Process for improving operation of large-scale combustors

Abstract

The heat output, e.g., megawatt product or steam generation, of a combustor is increased, preferably while plume is mitigated, by targeting treatment chemicals to locations in a furnace. The process improves heat output from the fuel in the region of the combustor optimum for heat recovery and also maintains good heat transfer characteristics for the heat exchange surfaces. The effectiveness of targeted in furnace injection, in-fuel introduction and in-furnace introduction of slag and / or corrosion and / or plume control chemicals are preferably determined, as are the effectiveness of targeted in furnace injection, in fuel introduction and in furnace introduction of combustion catalysts. Then, the effectiveness of various combinations of the above treatments are determined, and a treatment regimen employing one or more of the above treatments is selected. Preferred treatment regimens will contain at least two and preferably three of the treatments. Chemical utilization and boiler maintenance can improved as LOI carbon, slagging and / or corrosion are also controlled. In one preferred embodiment, the invention enables increasing by determining the positions for effective introduction of slag controlling chemical, introducing targeted slag controlling chemical treatment in an amount effective to reduce slag and introducing a combustion catalyst into the flame in an amount effective to improve combustion.

Description

RELATED APPLICATIONS [0001] This application is a continuation-in-part of and claims priority to prior U.S. patent application Ser. No. 10 / 754,072 filed Jan. 8, 2004.BACKGROUND OF THE INVENTION [0002] The invention relates to a process for increasing the heat output of large-scale combustors, such as the type used industrially and by utilities to provide power and incinerate waste. According to the invention, heat output is increased while, or plume opacity is mitigated, preferably both, and / or slag and / or corrosion are reduced. The invention achieves one or more of these desired results through the use of one or more chemicals, which in one embodiment is a unique combination of combustion catalyst and slag modifier. The chemicals are preferably introduced by targeted in-furnace injection, and / or in-body injection. [0003] The combustion of carbonaceous fuels, such as heavy fuel oils, coals, refinery coke, biomass and municipal and industrial waste, is typically less efficient than w...

AI Technical Summary

Benefits of technology

[0036] It is a distinct advantage of the invention that plume can be well controlled at the same time as corrosion, slag LOI carbon, and / or SO3. The net effect in many cases is a synergy in operation that saves money and / or increases efficiency in terms of lower stack temperatures, cleaner air heater surfaces, lower corrosion rates in the air heaters and ducts, lower excess O2, cleaner water walls, resulting in lower furnace exit temperatures and cleaner heat transfer surfaces in the convection sections of the boiler.

[0037] The process of the invention can be looked at from the unique perspective of system analysis. According to this aspect of the invention, the effectiveness of targeted in furnace injection, in fuel introduction and in furnace introduction of slag and / or corrosion and / or plume control chemicals are determined, as are the effectiveness of targeted in furnace injection, in fuel introduction and in furnace introduction of combustion catalysts. Then, the effectiveness of various combinations of the above treatments are determined, and a treatment regimen employing one or more of the above treatments is selected. Preferred treatment regimens will contain at least two and preferably three of the treatments. In each case, a determination can be any evaluation whether or not assisted by computer or the techniques of the above-referenced patents. In addition, it may involve direct or remote observation during operation or down times. The key factor here and a departure from the prior art is that targeted injection is evaluated along with nontargeted introduction, especially of a combination of combustion catalysts and slagging and / or corrosion and / or plume control chemicals. Chemical utilization and boiler maintenance can improved as LOI carbon, slagging and / or corrosion are also controlled.

[0038] The following examples are provided to further illustrate and explain the invention, without being limiting in any regard. Unless otherwise indicated, all parts and percentages are based on the weight of the composition at the particular point of reference.

Problems solved by technology

The combustion of carbonaceous fuels, such as heavy fuel oils, coals, refinery coke, biomass and municipal and industrial waste, is typically less efficient than would be desired; and in some cases the imposition of pollution control requirements is viewed as a cost penalty because the combustors are less able to efficiently produce electricity or steam.

In addition, these fuels contain slag-forming materials, and can generate corrosive acids, and unburned carbon, that in combination have a relatively negative effect on the productivity of the boilers, and can corrode the environment and pose a health risk.

Plume is a problem from an aesthetic standpoint as well as an environmental one.

Plume can be objectionable in and of itself and is expensive to treat by conventional technology.

While plume opacity is of concern from an external pollution position, slagging and some of the other problems caused by combustion can affect efficiency—therefore, economics, which are a severe threat to older power plants, especially, where efficiency is required for pollution controls to be affordable for maintaining the plants in operation.

Slagging deposits are sometimes extremely difficult to remove by conventional techniques such as soot blowing.

Slag buildup results in a loss of heat transfer throughout the system, increases draft loss, limits gas throughput and is a factor in tube failure due to erosion from excessive sootblowing.

The introduction of chemicals in this manner is often very inefficient and increases the amount of ash that must be disposed.

Corrosion control is too often a choice between polluting byproducts.

Unfortunately, the introduction of the chemicals has been very expensive due to poor utilization of the chemicals, much simply going to waste and some reacting with hot ash that would not otherwise cause a problem.

The presence of unburned carbon in the ash is an indication that combustion is not efficient and can cause operational problems.

This can be effective in some situations, but the use of excess air always decreases boiler efficiency.

Also, excess air increases SO2 to SO3 conversion, causing additional acid aerosol plume and may also increase NOx levels.

The use of combustion catalysts can also be effective in some cases; however, combustion catalysts cannot always be used effectively or efficiently due to fuel and / or equipment limitations.

Carbon in the ash can decrease commercial value of the ash, which can be used in concrete if the LOI can be reduced to less than 2%.

It has now been observed in some cases that the same treatments effective for plume reduction can also result in increased heat production by a combustor.

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