the use of the method of the invention permits real - time review of the level and / or rate of ash / slag deposition occurring for given process conditions . the real - time review permits the deposition process to be monitored more closely and , thus , minimized . the longer a boiler / furnace operates , the more ash or slag that deposits on internal boiler and heat exchanger contact surfaces . as deposition increases , the temperature indicated by a thermocouple will decrease . the level of temperature decrease correlates inversely to increase in deposition . the htp or slag probe useful in the present invention is constructed of a high - temperature alloy and is insertable and removable / retractable from the boiler / furnace . the probe has at least one and preferably a plurality of thermocouples to measure temperature . the probe preferably takes the general shape of a rod , pole , or lance with thermocouples positioned at points therealong . thermocouples may also be positioned to be oriented toward or away from ( or both ) the flame within the boiler / furnace . the probe is preferably air - cooled to maintain particular temperature conditions within the probe . the temperature of the probe is maintained independently of the temperature within the boiler / furnace . an example of a useful probe is shown in the fig1 . although not critical to the present invention , deposition or buildup can be controlled in boilers and furnaces by a variety of methods those methods include ( i ) use of slag control agents and oxygen - generating agents ; ( ii ) control of process variables such as temperature , pressure , and air feed rate ; and ( iii ) control of feedstock composition . a slag control agent is optionally employed to prevent buildup of deposits within the furnace of the utility boiler and other process surfaces . the slag control agent reacts with sulfuric acid to form innocuous , non - acidic compounds , thereby reducing acid emissions and corrosion of process surfaces within the utility boiler . the slag control agent also reacts or complexes with any undesirable vanadium compounds that may be present in the fuel oil . conversion of undesirable vanadium compounds , such as vanadium pentoxide and sodium vanadium pentoxide , to more innocuous vanadium compounds or forms helps to prevent or reduce catalysis of sulfur dioxide to sulfur trioxide , corrosion of process surfaces due to acid exposure , and deposition of vanadium compounds on process surfaces inside the utility boiler . slag control agents are useful in both oil - fired and coal - fired boilers . useful slag control agents include , but are not limited to , the following : magnesium hydroxide ; magnesium oxide ; magnesium carbonate ; and magnesium organometallic compounds , such as magnesium carboxylate , magnesium salicylate , magnesium naphthenate , and magnesium sulfonate . preferred slag control agents are magnesium hydroxide , magnesium oxide , and organometallic magnesium carboxylate with magnesium carbonate overlay . an oxygen - generating agent is optionally employed to provide additional oxygen at the situs of oxidation or burning in the furnace , which allows the feed rate of air supplied to the utility boiler to be reduced and / or minimized . use of the oxygen - generating agent also reduces the incidence of unburned carbon due to more efficient combustion or burning . reduction of unburned carbon also reduces the incidence and retention of sulfuric acid , which is absorbed by unburned carbon . oxygen - generating agents are useful in both oil - fired and coal - fired boilers . useful oxygen - generating agents include , but are not limited to , the following : calcium nitrate , calcium organometallic compounds , calcium salicylate , calcium sulfonate , overbased calcium carboxylate , iron oxides , iron carboxylates , iron organometallic compounds , iron sulfonates , barium oxide , barium carbonate , barium carboxylate , barium organometallic compounds , and barium sulfonate . preferred oxygen - generating agents are the calcium compounds . most preferred oxygen - generating agents are calcium nitrate and calcium carboxylate . the slag control agent and the oxygen - generating agent can be added or mixed into the fuel oil prior to combustion or added into the furnace of the utility boiler during combustion or burning . the treatment of the fuel oil can be homogeneous or non - homogeneous , i . e ., the agents can be homogeneously admixed within the fuel oil or non - homogeneously applied , such as to the surface or some portion of the fuel oil . the slag control agent and the oxygen - generating agent can be added or mixed in like manner in coal - fired boilers . the slag control agent and the oxygen - generating agent can be used in any known product form , such as a powder or liquid . liquids may be water - based , oil - based , or a combination thereof . liquids may take any known liquid form , such as solutions , slurries , suspensions , dispersions , or emulsions . liquid forms are preferred since they can be injected or sprayed with precision via conventional pumping and metering devices . a preferred means of adding the slag control agent and the oxygen - generating agent to the fuel oil or coal is via injection in liquid form . the amount of slag control agent employed will vary depending upon a variety of process and composition conditions , such as type of slag control agent selected , load or feed rate of fuel oil or coal , amount and type of oxygen - generating agent used , percent of excess oxygen desired , amount or feed rate of air , impurity composition of fuel oil or coal , and the like . when a liquid form of the slag control agent is used , the amount employed will typically vary from about 1 : 2000 to about 1 : 6000 agent : fuel oil , volume : volume . the amount of oxygen - generating agent employed will vary depending upon a variety of process and composition conditions , such as type of oxygen - generating agent selected , load or feed rate of fuel oil , amount and type of slag control agent used , percent of excess oxygen desired , amount or feed rate of air , impurity composition of fuel oil , and the like . when a liquid form of the oxygen - generating agent is used , the amount employed will typically vary from about 1 : 1000 to about 1 : 10000 and preferably about 1 : 2500 to about 1 : 4000 agent : fuel oil , volume : volume . an advantage of the present invention is characterization and control / minimization of slag deposition on process surfaces within the boiler / furnace and other process surfaces in contact with the exhaust gas . slag deposition can take the form of one or more layers caked / baked onto process surfaces . for instance , slag can deposit on the surfaces of tube bundles or other heat transfer devices within the utility boiler denuding the heat transfer efficiency of the utility boiler . an inner layer typically takes the form of metal complexes of vanadium with sodium , nickel , or iron . the vanadium / sodium , vanadium / nickel , and vanadium / iron metal complexes exhibit relatively low melting points , i . e ., 1000 ° f . to 1700 ° f . and leave a sticky deposit or buildup on process surfaces . another layer may form on the inner layer and take the form of vanadium / magnesium complexes exhibiting slightly higher melting points than the vanadium / sodium , vanadium / nickel , or vanadium / iron complexes . the vanadium / magnesium metal complexes are water soluble and friable , and can be washed and easily removed by conventional techniques , such as soot blowing . however , if elevated amounts of slag control agent , such as magnesium oxide , are used , the slag control agent may deposit on the surfaces of the layers of the metal complexes and be difficult or impossible to remove . magnesium oxide , a commonly used slag control agent , for example , is not water soluble or friable and is very difficult to remove by conventional techniques . another advantage of the present invention is characterization and control / minimization of ash deposition on process surfaces within the boiler / furnace and other process surfaces in contact with the exhaust gas . ash deposition occurs in both oil - fired and coal - fired boilers , but is a particular problem in coal - fired boilers due to the considerable ash content in coal . ash takes the form of noncombustible metals and / or minerals . the physical properties of ash vary depending on its composition depending on the properties of the ash . ash may take a liquid or a solid deposition form in an operating boiler depending on the properties of the ash . ash deposition on tube surfaces and other process surfaces impedes heat transfer and can cause boiler temperatures to rise unnecessarily and / or diminish steam production and / or otherwise diminish efficient operation of the boiler . additional teachings regarding the operation of utility boilers and furnaces are shown in u . s . patent publication no . 2006 / 0257799 a1 , which is incorporated herein by reference . in the following examples , time versus temperature can be measured and set forth in plots / graphs . for one means of analysis , a linear regression line is drawn through the data points to yield a slope . a lower slope indicates slower deposition ( slower buildup ) and a higher slope indicates faster deposition ( faster buildup ). the use of the method of the invention permits real - time review of the level and / or rate of ash / slag deposition occurring for given process conditions . the real - time review permits the deposition process to be monitored more closely and , thus , minimized . the htp , or “ slag probe ”, is a temperature controlled thermocoupled high alloy furnace probe that duplicates generating tube surface metal temperatures to establish baseline data vs . treatment with fuel additives , characterize high temperature deposit formation and treatment modification . this diagnostic tool enables ees to establish product feed rate ( s ) based on fuel quality and furnace temperatures as well as to quantify the effectiveness of treatment . the slag probe will be used to determine deposit composition and provide samples for the ash porosity test . htp probes were run on the 10 th floor pendant superheat section ( center of the west side ), and on the 9 th floor division superheat section ( north east corner ). the data is broken down by test number , location , zone 1 or 4 , and condition ( baseline , condition 1 , and condition 2 ). the average htp temperatures increase from zone 4 to zone 1 and represent the steam tube surface and subsequent insulating layers . zone 1 and zone 4 were chosen for analysis to show hot region deposits ( z1 ) and cold region deposits ( z4 ). however , due to lack of buildup on the 9 th floor htp &# 39 ; s , only zone 1 was analyzed . all deposits were sent out for mineral analysis ; 8 point fusion temperature analyses were performed only on the hot region deposits . after condition 1 was reached with the ct300 treatment ( mg ( oh ) 2 — magnesium hydroxide ), the probe deposits showed visual modification as evidenced by the photos in appendix iii . as treatment was continued , deposits would not stick to the probe , instead would bend up and pull away from the probe surface — see photo htp 9 . this indicates that the ct300 is interacting within the first eutectic melt phase and inhibiting the ash / slag buildup from bonding to the simulated tube surface . after condition 2 was reached with co - treatment of ct300 and ct100 ( cunh 3 ac ), the probe deposits were found to be visually different than htp 9 , see trial log and notes above for htp 11 . the mineral analysis of the deposits confirms that a major change in composition has occurred by introducing ct100 . more magnesium is brought into the deposit in both zone 1 and zone 4 along with a 50 % drop in iron content . in the case of zone 1 an increase in copper of 85 % was determined by icp spectroscopy . a large shift in calcium and silica was also observed as evidenced by the lack of black glass on the condition 2 probe . analysis of the deposition rate data clearly shows a reduction in deposition of 35 % for htp 9 versus baseline . this does not as change much for condition 2 but still represents a decrease with respect to baseline . the htp temperature graphs in appendix iv demonstrate how slag builds and sheds during conditions 1 and 2 where as baseline probes yield graphs with consistent steeper slopes .