单选题One of the main purposes of refractories in a boiler furnace is to（）Ahelp preheat the air for the furnacesBhelp preheat the feedwaterCprotect economizer from excessive heatDprevent excessive furnace heat losses
单选题
One of the main purposes of refractories in a boiler furnace is to（）
A
help preheat the air for the furnaces
B
help preheat the feedwater
C
protect economizer from excessive heat
D
prevent excessive furnace heat losses
参考解析
解析：
暂无解析
相关考题：
6 Communication is important for all organisations and requires an understanding of communication flows and channels.Required:(a) Briefly explain the main purposes of the three main formal communication channels in an organisation:(i) Downwards; (3 marks)
According to the passage, the main purposes of futures contracts are ______.A．to hedgeB．to speculateC．to arbitrageD．all of the above
In a()boiler the hot gases from the furnace pass gases from the furnace pass water is on the outside. A.water-tubeB.fire-tubeC.exhaust gasD.composite
The maximum pressure developed by a waste heat boiler is determined by the main engine exhaust ______.A.gas compositionB.gas temperatureC.pressureD.timing
A fire pump may be used for other purposes if ______.A.the other services are run off a reducing station with a pressure gageB.one of the required pumps is kept available for use on the fire main system at all timesC.no relief valves are installedD.all of the above conditions are met
Texts are usually used in English classes for two main purposes: as a way of developing reading comprehension and as a way of learning new language.（）A对B错
One of the main advantages of a graphite-furnace atomizer is that（）A、It requires only very small quantities of a sampleB、It requires metal.ions in aqueous solutionC、It does not produce background emission like a flameD、It does not get hot like a flame
Texts are usually used in English classes for two main purposes: as a way of developing reading comprehension and as a way of learning new language.（）
The air waybill number is the identification of each consignment and comprises three parts（）.A、the main portion identifying the consignmentB、a three-digit prefix identifying the carrierC、the main portion identifying the carrierD、the last check digit for accounting and security purposes
Which three statements about subqueries are true? （）A、A main query can have more than one subquery.B、A subquery can have more than one main query.C、The subquery and main query must retrieve data from the same table.D、The subquery and main query can retrieve data from different tables.E、Only one column or expression can be compared between the subquery and main query.F、Multiple columns or expression can be compared between the subquery and main query.
You are designing a site topology for the new Active Directory environment. What should you do?（）A、Create one site for all offices. Place the subnets for the four branch offices and the Sydney main office in this site. B、Create two sites: one site for the four branch offices and one site for the Sydney main office. Place the subnets for the branch offices in one site. Place the subnet for the Sydney main office in the other site. C、Create three sites: one site for the four branch offices, one site for the Sydney main office, and one site for the Sydney satellite offices. D、Create four sites: one for the Melbourne and Perth branch offices, one site for the Berlin and Paris branch offices, one site for the Sydney main office, and one site for the Sydney satellite offices. E、Create five sites; one site for the Melbourne branch office, one site for the Perth branch office, one site for the Berlin branch office, one site for the Paris branch office, and one site for the Sydney main office. Place the subnets for each branch office and the Sydney main office in their respective sites.
单选题One of the main advantages of a graphite-furnace atomizer is that（）AIt requires only very small quantities of a sampleBIt requires metal.ions in aqueous solutionCIt does not produce background emission like a flameDIt does not get hot like a flame
单选题Too much air in the furnace of an oil-fired boiler would be indicated by （）.Ayellowish flameBgolden yellow flameCwhite flameDbrilliant white flame
单选题In the event of a flame failure in an auxiliary water-tube boiler, you must（）Arelight the boiler immediately to prevent loss of steam pressureBrelight the fire off the brickwork as the bricks are cherry redCpurge the furnace of any combustible gases before attempting to relight the fireDspeed up the feed pump to prevent dry firing when the burner flame is reestablished
单选题A distorted furnace in a fire-tube auxiliary boiler may be the result of （）Afiring for extended periods in the low fire modeBoverheating, due to waterside depositsCvarying the water level above the crown sheetDcarrying excessive alkalinity in the boiler water
单选题（）are supplied by main switchboard directly.ASuez Canal searchlight, air compressor and air conditioning compressorBAir compressor, boiler blower and refrigeration plantCBoiler blower, Suez Canal searchlight and refrigeration plantDSuez canal searchlight, air compressor and boiler blower
单选题Diesel engine waste heat boiler construction is usually of the fire-tube or（）Acyclone furnace boiler typeBdry back boiler typeCwater-tube typeDcritical circulation boiler type
单选题A dazzling white burner flame in the boiler furnace indicates （）.Aproper combustionBwater in the fuelCexcess airDcold fuel oil
单选题In a （） boiler the hot gases from the furnace pass through the tubes while the water is on the outside.Awater-tubeBfire-tubeCexhaust gasDNone of the above is true
单选题The purpose of the programmed purge cycle on an automatically fired auxiliary boiler is to（）Acool the furnace to prevent pre-ignitionBremove explosive vapors from the furnaceCevaporate accumulated unburned fuel oilDprovide sufficient air in the furnace to allow ignition of the fuel
单选题The maximum pressure developed by a waste heat boiler is determined by the main engine exhaust （）.Agas compositionBgas temperatureCpressureDtiming
单选题Multiple fire pumps may be used for other purposes provided that one pump is（）.Aon line to the fire mainBkept available for use on the fire main at all timesCcapable of being connected to the fire mainDrated at or above 125 psi
单选题Which one is not the normal operation for boiler shutdown?（）ACarry out soot blowing if permissibleBChange fuel supply to diesel oilCClose steam stop valves on boiler when pressure is reducedDDrain boiler empty when it has cooled down
多选题The air waybill number is the identification of each consignment and comprises three parts（）.Athe main portion identifying the consignmentBa three-digit prefix identifying the carrierCthe main portion identifying the carrierDthe last check digit for accounting and security purposes
填空题One of the purposes of reforestation projects is to protect the habitat and prevent species loss.____
单选题The furnace of an oil fired boiler should be （） before the operating burner is lit.Afilled with waterBpurgedCcleared of airDNone of the above is true
单选题A dazzling white burner flame in the boiler furnace indicates （）.Ano combustionBdeposits in the fuelCexcessive air in the fuelDcold fuel oil