ESP, MDC AND BAG FILTERS.

 

ESP, MDC, and BAG FILTERS

1. The above-mentioned equipments are pollution control units associated with boiler operation.
2. The present prescribed norms by Pollution control boards the permissible SPM (suspended particulate matter) is limited to 50 ppm in the flue gases passing through stack or chimney.
3. In earlier days the MDC's and bag filters played major parts in arresting particulates from flue gas. but their efficiency was hardly about 85 to 90%.
4. In present condition the ESP'S are unavoidable considering the stringent norms prescribed by PCB. The efficiency of an ESP is 99%. there by meeting the norms prescribed by PCB
5. For small boilers operating on solid fuels such as coal, brickets, bagasse, paddy husk etc MDC is sufficient depending upon the location of the plant
these mechanical dust collectors operates on cycone whirling principles to remove heavier particulates and dischage considerably cleaner flue gas through chimney via I.D.FAN. periodical cleaning of MDC and Checking the condition of cycone cones are important in operation of MDC. A chocked nozzles in the cones circumference and  damaged cyclone cones  are major problem for improper functioning of MDC. A chocked nozzles creates enormous backfire in the furnace and damaged cones fails to arrest the particulates passing through the chimney.
6. The bag filters usually associated with coal fired boilers only. the restriction of flue gas temperature passing through these filters plays important role in the success of this unit. often we experience the damage of bags due to higher flue gas temperature and Mal functioning of solenoid valves because of compressed air which operates these valves. bagasse fired and husk fired boilers generally will not have bag filters due to fire particles in the flue gas which burns the bags. even improved glass filled filter bags which presently fitted in these filters are not pool proof.
7. This left with only ESP'S have to be established with high pressure higher capacity boilers used in many industries as a captive power plant which caters both steam and power requirements. the highest efficiency of atleast 99% is more reliable in boiler operation. however the operation and maintenance costs of ESP are sufficiently higher than MDC and bag filters. Ash conditioning unit is necessary with ESP to avoid spreading of fly ash to the surrounding areas of boiler house. A standby MDC is always recommended along with ESP. in case of break downs.
8. Electro static precipitator operates on d.c voltage current to separate the ash particulates from flue gas by ionizing it into positive and negative ions which are attracted by positive electrodes and negative plates provoded in the ESP. the collected ash are  removed by giving hammer blows or otherwise. ash handling unit is connected with it.

For further information one can always reach me by email or phone given below

K GOPALAN
9420663740/9108956202
kgopalan1956@gmail.com

Grate area, Furnace area and Furnace volume

 

grate area, Furnace area and Furnace volume in boiler operation and performance.

1. we know that the fuel is to be burned in the boiler furnace to generate steam for process and power generation.
2. As such where the fuel has to be burned is called grate and this grate area plays very important role in boiler operation and its performance.
3. The grate area should be sufficient enough to burn the required quantity of fuel continuously to liberate heat for steam generation. lesser the area then sufficient amount of fuel cannot be burned resulting in less steam generation. more the area the flue gas velocity gets reduced such that heat transfer will be erratic thereby influencing its performance.
4. stationary grate, traveling grate, pulsating grate, dumping grate, fluidised bed are types of grates normally used in boilers.
5.The Furnace area will be little more than grate area and the function is to transfer radiant or direct heat transfer to water wall tubes and is part of total heating surface of boiler comprising water wall tubes, inbeded tubes in FBC boilers.
6. Furnace volume is the complete volume of the Furnace consisting Furnace area, water wall refractory area, screen tube area, super heater zone, etc primarily almost all heat transfer areas included in upto total height of the Furnace. the larger the volume, burning of fuel more efficient, better heat transfer, more efficient burning of volatiles and reducing unburnt fuel. proper circulation of flue gases through all heating surface and better control of flue gas temperature.

Thus grate area, Furnace area and Furnace volume are plays more important roles in optimization of boiler operation and its performance. proper care must be taken to check these parameters proportional to boiler capacity before we place order for boiler.

It is very sad to say the commercial minds of manufacturers dominating their engineering brain in order to survive in the present competitive environment as such we are forced to face operational problems.

For more information one can always contact me by mail or phone given below

K GOPALAN
kgopalan1956@gmail.com
9420663740/9108956202.

APH AND ECONOMISER ROLE IN BOILER OPERATION.

 

Role of APH and Economiser in boiler operation and performance.

1. Both APH and Economiser are used as heat recovery units to recover heat from flue gases thereby reducing the temperature of flue gases thus reducing heat loss going into atmosphere.
2, APH air preheater is used to recover the heat from flue gas and transfer the same to cool atmospheric air before going into furnace.
3. heated primary and secondary air is always advantage for good combustion of fuel in the furnace. a reduction of 22 degree in flue gas reduces the fuel by 1%.
thereby increasing the boiler efficiency.
4.Apart from heat recovery unit this APH also act as pollution control unit to lesser extent. The present norms of 50 ppm of suspended particulate matter (SPM) Prescribed by POLLUTION CONTROL BOARDS plays an important role in selecting suitable design of APH.
5. Heat transfer in APH is mainly by convextion process. The design of passing air through the tubes and flue gases from out side is always desirable for better maintenance and easy cleaning.
6. Presently designers of APH are prefering carton stell tubes for cold end and carbon steel for hot end to minimize cold end corrosion of tunes. but my recommendation is to go with carton steel tubes only for both cold and hot sides as it gives longer life and replacement will be less.
7.Economiser is another important heat recovery unit in boiler design. It unimaginable to have boiler with out economiser. feed water is heated in the economiser before feeding it into the boiler drum. Feed water temperature nearer to the saturation temperature of steam is always recommended before feeding into boiler drum.As the flue gas temperature is higher after leaving bank tubes Economiser is placed first and APH after it. also heat transfer from gas to water always more efficient than transfer of heat from gas to air. therefore Economiser's efficiency is always more than that of APH. more over Economiser is considered as pressure part integral with boiler pressure parts and needs IBR Approval. whereas APH is non pressure part and IBR approval is not necessary. as as a rule every 6 degree rise in feed water temperature 1% fuel is saved. thus Economiser saves alot of fuel and increases boiler efficiency considerably.
7. Another important equipment in boiler system is deareter where the dissoved oxygen and other gases are removed from from feed water by heating the water minimum 105 degree and more depending upon boiler working pressure and temperature of super heated steam . this removal of oxygen and other gases is necessary to protect the tubes from pitting and erosion. but this areator is not a heat recovery unit.

For further information one can always reach me by email or phone given below

K GOPALAN.
Kgopalan1956@gmail.com
9420663740/9108956202.

Quality of fuels used in boilers

 

quality of fuels used in boilers.

In boiler operation and performance the quality of fuels play an important role.  

1. Normally we uses solid, liquid and gas  as fuels in operating the boilers.
2.The solid fuels are coal, wood, brickets, bagasse, paddy husk etc.
2. The liquid fuels are furnace oil, LDO, HSD, concentrated liquors from process plants,  etc
3. Gaseous fuels are CNG, BIOGAS, PRODUCER GAS etc.
4.Since Gaseous fuels are very clean we may not experience much of operational problems.
5. Liquid fuels barring furnace oil are also clean as such operational problems are less but furnace oil fired boilers face lot of problems .
6.Solid fuels boilers are one which normally encounter lot of problems. we will focus more on solid fired boilers particularly coal fired boilers.

The quality of coal play major part for operational problems in a boiler. There are many grades of coal available which can be classified from GRADE A to GRADE H.
grade A is good quality and grade H be the worst quality. normally grade A  and B are used in large scale power plants and the normal process industries will uses mostly grade C are lower. There are imported coal are used in boilers. The main problem in the Indian coal is high percentage of ash content. The medium scale process industries normally use high ash content coal because it is cheaper than imported coal in which ash content is significantly less. This high ash percentage will poses major problems in boiler operation. This ash get deposited in outer surface of boiler tubes in water tube boilers and inside in smoke tube boilers. this ash deposit over tubes reduces heat transfer and thereby boiler efficiency. though soot blowing  and air lancing operations removes most ashes from tube surfaces, still will not remove all. For this reason we will take periodical cleaning of boilers.The other solid fuels such as bagasse, husk are also create this problems but to lower extent. Though we know the problem of ash, we don't have any other options considering the economic in operating the industries. sulphur is another content in coal which creates corrosion problems in furnace grate, flue gas passages, ducting, and chimney. flue gas desulfuricatipn (FDG) is remedy for this problem but not viable for its high costs.
Calorific Value of fuel namely NCV net Calorific value of fuel plays on boiler performance and not GCV. since GCV gross Calorific value is includes hydrogen heating value which is not useful for heat transfer in boilers.
Boiler Manufacturers always shows efficiency based on GCV rather than NCV.
to show higher figures.
Preparation of coal for boiler such as screening, sizing, segregation improves boiler performance.
Don't get fooled by c.v.figure of coal coal suppliers. it is the figure of dried coal and the as supplied which we use in boilers normally.
further information one can always contact me by mail or phone given below.

K GOPALAN.
Kgopalan1956@gmail.com
9429663740/9208956202

Importance of combustion in boiler operations

 

Importance of combustion in boiler operation and performance.

combustion is the process of releasing the heat in the fuel with the help of oxygen available in the air to produce steam for process and power requirements of a process industry. there are many fuels available in the form of solid, liquid and gas. In any fuel the percentage of available carbon is counted for combustion in the boiler furnace.

carbon + oxygen = carbon di oxide

C+O2=CO2 ,molecular weight of carbon is12 and that of oxygen is 16
there fore, we have

12+2×16= 12+32= 44
12 ÷12 + 32÷12= 44÷12
1+8÷3 =11÷3
1+2.67=3.67

That is one kg of carbon requires 2.67 kg of oxygen for sticometric combustion of fuel. but in practical sticometric ratio of fuel to air will not provide complete combustion. therefore such amount of excess air is always necessary to achieve complete combustion of fuel.
1 kg of air consists 0.23 kg of oxygen. therefore for 2.67 kg of oxygen will require
2.67÷0.23 =11.61kg of air. for burning 1 kg of carbon we require 11.67 kg of air for combustion. other than carbon the fuel will consist of hydrogen, sulphur and other organic materials in some small quantities  as such air is required for burning those components as well. apart from this some quantity of excess air ranging from 10%to 50% be required additionally. so the F.D fan  must designed for this requirement of air for smooth and proper combustion of fuel in the furnace. the furnace grate area is  also must have sufficient to burn this much quantity of fuel. by having sufficient fan capacities and furnace area the combustion will be proper and the performance of boiler operation will be quite good.

for further information one can always be contacted by email or phone given below.

K GOPALAN.
kgopalan1956@gmail.com
9420663740/9108956202.

Importance of draught fans in boiler operation

 

Importance of draught in boiler operation and performance.

In the boiler operation we normally have three types of draught fans. they are 1. forced draught fan. 2. induced draught fan and 3. secondary air fan.

The functions of these fans are primarily to maintain sufficient Furnace draught in order to make the combustion of the fuel in grate such that the release of heat is maximum for steam generation.

more often we experience problems in combustion of fuel such as black smoke emissions through chimney, unburnt fuel in the ash, fouling of tubes ( water tubes and superheater tubes) etc, because of improper functioning of draught fans . we now look into this fans functioning.

1. F.D. Fan(forced draught fan). The function of this fan is to supply sufficient amount of  primary air (oxygen) to burn the fuel in furnace, also should be able to supply certain amont of excess air for complete combustion. The design of F.D fan is such that sufficient amount of air to be supplied with sufficient pressure ( draught). if proper care was not taken in volume and pressure requirements then it would create more problems. Most of the time boiler manufacturers provide fans with best design options thereby it will perform well when experiences worst conditions. more over boiler may use multi fuels sometimes for which this fans may not sufficient to supply required air. Therefore carefull consideration will be given in selection when we place order for boiler. most of the times the end user are forced to change the fan to higher capacity  after experience more difficulties while operating. Therefore one must consider the F.D fan size for worst fuel and operating conditions likely used so that it can takes care of best fuel and operating conditions. as a thump rule a 10% more in pressure and 25% more in capacity is ideal for the selection.

2. I.D.Fan.(induced draught fan). The primary function of this fan to suck the hot combustion gases from boiler furnace through no of heat exchangers such as furnace tubes, super heater tubes, boiler bank tubes, economiser tubes, air preheater tubes, M.D.C, ESP etc keeping sufficient draught in respective zones. modern boiler employes balanced draught design thereby keeping negative draught of -2mm to -5mmwc. Any under capacity fan will result back firing, fouling of tubes more unburnts black smoke emissions which drastically effect boiler operation and performance. therefore care must be taken before order of boiler as explained in F.D.fan case. most common problems are fan become unbalanced, more vibrations, bearing failures, erosion of fan blades, and ducts etc.

3. S.A.fans (secondary air fan).  In normal conditions the problems within S.A fans are neglible. it function is to burn volatiles and carbon left after primary combustion.

for more information one easily approach me by mail or phone given below.

K GOPALAN.
Kgopalan1956@gmail.com
9420663740/9208956202.

Boiler feed water quality

 

BOILER OPERATION AND PERFORMANCE

Boilers in any process plants is considered as a heart to its continuous operations, any unwanted stoppage or breakdowns leads to heavy loss to the plants. Therefore good performance of boiler is necessary to any process plants. We now discuss what are various parameters which can affect its performance and efficiency.

1. FEED Water Quality
2. F.D, I.D, and S.A. Fans.
3. Combustion
4. Quality of fuels used.
5. Grate area, Furnace area and Furnace volume.
6. Heat recovery units such as APH and Economiser.
7. pollution control units such as MDS and ESP.

In this post we will discuss the feed water quality

for maximum failure cases in boiler operation and its performance is because of poor quality of feed water. high pressure boilers and turbine house are integrated parts of distilleriey plants. poor quality water leads to scaling of tubes, drum inner side, drum internals and feed pipes. The scaling of boiler pressure parts affects its operational efficiency to large extent. it affects heat transfer from fuel to water, lower quantity and quality of steam generation which leads to more consumption of fuel and thereby lesser efficiency. The first and foremost point to consider is therefore the feed water quality.
Hence to have good quality of feed water one must have good water treatment plant
A simple soft water plant is sufficient for a small low pressure boilers used in chemical process plants with out steam turbine. however for a distilleriey plants which requires high pressure boilers with steam turbine one has to consider a D.M.plant  in series with softener plant.
the idea to have a softener plant before D.M plant is to have longer life of D.M Plant
and to some extent lesser times of regeneration cycles of D.M plant. Apart from having water treatment plant  one must have deareter to increase the water temperature 105 degrees and above to remove dissolved oxygen and other unwanted gases from feed water to keep heating surfaces clean and reduce erosion.
we hereby conclude water quality topic
for boiler operations.
For draught fans topic we will consider in the next post.
For any further information one can always contact me by mail or phone given below.

K GOPALAN
kgopalan1956@gmail.com
9420663740/9108956202.