The working environment for paper pulp production and paper making industry is highly corrosive, and can cause severe corrosive damage to technique equipments. Statistics show, the loss caused by corrosion is up to 6 dollars for each ton of paper pulp. In order to maintain smooth operation and to reduce cost, stainless steel and anti-corrosion alloy are widely used in paper pulp production, and have become the irreplaceable structure material in this area. When using different paper pulp and different pulp making technique, the brand of the stainless steel in use will differ accordingly, presently, the 0Cr18Ni9, 0Cr17Ni12Mo2, 0Cr19Ni13Mo3, 254SMO, 654SMO and double phase stainless steel and so on, have been widely used in the production of different paper pulp.

1. Stainless steel used in paper pulp production.
(1) Mechanical pulp making
In the process of mechanical pulp making, as chemistry drugs are not used, the corrosive extent is not so severe as the pulp making with sulfate and sulfite. In the early time, stainless steel was not much used under such environment; in recent years, for the purpose to reduce the repairing fee of the normal material and to promote economic benefit, as well as to prevent the pollution to paper pulp caused by iron rust, stainless steel is now widely used in mechanical pulp making, shown in the following table:

The application of stainless steel in mechanical pulp making

Equipment and part	Material	Remark
Pipe, pump and relevant accessories	00Cr18Ni10 00Cr17Ni14Mo2	Substituting the cast iron pipe, the medium contains acetic acid and formic acid, the PH is 4-5, it shall choose 00Cr18Ni10, when the content of chloride in the medium is high , use 00Cr17Ni14Mo2
Sprinkler of grinding drum and sprayer	00Cr18Ni10 00Cr17Ni14Mo2	Commonly use 00Cr18Ni10，in high temperature，use 00Cr17Ni14Mo2
Abstractor Equipment for disposing wood pieces	00Cr17Ni14Mo2 00Cr17Ni14Mo2	Used to send steam to the water contact parts and to dispose wood pieces
Filter equipment	00Cr18Ni10 00Cr17Ni14Mo2	The filter equipment and the filter plate of the separator, pipe end filter, filter slot, cylinder filter
Centrifugal purifier	00Cr18Ni10
Storage case	00Cr18Ni10
Spin-drier	00Cr18Ni10	The parts that contact the paper pulp, prevent the contamination to paper pulp
Cylinder dehydration press machine	00Cr17Ni14Mo2	Rotating cylinder of press machine and the filter slot

(2) Pulp making with sulfate method
In the pulp making technique process with sulfate method, the corrosion of the medium is not as high as with the sulfite method. In this process, the wood in the floating sea, the salt water and chemical drugs in use will all make the technique medium contain certain chloride, thus increasing the equipment corrosion. Practice experiences show, 00Cr18Ni10 and 00Cr17Ni14Mo2 can achieve a satisfying usage effect, and the application of stainless steel under this technique condition is shown in the table below:

The application of stainless steel in the pulp making with sulfate method

Name of equipment and part	Material	Remark
Cooking boiler	00Cr18Ni10 00Cr17Ni12Mo2	Used to make the boiler, the whole or the clad plate, lining
Wood crumbs preheater PH4.5-5.0，Cl- 8000ppm	00Cr17Ni14Mo2 00Cr25Ni6.5Mo3N(UR47N)	PH4.5-5，Cl-8000ppm 1 year of life span The life span can be over 4 years
Paper pulp preheater 170℃，Cl-≤800ppm	0Cr18Ni9 0Cr17Ni12Mo2 00Cr18Ni5Mo3Si2	A life span of 2-4 months 10 years of life span if no corrosion
Joining type boiler	00Cr18Ni10 00Cr17Ni14Mo2 2205	Clad plate The down part of the boiler is anti-corrosion, and is SCC resistant
Intermission boiler	0Cr17Ni14Mo2 2205和UR47N	Repair welding shall be needed each year More than 10 years of life span, no repair needed
Pipe system connected with the cooking , muzzles, sleeves	00Cr18Ni10 00Cr17Ni14Mo2 00Cr18Mo2 2205 00Cr19Ni13Mo2	1-3 years of life span 5 years of life span SCC resistant
auger conveyor for hot pulp	00Cr17Ni14Mo2
Drainage pipe	00Cr18Ni10 00Cr17Ni12Mo2	Matching with the material used for valves
Condenser	00Cr18Ni10 00Cr18Ni5Mo3Si2	SCC resistant
Paper pulp wash machine	00Cr18Ni10 00Cr17Ni14Mo2	Cylinder block , canister
Filtration equipment	00Cr18Ni10 00Cr17Ni14Mo2	Strum, filter
Centrifugal purifie	00Cr18Ni10	The upper part and down part of the purifier use pottery material
Stationary tank and bucket	00Cr18Ni10	Carbon steel lining
Spin-drier	00Cr18Ni10 00Cr17Ni14Mo2	Water slot filtration plate
Pipe pump, valve for disposing paper pulp	00Cr18Ni10 00Cr17Ni14Mo2 0Cr25Ni4Mo2(329)	Pipes, pumps , valves Used for pumps and valves contacting liquid high temperature and high chloride concentration
Pulp producing equipment	00Cr18Ni10 00Cr17Ni14Mo2
Alkalinity reclaim steamer	00Cr18Ni10 00Cr17Ni14Mo2	The outer layer is stainless steel, the inner pipe is carbon steel
Storage bucket for high corrosive black liquid	00Cr18Ni10	Carbon steel liningCarbon steel lining
Causticization container and bucket for green liquid and white liquid	0Cr18Ni10	Carbon steel lining
Gas washing tower	00Cr19Ni13Mo3 00Cr20Ni25Mo2Cu2

(3) Paper pulp making with sulfite method
The technique process of paper pulp making with sulfite method is one with the highest corrosion; in early time, the Calcium Hydrogen Sulfite that contains superfluous sulfur dioxide as the boiling liquid is used, this liquid is acidic, and can be only used to boil specific wood material. If the liquid is added with magnesium, sodium and ammonia to be treated as basic cooking liquor, then cooking liquor with different PH value can be acquired, and it can be applied to all kinds of wood material. As the chemical drug is expensive, and for the purpose of pollution prevention, the calcium hydrogen sulfite is forbidden to be released, thus it must be reclaimed through technique method like evaporation, etc, causing the processing equipment to be operated under severe corrosive environment. Equipments under this kind of environment shall bear sorts of corrosions including uniform corrosion, corrosive pitting, crevice corrosion, stress corrosion, abrasion, etc, so the material in use should have a higher grade than those used in the techniques illustrated above, the super austenite stainless steel （2RK65, 254SMO, 654SMO） and super double phase stainless steel have all been applied successfully. The application situations of stainless steel in the pulp producing process with sulfite method are shown in the table below:

Application of stainless steel in the pulp producing process with sulfite method

Name of equipment and part	Material	Remark
The connecting pipes that connect the mixer/ burner of iron sulfite mineral forge to the cooler tower and washing tower	0Cr25Ni4Mo2(329) 0Cr17、0Cr18Mo2	Resistance to high temperature and sulfur corrosion
Cooler tower, washing tower	00Cr17Ni4Mo2 00Cr18Ni15Mo4.5 00Cr20Ni18Mo6CuN(254SMO)	Upper part of tower Underpart of tower
Pipes for transporting pulp	00Cr20Ni18Mo6CuN 00Cr20Ni25Mo4.5Cu(2RK65)	Resistance to condensing sulfurous acid corrosion and sulfuric acid corrosion
Acid storing bucket	00Cr17Ni4Mo2 00Cr18Ni15Mo4.5 00Cr20Ni25Mo4.5	Used to maintain high pressure SO2 condition and for the making of according pipe Used on the upper part
Cooking boiler	00Cr17Ni14Mo2N 00Cr19Ni13Mo3N 00Cr20Ni25Mo4.5Cu 00Cr18Ni15Mo4.5 00Cr18Ni20Mo6CuN 00Cr25Ni6.5Mo3N	SCC resistant
Pipes connecting the cooking boiler and extraction device with heat method	00Cr17Ni14Mo2 00Cr19Ni13Mo2
Washing machine	00Cr17Ni14Mo2 00Cr19Ni13Mo2	Flow slot, washing pool, filter, container Filter web, canister
Filtration equipment	00Cr17Ni14Mo2	Strum, filter, centrifugal purifier
Spin-drier and according pipes	00Cr18Ni10 00Cr17Ni14Mo2
Reclaiming equipment for chemical drug	00Cr18Ni15Mo4.5 00Cr20Ni25Mo4.5Cu 00Cr17Ni14Mo2 00Cr17Ni14Mo3 00Cr20Ni18Mo6CuN	waste liquid bucket, 380℃ waste liquid bucket, ≤80℃ evaporator

(4) Pulp producing with semichemical method
The technique process of the pulp producing with semichemical method is between the chemistry method and mechanical method, material choosing of which will differ according to different chemical method being chosen. The most common method is the neutral sulfite semichemical method, namely, NSSC method. The application of stainless steel in the technique equipments of pulp producing with semichemical method is shown in the following table:

Material in the technique equipments of Pulp producing with semichemical method

Name of equipment and part	Material	Remark
Cooking boiler, auxiliary equipments and pipe system	00Cr17Ni4Mo2 00Cr18Ni10	Confined to continuous boiling
Equipments for Fiber separating, washing and filtrating	00Cr17Ni4Mo2	Drainage bucket, washing and filtrating device of liquid storing bucket , screw feeder
Refining equipment	00Cr17Ni4Mo2	Filtration equipment, centrifugal purifier, pipe, pump, valve

(5) Pulp producing with half wasted paper
The technique medium of pulp producing with waste water is not with very severe corrosion; in order to maintain the whiteness of the paper, 00Cr18Ni10 is commonly used as the equipment structure material; in the working procedure that requires the adding of chemical drugs (zinc hydrosulfite and sodium peroxide, sodium hypochlorite), 00Cr17Ni14Mo2 steel has the satisfactory usage effect.

(6) Paper pulp bleaching
Paper pulp bleaching is the last working procedure, which requires chemical drugs. Different paper pulp making processes will require different bleacher with large discrimination. In the pulp producing with sulfate method or sulfite method, the bleaching should be operated when chlorine, alkali, hypochlorite and chlorine dioxide are used, and for the mechanical pulp making and semichemical pulp making, peroxide and hydrosulfite are often used in the bleaching. During the bleaching process, water circulation will be used, which will cause the chloride in technique medium to increase intensely, and adding chemical drugs in the technique process, the technique medium will become severely corrosive. For the purpose to operate smoothly, the anti-corrosion material chosen for the bleaching technique equipments should be regarded the lowest grade as 00Cr17Ni14Mo2，00Cr19Ni13Mo3。00Cr20Ni25Mo4.5Cu，00Cr18Ni20Mo6CuN; high grade material like the super double phase stainless steel and nickel-base anti-corrosion alloy etc. have been widely used; the technician shall choose properly according to the medium’s actual condition. The applications of stainless steel in the bleaching technique process are shown in the table below:

The application of stainless steel in the bleaching technique process

Working procedure	Medium condition	Material	Remark
Chlorination treatment	Wet chlorine	00Cr17Ni14Mo2 00Cr19Ni13Mo3 00Cr20Ni25Mo4.5Cu 00Cr20Ni18Mo6N	Pipe pump, mixer, bleaching tower, scraper, tank, filtration cylinder, filter, bleaching liquid slot, white liquor transporting pipe
Alkalinity abstraction (extraction)	NaOH，PH10，40℃	00Cr19Ni14Mo2 00Cr18Ni10	Pipes around bleaching tower, bleaching tower, pipes for transporting abstracted pulp, scraper, oscillator, washing filter, washing tank, filtrate bucket, drainage slot
Bleaching with pypocholoride	Pypocholoride, PH>8.5，30-45℃	00Cr17Ni14Mo2 00Cr19Ni13Mo3 HastelloyC	Pipe system for transporting paper pulp, mixer, stirrer, filter, filtration slot, canister, filtration web, in-tower scraper
Bleaching with nitrogen dioxide	ClO2，PH4-5	00Cr17Ni14Mo2 00Cr19Ni13Mo3	Mixer, in-tower stirrer, tower top scraper, washing filter, filtration web, drainage slot, white liquor transporting pipes
		2507，UR52N+ 00Cr20Ni18Mo6CuN	Bleaching liquid canister
Peroxide bleaching	H2O2	00Cr17Ni14Mo2	Bleaching tower, pipe, filtration equipment, stirrer
Hydrosulfite bleaching	Zinc bisulfite, sodium bisulfite	00Cr17Ni14Mo2 00Cr19Ni13Mo3	Bleaching tower, pipe, stirrer, filter

The application of stainless steel in paper pulp bleaching process in Japan

Working procedure name	Name of equipment	Material
C procedure（30℃ Cl2）	Bleaching tower, screw propeller, stirrer, pump, washing machine	0Cr17Ni12Mo2
E procedure（NaOH 70℃）	Bleaching tower, stirrer, washing machine	The gaseous phase is 0Cr18Ni9, under conditions that contain Cl-、ClO-、ClO2, use 0Cr17Ni14Mo2
H procedure（NaClO·NaCl，40℃）	Stirrer, impeller, filter, washing machine	0Cr17Ni12Mo2
D procedure（ClO2，75℃）	Mixer	HastelloyC-276Ti
	Washing machine	0Cr17Ni12Mo2 00Cr19Ni13MoTi
H2O2 Bleaching, borol bleaching	Bleaching tower, circulating pump, stirrer, scrubbers	0Cr18Ni9
O2 bleaching（Na2S、Cl- and O2）	Bleaching tower, circulating pump, stirrer, scrubbers	In high concentration bleaching, use 00Cr19Ni13Mo3 or Carpenter20 ,in medium concentration bleaching, use 00Cr19Ni10

2. Paper making.
The production environment of paper making is not so highly corrosive like the technique medium of paper pulp making, but for the purpose of producing clean paper and easy maintenance, stainless steel is widely used in paper making technique process. The actual application situations are shown in the table below:

The application of stainless steel in paper making industry

Name of equipment or part	Material	Remark
Raw material storage tank	00Cr18Ni10	Lining
Pulp making machine Beating machine frame	00Cr18Ni10 00Cr17Ni14Mo2 Co-Cr-W hard alloy 00Cr18Ni10	Used under condition of high temperature water Stirrer Carbon equipment lining
Refining device tank	00Cr18Ni10 00Cr17Ni14Mo2
Beating machine cutter	1Cr17Ni2	Used in combination with 00Cr17Ni14Mo2
Sifting machine in the purifier Liquid slot, sieve plate	00Cr18Ni10 00Cr17Ni14Mo2
Mixing bucket	00Cr18Ni10 00Cr17Ni14Mo2	Lining or whole
Printing oil canister bucket Alum paste bucket	00Cr18Ni10 00Cr17Ni14Mo2
Paper making machine	00Cr18Ni10 00Cr17Ni14Mo2	Tank, guiding rail, side frame plate, bench roller, siphon tank, stream limiter, pipe system
Pumping sandwich rolling	Double phase stainless steel	Anti-corrosion fatigue
Metal web	00Cr18Ni10 00Cr17Ni14Mo2