Since 2010, the market economy has undergone tremendous changes. The development of the pulp and paper industry has been affected as never before. Due to the high cost of raw materials and low selling prices, many enterprises faced with production cuts, production suspensions, and even bankruptcy. Under such a market environment and the new environmental protection requirements, paper pulp mills must seek new methods and strategies in order to survive and develop. In the new situation, in order to obtain market and ultimately turn losses into profits, enterprises must reduce production costs on the premise of improving product quality. Based on the experience of paper pulping equipment manufacture, this paper introduces the optimization of equipment and process in pulp production and finally achieves the goal of reducing production costs.
Cooking process optimization
In the pulp production, the cooking system is the main steam consumption link. The optimization of the cooking process and the cooking equipment is the key to whether the whole pulping production can save steam and reduce the production cost.
Before the transformation, the steam required for pulp cooking is mainly supplied by the thermoelectric boiler. The cooking process mainly relies on the manual shut-off valve, which is mainly subject to adjust the size of the valve. The pulp cooking process is always cooked under high pressure and full pressure. So that the pulp cooking process is uneven, the cooking quality is obviously poor, the cooking process is not complete enough, and the steam consumed is very high. Besides, the blowing process after the cooking is open-type, during the blowing process, the released steam can be completely discharged, and the energy in the waste steam is not well utilized, resulting in high steam consumption and low production cost.
- Using steam from the alkali recovery to supply to the thermoelectric steam main pipeline, and the cooking steam is reversely supplied, thereby greatly reducing the load of the thermoelectric boiler, reducing the amount of the thermoelectric steam, and reducing the cost of the cooking steam;
- Using the pneumatic regulating valve to control the cooking steam flow, the steam flow from small to large, make the cooking more uniform, full and thorough, and the cooking quality is significantly higher;
- The steam released by the blowing process can be used as the heating washing water, after circulating absorption, The hot water temperature can meet the requirements of washing, thereby reducing the steam consumption for washing, and achieving a closed discharge process to reduce environmental pollution;
- After steaming, the steam used for pulping is also from the original 3. 3t reduced to the present 2. 2t.
Washing process and equipment optimization
For pulp washing process and equipment, no matter which way to be adopted, the pulp washing process basically adopt a four-stage washing and backwashing process, mainly make greater improvement and optimization in the screening process and equipment. Use more advanced medium pressure screen and vacuum washer as screening equipment;
- The screening quality is higher;
- The screening process has no need for clean water, only partial evaporation of condensed water was used as supplement and washing, and the filtrate after the screening was completely reused to achieve closed screening;
- High production capacity and low product cost;
- Zero emissions of pulp screening.
In pulp production, the better equipment and advanced processes are the keys to reducing production costs, improving product quality, and ultimately achieving energy savings and emission reductions. The recommended pulp washing equipment includes vacuum drum washer, twin roll press, single screw press, disc filter.
Bleaching process and equipment optimization
The pulp bleaching process mainly uses CEH or CEOH. Bleaching depends on the concentration of the pulp, the quality of the screening and related equipment.
In a long-term exploration and discussion, a lot of experience about the pulp bleaching process has been accumulated:
- Originally, the filtrates produced in each bleaching section are all discharged directly into the street as wastewater or sent to the sewage station for treatment. After modification and application. Most of the filtrate can be used in reverse flow, which not only saves a lot of water but also saves chemicals;
- Increases the washing area of the washer and improves the production capacity and pulp quality.
- In this production process, many companies currently use CEH bleaching, but the quality of bleached pulp after CEH bleaching is not very stable, it is easy to return yellow in the pulp tank, the fiber is relatively hard; and if CEOH bleaching is used, a small amount of liquid oxygen or H2O2 is added to the process., whiteness of bleached pulp will increase by 2 to 3% ISO, the quality of bleached pulp is relatively stable, the fiber structure is soft, and the bleached pulp is not easy to return to yellow, which can meet the quality requirements of papermaking, especially household paper. Therefore, through practice and comparison, the optimized bleaching process is CEOH bleaching.
With the continuous development and reform of the economy, the production processes and equipment of the pulp mills have formed a certain scale and a relatively mature operating system. In the process of development and expansion, various pulping enterprises have achieved a good pulping ability.
- In the storage of raw materials, taking bagasse as an example, the storage method of wet stacking is mainly used, and the sewage treated by the sewage treatment station is used as the spraying water.
- In the selection of pulping and screening production processes and equipment, the more advanced medium-pressure screens and vacuum washers at home and abroad are mainly used as screening equipment, and a more advanced closed screening process is adopted.
- In terms of energy conservation, after upgrading and optimizing the process and equipment, in terms of steam for tons of pulp, the steam for tons of products is also from the pre-reform 3. 3 t fell to 2. 2t, the annual consumption of steam is 110,000 tons(based on the bagasse pulp making).
- After transforming and optimizing the pulp manufacturing process and equipment, the company finally achieved the goal of energy saving and emission reduction.