In the low-carbon economy era, “energy-saving” becomes a vital topic in the paper pulp industry. The paper pulp mill around the word work on the research of related technology and try to reduce energy consumption. How to promote benefits of the paper pulping plants?
CNBM is a leading paper pulp machine manufacturer from China, and we are specialized in paper pulp making machines manufacture. We can offer pulp digester, blow tank, vacuum drum washer, twin roll press, single screw press, etc. We also provide custom paper pulp plants as you need. To further facilitate customers, we will introduce some energy-saving tips for the paper pulping plant, and we hope you can get inspiration based on your own situation.
Pulp cooking process
As we all know, paper pulping can be divided into three types: chemical pulping, mechanical pulping and chemi-mechamical pulping. There is no doubt that chemical pulping has the most wide applications. So, we introduce energy-saving tips for chemical pulping out of necessity.
Cooking auxiliary agent
The cooking auxiliary agent can improve the liquid penetration and make pulp cooking uniform, which increases the pulp yield and reduce energy consumption, reduce the raw material consumption and increase the working efficiency.
- The synergistic is a common cooking auxiliary agent.
- The phosphate can improve the delignification rate, and increase the pulp yield and whiteness of bleached pulp, also protect the viscosity of pulp. It can save 8%-10% energy and increase pulp yield by 4%-6%.
- There is a new-type agent, for example, Chemstone OAE-11, according to the report, it can both apply for hardwood and softwood, prevent the overcook of fine fibers. This agent can reduce the cooking time, increase the pulp yield by 2%-5%, and reduce sieve residue, bleached agent consumption, and sulfide discharge.
The continuous cooking control system
The continuous digester modification can greatly reduce the production loss, operation cost and negative impact on the environment, at the moment, increase the pulp yield and quality. The control system can optimize the pulping process. For example, the computer models produced by the department of energy in the USA have proved that save 1% energy.
Batch cooking digester modification
here are several energy-saving tips for batch cooking, such as indirect heating and cold blow. The indirect heating means that extract cook liquid from the digester, pass through the heat exchanger, and send back to the digester from two different charge inlets. Indirect heating can reduce steam consumption. But the indirect heating needs maintenance cost of the heat exchanger. For the cold blow system, at the last step of pulp cooking, use washing liquid for unbleached pulp to displace with the hot cooking liquid, the heat of waste liquid can be recovered and applied to the cooking of the next step. The cold blow reduces the steam consumption for heating cooking liquid and wood chips. The recovered black liquor can be used to preheat and dip the wood chip, or heat hot white liquid and water. According to the calculation, a pulp mill with a capacity of 30 tons per day, the cold blow system can save two million dollars, but require high investment in equipment.
In the kraft pulp mill, the hot pulp and cooking liquor will produce steam in the digester relief. For batch cooking, the steam is generally stored in the state of hot water. For continuous cooking, the extracted black liquor flow into a tank to do flash evaporation. All these sections mentioned above can recycle the heat to preheat the wood chips, heat water or steam black liquor.
Pulp washing process
A traditional washing process is a group of three or four vacuum drum washer. There is a new type of pulp washing system that uses pressure diffusion or press washing to replace the original process. Based on the report, we can know that the new system has higher washing efficiency and less nee of power consumption, steam consumption, and bleached chemical consumption. Especially the press washing is widely applied to many pulp mills. Common washing equipment includes twin roll press and single screw press.
The steam cycled washer
At present, the average age of American pulp washing equipment is 45 years old. There is an obvious chance to develop a more efficient washing process and washing equipment. The department of energy in the USA has developed a steam cycled washer with backwashing, steam, and high-pressure difference. It can wash pulp at the concentration of 28%-32%， save 70%-75% water compared with traditional pulp washing equipment.
CIO2 heat exchange
Before sending it to the bleaching process, the CIO2 liquid is usually cooled to achieve the largest concentration. But, preheat the CIO2 before entering the mixer can reduce the steam consumption of the bleaching process. How to save energy in this section? Install heat exchanger at the return circuit for CIO2 transportation, and use recycled heat resource to preheat.
Heat recovery of wastewater
The wastewater of the bleaching process contain a lot of heat, it will be a great loss if the pulp mill doesn’t recycle the heat. How to solve this problem? Install a heat exchanger to recycle the heat to heat water.
In conclusion, except for these tips we talked about above, there are many other ways to save energy in the paper pulp production line, such as chemical recovery, waste paper pulping, and so on. Every paper pulp mill can design own solution to the pulp plant. If you have any need for paper pulp plant customization or paper pulp machines, CNBM also welcome your contact!