Claims:WE CLAIM:
1. A dynamic flow adjuster assembly to improve distribution of pulverized coal-air mixture in pulverized coal pipes comprising of an orifice plate held to a driven shaft at one end thereof, wherein the driven shaft is driven by a drive shaft, one end of which is mounted with a rotatable stationary hand wheel for operating said orifice plate.

2. The dynamic flow adjuster assembly to improve distribution of pulverized coal-air mixture in pulverized coal pipesas claimed in claim 1, wherein the drive shaft drives the orifice gate mounted driven shaft radially inwards and outwards towards the pulverized coal pipe center according to direction of rotation of the hand wheel.

3. The dynamic flow adjuster assembly to improve distribution of pulverized coal-air mixture in pulverized coal pipes as claimed in claim 1 or 2, wherein a locking pin is provided with chain attachment on the hand wheel for engagement of the hand wheel with the drive shaft.

4. The dynamic flow adjuster assembly to improve distribution of pulverized coal-air mixture in pulverized coal pipes as claimed in any of the preceding claims, wherein the adjuster is connected to the coal pipe with the help of connecting flanges.

5. The dynamic flow adjuster assembly to improve distribution of pulverized coal-air mixture in pulverized coal pipes as claimed in any of the preceding claims, wherein the drive shaft is secured to the flow adjuster body at both ends thereof by means of mounting brackets allowing rotational motion of the hand wheel.

6. The dynamic flow adjuster assembly to improve distribution of pulverized coal-air mixture in pulverized coal pipes as claimed in any of the preceding claims, wherein the drive rod and follower rod assembly is enclosed by means of a plurality of plates and main support channels.

7. The dynamic flow adjuster assembly to improve distribution of pulverized coal-air mixture in pulverized coal pipes as claimed in any of the preceding claims, wherein a cam bolt is provided on the drive shaft, in which the cam bolt is having a threaded hole to hold the drive shaft and another plain hole to hold the driven shaft by means of fastener.

8. The dynamic flow adjuster assembly to improve distribution of pulverized coal-air mixture in pulverized coal pipes as claimed in any of the preceding claims, wherein the driven shaft slides on housing assembly mounted on top of the top cover plate and the orifice plate slides over the low friction strips placed inside the gate body bottom plate.

9. The dynamic flow adjuster assembly to improve distribution of pulverized coal-air mixture in pulverized coal pipes as claimed in any of the preceding claims, wherein the housing assembly is provided with O-ring seal and stuffing box sealing.

10. The dynamic flow adjuster assembly to improve distribution of pulverized coal-air mixture in pulverized coal pipes as claimed in any of the preceding claims, wherein a pointer assembly on the top plate is mounted on the cam bolt.
, Description:A dynamic flow adjuster assembly to improve distribution of pulverized coal-air mixture in pulverized coal pipes
FIELD OF INVENTION
[001] The present invention relates to a dynamic flow adjuster assembly to improve distribution of pulverized coal-air mixture in pulverized coal pipes. The present invention is designed to improve the distribution of the pulverised coal-air mixture evenly in pulverised coal pipes of thermal power plants by introducing the wear resistant dynamic flow adjuster.

BACKGROUND OF THE INVENTION

[002] In the context of newly introduced stringent emission norms for the coal fired power plants, combustion optimization becomes very critical and cost effective tool to combat the pollution emissions apart from other derived benefits like low unburnt in ash, which helps in attaining optimum performance of the power station. In pulverized coal fired utility boilers, mixture of pulverised coal and primary air from mills is transferred through steel pipes. As each mill is serving all corners of a tangential fired boiler, the pipe routing results in differential coal pipe travel lengths. To nullify the effect due to differential coal pipe lengths on coal-air mixture distribution and pressure drop across all pipes of a pulveriser, static or fixed orifices are employed. These fixed orifices selections are carried out for a fixed set of coal air mixture condition reference to design point on account of quality of coal and primary air. In real time operation, these parameters may change due to various reasons attributed to site dynamic conditions. Hence the effect of fixed orifice in the coal pipe may not serve the purpose fully. To perform the combustion tuning and optimization in such a challenging environment is extremely difficult without proper tools. Hence a system is required to be developed to meet the requirement.

[003] Purpose of the coal pipe balancing is to distribute the coal air mixture in all pulveriser outlets uniformly across the mill operating load range. Main critical parameter is the coal air mixture velocity, which is a function of coal piping geometry, coal type, coal moisture content, coal fineness, temperature of coal-air mixture and primary air quantity. There are various factors on which power plant operators cannot have control. Change in any of the above said parameters may disturb the flow pattern across the coal pipes of a pulveriser. Unbalance in coal air mixture flow across the coal pipes may result in multiple problems like improper coal combustion inside the furnace. Thus by flame fluctuation across this corner, improper coal combustion may result in coal accumulation in the furnace bottom, which may also lead to furnace explosion. This may also result in coal chocking due to poor coal air mixture velocity. This can cause undesirable operational issues like coal pluggage, faster wear of pulverised coal pipes and associated components, and may also resulting in unit tripping.

[004] In order to address these issues during change of coal parameters and other operating regime, a dynamic flow adjuster along with online coal flow measurement is being introduced in the coal pipes in addition to static orifices. The static orifices are sized to meet the design conditions, while dynamic flow adjusters serve for the dynamic operating conditions in thermal power plants.
DESCRPITION OF THE PRIOR ART:

[005] The pulverisers of coal fired thermal power plants are provided with a plurality of pipes carrying coal-air mixture to transport from the pulverisers to furnace. Each pulveriser may have to serve multiple pipes after pulverization of coal. The pulverised coal from mill is carried to furnace locations through steel pipes by hot gas or hot air pumped by a fan in general. Due to different destination of coal pipe ends, and pipe routing results in different equivalent lengths of coal pipes of a pulveriser. Thus results in different pressure drops that causes coal flow difference across the coal pipes. However, flow of the coal air mixture is required to be uniformly distributed in all pipes coming out of a pulveriser to have stable efficient combustion.

[006] In order to address this issue most of the pulveriser coal pipes in coal fired boilers are fitted with only a static orifice with fixed opening area different from the pipe opening area. These static orifices accommodate the coal-air mixture balance to a constant value due to fixed orifice opening. Due to dynamic state of the coal qualities and pulveriser operating parameters, fixed orifices may fall short of the requirements of satisfactory pulverised coal-air balancing. For addressing this, a change of orifice size is required. This is accomplished by designing new static orifice and getting it fixed in the pulverised coal pipes. Design and manufacturing of required orifice is tedious and requires to stop the running pulveriser to fix the newly designed static orifices. However the newly fixed static orifice will be working in functionally satisfactory condition till the coal characteristics are not changed. Present commercial coal source and availability is very dynamic. Any change of coal properties may put burden on the pulverised coal handling equipment and performance thereof. More over the pulverised coal is very abrasive in nature and causes lot of erosion of the steel pipes which it carries at velocities from 0 to ~28 M/s. During long operational time of the pulverisers, pipes carrying pulverised coal get punctured and potentially cause unsafe operational environment in the power plants. To address this chronic issues a simple viable equipment like flow adjusters were introduced. Most of these devices are butterfly valve type or multiple blade type were tested on records. But the multiple blade type flow adjuster gives almost required flow balancing performance in laboratory kind environment, which may not give the satisfactory conditions at real world coal fired thermal power plants due to cloggy / sticky nature of pulverised coal inside the multiple blades cavities. While butterfly valve type flow adjusters are reliable in thermal power plant applications but may fail to hold the performance due to high wear of the internal components. These flow adjusters produce reasonably stable performance elsewhere but for pulverised coal fired boilers the requirement is more rugged and simple in operation.

[007] Some known arts pertinent to variable orifice may be discussed hereinunder:-

[008] US patent 20170023035 reveals that plurality of multiple blades pivotally mounted with the housing to pivot between a retracted position and an extended position, each blade including a gas path edge, wherein the retracted position the gas path edges of the blades conform to the flow orifice, and in the extended position, the blades extend inward from the flow orifice wherein the gas path edge of each blade is spaced apart from the other blades. This apparatus claims using of multiple blades pivotally mounted on the body assembly so as to balance the coal air mixture.

[009] Another US patent 20070095260 discloses a method of controlling the distribution of coal in a pulverized coal-fired boiler system having at least one coal pulverizer and at least two burners disposed on a boiler enclosure for receiving pulverized coal from the at least one coal pulverizer. The method comprising: providing a coal feed system for supplying coal from the at least one coal pulverizer to the at least two burners, in which the coal feed system having a coal pipe junction with a riffle enclosure comprising a plurality of parallel partition walls forming multiple flow channels from an upstream coal pipe to each of at least two downstream pipes; providing a plurality of pilotable vanes upstream of the plurality of partition walls; and pivoting at least one of the plurality of pilotable vanes to control the distribution of coal among the at least two downstream coal pipes. This apparatus uses multiple blades with parallel partitions for flow distribution.

[0010] US patent US20040050306 is directed to an apparatus for controlling primary air flow and pulverized coal flow to a plurality of burners in a coal-fired boiler comprising: a plurality of coal dampers arranged to supply a mixture of air and pulverized coal to respective burners in the coal-fired boiler. Each damper is having a damper body and at least two orifice plates pivotally secured therein, in which said orifice plates are movable between open and closed positions; a real time coal flow monitoring device is operatively associated with each damper that is adapted to generate analog signals representing real time coal flow through its respective damper; and a programmable logic controller adapted to receive said analog signals and to adjust said orifice plates to balance the flow of air and pulverized coal to each of the plurality of burners. This apparatus uses automated control duel blades with parallel shaft arrangement for flow distribution.

[0011] Thus, none of the cited arts fulfill the requirements of the instant invention for which it is designed. Hence, the present invention introduces a dynamic flow adjuster assembly to improve distribution of pulverized coal-air mixture in pulverized coal pipes.

OBJECTS OF THE INVENTION

[0012] An object of the present invention is to provide a dynamic flow adjuster assembly to improve distribution of pulverized coal-air mixture in pulverized coal pipes.

[0013] Another object of the present invention is to provide a dynamic flow adjuster assembly to improve distribution of pulverized coal-air mixture in pulverized coal pipes which overcomes disadvantages of prior art.

[0014] Yet another object of the present invention is to provide a dynamic flow adjuster assembly to improve distribution of pulverized coal-air mixture in pulverized coal pipes which is efficient.

SUMMARY OF THE INVENTION

[0015] The present invention is pertinent to wear resistant dynamic flow adjuster gate assembly (Fig.2) employed for establishing the pulverised coal-air mixture balancing in all pipes of a pulveriser that carries the pulverised coal-air mixture by modulating manually the orifice opening using the pressure drop in the fuel pipes (Fig. 1). This flow adjuster is connected to pulverised coal- air mixture carrying pipes with flanged connection or coupling connection ends provided therewith. The dynamic flow adjuster transfers coal pipe load from one end to other end with the help of this connection. This orifice gate is operated manually by rotating stationary hand wheel mounted at one end of drive shaft which drives the orifice gate mounted rod radially inwards and radially outwards to the pulverised coal pipe center based on the direction of the hand wheel rotation. Hand wheel must be engaged with drive shaft for operation of the orifice gate. A locking pin provided with chain attachment on the hand wheel. For engaging the hand wheel, this pin needs to be inserted after bringing concentrically the locking holes provided on the drive shaft and hand wheel hub. This stationary drive shaft is fixedly secured with body. This orifice gate is connected to the coal pipe without any additional support. Thus subjected to bending movement due to self-weight of the orifice may subjected to permanent bending of the rods. This strucks the moving components after prolonged hours of elevated temperature operation with harsh environment. To overcome this issue parallel shafts arrangement is provided. This dynamic flow adjuster assembly is provided with small gear box with simple screw mechanism with parallel shaft assembly to reduce the total length of the orifice gate. This reduces the over-hang length of the flow adjuster assembly from the coal pipe center.

[0016] Drive shaft is fitted firmly on the flow adjuster body (Fig. 3) at both ends butt to allow rotational motion by using hand wheel fitted at one end. Drive rod and follower rod assembly is housed in dust tight environment so as to protect the equipment. Follower rod holds the orifice gate plate firmly at one end. The rotational movement of hand wheel produces linear movement of cam bolt provided on the drive shaft. The cam blot holds the drive shaft and driven shaft by means of parallel holes. In cam bolt, one hole with threaded provision has internal matching thread with drive shaft and another plain hole to hold the driven shaft by using locking nuts. Cam bolt is stationary to the driven shaft by the locking nuts. Flow adjuster orifice gate is mounted at one end of the driven shaft. Driven shaft slides on housing assembly mounted on top of the orifice body. Simultaneously, the orifice plate mounted on the driven-shaft slides over the low friction strips provided inside the gate body assembly. Housing assembly is mounted on the top cover plate to provide leak proof sealing. This housing assembly is provided with two level sealing system, one with O-ring and next level with stuffing box sealing. The housing assembly holds the drive shaft and allows the driven shaft to slide therethrough. Orifice gate plate always moves inside the orifice body during operation on a pair of friction free guides attached to the orifice body. Atleast two bearing surfaces fixed at either sides of the orifice gate, glides on the friction free guides. Orifice plate is provided with knife edge front to penetrate into coal path. During movement, sharp edges of orifice plate easily penetrate into the stagnated coal on the wall edges of the flow adjuster body. One of the main provisions for clearing the stagnated coal in passive areas inside the orifice is provided at four entry locations around the orifice body assembly through air entry nozzles. Air from these entry nozzles is distributed around the gate plate inside the body by air header provided at three sides. Air pushes the stagnated coal into the pulverised coal-air mixture path gradually.

[0017] Body assembly forms the main enclosure connected to the coal-air mixture transporting pipes with flanged connection or with a coupling. The body is designed to withstand the explosion pressure i.e., for example 50 psi of the coal air mixtures. Body is provided with sufficient structural rigidity to withstand elevated temperatures for prolonged duration of operation. Also it allows to transfer the coal pipe load from one end connection of orifice to other end of orifice connection. Dynamic flow adjuster body holds the orifice plate with the help of front cover body flange and top cover plate tightly by bolts and nuts. During maintenance, gate plate is removed by unbolting the top cover plate from the body flange.

[0018] All the internal components exposed to pulverised coal air are provided with high alumina ceramic lining for wear protection. The lining is provided in the orifice body assembly and orifice gate plate where the pulverised coal air mixture comes in contact. Use of ceramic lining in the flow adjuster orifice plate is optimized by implementing computational fluid dynamic analysis.

[0019] Full open position or completely retracted position of wear resistant dynamic flow adjuster behaves like coal pipe resulting in no resistance to coal path due to orifice gate plate. As the orifice gate advances towards the coal pipe central axis, gate plate offers resistance to flow path or pressure drop in the pulverised coal-air medium. Closed position of orifice is treated as fully penetrated condition. At fully closed position of orifice, pulverised coal-air path still has 1/3rd of coal pipe opening area to flow. This helps to avoid situation leading to complete blocking of the coal air path, even if accidentally kept at complete penetrated position of the orifice plate.

[0020] At this position of the orifice plate inside the coal pipe, maximum pressure drop is introduced due to flow obstruction of the orifice plate. This pressure drop is measured by using pressure transmitters.

[0021] Position indication scales of two numbers are provided with pointer assembly on the top of gear box top plate with transparent cover to monitor the orifice position during operation. This pointer assembly is mounted on the cam bolt. One scale is provided with percentage opening of the pipe area by the orifice gate plate with finer graduations called percentage scale. This scale is meant to observe the incremental opening during trails to balance the coal air mixture flow in parallel piping system. Another scale with equivalent orifice diameter scale is called orifice diameter scale. Orifice diameter scale indicates the equivalent orifice diameter due to the position of the orifice inside the coal air path. Orifice diameter scale is having integer graduations within the operable range. This helps in setting the predetermined position without conducting any prior tests to accomplish the balancing of the coal air mixture in pulverised coal ping system.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
[0022] Further objects and advantages of this invention will be more apparent from the ensuing description when read in conjunction with the accompanying drawings of the exemplary embodiments and wherein:

Fig 1 shows: Positioning of variable orifice in pulverised coal piping system from pulverised to furnace wind box along with pressure measuring points in a coal fired power plants.
Fig 2 shows: Sectional view of wear resistant dynamic flow adjuster with internal constructional details according to present invention.
Fig 3 shows: Enlarged view for the details of Internal guides and bearing pads for smooth movement of orifice plate in the present invention.
Fig 4 shows: Details of position of graduation scales and hand wheel with locking pin arrangement with drive shaft.
Fig 5 shows: Side sectional view of dynamic flow adjuster in accordance with present invention.
Fig 6 shows: Top view indicating direction of hand wheel for closing and opening along with flow direction indicator.

DETAIL DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE PRESENT INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS

[0023] The present invention imparts teaching regarding a technology pertinent to a dynamic flow adjuster assembly to improve distribution of pulverized coal-air mixture in pulverized coal pipes. The wear resistant dynamic flow adjuster 001 assembly is used for establishing the pulverised coal-air mixture balancing in all the pipes 061 of a pulveriser 059 that carries the pulverised coal-air mixture by modulating manually the orifice opening by making use of the pressure drop in the fuel pipes. This dynamic flow adjuster assembly 01 is connected to the multiple pulverised coal- air mixture carrying pipes with flanged 005 connection or coupling connection ends provided by fasteners like bolts 008 and nuts 009. The wear resistant dynamic flow adjuster 001 transfers load of coal pipe with this flanged connection 005. This dynamic flow adjuster 001 is modulated to equalize the pressure drop measured between pulveriser and coal pipe in proximity to the furnace where it is connected to windbox 062. This measurement is carried out with the help of pressure gauges 060, 064. This orifice gate is operated manually by rotating stationary hand wheel 037 mounted at one end of the drive shaft 029, which drives the orifice gate mounted rod 053 radially inwards and radially outwards to the pulverised coal pipe center according to the direction of the hand wheel 037 rotation. Said hand wheel (037) must be in engagement with drive shaft (029) for operation of the orifice gate. Further, a locking pin 046 is provided with chain 047 attachment on the hand wheel. For engaging the hand wheel 037 with drive shaft, this pin 046 is required to be inserted after bringing concentrically the locking holes provided on the drive shaft 029 and hand wheel hub 036. This stationary drive shaft 029 is fixedly secured with body. This dynamic flow adjuster 001 is connected to the coal pipe 061 with the help of connecting flanges 005 without any external supporting arrangement. By parallel shaft arrangement, the amount of overhang length of the flow adjuster 001 reduces from the center of coal pipe.

[0024] Thus, this dynamic flow adjuster is mounted on each coal pipe of pulveriser with flanged/coupled ends to establish the pulverised coal – air flow balancing. Based on the amount of area reduction through dynamic flow adjuster, it offers flow resistance in the coal transporting pipe, thereby changing the amount of coal-air mixture carried by a coal pipe. In coal fired thermal power plants, pulverised coal pipes are generally of different equivalent lengths owing to physical orientation with furnace entry point and pulverisers location. In order to neutralize the effect due to difference of lengths of coal pipes, this flow adjuster orifice plate is manually adjusted to attain the orifice opening area required.

[0025] Said drive shaft 029 is fitted firmly on the flow adjuster body at both ends thereof with the help of multiple mounting brackets 031, 055 but at the same time allows rotational motion by using hand wheel 037 placed at one end. The drive rod 029 and follower rod 053 assembly is accommodated in dust tight environment so as to protect the equipment by plates 032, 038, 049 and main support channels 057, 058. The follower rod 053 holds the orifice gate plate 013 firmly at one end thereof. The rotational movement of hand wheel 037 produces linear movement of cam bolt 026 provided on the drive shaft 029. The cam blot 026 holds the drive shaft 029 and driven shaft 053 by parallel holes therein(cam bolt 026). In cam bolt 026, one hole is having inner threaded surface to accommodate outer threaded surface of the drive shaft (029) and another plain hole to hold the driven shaft 053 by using locking nuts 027. Here, the cam bolt 026 moves along with the driven shaft 053. The orifice gate plate 013 mounted at one end of the driven shaft 053 is provided with ceramic lined wear protection 012.

[0026] The ceramic lined orifice body is provided with flanged/coupling connections co-axially to connect with coal transporting pipes without any external support and has box type construction with body flange, bottom plate, side plates and top plate to form the housing of orifice plate and the gear box.

[0027] The parallel shaft gear box with stationary drive shaft rotation produces liner motion of the cam bolt mounted on drive shaft by screw train. The only required liner motion of orifice plate holding driven shaft is given by the cam bolt on the drive shaft by fixing it by means of the locking nuts.

[0028] Said driven shaft 053 slides on housing assembly 022, 023 mounted on top of the top cover plate 041. Simultaneously, the orifice plate 013 mounted on the driven-shaft slides over the low friction strips 015 provided inside the gate body bottom plate 003. The housing assembly 022, 023 is provided with two level sealing system, one with O-ring seal and next level with stuffing box sealing 063. The Orifice gate plate 013 always moves inside the orifice body during operation on a pair of friction free guides 054 attached to the dynamic flow adjuster body. One of the main provisions for clearing the stagnated coal in passive areas inside the orifice is formed at four entry locations around the orifice body assembly through air entry nozzles 040 043. Air from these entry nozzles is distributed around the gate plate inside the body by air header located at three sides.

[0029] The body is provided with sufficient structural rigidity with stiffness to withstand elevated temperatures for prolonged duration of operation. The dynamic flow adjuster body holds the orifice plate tightly with help of front cover body flange 019 and top cover plate 041 by bolts 016, washer 017 and nuts 018. During maintenance, gate plate is removed by unbolting the top cover plate from the body flange.

[0030] Position indication scales of two numbers 045, 048 are provided with pointer assembly 039 on the top plate 038 with transparent cover 051 to monitor the orifice position during operation. This pointer assembly 039 is mounted on the cam bolt 026. One scale is provided with percentage opening 048 of the pipe area by the orifice gate plate with finer graduations called percentage scale and another scale with equivalent orifice diameter scale 045 is called orifice diameter scale.

[0031] It is to be noted that the present invention is susceptible to modifications, adaptations and changes by those skilled in the art. Such variant embodiments employing the concepts and features of this invention are intended to be within the scope of the present invention, which is further set forth under the following claims:-