Requirement : I need to query all the opportunity and make a csv file and send it to one peoplesoft server using a webservice call.

I have written the batch apex. 

global class OpportunityBatch implements Database.Batchable<sObject>{

    //global declaration of variable which contains all Opportunity
    String query;
   
    // global method for query
    global Database.querylocator start(Database.BatchableContext BC){   
   
        query='select id,AccountId,Amount,CloseDate from Opportunity';
        return Database.getQueryLocator(query);     
    }
    //which called by scheduler class to start the execution.
    global void execute(Database.BatchableContext BC, List<Opportunity> scope){
      List<Opportunity> oppListToUpdate = new List<Opportunity>();
     
      string header = 'Record Id, AccountId , Amount, Close Date \n';   
      String finalstr = header ;
      for(Opportunity opp : scope){
          string recordString = opp.Id+','+opp.AccountId+','+opp.Amount+','+opp.closeDate+'\n';
          finalstr = finalstr +recordString;              
      }
      Blob csvBlob = Blob.valueOf(finalstr);
          
    }
    global void finish(Database.BatchableContext info){    
    }
}

I have to write a scheduler class . But I am not getting how to use the csvBlob in the webservise call.
The web service call will be in batch class or in scheduler class. 

thanks in advance.