through the central chamber (9) until reaching the B socket chamber
(13) where it leaves the sampling probe through the orifice (14).
[0030] A system automation schematic drawing is presented in Figure 4.In this figure, the
sampling probe (11), being cooled or not, is coupled to a pneumatic cylinder (15),
controlled by a multiway valve (16), to insert or retract the probe in or out of the
furnace boiler(3).
[0031] In the version for gas sampling and analysis, shown in the mentioned Figure 4, the
sample collected by the probe passes through a heated filter to eliminate ash in suspension,
and then goes to a set of valves which either send the sample to the conditioning
system, or send pressurised air towards the heated filter and the probe, giving rise
to a countercurrent which cleans both of these items.
[0032] A typical sample conditioning system (19) is made up of a condenser, a cooler, a
filter and a pump. This conditioning system may be housed in a cabinet (20) located
on the cylinder-probe assembly support, which can also be used to house the valves,
or in an adjacent location in order to service several probes.
[0033] The sample is taken from the conditioning system to an analysis system, which consists
essentially of a gas analyser (21), together with other filters, a humidity detector
and a valve to control the input of samples to the analyser.
[0034] A programmable logic controller (PLC) (22) is used to collect the analysis results,
monitor the entire process and report on possible incidents. This information is sent
to a control room computer (23) with the necessary user interfaces, which also collects
information from other PCLs or monitoring systems. This computer also has software
designed to offer operational recommendations to the plant operator, based on the
readings, and on a number of rules gathered from experience on the optimisation of
the process.
[0035] This latter version has, in general, more advantages from the point of view of investment
and maintenance costs, although the characterisation period is slightly increased.
The photograph in Figure 9 shows this design, which is schematically presented in
the plant view of the drawing in Figure 12.
[0036] For the automated version with lateral displacement (one probe for several openings),
Figure 5, the gases sampling probe (1) or the insertion of any sensor type into the
furnace, the pneumatic cylinder (15), the multiway valve (16) which controls the cylinder
and other auxiliary equipment (for example, in the case of the gas sampling version,
the heated filter (17), the set of control valves (18) and the sample conditioning
system (19) located in the cabinet (29), which may also house the valves (16) and
(18)) are all located on a motorised (25) carriage (24). This makes it possible to
move the whole assembly for taking measurements in other parts of the boiler.
[0037] The carriage (24) has several proximity sensors (26), which stop the motors at positioners
(27) marking the exact position of the sampling points. In order for the carriage
(24) to halt exactly at the right spot, an automated speed control (28) reduces the
speed of the motors to a minimum as it approaches the positioner (27), due to a location
signal provided by an appropriate device (e.g. an encoder (29) located on the carriage
(24)).
1. System which allows measurements (by means of gas extraction or by insertion of sensors)
in any area of the interior of the furnace (high temperature areas) of industrial
boilers (as the ones in power plants), enabling combustion process optimisation in
these facilities based on the results obtained by the local measurements; this system
being characterised by and comprising the following elements: A) openings to access the furnace whose reduced
dimensions (width lower than the membranes which join the tubes making up the water
walls of the boiler, typically <20 mm) allow their placement on the mentioned membranes,
in such a way that enable direct measurements to be taken inside the boiler (not only
around its surrounding area), such as gas concentration measurements by means of sampling
on a prefixed point and subsequent analysis, temperature and heat flow measurements,
image capture at any wavelength, without the need of carrying out structural modifications
to the design of the boiler tube layout; B) small transversal dimension sampling probe
or probes, specially designed for the gas sampling and sensors insertion and conditioning
in high temperature areas, through the previously mentioned small openings.
2. System according to claim 1, where the sampling probe or probes are inserted inside
the boilers furnace through the small openings made in the proximity of each one of
the burners, in order to allow their individual optimisation.
3. System according to claims 1 or 2, where the sampling probe or probes are cooled by
water, water with additives, oil, oil with additives, air or any other kind of coolant
fluid.
4. System according to claims 1 or 2, where the sampling probe or probes are constructed
or externally covered by any kind of ceramic material, able to properly withstand
the high temperatures existing inside the boilers furnace, avoiding in such a way
the use of coolant fluids.
5. System according to claims 1, 2, 3 or 4, where the sampling probe or probes are fully
automated and controlled by specific software for all their various displacement capabilities,
using a sampling probe provided with the insertion-extraction movement capability,
for each small opening through which the measurement is intended.
6. System according to claims 1, 2, 3 or 4, where the sampling probe or probes are fully
automated and controlled by specific software for all their various displacement capabilities,
using one or more sampling probes, each one of them used for measuring through several
small openings, by means of lateral displacements in addition to the insertion-extraction
movements.
7. System according to claim 6, allowing the sampling probe or probes to face up the
small openings to access the inside of the furnace boiler with a precision of ±1 mm,
for example by the use of a combined action of proximity sensors for the final positioning
at the right point, and an encoder that allows a change of speed of the lateral displacement
depending on the distance to the positioner (greater speed at the beginning of the
movement, and slower speed as it approaches the positioner); or by any other positioning
system and determination of the sampling probe location that involves the use of infrared,
acoustic, electromagnetic or any other wavelengths techniques.
8. System according to claims 5, 6, or 7, characterised, in its furnace gases analysis version, by locating the treatment and conditioning systems
over the sampling probe stand, moving jointly with it in the lateral displacement
version described on claims 6 and 7; and being the mentioned treatment and conditioning
systems composed of a dust filter to hold the ashes and a cooling and/or sample moisture
condensing system.
9. System according to claims 5, 6, 7, or 8, allowing the cleaning of the sampling circuit
by means of countercurrent pressurised air (dust filter and sampling probe blowing)
making the system autonomous between sampling periods.
10. System according to claims 5, 6, 7, 8 or 9 where the results obtained in the local
measurements taken by the system itself, are transferred to the facility Control Room,
to enable process monitoring and adjustment.
11. System according to claims 5, 6, 7, 8, 9 or 10 provided with combustion optimisation
software (performance, pollutants generation, slagging, etc.) based on the results
given by the system local measurements and eventually other plant operational data
or results.
12. System according to the previous claims applied to combustion processes other than
the ones contained in claim 1, and being more specific, those which use gaseous, liquid
or solid fuel or mixtures of these, under presence of air, enriched air, and in general
any oxidising agent.
13. System according to claims 1 to 11 applied to other industrial burners, in a global
or individual way, as for example the ones mounted in process furnaces, clinker furnaces,
metallurgic furnaces, toxic and dangerous waste incinerators or solid urban waste
incinerators.